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SS2 BIOLOGY

Table of Contents

 

 

Theme 1          Organization of Life   

  1. Classification of Plants

Theme 2          The Organism at Work          

  1. Digestive System
  2. Transportation System
  3. Respiratory System
  4. Excretory System

Theme 3          The Organism and Its Environment  

  1. Nutrient Cycling in Nature
  2. Ecological Management: Association, Tolerance, Adaptation, Pollution
  3. Conservation of Natural Resources
  4. Pests and Diseases of Crops

Theme 4          Continuity of Life       

  1. Reproductive Systems in Vertebrates
  2. Reproductive Systems in Plants
  3. Pollination in Plants

 

 

 

 

 

Theme 1    Organization of Life   

Classification of Plants

A crop refers to a plant intentionally cultivated by humans for various beneficial purposes. Crops undergo classification based on three criteria: life cycle, morphology (form and structure of the plant), and utilization.

Classification Based on Life Cycle:

The life cycle of a crop spans from seed planting to crop maturity. Crops are categorized into three groups:

Annual Crops: These crops complete their life cycle within a year, examples include cotton, cowpea, yam, and rice.

Biennial Crops: Completing their life cycle within two years, crops like cassava, pepper, onions, carrot, and ginger fall into this category.

Perennial Crops: These crops take more than two years to complete their life cycle, including banana, orange, cocoa, and coconut.

 

Classification Based on Morphology:

Crops are classified according to their structure (form and shape):

Monocotyledonous Crops: These crops bear seeds with a single seed leaf (cotyledon), possess leaves with parallel veins, and have a fibrous root system. Examples include maize, rice, millet, and oil palm.

Dicotyledonous Crops: Crops in this category have seeds with two cotyledons, leaves with net veins, and a tap root system. Examples include mango, orange, cowpea, and groundnut.

 

Classification Based on Uses:

Crops are also classified based on their intended purpose:

Cereals: Grown for grains or seeds rich in carbohydrates, such as maize, millet, rice, and wheat.

Legumes (Pulses): Grown for protein-rich seeds or grains, including cowpea, groundnut, soya beans, and pigeon peas.

Roots and Tubers: These crops produce underground tubers rich in carbohydrates, like cassava, yam, potato, and carrot.

Vegetables: Grown for leaves, fruits, or roots rich in vitamins and minerals, such as tomato, lettuce, okro, and cabbage.

Spices: Rich in vitamins and minerals, these crops enhance food flavors, including pepper, ginger, garlic, and onions.

Beverage Crops: Used in making beverages, such as cocoa, coffee, tea, and kola nut.

Fruit Crops: Plants bearing edible fruits rich in vitamins and minerals, like oranges, cashew, guava, and watermelon.

Oil Crops: These crops produce edible oil when processed, including cotton seed, coconut, oil palm, groundnut, and shea butter.

Latex Crops: Produce latex used in manufacturing materials like tires, plastics, and foam, as seen in the rubber tree.

Fibre Crops: Produce fibers used for making clothes, ropes, and sacks, examples being cotton, sisal, jute, hemp, and kenaf.

Drug Plants: Grown for medicinal purposes, such as tobacco, neem, and Indian hemp.

Forage Crops: Grown to feed ruminant farm animals, including stylo, cowpea, and guinea grass.

Ornamental Crops: Grown for beautifying the environment, such as hibiscus and morning glory.

 

Classification of Plants into Seed-Bearing and Non-Seed-Bearing

The classification of plants into seed-bearing and non-seed-bearing is a fundamental division in the plant kingdom. Plants are classified into two main groups based on the presence or absence of seeds: seed plants and non-seed plants.

  1. Seed Plants (Spermatophytes)

Seed plants are divided into two main groups: gymnosperms and angiosperms.

Gymnosperms: These are seed plants that produce naked seeds (seeds not enclosed in a fruit). Examples of gymnosperms include conifers (such as pine, spruce, and fir trees), cycads, ginkgo, and gnetophytes.

Angiosperms (Flowering Plants): These are seed plants that produce seeds enclosed within a protective structure called a fruit. Angiosperms are the most diverse group of plants and include a wide variety of flowering plants, from grasses and herbs to trees and shrubs.

  1. Non-Seed Plants

Non-seed plants do not produce seeds for reproduction; instead, they reproduce by other means, such as spores. This group includes three main types:

Bryophytes: These are non-vascular plants that lack true roots, stems, and leaves. Mosses, liverworts, and hornworts are examples of bryophytes. They reproduce through spores.

Pteridophytes: These are vascular plants that produce spores for reproduction. Ferns, horsetails, and clubmosses are examples of pteridophytes. They have true roots, stems, and leaves.

Algae: Some algae, particularly the non-vascular types like green algae, also fall into the category of non-seed plants. Algae reproduce through various means, including spores and simple cell division.

This classification is based on reproductive structures and methods, and it reflects the evolutionary relationships among different plant groups. Seed plants, especially angiosperms, dominate the plant kingdom in terms of diversity and ecological importance. Non-seed plants, while less diverse, play crucial roles in various ecosystems and have unique ecological adaptations.

 

 

 

 

 

Theme 2    The Organism at Work

Digestive System

Digestive System | Hydra, Earthworm, Insects, Bird, Man

Invertebrates

Hydra Feeding

Planaria Digestion

Earthworm Digestion

Insect Digestion (Grasshopper)

 

Vertebrates

Bird Digestion

Rabbit Digestion

 

Feeding In Hydra

Hydra sustains itself by consuming small aquatic organisms, such as crustaceans. Utilizing specialized structures known as nematocysts on its tentacles, it captures prey. The captured food then enters the mouth, where gland cells secrete digestive enzymes into the enteron. This process involves both extracellular and intracellular digestion, with absorbed nutrients distributed throughout the body, while undigested remnants are expelled through the mouth.

 

Digestion In Flatworm [Tapeworm & Planaria]

While tapeworms are parasitic and lack an alimentary canal, relying on the host’s digested food, planaria, as free-living flatworms, feed on small animals. Planaria possess a simple alimentary canal with a single opening, the mouth, located ventrally. During feeding, the planarian’s pharynx extends from the mouth, drawing in food particles, which then travel to the small intestine. Digestion in planaria involves both extracellular and intracellular processes, with the branched intestine facilitating nutrient diffusion and undigested material exiting through the mouth.

 

Digestion In Earthworm

The earthworm’s alimentary canal, a tube with two openings (mouth and anus), comprises various segments:

 

  1. Mouth and buccal cavity for food intake
  2. Muscular pharynx secreting mucus for lubrication
  3. Tubular oesophagus
  4. Crop for temporary food storage
  5. Muscular gizzard for grinding food against small stones
  6. Long straight intestine for extracellular digestion

 

The earthworm employs its prostomium (mouth) to ingest soil, using the pharynx to suck in food. The esophagus transports food to the crop, where it is temporarily stored before entering the gizzard for mechanical breakdown. Extracellular digestion occurs in the intestine, where enzymes chemically break down food, and the absorbed nutrients enter the bloodstream. The earthworm’s digestive system, resembling a tube within a tube, occupies the anterior half of its body.

 

The earthworm plays a vital role in soil fertility by ingesting organic matter from soil, leaving behind castings containing inorganic matter. This feeding process enhances soil structure, allowing for better air and water penetration, and contributes to overall soil fertility, crucial for supporting crops and plants.

 

Insect Digestion

The digestive system of insects is comprised of three main segments:

  1. Foregut [consisting of the mouth, pharynx, esophagus, crop, and gizzard]
  2. Midgut [stomach]
  3. Hindgut [intestine, ileum, colon, rectum, anus]

Insects like grasshoppers primarily consume leaves, utilizing their mouthparts to cut and crush the foliage. Saliva from salivary glands is introduced to soften the leaves, and the resulting chewed food is stored in the crop, where it is further broken down into smaller pieces.

Enzyme-rich secretions from the foregut and midgut are directed into the midgut for digestion and absorption, while the hindgut serves for water absorption. Solid feces pellets are expelled through the anus after the collection of food waste through the malpighian tubules connecting the midgut and hindgut.

 

Bird Digestion

Birds lack teeth but possess a horny beak for feeding, with many species exhibiting adaptations in their feet for this purpose. The avian alimentary canal includes:

 

  1. Oesophagus
  2. Crop
  3. Proventriculus
  4. Gizzard
  5. Small intestine
  6. Caeca
  7. Cloaca

 

Mechanism of Bird Digestion

Birds swallow their food whole, storing it in the crop where it undergoes softening by secretions from the crop wall. From there, it moves to the proventriculus and then to the gizzard, where gastric juice churns and breaks down the food into smaller units. The gizzard’s muscular action, aided by small stones, contributes to the grinding process. Completion of digestion occurs in the small intestine through the action of intestinal and pancreatic juices, with absorption taking place in this segment. Solid waste is excreted through the anus into the cloaca.

 

Man’s Digestive System And Digestion

In the realm of heterotrophic organisms, sustenance is either derived from autotrophic counterparts or acquired through dependence on other heterotrophic organisms.

The process of digestion involves the ingestion of food, followed by its breakdown into simpler, soluble, and diffusible substances through a series of chemical and mechanical processes. Subsequently, the absorbed nutrients are assimilated into body fluids, while undigested remnants are expelled.

 

Mechanisms of Feeding And Digestion

Holozoic animals possess structures essential for acquiring and capturing prey. Those consuming large food particles exhibit specialized body modifications such as claws, teeth, or beaks, while those dealing with smaller food pieces utilize fluid or filter feeding structures. Saprophytes transform their food into a digestible form before ingestion, and parasites employ structures for infiltrating their hosts.

 

Unlike unicellular animals, most holozoic animals possess an alimentary canal with two openings: a mouth at the anterior end and an anus at the posterior end. This canal facilitates the breakdown of food into smaller units, the secretion of digestive enzymes, and the absorption of nutrients and water.

 

A digestive system comprises the alimentary canal and associated glands and organs that produce enzyme-rich secretions crucial for digestion. Mechanical breakdown is carried out by teeth, while digestive enzymes expedite chemical digestion.

 

Human Food Digestion

The process of human food digestion involves a sequence of stages: Ingestion → Digestion → Absorption → Assimilation → Egestion.

Food enters the mouth, where teeth grind it into smaller units, initiating chemical digestion. Saliva, containing the enzyme ptyalin, acts on cooked starch, converting it into complex sugar (maltose). The tongue mixes the food with saliva, forming a bolus that is then swallowed. Peristalsis, the rhythmic contraction and relaxation of the esophagus, propels the bolus into the stomach.

