organisms and their environment

Question 1

what is a carnivore?

Answer 1

a consumer that feeds on any other consumer from the trophic levels below it

Question 2

what is a community?

Answer 2

different populations of plants and animals living and interacting within a given habitat

Question 3

what is a consumer?

Answer 3

organisms that obtain their energy by feeding on other organisms

Question 4

what is a herbivore?

Answer 4

a primary consumer that feeds directly on plants

Question 5

what is an omnivore?

Answer 5

a consumer that feeds on both consumers and producers

Question 6

briefly describe the non-cyclical nature of energy flow

Answer 6

1. The principal source of energy input into biological systems within an ecosystem is the Sun
2. Energy flows into the ecosystem primarily as light energy and is eventually released as heat energy
3. The light energy entering the ecosystem is converted into chemical energy by plants during photosynthesis and is incorporated with elements such as carbon, hydrogen, oxygen and nitrogen into organic compounds such as carbohydrates, proteins and fats
4. The chemical elements can be recycled but the energy is released at different stages as heat energy and cannot be recovered
5. Thus, energy flow within an ecosystem is non-cyclic in nature and must be constantly supplied to the system

Question 7

Use ideas about energy transfer in photosynthesis and energy transfer between trophic levels to explain the advantage of short food chains

Answer 7

Only a small percentage of light energy is being converted into chemical energy [1]
by producers through photosynthesis from carbon dioxide and water into glucose [1]
When primary consumers feed on producers, energy is lost through heat during respiration/ undigested food during egestion/ uneaten body parts/ excreted as waste products [1]
Only a small proportion of 10% energy is available for the primary consumers [1] As energy moves up the food chain, lesser energy becomes available for higher trophic levels [1]
Advantages of short food chains [Reserve 1m]:
The shorter the food chain, the greater the amount of
energy available to the final consumer because lesser energy is lost to the environment. [1]
Short food chains are more efficient than long food chains in providing energy to the final consumer. [1]

Question 8

define trophic levels

Answer 8

a trophic level is the feeding position of an organism in a food chain

Question 9

what is the pyramid of numbers?

Answer 9

a pyramid of numbers is based on the total number of individual organisms at each trophic level

Question 10

what is the pyramid of biomass?

Answer 10

• biomass represents the total amount of living tissue within a particular trophic level
• biomass is usually expressed in terms of grams or organic matter per unit area
• thus, a pyramid of biomass represents the amount of potential food available within each trophic level

Question 11

what is the pyramid of energy?

Answer 11

• the pyramid of energy indicates the total amount of energy present in each trophic level
• it also clearly shows the loss of energy from one trophic level to the next because the energy transfer from one trophic level to the next is accompanied by the formation of waste and the conversion of potential energy into kinetic energy and heat energy
• generally, 90% of energy is lost to the environment and only 10% is available for the next trophic level

Question 12

how is 90% of energy lost to the environment?

Answer 12

• lost as heat during respiration
• uneaten body parts
• undigested food during egestion

Question 13

importance of carbon cycle

Answer 13

• to ensure a continuous supply of carbon dioxide for plants to carry out photosynthesis
• in photosynthesis, the energy from the sun is converted into chemical energy in food
  other living organisms rely on the food to stay alive
• to ensure energy flow through the ecosystem, from the sun to each trophic level in the food chain

Question 14

role of oceans as carbon sinks

Answer 14

oceans store carbon when carbon dioxide dissolves in the ocean’s water and also when the dissolved carbon dioxide is used by aquatic plants during photosynthesis to manufacture food. dead aquatic plants may also be trapped under ocean floors in the form of fossil fuels

Question 15

role of forests as carbon sinks

Answer 15

forests act as carbon sinks as plants absorb carbon dioxide for photosynthesis and the carbon remains in the plants as part of their constitute carbon compounds. dead plants can also continue to retain the trapped carbon in the form of fossil fuels for long periods of time

Question 16

effects of water pollution by sewage

Answer 16

• untreated sewage discharged into streams and rivers is a good food source for bacteria
• the bacteria grows exponentially, depleting the dissolved oxygen. The depletion of dissolved oxygen leads to the death of other aquatic life dependent on oxygen for aerobic respiration
• anaerobic bacteria continue to break down the organic waste and dead aquatic organisms, releasing gases like ammonia and sulfur dioxide. the water thus becomes inhospitable to different aquatic life forms
• furthermore, sewage can contain disease-causing bacteria like typhoid and cholera which may enter drinking water sources and cause epidemics

