CLASSIFICATION OF LIVING THINGS
DIVISION CONIFEROPHYTA
Coniferophyta
is a division containing cone-bearing plants with needle-shaped leaves.
The smaller male cones produce a yellowish powder called pollen. It contains the male sex cells or gametes. The large female cone bears small seed-like structures called ovules. These contain female gametes.
The male cone is comparable to a flower but consists only of pollen-producing structures. The pollen is formed on the leaf-like scales of the cone. The female cone is comparable to a flower but with ovule-forming parts only. The ovules are attached to the leaf scales of the cone.
The distinguishing features and characteristics of the organisms in this Division are:
- They are mostly shrubs and trees, with needle-shaped leaves.
- Their reproductive structures are cones.
- The ovules are not enclosed inside an ovary wall.
- The dominant generation is the sporophyte.
- The majority are evergreen (they keep their leaves all year round).
- They are widely distributed (commonly found in areas with cold climate).
Advantages
- Conifers are relatively fast-growing trees.
- They are grown in plantations and produce useful timber (softwood).
- They are used extensively in the building industry, paper making, and furniture making.
- The trunks of conifers grow very tall and straight. They are often used as telegraph poles.
DIVISION ANGIOSPERMOPHYTA
(FLOWERING PLANTS)
This division contains a wide variety of forms, but all have common distinctive features as you will see.
There are two classes of angiosperms:
- Monocotyledonae
- Dicotyledonae
The features of angiosperms include leaves, stem, roots, and flowers.
Nearly all angiosperms have the same structure in their features, modified according to type and function:
- Sepal: protects the flower parts when it is in bud.
- Petals: are often brightly colored to attract insects to pollinate the flower.
- Stamen: produces the male gametes.
- Carpel: produces the female gametes.
- The flower of angiosperms has male structures called stamens. These have a structure called filament that supports anthers which produce pollen.
- The female structures are called carpels. A carpel is composed of stigma, style, and ovary. The ovules are formed inside the ovary. Once a carpel has been pollinated and the ovule successfully fertilized, the carpel becomes a fruit and the ovules become seeds.
The Distinguishing Features of Angiosperms
- Their reproductive structures are flowers.
- When anthers and carpels are found in the same flower (e.g., Delonix regia), the flower is said to be bisexual. Some plants produce unisexual flowers (e.g., maize produces male flowers that release pollen and female flowers that produce ovules).
- Ovules are enclosed in an ovary, and hence the seeds are enclosed in a fruit.
- Angiosperms vary greatly in form, size, and habitat.
- They can be woody (e.g., coconut tree), non-woody (e.g., maize plants), some are very small such as groundnut plants, while others are very large such as baobab trees.
- They occur in a wide range of terrestrial (land) and aquatic (usually freshwater) habitats.
Comparing Monocots and Dicots
A bean seed or groundnut seed has 2 cotyledons and is described as dicotyledonous. The maize grain has only one cotyledon and is described as monocotyledonous.
Examples of monocotyledons are maize, coconut, millet, palms, grasses, and orchids.
Examples of dicotyledons are beans, castor, groundnuts, mango, hibiscus plants, and balsam plants.
Definitions
1. MONOCOTYLEDON PLANTS
– Are plants whose seeds have one seed leaf (one cotyledon).
2. DICOTYLEDON PLANTS
– Are plants whose seeds have two seed leaves (two cotyledons).
A. DISTINCTIVE FEATURES OF MONOCOTYLEDONS
- Their seeds have one cotyledon.
- The vascular bundles of the stem are scattered.
- The petals are arranged in groups of three.
- Leaves have veins running parallel to one another.
- Most have fibrous root systems.
B. DISTINCTIVE FEATURES OF DICOTYLEDONS
- Their seeds have two cotyledons.
- The vascular bundles of the stem and root are arranged regularly.
- The petals are arranged mostly in groups of five or more.
- The leaves have veins arranged in a branched network.
- Most have tap root systems.
Advantages of Angiosperms
- Are used for timber.
- Are used as a source of charcoal and wood.
- Are used for manufacturing paper.
- Some angiosperms provide medicine (e.g., neem tree and foxglove).
- Some flowering plants are used for decoration.
- Angiosperms can be used in the production of certain industrial chemicals such as plastics, rubber, and tannins.
- Angiosperms can be a good source of organic manure for crop production when they decay.
- Are used for manufacturing resins.
Disadvantages of Angiosperms
- Some flowering plants may cause allergies in humans (e.g., pollen allergies).
- Potted plants in the house compete with humans for oxygen.
- Some plants are poisonous to humans (e.g., certain types of cassava).
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