T6

Question 1

phylogeny tree

Answer 1

before darwin, there was a hierarchal structure that life had a natural order, however Darwin showed a different approach using a phylogeny tree
- this layout helps us see how closely related species are and the common ancestor between them

• the more recent the common ancestor between two species, the more closely related they are

Question 2

Darwin

Answer 2

he claimed that species are not fixed, species change throughout time, and the present day species are descendants from ancestral species and that these ancestral species are different from modern species

Question 3

1st inference of natural selection and adaptive evolution

Answer 3

observation 1 = Populations can potentially increase rapidly
Ob 2 = population are actually quite stable
ob 3 = resources are limited

therefore if there is an increase in individuals in a population than what the environment can support, this leads to a struggle for existence and competiton - necessary for natural selection

Question 4

2nd inference of natural selection and adaptive evolution

Answer 4

ob 4 = members of a population vary and are genetically diverse
ob 5 = some variation is hertiable

there individuals with characteristics that give them a greater probability of surviving and reproducing means more successful

Question 5

3rd inference of natural selection and adaptive evolution

Answer 5

this all leads to a gradual change in characteristics in a population with allele frequency changing over time

Question 6

how natural selection works

Answer 6

Individuals with longer beaks more likely to get more food and so will be more successful, fitter, and can reproduce more,

the trait for long beaks has a genetic basis (heritability) then offspring will have longer beaks and this will continue until frequency change in alleles, and evolution.

Because longer beaks are fitted to the environment, see adaptive evolution = birds are now more adaptive to environment

Question 7

requirments for natural selection

Answer 7

any character can evolve given
- varies in population
- variation is heritable
- affects the genetic contribution/fitness of an individual

Question 8

result of natural selection

Answer 8

adaptive evolution
the individuals are now more adaptive to the environment so more likely to survive

Question 9

EVIDENCE FOR EVOLUTION

Answer 9

EFE

Question 10

EFE : hidden similarties

Answer 10

homology between species that must come from a shared ancestor
e.g. pentadactyl limbs of different species all show very similar bone structures where the differences are only due to adapting to different environments (adaptive evolution)

Question 11

EFE: Homology in development stages

Answer 11

very different organisms share similar developmental stages

this shows that these organisms that share this have evolved from a common ancestor that had this basic development stage and is has changed slightly to each organism as evolved

Question 12

EFE: Homology in genetic code

Answer 12

genetic code is universal between all organisms, which creates a strong argument for a shared common ancestor

Question 13

EFE: homologies in different traits

Answer 13

this shows similar patterns which can only be explained by descendent of modification , using a phylogeny tree to look at this

Question 14

EFE: imperfections in structure

Answer 14

organisms are not built from scratch so can see the evolutionary history present in structures of species even when it doesnt make sense

e.g the recurrent laryngeal nerve in giraffes which goes via the heart, which doesnt make much sense

Question 15

EFE: power of artificial selection

Answer 15

supports the role of evolution because we have caused change

Question 16

EFE: Descent with modification implies missing links

Answer 16

fossils are starting to fill in these missing links where we would expect them to show if between organisms that are sharing a common ancestor

Question 17

EFE: experimental evolution with e.coli

Answer 17

identified the genetic change/mutation in these e.coli over time to test the evolutionary theory

rapid evolution in pests due to changes in environments , those individuals’ resistances to meds = more adaptive so more likely to survive and reproduce

Question 18

constraints of evolution

Answer 18

sometimes an evolutionary change that would be successful does not happen because
- variation was not available
- the benefit trait must have outweighed everything else and wouldn’t have made the other traits already present in the individual worse.

Question 19

if there is no heritable components and selective advantages with a specific trait, what will happen?

Answer 19

it will not pass on to the offspring and natural selection will not occur

Question 20

if there is no reproductive advanatge despite there being variation, what will happen?

Answer 20

if there is no reproductive advantage e.g hand size for using phones, then the trait is unlikely to be selected

Question 21

for a trait to be selected, it must be

Answer 21

heritable
have a reproductive advantage