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Chapter 22
Our Impact on the
Ecosystem (Part 2)
Objectives
Students should be able to
Outline the roles of microbes in sewage
disposal as an example of environmental
biotechnology
Discuss reasons for conservation of species
with reference to maintenance of biodiversity,
management of fisheries and management
of timber production
Reasons for Conservation
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To maintain a large gene pool. Many wild plants and
animals possess favourable genes. By cross-breeding
the different varieties of wild plants and animals, we can
improve agricultural produce, e.g. gaining a better yield
of milk or producing plants with better resistance to
diseases and drought.
To maintain a stable and balanced
ecosystem.
• Prevents disruption of natural
cycles, e.g. water and carbon cycles.
• Prevents global warming.
To prevent the
extinction of plant
and animal species.
(a) Tropical plants provide raw
materials for industries, e.g. rattan
to make furniture, rubber to make
tyres, fibres from cotton plants to
make cloth, and fibres from
coconut husks to make ropes.
To ensure the
conservation of
marine life, as they
are a major source
of human food.
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Conservation is of
scientific value. The
study of wildlife provides
useful information to
humans, e.g. we learn
about evolution from
studying wildlife.
REASONS FOR
CONSERVATION
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To maintain biodiversity.
• Rainforests house a large number of
species of animals and plants.
• Many tropical plants are of great
economic importance as they are sources
of raw material for industries, medicinal
drugs, natural insecticides and food.
(b) Tropical plants provide raw materials for medicinal
drugs, e.g. quinine from the bark of Cinchona, and
morphine, from the sap of the poppy plant, and natural
insecticides, e.g. pyrethrum, the chemical found in
chrysanthemum. Certain poisonous animals in the
rainforest may contain chemicals that have medicinal
value.
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Conservation
preserves natural
scenery and wildlife
for people to
appreciate. It also
maintains natural
resources for outdoor
recreational activities,
e.g. fishing, hiking
and skiing.
(c) Tropical
rainforests
provide food,
e.g. rice,
pineapple and
banana.
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Conservation measures
Indirectly through human population
control and reducing or eliminating
pollution
Directly through conserving natural
resources
Protecting wildlife
Environmental Biotechnology
This involves making use of biological
science to provide environmentally friendly
to reduce pollution and keep the
environment clean.
E.g. of environmental biotechnology
Decomposers in Sewage Treatment
 Decomposition of sewage takes a long time
 Hence , sewage is drained into large settling
tanks
 Bacteria present in the sewage secrete enzymes
to digest it
 Bacteria also feed on such digested products
 Liquid that results are filtered before being
discharged into sea
 Digested solid are dried and used as fertilisers
(a) Sewage from household is drained into settling
tanks, and then into sedimentation tanks.
(b) In the aeration tank
•
Bacteria mixed with sewage
•
Bacteria secrete enzymes to digest the solid
organic waste in the sewage into harmless
soluble substances and CO2.
•
Bacteria also feed on these products
(c) Liquid and disease-causing microorganisms are
removed and filtrate is discharged into the sea.
Solid remains is known as sludge
(d) Anaerobic bacteria breakdown organic matter in
the sludge
(e) Sludge is removed, dried and used as fertilisers.
How do we conserve the forests?
Prevention of massive cutting down of forests
Laws that ensure that trees for timber are cut
down selectively and at a regulated rate
How to conserve fishing grounds?
Banning the use of drift nets which trap all
forms of marine nets
Using nets with a certain mesh size so that
young fish are not caught
Regulating the entry of ships into fishing
grounds
Limiting the period of fishing in fishing grounds
Eliminate pollution of rivers and seas