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Biology A2 > Populations and Ecosystems > Flashcards

Populations and Ecosystems Flashcards

1
Q

Ecosystem

A

A group of inter-related organisms, their physical environments and interaction between living and non-living factors

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2
Q

Abiotic

A

Non-living, physical conditions

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3
Q

Biotic

A

Any living component that affects the population of another organism, or the environment

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4
Q

Population

A

Group of organisms of the same species living in the same habitat at one time

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5
Q

Community

A

All organisms of different species living in the same habitat at one time

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6
Q

Habitat

A

Place where a community of organisms live

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7
Q

Microhabitat

A

A small specialized habitat within a larger habitat

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8
Q

Niche

A

Role of a species in an ecosystem and its interrelationship between all the abiotic and biotic factors affecting it

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9
Q

Suggest how sudden changes in temperature can affect cold-blooded and warm-blooded organisms differently

A
  • Can slow down or completely stop enzyme activity of cold-blooded organisms
  • Warm-blooded organisms can maintain a constant body temperature but will have less energy for: growth (mature slowly) and reproduction
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10
Q

Suggest how light intensity can affect organisms

A

Impacts photosynthesis so growth of plants/ food source for other organisms

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11
Q

Suggest how sudden changes in pH can affect organisms

A

Impacts enzyme action so metabolic rates

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12
Q

Competitive Exclusion Principle

A
  • if two competing species coexist they have different niches
  • if there is no difference between niches of competing species then the least competitive will be eliminated
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13
Q

Suggest why it is difficult to prove that competition is the reason for variations in a population

A
  • many abiotic factors affect population size
  • time lag
  • data on population size is difficult to obtain and not always reliable
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14
Q

Suggest why the population of prey is always greater than its predator

A

A single predator will eat several prey in order to survive

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15
Q

Suggest why predator-prey graphs have cyclic fluctuations

A

Disease and changes in abiotic factors

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16
Q

How to calculate population size of bacteria

A

Starting population x 2^n where n = no. of divisions

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17
Q

How to calculate growth rate

A

(no. of births - no. of deaths)/time

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18
Q

Carrying Capacity

A

Maximum population an ecosystem can support

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19
Q

Lag Phase

A
  • not many individuals to start with

- not all individuals have reached breeding age

20
Q

Exponential Growth

A
  • no limiting factors, e.g. competition

- many organisms reproducing freely

21
Q

Stationary Phase

A
  • carrying capacity reached

- limiting factors provide environmental resistance to further growth

22
Q

Death Phase

A
  • resources exhausted
  • accumulation of toxic waste
  • arrival of new predator or disease
23
Q

Succession

A

Changes over time in the species that occupy a particular area

24
Q

Primary Succession

A

Process by which void and barren land becomes populated for the first time by a pioneer species

25
Q

Pioneer species

A
  • specially adapted to withstand a hostile environment
  • first to colonise an ecosystem
  • build up soil allowing larger, more complex organisms to survive
26
Q

Features of pioneer species

A
  • asexual reproduction by wind-dispersed seeds or spores which are easily dispersed
  • wind resistant / adhere to rocks
  • no cuticle so can absorb water over entire surface
  • ability to fix nitrogen from air since no nutrients available
  • tolerance to extreme temperature changes
  • survive desiccation
  • photosynthetic
27
Q

Secondary Succession

A

Result of disturbance to landscape where species re-establish or change altogether to a new kind of biotic landscape

28
Q

Suggest why succession is important

A
  • creates new microclimates
  • ensures high biodiversity
  • results in many dominant species
29
Q

Climax Community

A
  • final stage of succession
  • abiotic factors constant
  • stable community / same types of species present
  • population stable around carrying capacity
  • (increased biodiversity)
  • (great variety of habitats)
  • (organisms fill almost all biological niches)
30
Q

Hostile Abiotic Factors

A
  • no water source
  • windy (no shelter)
  • lots of light
  • extreme fluctuations in temperature
31
Q

Explain why lichen is a pioneer species

A

Lichen (Algae and Fungus)

  • Algae provides sugars from photosynthesis
  • Fungus absorbs water and releases extracellular enzymes get minerals from rocks
32
Q

Describe how to estimate population size using mark-release-recapture technique

A
  • sample captured and marked with non toxic marking that does not affect their survival
  • released into wild for long enough to disperse evenly amongst population
  • (no. in first sample x no. in second sample)/ no. of marked recaptured
33
Q

Suggest assumptions made when using mark-release-recapture technique

A
  • proportion of marked to unmarked individuals => whole
  • marked individuals distributed themselves evenly amongst population
  • no immigration/emigration
  • few deaths / births
  • mark is not lost
  • mark is non toxic and does impact survival of organisms, i.e. not noticeable to predators
34
Q

Disruptive Selection

A
  • selection against individuals with phenotypes around the mean
  • favour individuals with both extreme phenotypes
35
Q

Polymorphism

A

Different phenotype exist in the same (interbreeding) population of a species

36
Q

Speciation

A
  • formation of new species due to reproductive isolation in a species
  • allele frequencies of demes become so different they can no longer reproduce to produce fertile offspring
37
Q

Gene Pool

A

Alleles of all genes of individuals in a population at a given time

38
Q

Allopatric Speciation

A

Populations become geographically isolated so cannot reproduce

39
Q

Sympatric Speciation

A

Reproductive behavioural isolation that occurs while populations still occupy the same area

40
Q

Genetic Drift

A
  • change in allele frequency due to chance (e.g. natural disaster)
  • impact greater on small populations
41
Q

Explain why smaller populations evolve at a faster rate

A
  • more genetic drift

- random mutations / elimination of individuals has a larger impact on allele frequency

42
Q

Suggest reasons speciation occurs

A
  • reproductive isolation
  • geographically isolated
  • different reproductive behaviours
  • gamete incompatibility
43
Q

Explain why larger mammals and birds are not found in a succession until the later stages

A

Vegetation not large enough to provide shelter (habitats) and food

44
Q

Suggest why the number of plant species may be greater before the climax community is reached

A
  • more open space
  • less competition for light, nutrients etc
  • plant species are outcompeted by dominant woodland
45
Q

Suggest why organisms with more shared taxa have similar base sequences of DNA

A
  • more shared taxa indicates more recent separation of ancestral species
  • less time for accumulation of mutations in DNA
46
Q

Suggest how organisms with similar niches could avoid competition

A
  • alter their own niche to avoid competition

- by eating another prey / plant

47
Q

Suggest why capture recapture is not suitable for larger mammal population

A
  • dangerous / harm animal

- inaccurate with smaller populations

Biology A2 (15 decks)

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