Natural Selection

Question 1

General principle of Thomas Malthus

Answer 1

populations could grow exponentially but in practice they dont ; therefore they must be limited by incomplete survival or reproduction
-> competition bw members of same population to be in the part of population that survives and reproduces

Question 2

Mutation and Environment

Answer 2

Mutation is unrelated to demands of environment

Question 3

Fitness of an allele

Answer 3

-> fitness is defined as the number of offspring that organisms with a particular genotype or phenotype leave behind, on average, as compared to others in the population

Question 4

absolute / direct fitness

Answer 4

contribution of an individual to the gene pool of the next generation ( How many childrens a person has)

Question 5

relative / indirect fitness

Answer 5

the contribution an individual makes to the gene pool of next generation relative to contributions of other individuals ( eg more efficient food collection -> more power -> more eggs )

Question 6

How does natural selection change allele frequency?

Answer 6

natural selection increases the frequency of those alleles with high fitness and eliminates alternative alleles with low fitness
-> causes evolution by selecting favorable phenotypes

Question 7

adaptive evolution

Answer 7

evolution resulting in better match between organisms and their environment

Question 8

Linnean hierarchy

Answer 8

history of life with organisms at avrious levels related through descent from common ancestors

Question 9

genetic drift

Answer 9

random chance events cause allele frequencies to fluctuate unpredictably from one generation to the next
-> more likely to occur in small populations

-> GENES IN CURRENT ARE ONLY SAMPLE OF GENES CARRIED BY PREVIOUS GENERATION -> things get lost

Question 10

consequences of genetic drift

Answer 10

can lead to loss of genetic variation -> influences how effectively population is

Question 11

Founder effect

Answer 11

few individuals become isolated from larger population and establish a new gene pool different from source population

Question 12

Bottleneck effect

Answer 12

sudden change in environment drastically reduces size of population ( major disaster) ->one small part of population survives
-> by chance certain alleles are over/under represented or absent

Question 13

gene flow

Answer 13

• reduce genetic differences

traveling -> mating -> gene flow -> populations become more similar

Question 14

Mutation-selection-balance

Answer 14

mutation introduces genetic variation into population while selection reduces it
-> level of genetic diversity depends on the relative strength of the two

Question 15

Important point on natural selection and allele frequency

Answer 15

1 not necessarily organism but alleles with highest fitness will preserve
2 selection acts more directly on phenotype than on genotype

Question 16

Purifying selection

Answer 16

• the selective removal of alleles that are deleterious
• makes sure that deleterious mutations cannot take over a population and that any improved structures—once fixed in a population—are maintained as long as they are needed.
• > getting rid of the extremes

Question 17

Phenotypic plasticity

Answer 17

ability of one genotype to alter phenotype when exposed to different environments ( without altering its genome)

Question 18

Stabilizing Selection

Answer 18

intermediate phenotypes are more fit than extreme ones

• > individuals higher or lower the average having worse reproductive fitness
• > reduces variation and maintains status quo

Question 19

Directional Selection

Answer 19

one extreme phenotype is more fit than all the other phenotypes -> shifts overall makeup -> adaptation

Question 20

Disruptive Selection

Answer 20

occurs when condition favours variants at both extremes of a phenotyic range over intermediate phenotypes

Question 21

Heterozygote advantage

Answer 21

situation where individuals with one copy of a particular allele have higher fitness than individuals with either no or two copies
example sickle cell trait, which protects against malaria in heterozygotes, but causes a deadly disease in homozygotes

Question 22

negative-frequency-dependent selection

Answer 22

where a phenotype is associated with relative high fitness when it is rare but low fitness when it is common

Question 23

positive-frequency-dependent association

Answer 23

altruism, the more people it have, the better

Question 24

force of mutation

Answer 24

genetic mutation will persist when force of mutation is strengthened or that of selection weakened

Question 25

inconsistent ( unbeständig) selection

Answer 25

reason why variation may persist is if selection is inconsistent -> decreases particular allele in one year and increases it in another

Question 26

sexually antagonistic selection

Answer 26

optimal phenotype may not be same in male and female

Question 27

adaptationist stance / hypothesis

Answer 27

if some feature or behavior is commonly found in a type of organism then it is probably an efficient design solution to some problem the organism has faced -> multiple perspective model shows some evidences that can be met

Question 28

ultimate explanation

Answer 28

How a particular design increased ancestral fitness | -> more phenotype

Question 29

proximate explanation

Answer 29

explanation of the genetic mechanism that led to the formation of a new characteristic -> more genotype -> natural selection favours whatever proximate mechanisms produces the optimal phenotype

Question 30

example ultimate and proximate explanation : | Black tailed Prarie Dogs Alarm Calling

Answer 30

ultimate : call when kin is in danger - increases fitness | proximate: all kinds of proximate machanisms could produce the required effect

Question 31

Why can't organisms become perfect?

