chapter 5

Question 1

how is evolution defined by biologists?

Answer 1

as change in allele proportion in populations

Question 2

what three factors are necessary for natural selection and what does each factor entail?

Answer 2

variations
these variations must be heritable and come from changes in genetics as a result of random mutation
these genetic variations much somehow impact an individual’s fitness

Question 3

what does random mean in context of mutations and what word might be a better substitute for random?

Answer 3

it means mutations which occur regardless of whether they are useful to the individual or not, a better word might be indifferent

Question 4

how do random mutations occur and what effects do most of them cause?

Answer 4

mutations come from dna replication errors and are mostly harmful or neutral

Question 5

what is fitness?

Answer 5

an individual’s probability of leaving offsprings/passing on their genes to next gen

Question 6

what is the relation of natural selection and randomness and what is a good phrase that describes it?

Answer 6

natural selection aka. filtering of mutated variants isn’t random/by change, rather mutation of variants which occur + get selected is random by change
“the non-random survival of random variants”

Question 7

how do new traits evolve?

Answer 7

all new traits are modifications of earlier features

ex. legs of tetrapods = modified fins

Question 8

what is a requirement for each stage of evolution/modification of an adaptive trait? what kinds of stages aren’t possible?

Answer 8

each stage must provide evolutionary benefits/increased fitness/increased average number of offsprings
stages can’t be temporary inconveniences/setbacks

Question 9

how does evolution of fitness correlate w/ aging? what is an exception

Answer 9

since increased fitness only cares abt increased reproduction, genes which re favoured during youth may become negative in old age
an exception might be genes which help female humans survive post menopause

Question 10

how does the phrase “for the good of the species” fit into the concept of adaption?

Answer 10

this phrase is false, adaptions only aim to increase fitness of individuals and will not nessecariliy be beneficial for the species as a whole

Question 11

how does the phrase “for the benefit of the species” fit into the concept of adaption? and what is an example supporting this relationship

Answer 11

this phrase is false, adaptions only aim to increase the fitness of individuals and will not necessarily be beneficial for the species as a whole and may even have negative effects on overall species pop
ex. male lions displace resident male lions of a pride they kill all unweaned cubs of previous male
this is reduces pop of lions, but increases individual male lion fitness as can immediately fertilize females which increases genes passed to next gen

Question 12

what is genetic drift?

Answer 12

genetic drift is where changes in frequency of alleles happens over time but not because of natural selection

Question 13

what’s the diff b/w natural selection and genetic drift?

Answer 13

unlike natural selection, genetic drift is completely random
these random changes happen regardless of benefits/detriments while selection always gets rid of harmful alleles/physical features

Question 14

how does genetic drift happen?

Answer 14

parents each have two copies of same gene and sexual reproduction randomly pairs up/passes down genes from parent to offspring
this means frequency of genes in each gen will be diff
new mutations may rise and fall due to random sampling

Question 15

what changes can and can’t genetic drift make?

Answer 15

it can’t evolve adaptions (ex. build wings, eyes) but I can evolve features which aren’t harmful or helpful like mutations in pseudogenes

Question 16

when is genetic drift strongest and how can this be negative?

Answer 16

genetic drift is more dominant in smaller pops
it can overpower natural selection and raise the frequency of harmful genes in a small pop
ex/ gacher’s disease in northern swedes, tay-sachs in canjuns, retinitis pigmentosa in tristan de cunha
might get rid of beneficial allele and fixate harmful alleles

Question 17

why is the success of artificial selection important?

Answer 17

it acts as evidence to support the occurrence of natural selection
ex. sometimes results of artificial selection coincide w/ natural selection
greyhounds which are artificially selected for speed resemble cheetah which have been naturally selected for speed

Question 18

what are the differences b/w artificial selection and natural selection?

Answer 18

natural selection happens much slower which is why there is such a large variation in domesticated species
good and bad traits are chosen based on human desire rather than natural environment/adaptation or increasing fitness
ex. svelte will turkeys are bread to have breasts so large males can’t mount females and have to be artificially inseminated, this wldn’t happen in wild as lowers fitness

Question 19

what is stabilization selection and when does it happen?

Answer 19

stabilization selection keeps species at optimum state (ex. optimum body size) and culls individuals which are outside that state (ex. too big or too small)

Question 20

what is microevolution?

Answer 20

small changes in onde or few features of an organism

Question 21

what is microevolution?

Answer 21

small changes in onde or few features of an organism

Question 22

what is macroevolution and why is it difficult to study and how do we make up for this?

Answer 22

transformation of one type of plant/animal into another, its hard to study since it can’t be observed within a human lifetime so ppl study fossil records to see how it’s occurred in the past

Question 23

what kind of species is best for observing natural selection?

Answer 23

species w/ short generations which are adapting to new enviros/enviro changes
ex. after a drought on the Galapagos finches which usually prefer small soft seeds had to turn to larger hard seeds for food
this caused natural selection to favour finches w/ bigger + stouter beaks
by following gen average beak size increased by 10%

Question 24

what kind of species is best for observing natural selection?

Answer 24

species w/ short generations which are adapting to new enviros/enviro changes
ex. after a drought on the Galapagos finches which usually prefer small soft seeds had to turn to larger hard seeds for food
this caused natural selection to favour finches w/ bigger + stouter beaks
by following gen average beak size increased by 10%

Question 25

which is the insect equivalence of colonization and how does this relate to natural selection?

Answer 25

insects which are host specific need to adapt to their hosts, switching from host to host is inspection version of colonizing new habitats
ex. soapberry bugs which colonize plants w/ larger fruit evolve larger beaks and vice versa for ones which colonize smaller plants

Question 26

what is duplication and what type of evolution is it related to?

Answer 26

duplication is related to evolution of biochemical features, its a mutation type where an ancestral gene and its descendants become duplicated along a DNA strand due to mistakes in cell division
once this happens duplicated genes can evolve to become separate pathways to perform separate functions

Question 27

what is an example of a biochemical feature which resulted from duplication and what is evidence of this?

Answer 27

ex.
fibrinogen occurs in all vertebrates as a blood-clotting protein and presumably evolved from a protein w/ a diff function in ancestral invertebrates who lacked clotting pathways
sea cucumbers are evidence of this since they are an invertebrate which branched from vertebrate lineage and contain protein that is not used for blood clotting but is related to blood-clotting proteins in vertebrates
most likely common ancestor of sea cucumber and vertebrates had genes (ex. non-clotting functions) which were coopted for a new function (working clotting system) due to evolution

Question 28

what’s a major diff b/w evolution in labs and evolution found in fossils and why is this diff important?

Answer 28

rates of changes found in labs and colonization studies are 500 (colonization studies) to 1 million (lab selection experiments) times faster than rates found in fossil record
at these rate a mouse shld be able to evolve to the size of an elephant in 10 000 yrs
this is important since it demos that changes/evolution found in fossil record can perfectly reasonably be explained to happen due to selection