 

Stomach Digestion

In the stomach, the muscular wall vigorously contracts and relaxes, churning the food. Gastric juice, containing enzymes like pepsin and rennin, along with hydrochloric acid, aids in protein digestion. Pepsin breaks down proteins into peptones and polypeptides, while rennin coagulates milk. Food remains in the stomach for about 3-4 hours.

 

Small Intestine Digestion

The duodenum, the initial part of the small intestine, receives pancreatic juice with digestive enzymes, and the liver produces bile stored in the gall bladder. Pancreatic juice contains enzymes like amylase, trypsin, and lipase. The latter part, the ileum, secretes enzymes like maltase, sucrase, lactase, erepsin, and lipase. Digestion concludes in the small intestine, yielding amino acids, fatty acids, glycerol, and glucose.

 

Absorption And Assimilation

The small intestine’s folded and furrowed wall, along with finger-like projections called villi, maximizes surface area for efficient absorption. Nutrients are absorbed through diffusion or active transport, transported through blood and lymphatic vessels, and excess fats are stored in adipose tissues.

 

Filter Feeding And Fluid Feeding

Filter feeding is prevalent in aquatic animals like mosquito larvae and prawns, utilizing sieve-like structures to gather tiny organisms. Fluid feeding involves animals consuming liquid substances, including suckers (e.g., bugs, mosquitoes) and wallowers (e.g., tapeworms), which absorb nutrients directly through their body surface.

Modification And Mechanisms Of Feeding

Feeding mechanisms in animals vary, encompassing absorption (e.g., tapeworm), biting and chewing (e.g., grasshopper), sucking (e.g., mosquitoes), grinding (e.g., humans), and trapping and absorbing (e.g., bladder worm).

 

 

 

 

Transportation System

Transport System | Organisms, Mammals, Animals & Plants

The transport system involves the movement of metabolic materials from the parts of an organism where they are produced to other parts where they are utilized, stored, or eliminated from the body.

 

The necessity for a transport system in all living organisms, including plants and animals, is rooted in several purposes:

  1. Obtaining essential materials such as oxygen, water, and nutrients.
  2. Eliminating metabolic waste like carbon dioxide, urea, and water.
  3. Facilitating the movement of water and mineral salts from the soil, through the roots, to various parts of the plant.
  4. Transferring hormones from their production site to the site of action.
  5. Conveying glucose to various parts of plants.

 

Comparison of Transport in Lower and Higher Organisms:

  1. Substances moved over small distances vs. Substances moved over greater distances:

(a) Lower Organisms: In simpler organisms, substances are typically moved over short distances within the organism.

(b) Higher Organisms: In more complex organisms, substances need to be transported over larger distances throughout the organism’s body.

  1. Transport is by simple diffusion vs. Transport involves diffusion and other means:

(a) Lower Organisms: Transport in simpler organisms relies primarily on simple diffusion, a passive process where substances move from areas of high concentration to low concentration.

(b) Higher Organisms: In more complex organisms, transport involves not only diffusion but also other active means, such as the circulatory system in animals or vascular tissues in plants.

 

  1. Diffusion is sufficient due to a high surface area to volume ratio vs. Efficient transport system needed due to a small surface area to volume ratio:

(a) Lower Organisms: Simple diffusion is adequate in simpler organisms because they often have a high surface area to volume ratio, allowing sufficient exchange of materials through their cell membranes.

(b) Higher Organisms: More complex organisms have a smaller surface area to volume ratio, necessitating the development of efficient transport systems (like blood circulation or vascular systems) to ensure the distribution of materials to all cells.

  1. Cells are not isolated vs. Isolated cells need to be connected:

(a) Lower Organisms: Cells in simpler organisms are not isolated and may be in direct contact with their external environment.

(b) Higher Organisms: Cells in complex organisms are often isolated within tissues and organs, requiring a network of connections (blood vessels, xylem, phloem, etc.) to facilitate communication and material exchange.

  1. Transport materials are small in quantity vs. Transport materials are large in quantity:

(a) Lower Organisms: Smaller quantities of materials are transported in simpler organisms.

(b) Higher Organisms: Larger quantities of materials, such as nutrients, gases, and waste products, need to be transported in more complex organisms to meet the demands of numerous cells and organs.

 

Materials Transported in Animals:

  1. Oxygen:

   (a) Source: Lungs

   (b) Destination: All living cells of the body

  1. Carbon dioxide:

   (a) Source: Body cells

   (b) Destination: Lungs

  1. Urea:

   (a) Source: Body cells

   (b) Destination: Liver

  1. Excess salts:

   (a) Source: Body cells

   (b) Destination: Skin and kidney

  1. Water:

   (a) Source: Body cell

   (b) Destination: Skin, lungs, liver, kidneys, etc.

  1. Amino acid:

   (a) Source: Small intestine

   (b) Destination: Body cells

  1. Vitamins:

   (a) Source: Small intestine

   (b) Destination: Body cells

  1. Sugar:

   Source: Body cells

   Destination: Body cells

  1. Fatty acid and glycerol:

  (a) Source: Small intestine

  (b) Destination: Body cells

  1. Mineral salt:

   (a) Source: Small intestine

   (b) Destination: Body cells

  1. Hormones:

    (a) Source: Endocrine glands

    (b) Destination: Target organs or tissues

  1. Antibodies:

    (a) Source: White blood cells

    (b) Destination: All body parts

 

Materials Transported in Plants:

  1. Manufactured food:

   (a) Source: Leaves

   (b) Destination: All body cells

Explanation: The food manufactured through photosynthesis in the leaves serves as a nutrient source for all the cells in the plant. It is transported from the leaves to various parts of the plant to support growth, energy, and other cellular functions.

  1. Excretory Products (e.g., CO2 and water):

   (a) Source: All living cells

   (b) Destination: Site of excretion (e.g., stomata)

Explanation: Waste products generated by cellular processes, such as carbon dioxide and excess water, need to be removed from the plant. They are transported from all living cells to specific sites of excretion, such as stomata (tiny pores on leaves) through which gases like CO2 are released.

  1. Water (absorbed):

   (a) Source: Soil

   (b) Destination: Leaves and other parts of the plant

Explanation: Water absorbed by the plant’s roots from the soil is crucial for various physiological processes. It is transported from the roots to the leaves and other parts of the plant where it is needed for functions like photosynthesis, maintaining turgor pressure, and supporting overall plant hydration.

 

Transport Medium

Minerals are typically transported through liquid or fluid mediums. In organisms, four major transport media are commonly utilized:

  1. Cytoplasm: Lower unicellular organisms like amoeba, chlamydomonas, and euglena employ cytoplasm for transportation.
  2. Cell sap/Latex: Found in the concentrated solution in the cell vacuole of plants.
  3. Blood: Most animals, especially vertebrates, use blood to convey essential materials such as oxygen and digested food.
  4. Lymph: Present in higher animals, lymph is a fluid containing extra lymphocytes. It returns to the main vein through an opening in the subclavian (left jugular) vein, aiding in the purification of lymph before entering the bloodstream. Lacteal, a lymphatic vessel, transports fatty acids and glycerol, and lymph movement is facilitated by muscular action. Lymph nodes in the neck, groin, and armpit purify lymph before it enters the bloodstream. Unlike the circulatory system, the lymphatic system terminates blindly.

 

Diverse Mechanisms of Transportation in Some Organisms

Unicellular Organisms

Materials are transported through continuous streaming movements. Streaming may occur along the organism’s direction of movement (e.g., Amoeba), back to front, or in a circular motion (e.g., Paramecium).

Multicellular Organisms

Hydra

The movement of the gut wall draws water into the gut, causing digested food and oxygen to circulate. Flagella of flagellated cells also contribute to material circulation in the gut.

Flatworms

The extensive branching gut and large body surface area to volume ratio enable the diffusion of food and oxygen into all body cells. Body wall movement aids in transporting waste products out of the body.

Insects and Mollusks

Both have an open circulatory system where the heart pumps blood into vessels with branches opening into body cavities known as Haemocoels. Blood flows in unidirectional fashion, and blood distribution is poorly controlled.

Transport System in Mammals (Man)

 

The transportation media in humans include blood and lymph.

 

Composition and Structure of Blood

Blood, a fluid tissue, constitutes about 5-6 liters in the body and consists of two major components: blood cells (solid) and plasma (liquid).

 

Blood Cells

There are three types:

(a) Red blood cells (erythrocyte)

(b) White blood cells (leucocytes)

(c) Blood platelets (thrombocytes)

 

(a) Red Blood Cell

  1. Small, round, and disc-like in shape
  2. Has no nucleus.
  3. One cubic liter of blood has about 5.5 million red blood cells.
  4. Has a lifespan of about 120 days.

 

Red blood cells (RBCs) play a crucial role in transporting oxygen from the lungs to the body cells through their pigment, hemoglobin. The distinctive absence of a nucleus allows for a biconcave shape, maximizing the surface area for efficient oxygen exchange. Hemoglobin, contained within these cells, readily binds with oxygen in the lungs, forming oxyhemoglobin. The circulation of these specialized cells ensures the vital delivery of oxygen to tissues throughout the body.

 

(b) White Blood Cell

  1. Irregular (i.e., amoeboid in shape)
  2. Relatively large and colorless (larger than RBC but fewer)
  3. Contains a nucleus – about 5,000-10,000 per pinhead of blood (cubic milliliter of blood)

 

White blood cells (WBCs), characterized by their amoeboid shape and nucleus, are integral to the body’s defense against diseases. Larger and fewer in number than red blood cells, white blood cells actively engage in immune responses. They defend the body by either engulfing and intruding pathogens, such as bacteria and viruses, or by secreting antibodies that neutralize and eliminate harmful invaders. This vital function helps maintain the body’s overall health and well-being by preventing and combating infections.

 

White blood cells are of two types;

  1. Phagocytes- found in lymphatic system which ingest bacteria, viruses and dead cells to prevent diseases in a process called phagocytosis.
  2. Lymphocytes– made in lymph glands and they produce antibodies i.e. chemicals which stick to the surface of germs to kill them.

 

 

(c) Blood Platelets (Thrombocytes)

  1. Small and Disk-shaped:

   Blood platelets, also known as thrombocytes, are small, disk-shaped cell fragments.

  1. Lack of Nucleus:

   Unlike most cells, blood platelets lack a nucleus, contributing to their distinctive structure.

