Chapter 21 - Ecology

Question 1

Define bioaccumulation.

Answer 1

It is a process whereby the concentration of toxins in the bodies of organisms are built up. It is because toxins like DDT are non-biodegradable. They cannot be broken down by bacteria, and cannot be removed from bodies of organism. They store in fatty tissues of organisms.

Question 2

How does energy flow?

Answer 2

It flows in a linear manner. It does not flow in a cycle, thus energy cannot be recycled. Chemical energy is transferred from one trophic level to another upon predation, and is released as heat finally.

Question 3

Define food chain.

Answer 3

A series of organisms through which energy is transferred in the form of food.

Question 4

Define trophic level.

Answer 4

It refers to the position an organism occupies in a food chain.

Question 5

Define producers.

Answer 5

Producers are organisms that synthesize their own food by absorbing light energy and converting it into chemical energy and store it as food during photosynthesis. They produce complex organic food, glucose, from inorganic raw materials: carbon dioxide and water.

Question 6

Define consumer.

Answer 6

Organisms that cannot make its own food and obtain energy by feeding on other organisms.

Question 7

How does energy losses occur along food chains?

Answer 7

As energy is passed on from one trophic level to another, 90% of it is lost as heat energy due to respiration and chemical energy in waste products such as uneaten body parts and egestion. Only 10% of energy stored as tissues is transferred to the next trophic level. The shorter the food chain, the less energy is lost to the environment, hence, the energy transfer is more efficient.

Question 8

What is the function of pyramid of numbers?

Answer 8

It allows for comparison of number of organisms present in each trophic level at a particular time.

Question 9

What is the function of pyramid of biomass?

Answer 9

It allows for comparison of dry standing mass if organisms present in each trophic level at a particular time.

Question 10

Why are some pyramids of biomass inverted?

Answer 10

The producer reproduces fast enough to support the consumer despite their smaller biomass.

Question 11

What are physical features that make up the abiotic environment? (6)

Answer 11

1) light intensity
2) temperature
3) water availability
4) oxygen content
5) salinity (salt concentration) of soil and water
6) pH of soil and water.

Question 12

Describe the carbon cycle. (3 release, 3 remove from environment)

Answer 12

1) removal from environment: photosynthesis - green plants absorb CO2 during photosynthesis to manufacture glucose
2) removal from environment: feeding - animals obtain carbon compounds by feeding on plants/other animals
3) removal from environment: preserved as fossil fuels
4) release into environment: respiration - plants and animals respire
5) release into environment: decomposition - decomposers such as bacteria, microbes and fungi break down dead organic matter and release CO2
6) release into environment: combustion - Combustion of fossil fuels release CO2 into the environment

Question 13

Why is the carbon cycle important? (2)

Answer 13

1) ensures a continuous supply of CO2 for plants to photosynthesize. Thus, food can be produced and fed upon by other organisms to stay alive
2) enables energy to flow through ecosystem in the form of carbon compounds

Question 14

Define carbon sinks.

Answer 14

Carbon sinks stores more carbon than it releases for long periods of time.

Question 15

What are 2 major carbon sinks?

Answer 15

1) oceans

2) forests

Question 16

Why are oceans carbon sinks?(2)

Answer 16

1) the carbon dioxide that dissolves in the ocean’s water is absorbed and used by algae and phytoplankton during photosynthesis
2) a portion of carbon compounds found in oceans is buried in the seabed and is the form of fossil fuels such as natural gas and oil.

Question 17

How do we increase the photosynthetic activity of phytoplankton?

Answer 17

Add iron compounds such as iron oxide and iron sulfate to the ocean. It stimulates the growth of phytoplankton and increases the phytoplankton’s photosynthesis rate.

Question 18

Why are forests carbon sinks?(3)

Answer 18

1) atomospheric oxygen is absorbed by plants and used in photosynthesis
2) a large amount of carbon compounds is stored in trees
3) remains of dead trees form coal, a fossil fuel.

Question 19

Explain why it is not possible for a food chain to have more than 4 trophic levels.

Answer 19

90% of energy is lost as you move up the trophic levels. Not enough energy to support the last trophic level.