Topic 9 - Ecosystems And Material Cycle

Question 1

What is the equation for efficiency of energy transfer between trophic levels?

Answer 1

(Energy transferred to next level ÷ energy available at previous level) X 100

Question 2

What is eutrophication?

Answer 2

The process by which an aquatic ecosystem becomes enriched.

Question 3

What is the first stage of eutrophication?

Answer 3

Fertilisers enter the water, adding excess nitrates (more than plants in the water can take in)

Question 4

What is the second stage of eutrophication?

Answer 4

The excess nitrated cause algae to grow fast and block out sunlight.

Question 5

What is the third step of eutrophication?

Answer 5

Plants can’t photosynthesise due to lack of light and therefore start to decompose and die.

Question 6

What is the fourth step of eutrophication?

Answer 6

With more food available, microorganisms that feed on decomposing plants increase in number and use up oxygen in the water.

Question 7

What is the fifth step of eutrophication?

Answer 7

Organisms that need oxygen for aerobic respiration (e.g. fish) die.

Question 8

What happens after eutrophication?

Answer 8

Algae die because it has no nutrients. The water loses oxygen (anoxic) so it becomes clear but it’s dead water.

Question 9

What is a population?

Answer 9

All the organisms of one species in a habitat

Question 10

What is a community?

Answer 10

All the organisms of different species living in a habitat

Question 11

What is an ecosystem?

Answer 11

A community of organisms along with the abiotic conditions

Question 12

What does interdependent mean?

Answer 12

Organisms are interdependent. This means they depend on each other for things like food and shelter in order to survive and reproduce.

Question 13

What is a disadvantage of interdependence?

Answer 13

A change in the population of one species can have huge knock on effects for other species in the same community

Question 14

What is mutualism (with an example)?

Answer 14

It’s a relationship between two organisms from which both organisms benefit e.g. 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. The bees get food and the plants get help reproducing

Question 15

Why are parasites examples of non-mutualistic relationships (with example of parasite)?

Answer 15

Parasites take what they need to survive but the host doesn’t benefit e.g. fleas are parasites of mammals such as dogs. They feed on the host’s blood but don’t offer anything in return

Question 16

What are environmental changes caused by?

Answer 16

Abiotic and biotic factors which affect communities in many different ways

Question 17

What abiotic factors affect communities?

Answer 17

Temperature
Amount of water
Light intensity
Levels of pollutants

Question 18

What biotic factors affect communities?

Answer 18

Competitions

Predation

Question 19

What is the source of nearly all life on earth?

Answer 19

The Sun

Question 20

How do plants use light energy?

Answer 20

Plants convert a small % of light energy into glucose. They use some of the glucose immediately in respiration ad store some of the rest as biomass

Question 21

What is biomass?

Answer 21

The mass of living material that makes up an organism

Question 22

What happens, in terms of energy transfer, when an animal eats a plant?

Answer 22

it uses some of the energy it gets from the plant and some of the rest is stored in its biomass

Question 23

How is energy used by organisms?

Answer 23

To stay alive i.e. in respiration, which transfers energy for all life processes, including movement. A lot of energy is transferred to the surroundings by heat. This isn’t stored as biomass so isn’t transferred to the organisms in the next trophic level.

Question 24

Why doesn’t all of the energy stored as biomass get transferred to the next trophic level?

Answer 24

Not all of the organism is eaten (e.g. the bones) and because not all of the bits that do get eaten can be digested - undigested materials is lost from the food chain in faeces

Question 25

How can fish farms in areas of open area reduce biodiversity in surrounding areas?

Answer 25

1) Food is added to the nets to ffed the fish, which produce huge amounts of waste. Both the food and the waste can leak into the open water, causing eutrophication
2) Fish farming in open areas often acts as a huge breeding ground for a large number of parasites. These parasites an get out if the farm and infect wild animals, sometimes killing them
3) Predators are attracted to the nets and can become trapped in them and die
4) Sometimes farmed fish can escape into the wild which can cause problems for wild populations of indigenous species

Question 26

What is a non-indigenous species?

