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Worcester Sixth Biology 101 > Variation and Evolution > Flashcards

Variation and Evolution Flashcards

1
Q

What does variation mean?

A

differences between organisms of the same species

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2
Q

What are the 3 categories that are causes of variation?

A

different genotypes
different epigenetic modifications
different environmental effects

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3
Q

Which causes of variation are heritable?

A

different genotype
different epigenetic modifications

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4
Q

How can asexually reproducing organisms increase their heritable variation?

A

mutations of genes

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5
Q

What are the 4 ways that variation can be increased through sexual reproduction?

A

The crossing over between homologous chromosomes in prophase 1 of meiosis
The random distribution of chromosomes during metaphase 1 of meiosis
THe random ditribution of chromatids at metaphase 2 of meiosis
THe mixing of 2 different parental genotypes at fertilisation

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6
Q

What kind of variation is non-heritable?

A

different environmental effects

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7
Q

What are the 2 categories of variation?

A

discontinuous and continuous

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8
Q

What is discontinuous variation?

A

variation that can be only one state or another, and there are no intermediates. The character states are clear cut and easy to tell apart

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9
Q

What are some examples of discontinuous variation?

A

eye colour, hair colour, blood group, number of fingers, form of moth (melanic or speckled)

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10
Q

What does monogenic mean?

A

involving or controlled by a single gene

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11
Q

How can environment effect gene expression?

A

temperature for Siamese cat if cold causes melanin to be produced in extremities making areas like ears, paws, tail, face black
in early development, external experiences spark signals between neurons, which respond by producing proteins. these gene regulatory proteins head to the nucleus of the neural cell, where they either attract or repel enzymes

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12
Q

What is continuous variation?

A

can take any value in a given range, These characteristics are controlled by many genes and are therefore polygenic. The environment can influence the expression of these genes and therefore plays a role in determining phenotypic variation

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13
Q

What are some examples of continuous variation?

A

height, finger length

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14
Q

How is continuous variation data usually presented?

A

bell curve or normal distribution curve

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15
Q

What is over production?

A

when a species produce a larger number of offspring than that which can be physically supported by parents or ecosystem that they’re in

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16
Q

Why does population size remain roughly constant?

A

sunlight availability
food supply
available space
- when an organism uses more than what is available, causes the death of that part of an ecosystem, which in turn leads to death of the species.

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17
Q

What is intraspecific competition?

A

between individuals of the same species

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18
Q

what is interspecific competition?

A

between individuals of different species

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19
Q

What are 3 ways gene expression is regulated and results in variation?

A

Gene mutation
DNA methylation
Histone modification

20
Q

How does gene mutation cause variation?

A

it changes what proteins are made

21
Q

How does DNA methylation cause variation?

A

more methylated means the gene is less likely to be transcribed, (other genes will begin to emerge)

22
Q

How does Histone modification cause variation?

A

adding of acetyl groups means histone is going to be less tightly packed, so protein is more accessible and results in more transcription

23
Q

What is heritable variation?

A

a characteristic that can be passed on from parent to offspring through genes like eye colour and hair colour

24
Q

What is non-heritable variation?

A

a characteristic that cannot be passed from parent to offspring through genes like tattoos and scars

25
Q

Is variation imposed by the environment (that doesn’t consist of epigenetic change) heritable or non-heritable?

A

non-heritable - cannot be transmitted to offspring

26
Q

What is a selection pressure?

A

something that puts stress on an organism and can result in decline, unless adaptation occurs - it therefore drives the selection of suitable alleles due to the environment

27
Q

What does population genetics mean?

A

study of genetic variation within and among population and the evolutionary factors that explain this variation (allele’s frequency’s , genotypes)

28
Q

What is selection?

A

preferential survival and reproduction of individuals with certain genotypes
suitable alleles surviving in an environment

29
Q

What is a gene pool?

A

all the genes within a breeding population, (could potentially be inherited)

30
Q

What is allelic frequency?

A

the number of alleles in a population, how often they occur. proportion of different alleles in a specific gene pool

31
Q

What is genetic drift?

A

the change in frequency of an existing gene variant in the population due to random chance

32
Q

What are some examples of selective agencies/pressures?

A

food, space, water and light

33
Q

What might animals compete for?

A

intraspecific - competition for a mate (breeding partner)
interspecific - competition for food, territory, water

34
Q

What is directional selection?

A

moving towards 1 phenotype, over time frequency of phenotype changes, due to reproduction

35
Q

What is stabilising selection?

A

when extremes are removed from a population

36
Q

What is disruptive selection?

A

When extremes are selected for in a population

37
Q

What can the Hardy-Weinberg principle be used for?

A

calculate the genetic variation of a population
estimate the frequencies of dominant or recessive alleles
estimate the different genotypes of a characteristic

38
Q

What is the equation used in the Hardy-Weinberg principle?

A

p^2 + 2pq + q^2
where p = dominant allele
q = recessive allele

39
Q

What does the p^2 show about a organism in Hardy-Weinberg Principle?

A

It is homozygous for the dominant allele

40
Q

what does the pq show about an organism in Hardy-Weinberg principle?

A

It is a heterozygous genotype

41
Q

what does the q^2 show about an organism in the Hardy-Weinberg principle?

A

it is the homozygous for the recessive allele

42
Q

What are the conditions for the Hardy-Weinberg principle to work?

A

only 2 alleles for a phenotypic trait
frequencies of alleles must stay the same from generation to generation

43
Q

What must be in place for the frequencies of alleles to remain the same from generation to generation?

A

large population
diploid organisms
allele frequencies same for both species
no selection for or against a phenotype
random mating throughout the population
reproduce sexually
no mutations
population is isolated (no immigration or emigration)

44
Q

What is a population bottleneck?

A

event that drastically reduces the size of a population only some alleles can be passed on and inherited in the next generation

45
Q

What is the Founder Effect?

A

reduced genetic diversity which results when a population is descended from a small number of individuals in a new, isolated population

Worcester Sixth Biology 101 (31 decks)

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