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Biology paper 2 > Topic 13: Populations in ecosystems > Flashcards

Topic 13: Populations in ecosystems Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define ecology

A

the study of the interelationships between organisms and their environment (abiotic and biotic factors)

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2
Q

Define Ecosystem

A

A community and all the non-living factors of its environment

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3
Q

Define population

A

A group of individuals of one species that occupy the same habitat at the same time and can potentially interbreed - abiotic and biotic factors can influence population size

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4
Q

Define community

A

All the populations of different species living and interacting in a particular place at the same time

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5
Q

Define habitat

A

A place where an organism lives - the physical conditions and other organisms present - there are microhabitats within each habitat

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6
Q

Define ecological niche

A

How an organism fits into an environment - where it lives and what it does there - no two species can occupy the same niche due to differing adaptations to the biotic and abiotic conditions (competitive exclusion principle)

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7
Q

What factors determine population size - give examples?

A
  • effect of abiotic factors - temperature, light, soil pH, water and humidity
  • interaction between organisms - competition and predation
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8
Q

Define carrying capacity

A

The maximum stable population size of an organism an ecosystem can support - slight changes in the environment can change the carrying capacity

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9
Q

What are the three main phases on a population growth graph?

A
  • lag phase (flat) - low growth rate - no environmental resistance
  • log phase (increase) - maximum growth rate (BR>DR) - no limiting factors
  • stationary phase (flat) - carrying capacity reached (BR = DR) - some environmental resistance - population is at its maximum size
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10
Q

Why is a log scale often used to plot population growth?

A

Rapid growth over a short period creates a large increase in values which can’t be plotted on a regular graph

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11
Q

How do abiotic factors influence carrying capacity?

A
  • if an abiotic factor is below or above the optimum
  • fewer individuals can survive and reproduce as adaptations are not suited to the conditions
  • population size decreases
  • so the carrying capacity for that species is reduced
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12
Q

Define intraspecific competition

A

individuals of the same species compete for resources such as food, water and breeding sites

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13
Q

How does resource availability impact population size when intraspecific competion is occuring?

A

Resources availability detemines size of population and influences competition
* population increases when resources are plentiful
* which causes competion to increase
* resources become limiting
* population begins to decline
* smaller population means less competition - more growth so population begins to grow again

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14
Q

Define interspecific competion

A

individuals of different species compete for resources

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15
Q

How does interspecific competition impact population size?
What is competitive exclusion principle?

A

one species will have a competitive advantage - its population size will increase while the other decreases
Competitive exclusion principle - no two species can occupy the same niche when resources are limiting - different niches = less competition for food and resources

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16
Q

Define predation

A

when an organism kills and eats another

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17
Q
A
17
Q

How does the predator - prey relationship affect population size?

A
  • predators eat prey - population of predators increases
  • prey population decreases - competition for food increases - predator population decreases
  • decreased predators - less prey are eaten = prey population increases
  • more prey are available for food = predator population increases again
18
Q

What is the role of selection pressure in changes in population size?

A

Disease and climatic changes causes selection pressure - population evolves to become better adapted to harsh conditions

19
Q

What factors should be considered when using a quadrat?

A
  • size of quadrat
  • number of quadrats - more quadrats = more RELIABLE
  • position of quadrat - sampling must be RANDOM to produce SIGNIFICANT results
20
Q

What are the two types of quadrat?

A
  1. frame quadrat
  2. point quadrat
21
Q

How is random sampling carried out?

A
  1. lay tape measures along two sides of the study area
  2. obtain coordinates using a random number generator
  3. place a quadrat at the coordinates and count the species within
22
Q

What type of sampling is a transect?

A

systematic

23
Q

How is a belt transect used?

A
  • stretch a string or tape across the ground
  • place a frame quadrat alongside and record the species inside
  • move quadrat at intervals and repeat
24
Q

Define abundance

A

the number of individuals of a species in a given area

25
Q

Define frequency

A

likelihood of a particular species occuring in a quadrat (if a species occurs in 15 /30 quadrats its occurence is 50%)
* indicates species present
* general distribution

26
Q

Define percentage cover

A

estimate of the area within a quadrat that a particular species covers
* data can be collected rapidly
* individual plant don’t need to be counted
BUT less useful when plants overlap

27
Q

What three factors are needed for reliable results?

A
  • large sample size (more representitive)
  • many quadrats (more reliable)
  • mean needs to be collected
28
Q

When is mark-release recapture used?

A

to investigate abundance of motile species

29
Q

What is the equation for mark release recapture?

A

individuals in sample one x individuals in sample 2 / number of marked recaptured

30
Q

What are the steps of mark-release recapture?

A
  1. capture/collect, mark AND release organisms
  2. leave time to disperse before second sampling/collection
  3. collect second sample and calculate estimated population size
31
Q

What 6 assumptions are made during mark-release recapture?

A
  • mark/label is not rubbed off during the investigation
  • method of marking is non-toxic and doesn’t make organism more vulnerable to predation
  • no deaths or births in the population
  • no immigration into the population or emigration out
  • marked individuals have sufficient time to redistribute evenly into the population
  • proportion of marked to unmarked in second sample is in the same proportion as the population as a whole
32
Q

Define succession

A

a change in a community over time due to changes in abiotic factors and/or species present

33
Q

Define climax community

A

a stable community where no further succession occurs

34
Q

What are pioneer species - what are their main features?

A

first species to colonise newly explosed land (eg volcanic island)
* produce MANY, WIND dispersed seeds
* RAPID germination of seeds
* ability to photosynthesise (not dependent on animal species)
* ability to fix nitrogen from the atmosphere
* tolerence to extreme conditions

35
Q

What are the common features of succession?

A
  • abiotic environment becomes less hostile
  • greater variety of habitats and niches
  • increased biodiversity
  • more complex food webs
  • increased biomass
36
Q

At what stage in succession is biodiversity highest and when does it decrease?

A

At mid succession - decreases** as** the climax community is reached as the dominant species outcompete the pioneer species, leading to their removal from the community

37
Q

Describe the stages of primary succession

A
  1. colonisation by pioneer species (lichen) - weathering of rock to produce sand/soil - lichen die and decompose which released nutrients
  2. change in the abiotic environement caused by species present
  3. enables further species to colonise/survive (mosses and ferns) , thicker layer of soil builds up, increased water retention - environment is less hostile so grasses, shrubs ans trees develop
  4. changes in diversity/biodiversity - many species
  5. stability increases/environment is less hostile - more food chains, more food webs - leads to stable community
  6. climax community is reached - stable over a long period
38
Q

Define secondary succession

A

Pioneer species become established on previously inhabited land (cleared by fire or for agriculture), soil (with seeds and roots) is already present and biomass is higher so secondary succession is much quicker

39
Q

Define conservation

A

preservation, protection or restoration of the natural environment and species there

40
Q

What are the main reasons for conservation?

A
  • personal
  • ethical
  • economic
  • cultural and aesthetic
41
Q

How can managing succession help to conserve habitats?

A

The climax community needs to be prevented
* usually done via grazing, mowing, burning land
* without this shrubs would take over and woodland would form

Biology paper 2 (4 decks)

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