Chapter 18 — Population And Evolution Flashcards

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1
Q

How does genetic variation occur?

A

Genetic variation can occur in 3 ways:

  • mutations
  • meiosis
  • random fertilization of gametes
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2
Q

What are selection pressures?

A

Selection pressures are the environmental factors that affect an organism’s chance of survival and reproduction

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3
Q

What is stabilising selection?

A
  • organisms with middle range characteristics are more likely to survive and reproduce
  • occurs in a stable environment
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4
Q

Give a definition of variation.

A

Variation is essentially the differences that exist between individuals, occuring within species and between species.

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5
Q

What is directional selection?

A

when one of the extremes are favoured

individuals with allele for one

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6
Q

What is disruptive selection

A
  • when extreme characteristics on both ends of the range are favoured
  • and more likely to survive
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7
Q

Give 2 types of factors that cause phenotypic variation.

A

genetic factors and environmental factors both cause phenotypic variation

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8
Q

What is allopatric speciation?

A

A type of speciation where new species form from different populations that are found in different areas

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9
Q

Describe how you could use the mark-release-recapture method to estimate the number of lizards on an island.

A
  • collect sample 1 by capturing, marking and releasing the lizards
  • marking should be in a way that doesn’t make them obvious to predators
  • release them back into the wild
  • leaving sufficient time for them to randomly distribute over area
  • and then collecting sample 2 by recapturing them
  • population = (number in sample 1 × number in sample 2) divided by number of marked in sample 2
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10
Q

Habitat

A

Where an organism lives

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11
Q

Population

A

all the organisms of one species in a habitat

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12
Q

Community

A

Groups of different species in an area

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13
Q

Ecosystem

A

A community, including all the biotic features (predators, prey​) and all the abiotic conditions (temp, water availability)

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14
Q

Abiotic factors

A

The non-living physical or chemical features of an ecosystem that affect an organism’s survival and reproduction

  • temperature
  • climate
  • water
  • nutrients
  • oxygen concentrations
  • pollution
  • light intensity
  • moisture
  • pH
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15
Q

Biotic factors

A

All the living organisms of an ecosystem

  • plants
  • fungi
  • animals
  • predators
  • prey
  • food
  • bacteria
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16
Q

Niche

A

The role of a species within its habitat

17
Q

Adaptation

A

A feature that members of a species have that increases their chance of survival and reproduction.

18
Q

What is speciation?

A

Speciation is the development of a new species from an existing species, occuring when populations of the same species become reproductively isolated.

19
Q

What is the difference between allopatric and sympatric speciation?

A

Allopatric speciation occurs when a population is geographical isolated and sympatric speciation occurs when there is no physical separation.

20
Q

Describe the process of allopatric speciation.

A
  • physical barrier stops interbreeding between two populations of the same species
  • each side of the physical barrier will have slightly different conditions
  • and thus each population will experience different selection pressures
  • each population adapts to its new environment and conditions
  • allele and phenotype frequency change leading to the development of new species
21
Q

Genetic drift

A

When chance determines which allele for one genotype is passed on to offspring more often than the others. The number of individuals with the allele increases. This could eventually lead to reproductive isolation.

22
Q

the frequency of the beneficial alleles in the gene pool increases from generation to generation

A

23
Q

Interbreeding

A

When organisms of the same species breed

24
Q

Crossbreeding

A

When organisms of different species breed

25
Q

Carrying capacity

A

The maximum size of a population that an ecosystem can support

26
Q

Succession

A

the process by which ecosystems change overtime, of which there are two types: primary succession and secondary succession

can also be describes as the process by which communities of animals and plants colonise an area and then over time are replaced by other usually more varied communities

27
Q

Primary succession

A

1- occurs when there is just an empty inorganic surface such as bare rock

  • due to volcanic eruptions, landslides etc.
  • opportunists or pioneer species (mosses, lichens) are the first to colonise because they are hardy, don’t dry out easily
  • help to form humus by breaking down rock surfaces into organic material
  • when these plants die and decompose they form soil allowing other species (grasses, ferns) to take root
  • these also add to the soil when they die and decay
  • as more nutrients and water are retained in the soil, it us able to support larger species of plants
  • animal species make these plants their home and source of food
  • diversity increases
  • a climax community is reached at some point: the biodiversity of the ecosystem stays constant, the community is self-sustaining, the most productive group of organisms that environment can support
28
Q

Secondary succession

A
  • occurs when soil is present but free of vegetation
  • due to forest fires, floods, human disturbances etc.
  • the new climax community can be different from the original climax community