Characteristics Of Living Things

Classification involves grouping living things based on their structural, genetic, and cellular organization, a practice known as taxonomy. The current system of classification, introduced by the Swedish naturalist Carl Von Linne (1707-1778), categorizes living things into various hierarchical levels.   In this system, living things are initially grouped into a broad category called a kingdom. […]

Classification involves grouping living things based on their structural, genetic, and cellular organization, a practice known as taxonomy. The current system of classification, introduced by the Swedish naturalist Carl Von Linne (1707-1778), categorizes living things into various hierarchical levels.

 

In this system, living things are initially grouped into a broad category called a kingdom. The kingdom is then divided into smaller units known as phyla (or division, in the case of plants). Phyla are further subdivided into classes, classes into orders, orders into families, families into genera, and genera into species. A species is defined as a population of related organisms capable of interbreeding to produce fertile offspring.

 

The modern classification system, based on physiology, biochemistry, and embryology, categorizes living things into five kingdoms: Monera, Protoctista, Fungi, Plantae, and Animalia.

 

Kingdom Monera (Characteristics)

  1. Lack organized DNA, with scattered Deoxyribonucleic acid (DNA) in the cytoplasm (prokaryotes).
  2. Absence of mitochondrion in the cytoplasm.
  3. Cell walls made of protein and fatty materials.
  4. Microscopic single-celled organisms, some motile and some non-motile.
  5. Feed both autotrophically and heterotrophically.
  6. Reproduction occurs only through asexual means.

 

Kingdom Protoctista (Characteristics)

  1. Well-organized DNA in the nucleus (eukaryotes).
  2. Single-celled organisms.
  3. Some motile and some non-motile.
  4. Inhabit water, damp soil, leaf litter, and other moist terrestrial habitats.
  5. Use mitochondrion for cellular respiration.
  6. Form cysts to survive adverse conditions.
  7. Reproduce both sexually and asexually (e.g., Amoeba, Euglena, Chlamydomonas, Plasmodium).

 

Kingdom Fungi (Characteristics)

  1. Heterotrophic feeding (lacks chlorophyll and cannot photosynthesize).
  2. Simple multicellular organisms with non-green bodies.
  3. Lack true roots, stems, and leaves.
  4. Composed of thread-like hyphae forming mycelium.
  5. Reproduction through spores.
  6. Carbohydrate storage as glycogen.
  7. Cell walls made of chitin (not cellulose like plants).

Examples: Mucor, Rhizopus, Mushroom, Slime mould.

 

Kingdom Plantae (Characteristics)

  1. Multicellular and non-motile organisms.
  2. Cells bounded by rigid cellulose cell walls.
  3. Contain chlorophyll for photosynthesis.
  4. Store carbohydrates as starch or sucrose.

 

Classification of Kingdom Plantae Based on Botanical Classification

Thallophyta (Algae)

  1. Simple microscopic plants.
  2. Lack true roots, stems, and leaves.
  3. Found in aquatic habitats.
  4. Autotrophic (synthesize their own food).
  5. Reproduce both asexually and sexually.
  6. Cell walls contain cellulose and various pigments.

 

Bryophyte (Moss and Liverwort)

  1. Non-vascular multicellular plants.
  2. Terrestrial, growing in moist environments.
  3. Differentiated into stem-like and leaf-like structures.
  4. Lack true roots, stems, and leaves.
  5. Asexual reproduction via spores; sexual reproduction in water.
  6. Exhibit alternation of generation.

 

Division Pteridophyta (Ferns)

  1. True roots, stems, and leaves.
  2. Well-developed vascular bundles.
  3. Reproduction by spores and dependent on water for sexual reproduction.
  4. Terrestrial and some aquatic species.
  5. Exhibit alternation of generation.

 

Spermatophyta (Seed-Bearing Plants)

  1. Well-developed vascular bundles.
  2. Adapted to terrestrial habitats.
  3. Divided into Gymnospermatophyta (Coniferophyta) and Angiospermatophyta.

 

Gymnospermatophyta (Coniferophyta)

  1. Large plants with true roots, stems, and leaves.
  2. Needle-like green leaves.
  3. Naked seeds borne in cones.

 

Angiospermatophyta

  1. Possess true flowers for sexual reproduction.
  2. Well-developed roots, stems, and leaves.
  3. Seeds and fruits produced after fertilization, enclosed within the ovary.
  4. Terrestrial and some aquatic species.

