Module 6: Ecosystems

Question 1

Primary Succession:

Answer 1

Occurs on an area of land that has been newly formed or exposed. There is no soil or organic material. -> e.g eruption, sand dunes, silt deposition, glacial retreat

Question 2

Secondary Succession:

Answer 2

This occurs where soil is present but no animal or plant species. -e.g after forest fire of controlled burning

Question 3

What is succession?

Answer 3

Changes to the present species in an environment in response to changes in abiotic factors.

Question 4

What is a pioneer species?

Answer 4

The first species to occupy “new land” during succession.

Question 5

What are adaptations of a pioneer species?

Answer 5

The ability to produce large quantities of seeds or spores
Rapid germination of seeds
The ability to photosynthesise.
Tolerance to extreme conditions
The ability to fix nitrogen from the atmosphere

Question 6

What is the name of the steps of succession?

Answer 6

Seral stages

Question 7

What are the different colonisers present in an intermediate community?

Answer 7

Secondary coloniser, tertiary colonisers and scrubland.

Question 8

How fast is primary succession?

Answer 8

Slow

Question 9

How fast is secondary Succession?

Answer 9

Rapid

Question 10

How do the conditions of an ecosystem change over the course of succession?

Answer 10

The conditions become less hostile, species diversity increases and-so the ecosystem becomes more stable.

Question 11

What are organic products released into the soil known as?

Answer 11

Humus

Question 12

Secondary colonisers:

Answer 12

Use the humus deposited into the ground to grow, they act as a food source for primary consumers, allowing animal species to colonise the area.

Question 13

Tertiary colonisers:

Answer 13

As the conditions improve tertiary colonisers arrive, with waxy cuticles for water retention.

Question 14

Why does the soil become more fertile as succession continues?

Answer 14

Organic products and matter from plants deposit into the soil and rocks are eroded releasing minerals into the soil.

Question 15

What is the dominant species in each seral stage?

Answer 15

The species with the greatest biomass in the ecosystem in a given time.

Question 16

What is the name of the final seral stage?

Answer 16

The climax community.

Question 17

What is the climax community?

Answer 17

The final seral stage. The community is in a stable state and will show very little change over time. There is high biodiversity with a couple of dominant species. The species present is dependent on the climate.

Question 18

When does biodiversity peak during succession?

Answer 18

Mid-succession.

Question 19

Animal succession:

Answer 19

Similar to plant succession although much slower. The land must also not be geographically isolated to allow for the animal species to enter the area.

Question 20

What is the name of the final stage of succession when it’s artificially stopped?

Answer 20

Plagioclimax.

Question 21

What is one of the main reasons for succession being interrupted?

Answer 21

Agriculture:

• grazing and trampling of vegetation by domesticated animals - areas remain grassland
• Removing existing vegetation such-as shrubs and replaced with crops
• Burning down forests - Increases biodiversity due to secondary succession

Question 22

What are two examples of dynamic ecosystems?

Answer 22

Cold and Aquatic environments.

Question 23

What diagrams can be used to show the transfer of biomass?

Answer 23

Food chains and webs

Question 24

How is biomass measured?

Answer 24

Measure the mass of fresh material, kill the organism and heat it to obtain “dry mass”. This is then multiplied by the number of organisms in that trophic level.

Question 25

Why is water content removed from biomass?

Answer 25

Water content makes results less precise as water content varies daily and seasonally.

Question 26

What is the issue with how biomass is measured?

Answer 26

It doesn’t take into account seasonal changes and only provides the biomass at a particular time.

Question 27

How can the method to measure biomass be improved?

Answer 27

A larger sample could be taken over a longer period of time.

Question 28

What is nitrogen used for in plants and animals?

Answer 28

To synthesise proteins and amino acids.

Question 29

How is nitrogen transferred from plants to decomposers?

Answer 29

The plant will either be digested by animal or the plant will die and be directly digested by a decomposer

Question 30

How do decomposers transfer nitrogen into the soil?

Answer 30

Ammonification

Question 31

What is ammonification?

Answer 31

The dead matter is broken down into ammonia in the soil.

Question 32

What process transfers ammonium into nitrates?

Answer 32

The process of nitrification: 2 step process
Nitromonas converts ammonia into nitrite ions
Nitrobacter convert nitrite ions into nitrates

Question 33

In what form is nitrogen assimilated into plants?

Answer 33

Assimilation: Nitrate ions in the soil diffuse into the roots.

Question 34

What do denitrifying bacteria do?

Answer 34

Convert nitrates in the soil into nitrogen gas which is released into the atmosphere.

Question 35

What plants have nitrogen-fixing bacteria in their roots where nitrogen fixation occurs?

Answer 35

Legumes

Question 36

What is nitrogen fixation?

Answer 36

Nitrogen from the atmosphere is converted into ammonia in the soil.

Question 37

What is an abiotic process of nitrogen fixation?

Answer 37

Lightning.

Question 38

What is a human impact on the nitrogen cycle?

Answer 38

Over-use of fertilisers increases the nitrate content of the soil.
Waste from livestock can also increase the nitrate content of the soil.
The increase nitrate content can lead to eutrophication

Question 39

Detritivores:

Answer 39

Alternate name for saprophytes that speed up the decay process.

Question 40

What are the 3 types of organisms in the carbon cycle?

Answer 40

Consumers, Produces and Decomposers.

Question 41

How is carbon transferred from animals and plants to the atmosphere?

Answer 41

Respiration and decomposition

Question 42

How is carbon removed from the atmosphere?

Answer 42

Dissolved into the ocean, or photosynthesis.

Question 43

How is carbon transferred from decomposers to the atmosphere?

Answer 43

If decomposition is prevented, the dead material will become fossil fuels, which then undergo combustion releasing carbon into the atmosphere.

Question 44

What is the carbon containing compound present in the atmosphere?

Answer 44

CO2