  1. Critical for Clotting:

Platelets play a crucial role in the process of blood clotting (hemostasis). When a blood vessel is injured, platelets adhere to the site and release substances that attract other platelets. This initiates a cascade of events leading to the formation of a blood clot, which helps prevent excessive bleeding.

  1. Temporary Lifespan:

Platelets have a relatively short lifespan, typically surviving for about 8 to 10 days in the bloodstream.

  1. Formation in Bone Marrow:

The bone marrow is the primary site of platelet production. Megakaryocytes, large cells in the bone marrow, fragment into smaller pieces, giving rise to platelets.

  1. Enhance Clot Stability:

Platelets, along with other components of the blood clotting process, contribute to the stability of the clot. They help seal the wound and prevent further bleeding.

  1. Interaction with Fibrin:

Platelets interact with fibrin, a protein formed during the clotting process, to create a mesh-like structure that reinforces the clot and promotes healing.

  1. Response to Vessel Injury:

Platelets are particularly responsive to vessel injury, quickly aggregating at the damaged site to initiate the clotting cascade.

  1. Vital for Hemostasis:

The primary function of platelets is to maintain hemostasis by preventing and controlling bleeding. They are essential for the body’s ability to respond to injuries and ensure the integrity of the circulatory system.

  1. Collaboration with Other Blood Components:

Platelets work in coordination with other blood components, such as clotting factors and red and white blood cells, to orchestrate an effective response to vascular injuries.

Understanding the role of blood platelets is crucial in appreciating the intricate mechanisms that safeguard the body against excessive bleeding and maintain the delicate balance of the circulatory system.

 

Blood Plasma

The liquid component of blood is a pale yellow liquid composed mainly of water (about 90%), along with plasma proteins, antibodies, hormones, enzymes, gases, digested food, salts, and waste products. It transports dissolved substances and blood cells.

 

Lymph

A colorless liquid in the lymphatic system with a composition similar to tissue fluid but containing extra lymphocytes. It aids in body defense by producing white blood cells and absorbs fatty acids and glycerol. Disease-causing microorganisms in the lymph are filtered out in lymph nodes and engulfed by phagocytes.

 

Blood Functions

  1. Hemoglobin facilitates the transport of oxygen.
  2. The liver and muscles produce heat, which is evenly distributed throughout the body for temperature regulation.
  3. Digested nutrients such as glucose, amino acids, fatty acids, and glycerol are transported from the villi to all body cells and tissues for utilization or storage.
  4. Excretory products like CO2, water, and urea are transported from their production sites to excretory organs (skin, lungs, liver, and kidneys) for elimination.
  5. Hormones are conveyed from their production sites to target organs.
  6. Water, constituting 90% of blood content, is transported to various cells for metabolic activities.
  7. White blood cells (WBCs) defend against infections.
  8. Platelets initiate blood clotting in response to injuries.
  9. WBCs produce antibodies to destroy pathogens and their harmful products.

 

Transport System In Higher Plants

In simple unicellular plants, the exchange of materials occurs through a straightforward diffusion process between the plant and its aquatic environment. Consequently, there is no necessity for a complex transport system. However, in higher plants such as ferns and flowering plants, an intricate transport system becomes essential to convey water and mineral salts from the soil to various plant parts and to transport manufactured food from the leaves to other regions for utilization or storage. The plant’s transport system comprises vascular bundles, including xylem and phloem tissues.

 

The xylem is responsible for transporting water with dissolved substances from the soil to different parts of the plant. On the other hand, the phloem tissue facilitates the translocation of manufactured food from the leaves to other plant parts. In the roots and stems of dicotyledonous plants, a layer known as cambium exists between the xylem and phloem tissues. Vascular bundles are thus present in the roots, stems, and leaves of flowering plants.

 

Processes Supporting Transportation in Plants:

  1. Translocation: This process involves the transportation of manufactured food substances through phloem tissue from the site of production (usually leaves) to other plant tissues where they are utilized or stored.
  2. Transpiration: This refers to the removal of excess water from plants into the atmosphere in the form of water vapor. Water loss can occur through stomata (in leaves), lenticels (in stems), or the cuticle of the leaf surface. The rate of transpiration is measured using instruments.

 

Factors Affecting the Rate of Transpiration:

(a) Size of Stomatal Pores: Flaccidity of guard cells prevents transpiration by closing stomatal pores, while turgidity allows transpiration by opening them.

(b) Humidity: Higher humidity slows down the rate of transpiration.

(c) Temperature: Increased temperature leads to an increase in transpiration.

(d) Light: High light intensity increases photosynthetic rate, leading to higher temperatures and, consequently, an elevated rate of transpiration.

(e) Wind: Higher wind speed results in a higher rate of transpiration.

(f) Soil Water: Increased soil water levels lead to higher absorption rates, resulting in an elevated rate of transpiration.

 

Importance of Transpiration to Plants:

  1. Facilitates the absorption of water and mineral salts from the soil.
  2. Aids in the movement of soil water.
  3. Cools the plant through water evaporation.

 

Water transport in xylem tissue is influenced by root pressure, suction pressure, capillary action, and transpiration pulls.

 

 

 

 

Respiratory System

Definition And Phases Of Respiration

Respiration is a complex biological process involving the intake of oxygen, its distribution within the organism, exchange at the cellular level, and the subsequent release of energy in the form of ATP, water, and carbon dioxide. This biochemical activity within cells breaks down glucose through enzyme-controlled reactions to generate energy for daily cellular functions.

The distinct phases of respiration include:

  1. External Respiration (Breathing):

This phase encompasses the inhalation of oxygen into respiratory organs (such as lungs or gills) and the exhalation of carbon dioxide and water vapor.

  1. Internal (Tissue) Respiration:

This phase involves the oxidation of food substances within cells, leading to the release of energy, carbon dioxide, and water. Oxygen acquired during the breathing process facilitates this internal respiration, as represented by the equation: C6H12O6 + 6O2 → 6H2O + 6CO2 + Energy (ATP).

 

Conditions Necessary For Respiration

For efficient gas exchange to occur, certain conditions must be met:

  1. Respiratory Medium:

This refers to the environment from which the organism acquires oxygen, such as air or water.

  1. Respiratory Organ:

The organ possessed by the organism to extract oxygen from the environment and expel carbon dioxide and water vapor, e.g., lungs in mammals or gills in fishes.

  1. Transport Medium:

A medium (e.g., blood in mammals) is required to transport dissolved oxygen to various cells, picking up carbon dioxide and other waste products for elimination.

  1. Ventilation:

The movement of air over the respiratory surface ensures the replacement of used oxygen and the elimination of waste products. Human breathing is an example of a ventilation mechanism.

  1. Respiratory Surface:

This is the physical surface where gaseous exchange occurs, such as alveoli in mammals or the cell membrane in amoebas.

 

Characteristics of Respiratory Surface

All respiratory surfaces, whether in plants or animals, must exhibit the following characteristics:

  1. Moisture:

   The respiratory surface must be moistened to allow gases to diffuse through them in solution.

  1. Permeability:

   It must be permeable to enable the passage of gases in and out.

  1. Thin-Walled:

   A thin-walled structure facilitates easier and faster diffusion.

  1. Adequate Supply of Transport Medium:

   There must be a sufficient supply of a transport medium (e.g., blood) to aid in the exchange of gases.

  1. Large Surface Area:

   The surface must be large enough to facilitate the easy diffusion of gases.

  1. Highly Vascularized:

   The respiratory surface must be highly vascularized, featuring numerous capillaries or a similar network to facilitate the exchange of gases.

 

Types of Respiratory System

The respiratory systems among different organisms vary based on factors such as type, complexity, size, and habitat. The table below illustrates various organisms along with their associated respiratory structures:

 

The respiratory structures among various organisms exhibit remarkable diversity, adapting to their specific needs and environmental conditions. The following is an expanded explanation of the respiratory structures associated with each organism:

  1. Unicellular organism (e.g., Amoeba, Paramecium):

These single-celled organisms rely on their entire body surface as their respiratory structure. The body surface, acting as a membrane, facilitates the exchange of gases through simple diffusion processes.

  1. Hydra, worm, tapeworm:

Organisms such as Hydra, worms, and tapeworms utilize the cell membrane for respiration. The cell membrane, being the outer boundary of these multicellular organisms, serves as the primary site for gas exchange.

  1. Earthworm:

Earthworms exhibit respiration through their wet skin or body surface. The skin’s moisture allows for efficient gas exchange, and this process is vital for their survival in terrestrial environments.

  1. Fish (e.g., Tilapia):

Fish employ gills as their respiratory structures. Gills consist of filaments where gaseous exchange occurs, ensuring the extraction of oxygen from water and the elimination of carbon dioxide.

  1. Arthropod (e.g., insects):

Insects utilize a tracheal system for respiration. Air enters through spiracles and travels through a network of tracheal tubes, ensuring oxygen delivery to every part of the body.

  1. Arachnids (e.g., spiders):

Arachnids, such as spiders, rely on book lungs for respiration. These book lungs provide a surface for gas exchange, allowing the uptake of oxygen and the release of carbon dioxide.

  1. Tadpoles:

Tadpoles, the larval stage of amphibians, use gills as their primary respiratory structures. These gills extract oxygen from water, facilitating the tadpoles’ survival in aquatic environments.

  1. Reptiles (e.g., lizards):

Reptiles, including lizards, primarily respire through lungs. Lungs provide a complex and efficient structure for the exchange of gases, supporting their adaptation to terrestrial habitats.

 

  1. Amphibians (e.g., toads):

Amphibians exhibit a combination of respiratory structures, including the mouth, skin, and lungs. This versatility allows them to respire through various means, depending on their environmental conditions.

  1. Mammals:

Mammals predominantly rely on lungs as their respiratory structures. Lungs provide a highly specialized and efficient system for the exchange of oxygen and carbon dioxide, crucial for sustaining mammalian life.

  1. Flowering plant:

Flowering plants utilize stomata and lenticels for gas exchange. Stomata, located on the surface of leaves and stems, allow for the intake of carbon dioxide and the release of oxygen during photosynthesis. Lenticels, found in woody tissues, also contribute to gas exchange in plants. This intricate system supports the plant’s metabolic processes and growth.

 

Mechanism of Respiratory System In Lower Animals

  1. Unicellular Organism:

These organisms, such as Amoeba, rely on their entire body surface for respiration. The cell membrane serves as the respiratory surface, facilitating a simple diffusion process. Oxygen, present in high concentrations in the environment, is absorbed by the organism and diffuses into regions with lower concentration.

