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AQA A Level Biology flashcards > 7C - Populations in Ecosystems > Flashcards

7C - Populations in Ecosystems Flashcards

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1
Q

What is a habitat?

A

The place where an organism lives (e.g. rocky shore)

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2
Q

Give an example of a habitat.

A
  • Rocky shore

* Field

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3
Q

What is a population?

A

All the organisms of one species in a habitat.

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4
Q

What is a community?

A

Populations of different species in a habitat make up a community.

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5
Q

What is an ecosystem?

A

A community, plus all the abiotic conditions in the area in which it lives.

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6
Q

Are ecosystems small or large?

A

They can be both.

e.g. Small pond or large ocean

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7
Q

Explain the difference between an ecosystem and habitat.

CHECK

A

A habitat is simply the place in which an organism lives, while an ecosystem includes a community with all the abiotic factors associated with it.

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8
Q

Explain the difference between a population and a community.

A

A community is the collection of populations in a certain habitat.

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9
Q

What are abiotic conditions?

A

The non-living features of an ecosystem.

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10
Q

What are biotic conditions?

A

The living features of an ecosystem.

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11
Q

Give an example of an abiotic condition.

A
  • Temperature

* Availability of water

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12
Q

Give an example of a biotic condition.

A
  • Presence of predators

* Food

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13
Q

What is a niche?

A

The role of a species within its habitat.

eg. What, where and when it eats

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14
Q

What is an adaptation?

A

A feature that members of a species have that increases their chance of survival and reproduction.

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15
Q

What does a species’ niche include?

A
  • Biotic interactions (e.g. the organisms it eats and those it’s eaten by)
  • Abiotic interactions (e.g. the oxygen an organism breathes in and the CO2 it breathes out)
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16
Q

Can a niche be shared?

A
  • No, each species has a unique niche.

* It may appear as if two species are occupying the same niche, but there’ll be small differences, such as what they eat

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17
Q

What happens if two species try to occupy the same niche?

A
  • They compete with each other.

* Eventually, only one species is left

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18
Q

Give an example of a niche.

A

Common pipistrelle bat:
This bat lives throughout Britain on farmland, open woodland, hedgerows and urban areas. It feeds by flying and catching insects using echolocation at frequency of around 45 kHz.

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19
Q

Give an example of the differences in niche between…
• Common pipistrelle bat:
This bat lives throughout Britain on farmland, open woodland, hedgerows and urban areas. It feeds by flying and catching insects using echolocation at frequency of around 45 kHz.
• Soprano pipistrelle bat:
This bat lives in Britain in woodland areas, close to lakes or rivers. It feeds by flying and catching insects using echolocation at a frequency of around 55 kHz.

A

They use different frequencies for echolocation.

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20
Q

What are the 3 types of adaptation?

A
  • Physiological
  • Behavioural
  • Structural
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21
Q

What are physiological adaptations?

A

To do with processes inside the body.

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22
Q

What are behavioural adaptations?

A

To do with how an organism acts.

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23
Q

What are structural adaptations?

A

To do with structural features of the body.

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24
Q

Describe simply natural selection.

A

Organisms with better adaptations are more likely to survive, reproduce and pass on the alleles for their adaptations, so the adaptations become more common in the population.

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25
Q

Give an example of how a species uses an ecosystem like no other organism can (a niche).

A

Only giant anteaters can break into ant nests and reach the ants. They have claws to open the nest, and a long, sticky tongue which can rapidly move in and out of its mouth to pick up ants.

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26
Q

What two things are organisms adapted for?

A
  • Abiotic conditions

* Biotic conditions

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27
Q

Give some examples of adaptations to abiotic conditions.

A
  • Otters have webbed paws -> So they can walk on land and swim effectively.
  • Seals have a thick layer of blubber -> This helps to keep them warm in cold seas.
  • Hedgehogs hibernate -> This lowers their metabolic rate over winter, conserving energy.
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28
Q

Give some examples of adaptations for biotic conditions.

A
  • Sea otters use rocks to smash open shellfish and clams -> This gives them access to another food source.
  • Male frogs produce mating calls -> This helps attract a mate of the same species, making reproduction more successful.
  • Some bacteria produce antibiotics -> To kill other bacterial species in the area, reducing competition.
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29
Q

What is population size?

