Speciation Evolution

Question 1

genetic variation (4)

Answer 1

genetic variation is the basis for evolution

a population must have genetic variation in order to evolve (one of the most important things required for evolution)

Question 2

genotypic frequencies maths

Answer 2

genotypic frequencies

P = f(AA) = N_AA / N_total
H = f(Aa) = N_Aa / N_total
Q = f(aa) = N_aa / N_total

P + H + Q = 1

Question 3

genotypic frequency (4)

Answer 3

genotypic frequency is the proportion of individuals in a population with a given genotype

Question 4

genotypes for a locus with two alleles

Answer 4

for a locus with two alleles (A and a)

there are three genotypes: aa, Aa, AA

Question 5

maths lol

Answer 5

allelic (gene or gametic) frequencies

p = f(A) = (2 N_AA + N_Aa) / 2 x N_ total = P + 0.5H

q = f(a) = (2 N_aa + N_Aa) / 2 x N_ total = Q + 0.5H

p + q = 1

Question 6

assumptions for hardy weinburg equilibrium (4)

Answer 6

1. random mating
2. no mutation
3. no migration
4. no selection
5. large population

Question 7

inbreeding (4)

Answer 7

Most common type of nonrandom mating
* Positive assortative mating for relatedness
* An extreme version is self-fertilisation

Question 8

non-random mating

Answer 8

Two types:
1. Positive assortative mating
- tendency for like individuals to mate

2. Negative assortative mating
   - tendency for unlike individuals to mate

Question 9

causes for evolutionayr change (4) (last half)

Answer 9

1. mutation - ultimate sources of variation, individual mutations are rare -> weak cause of genetic change in populations
2. migration (gene flow) - effect is to make populations more similar, reduces genetic divergence between populations, while maintaining variation within populations
3. genetic drift - Random changes in allele frequencies from one
   generation to the next
   Fluctuations are caused by random sampling of
   gametes from the gene pool
   Rate of change depends on population size - the smaller the sample, the greater the rate of change
4. natural selection - sexual selection is a subset of natural selection. Most complex of all the evolutionary forces
   affecting the genetic makeup of populations
   Occurs in many ways - not all result in
   evolutionary changes

Question 10

gene flow

Answer 10

highly mobile species or those within continuous distriubtuons show fewer genetic differences amoung populations

Question 11

importance of random drift (genetic drift) (4)

Answer 11

Conservation genetics - loss of genetic variation in small populations
* Evolution — potential for rapid evolutionary change without selection, or even in opposition to selection

Question 12

is selection the main mechanism causing genetic differences? (4)

Answer 12

Selection is not the only mechanism causing genetic differences between populations, but is the only one that causes adaptive changes

Question 13

natrual selection (4) (4)

Answer 13

1. Variation exists
2. Traits are inherited
3. Differential survival and reproductive success

OUTCOME:
Those alleles associated with greater survival or reproductive success will increase in frequency the next generation

Answer 14

Measured as the average contribution by a particular genotype to subsequent generations
* Environment dependent - can vary between sites

Question 15

sexual selection

Answer 15

Sexual selection: secondary sexual characters
* Function during reproduction, but are not necessary for breeding
* Reduce survival
- manoeuverability
- powers of flight
- more conspicuous
- energetically costly

Question 16

which one is more important reproductive success or survival

Answer 16

reproductive success is more important than survival

Question 17

types of sexual selection (4)

Answer 17

Types of sexual selection
Intrasexual competition - members of one sex compete with each other for members of the other sex
Intersexual choice - members of one sex choose mates

Question 18

mate choice, direct and indirect benefits (4)

Answer 18

1. Direct benefits - parental care, provide food, protection
2. Indirect benefits - attributes of mate are inherited by
   offspring

Question 19

the handicap hypothesis

Answer 19

Indirect benefit - the handicap hypothesis
* Assumes males vary in their quality - some males have genes that confer higher quality (“good genes”) than others (“bad genes”)
.
Males with ability to possess a handicap have good genes so females that mate preferentially with these males will have offspring with good genes

Question 20

morphological (taxonomic) species concept

Answer 20

members of a species are morphologically alike

Question 21

biological species concept limitations (4)

Answer 21

does not consider asexually reproducing species, fossils
> overlooks common cases of hybridisation between species
morphological diversity and reproductive isolation do not go
hand-in-hand

Question 22

biological species concept

Answer 22

Biological species concept - groups of interbreeding individuals that are reproductively isolated from other such
groups

Question 23

dog breeds and biolgoical species concept

Answer 23

Applies to populations not individuals
genes from Great Dane to Chihuahua is possible through intermediates, but not directly

Question 24

what do all species concepts have in common (4)

Answer 24

All models emphasise the restriction of gene flow between populations so that divergence between them can occur

Reproductive isolation is important from an evolutionary perspective because it allows different species to evolve in their own ways

Question 25

two things required for speciation (4) (4)

Answer 25

1. divergence 2. reproductive isolation

Question 26

ways reproductive isolation can occur

Answer 26

1. pre-zygotic barriers 2. post-zygotic barriers

Question 27

pre-zygotic barriers

Answer 27

1. Pre-zygotic barriers (before fertilisation) a) Ecological - species occupy the same geographic area but do not hybridise because they occupy separate habitats b) Temporal - differences between species in the timing of reproduction c) Behavioural - differences between species in courtship behaviours d) Mechanical - physical restrictions to mating e) Gametic - gametes of different species do not interact

Question 28

post-zygotic barriers (4)

Answer 28

2. Post-zygotic barriers (after fertilisation) a) Zygote dies early during embryogenesis b) F1 hybrid survive but are sterile c) Backcross or F2 hybrids are inviable or sterile

Question 29

how does reproductive isolation arise (4) (4)

Answer 29

Post-zygotic isolation > cannot be the direct results of natural selection because it is impossible to select for inviable offspring * must be a side-effect of genetic change for other reasons Pre-zygotic isolation can be the direct result of selection - but only if there is already post-zygotic isolation (reinforcement)

Question 30

allopatry meaning

Answer 30

allopatric populations do not overlap

Question 31

sympatry meaning

Answer 31

sympatric populations occur in the same place

Question 32

sympatric speciation

Answer 32

A new species arises within the distribution of the original species No geographic barrier needed

Question 33

adaptive radiation

Answer 33

Adaptive radiation: a rapid evolutionary diversification of a single lineage Characterised by an increase in the morphological and ecological diversity

Question 34

a lot of

Answer 34

a lot of diversity in a species can be due to a lack of competitors (e.g. Hawaiian drosophila) , meaning new species that arrive on island can exploit all these resources and fill all these environmental niches not being used

Question 35

character displacement (4)

Answer 35

Character displacement: differences among species are accentuated in regions where they co-occur, but are minimised or lost where the species' distributions do not overlap

Question 36

summary

Answer 36

Biological species are evolutionarily independent lineages, separated by reproductive isolation Geographic separation is the easiest starting point for the understanding of the evolution of reproductive isolation Basic ideas about competition and natural selection can go a long way in explaining major patterns in nature