  1. Insects:

Insects utilize a tracheal system for respiration. Air enters through spiracles and travels through a branching network of tracheal tubes, reaching every part of the body. Special cells called tracheoles provide a moist interface for gas exchange between atmospheric air and living cells. Oxygen dissolves in the tracheole liquid, diffusing into adjacent cells, while carbon dioxide produced during cellular respiration exits through the tracheal system.

  1. Fish:

Fish employ gills as their respiratory organs. Gill filaments facilitate gaseous exchange, while gill rakers prevent food particles from entering the gill chamber. The fish initiates breathing by drawing water into its mouth, allowing oxygen to diffuse into the gill filaments. Carbon dioxide is expelled as water exits through the operculum.

 

  1. Toad:

(a) Tadpole: The larval toad or frog has external gill flaps that extract oxygen from water through diffusion. Tadpoles can also gulp oxygen from the air as they rise to the water’s surface. As tadpoles mature, gills are absorbed, and other respiratory systems develop.

(b) Adult Toad: Adult toads respire through the skin, mouth, and lungs.

 

Buccal (Mouth) Gaseous Exchange

The toad employs its mouth as a respiratory organ due to the following factors:

  1. Large Surface Area:

   The mouth is expansive, providing a substantial surface area for respiratory functions.

  1. Thin Mucus Membrane:

   A thin mucus membrane facilitates easy diffusion for respiratory processes.

  1. Abundant Blood Capillaries:

   The mouth is well-supplied with blood capillaries, enhancing the efficiency of gaseous exchange.

To initiate breathing, the toad closes its mouth, opens its nostrils, and lowers the floor of the buccal cavity, drawing air through the nostrils into the buccal cavity. Subsequently, the capillaries and the glottis close, initiating gaseous exchange between the inhaled air and the blood. To expel air, the floor of the buccal cavity is raised, increasing air pressure and prompting the nostrils to open, allowing air containing carbon dioxide to flow out.

 

Skin/Cutaneous Respiration In Toad

This occurs due to the large surface area of the toad’s skin, which is kept moist by continuous secretion from mucus glands. With an ample supply of blood capillaries and a thin membrane, simple diffusion of gases takes place through the skin in both terrestrial and aquatic environments.

 

Lungs/Pulmonary Respiration In Toad

Similar to buccal respiration, pulmonary respiration in the toad involves drawing air into the mouth by lowering the floor of the mouth, expanding the throat, and opening the nostrils for air entry. After nostril closure, the air in the mouth is propelled into the lungs by the contraction of the mouth floor.

 

To expel carbon dioxide from the lungs, the floor of the mouth moves down, extracting air from the lungs into the mouth. Finally, the nostrils open, and the upward movement of the mouth floor forces air out of the nostrils, completing the respiratory cycle.

 

Respiratory System of Mammals & Respiration In Plants

Mammalian Respiratory System

The respiratory system in mammals stands out as the most intricate among all respiratory systems, featuring a pair of lungs enclosed within the thoracic cavity and linked to the external environment through a network of branched air tubes.

 

In humans, air can be drawn in through either the mouth or nose, both leading to the pharynx—a brief passage that bifurcates into two directions. One path directs air to the digestive tract, while the other leads to the larynx and the lower airway. The glottis, the entrance to the larynx, is safeguarded by a cartilaginous flap known as the epiglottis, preventing the entry of food into the windpipe. The glottis must remain open for air to reach the larynx.

 

The trachea, or windpipe, divides into two bronchi, featuring cartilaginous rings that prevent collapse under low air pressure. Each bronchus further branches into bronchioles within the lungs, where alveoli, surrounded by blood capillaries, facilitate gaseous exchange. Oxygen follows this pathway into the lungs, while CO2 exits through the same route.

 

Mechanism of Mammalian Respiration

 

Mammalian respiration involves two phases: external and internal respiration.

External Respiration (Breathing):

This phase encompasses the inhalation of oxygen and the exhalation of CO2 and water vapor.

 

Mechanism of inspiration (inhalation) in humans:

  1. Contraction of the intercostal muscles.
  2. Upward and outward movement of the ribs.
  3. Flattening of the diaphragm.
  4. Increased volume of the thoracic cavity.
  5. Resultant air intake from the nostrils to the alveoli.

 

Mechanism of expiration (exhalation) in humans:

  1. Relaxation of the intercostal muscles.
  2. Downward and inward movement of the ribs.
  3. Diaphragm assumes a dome shape.
  4. Decreased thoracic cavity volume.
  5. Air expulsion from the alveoli to the exterior through the nose, carrying waste products like CO2 and water vapor.

 

Air composition in inhaled and exhaled air:

The composition of air undergoes notable changes during the respiratory process, with distinct alterations in the proportions of various components between inhaled and exhaled air. This transformation is encapsulated in the table below:

The inhalation phase initiates the respiratory cycle, where the air taken in is characterized by a relatively higher oxygen concentration at 21%. This oxygen-rich air is crucial for sustaining aerobic cellular respiration, supporting vital physiological processes within the body.

 

During exhalation, the composition of exhaled air undergoes discernible modifications. The oxygen content diminishes to 16%, reflecting the utilization of oxygen by the body’s cells in metabolic processes. Simultaneously, the carbon dioxide concentration experiences a substantial increase from 0.03% to 4%, signifying the metabolic waste generated by cellular activities. Carbon dioxide is transported back to the lungs through the bloodstream and expelled during exhalation.

 

Nitrogen, constituting the majority of both inhaled and exhaled air at 78%, remains relatively constant. Nitrogen serves as a non-reactive component, contributing to the overall composition of the air without undergoing significant alterations during the respiratory cycle.

 

The water vapor content in inhaled air is variable, dependent on the environmental conditions and humidity levels. In contrast, exhaled air is characterized by saturated water vapor, reflecting the moisture added to the air during the respiratory process. This moisture-laden exhaled air plays a role in maintaining the optimal conditions for gaseous exchange within the respiratory system.

 

In summary, the dynamic interplay of oxygen, carbon dioxide, nitrogen, and water vapor in inhaled and exhaled air highlights the intricate and finely regulated processes involved in mammalian respiration. These fluctuations in air composition are essential indicators of the physiological exchanges occurring within the respiratory system to support the metabolic demands of the organism.

 

Cellular (Internal) Respiration

 

Cellular respiration is the process of oxidizing glucose to release energy, and it occurs within the mitochondria, the cellular powerhouse, in all living cells.

In the cell cytoplasm, a single 6-carbon sugar molecule undergoes enzymatic catalysis, breaking down into two 3-carbon pyruvate molecules. This glycolysis process doesn’t require oxygen. Each pyruvic acid is subsequently fully oxidized into carbon dioxide and water within the mitochondria. The breakdown of glucose to pyruvic acid is termed glycolysis, while the series of chemical reactions within the mitochondrion responsible for the final breakdown of food molecules into carbon dioxide, water, and energy—carried out by seven enzymes—is known as the Krebs cycle (citric acid cycle). The majority of ATPs (36 ATP) are generated in the Krebs cycle, resulting in a total of 38 ATP molecules when one glucose molecule undergoes complete oxidation.

 

Respiratory System of Mammals

KREB CYCLE

Aerobic And Anaerobic Respiration

In most cells, aerobic respiration, occurring in the presence of oxygen, is the predominant form of cellular respiration. The maximum amount of ATP (38 ATP) is generated from one glucose molecule through this process.

In certain organisms, energy is obtained by breaking down glucose in the absence of oxygen, known as anaerobic respiration. Only two ATPs are produced in this process. In animals, anaerobic respiration often results in lactic acid instead of pyruvic acid, which is useful in yoghurt production. In plants, alcohol and carbon(IV) oxide are produced.

 

Respiration In Plants

Plants lack specialized respiratory organs. Gases move in and out of plants through stomata and lenticels.

Stomata are tiny pores in the lower epidermis of leaves, each enclosed within two bean-shaped guard cells. They regulate the opening and closing of stomata.

Lenticels are breathing pores or tiny openings found in the bark of older stems. Comprising a loose mass of small, thin-walled cells, lenticels permit easy gas diffusion in and out of the plant.

 

Mechanism of Gaseous Exchange In Plants

Oxygen, carbon dioxide, and water vapor are released through a simple diffusion process in plants. Oxygen enters plants through stomata and lenticels, while CO2 and water vapor diffuse out through the same openings. This is facilitated by the concentration gradient of these gases. Plants primarily take in oxygen at night and release carbon dioxide and water vapor during the day due to photosynthetic activities, with oxygen being a by-product of photosynthesis.

The opening and closing of stomata are regulated by guard cells, with stomata opening when guard cells are turgid and closing when the cells become flaccid.

 

 

 

 

Excretory System

Excretion is the elimination process of metabolic waste products from the bodies of all living organisms. It differs from egestion, which involves expelling solid waste (undigested food substances, i.e., faeces) through the anus. The importance of excretion lies in several factors:

 

  1. To prevent harm caused by any excretory product.
  2. Removal of poisonous excretory products from the body.
  3. Maintaining water balance for homeostasis.
  4. Preventing interference of waste products with normal metabolic activities.

 

Organisms Employ various Excretory Structures and Eliminate Specific Waste Products:

  1. Protozoa use contractile vacuoles to expel CO2, ammonia, and water.
  2. Flatworms rely on flame cells to eliminate CO2, ammonia, and water.
  3. Earthworms employ nephridia to excrete CO2, ammonia, and water.
  4. Crustaceans utilize green glands to eliminate CO2, ammonia, and water.
  5. Insects have Malpighian tubules for excreting CO2, ammonia, and uric acid.
  6. Fish use kidneys to excrete CO2, ammonia, and water.
  7. Amphibians, reptiles, and birds excrete water and salt through their kidneys, with birds also eliminating CO2 and water vapour through lungs.
  8. Mammals employ kidneys, lungs, skin, and liver to excrete CO2, water, and urea.
  9. Flowering plants utilize stomata, lenticels, and leaves to eliminate H2O, CO2, O2, tannins, gum, alkaloids, oil, and latex.

 

Excretory systems vary, with examples including:

  1. Protozoa’s contractile vacuole, expelling water through a temporary break in the cell membrane.
  2. Flatworms’ flame cells, with tubules ending in a duct for waste expulsion.
  3. Earthworms’ nephridia, featuring a nephriodiophore for waste discharge and reabsorption of useful substances.
  4. Insects’ Malpighian tubules, absorbing nitrogenous waste and water, converting it into uric acid and eliminating it as solid crystals.

