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Biology > Populations in ecosystems > Flashcards

Populations in ecosystems Flashcards

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1
Q

What is an ecosystem?

A

Made up of a community and all of the non-living components of the environment. They are very dynamic systems

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2
Q

What are the three phases in the usual pattern of growth for a natural population?

A
  • period of slow growth - as organisms adjust to their environment
  • period of rapid growth - ever-increasing number of individuals continue to reproduce
  • period where population growth declines until stable - always fluctuations because food supply changes, disease, resource exhaustion and migration in/outward
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3
Q

What can cause the size of a population to vary?

A
  • abiotic factors
  • interactions between organisms (inter/intraspecific competition)
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4
Q

What is ecological niche?

A

How an organism fits into its environment, involving its adaptation to both biotic and abiotic factors which allow it to survive, reproduce and maintain a viable population

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5
Q

How should you plot a growth curve when growth occurs rapidly?

A

Using log number of individuals

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6
Q

Why does bacteria population eventually level off?

A

Initially there are no limiting factors so growth is rapid

  • mineral ions are consumed as population grows larger
  • bacteria at surface prevent light from reaching those beneath
  • other species may be introduced which use the bacteria for food, or compete for light and mineral ions
  • winter brings lower temperatures and lower light intensity
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7
Q

What are some abiotic factors?

A
  • temperature
  • pH
  • light/shade
  • water and humidity
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8
Q

What are some biotic factors?

A
  • food supply
  • predation
  • inter/intraspecific competition
  • disease
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9
Q

How does light affect the organism?

A
  • photosynthesis rate increases as light intensity increases
  • opening of stomata
  • kinesis
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10
Q

How does wind/water current affect the organism?

A
  • transpiration rates
  • evaporation of water from animals
  • seed dispersal - effects competition
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11
Q

How does water/humidity affect the organism?

A
  • transpiration rates
  • evaporation from animals
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12
Q

How does pH affect the organism?

A
  • tertiary structure of enzymes
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13
Q

How does temperature affect the organism?

A
  • enzymes
  • kinetic energy
  • lower temp = more dissolved O2
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14
Q

What techniques can be used to investigate populations?

A
  • transect sampling - tape is stretched along a habitat and measurements taken at regular intervals (where conditions and organisms change over distance)
  • gridded frame quadrat sampling - gridded quadrat placed at random coordinates ( collects frequency data)
  • open frame quadrant sampling - quadrat without subdivisions placed at random coordinates (estimates percentage cover)
  • point quadrat sampling - horizontal bar with 10 holes at set intervals, a pin is dropped into the holes and each species touching the pin can be counted (estimates percentage occurrence of individuals)
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15
Q

How can you measure abundance of species?

A
  • frequency eg. if the species occurs in 15/30 quadrats, frequency is 50%
  • percentage cover
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16
Q

How can you estimate population size through mark-release-recapture?

A

(number of species in sample 1 x number of species in sample 2) / number of marked individuals recaptured

17
Q

What assumptions does mark-release-recapture rely on?

A
  • proportion of marked and unmarked individuals remains the same
  • animals will evenly redistribute themselves
  • must have a definite boundary (no in/outward migration
  • no/few births and deaths
  • method of marking is non-toxic and does not make the individual more/less likely to survive
  • mark cannot be rubbed off
18
Q

What is succession?

A

How ecosystems change as new species colonise. Can result in a less hostile environment which makes it more likely for species to survive

19
Q

What are the stages of succession?

A
  • initially a pioneer species will colonise. These pioneer species will make up a pioneer community
  • the pioneer community will eventually die and decompose, and biological weathering will occur on rocks, releasing sufficient nutrients to support a colony of small plants. This creates a layer of top soil called humus and more favourable conditions
  • death and decomposition of plants creates a thicker layer of soil that holds organic material and water, making it easier for more plants to grow
  • the environment becomes less hostile, more species develop that act as food sources, food chains develop into complex food webs and communities become stable
  • climax community consisting of animals and plants
20
Q

What does succession lead to?

A
  • abiotic environment becomes less hostile
  • greater variety of habitats and niches
  • increased biodiversity
  • more complex food webs
  • increased biomass
21
Q

What are the reasons for conservation?

A
  • personal - to maintain our planet and therefore our life support system
  • ethical - other species have occupied the earth longer than us and should be allowed to coexist, respect is preferable to disregard
  • economic - gigantic gene pool which can make millions of substances which may prove valuable in the future
  • cultural and aesthetic - habitats and organisms enrich our lives, variety adds interest to everyday life and can inspire others eg. writers/poets/artists who entertain and fulfil us
22
Q

How can succession be prevented?

A
  • temporarily introduce grazing animals to stop plants establishing themselves
  • controlled fires to burn away shrubs and trees
23
Q

What impact does farming have on species diversity?

A

reduces diversity due to pesticides and monoculture

24
Q

What impact does farming have on genetic diversity?

A

decreases genetic diversity because farmers select for certain characteristics eg. crops with greatest yield, cows with greatest milk production, so the number of alleles within the population is reduced

25
Q

What is sampling?

A

selecting a group of individuals to measure that will represent the whole population

Biology (28 decks)

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