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A-Level Biology A2 > Populations In Ecosystems > Flashcards

Populations In Ecosystems Flashcards

1
Q

Definition of a habitat

A

The place where an organism lives within an ecosystem

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2
Q

Definition of population

A

A group of organisms of the same species living in a particular area at a particular time that can potentially interbreed to produce fertile offspring.

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3
Q

Definition of a community

A

Populations of different species in a habitat make up a community

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4
Q

Definition of an Ecosystem

A

A community, plus all the non-living conditions in the area in which it lives. Ecosystems can be small or large.

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5
Q

Definition of abiotic conditions

A

The non-living features of the ecosystem i.e. temp, water availability

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6
Q

Definition of biotic conditions

A

The living features of the ecosystem i.e. predators or food

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7
Q

Definition of a Niche

A

The role of a species within its habitat, i.e. what it eats, where and when it feeds.

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8
Q

Definition of adaptations

A

A feature that members of a species have that increases their chance of survival and reproduction, i.e. giraffes have long necks to help them reach vegetation that’s high up increasing chance of survival.

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9
Q

What does every species occupy?

A

A different niche

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10
Q

What would happen if two species try to occupy the same niche?

A

They will compete with each other and one will be more successful until one of the species is left.

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11
Q

What is competitive exclusion

A

Same species appear similar but two can’t successfully occupy the same niche.

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12
Q

What do niches include

A

biotic and abiotic conditions

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13
Q

Give examples of features of adaptations

A
  1. physiological
  2. behavioural
  3. anatominal
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14
Q

Organisms with better adaptations are more likely to:

A
  • survive
  • reproduce
  • pass on advantageous alleles
  • increasing frequency of them alleles in population
  • adaptations more common
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15
Q

what does it mean when it says a species has its own unique niche?

A

Every species is adapted to use an ecosystem in a way that no other species can

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16
Q

Give examples of how organisms are adapted to abiotic conditions

A
  • Otters have webbed paws - means they can both walk on land and swim effectively. That increases chance of survival because they can live and hunt both on land and in water.
  • Seals have a thick layer of blubber/ fat - helps keep them warm in cold seas, increasing survival as can live in places where food plentiful.
  • Hedgehogs hibernate - lowers their metabolism over winter, increases chance of survival as conserve energy during coldest months.
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17
Q

Give examples of how organisms are adapted to biotic conditions

A
  • Sea otters use rocks to smash open clams and shellfish, increasing chance of survival as gives them access to another source of food.
  • Male frogs produce mating calls to attract females - makes sure they attract a mate of the same species - sucessful mating.
  • Some bacteria produce antibiotics - kill other species of bacteria in the same area, increasing their chance of survival as less competitive for resources.
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18
Q

Difference between habitat and niche

A

Habitat = Where a species lives

Niche = What it does in its habitats

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19
Q

What is carrying capacity?

A

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

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20
Q

What is population size?

A

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

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21
Q

What do abiotic factors include?

A

light

water

space

temperature

chemical composition

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22
Q

What happens when abiotic conditions aren’t ideal?

A

organisms can’t grow as fast, or reproduce as successfully.

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23
Q

Why do population sizes vary?

A

Because of abiotic and biotic factors

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24
Q

What are a part of biotic factors

A
  1. Interspecific competition
  2. Intraspecific competition
  3. Predation
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25
Q

What is interspecific competition?

// What will be the effect of interspecific competition on the population size of a species?

A
  • Competition between different species for same resources - different species compete with each other.
  • resources availability reduced.
  • both populations limited by lower food and so less energy for growth and reproduction.
  • population size lower doe both species.
  • if two species are competing but ones better adaprted to surroundings then less well adapted = outcompeted.
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26
Q

What is intraspecific?

A
  • Competition within a species.
  • When competition of the same species compete with each other for the same resources.
  • It can cause a cyclical change in population size around ecosystems carrying capacity.
  • The population of a species increases when resources plentiful = more competition for same amount of space or food.
  • The space/ food is limited - isn’t enough for all the organisms so population starts to decline.
  • a smaller population means there’s less competition for space and food which is better for growth and reproduction - so population starts to grow again.
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27
Q

What is predation?