 

The Types of Excretory Systems:

Kidneys in Fish, Amphibians, Reptiles, and Birds:

These organs play a crucial role in maintaining water and electrolyte balance. Fish, amphibians, reptiles, and birds excrete metabolic waste, mainly in the form of ammonia, through their kidneys. Birds, in addition, eliminate carbon dioxide and water vapor through their lungs.

 

Mammalian Excretory System:

 Mammals possess a complex excretory system involving multiple organs. The kidneys filter blood, removing waste products like urea, excess salts, and water. Lungs eliminate carbon dioxide during respiration, while the skin excretes small amounts of water and salts through sweat. The liver is involved in the breakdown of toxins and metabolic byproducts.

 

Excretion in Flowering Plants:

Plants have specific structures and mechanisms for excretion. Stomata, small pores on leaves, allow the exchange of gases like carbon dioxide and oxygen. Lenticels, found in the bark of woody plants, also aid in gas exchange. Leaves may shed substances like tannins, gum, alkaloids, oils, and latex as part of their excretory processes.

 

Malpighian Tubules in Insects:

These tubules play a crucial role in the insect’s excretory system. Located between the midgut and hindgut, Malpighian tubules absorb nitrogenous waste and water from the insect’s hemocoel. As the waste travels through the tubules, it is converted into uric acid, and much of the water is reabsorbed, resulting in the formation of solid crystals.

 

In summary, excretion is a vital process across the biological spectrum, ensuring the removal of harmful waste products and maintaining internal balance. The diverse adaptations seen in various organisms reflect the evolution of specific excretory mechanisms tailored to their environmental and physiological needs.

 

 

Mammalian Excretory System

In mammals, the excretory system serves the vital function of eliminating various waste products from the body. Mammalian lungs expel water vapor and carbon dioxide (CO2), the liver discharges a bile pigment known as bilirubin, the skin releases water, salt, and urea through sweat, while the kidneys excrete water, mineral salt, and urea. This excretory system is comprised of a pair of kidneys, a ureter, a bladder, a renal artery, and a renal vein.

 

Kidney Structure

The mammalian kidney, a reddish-brown, bean-shaped organ situated at the posterior end of the abdomen, exhibits distinct regions when cut longitudinally: an outer cortex and an inner medulla. Numerous narrow tubules, called urinary tubules or nephrons, traverse these regions and open at the tips of triangular-shaped masses known as pyramids. These pyramids, in turn, lead to a funnel-shaped cavity called the pelvis, which continues as the ureter—a lengthy, narrow tube connecting the kidney to the urinary bladder. The kidney is richly supplied with tiny capillaries, branches of the renal artery and vein.

 

Kidney Functions

The kidney performs three major functions:

  1. Osmoregulation: This process ensures the balance between water and salt in the body fluid. The kidney extracts or removes substances from the blood to maintain normal osmotic balance when the concentration of blood is higher or lower than that of the cell content.

 

  1. Maintenance of Acid-Base Balance: The kidney excretes excess acids or bases to regulate the body’s acid-base balance. If the concentration of bases is higher than that of acids, more salt is excreted in the urine to maintain equilibrium.

 

  1. Excretion: The kidney eliminates metabolic waste products from the body by forming urine. This process is facilitated by numerous urinary tubules, which serve as the functional units of the kidney.

 

Urinary Tubule Structure (Nephron)

The nephron comprises a Bowman’s capsule, shaped like a cup, which opens into short coiled proximal convoluted tubules. The tubule then extends as a U-shaped loop known as Henle’s loop in the medulla. The loop re-enters the cortex as the distal convoluted tubule, widening as it enters the pelvis. Numerous capillary networks are associated with the nephron. The renal artery, branching within the Bowman’s capsule, forms a capillary knot called the glomerulus. This glomerulus reconnects to create a blood vessel leading out of the capsule, subsequently branching into a capillary network surrounding the urinary tubule before joining the renal vein.

 

Urine Formation

ULTRA-FILTRATION: The renal artery carries blood to the kidney, entering the glomeruli (capillaries) in the Bowman’s capsule. Water, mineral salts, sugar, and other solutes are filtered from the blood into the capsule.

 

SELECTIVE RE-ABSORPTION: The glomerular filtrate travels down the tubules, including the proximal convoluted tubular loop and the loop of Henle, where watery sugar, amino acids, and useful salts are reabsorbed into the blood capillaries through active transport. This process of selectively reabsorbing beneficial materials into the blood is known as selective reabsorption.

 

HORMONAL SECRETION: As the fluid moves through the distal convoluted tubules, additional water is reabsorbed due to the action of antidiuretic hormones (ADH), ultimately forming urine. The urinary tubules discharge their contents into the pelvis, and from there, urine flows through the ureter into the urinary bladder. When full, the bladder contracts, expelling urine from the body through the urethra.

 

Plant Excretion

Plants lack specialized excretory organs, and excretory waste is minimal. Waste elimination occurs through stomata and lenticels. Primary plant waste products include water, eliminated through transpiration and guttation, and carbon dioxide released during respiration at night when photosynthesis is inactive. Additionally, alkaloids like quinine, nicotine, cocaine, and morphine are transformed into harmless substances, stored in various plant parts as valuable commercial products.

 

 

 

 

 

Theme 3    The Organism and Its Environment  

Nutrient Cycling in Nature

Meaning

Nutrient cycling involves the continuous movement of specific elements such as nitrogen, carbon, water, oxygen, and other substances from the environment to various organisms and back to the environment. The route that atoms or elements follow in this process is referred to as a cycle. Notable examples of nutrient cycles include the nitrogen cycle, carbon cycle, water cycle, and decomposition in nature.

 

Carbon Cycle

The carbon cycle represents the utilization of carbon, facilitating the flow of energy through Earth’s ecosystem. This fundamental process initiates when photosynthetic plants absorb carbon dioxide (CO2) from the atmosphere or dissolved in water.

 

Carbon dioxide enters the atmosphere through:

  1. The combustion of organic materials like coal, wood, and petroleum.
  2. Volcanic activity, releasing carbon dioxide.
  3. Respiration by plants and animals.
  4. The death, decay, and decomposition of plants and animals.
  5. The diffusion of carbon dioxide from seas and other bodies of water, which act as reservoirs for carbon dioxide.

 

Carbon’s Significance in Nature

Plants utilize carbon dioxide from the air in the process of photosynthesis to create their food. Carbon serves as the fundamental building block for all organic matter, contributing to the purification of the atmosphere and the regulation of carbon dioxide levels. Additionally, organic matter, rich in carbon, plays a crucial role in replenishing soil nutrients.

 

Maintaining Carbon-Oxygen Balance

Oxygen comprises 21% of the atmospheric gases. Various processes, such as respiration, decay, and combustion, influence oxygen levels. Human activities like deforestation can disrupt this balance, leading to decreased oxygen and increased carbon dioxide levels. While a slight decrease in atmospheric oxygen has minimal impact, a rise in carbon dioxide may contribute to the greenhouse effect, causing the retention of the sun’s radiant energy and warming the Earth’s atmosphere. Thus, it is essential to manage the carbon-oxygen equilibrium in the atmosphere.

 

The Water Cycle

The water cycle involves the continuous movement of water between the earth and the atmosphere through processes like evaporation, transpiration, and precipitation.

 

Natural Water Cycling Process

Solar energy induces water to evaporate from the hydrosphere into the atmosphere. Upon cooling, the water vapor condenses, forming clouds at high altitudes. These clouds then precipitate as rain, returning water to the hydrosphere.

 

Significance of Water for Plants

Water plays a vital role in various aspects for both plants and animals:

  1. Facilitating the absorption of dissolved mineral salts by plants.
  2. Serving as a crucial raw material for photosynthesis.
  3. Acting as a transport medium for plant nutrients.
  4. Maintaining the osmotic content of body tissues.
  5. Constituting the primary component of plant protoplasm.
  6. Being essential for the germination process.

 

Importance of Water for Animals

Water is equally crucial for animals:

  1. Acting as a solvent in the digestion of soluble food substances.
  2. Forming a substantial portion of the blood.
  3. Assisting in the excretion of waste products.
  4. Regulating body temperature.
  5. Providing a natural habitat for aquatic organisms.

 

 

 

Ecological Management: Association, Tolerance, Adaptation, Pollution

Within a community, various biological interactions occur among organisms of different species. These interactions can be categorized into three types: beneficial, neutral, and harmful associations.

 

Types of Associations:

Symbiosis:

Symbiosis refers to a close association between two organisms, where one or both derive benefits from each other. The participants in this mutually advantageous relationship are termed symbionts. Symbiosis can be further classified into two categories: mutualism and commensalism.

 

Mutualism:

Mutualism describes an association between two organisms in which both derive benefits from their interaction.

 

Examples of mutualistic relationships include:

  1. Algae and fungi in lichen.
  2. Protozoa in the intestine of termites.
  3. Nitrogen-fixing bacteria in the root nodules of leguminous plants.
  4. Bacteria in the rumen of ruminants.

 

Commensalism:

Commensalism is a relationship between two different species, where one (commensal) benefits while the other (host) remains unaffected, neither gaining nor losing.

 

Examples of commensalistic relationships include:

  1. Remora fish and sharks.
  2. Oysters and crabs.
  3. Humans and intestinal bacteria.

 

Parasitism:

Parasitism signifies a close relationship between two organisms, where one, identified as the parasite, resides in or on the body of another—the host—drawing advantages from and causing harm to it, resulting in losses for the host. The parasite thrives in this association, while the host typically experiences harm or even death.

 

Examples of Parasitism:

  1. Man and the tapeworm.
  2. Mistletoe and flowering plants.

 

Competition:

Competition involves interactions between two organisms, whether of the same or different species, wherein one surpasses the other to ensure its survival.

Competition often revolves around limited environmental resources, such as food, water, nutrients, gases, light, and space. During competition, one organism gains control over one or more of these resources, enabling its growth and survival, while the other fails to thrive, leading to its elimination.

Intra-specific competition occurs when members of the same species compete, while inter-specific competition involves members of different species vying for resources.

Examples of Competitive Associations:

  1. Flowering plants and grasses: The larger size and numerous branches and leaves of flowering plants enable them to outcompete grasses by depriving them of nutrients, space, and sunlight, ultimately eliminating the grasses.

 

Predation:

Predation is a form of association where one organism, the predator, kills and directly consumes another, known as the prey. The predator, typically larger and stronger than the prey, benefits by obtaining sustenance, while the prey is entirely consumed.