Answer 26

A species that doesn’t occur naturally in an area

Question 27

Why can non-indigenous species cause problems for indigenous species?

Answer 27

Non-indigenous species compete with indigenous species for resources like food and shelter. Sometimes they’re better at getting these resources and out-comped the indigenous species, which decrease in number and eventually die out. Also non-indigenous species sometimes bring new diseases to a habitat which often infect and kill the indigenous species and therefore reducing biodiversity.

Question 28

What do conservation schemes help?

Answer 28

They can help to protect biodiversity by preventing species from dying out

Question 29

Give examples of conservation methods?

Answer 29

• Protecting a species’ natural habitat
• Protecting species in safe areas outside of their natural habitat (e.g. zoos) and introducing captive breeding programmes to increase numbers
• The use of seed banks in order to store and distribute the seeds of rare and endangered plants.

Question 30

What are the benefits of maintaining biodiversity on a local and global scale?

Answer 30

1) Protecting the human food supply - over-fishing is a problem
2) Ensuring minimal damage to food chains - conserving one species is important to conserving other species in the same food chain
3) Providing future medicines - Plants becoming extinct means we may be missing out on valuable medicines
4) Cultural aspects - for example species may be important to and nation’s/area’s cultural heritage
5) Ecotourism - environmentally-friendly tourism helps bring money into biodiverse area
6) Providing new jobs - e.g. ecotourism, conservation schemes and reforestation schemes

Question 31

What is ‘food security’?

Answer 31

The world’s population is rising very quickly and it’s not slowing down. This means that global food production must increase too, so that we all have access to enough food that is safe for us and has the right balance of nutrition.

Question 32

5 factors affecting food security?

Answer 32

• Increasing human population
• Increasing consumption of meat, fish snd increasing animal farming
• Environmental changes caused by human activity
• Sustainability
• New pests and pathogens

Question 33

How are materials recycled through both biotic and abiotic components of ecosystems?

Answer 33

Living things are made up of elements that they take from the environment e.g. plants take in carbon and oxygen from the air and nitrogen from the soil
They turn these elements into complex compounds (carbohydrate, proteins and fats) that make up living organisms. Elements are passed along food chains when the animals eat the plants and each other
The elements are recycled - waste products and dead organisms are broken down by decomposers (usually microorganisms) and the elements in them are returned to the soil or air, reach to be taken in by new plants and put back into the food chain

Question 34

Describe the carbon cycle.

Answer 34

Green plants use the carbon from CO2 to make carbohydrates, fats and proteins
Eating passes the carbon compounds in the plant along to animals in a food chain
Both plant and animal respiration while organisms are live release CO2 back into the air
Plants and animals eventually die and decompose, or are killed and turned into useful products
When animals and plants decompose, they’re broken down into microorganisms, such as bacteria and fungi. These decomposers release CO2 back into the air by respiration, as they break down the material
Some useful plant and animal products, e.g. wood and fossil fuels, are burned (combustion). This also releases CO2 back into the air
Decomposition of materials means that their habitats can be maintained for the organisms that live there e.g. nutrients are retuned to the soil

Question 35

How is water recycled?

Answer 35

Energy from the sun makes water evaporate from the land and sea, turning it into water vapour. (Water vapour also evaporates from plants)
The warm 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 36

What is desalination?

Answer 36

Removing salts from salt water

Question 37

What is thermal desalination?

Answer 37

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

Question 38

How can revise osmosis be used as a method of desalination?

Answer 38

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

Question 39

Why does nitrogen in the air have to be turned into mineral ions such as nitrates before being used by plants?

Answer 39

Nitrogen is very unreactive and so it can’t be used directly by plants or animals

Question 40

Describe the nitrogen cycle.

Answer 40

Plants absorb mineral ions containing nitrogen and use the nitrogen in them to make proteins. Nitrogen is then passed along food chains in the forms of proteins, as animals eat plants and each other.
Decomposers break down proteins in rotting plants and animals, and urea in animal waste. This returns the nitrogen to the soil

Question 41

What is nitrogen fixation?