A

The total number of organisms of one species in a habitat.

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30
Q

What is carrying capacity?

A

The maximum stable population size of a species that an ecosystem can support.

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31
Q

What affects the carrying capacity of an ecosystem?

A

The abiotic and biotic factors.

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32
Q

Give some examples of abiotic factors that affect the carrying capacity of an ecosystem.

A
  • Light
  • Water
  • Space
  • Temperature
  • Chemical composition of surroundings
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33
Q

Explain how the temperature of an ecosystem affects the carrying capacity.

A
  • When the temperature of a mammal’s surroundings is ideal for metabolic reactions to take place, less energy has to be used up by the body maintaining the body temperature.
  • This means more energy can be used for growth and reproduction, so the population size increases.
  • The opposite is also true.
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34
Q

Name the three ways in which biotic factors can affect the carrying capacity of an ecosystem.

A

1) Interspecific competition -> Competition between species
2) Intraspecific competition -> Competition within a species
3) Predation

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35
Q

What is the name for competition between species?

A

Interspecific competition

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36
Q

What is the name for competition within a species?

A

Intraspecific competition

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37
Q

What is interspecific competition?

A

When organisms of different species compete with each other for the same resources.

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38
Q

Give an example of interspecific competition.

A

Red and grey squirrels compete for the same food sources and habitats.

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39
Q

How does interspecific competition affect the population size of two species?

A

EITHER:
• Both populations reduced -> Since the resources available to each species are reduced
OR
• One species is out-competed -> If one species is better adapted than the other, then the second species is out-competed and cannot survive there

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40
Q

Give an example of interspecific competition reducing population size of both species.

A

In an area where both red and grey squirrels exist, the numbers of each species are lower than if only one species were to exist there.

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41
Q

Give an example of interspecific competition causing one of the two species to be out-competed.

A

Grey squirrels out-competed red squirrels in the UK, since they are larger and can store more fat over winter. They can also eat a wider range of food.

42
Q

How does intraspecific competition affect population size?

A

1) When resources are plentiful, the population thrives and rises above the carrying capacity. This increases competition.
2) This depletes the resources and there is not enough food and space for all the organisms.
3) So the population declines below the carrying capacity, which reduces the competition for food and space. This means growth and reproduction are once again favoured and so the cycle starts again.
(See diagram pg 184 of revision guide)

43
Q

What is predation?

A

Where an organism kills and eats another organism.

44
Q

What can be said about the population sizes of predators and prey?

A

They are interlinked.

45
Q

How does predation affect population size?

A

1) As prey population increases, there’s more food for predators, so the predator population grows along with the prey population.
2) This means more prey is eaten, so the prey population soon starts to fall.
3) This means there’s less food for the predator, so their population decreases. The process repeats.
(See diagram pg 185 of revision guide)

46
Q

Why is a sample taken?

A

It is too time-consuming to measure the entire area.

47
Q

Describe how to take a random sample to investigate an area.

A

1) Choose an area to sample (within a larger area).
2) Choose an appropriate sampling method, depending on whether the organisms are motile or non-motile.
3) Take random samples.
4) Repeat process to reduce the likelihood that results are due to chance.
5) Use data to draw conclusions about the whole area.

48
Q

What sampling methods can be used to investigate non-motile organisms?

A
  • Quadrats

* Transects

49
Q

What sampling methods can be used to investigate motile organisms?

A

Mark-Release-Recapture

50
Q

What are non-motile organisms?

A

Ones which do not move around

51
Q

What are motile organisms?

A

Ones that move around

52
Q

Describe how a quadrat can be used to investigate non-motile organisms.

A

1) Use a method, such as a random number sheet, to generate a series of random co-ordinates in the area.
2) Place two tape measures at right-angles to create the axis along which sampling will take place.
3) Place quadrats at different points in the area.
4) The number of individuals of a species or the percentage cover of a species in each quadrat can be measured. For percentage cover, a square is covered if it is more than half-covered.

53
Q

What are transects used for?

A

To investigate how organisms are distributed across an area.

54
Q

Describe the two types of transect.