Question 17

effects of pollution due to insecticides

Answer 17

• insecticides are chemicals used to kill insects
• insecticides like DDT (dichloro-diphenyl trichloroethane) are pollutants because they are non biodegradable. DDT cannot be broken down by microorganisms and remain in the environment for a very long time
• insecticides can be carried by rainwater into streams, rivers and other water bodies and accumulate over time. they may kill aquatic animals or be taken up by land animals that drink the water or feed on the aquatic animals
• furthermore, insecticides like DDT are fat soluble and so will accumulate in the bodies of animals. these chemicals are then passed along the food chain, with the highest concentrations being found in animals up in the food chain. this process is referred to bioaccumulation
• bioaccumulation results in the top consumers in food chains suffering from the toxic effects of the high concentrations of these dangerous chemicals

Question 18

role of microorganisms in sewage treatment

Answer 18

Microorganisms are used in environmental biotechnology to treat sewage in order to reduce pollution and keep the environment clean.
• Sewage from households is drained into large settling tanks and sedimentation tanks where heavy suspended materials are removed.
• It is then pumped into aeration tanks and bacteria are introduced.
The bacteria secrete enzymes that digest solid organic waste into harmless soluble substances and carbon dioxide. The bacteria also feed on the digested products. The liquid generated by the bacterial digestion is filtered and discharged into the rivers or seas after disease-causing microorganisms are removed.
• Anaerobic bacteria are then used to break down organic matter in the remaining solid material called sludge. Finally, the sludge is removed, dried and used as fertilisers.

Question 19

importance of conversation

Answer 19

1. Conservation is important as it ensures the preservation and protection of natural resources in the environment.
2. Natural renewable resources include water, air, soil, forest and wildlife.
3. Non-renewable resources include fossil fuels and minerals.
4. Conservation is important for the maintenance of biodiversity, management of fisheries and the management of timber production.

Question 20

reasons for maintenance of biodiversity

Answer 20

• plants and animals are not forced into extinction
• For instance, tropical rainforests are home to a large and diverse collection of plant and animal species. The plants found in the rainforests may provide humans with new medicinal drugs, sources of food, natural insecticides and even raw materials for different industries. Examples of tropical plants that have provided raw materials include latex from the rubber plant, rattan used in furniture, and cotton to make cloth.
  • Marine biodiversity is important too as the ocean is a major source of food for humans.
  • Biodiversity also ensures that food chains and food webs can be sustained to ensure stable and balanced ecosystems.
  When ecosystems are disrupted, there can be far-reaching consequences like global warming.
  • Biodiversity also ensures that a sufficiently large and varied gene pool is maintained. This is important to ensure that crossbreeding produces new genetic varieties that are better suited to survive in changing environmental conditions or when faced with new diseases.

Question 21

reasons for management of fisheries

Answer 21

The management of fisheries ensures the continued availability of a very important source of food for humans. Measures taken must reduce or prevent pollution as well as encourage sustainable fishing approaches.

Question 22

measures that can be taken to reduce or prevent pollution and encourage sustainable fishing approaches

Answer 22

• Measures that can be taken include:
- ban the harvesting of endangered species (in fact, to prevent the extinction of these species, these fishes can be raised in fisheries and released into the wild to restock dwindling populations);
- ban the use of drift nets which indiscriminately capture all forms of sea life;
- encourage the use of nets with a mesh size that only captures adult fishes and allows young fishes to escape;
- strictly regulate the period of fishing in fishing grounds so as not to deplete the fish populations and provide sufficient time for them to breed.

Question 23

reasons for management of timber production

Answer 23

• Forests are extremely important as they are a major source of oxygen (via photosynthesis). They provide shelter to animals and form important habitats. They increase rainfall (by increasing the release of ground water through transpiration) and moderate weather patterns, and also protect the topsoil from erosion. Therefore, the cutting down of trees to provide timber cannot be done indiscriminately.

Question 24

measures that can be taken to manage timber production

Answer 24

• making laws to ensure that trees are cut at a sustainable rate so that the forests can still be maintained;
• not cutting down young trees and seed trees;
• planting new seedlings to replace the trees that were cut down;
• setting up forest reserves to ensure different varieties of trees survive;
• conducting research that allows trees sought for timber production to be grown more quickly and to provide better yields.