Topic 9 - Ecosysems And Cycles

Question 1

Ecosystem

Answer 1

All organisms and the environment in which they live.

Question 2

Community

Answer 2

All the organisms of different species that live and interact in an ecosystem.

Question 3

Population

Answer 3

A group of one species living in a particular area.

Question 4

Organism

Answer 4

An individual animal, plant, or single-celled life form.

Question 5

What is the biggest to smallest?

Answer 5

Ecosystem
Population
Community
Organism

Question 6

Abiotic factors

Answer 6

Non-living variable that can influence where organisms live.

Question 7

Biotic factors

Answer 7

Interactions associated with living organisms. They can also influence the distribution of organisms in an ecosystem.

Question 8

2 main biotic factors which affect distribution of organism

Answer 8

Competition
Predation

Question 9

What do organisms have to compete for?

Answer 9

Food
Water
Space
Light
Oxygen
Mates

Question 10

Interdependence

Answer 10

In a food web, changes in the population of one organism have an effect on the populations of other organisms.

Question 11

Trophic level

Answer 11

Describes the level a specific organism occupies in a food chain.

Question 12

What is an example of a win-loose?

Answer 12

Parasites are organisms that live on or in a host organism. The parasite benefits, the host does not and may be harmed.

Fleas are parasites of mammals such as dogs. Fleas feed on the hosts blood but don’t offer anything in return.

Question 13

What is an example of a win-win?

Answer 13

Mutualism is a relationship between organisms of a different species where both organisms benefit.

Bees and flowering plants have a mutualistic relationship. When bees visit flowers to get nectar, pollen is transferred to their bodies. The bees then spread the pollen to other plants when they land on their flowers. Bees get food and the plants get help reproducing.

Question 14

Process of eutrophication?

Answer 14

1) Too much fertiliser is used by farmers - it ends up being washed into rivers and lakes.
2) Fertiliser in the river water increases plant growth just as it does on land.
3) Algae grow rapidly on the surface of the water (called eutrophication).
4) Algae block out sunlight for other plants so they stay to die.
5) Bacteria feeding on the dead plant material uses up the oxygen in the water.
6) Fish may then die through lack of oxygen.

Question 15

What is fish farming?

Answer 15

Overfishing of wild fish has damaged some aquatic ecosystems. Fish farming aims to produce more fish and so reducing overfishing of wild fish.

Question 16

Advantages of fish farming?

Answer 16

• Grow rapidly
• Competing species kept out
• Protected against predators
• Fed better

Question 17

Disadvantages of fish farming?

Answer 17

• Kept in small space
• Disease more likely to occur and can be more easily spread
• Pesticides and antibiotics may be needed to control disease
• Uneaten food and faeces sinks to the bottom of the tank, changing conditions

Question 18

Non-indigenous species

Answer 18

A species that doesn’t naturally occur in an area.

Question 19

Disadvantages of non-indigenous species?

Answer 19

• Compete with indigenous species for resources like food and shelter.
• They sometimes bring new diseases to a habitat.

Question 20

Things we can do to increase biodiversity?

Answer 20

Reforestation
Conservation schemes

Question 21

Reforestation

Answer 21

When land where a forest previously stood is replanted to form a new forest.

Question 22

Conservation schemes

Answer 22

Help to protect biodiversity by preventing species from dying out.
• Protecting a species’ natural habitat.
• Protecting species in safe areas outside of their natural habitat and introducing captive breeding programmes to increase numbers.
• The use of seed banks to store and distribute the seeds of rare and endangered plants.

Question 23

Benefits of maintaining biodiversity

Answer 23

• Protecting the human food supply.
• Ensuring minimal damage to food chains.
• Providing future medicines.
• Cultural aspects.
• Ecotourism.
• Providing new jobs.

Question 24

How do different materials cycle through the abiotic and biotic components of an ecosystem?

Answer 24

• Living things are made of elements they take from the environment.
• They turn these elements into the complex compounds that make up living organisms. Elements are passed along food chains when animals eat the plants and each other.
• The elements are recycled - waste products and dead organism are broken down by decomposers and the elements in them are returned to the soil or air, ready to be taken in by new plants and put back into the food chain.

Question 25

Carbon cycle

Answer 25

• CO2 is removed from the air in photosynthesis by green plants and algae - they use the carbon to make carbohydrates, proteins and fats. They are eaten and the carbon moves up the food chain.
• CO2 is returned to the air when plants, always and animals respire. Plants and animals eventually die and decompose, or are killed and turned into useful products. When plants and animals decompose they are broken down by by microorganisms, such as bacteria and fungi. These decomposers release CO2 back into the air by respiration as they break down the material.
• CO2 is returned to the air when wood and fossil fuels are burnt (combustion) as they contain carbon from photosynthesis.

Question 26

Why is decomposition important?

Answer 26

It means that habitats can be maintained for the organisms that live there, e.g. nutrients are returned to the soil and waste material, such as dead leaves, doesn’t just pile up.