 

Examples of Predation:

  1. The hawk and chicks of domestic fowls.
  2. The leopard and antelope.
  3. The lion and gazelle.

 

Tolerance:

Tolerance represents the capacity of living organisms to endure slight adverse changes in the environment that affect their survival. The distribution of living organisms in diverse terrestrial and aquatic habitats worldwide is significantly influenced by abiotic factors. These factors encompass temperature, rainfall (moisture availability), light intensity, salinity, and edaphic elements. Each of these factors manifests across a spectrum in various habitats.

 

Tolerance Range:

The tolerance range denotes the span between the minimum and maximum thresholds within which organisms can endure specific environmental changes to ensure their survival. Organisms can thrive only within certain minimum and maximum limits for each abiotic factor. The interval between the upper and lower boundaries is termed the tolerance range for the respective factors. For instance, for most animals, the minimum temperature threshold is 0°C, while the maximum limit is 42°C, with fatal consequences beyond this range.

 

Geographic Range:

The geographic range pertains to the regions where a species of organism is exclusively found within the minimum and maximum limits of its tolerance. For example, the geographic range of the tropical rainforest is confined to the equator due to high rainfall and temperatures. In contrast, tropical rainforests are absent at the Northern and Southern poles due to lower rainfall and temperatures.

 

 

 

Conservation of Natural Resources

Meaning:

Conservation refers to the deliberate and controlled utilization of natural resources, aimed at ensuring their sustained availability while preserving the quality and original state of the environment. In simpler terms, it involves safeguarding natural resources from loss, waste, or exploitation through judicious use, with the goal of maintaining their continuity, availability, and preserving their inherent quality.

 

Natural resources can be categorized as either renewable or non-renewable.

(i) Renewable natural resources: These are resources that can be replenished. Examples include rain, animals, plants, water, and food and soil.

(ii) Non-renewable natural resources: These are resources that, once depleted, cannot be replaced or recovered. Examples mainly include mineral resources such as petroleum, coal, tin, copper, etc.

 

Reasons for Conservation:

(i) To prevent the destruction of the natural environment and enable the continued use of resources for human benefit.

(ii) To preserve rare and valuable plant and animal species for future generations, preventing extinction or permanent loss.

(iii) To maintain naturally beautiful landscapes for their aesthetic value.

(iv) To encourage the recycling of scarce mineral resources, such as water.

(v) To prevent the disruption of natural ecosystems, allowing organisms within them to survive.

(vi) Conservation of forests, which provide medicinal materials, ensures their easy availability and continued existence.

(vii) Natural resources, such as wildlife, forests, and minerals, serve as the foundation for research purposes.

 

Natural Resources Requiring Conservation:

Natural resources that warrant conservation efforts include wildlife, water, forests, soil, air, and mineral resources.

 

Conservation Approaches for Natural Resources

Conserving Wildlife

  1. i) Establishing game or forest reserves.
  2. ii) Developing zoological gardens.

iii) Regulating hunting to prevent the extinction of certain animal species.

  1. iv) Prohibiting the killing or poaching of animals in game reserves.
  2. v) Preventing bush burning to avoid wildlife migration or displacement.
  3. vi) Prohibiting deforestation and promoting afforestation or reafforestation.

vii) Raising awareness about the importance of wildlife.

viii) Preventing pollution to safeguard aquatic life.

 

Conserving Forests

  1. i) Implementing selective tree cutting without disrupting the undergrowth.
  2. ii) Promoting reafforestation and tree planting initiatives.

iii) Preventing bushfires or uncontrolled forest fires.

  1. iv) Combating plant pests and diseases.
  2. v) Establishing forest reserves.
  3. vi) Educating the public about the value of forests and the significance of conservation.

 

Conserving Soil

  1. i) Avoiding overgrazing to prevent soil erosion.
  2. ii) Discouraging indiscriminate deforestation to protect the soil from erosion.

iii) Adopting sustainable farming practices, such as crop rotation, to prevent erosion, leaching, waterlogging, or acidity.

  1. iv) Preventing land pollution to preserve essential soil organisms.
  2. v) Avoiding clear cutting that exposes the soil to erosion.
  3. vi) Prohibiting bush burning, which can lead to soil erosion.

 

Conserving Air

  1. i) Regulating effluents from factories or chimneys to prevent air pollution and acid rain.
  2. ii) Controlling emissions from automobiles or thermal plants to safeguard aerial life.

iii) Properly treating and disposing of sewage.

  1. iv) Burning wastes efficiently to prevent air pollution.

 

Conserving Minerals

Mineral resources, being non-renewable, require conservation measures:

  1. i) Enforcing legislation against indiscriminate mining.
  2. ii) Adopting effective and efficient mineral extraction methods to minimize wastage.

iii) Promoting the responsible and efficient use of available mineral resources.

  1. iv) Discouraging over-reliance on a particular mineral to prevent depletion.
  2. v) Implementing proper pricing for mineral resources and their by-products to ensure optimal value.

 

 Significance and Approaches to Natural Resource Conservation

Conservation of natural resources is imperative for the sustenance of life on Earth. Various categories of resources, including wildlife, forests, soil, air, and minerals, play crucial roles in supporting human activities and maintaining ecological balance. Here, we explore the benefits of conserving these resources and outline methods to ensure their sustainable use.

 

Benefits of Wildlife Resources Conservation:

  1. Human Consumption: Wildlife resources provide essential food items such as fish, prawns, and crayfish.
  2. Tourism: Wildlife areas serve as tourist attractions, offering pleasure and relaxation.
  3. Hydro-Electric Power Generation: Dams, like the Kainji dam, utilize wildlife-rich water bodies for electricity production.
  4. Agricultural Support: Some wildlife ecosystems contribute to agricultural processes, such as pollination by bees.

 

Benefits of Forest Resources Conservation:

  1. Food Supply: Forests offer fruits, vegetables, and meat.
  2. Construction Materials: Timber from forests is a key resource for construction purposes.
  3. Medicinal Herbs: Forests house medicinal plants with various health benefits.
  4. Employment: Forests provide jobs for forest guards, lumbermen, and hunters.

 

Benefits of Soil Resources Conservation:

  1. Agricultural Support: Soil is vital for farming and supports the growth of valuable wood.
  2. Infrastructure Base: Buildings are erected on the soil, forming the foundation for human habitation.
  3. Mineral Resources: The soil is a source of various minerals crucial for industrial and economic activities.

 

Benefits of Air Resources Conservation:

  1. Oxygen Supply: Air provides oxygen for respiration by plants and animals.
  2. Carbon Dioxide for Photosynthesis: Plants utilize carbon dioxide from the air for photosynthesis.
  3. Habitat for Organisms: Air serves as the habitat for diverse organisms, enhancing life’s meaning and comfort.

 

Benefits of Mineral Resources Conservation:

  1. Fuel Source: Minerals like coal, petroleum, and natural gas serve as vital energy sources.
  2. Construction Materials: Minerals such as iron, zinc, and aluminum contribute to construction.
  3. Ornamental Use: Precious metals like gold and silver are utilized for ornamental purposes.
  4. Employment and Economic Value: Mineral extraction provides employment and contributes to foreign exchange.

 

Ways of Ensuring Conservation:

  1. Establishment of Agencies: Organizations like the Nigerian Conservation Foundation and Federal Environmental Protection Agency oversee conservation efforts.
  2. Game Reserves and National Parks: Protected areas like Yankari Game Reserve serve to conserve wildlife and provide recreational and scientific benefits.
  3. Conservation Laws: Governments enact laws to regulate activities like tree felling and hunting to prevent resource exploitation.
  4. Conservation Education: Informing the public about the importance of conservation and the consequences of resource depletion is crucial.

 

Problems Associated with Conservation:

  1. Soil Erosion: Natural forces and human activities cause soil erosion.
  2. Pollution: Land, air, and water pollution pose significant threats to conservation efforts.
  3. Natural Disasters: Events like earthquakes and floods can disrupt conservation initiatives.
  4. Overgrazing: Uncontrolled grazing by domestic livestock leads to environmental degradation.
  5. Indiscriminate Hunting and Fishing: Threatens wildlife and aquatic life, respectively.
  6. Bush Burning and Deforestation: Contribute to the loss of wild plants and animals.
  7. Poor Farming Practices: Practices like bush fallowing and continuous cropping deplete soil nutrients.
  8. Oil Spillage: Causes terrestrial and aquatic life loss, impacting ecosystems.

 

 

 

Pests and Diseases of Crops

A pest is an organism that hosts disease organisms or inflicts damage upon other organisms. Pests can be categorized into crop pests, affecting plants, and livestock pests, targeting animals.

Crop pests encompass insects like grasshoppers, mealy bugs, myriads, beetles, birds, and mammals (such as rodents). Livestock pests include ectoparasites like ticks and mites, as well as endoparasites such as liver flukes, roundworms, and tapeworms. Additionally, pests can manifest as plant nuisances, known as weeds, or animal intruders such as insects, birds, rodents, monkeys, humans, or nematodes.

 

Types of Pest

  1. Insect Pests: Arthropods that transmit diseases or cause harm to plants and animals, such as ticks, lice, grasshoppers, and cotton stainers.
  2. Non-Insect Pests: Vertebrates and mollusks causing diseases in plants and animals or destroying crops, including rodents, worms, nematodes, and monkeys.

 

Groups of Insect Crop Pests

  1. Stem Borers: Larvae of certain moths that infest cereal crops like maize, weakening stems and causing breakage.
  2. Fruit and Seed Feeders: Including fruit-piercing moths, fruit flies, cotton strainers, and specific beetles affecting crops like tomato, millet, maize, and okra.
  3. Root Feeders: Insect larvae or adults, such as the yam beetle, residing in the soil and feeding on yam tubers.
  4. Leaf Feeders: Snails, leaf-feeding beetles, caterpillars of various moths and butterflies, grasshoppers, and locusts consuming crop leaves.
  5. Young Shoot Feeders: Insects like aphids and mealybugs piercing and sucking juices from young crop shoots, potentially transmitting diseases like cassava mosaic through white flies.

 

Life Cycle of Selected Pest: Grasshopper (Zonocerus variegates)

History:

  1. Male and female grasshoppers mate, with fertilization occurring internally.
  2. The female digs a hole near plant roots using her ovipositor and lays 40 to 100 eggs in the hole, covering them with a protective material.
  3. After about three days, the eggs hatch into nymphs, resembling wingless, sexually immature adults.
  4. Nymphs molt multiple times, hopping around and feeding on plant shoots.
  5. They migrate to areas with cassava farms, feeding on cassava leaves until reaching the adult stage.

