Evolution of cells

Question 1

drives evolution of adaptation

Answer 1

natural selection

Question 2

complex traits are

Answer 2

adaptations

Question 3

drives the evolution of complex traits

Answer 3

natural selection

Question 4

makes 5% of the body weight
uses >25% of body’s energy

Answer 4

the brain

Question 5

why does naturak selection favors the brain?

Question 6

why are complex, energetically expensive traits maintained by natural selection?

Answer 6

• fitness benefit
• outweighs
• fitness cost

Question 7

fitness

Answer 7

measure as reproductive

Question 8

accounting for human brain size

Answer 8

• fitness costs
  1) cosumes 25% of body energy
  2) the locus of psychiatric illnesses
  3)?
  4) big surface are for injury

Question 9

fitness benefits

Answer 9

1) communication?
- other animals can communicate; what sets humans apart?
- language, pattern recognizition
2) capacity to live in large functioning society?
- impulse control; large brain unlocks abstract thinking which can lead to moral system, embodied institutions, divisions of labor
3) critical thinking/reasoning?
- tool making? ability to do math?
-

Question 10

natural selection favors eduacted women not producing enough offspring?

Answer 10

no

Question 11

what is sex?

Meiosis

Answer 11

producing of gametes and reduction in ploidy level

Question 12

what is sex?

recombinations

Answer 12

shuffling of alleles among homologous chromosomes

Question 13

what is sex?

fusion of male and female gametes

Answer 13

how do we determine if a gamete is male or female?

Question 14

what is sex?

production of…..zygote (offspring)

Answer 14

genetically unique

Question 15

asexual reproduction involves

Answer 15

cloning

Question 16

sexual reproduciton

Answer 16

producing a hydbrid

Question 17

sex evolved once

Answer 17

~2.5 bya (life evolved ~3.5 bya) in early eukaryotes. (evidence for single origin :shared mechanisms of meiosis)

Question 18

evolution of sex in unicellular organism

Answer 18

• chlamydomonas: single-celled eukaryote
• mostly haploid & reproduces clonally
• but…… starvation/stress triggers sexual reproduction! (meiosis and fusion lead to diploid cust stage)

Question 19

evolution of sex in multicellular orgaism

Answer 19

• invertebrates
• cnidarians: many feature both asexual and sexual reproduction insects: most reproduce sexually; some feature both asexual and sexual reproduction- cyclical parthenogenesis and sex when stressed

Question 20

fish/amphibian/reptiles

Answer 20

• most species sexual
• asexual reproduction (parthenogesis) secondarily acquired in a few sexual species
• mammals/ birds: only sexual reproduction

Question 21

why is sex interesting to biologist?

Answer 21

apparent paradox
- sexual reproduction is widespread in eukaryotes (especially complex multicellular eukaryotes)but it carries

Question 22

costs of sex?

Answer 22

time consuming and risky

Question 23

courtship

Answer 23

mate search, overcoming prezygotic and postzygotic barrierd take time. secondary sexual characteristics can make an organism vulnerble to predation

Question 24

sexual selection and natural selection difference?

Question 25

risk of dieses transmissions

Answer 25

between sexual partnerr+ risk of transmittiong harmful recessive allele to offspring

Question 26

genetic recombination

Answer 26

breaks up good gene combinations (coadapted gene complexes) (but it can also assemble good gene combinations)

Question 27

cost of male

Answer 27

if female reproductive output is the same in a sexual and asexual, them asexuals will increase at 2x the rate od sexuals
sex=2 fold cost to fitness
therfore sexual reproduction must offer a > 2 fold benefits to fitness

Question 28

asexual populations

Answer 28

mutation is the main source of variation. Clones are genetically identical;
- “wait time” for evolution of benefivial allleles is longer in asexuals
- adaptation to new enviroments in aseual populations may be slower then in seuxally reproducing populations (counterexamples?)

Question 29

muller’s ratchet

Answer 29

most mutations that affect phenotype are deleterious
- clonal population can not purge harmful mutations through recombination
- irreversible fitness decline in asexuals

Question 30

sexual reproduction

Answer 30

• mutation and recombination are both important sources of variation. Recombined offspring are genetically variable
• “wait time” for evolution of beneficial alleles is longer in asexuals
• recombinations can help assemble beneficial alleles and break apart deleterious alleles
• sexual can purge low fitness aleles through recombination and mantain higher average fitness in population

Question 31

average fitness/reproductive output (all else equal)

Answer 31

penefits asexual reproduction

Question 32

what ecological factors/selective pressures explain sexual reproduction?

Answer 32

• coevolutionary arms race between hosts and parasites
• new zeland snails vs. trematode parasites
• observation: populations contain mix of males, females and asexual females
• question: sexually reproducing snails should be more common in areas with higher infection rates.
• result: can predict frequency of males based on infection data
• natural selection favors high frequency