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a) Habitat destruction/alteration and loss:
- this is greatest threat to wild plant and animal species, since habitat is where the species seek food, shelter and breed. As the human population undertake development activities there is disturbance/ alteration and loss of many habitats for wild species. Habitats are destroyed through:- Deforestation, Human settlement and construction, Draining and reclaiming wetlands, Modern farming, where natural ecosystem are replaced with single crops, Mining, etc.
b) Over harvesting/overexploitation of biological resources:
- may occur due to poaching, over fishing, commercial hunting – killing animals for profit from their products like fur, meat skin, tusks etc. Subsistence hunting, animals are killed for food and sport hunting animals are killed for recreation or leisure.
c) Predators and pests control:
- Extinction or near extinction can occur because of attempt to exterminate pests and predator species that compete with human and livestock for food.
d) Pets, zoos and medical research:
many birds are sold each year; most of them end up as pets. Some species of exotic plants (e.g. cacti) are gathered illegally and sold to collectors, where they are used to decorate homes; offices etc., many animals (e.g. mice, guinea pigs etc.) are used for toxicity testing, biochemical research and drug development. This is serious especially to endangered species.
e) Pollution:
- chemicals, industrial wastes, acid deposition, excess heat from electric power plants etc. have wiped out some of fish species. Slowly biodegradable pesticides such as DDT and Dieldrin have been magnified in food chains and have caused reproductive failures and eggshell thinning of important birds. (Bio magnification- build-up chemical elements or substances in organisms in successively higher tropic levels)
f) Introduction of exotic/alien species:
- in some cases when alien species are introduced into a new geographical area, it can cause population decrease or even extinction of one or more existing species, because of preying on existing species, destroying its habitats or through competition for food.
g) Cross-breeding –
This is where hybrid replace the natural species of plants and animals
marto answered the question on March 20, 2019 at 11:08
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