Relevance Of Biology To Agriculture

CONTENT           

• Classification of plants
• Botanical classification
• Agricultural Classification
• Classification based on life cycle
• Classification based on size
• Effects of agricultural practices on ecological systems

CLASSIFICATION OF PLANTS

Plants exists in various forms and types hence, the need for classification.  Plants can be classified on the following bases

1. Botanical classification
2. Agricultural classification
3. Classification based on life cycle
4. Classification based on size

BOTANICAL CLASSIFICATION

The concept of binomial nomenclature has it that plant kingdom can be subdivided into divisions, classes, orders, families, general and species.  This is based on their structures, functions and evolutionary trends.  Plants are then generally classified into three brand groups

• Thallophytes (A)
• Bryophytes (B)
• Tracheophytes (C)

Tracheophytes are further grouped into pteridophytes (D) and spermatophytes (E).  The Spermatophytes can also be grouped into gymnosperms (F) and angiosperms (G).  The angiosperms are subdivided into dicot (H) and Monocot (I)

EVALUATION

1.            Outline the criteria (bases) for classifying plants

2.            List the three factors upon which botanical classification is based

AGRICULTURAL CLASSIFICATION

Agricultural classification of plants is based on:.

i.              The product obtained from the plants

ii.             The parts of the plant that is useful

iii.            The economic importance of the plants

Plants are therefore classified agriculturally into the following

1.            CROPS AND WEEDS: – plants that are needed on the farm are called crops while other unwanted are called weeds.                

2.            FOOD CROPS AND CASH CROPS: – crops grown mainly for human consumption are called food crops e.g. maize, yam etc.  Those grown mainly to earn money are cash crops e.g. cocoa, coffee

3.            ROOT CROPS: – are plants which store mainly starch in edible underground stems or roots e.g. yam, cassava etc.

4.            CEREAL CROPS: – these are monocotyledonous plants of grass family, whose grains are eaten e.g. maize, millet, guinea corn, rice, wheat, etc.  They are rich in carbohydrates.

5.            FRUITS CROPS:-  are rich in vitamins and minerals.  Fruits are also rich in sugar.  These include oranges, mangoes, avocado peers, cashew etc.  whose fruits are eaten

6.            VEGETABLE CROPS: – are herbaceous plants whose vegetable (leafy) parts are eaten.  They include spinach, lettuce, carrots, cabbage, okro, tomato, onion, pepper etc.  They are also rich in vitamins and minerals.

7.            LEGUMES: – are plants of beans family such as cowpea and groundnuts whose seeds are eaten.  They are rich in proteins

8.            SPICES:  Are plants whose parts are used for seasoning food such as pepper, curry, thyme and ginger.

9.            LATEX PLANTS:  Are plants that are grown for their useful latex (a milky fluid) e.g. rubber plants used for making natural rubber in the tropical countries

10.          FIBRE PLANTS:  Are plants which produce fibre for the purpose of rope making, textile and bags production e.g. cotton, hemp etc.

11.          BEVERAGE AND DRUG PLANTS: – Are plants whose parts are taken as stimulants or drugs e.g. tea, coffee, cocoa and kola nut, quinine tree for medicine.

12.          OIL PLANT: – Produce oil of economic value e.g. oil palm, sheanut, groundnut, coconut, castor oil plant and melon.

EVALUATION:

1.            What are the factors considered in agricultural classification of plants?

2.            Differentiate between fruits crops and vegetable crops

PLANT CLASSIFICATION BASED ON LIFE CYCLE AND SIZE

Based on life cycle (period or existence) plant can be classified as

a.            ANNUALS: – These are plants which complete their life cycle within one growing season or within a year e.g. Maize, Yam, Melon, cowpea, tomato etc.

b.            BIENIALS: – These complete their life cycle within two years e.g. Banana, plantain, pineapple etc.

c.             PERENNIALS: – These persist over (more than) two years producing their yields every season e.g. orange, mango, oil palm cocoa etc.

Plant based on size fall into three categories

1.            Herbs are small plants with fleshy stem e.g. Spinach, waterleaf etc.

2.            Shrubs are medium – sized plants with woody stem branch very close to the ground (soil) e.g. hibiscus

3.            Trees are big plants with woody trunk, which branch at the top e.g. Iroko, Mahogany, Cashew, and Coffee etc.

