Chapter 16 Man And The Environment

Question 1

State two ways in which energy may be lost between trophic levels. [2] (2016/A6)

Answer 1

Energy may be lost between trophic levels as heat energy is released into the environment through respiration. [1]
Energy may also be lost between trophic levels as trapped chemical energy in the egested and excreted materials. [1]

Question 2

State what is meant by the term carbon sink [2] (2014/A4)

Answer 2

A carbon sink is an area that stores more carbon than it releases [1] for long periods of time [1] such as forests/oceans

Question 3

Suggest why the ocean gives out less carbon than it takes in [5] (2014/A4)

Answer 3

1. Carbon dioxide is absorbed by ocean when it dissolves in. It is used during the photosynthesis of plants and algae.
2. Carbon is stored in structure of plants (e.g cell wall) and other organism( e.g. tissues) when they consume plants.
3. Upon death, the carbon in animals may be changed to fossil fuels and stored/sequestered.
4. Though Respiration by organisms in the ocean cause the release of carbon into the atmosphere, the rate of respiration is less than rate of photosynthesis and other processes that store/sequester carbon.
5. Thus the net effect is a removal of carbon from the atmosphere.

Question 4

Explain the importance of respiration, photosynthesis and combustion in the carbon cycle. [3] (2018/A7)

Answer 4

• Process P is respiration from animals which produces and releases carbon dioxide into the atmosphere [1]
• Process Q is the photosynthesis of plants which absorbs carbon dioxide from the atmosphere; it creates carbon sinks over indefinite/long periods of time, such as forests, as it stores more carbon than it releases [1]
• Process S is the combustion of fossil fuels from factories/ industrial power plants which produce and releases carbon dioxide into the atmosphere, which contributes to global warming [1]
• Processes P, Q and S help to maintain the level of carbon dioxide in the atmosphere and are part of the carbon cycle.

Question 5

Describe the role of bacteria and fungi in the carbon cycle. [3] (2018/A7)

Answer 5

• Bacteria and fungi are decomposers that break down dead material from plants and other organisms into simpler substances in the process of decomposition. They release carbon dioxide into the atmosphere.
• Anaerobic decomposition involves bacteria breaking down organic matter such as glucose into CO2 and methane (CH4).
• The carbon cycle recycles inorganic and organic material in the soil through the process of decomposition.