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GCSE Edexcel Biology > B9 - Ecosystems and Material Cycles > Flashcards

B9 - Ecosystems and Material Cycles Flashcards

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1
Q

Define

Individual.

A

a single organism

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2
Q

Define

Population.

A

all the organisms of one species in a habitat

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3
Q

Define

Habitat.

A

the place were an organism lives

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4
Q

Define

Species.

A

a group of similar organisms that can reproduce to give fertile offspring

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5
Q

Define

Community.

A

all the organisms of different species living in a habitat

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6
Q

Define

Ecosystem.

A

a community of organisms along with all the non-living (abiotic) conditions

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7
Q

What is

Interdependence?

A

organisms depending on eachother for things like food and shelter in order to survive and reproduce

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8
Q

What does interdependence mean for communities?

A

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

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9
Q

Define

Mutualism.

A

a relationship between two organisms from which both organisms benefit

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10
Q

Define

Parasite.

A

An organisms that lives very closely with a host species. The parasite takes what it needs to survive, but the host doesn’t benefit.

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11
Q

What are some

abiotic factors that affect communities?

(non-living)

(4 factors)

A
  • temperature
  • amount of water
  • light intensity
  • levels of pollutants
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12
Q

What are some

biotic factors that affect communities?

(living)

(2 factors)

A
  • competition
  • predation
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13
Q

How do you

compare how common an organism is in two sample areas?

(6 steps)

A
  1. Place a quadrat on the ground at a random point within the first sample area.
  2. Count all the organisms you’re interested in within the quadrat.
  3. Repeat steps 1 and 2 lots of times.
  4. Work out the mean number of organisms per quadrat within the first sample area.
  5. Repeat steps 1 to 4 in the second sample area.
  6. Compare the two means.
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14
Q

Define

gradient.

(biology)

A

abiotic factors changing across a habitat

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15
Q

How do you

use a belt transect to study distribution along a gradient?

(practical)

(5 steps)

A
  1. Mark out a line in the area you want to study.
  2. Collect data along the line using quadrats placed next to eachother.
  3. You could also record other data, such as the mean height of the plants you’re counting or the abiotic factors in each quadrat.
  4. Repeat steps 1 and 2 several times, then find the mean number of organisms or mean percentage cover for each quadrat.
  5. Plot graphs to see if the changing abiotic factor is correlated with a change in the distribution of the species you’re studying.

If your transect is quite long, you could place the quadrats at regular intervals instead.
Collect data by counting all the organisms of the species you’re interested in, or by estimating percentage cover.

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16
Q

What is the formula for

the efficiency of energy transfer between levels of a food chain?

A

efficiency = (energy transferred to next level x 100) / energy available at previous level

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17
Q

Define

Biodiversity.

A

the variety of living organisms in an ecosystem

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18
Q

What are the steps for

eutrophication?

(5 steps)

A
  1. Fertilisers enter the water, adding excess nitrates (more than plants in the water can take in).
  2. The excess nitrates cause algae to grow fast and block out the light.
  3. Plants can’t photosynthesise due to lack of light and start to die and decompose.
  4. With more food available, microorganisms that feed on decomposing plants increase in number and use up oxygen in the water.
  5. Organisms that need oxygen for aerobic respiration (e.g. fish) die.

Pollution by sewage can allso cause this eutrophication

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19
Q

How can

fish farms in areas of open water reduce biodiversity in the surrounding area?

(4 steps)

A
  1. Food is added to the nets to feed the fish, which produce huge amounts of waste. Both the food and the waste can leak into the open water, causing eutrophication and the death of wild species.
  2. Fish farms in open water often act as a breeding ground for large numbers of parasites. These parasites can get out of 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.
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20
Q

Define

Non-indigenous species.

A

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

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21
Q

How can

the introduction of a non-indigenous species reduce biodiversity?

(2 ways)

A
  1. Non-indigenous species compete with indigenous species for resources like food and shelter. Sometimes, they are better at getting these resources and out-compete the indigenous species, which decrease in number and eventually die out.
  2. Non-indigenous species sometimes also brng new diseases to a habitat. These often infect and kill lots of indigenous species, reducing the habitat’s biodiversity.
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22
Q

Define

Reforestation.

A

when land where a forest previously stood is replanted to form a new forest

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23
Q

What are some

benefits to maintaining biodiversity?

(6 benefits)

A
  • protecting the human food supply
  • ensuring minimal damage to food chains
  • providing future medicines
  • cultural aspects
  • ecotourism
  • providing new jobs
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24
Q

Define

Food security.

A

Having access to enough food that is safe for us to eat and has the right balance of nutrition

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25
Q

Define

Yield.

A

the amount of useful product made

26
Q

Define

Sustainability.

A

meeting the needs of today’s population without affecting the ability of future generations to meet their needs.

27
Q

What are the 7 most important points about the

carbon cycle?

A
  1. There’s only one arrow going down from carbon dioxide in the air. The whole thing is ‘powered’ by photosynthesis. Plants use the carbon in carbon dioxide to make carbohydrates, fats and proteins.
  2. Eating passes the carbon compounds in the plant along to animals in a food chain.
  3. Both plant and animal respiration while the organisms are alive release carbon dioxide back into the air.
  4. Plants and animals eventually die and decompose, or are killed and turned into useful products.
  5. When plants and animals decompose they’re broken down by microorganisms, such as bacteria and fungi. These decomposers release carbon dioxide back into the air by respiration, as they break down the material.
  6. Some useful plant and animal products are burned (combustion). This also releases carbon dioxide back into the air.
  7. Decomposition of materials means that habitats can be maintained for the organisms that live there.
28
Q

What are the 4 steps to the

water cycle?

