Ecosystems

Question 1

Define an ecosystem.

Answer 1

A characteristic community of interdependent species interacting with the abiotic components of their habitat.

Question 2

How did the energy from earth enable organisms to exist?

Answer 2

An unequal distribution of protons allowed non-living systems to transition to living systems. The oxidation of inorganic molecules like hydrogen gave the electrons need to reduce CO2 or methane into sugar. The energy released by these chemical reaction is what they used to make carbohydrates

Question 3

What are 4 biotic components of an ecosystem?

Answer 3

Habitats
Communities
Biomass
Food chains

Question 4

Define a habitat

Answer 4

An ecological or environmental area which provides the means of survival such as food, soil, temperature and pH.

Question 5

Define a community.

Answer 5

The members of a species living and interacting together in a habitat to form a population. Populations interact to form a community.

Question 6

What are primary and secondary consumers?

Answer 6

Primary consumers are herbivores, secondary consumers are carnivores.

Question 7

What is a detritus food chain?

Answer 7

Detritus - detritivore - decomposed.

Question 8

What is a detritivore?

Answer 8

An animal like an earthworm, that feed on small fragments of organic debris.

Question 9

What are decomposes?

Answer 9

Microbes such as bacteria and fungi that obtain nutrients from dead organisms and animal waste.

Question 10

What do the length of food chains depend on? (5)

Answer 10

1. More energy fixed = longer food chain. Tropical food chains are longer than arctic ones.
2. Efficiency of energy transfer
3. Predator - prey cycles
4. Larger ecosystems mean longer FC
5. 3D environments like aquatic systems and forests have longer food chains

Question 11

Why is 60% of light that falls on plants not absorbed?

Answer 11

1. Wrong wavelength
2. Reflected
3. Transmitted straight through the leaf

Question 12

What is photosynthetic efficiency and how is it calculated?

Answer 12

The measure of ability of a plant to trap light

Light the plant incorporates / total light x100

It may be as low as 1% in wild plants, but 7-8% in selectively bred plants.

Question 13

What is GPP?

Answer 13

The rate that plants convert light energy into chemical energy (sugars) in kJm-2y-1

Question 14

What is NPP?

Answer 14

GPP-respiration. A lot of GPP is released by the respiration of the plant to fuel e.g. Protein synthesis. The remainder is NPP. it represents the energy in the plants biomass (food available for primary consumers).

Question 15

What is primary productivity?

Answer 15

The rate producers turn light energy into biomass

Question 16

What is secondary productivity?

Answer 16

The rate consumers turn chemical energy from food into biomass (assimilate it into their cells / tissues)

Question 17

Give 3 reasons why energy is lost at each level of the food chain.

Answer 17

1. Energy is egested.
2. Energy is lost as heat.
3. Some parts of the animal contains energy but isn’t eaten, e.g. Bones and fur.

Question 18

Explain why carnivores lose less energy than herbivores.

Answer 18

Cellulose is not digested (in plants) so is lost in faeces. Carnivores lose about 20% of their energy whereas herbivores lose about 60%.

Question 19

Explain why carnivores convert energy more efficiently than herbivores.

Answer 19

Herbivores have a conversion efficiency of 10%.
Herbivores don’t eat all of the plants - e.g. not the roots.
Carnivores food is more quickly and easily digested - efficiency = 20%

Question 20

How do you calculate the efficiency of an energy transfer?

Answer 20

Energy incorporated into biomass after transfer / energy incorporated into biomass before transfer x100