 

Subdivided into two classes:

Monocotyledoneae (Monocot)

  1. Leaves with parallel veins.
  2. Dull-colored flowers.
  3. Embryo with one cotyledon.

 

Dicotyledoneae (Dicot)

  1. Leaves with network veins.
  2. Brightly colored flowers.
  3. Embryo with two cotyledons.

Examples: Maize, palm tree, grasses (Monocot); Mango, Orange (Dicot).

 

Agricultural classification involves categorizing plants based on the purpose for which they are cultivated. The main categories include:

Cereals or Grain Crops:

  1. Cultivated for their grain with high starch content.
  2. Examples: maize, guinea corn, millet, wheat, ryes, barley, and oats.

 

Leguminous Plants or Pods:

  1. Important plants with high protein content, serve as a source of nitrate in the soil.
  2. Examples: groundnut, beans, melon, flamboyant, crotalaria, etc.

 

Root Crops:

  1. Tuberous plants specialized for food storage, providing a good source of carbohydrates.
  2. Examples: sweet potatoes, Irish potatoes, yam, cassava, and carrot.

 

Vegetable Crops:

  1. Herbaceous plants that are vital constituents of a diet, serving as sources of vitamins and mineral salts.
  2. Examples: tomatoes, pepper, onions, cabbage, lettuce, okra, and other vegetables.

 

Fruits:

  1. Grown for the production of fruits, rich in vitamin A, C, and minerals, usually consumed in their natural form.
  2. Examples: mangoes, pawpaw, guava, bananas, pineapple, etc.

 

Cash Crops (Economic Crops):

  1. Grown primarily for profit.
  2. Examples: oil-producing plants like oil palm, latex crops like rubber, fiber crops like cotton, and beverage/drug plants like cocoa and spices.

 

Oil Plants:

  1. Produce oil as a food reserve stored in their fruits or seeds.
  2. Examples: palm oil fruit and kernel, melon seed, cottonseed, groundnut, coconut, and shea butter.

 

Fibre Crops:

1.  Grown for their fibers used in making clothing, ropes, sacks, etc.

 

Beverages and Drug Plants:

  1. Produce non-alcoholic beverages (e.g., cocoa, coffee).
  2. Examples of drugs include quinine obtained from the bark of cinchona spp., used as an anti-malaria drug.
  3. Spices: Vegetable plants used to add flavor to modern dishes, such as ginger, cloves, pepper, vanilla, nutmeg.

 

Classification of Plants Based on Life Cycle:

Annuals:

  1. Plants with one growing season, producing seeds in the first year and then dying off.
  2. Examples: maize, guinea corn, wheat, groundnut, beans, etc.

 

Biennials:

  1. Plants that grow for two seasons, with the first year devoted to building up food material and seed production in the second year.
  2. Examples: cabbage, carrot, cocoyam, cassava, etc.

 

Perennials:

  1. Plants that grow for three or more seasons or years.
  2. Examples: shrubs and trees.

 

Relevance of Biology to Agriculture:

Agriculture, defined as the cultivation of crops and rearing of farm animals, is essential for providing human basic needs like food, shelter, clothing, and materials for industrial purposes.

 

Kingdom Animalia (Characteristic Features):

  1. Multicellular organisms.
  2. DNA located in the nucleus enclosed with a nuclear membrane.
  3. Cells have no cell walls.
  4. Nervous systems present except in sponges.
  5. True tissues present except in sponges.
  6. Heterotrophic feeding.
  7. Divided into two major groups: Invertebrata (animals without a backbone) and Vertebrata (animals with a backbone).

 

Classification of Animals Based on Features Like Body Symmetry, Body Design, and Body Cavity:

Body Symmetry:

  1. Radial Symmetry: Body can be cut along its axis anywhere to give two identical halves.
  2. Bilateral Symmetry: Body can be cut along its axis in only one place to give two identical halves.

 

Body Design:

  1. Sac-like Body Design: Animals with a single opening (mouth) leading to the gut cavity.
  2. Tubular Body Design: Animals with double openings like a tube with gut openings at the anterior (mouth) and posterior (anus).

 

Body Cavity:

  1. Acoelomate: Animals without a body cavity.
  2. Pseudocoelomate: Animals with a false body cavity.
  3. Coelomate: Animals with a true body cavity.