A
  1. Energy from the Sun makes water evaporate from the land and sea, turning it into water vapour. Water also evaporates from plants by transpiration.
  2. The warm water vapour is carried upwards (as warm air rises). When it gets higher up it cools and condenses to form clouds.
  3. Water falls from the clouds as precipitation onto land, where it provides fresh water for plants and animals.
  4. It then drains into the sea and the whole process starts again.
29
Q

Define

Desalination.

A

removing salts (mineral ions) from salt water

30
Q

Describe the process of

thermal desalination.

(3 steps)

A
  1. Salt water is boiled in a large enclosed vessel, so that the water evaporates.
  2. The steam rises to the top of the vessel, but the salts stay at the bottom.
  3. The steam then travels down a pipe from the top of the vessel and condenses back into pure water.
31
Q

Define

Osmosis.

A

The net movement of water across a partially permeable membrane, from an area of higher water potential to an area of lower water potential.

32
Q

What are the steps of

reverse osmosis?

(3 steps)

A
  1. Salt water is treated to remove 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.
  3. As the water is forced through the membrane, the salts are left behind, removing them from the water.
33
Q

Define

Nitrogen fixation.

A

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

34
Q

What are the two main ways of

nitrogen fixation?

A
  • lightning
  • nitrogen-fixing bacteria
35
Q

Why is nitrogen fixation necessary?

A

Nitrogen is needed for making proteins for growth, so living organisms have to get it somehow. However, nitrogen gas, N2, is very unreactive so can’t be used directly by plants or animals.

36
Q

What do decomposers do in the nitrogen cycle?

A

decompose proteins and urea and turn them into ammonia

ammonia forms ammonium ions in solution that plants can use

37
Q

What do nitrifying bacteria do in the nitrogen cycle?

A

turn ammonia in decaying matter into nitrites and then into nitrates

different species of nitrifying bacteria are responsible for producing nitrites and nitrates

38
Q

What do nitrogen-fixing bacteria do in the nitrogen cycle?

A

turn atmospheric N2 (from air pockets in the soil) into ammnoia, which forms ammonium ions

39
Q

What do denitrifying bacteria do in the nitrogen cycle?

A

turn nitrates back into N2 gas

this is of no benefit to living organisms, denitrifying bacteria are often found in waterlogged soils

40
Q

What are some ways for farmers to

increase the amount of nitrates in the soil?

(2 ways)

A
  • crop rotation
  • fertilisers
41
Q

What is

crop rotation?

A

different crops being grown each year in a field each year in a cycle

the cycle usually includes a nitrogen-fixing crop, which helps put nitrates back into the soil for another crop to use the following year

42
Q

Define

Indicator species.

A

organisms that are very sensitive to changes in their environment

43
Q

Why are indicator species helpful?

A

they can be studied to see the effect of human activities

44
Q

What would the presence of stonefly larvae signify?

(indicator species)

A

the water is clean

45
Q

What would the presence of freshwater shrimps signify?

(indicator species)

A

the water is clean

46
Q

What would the presence of blood worms signify?

(indicator species)

A

the water has a very high level of water pollution

47
Q

What would the presence of sludgeworms signify?

(indicator species)

A

the water has a very high level of water pollution

48
Q

What would the presence of bushy lichen or lots of lichen signify?

(indicator species)

A

the air is clean

(the concentration of sulfur dioxide in the atmosphere is low)

49
Q

What would the presence of crusty lichen signify?

(indicator species)

A

less clean air

(compared to bushy lichen)

50
Q

What would the presence of blackspot fungus on rose leaves signify?

(indicator species)

A

the air is clean

(the concentration of sulfur dioxide in the air is low)

51
Q

What is a more accurate way to measure the concentration of dissolved oxygen in the water (level of water pollution)?

(2 methods)

A

dissolved oxygen meter
chemical test

52
Q

What is a more accurate way to measure the concentration of sulfur dioxide in the air (level of air pollution)?

(2 methods)

A

electronic meter
laboratory test

53
Q

What 3 main things does the rate of decay depend on?

A
  • temperature
  • water content
  • oxygen availability
54
Q

How does temperature affect rate of decay?

A

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

55
Q

How does water content affect rate of decay?

A

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

56
Q

How does oxygen availability affect rate of decay?

A

the rate of decomposition is faster where there is plenty of oxygen available

57
Q

What are some methods of

food preservation to reduce the rate of decay?

(3 methods)

A
  • storing foods in a fridge or freezer
  • storing food in airtight cans
  • drying food
58
Q

How does storing foods in a fridge or freezer help food preservation?

A

it lowers the temperature of the food, this slows down the decomposers’ rate of reproduction

(or stops it altogether in the case if freezing)

59
Q

How does storing food in airtight cans help food preservation?

A

This stops the microorganisms getting in. Once the food is in, the cans are sealed and sterilised to kill any microorganisms present.

60
Q

How does drying food help food preservation?

A

it removes the water that microorganisms need to survive and reproduce

(as does adding salt or sugar, which causes the microorganisms to lose water by osmosis)

61
Q

Define

Compost.

A

decomposed organic matter that is used as a fertiliser for crops and garden plants

GCSE Edexcel Biology (10 decks)

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