Chapter 22 - Our Impact On The Ecosystem Flashcards
Why does deforestation occur?(5)
1) land is needed for urban development
2) land is needed for growing crops
3) land is used for growing grassland for animal grazing
4) firewood is a source of fuel
5) wood is used as construction materials/turned into pulp for making paper
What are the effects of deforestation?(4)
1) soil erosion: when trees are removed, the soil is directly exposed to the force of the rain. There are also no roots to bind the soil.
2) flooding: eroded soil may be deposited in rivers and streams, blocking the flow of water, rising the water levels rapidly, causing floods
3) desertification: sunlight falls directly onto the soil, causing it to harden. The land become barren and plants cannot grow in the soil
4) climate changes: when trees are cleared, there will be less transpiration of rain water. There are less clouds, less rainfall.
How do uncontrolled fishing practices harm the ecosystem?(2)
1) modern fishing gear such as drift nets catches marine life indiscriminately. Marine life such as sharks and dolphins are often unintentionally caught. Although these animals are released back into the ocean, they often do not survive
2) cyanide poisoning and dynamite are used to stun reef fish and capture them. Both cyanide and explosives kill corals and other reef organisms.
What are the effects of uncontrolled fishing practices?
Some species of fish will be caught faster than they can be replaced. Young fish that are caught will not have a chance to grow and reproduce, and marine organisms that are unintentionally caught often do not survive. Marine population will thus decrease rapidly, causing some species to be endangered or extinct.
Define pollution.
It is the addition of substances to the environment that damage it, making it undesirable or unfit for life.
What is water pollution by sewage?
Sewage is waste matter from homes or industries, and untreated sewage is a good source of food for bacteria.
What are the effects of sewage?
1) bacteria grow and multiply rapidly, depleting the oxygen in the water. Other organisms might die due to insufficient oxygen.
2) if sewage contains excessive fertilizers (inorganic waste), eutrophication may occur
Define eutrophication.
It is the process where water receives excess nutrients like phosphates and nitrates, causing the excessive growth of algae and water plants.
What are the effects of eutrophication?
Excess nitrates and phosphates promote rapid growth of algae on surface of water bodies. This prevents sunlight from reaching the submerged plants. Submerged plants are unable to photosynthesize and die. Dead plants are decomposed by bacteria. Bacteria thus multiply and grow quickly, using up the oxygen in water. Other organisms then die due to lack of oxygen.
How does sewage treatment take place in water reclamation plants?(5)
1) settling tanks: heavier and bigger particles settle at the bottom and are removed as sludge
2) aeration tanks: bacteria is mixed with sewage. Bacteria secrete enzymes to digest organic waste into harmless soluble substances and carbon dioxide
3) final settling tank: microorganisms are removed from the treated sewage before being discharged into the sea.
4) anaerobic digesters: sludge from settling tank is treated with anaerobic bacteria.
5) treated sludge is dewatered and disposed of as a soil conditioner.
What happens when poisonous metals from inorganic wastes are dumped into water bodies? (4)
1) poisonous metals are absorbed by water plants in the water body
2) water plants are eaten by fish
3) fish caught from the sea contain high concentrations of poisonous metals
4) villagers who eat the fish are poisoned.
What is bioamplification?
It is when bioaccumulation occurs in an organism, and DDT gets passed along the food chain up the trophic levels, increasing in concentration. Organisms in the top trophic level thus have the highest concentration of the insecticide and suffer or die from its harmful effects.
What is conservation?
It is the protection and preservation of natural resources in the environment.
Why do we need conservation?
1) maintenance of biodiversity by preventing extinction of plant and animal species
2) maintain a stable and balanced ecosystem
3) maintain a large gene pool. By cross-breeding different varieties of wild plants and animals, agriculture produce can be improved.
5) preserve natural scenery and wildlife
6) for scientific research that provides useful information to humans
7) habitat for many animals and plants
8) source of raw materials for medicinal drugs, natural insecticides and food
How do we manage fisheries?(4)
1) ban use of drift nets, trawlers and dredges
2) use nets with a certain mesh size
3) limit the number of ships allowed in fishing grounds at any one time
4) raising endangered species of fish in hatcheries for release into the sea