 

Members of Phylum Invertebrata:

Porifera (Characteristic Features):

  1. Unicellular aquatic animals, often attached to rocks or shells in colonies.
  2. Lack specialized tissues, organs, or systems.
  3. Radial symmetry.
  4. Single opening leading to an internal cavity.
  5. Examples: sponges.

 

Phylum Cnidaria or Coelenterata (Characteristic Features):

  1. Multicellular organisms, including sea anemones, jellyfish, and corals.
  2. Radial symmetry.
  3. Single body cavity called enteron.
  4. Two distinct body layers (diploblastic): ectoderm and endoderm.
  5. Soft, jelly-like bodies.
  6. Asexual reproduction by budding.
  7. Tentacles and stinging cells (Nematocysts) used for capturing prey.

 

Phylum Platyhelminthes (Flatworms):

  1. Flat, unsegmented bodies.
  2. Bilateral body symmetry.
  3. No body cavity or lumen.
  4. Three layers (triploblastic): ectoderm, mesoderm, and endoderm.
  5. Most are hermaphrodites.
  6. Some are parasites in humans and other animals.

 

Phylum Nematoda (Roundworms):

  1. Round and cylindrical bodies.
  2. Lack a body cavity (pseudo-coelom).
  3. Bilateral body symmetry.
  4. Some hermaphrodites, some reproduce sexually.

 

Phylum Annelida (Earthworms, Leeches, Tubeworms):

  1. True body cavity or coelom.
  2. Metameric segmentation internally and externally.
  3. Aquatic and terrestrial.
  4. Sexual reproduction; many are hermaphrodites.

 

Phylum Mollusca (Squid, Mussel, Snails, Oyster):

  1. Soft, unsegmented bodies.
  2. Tentacles on the head.
  3. Muscular foot adapted for crawling or burrowing.
  4. Body covered by a mantle; some have calcareous shells.
  5. Aquatic and terrestrial.
  6. Oculiferous tentacles for sensitivity.

 

Phylum Arthropoda (Largest Group in Animal Kingdom):

  1. Segmented bodies with a distinct head and complex muscular system.
  2. Divided into classes: Crustacea, Insecta, Arachnida, Myriapoda.
  3. Hard, rigid exoskeleton made of chitin.
  4. Jointed appendages or legs for various functions.
  5. Molting or ecdysis for growth.
  6. Various means of respiration (gills, trachea, lung book, body surface).

 

Phylum Echinodermata (Starfish, Sea Urchins, Sea Cucumbers):

  1. Radial body symmetry.
  2. Mostly marine.
  3. Triploblastic animals.
  4. No brain or eyes.
  5. True feet used for movement.

 

Sub Phylum Vertebrata (Five Classes):

Class Pisces (Fishes):

  1. Bony fish with a bony skeleton or cartilaginous fish with soft bones.
  2. Covered by scales, possess fins for movement.
  3. Gills for gaseous exchange.
  4. Poikilothermic or cold-blooded.
  5. Swim bladder for buoyancy.
  6. Lay eggs externally.

 

Class Amphibia (Amphibians):

  1. Two pairs of limbs, naked or moist glandular skin.
  2. Dual life: can live in both water and on land.
  3. Gaseous exchange with gills in tadpole stage and with lungs, skin, and mouth in adults.
  4. Oviparous with external fertilization.

 

Class Reptilia (Reptiles):

  1. Dry skin with scales, lungs for breathing.
  2. Oviparous with internal fertilization.
  3. Homodont dentition.
  4. Some are aquatic, others terrestrial.

 

Class Aves (Birds):

  1. Internal jointed skeleton made of bone.
  2. Bilateral symmetry, body divided into head, trunk, and tail.
  3. Two pairs of limbs (pectoral and pelvic limbs).
  4. Well-developed central nervous system with a closed blood system.
  5. Skin covered by scales or feathers.
  6. Warm-blooded.

 

Class Mammalia (Mammals):

  1. Internal jointed skeleton made of cartilage or bone.
  2. Bilateral symmetry, body divided into head, trunk, and tail.
  3. Two pairs of limbs (forelimbs and hind limbs).
  4. Well-developed central nervous system, closed blood system.
  5. Skin covered by hair or fur.
  6. Warm-blooded.

This classification provides a comprehensive overview of plant and animal diversity based on agricultural and biological criteria.

