Relevance of Biology to Agriculture

The primary aim of agriculture is to provide adequate food for an ever increasing human population. The issue of food production, preservation, storage and wastage has been challenging to both the agriculturist and the government.

Botanical Classification

This system uses the binomial nomenclature, giving every plant two names (generic and specific). The generic name comes first with a capital letter, while the specific name is in lowercase. Both names are either italicized or underlined separately. Example: Rhizopus nigricans or Marchantia palmata.

Classification of Plants Based on Presence or Absence of Flowers:

• Non-flowering Plants:
  • Thallophyta: Plants with thalli, lacking roots, stems, leaves, flowers, and vascular tissues. Examples: bacteria, algae, fungi, lichens.
  • Bryophyta: Multicellular, non-vascular plants with stem-like and leaf-like structures, but lacking roots. They live in moist places and reproduce via spores. Examples include plants with rhizoids for absorbing nutrients.
  • Pteridophyta: Multicellular plants with true roots, stems, and leaves but lacking flowers. Their vascular system is primitive, and they reproduce by spores. Examples: ferns like Nephrolepsis and Dryopteris.
• Flowering Plants (Spermatophytes):
  • Angiosperms: Plants that produce seeds enclosed by a seed coat. Angiosperms are divided into monocotyledons and dicotyledons.
    • Dicotyledons: Plants with two seed leaves (cotyledons) and net-veined leaves. Examples: tomato, beans, mango, melon.
    • Monocotyledons: Plants with one seed leaf (cotyledon) and parallel-veined leaves. They have fibrous root systems.
  • Gymnosperms: Plants that produce naked seeds, meaning the seeds are not enclosed by any structure. Examples: pines, cones.

agricultural classification of plants

Agricultural classification of plants is based on:

• The economic importance of the plants
• The parts of the plant that are useful
• The product obtained from the plants

Classification based on product

• Crops and Weeds: Plants that are needed on the farm are called crops, while unwanted plants are called weeds.
• Food Crops and Cash Crops:
  • Food crops are grown mainly for human consumption, e.g., maize, yam.
  • Cash crops are grown mainly to earn money, e.g., cocoa, coffee.
• Root Crops: Plants that store starch in edible underground stems or roots, e.g., yam, cassava.
• Cereal Crops: Monocotyledonous plants from the grass family, whose grains are consumed, e.g., maize, millet, guinea corn, rice, wheat. They are rich in carbohydrates.
• Fruit Crops: These crops are rich in vitamins, minerals, and sugar. Examples include oranges, mangoes, avocado pears, cashew, whose fruits are eaten.
• Vegetable Crops: Herbaceous plants with edible leafy parts, rich in vitamins and minerals. Examples include spinach, lettuce, carrots, cabbage, okra, tomato, onion, and pepper.
• Legumes: Plants from the beans family, e.g., cowpea, groundnuts, whose seeds are eaten. They are rich in proteins.
• Spices: Plants whose parts are used for seasoning food, such as pepper, curry, thyme, and ginger.
• Latex Plants: Plants grown for their useful latex (a milky fluid), e.g., rubber plants used for making natural rubber in tropical countries.
• Fibre Plants: Plants that produce fiber for making ropes, textiles, and bags, e.g., cotton, hemp.
• Beverage and Drug Plants: Plants whose parts are taken as stimulants or drugs, e.g., tea, coffee, cocoa, kola nut, and the quinine tree for medicine.
• Oil Plants: Plants that produce oil of economic value, e.g., oil palm, shea nut, groundnut, coconut, castor oil plant, and melon.

Plant Classification Based on Life Cycle

• Annuals: These are plants that complete their life cycle within one growing season or year, e.g., tomato, cowpea, melon, yam, maize.
• Biennials: These plants complete their life cycle within two years, e.g., pineapple, plantain, banana.
• Perennials: These plants persist for more than two years, producing yields every season, e.g., cocoa, oil palm, orange, mango.

