5.1 evidence of evolution

evolution definition

cumulative change in the inheritable characteristics of a popn over a long period of time

evi for evolution (5)

1. homologous/analogous

2. fossil record

3. selective breeding

4. speciation

5. patterns of variation

homologous/analogous structures

analogous: same function, appears same, diff fundamental structure → diff ancestors but became similar bcos they perform the same function → convergent evolution. eg. fins of shark, dolphin, penguin.

homo: diff function, fundamental structure → same common ancestor → became adapted to diff environments → divergent evo, adaptive radiation. eg. human, horse, frog forelimbs — all pentadactyl structure

vestigial organs

organs that are small/have no function. theory is that vestigial organs existed in ancestral species, but as the species adapt the organs eventually lose their function → reduced in structure.

eg. appendix, wisdom tooth.

fossil records

rock strata: different layers of rock tt rep a diff period of geological time. fossils can be found in these layers. carbon dating to find the ages of rock strata & the fossils in them. transitional fossils can show intermediate forms.

evi? the sequence in which fossils appear reflects the sequence of evolution. the sequence links existing organisms to likely ancestors. eg. fossils show the evo of a whale from 4-limbed land animal to 2-limbed whale (documented by transitional forms).

selective breeding

eg. of pets/domesticated animals. when humans selectively breed animal species to enhance characteristics deemed desirable.

effectiveness of artificial selection: considerable changes over a v short period of time (compared to geological time).

can cause evo but is not evi that evo occurs by natural selection.

speciation

when 2 popns of a species become separated → reprod isolation → characteristics diverge → have recognisable differences over time.

eg, allopatric /sympatric speciation.

patterns of variation

continuous: cumulative differences, provides possible evi for the origin of new species by evolution.

discontinuous

dev of melanism

before ind rev: white moths had a selective adv, camouflaged better → selected for.

after ind rev: black soot coats the bark of trees. black moths had a selective adv → selected for.