Cambridge International A Level Biology Revision Guide

Chapter 18: Biodiversity, classification and conservation
Other services
Ecosystems provide services for us. Forests and peat bogs
absorb carbon dioxide and may help to reduce the effect of
increases in carbon dioxide in the atmosphere.
Organic waste material added to waters is broken
down by microorganisms. The transpiration of plants
contributes to the water cycle providing us with drinking
and irrigation water. Termites and ants along with many
species of fungi and bacteria recycle elements, such as
carbon, nitrogen, sulfur and phosphorus. Without this
recycling, the supply of nitrates, sulfates and phosphates
for plants would become limiting. Plant growth would
slow and there would be less food available for organisms
in other trophic levels.
National parks are areas of land that are controlled by
the government of a country and protected by legislation.
Agriculture, building, mining and other industrial
activities are strictly controlled. In some countries, such
as Kenya, national parks act as conservation areas where
populations of wild animals are maintained (Figure
18.29).
QUESTION
18.14 a List some of the threats to aquatic and terrestrial
ecosystems.
b State five reasons why it is important to maintain
biodiversity.
Protecting endangered species
An endangered species is one that is threatened with
extinction (Chapter 17, page 417). There are a variety of
ways to protect endangered species.
The best way to conserve any species is to keep it
in its natural habitat. Maintaining the natural habitat
means that all the ‘life support systems’ are provided.
In the public mind, conservation tends to concentrate
on individual species or groups of species. High-profile
programmes have centred on mammals, such as giant
pandas and whales. Equally important is the protection
of whole ecosystems threatened by development; the most
popular of these is the tropical rainforest although there
are many other, less well-known, rare ecosystems that
should be conserved, such as karst limestone, because they
are very vulnerable to pollution.
National parks
Most countries now set aside areas where wildlife and
the environment have some form of protection, and
where the activities of humans are limited. For example,
conservation areas may be set up where there are strict
limits on building, grazing farm animals, hunting or other
activities that might adversely affect animals and plants
that live there.
Figure 18.29 Elephants in the Amboseli National Park,
Kenya. Elephants throughout Africa are exposed to numerous
threats, not least poaching. Biodiversity suffers if their
numbers increase or decrease. There is a delicate balance
to achieve and this needs careful management by park
authorities.
The world’s first national park, the Yellowstone
National Park in the USA, was set up in 1872. It is the
last remaining nearly intact ecosystem of the northern
temperate climatic zone and serves as both a recreational
and a conservation area. Three of the animal species that
can be found there are listed in the USA as threatened
(bald eagle, grizzly bear and lynx) and two as endangered
(whooping crane and grey wolf).
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