Plant Classification Based on Size:

• Herbs: Small plants with fleshy stems, e.g., waterleaf, spinach.
• Shrubs: Medium-sized plants with woody stems, branching close to the ground, e.g., hibiscus.
• Trees: Large plants with woody trunks that branch at the top, e.g., cashew, mahogany, Iroko, coffee.

Applications of Biology in Agriculture

Biology plays an important role in agriculture by helping to improve crop and livestock production. It is applied in agriculture in the following ways:

1. Pest control
2. Understanding the effects of climate on crops
3. Creation of pest-resistant plants
4. Food preservation
5. Selective breeding to improve agricultural plants and animals

Pest Control

Pest control is a key application of biology in agriculture.

Biological knowledge has enabled the development of methods to reduce or manage the population of harmful insects, animals, or plants. This is done by introducing, encouraging, or artificially increasing their natural enemies to keep their population at manageable levels.

The mechanisms used include natural processes like predation, parasitism, or herbivory.

By using these natural methods, pest control allows for the manipulation of ecological processes in a way that works in harmony with nature, serving agricultural purposes without harming the environment.

Effects of Agricultural Activities on Ecological Systems

Agricultural or farming practices carried out by farmers have various consequences on the ecological system. These practices and their effects include:

• Bush Burning: Bush burning involves setting fire to vegetation to clear the land. The effects of bush burning include:
  • Destruction of organic matter in the soil
  • Pollution of the atmosphere with smoke
  • Death of many soil micro-organisms
  • Exposure of soil to erosion and leaching
  • Reduced water-holding capacity of the soil
  • Extinction of some animal species
  • Alkalinity of the soil due to ash deposition
• Overgrazing: Overgrazing occurs when too many animals graze a particular pasture, exceeding the land's carrying capacity. Effects of overgrazing include:
  • Removal of the vegetative cover
  • Increased soil erosion
  • Destruction of soil structure
  • Improved soil fertility due to animal droppings
  • Eradication of weeds from the land
  • Compaction of the soil from continuous trampling by animals
  • Poor growth and regeneration of vegetation
• Tillage: Tillage refers to the working, digging, or breaking up of soil to prepare it for crop planting. Its effects include:
  • Encouraging leaching of nutrients
  • Loosening of the soil for better aeration
  • Exposure and potential death of soil organisms
  • Changes to the soil’s structure and texture
  • Alterations to the land's ecological balance
  • Loss of soil fertility due to intensive tillage
  • Increased soil erosion
• Deforestation: Deforestation is the continuous removal of trees, either through bush burning or indiscriminate logging without replanting. The effects of deforestation include:
  • Reduced water infiltration due to the absence of humus and dead leaves
  • Decrease in rainfall in affected areas
  • Disruption of micro-organism activity in the soil
  • Loss of nutrients through leaching and erosion
  • Decreased wildlife population
  • Reduced humus content in the soil
• Fertilizer Application: Fertilizer application involves adding chemicals or substances to the soil to improve fertility. Effects of fertilizer use include:
  • Loss of organic matter or humus
  • Deterioration of soil structure
  • Increased porosity of the soil
  • Supplementation of the soil’s nutrient content
  • Excessive use can lead to soil acidity

Application of Pesticides

Pesticides are chemical substances used to destroy or kill pests, while herbicides are chemicals in the form of solutions or gases that can destroy weeds. The effects of pesticide application include:

• Causes pollution of the environment
• Affects or destroys other useful plants and animals
• Reduces the population of the target insects or plants
• Pesticides may leave undesirable residue in the environment
• When washed into rivers or lakes, they can cause the death of aquatic animals

Application of Herbicides:

Herbicides: Herbicides are chemicals used for weed control, and they are categorized into two types: Selective weed killers and non-selective weed killers. Selective weed killers target specific weeds while sparing other plants, including crops. Non-selective weed killers, however, eliminate both weeds and cultivated crops.

Effects of herbicides:

• They destroy other useful plants and animals
• Excessive use of herbicides may damage crops and plants
• When washed into rivers, they can cause the death of aquatic animals