 

Class Aves (Birds):

Birds, belonging to Class Aves, encompass a diverse group adapted to aerial life through wing modifications of the forelimb. Examples include pigeons, domestic fowls, ostriches, and ducks.

 

Characteristics:

  1. Homoeothermic: Maintaining a constant body temperature, irrespective of environmental changes.
  2. Feathers: Entire body covered except for legs, which are scaled.
  3. Beak: Mouth extended to form a beak for feeding.
  4. Hollow Bones: Rigid, hollow bones with air sacs, aiding lightness during flight.
  5. Internal Fertilization: Reproduction through internal fertilization.
  6. Respiration: Utilization of lungs for respiration.
  7. Wings: Forelimbs modified into wings for flight.
  8. Toothless: Beak used for feeding.

 

Class Mammalia (All Mammals):

Mammals, the most advanced in the animal kingdom, possess two body cavities separated by a diaphragm.

 

Characteristics:

  1. Homoeothermic: Maintaining a constant body temperature.
  2. Covering: Bodies covered with hairs or fur.
  3. Heterodont Dentition: Having different sets of teeth in terms of shape and function.
  4. Diaphragm: Thoracic cavity separated from the abdominal cavity by a diaphragm.
  5. Respiration: Lungs used for respiration.
  6. Brain: Well-developed brain.
  7. Pinnae: External ears referred to as pinnae.
  8. Viviparous: Giving birth to live young.
  9. Four-Chamber Heart: Fully developed four-chamber heart.
  10. Mammary Glands: Presence of mammary glands producing milk for young ones.
  11. Internal Fertilization: Reproduction involves internal fertilization.

 

Effects Of Agricultural Activities On Ecological System:

Agricultural activities impact ecosystems, potentially disrupting the balance through practices like bush clearing, burning, tillage, fertilizer use, and pesticide/herbicide application.

 

Bush Clearing:

Effects

  1. Exposure of soil to direct sunlight, altering microbial conditions.
  2. Increased risk of erosion without plant cover.
  3. Leaching of nutrients in unprotected soil.
  4. Potential desertification.
  5. Displacement of wildlife.
  6. Setback in plant succession.
  7. Destruction of plant species conservation.

 

Bush Burning:

Effects

  1. Loss of animal and microbial life.
  2. Gradual loss of soil fertility.
  3. Alkaline soil from burnt ashes.
  4. Soil exposed to wind and rain erosion.
  5. Delayed return of microorganisms.
  6. Reduced water-retaining capacity.
  7. Non-regeneration of some plant species.
  8. Disruption of balanced ecosystems.

Advantages:

  1. Renewal of grass growth.
  2. Speedy emergence of dormant seeds.
  3. Charcoal and wood for cooking.

 

Tillage:

Effects

  1. Loosening of soil, increasing erosion risk.
  2. Ecological changes in soil.
  3. Leaching of soil nutrients.
  4. Structural damage and microorganism loss.
  5. Elevated fire and heat risk on soil.

Advantages

  1. Improved soil aeration.
  2. Prevention of different plant appearances.
  3. Enhanced crop yield.

 

Fertilizer Use:

Effects

  1. Loss of organic humus.
  2. Soil crumb structure destruction.
  3. Water pollution if washed into rivers.
  4. Dry, powdery soil susceptible to wind erosion.
  5. Harm to useful soil organisms.

 

Pesticides and Herbicides:

Effects

  1. Loss of organic humus.
  2. Destruction of soil crumb structures.
  3. Water pollution.
  4. Dry, powdery soil prone to wind erosion.
  5. Harm to beneficial soil organisms.

 

Effects of Different Farming on Ecological System:

Crop Rotation:

Benefits:

  1. Allows land to fallow.
  2. Prevents erosion.
  3. Increases crop yield.
  4. Prevents disease infestations.
  5. Adds nitrates to the soil.
  6. Avoids nutrient depletion.

 

Crop Rotation:

Crop rotation involves the systematic planting of different crops in specified plots over multiple years to enhance soil fertility and manage pests effectively.

