Lecture 7- the origin of species

Question 1

what does evolution require to occur?

Answer 1

Changes in allele and genotype frequency

Question 2

what are the evolutionary changes that effect changes in allele and genotype frequency?

Answer 2

• genetic drift
• mutation
• gene flow
• natural selection

Question 3

what is mutation?

Answer 3

changes in the genetic code

Question 4

when is mutation more successful at causing evolution?

Answer 4

when it occurs in cells that produce gametes, as the mutation can be passed onto the offspring

Question 5

on which genes does selection not occur on?

Answer 5

ones that affect the phenotype

Question 6

why may mutations not be beneficial?

Answer 6

often organisms are already well adapted to their environments, so changes may reduce this adaptability and not be beneficial

Question 7

what rate does mutation occur at?

Answer 7

1/100000 genes per generation, low impact on population

Question 8

what is gene flow?give an example

Answer 8

• the genetic exchange between populations

- the movement of fertile individuals or movement of gametes (pollen) between populations

Question 9

how does gene flow reduce genetic differences between populations?

Answer 9

there’s an increased amount of shared genetic material between the two

Question 10

what is genetic drift?

Answer 10

the Chance alterations in the allele frequencies of populations

Question 11

what are the two main mechanisms of genetic drift?

Answer 11

• bottleneck effect

- foundler effect

Question 12

explain the bottleneck effect

Answer 12

• the parent population undergoes a massiv ereduction in population size, this may be as a result of a natrual disaster
• a small random assortment of survivors with random genes survive,with different allele frequencies to the prior population and some may be missing entirely
• this significantly reduces genetic diversity, and diversity may take a long time to recover after this event

Question 13

explain the founder effect

Answer 13

• a few induviduals of a species migrate and colonize a new region (eg. a volcanic island) ,and become founders of this new isolated population
• this new gene pool differs significantly to the new population
• rare alleles may be significant as they will be the genes passed on the future generation
• this leads to a loss of genetic variability and non random distribution of genes

Question 14

how does genetic drift impact a species ability to adapt to an environment?

Answer 14

it leads to a loss of genetic variation. evolution requires variation in order for adaptation to occur, so this impacts how well suited these organism are to their environment

Question 15

explain natural selection in genetic terms

Answer 15

occurs from individuals passing on alleles to the next generation, that differ in frequency to the current one

Question 16

what are the three modes of natural selection?

Answer 16

• stabilizing
• diversifying
• directional

Question 17

what is directional selection?

Answer 17

• when the conditions favour individuals exhibiting one extreme of the phenotype range.one sided outlier advantage
• common in changing environments

Question 18

which method of natural selection is a one sided outlier advantage?

Answer 18

directional

Question 19

what is disruptive selection?

Answer 19

when the extremes of the phenotype range are favored over the intermediate ones

Question 20

what is stabilizing selection?

Answer 20

-when the intermediate phenotype variants are favored over the intermediate ones

Question 21

what is k selection? what is it dependent on

Answer 21

• k selection occurs in high density populations, where traits that use lesser resources are favored
• its density dependent

Question 22

what is r selection?

Answer 22

at low density populations, with no pressure on resources, selection favors traits that allow rapid reprouduction

Question 23

which one, r or k selection, favours traits that allow rapid reproduction?

Answer 23

r selection

Question 24

in what type of population does k selection occur?

Answer 24

in a high density one with lesser access to resources

Question 25

what is allopatric speciation?

Answer 25

• changes in environment cause a population to be isolated

- this population then evolves in isolation, causing division into a new species

Question 26

what is sympatric speciation?

Answer 26

• occurs in geographical overlapping populations
• changes in environment cause selection to act upon some individuals
• gene flow is reduced (eg. by chromosome mutations or via non random mating)
• the two continue to evolve until they can no longer interbreed

Question 27

which type of speciation occurs in geographically overlapping populations?

Answer 27

sympatric speciation

Question 28

explain the concept of a ring species

Answer 28

a ring species is where two species within the same environment become to genetically different to interbreed, however they are connected by a geographical ring of species that cannot interbreed

Question 29

what is a reproductive barrier of sympatric speciation?

Answer 29

once the species have evolved they can no longer interbreed, as they are now too distantly related

Question 30

what is the difference between a prezygotic and a post zygotic barrier?

Answer 30

prezygotic barrier prevent fertilisation from occurring, postzygotic barriers prevents offspring from being fertile

Question 31

what does post zygotic barriers refer to?

Answer 31

the non viable offspring produced as a result of hybridisation between two species.

Question 32

what is hybrid inviability?

Answer 32

a postzygotic barrier. when the offspring dies as an embryo

Question 33

what is hybrid sterility?

Answer 33

when the offspring produced by hybridisation is unable to breed(sterile). this is a postzygotic barrier

Question 34

what is hybrid breakdown?

Answer 34

the first generation of hybrids (produced by two species interbreeding) is able to produce offspring. however, the second generation is infertile and cannot breed with similar crosses, or backcrosses to the parent species

Question 35

what are the three postzygotic barriers?

Answer 35

• hybrid inviability
• hybrid breakdown
• hybrid sterility

Question 36

what are the five forms of prezygotic barriers?

Answer 36

• habitat isolation
• behavioural isolation (eg. different mating calls)
• temporal isolation (mates in different seasons)
• mechanical isolation
• genetic isolation

Question 37

what is phyletic gradualism?

Answer 37

a slow but steady rate of evolutionary change. small changes accumulate steadily over long periods of time, resulting in speciation

Question 38

what is punctuated equilibrium?

Answer 38

the theory of evolution that species show no evolution for long periods of time, and then have rapid burst of speciation.

Question 39

which rate of evolution theory does adaptive radiation relate to?

Answer 39

punctuated equilibrium

Question 40

how can genetic variation be described on a gene level?

Answer 40

The average amount of loci that are heterozygous

Question 41

what does the harvey Weinberg equilibrium state?

Answer 41

that allele and genotype frequencies will remain fixed in a population provided there is no evolutionary influence

Question 42

which evolutionary force results in adaptive evolution? why?

Answer 42

• natural selection
• the other three can introduce harmful genes into a population, whereas only beneficial traits survive selection in natural selection

Question 43

what is frequency dependant selection?

Answer 43

where the fitness of a phenotype depends on how prevalent it is in a population