A
  • Where an organism kills and eats another organism.
  • The population sizes of predators and prey are interlinked - as the population of one changes, the population of another changes.
  • As prey increases = more food for predator so increase in predators.
  • as predator increases, more prey eaten and so prey population decreases.
  • as prey population decreases = less food for predators so predators decrease.
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28
Q

What causes complications between the predator-prey relationships?

A

there’s other factors involved i.e. food availability for prey.

i.e. it’s thought that the population of a prey begins to decline because there’s too many of them for the amount of food available but it is then accelerated by predation from the lynx.

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29
Q

How would you investigate a population?

A

Take random samples from an area

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30
Q

Suggest appropriate units for gross productivity.

A

Unit of energy / mass, per area, per year.

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31
Q

What is meant by uniformly distributed?

A

Same number (of organisms) in each region / (organisms) equally spread;

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32
Q

How do the assumptions made in proportional sampling differ from those made in mark-release-recapture? (2)

A

In mark–release-recapture (technique)

  1. No assumption that organisms are uniformly distributed;
  2. Size of total area / size of sampled region not required;
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33
Q

What’s the problem with measuring number of individuals in a species and the distrubition of that species in the entire area?

A

It’s very time consuming.

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34
Q

Explain how you take samples

A
  1. Choose an area to sample - a small area
  2. Should be random to avoid bias = i.e. random generator to select coordinations
  3. Use an appropiate technique
  4. Repeat process - reduce chance likelihood
  5. The number of individuals for the whole area can be estimated by a mean of the data and multiplying it by size of whole area
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35
Q

What does abundance mean

A

The number of individuals of one species in a particular area

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36
Q

What are measures of abundance taken

A
  1. freq. = number of samples of a species measured in
  2. percentage cover = how much of the area you’re investigating is covered by a species
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37
Q

What are used to investigate non-motile organisms?

A

Quadrats and transects

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38
Q

What are non-motile organisms

A

They dont move - like plants

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39
Q

Three ways to measure population in a investigation

A
  1. quadrats
  2. transects
  3. capturing motile organisms
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40
Q

Describe how you could use a quadrat to measure number of individuals

A
  1. Square frame, divided into a grid of 100 smaller squares
  2. placed on ground at different points
  3. the species frequency or number of individuals of each is recorded in each quadrat
  4. count a square if more than half covered - can measure the percentage cover
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41
Q

Why is it good to measure the percentage cover

A

Quick easy way to investigate populations

dont have to count all

42
Q

How would you find out plants are distributed across an area?

A

use a transect line

  1. belt transects = quadrats based next to each other along the transect line to work out species frequency and percentage cover.
  2. interrupted belt transects = measurements to cover a larger distance, quadrats placed at intervals along line
43
Q

Explain the mark-release-recapture method

A
  1. capture of a sample of species using appropriate technique
  2. mark them in a harmless way (spot of paint)
  3. release them back into their habitat
  4. wait a week, take second sample from same population
  5. count how many in second are marked.
  6. use the equation to estimate total population size
  7. number caught in first x number caught in second / number marked in second
44
Q

What do you have to make sure of if using the mark release recapture method

A
  1. the marked sample has had enough time and opportunity to mix
  2. the mark hasn’t affected chance of survival (could be visible to predators)
  3. doesn’t cause distress on species
  4. there are no changes in the population size due t births, deaths and migration
45
Q

When do you know when you have a realistic estimate

A

when the mean no longer changes

46
Q

What often changes within a particular area?

A

The distribution of species

47
Q

What are examples of environmental factors

A

Shade, pH

48
Q

How would you investigate the effect of soil pH

A
  1. place a tape measure in a straight line = transect
  2. take a 1 m2 quadrat divided into 100 squares
  3. start from shore, place quadrat next to tape measure
  4. count the squares containing the species i.e. marram grass and record results in a table as a percentage cover
  5. at each sample point you should measure the pH and record results in a table
  6. repeat observation every 10 m along the transect
49
Q

How can you measure the pH?