A
  • Belt transect - Quadrats are placed next to each other along the transect.
  • Interrupted belt transects - Quadrats are placed at intervals along the transect (to cover larger distances).
55
Q

Describe how mark-release-recapture can be used to investigate motile species.

A

1) Capture a sample of species using an appropriate technique and count them.
2) Mark them in a harmless way.
3) Release them back into the habitat.
4) Wait a week, then take a second sample from the same population.
5) Count the number of the second sample that are marked.
6) Use the equation:
Total population size = No. in 1st sample x No. in 2nd sample / No. marked in 2nd sample

56
Q

What is the equation for population size in mark-release-recapture?

A

Total population size = No. in 1st sample x No. in 2nd sample / No. marked in 2nd sample

57
Q

What are some assumptions of the mark-release-recapture method?

A

1) Marked sample has had enough time and opportunity to mix back in with the population
2) Marking hasn’t affected the chances of survival
3) Marking is still visible
4) No births, deaths or migration

58
Q

Describe how you could investigate the effect of soil pH on marram grass distribution in a coastal ecosystem.

A

1) Place a tape measure in a straight line from the shore, heading inland. This is the transect.
2) Take 1m2 quadrat divided into 100 squares.
3) Starting from the shore, place the quadrat next to the tape measure.
4) Count the squares containing marram grass and record the results as percentage cover.
5) At each sample point, also measure the pH.
6) Repeat every 10m along the transect.
7) Plot a graph of percentage cover and pH against distance from shore (i.e. have 2 y-axis) to deduce any relationship.

59
Q

How can you measure the pH of soil?

A

• Use a digital pH probe
OR
• Add barium sulphate, distilled water and pH indicator.

60
Q

How does pH change with distance from the shore?

A

It decreases, because:
• Soil/sand nearer the sea has many more shell fragments made of alkaline calcium carbonate.
• Soil/sand away from the sea has more rotting vegetation which is more acidic.

61
Q

Looking at the graph on pg 187, why can you not draw conclusions about the relationship between pH and marram grass distribution?

A

There may be other confounding factors, such as soil moisture content, salinity and completion from other species.

62
Q

What are some types of issues that need to be considered when doing a population investigation?

A
  • Safety

* Ethical

63
Q

What are some safety issues and prevention techniques in the investigation of the effect of pH on marram grass distribution?

A
  • Tides -> Use tide timetables
  • Slipping -> Wear suitable clothing and footwear for the weather and terrain
  • Chemicals -> Wash your hands before eating, especially after handling soil
64
Q

What are some ethical issues and prevention techniques in the investigation of the effect of pH on marram grass distribution?

A
  • All fieldwork affects the environment where it’s carried out (e.g. lots of people walking may cause soil erosion)
  • Investigations should be planned to minimise these (e.g. people should restrict where they walk to the area being studied)
65
Q

What is succession?

A

The process by which an ecosystem changes over time.

66
Q

What word can be used to describe ecosystems?

A

Dynamic

67
Q

The biotic conditions in an ecosystem change as…

A

…the abiotic conditions change.

68
Q

What are the two types of succession?

A
  • Primary

* Secondary

69
Q

What is primary succession?

A
  • Succession that happens on land that’s been newly formed or exposed.
  • There’s no soil or organic material.
70
Q

What is secondary succession?

A
  • Succession that happens on land that’s been cleared of all plants.
  • Soil remains.
71
Q

Give an example of primary succession.

A

Where sea level has dropped, exposing a new area of land.

72
Q

Give an example of secondary succession.

A

Where an area of forest has been cut down by humans.

73
Q

Describe the process of primary succession.

A
  • At first the conditions are hostile.
  • A pioneer species colonises the area when wind blows seeds or spores.
  • When these die and are decomposed by microorganisms, they change the abiotic conditions by forming a basic soil from humus. This can retain water.
  • This makes the conditions less hostile so new organisms with different adaptations can move in and grow.
  • When these die and decompose, they make the soil deeper and richer in minerals. It can retain more water.
  • Larger plants like shrubs can start to grow in the deeper soil.
  • Some species may change the environment so that it is less suitable for previous species. They can also outcompete the previous species, becoming the new dominant species.
  • Over time, biodiversity increases until a climax community is reached.
74
Q

What is the first species to colonise an area called?

