Variation and Evolution

Question 1

What does variation mean?

Answer 1

differences between organisms of the same species

Question 2

What are the 3 categories that are causes of variation?

Answer 2

different genotypes
different epigenetic modifications
different environmental effects

Question 3

Which causes of variation are heritable?

Answer 3

different genotype
different epigenetic modifications

Question 4

How can asexually reproducing organisms increase their heritable variation?

Answer 4

mutations of genes

Question 5

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

Answer 5

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

Question 6

What kind of variation is non-heritable?

Answer 6

different environmental effects

Question 7

What are the 2 categories of variation?

Answer 7

discontinuous and continuous

Question 8

What is discontinuous variation?

Answer 8

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

Question 9

What are some examples of discontinuous variation?

Answer 9

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

Question 10

What does monogenic mean?

Answer 10

involving or controlled by a single gene

Question 11

How can environment effect gene expression?

Answer 11

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

Question 12

What is continuous variation?

Answer 12

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

Question 13

What are some examples of continuous variation?

Answer 13

height, finger length

Question 14

How is continuous variation data usually presented?

Answer 14

bell curve or normal distribution curve

Question 15

What is over production?

Answer 15

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

Question 16

Why does population size remain roughly constant?

Answer 16

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.

Question 17

What is intraspecific competition?

Answer 17

between individuals of the same species

Question 18

what is interspecific competition?

Answer 18

between individuals of different species

Question 19

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

Answer 19

Gene mutation
DNA methylation
Histone modification

Question 20

How does gene mutation cause variation?

Answer 20

it changes what proteins are made

Question 21

How does DNA methylation cause variation?

Answer 21

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

Question 22

How does Histone modification cause variation?

Answer 22

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

Question 23

What is heritable variation?

Answer 23

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

Question 24

What is non-heritable variation?

Answer 24

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

Question 25

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

Answer 25

non-heritable - cannot be transmitted to offspring

Question 26

What is a selection pressure?

Answer 26

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

Question 27

What does population genetics mean?

Answer 27

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

Question 28

What is selection?

Answer 28

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

Question 29

What is a gene pool?

Answer 29

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

Question 30

What is allelic frequency?

Answer 30

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

Question 31

What is genetic drift?

Answer 31

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

Question 32

What are some examples of selective agencies/pressures?

Answer 32

food, space, water and light

Question 33

What might animals compete for?

Answer 33

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

Question 34

What is directional selection?

Answer 34

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

Question 35

What is stabilising selection?

Answer 35

when extremes are removed from a population

Question 36

What is disruptive selection?

Answer 36

When extremes are selected for in a population

Question 37

What can the Hardy-Weinberg principle be used for?

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

It is homozygous for the dominant allele

Question 40

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

Answer 40

It is a heterozygous genotype

Question 41

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

Answer 41

it is the homozygous for the recessive allele

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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)

Question 44

What is a population bottleneck?

Answer 44

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

Question 45

What is the Founder Effect?

Answer 45

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