A
  • Digital pH probe

or

  • take sample back to school if don’t have one and use a sieve to remove any debris and add some barium sulfate, distilled water and pH indicator.
  • shake thoroughly and leave it to settle.
  • check against a pH chart and record results
50
Q

What are safety issues/ how to reduce risks when investigating outside/ effect of something

A
  1. known the local tide times - low tide is best
  2. wear suitable clothing and footwear for the weather and terrain
  3. wash your hands before eating, especially after handelling soil
51
Q

What are ethical issues?

how to avoid them?

A
  1. people walking around can cause soil erosion
  2. marram grass can be killed by people trampling over it

investigations should be planned to have the smallest impact possible

  1. people should restrict where they walk to the area being studied
  2. try to avoid treading on the plants
52
Q

Ecosystems are known as what?

A

dynamic

53
Q

why are ecosystems known as dynamic?

A

because they are constantly changing

54
Q

What is the definition of succession?

A

The process by which an ecosystem changes over time.

//The changes, over time, in the species that occupy a particular area.

55
Q

As the abiotic conditions change the ____ change

A

biotic

56
Q

What are the two types of succession?

A

Primary succession

Secondary succession

57
Q

What is primary succession?

A

It happens on land that’s been newely formed or exposed i.e. where a volcano has erupted to form a new rock surface or where sea levels have dropped exposing new area of land.

There’s no soil or organic material to start off with

58
Q

What is secondary succession?

A

happens on land that’s been cleared of all the plants, but where the soil remains i.e. after a forest fire or where a forest has been cut down by humans.

59
Q

Explain the process/ stages of succession

A
  1. Primary succession - when species colonise a new land surface. Seeds and spores are blown in by the wind and begin to grow = pioneer species.
  2. Abiotic conditions are hostile i.e. there’s no soil to retain water. The pioneer species only grow due to being specially adapted to cope.
  3. The pioneer species change the abiotic conditions - they die and microorganisms decompose the dead organic material, forming basic soil.
  4. This makes conditions less hostile so new organisms with different adaptations grow as basic soil helps retain water and they then die and decompose adding more organic material, making soil deeper, retaining more water.
  5. Some new species change environment so becomes less suitable for previous, = less suitable conditions.
  6. Secondary succession = pioneer species larger plants as soil layer already starts succession.
  7. At each stage, diff species better adapted so outcompete ones already there = become dominant species.
  8. Ecosystem becomes more complex and new species move in alongside exisitng = incrreases biodiversity.
  9. Final stage is the climax community = ecosystem is supporting largest and most complex community. It won’t change = steady state.
60
Q

What are pioneer species?

A

The first species to colonise the area

61
Q

Explain the pioneer stage of succession

A
  1. Primary succession - when species colonise a new land surface. Seeds and spores are blown in by the wind and begin to grow = pioneer species.
  2. Abiotic conditions are hostile i.e. there’s no soil to retain water. The pioneer species only grow due to being specially adapted to cope.
62
Q

What is the final stage of succession?

A

climax community

63
Q

What’s the definition of cliamx community?

A

ecosystem is supporting largest and most complex community. It won’t change as in steady state.

64
Q

Explain in detail primary succession

A
  1. Primary succession - when species colonise a new land surface. Seeds and spores are blown in by the wind and begin to grow = pioneer species.
  2. Abiotic conditions are hostile i.e. there’s no soil to retain water. The pioneer species only grow due to being specially adapted to cope.
  3. The pioneer species change the abiotic conditions - they die and microorganisms decompose the dead organic material, forming basic soil.
  4. This makes conditions less hostile so new organisms with different adaptations grow as basic soil helps retain water and they then die and decompose adding more organic material, making soil deeper, retaining more water.
  5. Some new species change environment so becomes less suitable for previous, = less suitable conditions.
65
Q

Explain in more detail secondary succession

A

Secondary succession = pioneer species larger plants as soil layer already starts succession.

