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
Pioneer species
- specially adapted to withstand a hostile environment - first to colonise an ecosystem - build up soil allowing larger, more complex organisms to survive
26
Features of pioneer species
- 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
Secondary Succession
Result of disturbance to landscape where species re-establish or change altogether to a new kind of biotic landscape
28
Suggest why succession is important
- creates new microclimates - ensures high biodiversity - results in many dominant species
29
Climax Community
- 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
Hostile Abiotic Factors
- no water source - windy (no shelter) - lots of light - extreme fluctuations in temperature
31
Explain why lichen is a pioneer species
Lichen (Algae and Fungus) - Algae provides sugars from photosynthesis - Fungus absorbs water and releases extracellular enzymes get minerals from rocks
32
Describe how to estimate population size using mark-release-recapture technique
- 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
Suggest assumptions made when using mark-release-recapture technique
- 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
Disruptive Selection
- selection against individuals with phenotypes around the mean - favour individuals with both extreme phenotypes
35
Polymorphism
Different phenotype exist in the same (interbreeding) population of a species
36
Speciation
- 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
Gene Pool
Alleles of all genes of individuals in a population at a given time
38
Allopatric Speciation
Populations become geographically isolated so cannot reproduce
39
Sympatric Speciation
Reproductive behavioural isolation that occurs while populations still occupy the same area
40
Genetic Drift
- change in allele frequency due to chance (e.g. natural disaster) - impact greater on small populations
41
Explain why smaller populations evolve at a faster rate
- more genetic drift | - random mutations / elimination of individuals has a larger impact on allele frequency
42
Suggest reasons speciation occurs
- reproductive isolation - geographically isolated - different reproductive behaviours - gamete incompatibility
43
Explain why larger mammals and birds are not found in a succession until the later stages
Vegetation not large enough to provide shelter (habitats) and food
44
Suggest why the number of plant species may be greater before the climax community is reached
- more open space - less competition for light, nutrients etc - plant species are outcompeted by dominant woodland
45
Suggest why organisms with more shared taxa have similar base sequences of DNA
- more shared taxa indicates more recent separation of ancestral species - less time for accumulation of mutations in DNA
46
Suggest how organisms with similar niches could avoid competition
- alter their own niche to avoid competition | - by eating another prey / plant
47
Suggest why capture recapture is not suitable for larger mammal population
- dangerous / harm animal | - inaccurate with smaller populations