1st Year:

  1. 1st Plot: Maize
  2. 2nd Plot: Cassava
  3. 3rd Plot: Fallow
  4. 4th Plot: Groundnut
  5. 5th Plot: Yam

 

2nd Year:

  1. 1st Plot: Cassava
  2. 2nd Plot: Fallow
  3. 3rd Plot: Groundnut
  4. 4th Plot: Yam
  5. 5th Plot: Maize

 

3rd Year:

  1. 1st Plot: Fallow
  2. 2nd Plot: Groundnut
  3. 3rd Plot: Yam
  4. 4th Plot: Maize
  5. 5th Plot: Cassava

 

4th Year:

  1. 1st Plot: Groundnut
  2. 2nd Plot: Yam
  3. 3rd Plot: Maize
  4. 4th Plot: Cassava
  5. 5th Plot: Fallow

 

5th Year:

  1. 1st Plot: Yam
  2. 2nd Plot: Maize
  3. 3rd Plot: Cassava
  4. 4th Plot: Fallow
  5. 5th Plot: Groundnut

 

Mixed Farming:

Mixed farming integrates both animal and crop production on the same farm, providing several benefits:

  1. Allows animals to convert plant products into high-quality protein.
  2. Mitigates the risk of single crop failure.
  3. Economically viable, generating income from both crops and animals.

 

Mixed Cropping:

Involves growing more than one type of crop simultaneously on a piece of land, enhancing diversity and reducing the risk of crop failure.

 

Adverse Farming Methods:

Continuous cropping:

  1. Permanently cultivating a piece of land with potential drawbacks:
  2. Leads to soil mineral exhaustion.
  3. Reduces clearing costs.
  4. May result in low productivity and crop failure over time.

 

Monoculture or monocropping:

  1. Growing the same crop on the same land annually with adverse effects:
  2. Makes the environment unsuitable for many crops.
  3. Encourages the spread of pests and diseases.
  4. Risks crop failure and soil structure destruction.

 

Shift cultivation:

  1. Cultivating a piece of land for a few years before abandoning it for a new one, leading to:
  2. Wastage of land.
  3. Soil erosion.
  4. Migration of animals.

 

Pests:

Pests, such as insects or small animals, can damage crops and spread diseases to humans and animals.

 

Types of Plant Pests:

  1. Insect Pests:

Harmful insects cause damage to crops in the field and storage.

Examples: crop-eating, sap-sucking, biting and chewing, piercing and sucking insects.

 

  1. Worm Pests and Borers:

Some subterranean worms feed on plant roots, while others chew leaves, stems, and flowers.

 

  1. Animal Pests:

Mammal pests (e.g., monkeys, grass-cutters) and bird pests (e.g., fowls, guinea fowls) that destroy crops.

 

Effects of Pests:

  1. Destruction of vegetation.
  2. Competition for food.
  3. Reduction in crop quality and quantity.
  4. Financial losses for farmers.
  5. Increased costs for pest control.
  6. Disease transmission to both humans and plants.

 

Control of Pests:

  1. Chemical Control: Use of chemical substances like Aldrin, Vertox 85, Gammalin 20, and Didimac 25.
  2. Cultural Methods: Seasonal practices, crop rotation, regular weeding, correct spacing, and early harvest.
  3. Physical Methods: (a) Scaring, killing, collecting pests for mass destruction. (b) Setting traps, shooting, using scarecrows, and farm drums.
  4. Biological Control: Introduction of natural enemies to consume or control pest populations.

 

Life Cycle of Yam Beetle:

The pest bores into yam tubers, with cycles involving eggs, nymphs, larvae, and adults. It contributes to yam tuber destruction.

 

Life Cycle of Rhinoceros Beetle:

Found on oil palm trees, this pest’s life cycle includes eggs, larvae, pupa, and adults. It can kill trees and is controlled by burning dead trees.

 

Diseases of Agricultural Importance:

Diseases are categorized into viral, bacterial, fungal, and protozoal diseases, with general effects including reduced yield, decreased quality, malformation, death, financial losses, increased production costs, unattractiveness, and retarded growth.

 

General Control of Diseases:

  1. Clearing breeding grounds.
  2. Chemical applications.
  3. Vaccination for immunity.
  4. Good sanitation.
  5. Adequate feeding.
  6. Isolation of new stocks.
  7. Rotational grazing.
  8. Regular changing of animal bedding.
  9. Veterinary check-ups.

Disease examples include viral diseases like foot and mouth disease, bacterial diseases like anthrax, fungal diseases like blight, and protozoal diseases like trypanosomiasis. Control methods encompass chemical, cultural, physical, and biological approaches.

This comprehensive overview highlights the importance of integrated farming practices and effective pest and disease management for sustainable agriculture.

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