 

LIFE CYCLE OF A GRASSHOPPER

Impact of Grasshopper Infestation on Cassava:

Both nymphs and adults of grasshoppers consume cassava leaves, shoots, and bark, resulting in a significant decrease in cassava yield due to impaired photosynthesis.

 

Control Method:

Apply gammalin 20 through spraying.

Cassava Mealybug and its Consequences:

The female cassava mealybug reproduces through parthenogenesis, laying unfertilized eggs that hatch into wind-borne larvae or those carried with cassava stem cuttings during planting. These larvae undergo three molting stages before reaching adulthood, completing one generation in approximately twenty-two days. Adult mealybugs have a lifespan of about one hundred and forty-five days.

 

Effects of Mealybug Infestation:

Mealybugs extract sap from cassava, causing stunted shoot growth, the development of bunchy tops, and the eventual death and shedding of shoot leaves. Additionally, mealybug infestation hampers photosynthesis.

 

Control Method:

Before planting cassava tubers, immerse the cuttings in a 0.1% ultracide solution for one minute.

 

Life Cycle of Cassava Mealybug:

The life cycle involves various stages, starting from egg laying through parthenogenesis, wind-borne larvae, molting stages, and the emergence of adults.

 

Life History of Bean Weevil and Its Effects:

Bean weevils, after mating, lay fertilized eggs in ripening pods on the farm. The hatched larvae enter bean seeds before harvesting, feeding on cotyledons in storage. Larvae transform into pupae, eventually becoming adults that fly back to the farm to repeat the cycle.

 

Effects of Bean Weevil Infestation:

Larvae feeding on bean seeds reduces their quality and value.

 

Control Method:

Fumigate bean storage with methyl bromide or other fumigants to eliminate weevils.

Cocoa Myriads (Capsid)

These are piercing and sucking insects. They attach the young shoot of cocoa, introducing toxic saliva into the sap which may kill the plant. It can also introduce viral diseases into the plant.

 

Effects

Cocoa myriads cause die back disease which reduces the growth of cocoa plant. Fruit yield is reduced.

 

Control

Spray the cocoa farm with kokotine or gammalin 20

Yam Beetle (Heteroligusmeles)

 

Life History

The mating of the female and the male yam beetles takes place between November and December in riverine areas and fertilized eggs are laid. Between December and February, eggs hatch into larvae that feed on the decayed organic substances. The larvae melt thrice before developing into pupae. In March, the pupae develop into adults after moulting.

The adults then fly to areas where yams are planted between April and June. They dig into the soil to search for yam tubers. When they eventually come in contact with tubers, they feed on them and seriously damage the tubers. Between October and November, the adult yam beetles undergo breeding migration to the riverine areas again for mating.

 

Effects

Adult beetles feed on yam tubers causing serious damage to the tubers and render the tubers valueless. If the tubers are attacked at early stage, the yield becomes poor.

 

Control

Dust yam or yam sets with Aldrin before planting.

 

This is a summary of various pests that affect crops, their effects on the crops, and recommended methods for controlling them. Here’s a breakdown:

 

  1. Grasshopper:

   Effects: Nymphs and adults feed on leaves and shoots, reducing crop yield.

   Control: Spray with gammalin 20.

  1. Yam Beetle:

   Effects: Adults feed on yam tubers, making them valueless or causing poor yield.

   Control: Dust yam or yam sets with aldrin before planting.

  1. Cocoa Myriads (Capsids):

Effects: Piercing and sucking insects that attack young cocoa shoots, introducing toxic saliva and viral diseases, leading to plant death, reduced growth, and fruit yield.

Control: Spray cocoa farm with kokotine or gammalin 20.

  1. Mealy Bug:

Effects: Sucks sap of cassava, causing bunchy tops in shoots, with leaves dying and dropping, resulting in low root tubers.

Control: Dig cassava cuttings in 0.1% rogor before planting.

  1. Beans Weevils:

  Effects: Larvae feed on bean seeds, boring holes and reducing grain quantity and quality.

  Control: Fumigate the store with insecticides and practice early harvesting.

  1. Cotton Strainers:

   Effects: Feed on cotton seeds, staining lint.

   Control: Spray suitable insecticides.

  1. Mammals (Monkeys, Grass Cutter, Squirrel):

  Effects: Destroy tubers, fruits, and shoots of crops by feeding on them.

  Control: Trapping, shooting, and clearing hideouts by proper weeding.

  1. Birds:

   Effects: Feed on grains, plantains, and other crops.

   Control: Chasing away.

 

The table provides information on the pests, the damage they cause, and suggested control measures for each pest. These measures include the application of specific pesticides, dusting with chemicals, fumigation, trapping, shooting, and other relevant actions to mitigate the impact of the pests on crop yields.

 

Pests and Parasites of Livestock and Their Effects

A parasite is an organism living in or on another organism called host having a harmful effect on the host as a result of the association.  Parasite which lives inside its host is called endoparasite e.g. tapeworm, roundworm, liver fluke.  Parasite which lives on or outside the host is called ectoparasite e.g. ticks, lice and mite.

Examples of Animal Pests, their Effects and Control

Animal pests can have significant effects on agriculture, ecosystems, and human activities. These pests can cause damage to crops, transmit diseases, and disrupt natural habitats. Effective control measures are essential to mitigate the impact of these animal pests. Here are examples of animal pests, their effects, and common control methods:

  1. Rodents:

(a) Effects: Rodents, such as rats and mice, can damage crops, contaminate food supplies, and spread diseases. They are notorious for gnawing on electrical wiring and causing structural damage to buildings.

(b) Control: Control measures include traps, rodenticides, and maintaining proper sanitation to eliminate food sources and hiding places.

 

  1. Insects:

(a) Effects: Insects like aphids, locusts, and beetles can devastate crops by feeding on plant tissues, spreading diseases, and reducing overall yields. Some insects also damage stored grains and crops post-harvest.

(b) Control: Biological control, insecticides, and integrated pest management (IPM) practices are commonly used to manage insect infestations.

 

  1. Birds:

(a) Effects: Birds, such as pigeons and starlings, can damage crops, especially fruits, by pecking and feeding on them. They may also pose a threat to fisheries by preying on fish stocks.

 (b) Control: Bird netting, scare tactics (using visual and auditory deterrents), and repellents are employed to protect crops from bird damage.

 

  1. Nematodes:

(a) Effects: Plant-parasitic nematodes can negatively impact crop roots, leading to stunted growth, wilting, and reduced yields. They are a significant concern in agriculture.

(b) Control: Crop rotation, soil solarization, and the use of nematicides help manage nematode populations.

 

  1. Deer and Rabbits:

(a) Effects: Herbivores like deer and rabbits can consume crops and ornamental plants, leading to economic losses for farmers and gardeners.

(b) Control: Fencing, repellents, and habitat modification are common methods to protect plants from browsing by deer and rabbits.

 

  1. Ticks and Fleas:

(a) Effects: Ticks and fleas are vectors of diseases affecting both animals and humans. They can transmit pathogens such as Lyme disease, typhus, and various feverControl:** Insecticides, acaricides, and preventive measures like regular grooming and maintaining a clean environment help control tick and flea infestations.

 

  1. Termites:

(a)  Effects: Termites are known for damaging wooden structures, including buildings, furniture, and fences.

 (b) Control: Termite baits, liquid termiticides, and physical barriers are used to prevent and control termite infestations.

 

Effective pest control involves a combination of biological, chemical, and cultural methods. Integrated pest management strategies aim to minimize environmental impact while efficiently managing pest populations to protect agriculture and ecosystems. Regular monitoring and adapting control measures based on the specific characteristics of the pest species are crucial for successful pest management.

 

 

 

Theme 4  Continuity of Life   

  1. Reproductive Systems in Vertebrates

 

Male And Female Reproductive Structures

Structures of the Male Reproductive System:

 

  1. Testis:

   (a) Description: Oval-shaped structures are found in scrotal sacs in pairs outside the body to maintain a cooler temperature.

   (b) Functions:

     (1) Production of sperms.

     (2) Production of male sex hormones (testosterone).

     (3) Development of secondary sexual characteristics in males.

 

  1. Seminiferous Tubules:

   (a) Description: Found within the testis, composed of a mass of sperm-producing tubes.

   (b) Function: Site of sperm production.

 

  1. Epididymis:

   (a) Description: A long coiled tube located outside the testis.

   (b) Function: Collects and stores sperm temporarily until maturity.

 

  1. Vas Deferens (Sperm Duct):

   (a) Description: A narrow tube leading from the epididymis to the seminal vesicles.

   (b) Function: Conduction of sperm from the epididymis to the seminal vesicle.

 

  1. Seminal Vesicle:

   (a) Description: A small sac at the back of the vas deferens.

   (b) Functions:

    (1) Stores sperm until ejaculation.

    (2) Secretes part of the seminal fluid.

    (3)  Seminal fluid contains fructose, providing energy for the sperms.

 

  1. Prostate Gland:

   (a) Description: Connected to the urethra through many tubules.

   (b) Function: Secretion of seminal fluid.

 

  1. Cowper’s Gland:

   (a) Description: Located close to the prostate gland.

    (b) Function: Secretes a part of the seminal fluid, raising the acidic pH of the female reproductive medium, which could otherwise be detrimental to sperm survival.

 

  1. Urethra:

   (a) Description: A narrow tube passing through the penis.

   (b) Function: Facilitates the passage of sperm into the vagina of the female animal and also serves as the urinogenital opening, allowing the passage of urine out of the body.

 

  1. Penis:

   (a) Description: Contains tissues that make it turgid (erect when filled) with blood.

   (b) Function: Helps to introduce sperm into the vagina of the female animal and facilitates the passage of urine.

 

The male reproductive system is a complex network of organs with specific structures and functions, all working together to produce, store, and deliver sperm for sexual reproduction.

Structures And Functions of The Female Reproductive System

  1. Ovaries:

   (a) Description: Found on each side of the vertebral column (two in every woman).

   (b) Functions:

     (1) Produce eggs (ova).

     (2) Produce female sex hormones (oestrogen and progesterone).

     (3) Development of secondary sexual characteristics in females.

 

  1. Oviduct (Fallopian Tube):

(a) Description: A long narrow tube with a funnel opening that receives eggs released by the ovary, linking the ovary and uterus.

(b) Functions:

  (1)  Fertilization takes place in the oviduct.

  (2)  Allows the passage of eggs from the ovary to the uterus.

 

  1. Uterus:

  (a) Description: A muscular organ that serves as a cavity for the development of the zygote into a baby.

