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AL. AQA Biology > natural selection and speciation > Flashcards

natural selection and speciation Flashcards

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1
Q

stabilising selection

A
  • response to STABLE environment
  • mode stays same, sd falls - population graph gets narrower and taller as selection against mutation takes place
  • eg. birth weight
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2
Q

bottleneck event

A
  • when a population is reduced to a few breeding individuals ∴ much narrower gene pool
  • drastic reduction in population
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3
Q

directional selection

A
  • response to CHANGE in environment
  • eg. poison used and resistant individuals start to occur
  • phenotypes shift in one direction and one aspect of a trait is emphasised (curve shifts right or left)
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4
Q

disruptive/diversifying selection

A
  • response to FLUCTUATING environment
  • favours 2 extremes of a trait at expense of intermediate forms
  • middle of curve is eliminated and 2 peaks form either side of it
  • eg. rock pocket mouse
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5
Q

prezygotic barrier

A

those which prevent fertilisation from happeneing

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6
Q

postzygotic barrier

A

fertilisation may occur but any offspring are either not viable or are sterile

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7
Q

eg. prezygotic barrier (3)

A
  • seasonal isolation
  • behavioural isolation
  • mechanical incompatibility
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8
Q

eg. postzygotic barrier (2)

A
  • hybrid inviability

- hybrid sterility

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9
Q

allopatric speciation

A

between 2 geographically isolated populations - gene pool physically separated ∴ separate populations evolve independently

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10
Q

sympatric speciation

A

organisms in the same area become separated into 2+ reproductively isolated groups

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11
Q

variation

A

difference in characteristics shown by organisms belonging to the same natural population or species

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12
Q

discontinuous variation

A

when you have or haven’t got a feature - 2 options

eg. blood group

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13
Q

continuous variation

A

characteristics on a gradient from one extreme to the other - influenced by polygenes and environmental factors

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14
Q

causes of variation (4)

all lead too…

A

1) crossing over of alleles during mitosis
2) independent segregation of chromosomes (Meiosis I)
3) random fusion of gametes
4) mutations in DNA

… gene reshuffling ∴ variation

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15
Q

selection

A

process by which organisms better adapted to the environment survive and reproduce and those not so well adapted fail to reproduce or die

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16
Q

genetic drift

A

a change In the gene pool due to chance

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17
Q

founder effect

A

new colony started by a few members of the original populations, reducing genetic variation ∴ may lead to speciation

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18
Q

isolating mechanism

A

barrier preventing gene exchange

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19
Q

point mutation

A

change in base sequence at a single base in the gene - single base deleted, substituted or inserted

20
Q

stem cells

A

unspecialised cells which can develop into other types of cell

21
Q

totipotent stem cells

A

can specialise into ANY body cell, including placenta

22
Q

pluripotent stem cells

A

can specialise into any body cell, but NOT placenta

23
Q

multipotent stem cells

A

present in adult mammals - able to specialise into a few different types of cell

24
Q

unipotent stem cells

A

present in adult mammals - able to specialise into only one type of cell

25
Q

how do stem cells become specialised?

A

during development they only transcribe and translate part of their DNA, depending on conditions they are in, causing some genes to be expressed and others not to be

26
Q

iPS cells

A

induced pluripotent cells

27
Q

how are iPS cells made

A

in lab - infecting cells with specially-modified virus which has genes coding for transcription factors within its DNA - genes are passed to the cell’s DNA meaning that the cell can produce the transcription factors

28
Q

stem cell treatments (currently)

A

bone marrow transplant - to replace faulty bone marrow - treat leukaemia

29
Q

future stem cell therapies (5)

A
  • spinal cord injuries
  • heart disease and damage caused by heart attacks
  • bladder conditions
  • respiratory diseases
  • organ transplants
30
Q

how can transcription factors reprogram cells to form iPS cells

A
  • attach to promoter region of gene

- stimulate/prevent binding of RNA polymerase so that transcription does/doesnt occur

31
Q

transcription factors

A

proteins that control rate of protein synthesis by switching genes on and off

32
Q

transcription factors act as…

A

activators

repressors

33
Q

how to transcription factors work?

A
  • factors binds to promoter region
  • rna polymerase is complimentary and therefore binds to region, activating it
  • gene then switched on
  • transcription can occur
34
Q

proto-oncogenes

A

regulate stages in mitosis - stimulate cell division/growth

35
Q

tumour supressor genes

A

prevent tumours

36
Q

mutation type in proto-oncogenes

A

gain of function mutation

37
Q

mutation type in tumour supressor genes

A

loss of function mutation

38
Q

metastisis

A

travel in bloodstream + affect other tissues and spreads

39
Q

why does genetic drift occur faster in smaller populations

A

as relatively few individuals = relatively small gene pool = less genetic diversity therefore any mutation will quickly affect members of population because frequency is relatively high (in large pops effect is diluted)

40
Q

competition

A

when 2+ individuals share any resource that is insufficient to supply all requirements fully

41
Q

infraspecific comp

A

between 2 members of the same species

42
Q

interspecific comp

A

between 2 members of different species

43
Q

competitive exclusion principle

  • overall message?
A

population of species with competitive advantage will gradually increase in size and the other one will diminish - if conditions remain the same, one species will be completely removed

  • no 2 species can occupy the same niche indefinitely when resources are limited
44
Q

genome

A

all genetic material (alleles) in an organism

45
Q

proteome

A

all the proteins produced by the genome (controlled by transcription factors)

AL. AQA Biology (18 decks)

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