Ecosytems

Question 1

What is a community?

Answer 1

All populations of different species in the same area at the same time

Question 2

What is an ecosystem?

Answer 2

The living and non-living (biotic and abiotic) components of an environment

Question 3

What is a niche>

Answer 3

An organism’s role in an ecosystem. Like position in food web. Each species occupies their own niche governed by their adaptation to biotic and abiotic factors.

Question 4

What is Carrying Capacity?

Answer 4

The maximum population size an ecosystem can support.

Question 5

What is biomass?

Answer 5

The dry mass of carbon containing compounds in living materal

Question 6

How is the majority od energy lost between each trophic level?

Answer 6

Due to respiration and excretion. The remaining forms biomass.

Question 7

How do you measure the efficiency of biomass transfer?

Answer 7

efficiency = biomass transferred / biomass intake x 100%

Question 8

How do biotic and abiotic factors influence the productiveness of an ecosystem?

Answer 8

Plenty light, water, warmth and green plants maximises rate of photosynthesis, resulting in more carbohydrates being produced in the plants.

Question 9

How do humans manipulate biomass transfer?

Answer 9

Reducing energy lost at each trophic level.
- Reducing movement (so respiration) of animals
- Providing animals with higher energy food (icreases energy input)
- Keeping animals indoors to reduces energy transferred as heat
- Removing competition and predators (growing indoors and providing animals and plants with all they need)

Question 10

If plants and animals can’t obtain nitrogen through gas exchange (bc of its triple bond) how is it absorbed?

Answer 10

Microorganisms convert nitrogen gas into nitrogen containing substances (nitrogen fixing)

Question 11

What biological molecules contain nitrogen?

Answer 11

Proteins, nucleic acids and ATP

Question 12

What are the key processes of the nitrogen cycle?

Answer 12

1. Saprobiotic nutrition and microbes
2. Nitrogen fixation in soil and in Rhizobium
3. Ammonification (basically nitrogen fixation with with saprobiotes making HH4+ from decaying material)
4. Nitrification
5. Denitrification

Question 13

How does nitrogen fixation occur in the symbiotic relationship between plants and bacteria?

Answer 13

Nitrogen is first fixed by bacteria such as Rhizobium which live in the root nodules of leguminous plants such as pea plants. The bacteria have a mutualistic relationship with the plant where they exchange the fixed nitrogen for glucose.

Question 14

Describe Ammonification.

Answer 14

Saprobiotic microbes in anaerobic conditions, which are maintained with the use of special oxygen
absorbing proteins, enable nitrogen reductase to reduce nitrogen gas to ammonium ions (NH4+)

Question 15

Describe nitrification.

Answer 15

Nitrosomonas oxidise ammonium ions to nitrites (NO2-).
Nitrobacter subsequently oxidise nitrites to nitrates in the presence of oxygen (NO3 -).
Plants absorb nitrates from soil for nucleotide synthesis, to make ATP and proteins (Assimilation)

Question 16

Describe Nitrogen fixation.

Answer 16

nitrogen fixing bacteria convert nitrogen gas into ammonia, which forms ammonium ions (NH4+).

Question 17

Describe Denitrification.

Answer 17

In anaerobic conditions (e.g water logged soil), denitrifying bacteria convert nitrates (NO3-) back to nitrogen gas (N2) for and nitrous oxide for respiration.

Question 18

How does the carbon cycle begin?

Answer 18

Plants photosynthesise to fix carbon dioxide into carbohydrates which are ingested by animals. The respiration of all organisms converts the carbon in the carbohydrates back to carbon dioxide in the atmosphere or oceans. When they die or excrete the carbon is broken down by decomposers into carbon dioxide that respire using the carbs from waste matter.

Question 19

What is the imbalance in the carbon cycle leading to?

Answer 19

The acidification of the oceans and global warming. This imbalance is caused by deforestation and burning too many fossil fuels. Less CO2 is being used in photosynthesis and more is being produced by combustion.

Question 20

What is succession?

Answer 20

The change in an ecological community over time.

Question 21

What is a pioneer species?

Answer 21

The first in succession, the first to colonise the land.
E.g Lichen. They are adapted to survive harsh abiotic factors.
Their death and decomposition make abiotic factors less harsh, forming thin soil layer (humus)

Question 22

What is Primary sucession?

Answer 22

Mosses and smaller plants can now survive. They increase depth and nutrient content of the soil

Question 23

Why do existing species become outcompeted in succession?

Answer 23

Because each new species changes the environment in a way that becomes less suitable for the previous species.

Question 24

What are the effects of succession?

Answer 24

Biodiversity increases as species richness and number of species increases. The abiotic factors become less harsh and larger plant species and animals colonise the area.

Question 25

What is the final stage of succession?

Answer 25

The climax community (dominated by trees).

Question 26

What is a secondary succession?

Answer 26

When succession is disrupted (e.g forest fire) so plants and are destroyed. Succession starts again but the soil already exists so it doesn’t begin from the bare rick seral stage.

Question 27

What is deflected sucession?

Answer 27

The interruption of the process of succession. E.g mowing, grazing by livestock and controlled burning. A climax community won’t be reached.

Question 28

Why is deflected succession sometimes done purposefully?

Answer 28

By maintaining earlier stages of succession, a greater variety of habitats are conserved so a greater range of species survive.

Question 29

How is the conflict betwen human needs and conservation managed?

Answer 29

Compromises are needed. For example, forests can be coppiced to provide timber, fuel and furniture, whilst still allowing the tree to survive.

Question 30

What is sampling used for?

Answer 30

Estimating population size to measure the impact of changing environments on plants and animals we want to protect.
It is less stime consuming and more accurate to take samples to provide an estimate.

Question 31

How do we make sure a sample is representative of the population size?

Answer 31

Many samples (30+) are taken and sampling should be random to avoid bias