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Biology A-Level > Populations in Ecosystems > Flashcards

Populations in Ecosystems Flashcards

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1
Q

Define habitat

A

Place where an organism lives

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2
Q

Define population

A

Group of individuals of same species living in particular habitat + able to interbreed

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3
Q

Define community

A

Populations of diff species in a habitat

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4
Q

Define ecosystems

A

Self contained area made up of living + all the non-living factors

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5
Q

Define abiotic conditions

A

Non-living fts of the ecosystem

Eg. temp + water availability

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6
Q

Define biotic conditions

A

Living fts of the ecosystem

Eg. predators + food

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7
Q

Define niche

A

Roles of a species w/in its habitat

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8
Q

Why can a niche only be occupied by 1 species?

A

Bc the 2 species will compete until only 1 is left

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9
Q

Do 2 species ever occupy the same niche?

A
  • No
  • Own unique niche
  • Look similar but have slight differences eg. what they eat
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10
Q

Define adaptations

A

Fts that inc chances of survival + reproduction

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11
Q

Adaptations can be:

A
  • Physiological
  • Behavioural
  • Anatomical
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12
Q

Give eg. of organisms adapting to abiotic conditions

A
  • Otters : webbed feet - can hunt + live on land + water
  • Seals : thick layer of blubber - keep warm
  • Hedgehogs : hibernate - lower rate of metabolism
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13
Q

Give eg. of organisms adapting to biotic conditions

A
  • Sea otter : use rocks to smash shellfish
  • Male frogs : produce mating calls
  • Bacteria : produce antibiotics, kills other bacteria
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14
Q

Define population size

A

Total no. of organisms of 1 species in a habitat

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15
Q

Define carrying capacity

A

Max stable population size of a species that an ecosystem can support

Varies as result of abiotic + biotic factors

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16
Q

Give examples of abiotic factors that affect the population size

A
  • Amount of light, water + space available
  • Temp
  • Chemical composition of env
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17
Q

What happens to the population size when the abiotic conditions are ideal?

A
  • Inc
  • Eg. ideal temp for metabolic reactions, don’t use up much energy maintaining body temp. More energy for growth + reproduction
18
Q

Give examples of biotic factors that affect the population size

A
  • Interspecific competition - btw diff species
  • Intraspecific competition - w/in species
  • Predation
19
Q

Outline interspecific competition as a factor affecting population size

A
  • Btw diff. species for same resources
  • Resources available to both pop is reduced - both pop limited by lower amount of food. Less energy for growth + reproduction so population size dec
  • If 1 better adapted, likely to out-compete other species
20
Q

Outline intraspecific competition as a factor affecting population size

A
  • Same species compete for same resources
  • Pop inc when resources is plentiful, as pop inc, more organisms competing for same food + space
  • Resources become limiting - not enough so pop dec
  • Smaller pop means less comp for food + space, better for growth + reproduction - pop inc
21
Q

Outline predation as a factor affecting population size

A
  • Pop size of predators + preys are interlinked
  • As prey pop inc, more food for predators so pop inc
  • As predator pop inc, more prey eaten so prey pop fall
  • Less food for predator so pop dec
22
Q

Outline how to carry out a random sample

A
  • Choose an area to sample - set up tape measure
  • Use random no. generator to generate coordinates - avoid bias
  • Repeat to reduce likelihood that results are due to chance
  • Estimate by multiplying mean by area size
23
Q

Define non-motile organisms

A

Organisms that don’t move - plants

24
Q

What is used to investigate non-motile/slow organisms?

A
  • Quadrats
  • Transects
25
Q

Describe how you would use a quadrat to investigate non-motile organisms

A
  • Set up tape measure
  • Using random no. generator, generate co-ordinates
  • Place quadrat at co-ordinates
  • Species freq: count no. diff species in each quadrat
  • Percentage coverage : count how much of quadrat is covered - quicker
26
Q

When are transects used?

A

Find how plants are distributed across an area

27
Q

What are diff types of transects?

A
  • Belt transect: quadrat placed next to each other
  • Interrupted belt transect: quadrat placed at regular intervals (cover longer distance)
28
Q

Describe how you would use a transect to investigate non-motile organisms across an area (4)

A
  • Lay tape
  • Take samples at regular intervals
  • Using quadrat
  • Count no/percentage coverage
  • Use several transects
29
Q

What is used to investigate motile organisms?

A

Mark-Release-Recapture

30
Q

Outline how to carry out mark-release-recapture to investigate motile organisms

A
  • Capture sample + count
  • Mark them in harmless way
  • Release
  • Wait until re-intergrate, take 2nd sample from same pop
  • Count how many are marked
  • Use equation :

Total pop = no. 1st sample x no. 2nd sample / no. marked 2nd sample

31
Q

Outline the assumptions when carrying out mark-release-recapture

A
  • Marked sample has had enough time to re-intergrate
  • Marking hasn’t affected chances of survival
  • Marking is visible
  • No changes in pop size (births, deaths + migration)
32
Q

Why are ecosystems described as being dynamic?

A

They’re constantly changing

33
Q

Define succession

A

Change in ecosystem over time due to abiotic + biotic conditions

34
Q

What are the types of succession?

A
  • Primary succession - land that been newly formed/exposed. No soil/organic material to start w/
  • Secondary succession - land thats been cleared of all plants but soil remains
35
Q

Outline what happens during primary succession

A
  • Pioneer species (seeds + spores) blown by wind + grow
  • Abiotic conditions are hostile - pioneer species grow bc adapted to cope
  • Change abiotic conditions - die + microorganisms decompose dead organic material (humus). Forms basic soil
  • Makes condition less hostile eg. basic soil able to retain water, new organisms w/ diff. adaptations move, grow + die, making soil richer - larger plants grow
  • New species change env so less suitable for previous species
36
Q

Outline what happens during (secondary) succession

A
  • Pioneer species = larger plants
  • Each stage, diff plants + animals better adapted outcompete previous species, become dominant species
  • As succession goes on, ecosystem becomes complex + biodiversity inc
  • Final stage = climax community
  • Won’t change bc in a steady state
37
Q

Define climax community

A

Stable/final community

38
Q

The species making up the climax community depends on what?

A

Climate

39
Q

Define plagioclimax

A

When human activity artificially prevent sucession, preventing climax community from developing

40
Q

Define conservation

A

Protection + management of ecosystems in a sustainable way

41
Q

What are different ways to manage succession as a way of conserving?

A
  • Animal grazing - eat growing points
  • Managed fires - secondary succession will occur
42
Q

Give examples of different conserving techniques

A
  • Plants use seedbanks, stores seeds from diff plant species. If plant becomes extinct, stored plants used
  • Fishing quotas limits amount of certain fish species caught
  • Protected areas (nature reserves) protect habitats by restricting urban development, industrial development + farming
  • Endangered species bred in captivity

Biology A-Level (10 decks)

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