   (b) Function:

    Site of embryo development from implantation until birth.

 

  1. Vagina:

   (a) Description: A muscular tube leading from the uterus to the outside of the body.

   (b) Functions:

     (1)  Receives sperm from the penis during intercourse.

     (2)  Allows the passage of the fetus during birth.

 

  1. Cervix:

 (a) Description: A ring of muscles with a tiny opening that closes the lower end of the uterus where it joins the vagina.

 (b) Function: Controls the opening and closing of the vagina, especially during birth.

 

  1. Vulva:

   (a) Description: Refers to all external parts of the female reproductive organ.

    (b) Functions:

     (1) Allows the passage of the penis into the vagina during intercourse.

     (2) Permits the passage of the fetus during birth.

 

  1. Clitoris:

   (a) Description: A small, sensitive organ corresponding to the male penis. It is erectile and becomes stiff when stimulated due to blood inflow.

    (b) Function: Helps to stimulate the female during sexual intercourse, leading to orgasm.

 

Evaluation

 

Structural Differences between Male and Female Reproductive Systems:

  1. The presence of testes in males and ovaries in females.
  2. Differences in external genitalia (penis and scrotum in males, vulva in females).
  3. Presence of a uterus in females for embryo development.
  4. The structure of gametes (sperm in males, ovum in females).
  5. The role of hormones (testosterone in males, estrogen and progesterone in females).

 

Description of Organs in the Female Reproductive System:

  1. Ovaries: Produce eggs and female sex hormones.
  2. Oviduct (Fallopian Tube): Site of fertilization and passage for eggs from ovary to uterus.
  3. Uterus: Muscular organ for embryo development.
  4. Vagina: Muscular tube for sperm reception and childbirth.
  5. Cervix: Ring of muscles controlling the vagina’s opening.
  6. Vulva: External parts facilitating intercourse and childbirth.
  7. Clitoris: Sensitive organ contributing to sexual stimulation.

 

Structure of Mammalian Gametes:

Male Gamete (Sperm):

  1. Produced in the testes through spermatogenesis.
  2. Microscopic and unicellular.
  3. Comprises parts like acrosome, middle piece, flagellum, and nucleus.
  4. Nucleus contains genetic material (DNA) for fertilization.

 

Female Gamete (Ovum):

  1. Produced in the ovaries through oogenesis.
  2. Larger than sperm, about 0.1mm in diameter.
  3. Comprises cytoplasm, a central nucleus with chromosomes, granules and yolk droplets for nourishment, plasma membrane, outer vitelline membrane, and jelly coat of glycoprotein.
  4. Nucleus contains chromosomes responsible for transmitting traits from parents to offspring.

 

 

Structure of Male and Female Reproductive Organs of Fish and Reptiles:

Fish and reptiles exhibit diverse reproductive strategies, but there are commonalities in their reproductive organs. In general, both male and female individuals have gonads responsible for producing gametes (sperm and eggs, respectively). Here’s an overview:

 

Male Reproductive Organs:

Testes: These are the primary male reproductive organs responsible for producing sperm. In fish, testes can be paired or unpaired structures.

Ducts: Sperm travel from the testes through ducts like vasa deferentia before being released during reproduction.

 

Female Reproductive Organs:

Ovaries: These are the female gonads responsible for producing eggs (ova).

Oviducts: Eggs move from the ovaries through oviducts, where fertilization may occur. In some fish, eggs are released into the water, while in others, fertilization occurs internally.

 

Parts and Functions of Male and Female Reproductive Organs of Fish and Reptiles:

 

Male Reproductive Organs:

  1. Testes: Produce sperm through spermatogenesis.
  2. Vasa Deferentia: Transport sperm from the testes to the outside.
  3. Accessory Glands: Some species have accessory glands that contribute fluids to the sperm, aiding in fertility.

 

Female Reproductive Organs:

  1. Ovaries: Produce eggs through oogenesis.
  2. Oviducts: Transport eggs from the ovaries to the external environment.
  3. Accessory Glands: Some species have glands contributing substances to the eggs or surrounding environment.

 

Structure of Male and Female Gametes:

Male Gametes (Sperm):

  1. Head: Contains the nucleus with genetic material.
  2. Midpiece: Packed with mitochondria to provide energy for movement.
  3. Tail: Propels the sperm towards the egg.

 

Female Gametes (Eggs/Ova):

  1. Nucleus: Contains genetic material.
  2. Cytoplasm: Provides nutrients for the developing embryo.
  3. Zona Pellucida: Protective layer surrounding the egg.

 

Differences Between Male and Female Reproductive Organs of Fish and Reptiles:

  1. Gamete Production: Males produce sperm, while females produce eggs.
  2. Internal vs. External Fertilization: In some fish, fertilization occurs externally, while in many reptiles, it is internal.
  3. Copulatory Organs: Some male reptiles have specialized copulatory organs for internal fertilization.
  4. Egg Development: Fish may lay eggs that develop externally, while reptiles may have internal egg development with various reproductive strategies (oviparous, viviparous, or ovoviviparous).

 

Remember that variations exist across different species of fish and reptiles, and the details can differ based on the specific characteristics of each group.

 

 

Reproductive Systems in Plants

Flower Structure:

Floral Part (Whorls):

  1. Calyx (Sepals): The outermost part, usually small and green, protects the flower in the bud.
  2. Corolla (Petals): Located inside the sepals, the attractive part of the flower, coloured and scented to attract pollinators.
  3. Androecium (Stamens): Male reproductive organs, composed of stamens with filaments and anthers. Anthers produce pollen grains.
  4. Gynoecium (Carpels): Female reproductive organ, innermost floral part, composed of carpels. A carpel includes the ovary, style, and stigma.

 

Flower Stalk (Pedicel):

Supports the floral part and connects the flower to the stem.

 

Parts of a Typical Flower:

The Calyx:

(a) Composed of sepals, a protective outer layer in the bud.

(b)  Sepals can be separated (polysepalous) or joined to form a cup (gamosepalous).

(c)  Epicalyx may be present in some flowers.

 

The Corolla:

(a) Composed of petals, the attractive and often coloured part of the flower.

(b) Petals can be separated (polypetalous) or joined to form a tube (gamopetalous).

 

The Androecium:

(a) Male reproductive organs, composed of stamens with filaments and anthers.

(b) The anther produces pollen grains, which contain the male gametes.

 

The Gynoecium:

  1. Female reproductive organ, composed of carpels.
  2. Carpels may be separate (monocarpous) or fused (polycarpous).
  3. A pistil or carpel includes ovary, style, and stigma.
  4. The ovary contains ovules, which produce the female gametes.
  5. After fertilization, the ovary develops into fruit, and the ovule develops into a seed.

 

Types of Ovary:

  1. Superior Ovary: Above other floral parts, hypogynous flower (e.g., hibiscus).
  2. Inferior Ovary: Below other floral parts, epigynous flower (e.g., sunflower).
  3. Half Inferior Ovary: At the same level as other floral parts, perigynous ovary (e.g., rose).

 

Types of Flower:

  1. Flowers differ in:
  2. Number of floral parts
  3. Color of petals
  4. Size and shape
  5. Symmetry (radial or irregular)
  6. Completeness (complete or perfect, incomplete or imperfect)
  7. Position of the ovary (hypogynous, epigynous, or perigynous)
  8. Occurrence (solitary or in groups, axillary or terminal)

 

Sexes in Plants:

  1. Most flowers are bisexual (both stamens and carpels), while some are unisexual.
  2. A plant can be monoecious (both male and female flowers on the same plant) or dioecious (male and female flowers on different plants).

 

Placentation:

  1. Placentation refers to the arrangement of ovules within the ovary.
  2. Types of placentation include marginal, parietal, free central, axile, and basal.

 

Types of Placentation:

  1. Marginal Placentation: Ovules arranged at the margin of the ovaries (e.g., beans, flamboyant flowers).
  2. Parietal Placentation: Ovules arranged to the side of the ovary or within a single chamber (e.g., pawpaw).
  3. Free Central Placentation: Ovules born on a knob projecting from the base of the ovary (e.g., water lily).
  4. Axile Placentation: Carpels meet at the centre to form the placenta for ovule attachment (e.g., tomatoes).
  5. Basal Placentation: Ovules attached to the base of the ovule (e.g., sunflower).

 

 

Pollination in Plants

Pollination Process:

(a) Definition: The transfer of mature pollen grains from the anther of a flower to the mature stigma of the same or another flower.

(b) Precedes Fertilization: Pollination typically occurs before fertilization.

 

  1. Types of Pollination:

(a) Self-Pollination: Pollen transfer from the anther to the stigma of the same flower or another flower of the same plant. Involves only one parent plant.

(b) Cross-Pollination: Pollen transfer from the anther of one flower to the stigma of a flower on another plant of the same or closely related species. Involves two parent plants.

 

Advantages and Disadvantages of Self-Pollination:

   Advantages:

  1. Effective pollination in bisexual flowers.
  2. Avoids wastage of pollen grains.

   Disadvantages:

  1. Weak offspring due to continuous self-pollination.
  2. Offspring are less adaptive to the environment.

 

Advantages and Disadvantages of Cross Pollination:

   Advantages:

  1. Production of healthier offspring.
  2. Production of viable seeds.
  3. Offspring are more adapted to the environment.
  4. Formation of new varieties with good characteristics.

  Disadvantages:

  1. Depends on external agents (wind, insects).
  2. Wastage of pollen grains, especially in wind pollination.

 

Features of Self-Pollinated Flowers:

   (a) Homogamy and cleistogamy are features favoring self-pollination.

 

  1. Features of Cross-Pollinated Flowers:

(a) Dioecious flowers, dichogamy (protandry and protogyny), brightly coloured petals, sweet smell, unisexual flowers, self-incompatibility, and the position of anthers and stigmas.

 

  1. Agents of Pollination (Pollinators):

   (a) Insects, birds, snails, bats, and humans, as well as physical factors like wind and water.

   (a)  Major agents are insects and wind.

 

  1. Characteristics of Insect-Pollinated Flowers (Entomophilous):

(a) Large conspicuous petals and sepals, bright colouration, scent, presence of nectar, rough, sticky and relatively few pollen grains, and a flat, sticky stigma.

 

  1. Characteristics of Wind-Pollinated Flowers (Anemophilous):

(a) Small inconspicuous petals and sepals, dull-coloured flowers, absence of scent, absence of nectar, a large quantity of pollen grains, small, light, sticky pollen grains, and an elongated sticky stigma with a large surface area.

 

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