Question 27

Water cycle

Answer 27

• Energy from the sun makes water evaporate from the land and seas, turning it into water vapour. Water also evaporates from plants - known as transpiration.
• The warm water water vapour is carried upwards. When it gets higher up it cools and condenses to form clouds.
• Water falls from the clouds as precipitation onto land, where it provides fresh water for plants and animals.
• It then drains into the sea and the whole process starts again.

Question 28

What can be used to produce potable water in times of drought?

Answer 28

Desalination
Removes salts (mineral ions) from salt water (sea water).

Question 29

Thermal desalination

Answer 29

• Salt water is boiled in a large enclosed vessel, so that the water evaporates.
• The steam rises to the top of the vessel, but the salts stay at the bottom.
• The steam then travels down a pipe from the top of the vessel and condenses back into pure water.

Question 30

Reverse osmosis

Answer 30

• Salt water is first treated to remove solids, before being fed at very high pressure into a vessel containing a partially permeable membrane.
• The pressure causes the water molecules to move in the opposite direction to osmoses - from a higher salt concentration to a lower salt concentration.
• As the water is forced through the membrane the salts are left behind, removing them from the water.

Question 31

The nitrogen cycle

Answer 31

• The atmosphere contains 78% nitrogen gas.
• This is very unreactive and so it can’t be used directly by plants or animals.
• Nitrogen is needed for making proteins for growth, so living organisms need it somehow.
• Nitrogen in the air needs to be turned into mineral ions such as nitrates before plants can use it.
• Plants absorb these mineral ions from the soil and use the nitrogen in them to make proteins.
• Nitrogen is then passed along food chains in the form of proteins as animals eat plants.
• Decomposers break down proteins in rotting plants and animals, and urea in animal waste.
• This returns the nitrogen to the soil - so the nitrogen in these organisms is recycled.

Question 32

Nitrogen fixation

Answer 32

The process of turning N2 from the air into nitrogen-containing ions in the soil which plants can use.

There are 2 main ways that this happens:
• Lightning - there’s so much energy in a bolt of lightning that it’s enough to make nitrogen react with oxygen in the air to give nitrates.
• Nitrogen fixing bacteria in roots and soil.

Question 33

Bacteria involved in the nitrogen cycle?

Answer 33

• Decomposers - decompose proteins and urea and turn them into ammonia. Ammonia forms ammonium ions in solution that plants can use.
• Nitrifying bacteria - turn ammonia in decaying matter into nitrites and then into nitrates.
• Nitrogen fixing bacteria - turn atmospheric N2 into ammonia which forms ammonium ions.
• Denitrifying bacteria - turn nitrates back into N2 gas. This is no benefit to living organisms. Denitrifying bacteria are often found in water clogged soils.

Question 34

Nitrogen fixing bacteria

Answer 34

Some nitrogen fixing bacteria live in the soil.
• Others life in the nodules on the roots of legume plants.
• When these plants decompose, the nitrogen stored in them and their nodules is returned to the soil.
• Nitrogen containing ions can also leak out of the nodules during plant growth.
• The plants have a mutualistic relationship with the bacteria - bacteria get food from the plant and the plant gets nitrogen containing ions from the bacteria to make into proteins.

Question 35

How do farmers increase the amount of nitrates in the soil?

Answer 35

• Crop rotation - This is where instead of growing the same crop in a field year after year, different crops are grown each year in a cycle. The cycle usually includes a nitrogen fixing crop which helps to put nitrates back into the soil for another crop to use the following year.
• Fertilisers - spreading animal manure or compost on fields recycles the nutrients left in plant and animal waste and returns them to the soil through decomposition. Artificial fertilisers containing nitrates can also be used but these are very expensive.

Question 36

Quadrat

Answer 36

A quadrat is a square frame enclosing a known area to compare how common and organism is in 2 sample areas.
• Place a Quadrat on the ground at a random point within the first sample area.
You could do this by dividing the sample area into a grid and using a random number generator to pick coordinates to place you quadrats at. This will help to make sure the results you get are representative of the whole sample area.
• Count all the organisms you are interested in within the quadrat.
• Repeat steps 1 and 2 lots of times.
• Work out the mean number of organisms per quadrat within the first sample area.
• Repeat steps 1 to 4 for the second sample areas.
• Compare the 2 means.

Question 37

Belt transects

Answer 37

You can use quadrats to help find out how organisms are distributed along a gradient.
• Mark out a line in the area you want to study.
• Then collect data along the line using quadrats placed next to each other. Collect data by counting all the organisms of the species you’re interested in, or by estimating percentage cover.
• You could also record other data such as the mean height of the plants you’re counting or the abiotic factors in each quadrat.
• Repeat steps one and 2 several times, then find the mean number of organisms for each quadrat.
• Plot graphs to see if the changing abiotic factor is correlated with a change in the distribution of the species you’re studying.