Answer 31

1 Time lags ( adaptation is constantly behind) 2 Selection can act only on existing variation -> fittest phenotype not always ideal phenotype 3 works on already existing traits by adaptation rather than building new structures from scratch 4 adaptations are often compromises ( eg penguins live on land and sea) 5 Chance events ( eg genetic drift) can ruin process 6 need of anear continous gradient of improvement

Question 32

hitch hiking trait

Answer 32

allele changes frequency not because it itself is under natural selection, but because it is near another gene that is undergoing a selective sweep and that is on the same DNA chain example : humans made foxes tame -> many other characteristic changed too

Question 33

3 ways to test an adaptionist hypothesis

Answer 33

1 Reverse Engineering and optimality models 2 Experimental MAnipulation and Experiments of Nature 3 Comparitive Evidence

Question 34

Reverse Engineering and optimality models

Answer 34

Reverse engineering : examine how it works , then come up with assumptions about what function would have led it to be deigned this way Optimality models: >>>>> not complete yet

Question 35

Experimental manipulation and experiments of nature

Answer 35

cmparing individuals with more and less of the characteristic

Question 36

Comparitive evidence

Answer 36

comparative method : skin colour should be associated to average amount of sunshine that population is exposed to

Question 37

sexual dimorphism

Answer 37

difference between male and female forms of same species

Question 38

sexual selection

Answer 38

natural selection on the ability to gain mates

Question 39

Bateman's principle

Answer 39

variability in reproductive success is greater in males than in females - > females have an upper limit when it comes to reproduction and males dont have it - > males maximize quantity while females spend long time choosing quality

Question 40

Intrasexual competition

Answer 40

example : fight between males | must weigh cost-benefit : even though fighting is risky -> benefit more access to more mates

Question 41

female choice and ornamentation

Answer 41

- seccond way to compete for extra females is by attractiveness

Question 42

the sexy son hypothesis

Answer 42

there is a genetic correlation between the preferene for the traits and the trait itself -> mating with a male who has a favorable traits means higher chance that own son has trait too

Question 43

the good genes hypothesis

Answer 43

females choose males with best traits , because these traits provide that they do well in general in current environment -> high quailty traitsshow higher quality in general ; not just to be more attractive but to survive better

Question 44

Intersexual competion

Answer 44

females choose a male | trade offs : cost vs benefits

Question 45

Reformulation of Batemans principle due to sex role revearsal

Answer 45

whichever sex invests less per episode of reproduction will have the larger variance in reproductive success and will therrefore compete for mates

Question 46

Extra-pair mating

Answer 46

female mates with males other than the social partner -> usually the extra mate is the ''good gene'' mate whereas their actual partner is of lesser quality but needed to raise the offspring

Question 47

alternative male reproductive strategies

Answer 47

1 wait in one colony and have extra pair matings, wairing for territory to become free 2roaming from colony to colony picking up occasional extra pair matings and no need for further investment

Question 48

Batemans principle in humans

Answer 48

males reproductive success tends to be higher than females but depends in environment and socital circumstances ( having several wives and money)

Question 49

Males parental investment compared to females

Answer 49

men : women should be fertile and produce fertile offsprings -> high value on physical appereance women: material resources of men are of great importance

Question 50

male short term mating

Answer 50

mating can be expensive for male but not necessarily -> choosy for long term relationships

Question 51

'just so' explanation

Answer 51

the opposite of adaptation -> logical story is not always the correct story!

Question 52

Two types of adaptation

Answer 52

1 Being adopted of an individual -> proper functioning in environment 2 Becoming adapted as an population -> increasing frequency of adapted individuals

Question 53

NS in terms of fitness

Answer 53

any consistent difference among phenotypycally different classes of organisms

Question 54

adaptation

Answer 54

better functioning = more offspring = higher fitness - an adaptation is a character that raises relative fitness of an individual - adapation has no evultionary effect unless phenotypes differ in genotypes

Question 55

What are mistaken views on adaptations?

Answer 55

1 all differences between populations are adaptive | 2 all characters of of organisms are adaptations

Question 56

adaptations are trade offs

Answer 56

benefits always come with costs

Question 57

Why is HW still relevant?

Answer 57

- > no need to look at adaptations etc | - > used to detect evoution