66
Q

Using the example of bare rock to woodland, explain primary succession

A
  1. Pioneer species colonise the rocks i.e. lichens grow on and break down rocks, releasing minerals
  2. The lichens die and are decomposed forming thin soil (thickens as more organic material is formed). Means other species can grow.
  3. Larger plants that need more water can move in as soil deepens i.e. grasses and small flowers. The soil continues to deepen as larger plants die and are decomposed.
  4. Shrubs, ferns and small tress begin to grow, out-competing the grasses and smaller plants to become the dominant species.
  5. Diveristy increases.
  6. The soil is then deep and rich with nutrients to support larger trees. That becomes the dominant species and the climax community is formed.
67
Q

What do different ecosystems have?

A

different climax communities

68
Q

What determines which species makes up the climax community?

A

What the climate is like in an ecosystem.

69
Q

What is a climatic climax?

A

The climax community for a particular climate

70
Q

Give examples of climatic climax

A
  1. In a temperature climate there’s plenty of available water, mild temperature and not much change between the seasons. The climatic climax will contain large trees because they can grow in these conditions once deep soils have developed.
  2. In a polar climate there’s not much available water, temperatures are low and there are big changes between the seasons. Large trees won’t be able to grow in these conditions so the climatic complex contains only herbs or shrubs but it’s still climax community.
71
Q

Changes that organisms produce in their abiotic environment can result in

A

a less hostile environment and change biodiversity.

72
Q

What does conservation of habitats frequently involve

A

Conservation of habitats frequently involves management of succession.

73
Q

What can prevent succession?

A

Human activites

74
Q

If succession stops what does that lead to?

A

It ends up stopping the climax community from developing.

75
Q

What is the climax community called when succession is stopped artifically?

A

Plagioclimax

76
Q

Definition of lagioclimax

A

The name given to the climax community when succession is artficially stopped

77
Q

Give an example of Plagioclimax

A

A regularly mown field won’t develop shrubs and trees even if ecosystem climate can be supported as the growing points are cut off by the lawnmower, so larger plants aren’t established.

The longer the interval between moving, the more frequent mowing, succession can’t progress and diversity will be lower.

78
Q

What does conservation involve?

A

preventing succession in order to preserve an ecosystem in its current stage of succession.

79
Q

Give an example of how/why conservation involves preventing succession in order to preserve an ecosystem in its current stage of succession

A

There are large areas of moorland that provides habitats for many species of plants and animals.

If the moorland was left to natural processes, succession would lead to a climax community of spruce forest meaning loss of moorland habitat and could lead to loss of some plants and animals currently living there.

Preventing succession keeps the moorlands ecosystem intact.

80
Q

What are 2 ways to manage succession to converse a moorland?

A
  1. Animals are allowed to graze on the land. This is simliar to mowing - the animals eat the growing points of the shrubs and tress, which stops them from establishing themselves and helps to keep vegetation low.
  2. Managed fires are lit. After the fires, secondary succession will occur on the moorland - the species that grow back first are the species that are being conserved. Larger species will take longer to grow back and will be removed again next time the moor is burnt.
81
Q

What is meant by climax community?

A

the final stage of succession, remaining unchanged until destroyed by an event such as fire or human interference.

82
Q

What is the definition of conservation?

A

the protection and management of species and habitats in a sustainable way

83
Q

What does sustainable mean?

A

That 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

84
Q

Why is careful management needed?

A

To find a balance between two and maintain the sustainability of natural resources

85
Q

Give an example of careful management

A
  • The maasai mara is in kenya = large area of grass land
  • The people traditionally earn a living by raising livestock such as cattle.
  • This can bring them into conflict with conservationists.
  • Conservation trusts are working with the Maasai to help them make money from their land through conservation and ecotourism projects rather than farming and to farm in a sustainable way
86
Q

What are different methods of conservation?

