SS1 Biology Lesson Note on Relevance of Biology to Agriculture

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CLASS: SS I

TOPIC: RELEVANCE OF BIOLOGY TO AGRICULTURE

CONTENT:

1. Classification of Plants

• Botanical classification
• Agricultural classification
• Classification based of life cycle

2. Effects of Agricultural Activities on Ecological system
3. Pests and Diseases of Agricultural Importance

SUB-TOPIC 1: CLASSIFICATION OF PLANTS

Classification of plants is based on botanical techniques and agricultural techniques. The botanical techniques where all plants are grouped into plant kingdom based mainly on structure, function and evolutionary trends is not very useful to a farmer. The agricultural techniques involve nature of the products and life cycle. Hence plant can be classified based on the following:

1. Botanical classification
2. Nature and uses of products
3. Life cycle

(I) BOTANICAL CLASSIFICATION

This is the classification system of flora and fauna that uses the binomial system of nomenclature in which every plant is given two names (generic and specific names). The generic names are always written first starting with a capital letter while the Last which is the specific names are written in small letters. The names are either italicized or underlined separately. E.g. Rhizopus nigricans or Marchantia palmata.

Based on what is present or absent in the plants, botanists grouped plants by considering the plants’ structure, presence of flower,s and mode of reproduction.

Plants are classified into two groups

• Non flowering plant
• Flowering plants

(i) Non-flowering plants

These are plants that do not have or produce flower. They are lower plants lacking vascular bundles, they lack true roots stems and leaves. The non-flowering or seedless plants are classified into three groups:

1. Thallophyta: these are plants that have bodies called thalli. They lack organs like roots, stems, leaves, flowers and vascular tissues. Examples: Algae, fungi, bacteria and Lichens.
2. Bryophyta: the plants are multicellular and non-vascular. They have stem-like and leaf-like structures but lack roots. Bryophytes live in moist place and reproduce by spores. They have rhizoids through which the plant absorbs nutrients from the soil.
3. Pteridophyta: they are multicellular plants with true roots, stems and leaves but lack flowers. The vascular system os primitive as well as chlorophyll. They reproduce by spores. Some of them are aquatic while some are terrestrial e.g. ferns (Dryopteris, Nephrolepsis).

(ii) Flowering plants:

These are the higher plants called spermatophytes or seed plants. They produce flowers and are vascular plants. Spermatophytes are further grouped and classified into angiosperms and gymnosperms.

Angiosperms: these are plants that produce seeds which are enclosed. Seed is produced and protected by a seed coat. Angiosperms are further grouped into dicotyledons and monocotyledons.

• Dicotyledons are plants with two seed leaves or cotyledons. The leaves are net-veined or reticulate e.g. beans, melon, mango and tomato.
• Monocotyledons are plants with one seed leaf or one cotyledon. They have parallel-veined leaves. They possess fibrous root systems.

Gymnosperms: this group also produces see but the seeds are naked. The seeds are not enclosed in the plant e.g. pines and cones.

(II) AGRICULTURAL CLASSIFICATION

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