A

Pioneer species

75
Q

In succession, what changes first at each stage, the biotic or abiotic conditions?

A

Abiotic

76
Q

Give an example of a pioneer species.

A

Marram grass

77
Q

What is humus?

A

Dead organic material

78
Q

Give an example of when a more advanced species in succession changes the conditions to be less favourable to earlier species.

A

Sand sedge stabilises the sand through growth of rhizomes (underground stems), which makes the conditions less suitable for marram grass.

79
Q

Describe the process of secondary succession.

A

It is just like primary succession except there is already a soil layer and so the pioneer species are larger plants.

80
Q

How does biodiversity change throughout succession?

A

It increases until a climax community is reached.

81
Q

What is the final stage of succession called?

A

Climax community

82
Q

Describe succession to form woodland.

A
  • Pioneer species colonise the rocks e.g. lichens grow on and break down rocks
  • Lichen die and are decomposed to form a thin soil, which thickens and allows other species such as mosses to grow.
  • Larger plants that need more water can move in as the soil depends e.g. grasses and small flowering plants
  • Soil continues to deepen, and shrubs, ferns and small trees begin to grow, out-competing the grasses and smaller plants to become the dominant species.
  • Diversity increases
  • Finally, the soil is deep and rich enough in nutrients to support large trees. These become the dominant species and the climax community is formed.
83
Q

Do all ecosystems have the same climax community?

A

No, it depends on the climate.

84
Q

What is the name for the type of climax community in an ecosystem?

A

Climatic climax

85
Q

Explain the climatic climax in a temperature climate.

A
  • There’s plenty of available water, mild temperatures and not that much change between seasons.
  • Climatic climax will contain large trees because they can grow in these conditions.
86
Q

Explain the climatic climax in a polar climate.

A
  • There’s not much available water, low temperatures and massive changes between seasons.
  • Climatic climax will contain only herbs or shrubs because trees can’t grow in these conditions.
87
Q

What is the name for the climax community when succession is stopped by human activity?

A

Plagioclimax

88
Q

Give an example of a plagioclimax.

A

Frequently mowing a lawn prevents large shrubs and trees growing, since their growing points are cut off. The plagioclimax only contains grass.

89
Q

Describe how conservation may involve preventing succession.

A

Preventing succession can maintain an ecosystem in a desired stage of succession.

90
Q

Give an example of conservation by preventing succession.

A

Moorlands in Scotland provide habitats for many species of plant and animal. If succession was allowed to happen, a climax community of spruce forest would form, causing the loss of this important habitat for many species. So succession is prevented.

91
Q

Give two ways of preventing succession in a moorland ecosystem.

A

1) Animal grazing

2) Managed fires

92
Q

What happens after managed fires are lit to prevent succession?

A
  • Pioneer species quickly grow back.

* Larger species take longer to grow back and will be removed again next time the moor is burnt.

93
Q

What is conservation?

A

The protection and management of species and habitats in a sustainable way.

94
Q

What does sustainable mean?

A

When enough resources are taken to meet the needs of people today, without reducing the ability of people in the future to meet their own needs.

95
Q

What does conservation often have a conflict with?

A

Human interest

96
Q

Give an example of balancing conservation and human interest.

A
  • The Maasai Mara is a national reserve in Kenya. It is a large area of grassland.
  • Maasai people traditionally earn a living by raising livestock, which can bring them into conflict with conservationists due to overgrazing.
  • Conservation trusts work with the Maasai to help them make money from their land through conservation and ecotourism, and to farm in a sustainable way.
97
Q

What are the two possible focuses of conservation?

A
  • Conserving a particular species

* Conserving a habitat for the species that live there

98
Q

Give some examples of conservation techniques.

A
  • Seedbanks
  • Fishing quotas
  • Protected area that restrict urban development, industrial development and farming
  • Breeding endangered species in captivity
99
Q

Remember to practice evaluating evidence about conservation issues.

A

Example on pgs 190 and 191 of revision guide

100
Q

What can you look at when two different studies about conservation reach conflicting conclusions?

A

Evaluate the methods of each to see which is more likely to be accurate and reliable.

AQA A Level Biology flashcards (19 decks)

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