EVALUATION

1.            Classify the following plants based on their life cycle (a) Vegetable (b) Pineapple (c) almond tree

2.            Give two examples each of herbs, shrubs and tree crops

EFFECTS OF AGRICULTURAL ACTIVITIES ON ECOLOGICAL SYSTEM

The following agricultural or farming practices carried out by farmers have some consequences on the ecological system. These agricultural practices and their effects include;

a.            Bush Burning: Bush burning involves the setting of fire in the bush to clear out the vegetation.Effects of bush burning include

–              Destruction of the organic matter in the soil

–              Atmosphere is polluted with smoke.

–              Many of the micro-organisms are killed

–              exposes the soil to erosion and leaching

–              reduces the water holding capacity of the soil

–              Bush burning leads to the extinction of some animals

–              The ash produced by bush burning gives the soil a slightly alkaline nature

b.            Overgrazing: Overgrazing is a situation where more animals than what can be supported on a particular pasture are put there to graze. It is a way of exceeding the carrying capacity of the soil. Overgrazing

–              removes the vegetative cover of the soil

–              exposes the soil to erosion

–              destroys the soil structure

–              More faeces are dropped on the soil which could improve the fertility of the soil.

–              Weeds can eradicated from such lands

–              It leads to compactness of the soil resulting from continuous trampling of animals.

–              causes poor growth and regenerative capacity of vegetation

c.             Tillage: Tillage is defined as the working, digging or breaking up of the soil in preparation for the planting of crops. Tillage encourages leaching

–              helps to loosen the soil

–              it enhances proper aeration of the soil

–              tillage exposes the soil organisms and may kill some

–              it changes the structure and texture of the soil

–              tillage leads to changes in the ecology of the land

–              Intensive tillage can lead to loss of soil fertility.

–              It exposes the soil to erosion.

d.            Deforestation: Deforestation is the continuous removal of forest stand (trees) either by bush burning or indiscriminate felling without replacing them. Deforestation

–              It reduces water percolation due to absence of humus and dead leaves on the soil

–              It reduces the amount of rainfall in the area

–              Deforestation hinders micro-organisms activities in the soil

–              It results in loss of nutrients through leaching and erosion

–              It reduces wildlife population in the area concerned

–              It reduces the humus content of the soil

e.            Fertilizer application: This involves the application of certain chemicals or substances into the soil to improve its fertility. Effects of fertilizer application include

–              It brings about the loss of organic matter or humus

–              It deteriorates the structure of the soil

–              Fertilizer increases the porosity of the soil

–              It supplements nutrient content of the soil

–              Excessive application of fertilizer can cause soil acidity

–              The productive capacity of the soil is enhanced by the application of fertilizer

–              It stimulates vegetative growth, hence it reduces soil erosion

f.             Application of pesticides/herbicides: Pesticides are chemical substances which are used to destroy or kill pests while herbicides are also chemical substances in form of solution or gases capable of destroying weeds. Effects of pesticides application include

–              It causes pollution of the environment.

–              It affects or destroys other useful plants and animals.

–              It reduces the population of the target insects or plants.

–              Pesticides may leave undesirable residue in the environment.

–              When such chemicals are washed into rivers or lakes, they can cause death of aquatic animals.

EVALUATION

1.            State three effects of fertilizer application, tillage and bush burning on the ecosystem.

2.            Explain with reason the most ecologically friendly agricultural practice.

GENERAL EVALUATION

1.            Based on size, classify water leaf, hibiscus and oil palm

2.            Differentiate between shrubs and trees

3.            Discuss the botanical classification (using example where appropriate)

4.            In what ways are fruits and vegetable crops similar

5.            Differentiate between root and cereals crops

6.            Differentiate between annual and perennial crops giving two examples each.

WEEKEND ASSIGNMENT

1.            Which of the following is not an example of classification of plants   (a) Herbs and shrubs    (b) annual and perennials    (c) Graminae and enphorbinosae     (d) monocot and dicot

2.            Plants can be classified based on all these except (a) botanical  (b) size (c) agricultural use     (d) planting season

3.            Fruits crops are rich in (a) Vitamin and Minerals (b) Vitamins and protein  (c) Mineral and carbohydrate   (d) protein and carbohydrate

4.            Spices include   (a) Pepper and ginger    (b)  Palm oil and ginger   (c) Lettuce and carrot    (d) yam and maize

5.            Which of these does not have negative effect on the ecological system     (a) fertilizer application     (b) crop rotation     (c) tillage     (d) bush burning

THEORY

1.            State three effects each of the following farm practices on the ecosystem

(i)            Bush clearing

(ii)           Shifting cultivation

(iii)          monocropping

What are the classes of plants based on uses.