17- selection+evolution

Question 1

genetic variation caused by

Answer 1

• mutations: changes to genes+chromosomes that may be passed on
• meiosis: new combinations of alleles in gametes formed
• random fertilisation: produces new allele combs in sexual reproduction
• random mating

Question 2

polygene:

Answer 2

diff genes at diff loci all contributing to a particular aspect of phenotype

Question 3

genetic diversity + how it leads to variation

Answer 3

total number of DIFF ALLELES in pop
diff combinations of alleles result in diff PROTEINS being produced->diff CHARACTERISTICS

Question 4

allele

Answer 4

different version of a gene

Question 5

prezygotic reproductive barrier

Answer 5

prevents fertilisation+formation of zygote
acts before fertilisation of egg

Question 6

postzygotic reproductive barrier

Answer 6

produces as result of hybridisation(diff species), reduces viability/reproductive potential of offspring

Question 7

sympatric speciation
(less frequent in animals)

Answer 7

ecological/behavioural separation leads to groups becoming reproductively separated with no gene flow between->forms separate species

Question 8

why is genetic diversity important for a population, and why is lack of genetic diversity in small populations dangerous

Answer 8

genetic diversity->variation within population = essential in process on natural selection, allowing population to adapt to changes over time
small pops can’t adapt to change as easily+more likely to become extinct

Question 9

genetic drift

Answer 9

change in allele frequency due to chance- not natural selection
likely when small number population separated from rest of large pop

Question 10

genetic drift leads to

Answer 10

loss of genetic variation- certain alleles lost due to chance

Question 11

founder effect

Answer 11

extreme genetic drift where small populations arise due to establishment of new colonies by few ISOLATED individuals

Question 12

founder effect leads to

Answer 12

smaller gene pools+less gen diversity within population
rare alleles in OG pop have higher frequency

Question 13

bottleneck effect

Answer 13

large reduction in pop size lasting at least 1 gen
greatly reduces gene pool+diversity

Question 14

conditions for Hardy Weinburg

Answer 14

no mutations,
pop isolated,
no selection,
large pop,
mating within population is random

Question 15

Which factors contribute to the emergence of new species

Answer 15

reproductive isolation of populations
genetic divergence driven by natural selection
genetic drift

Question 16

t-test measuring variation

Answer 16

comparing means of 2 sets of data
Follow normal distribution, continuous data,
Equal variance/SDs
Samples independent of each other

Question 17

environmental factors limiting populations

Answer 17

Competition for food
Competition for mates
Supply of water
temp

Question 18

types of selection

Answer 18

directional
stabilising
disruptive

Question 19

directional selection

Answer 19

Increases for one extreme, normal shifts in direction of favoured extreme

Question 20

stabilising selection

Answer 20

Increases allele frequency for the average phenotype, decreases allele frequency for extremes, curve narrows

Question 21

disruptive selection

Answer 21

Increases for multiple extremes, decreases for intermediates
Curve shifts into M shape, 2 peaks either side of OG peak

Question 22

Processes causing allele change

Answer 22

Natural selection
Founder effect
genetic drift
bottleneck effect

Question 23

natural selection

Answer 23

Selection pressures result in gradual change in allele frequency over several generations

Question 24

founder effect

Answer 24

Changes in allele frequencies occur in diff direction for newly isolated small pop in comparison to larger pop- due to CHANCE

Question 25

genetic drift

Answer 25

Gradual change in allele frequencies in small pop due to chance, not natural selection

Question 26

bottleneck effect

Answer 26

Reduction in gene pool of pop due to dramatic decrease in pop size

Question 27

artificial selection

Answer 27

- Select a population that displays variation. - Select individuals with desired traits, (high milk production) - Selectively breed individuals together that display desired traits. - Grow and test the offspring for the desired traits. - Repeat the selection process across many generations

Question 28

Evolution

Answer 28

formation of new species from pre-existing species OVER TIME variation: Change of characteristics of species due to allele frequency changes natural selection / selective advantage for survival / survival of the fittest

Question 29

Speciation

Answer 29

organisms w/ same features, interbreed to produce fertile offspring, reproductively isolated from other species

Question 30

morphological

Answer 30

structural features

Question 31

physiological

Answer 31

metabolic processes in living organisms

Question 32

biochemical

Answer 32

base sequence in DNA molecules + a.a. Sequences

Question 33

Molecular comparisons between species

Answer 33

1. compare a.a. sequences of proteins. more sim sequence=more closely related 2. Nucleotide sequences of mtDNA

Question 34

Characteristics of mtDNA

Answer 34

- Circular, doesn’t cross over - Mutations occur at constant rate- molecular clock - mtDNA mutates faster than nuclear DNA- changes only arise through mutation, aren’t repaired. Not associated with histones. - Smaller, fewer genes->quicker mtDNA analysis - mtDNA passed from mother to offspring, all descendants of 1 female have identical mtDNA

Question 35

explain how variation in ecosystems contributes to biodiversity

Answer 35

- diff habitats - diff niches - diff selection pressures - genetic diversity - adaptation - diff climates

Question 36

give reasons why low genetic variation may decrease the long term survival of a species

Answer 36

- most alleles identical so when selection pressures act against genotypes, most likely to die - aren't able to survive+reproduce offspring -> low organism numbers -> **inbreeding depression, increased homozygosity** - risk of extinction

Question 37

examples of evidence obtained from observations+exps helping confirm sea blush plants belong to same species

Answer 37

- same morphological features - same nucleotide/amino acid sequences - can reproduce to generate fertile offspring - not reproductively isolated - occupy same niche

Question 38

why natural selection occurs (excluding selection pressure)

Answer 38

- populations produce many offspring, will have genetic variation - mutations/sexual reproduction, random fertilisation - competition (food, mates, resources)