A
  1. Seedbanks - stores a lot of seeds from lots of different plant species. If the plants become extinct in the wild, the stored seeds can be used ti grow new plants. It’s a good way of conserving stored seeds in large numbers and in small spaces anywhere for a long period of time if cool and dry.
  2. Fishing quotas - Limits amount of certain fish species that fishermen are allowed to catch. Help conserve fish species by reducing the numbers that are caught and killed.
  3. Protected areas - national parks and nature reserves protect habitats by restricting urban development, industrial development and farming.
  4. Endangered species - can be bred in captivity to increase their numbers then returned back to wild. Good as help increase endangered species number.
87
Q

What are the problems with the different methods of conservation?

A
  1. Seedbanks - need to be regularly tested.
  2. Fishing quotas - unpopular with fishermen as limit potential income. Also problems with ‘discards’ - catching more fish than allowed and throwing them dead back into the sea so don’t exceed quota.
  3. Protected areas - National parks are used as tourist destinations so conflict between need to conserve habitats and visits needs.
  4. Captive breeding - reintroducing animals bred in captivity could cause problem as new diseases to habitats could develop, harming other species living there.
88
Q

If studies came to the same conclusion, the conclusion would become…

A

increasingly accepted.

89
Q

Use your knowledge of succession to explain the increase in biomass during the first 20 years. (3)

A
  1. Pioneer species;
  2. Change in abiotic conditions / less
    hostile / more habitats/niches;
  3. Increase in number/amount/diversity
    of species/plants/animals;
90
Q

Marram grass is a pioneer species that grows on sand dunes. It has long roots and a
vertically growing stem that grows up through the sand.
Sand dunes are easily damaged by visitors and are blown by the wind. Planting marram grass is useful in helping sand dune ecosystems to recover from damage.

Use your knowledge of succession to explain how. (2)

A
  1. Stabilises sand / stops sand
    shifting;
  2. Forms/improves soil / makes
    conditions less hostile;
91
Q

Farmland previously used for growing crops was left for 30 years and developed into
woodland. During this period, ecologists recorded an increase in the diversity of
birds in the area.

Name the process that resulted in the development of woodland from farmland. (1)

Explain the increase in the diversity of birds as the woodland developed.(3)

A

Succession;

  1. Greater variety/diversity of plants/insects / more
    plant/insect species;
  2. More food sources / more varieties of food;
  3. Greater variety/more habitats/niches;
92
Q

Succession process (5)

A
  1. Pioneer species colonises
  2. Makes abiotic conditions less hostile
  3. New species outcompetes pioneer species because better competitor
  4. New species increase in number, pioneer species decrease in number.
  5. Climax community established
    = the organisms that make up the final stage of ecological succession
    - normally has one dominant plant species, one dominant animal species
93
Q

5 features following succession?

A
  • Abiotic conditions less hostile/more habitats/more niches
  • Increased biodiversity
  • More complex food webs
  • Increased biomass
  • Increased stability
94
Q

The population of trees in the forest evolved adaptations to the mountain environment.

Use your knowldge of selection to explain how.

A
  • Variation in orgiginal colonisers.
  • Causing allele frequency to increase.
  • Some better adapted for survival.
  • Greater reproductive success.
95
Q

The scientists used percentage cover rather than frequency to record the abundance of algae present. Suggest why.

A

Difficult to count individual organisms.

96
Q

Explain why bog is decribed as the climax community

A

Stable community.

97
Q

Suggest why trees are unable to survive in waterllogged soils.

A

Roots unable to respire aerobically

active transport of minerals

98
Q

The water and soil in sphagnum bogs are usually acidic. Suggest why sphagnum is not fully decomposed after it dies.

A
  • fewer decomposers
  • H+ ions affect active sites
  • Anaerobic conditions
99
Q

Explain what limits the size of populations in a climax community

A

Nutrients

change in abiotic factors

competition in some area for limited resources

diseases killing species

predators

space for niche

light intensity

100
Q

Give two features of a climax community

A
  1. populations and community stable around carrying capacity.
  2. abiotic factors constant over time.
101
Q
A

A-Level Biology A2 (11 decks)

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