Answer 41

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

Question 42

Describe the two main ways that nitrogen fixation can happen.

Answer 42

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 43

What are the four types of bacteria involved in decomposition?

Answer 43

• Decomposers
• Nitrifying bacteria
• Nitrogen-fixing bacteria
• Denitrifying bacteria

Question 44

What do decomposers do?

Answer 44

Decompose proteins and urea and turn them into ammonia

Question 45

What does nitrifying bacteria do?

Answer 45

Turn ammonia in decaying matter into nitrites and then into nitrates

Question 46

What does nitrogen-fixing bacteria do?

Answer 46

Turn atmospheric nitrogen into ammonia which forms ammonium ions

Question 47

What does denitrifying bacteria do?

Answer 47

Turn nitrates back into nitrogen gas. This is of no benefit to living organisms and are often found in waterlogged soils

Question 48

Which invertebrate animals are indicators of clean water and why?

Answer 48

Invertebrate animals like stonefly larvae and freshwater shrimps are good indicators of water pollution because they’re very sensitive to the concentration of dissolved oxygen in the water. If you find stonefly larvae in a river, it indicates that the water is clean

Question 49

Which invertebrate species are adapted to living in polluted conditions?

Answer 49

Bloodworms and sludge-worms indicate a very high level of water pollution

Question 50

What can air pollution be monitored by and why?

Answer 50

By looking at particular types of lichen that are sensitive to the concentration of sulphur dioxide in the atmosphere. The number and type of lichen at a particular location will indicate how clean the air is

Question 51

What amount and type of lichen indicates clean ear?

Answer 51

Lots of lichen - especially bushy lichen, which need cleaner air than crusty lichen

Question 52

Where is blackspot fungus found and what does it indicate?

Answer 52

It’s found on rose leaves and indicates clean air as it is sensitive to the level of sulphur dioxide in the air

Question 53

What ways can you use indicator species to measure pollution?

Answer 53

1) Do a simple survey to see if indicator species are present or absent from an area - is quick but doesn’t tell you how polluted an area is
2) Counting the number of times an indicator species occurs in an area - given a numerical value so you can compare the levels of pollution amongst different places

Question 54

Advantages and disadvantages of suing indicator species?

Answer 54

Simple and cos-effective
Doesn’t give accurate figures for exactly how much pollution is present. There may also be factors other than pollution playing a role in the presence or absence of a species in an environment

Question 55

Examples of non-living indicators.

Answer 55

Dissolved oxygen meters and chemical tests are used to accurately measure the concentration of dissolved oxygen in water to show how the level of water pollution is changing
Electronic meters and various laboratory tests are also used to accurately measure the concentration of sulphur dioxide in air to show how air pollution is changing

Question 56

What is most decomposition done by?

Answer 56

Microorganisms like soil bacteria and fungi (known as decomposers)

Question 57

What does the rate of decomposition depend on?

Answer 57

Temperature
Water content
Oxygen availability

Question 58

How does temperature effect the rate of decomposition?

Answer 58

A warm temperature speeds up the rate of enzyme-controlled reactions in microbes, so decay happens faster. Enzymes denature if temperatures get too hot

Question 59

How does water content effect the rate of decomposition?

Answer 59

Decay takes place faster in moist environments because the organisms involved in decay need water to survive and carry out biological processes

Question 60

How does oxygen availability effect the rate of decomposition?

Answer 60

Rate of decomposition happens faster when there is plenty of oxygen available. Many microorganism need oxygen for aerobic respiration. Some decomposers don’t need oxygen to respire, but these decomposers work slower anyway

Question 61

Examples of preservation methods that slow down decomposition.

Answer 61

• Storing food in a fridge or freezer lowers the temperature of the food. This slows down the decomposers’ rate of reproduction (or stops it all together in the case of freezing)
• Storing food in airtight cans stops microorganisms from getting in. Once the food is in, the cans are sealed and sterilised (by exposing then to a high pressure and temperature) to kill any microorganisms present
• Drying food removes the water that microorganisms need to survive and reproduced as does adding salt or sugar, which causes the microorganisms to lose water by osmosis