Page 172 - Biology_F5

Comparative studies of natural groups of organisms

provided angiosperms an opportunity (n) Deciduous trees shed their leaves
to increase their domination in the during dry season to reduce the rate
terrestrial ecosystem. of transpiration, hence, limiting water
(h) Seeds produced by angiospermophytes loss.
have a highly nutritive tissue called (o) Asexual reproduction by vegetative
endosperm, which provides food for propagation ensures rapid growth and
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the developing embryo, cotyledons, maturity.
and sometimes, for the seedling when
it first appears. 3.6.5 Economic importance of plants
Plants are very important to the survival of
(i) They have developed extensive root other organisms. Without plants our day
system for anchorage on land and to day life would have been impossible.
absorption of water and mineral salts. Animals’ life is dependent on plants
Some plant roots have developed directly and or indirectly. However, there
symbiotic relationship with fungi are some plants with detrimental effects
to form mycorrhizae, which help to the life of animals. The following are
to increase the root surface area for advantages and disadvantages of plants.
absorption of nutrients and water from
the soil. Advantages of the kingdom Plantae
(a) Species in this kingdom are the main
(j) They have an advanced and elaborated source of food for heterotrophs. Primary
vascular system for transportation of consumers, such as browsers and
materials. For example, xylem has grazers depend on angiospermophytes
both vessel and tracheids for efficient as their sole source of food. Likewise,
water movement. human beings obtain various types
(k) They have stomatal pores for of food, such as vegetables, potatoes,
transpiration and gas exchange. These sugar, cereals, and fruits from plants.
are modified in various ways to reduce (b) They are important atmospheric
excessive water loss. purifiers due to their ability to sequester
(l) Angiospermophytes can control carbon, thus reducing carbon dioxide
evapotranspiration, depending on the concentration in the atmosphere. Carbon
environment in which a particular dioxide is one of the greenhouse gases;
species is adapted to live. For example, hence its reduction in the atmosphere
xerophytes have sunken stomata; most will in turn reduce the risks of global
of them are restricted on the lower side warming. Through photosynthesis,
of the leaf. plants produce oxygen which is used by

(m) They have cuticle, a thick waxy most of the organisms for respiration.
material covering the epidermal cells (c) Plants such as legumes have symbiotic
in all plant leaves. In addition, stems of relationship with nitrogen fixing bacteria
monocots restrict excessive water loss. in their root nodules. These bacteria are

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