Organisms & their environment

Question 1

briefly describe the non-cyclical nature of energy flow

Answer 1

1. The sun is the ultimate source of energy.
2. Explain photosynthesis
3. Energy in the producers is passed from one trophic level to another by feeding.
4. Flow of energy through the ecosystem is non-cyclic. Energy is lost as heat to the environment through respiration. Since this heat energy does not return back into the same system, it cannot be recycled.
5. Egested & excreted materials, & dead organisms conain trapped chemical energy. Decomposers break down any decaying organic matter. The respiration of decomposers releases heat and carbon dioxide into the atmosphere.

Question 2

producer

Answer 2

• trap light energy from the sun and convert it into chemical energy
• synthesise glucose from carbon dioxide and water to form glucose and oxygen via photosynthesis
• affect the lives of other organisms because they provide them with oxygen and energy

Question 3

consumer

Answer 3

• organisms that are unable to make their own food
• obtain energy and nutrients by feeding on other organisms

Question 4

trophic level

Answer 4

Feeding position of an organism in a food chain

Question 5

describe how carbon is cycled within an ecosystem

Answer 5

1. Photosynthesis
2. Feeding
3. Combustion
4. Respiration
5. Decomposition

Question 6

role of forests as carbon sinks

Answer 6

• Carbon dioxide is taken in by the trees and used in photosythesis.
• Due to photosynthesis, carbon compounds are formed which are then stored within the trees.
• When trees die, their remains may be buried deep in the ground to form coal which traps carbon

Question 7

role of oceans as carbon sinks

Answer 7

• Dissolved carbon dioxide is used by phytoplanktons, algae and water plants
• The carbon is then stored as carbon based molecules in them.
• This carbon is also stored as carbon based molecules in the organisms that eat PAW
• When these organisms die and are buried in the seabed, they form fossil fuel to keep the carbon trapped.

Question 8

effects of water pollution by sewage & inorganic waste

Answer 8

May contain disease-causing organisms such as bacteria
- Affect large no of ppl (if it gets into drinking water)
- Water-bourne diseases eg: cholera & typhoid

Contains phosphates & nitrates(nutrients for algae & water plants):
- Eutrophication: The process where water recipes excess nutrients (phosphates & nitrates), which causes excessive growth of algae & water plants
- Overgrowth of algae & floating water plants - prevent sunlight
- Submerged algae & water plants die (lack of sunlight) - decomposed by aerobic bacteria & fungi
- Bacteria feeding on decaying organic matter grow & multiply rapidly - use up oxygen in water
- Fishes die (lack of oxygen)

Question 9

effect of pollution due to insecticides

Answer 9

• due to bioaccumulation, insecticides accumulate inside the body of animals & plants as they may not be excreted, thus stored in fatty tissues of organisms that consume it
• due to amplification, amount of insecticide increase as animal in higher trophic level feed on anmals & plant of lower trophic level
• predators in higher trophic level would take in the greatest amount of insecticides, with bioaccumulation & bioamplification, large amount of insecticide is present in the body

Question 10

sewage treatment

Answer 10

1. Used water is first passed through bar screens to remove large, course materials (grit,rags)
2. Primary treatment: liquid flows through the tank very slowly - allows the solid suspensions to settle to the bottom of the tank as primary sludge
   This sludge is removed and fed into an aerobic digester.
3. The top liquid from this tank flows into an aeration tank.
4. In the aeration tank, the liquid is mixed with aerobic microorganisms, mainly bacteria. Bubbles of compressed air - pumped into the liquid through pipes in the floor of the tank. Dissolved oxygen is used by the microorganisms for aerobic respiration
5. The microorganisms breakdown the organic pollutants in the water. The treated water, together with the microorganisms, is channelled into the final settlement tank.
6. Here, the microorganisms settle to the bottom of the tank as sludge. A portion of this sludge is returned to the aeration tank for reuse, excess sludge is sent to the anaerobic digester.
7. The clean water at the top of the tank may be discharged as effluent into nearby rivers, streams and lakes
8. In anaerobic digester (closed tank, no oxygen), anaerobic bacteria decompose the sludge, break down the organic matter, producing biogas, mainly methane (Fuel: generate electricity for the functioning of the reclamation plant)
9. The remaining solid material is removed from the tank - fertiliser or burnt in an incinerator

Question 11

reasons for conservation

Answer 11

• Marine life are a major source of human food
• Rainforests are a source of raw materials for industries
• Prevents extinction of animal and plant species
• Maintenance of a large gene pool
• Maintenance of a balanced ecosystem
• Studies on wildlife provides useful information for humans
• Preservation of natural scenery and wildlife

Question 12

how conservation is done

Answer 12

Management of fisheries:
- regulating entry of ships into fishing grounds
- banning the harvesting or fishing of endangered species
- limiting the period of fishing in fishing grounds
- raising endangered species of fish in hatcheries and releasing them into fishing grounds where fish population are decreasing

Management of timber production:
- various gov laws ensure that trees felled for timber are cut down selectively & at regulated rate
- young trees not felled
- new seedlings planted to replace trees that were cut down for timber; reforestation (planting trees to replace trees cut down)