Evidence for Evolution

Question 1

Explain how DNA hybridisation provides evidence for evolution

Answer 1

DNA hybridisation is a technique that allows scientists to determine how closely two organisms are related. Because DNA unravels when heated, when scientists mix the DNA of two species they can determine how closely related two species are based on the temperature the two strands separate. Closely related organisms have DNA that is similar and hence bonds strongly together requiring higher temperatures to separate. This provides evidence for a shared ancestry.

Question 2

Explain how Comparative Anatomy provides evidence for evolution

Answer 2

homologous structures suggest evolution from a common ancestor: an example of divergent evolution. One common homologous structure is the pentadactyl limb (you know the joints hopefully). The pentadactyl limb is found in organisms such as humans bats, and whales. Each is slightly different as they have adapted to best suit their environment. Eg. whales have short square shaped bones to create a flipper shape for optimal movement in aquatic environment.

Question 2

Explain how comparative embryology provides evidence for evolution

Answer 2

Study of anatomical development in embryonic forms shows similarities suggesting a common ancestor across different species. Early embryo’s possess similarities such as: gills, spinal chord and a “tail” structure, some of which disappear as the organism develops.

Question 3

Explain how biogeography provides evidence for evolution

Answer 3

Distribution of similar organisms follows movement of tectonic plates. As plates in gondwana moved apart similar organisms were subjected to different environments and had to adapt. eg. presence of flightless birds across continents (emu, kiwi, cassowary, ostrich) location of plates = different selection pressures = different size colour and feathers.

Question 4

Explain how paleontology provides evidence for evolution

Answer 4

As selection pressures create gradual changes in organisms, “transitional forms” are formed depicting an intermediate form between a past and contemporary organism. eg. archeopteryx transitional form between dinosaur and bird possessing both reptilian and avian characteristics.

reptilian: teeth, claws on wings, long tail
Avian: feathers and wings

Question 5

What are the two techniques to date fossils

Answer 5

Absolute dating (numerical value): radiocarbon dating (c14) measures amount of c14 and by comparing it to its half life we are able to correlate how much is present to how much has decayed and how long it took thereby measuring the approximate age of the organism.

Relative Dating (compared age): comparing positions of rock strata, by law of superposition younger ones above older ones below.

Question 6

What is a modern example of evolution

Answer 6

red-bellied black snake: ones with larger mouths tend to eat cane toads, however they die. Thus having a small jaw becomes favourable and small heads are more common

Antibiotic resistance: the antibiotic serves as a selection pressure and organisms with resistance have the favourable characteristics and are able to survive and reproduce. These resistant traits become more common within a population until the bacteria is resistant to a level of antibiotics.