M3.3

Question 1

Cenozoic Era

Answer 1

Age of Mammals
- Groups of giant mammals went extinct, allowing smaller species of mammals (dogs, horses, primates, elephants) to thrive in the absence of their primary predators
- Without dinosaurs, plant life thrived

Question 2

Levels of biodiversity

Answer 2

• Genetic diversity - total number of genetic characteristics in the genetic make-up of a species
• Species diversity - how many species are in an ecological community
• Ecological diversity - variation of ecosystems found in a region

Question 3

Allopatric speciation

Answer 3

• Parent population becomes separated due to physical barriers, preventing the flow of genes between the two populations
• Populations experience different selection pressures that favour different genotypes
• Over time this results in different genetic makeups that cause members of each species to be unable to interbreed fertile offspring

Question 4

micro-evolution

Answer 4

changes within a population over a short period of time
e.g. peppered moth

Question 5

macro-evolution

Answer 5

the accumulation of micro-evolution over a long period results in the formation of new species

Question 6

speciation

Answer 6

the formation of new species due to a combination of micro-/macro-evolution and change in environment

Question 7

Case study of macro-evolution: fossil record of horses

Answer 7

Sudden large changes in cheek teeth span between horses of the different geological eras is unsupported by evidence of transitional fossils → punctuated equilibrium

• Early Eocene: small, dog-sized mammals with 4-toed hoofs. Cheek teeth span was around 4.5cm
• Early Oligocene: fossils show cheek teeth span suddenly increased to 7.2cm. No evidence show transition between Eocene and Oligocene teeth spans
• Early Miocene: multiple cheek teeth spans occurring simultaneously shows radiation. This was because horses moved out into the plains and colonised different niches. Cheek teeth span jumped again from ~8cm-10 to 14cm between early and late Miocene
• Pliocene: more radiation can be seen from fossil record. One genus had cheek teeth span of 21.5cm, while another contemporaneous one had only 11cm.

Increases in cheek teeth span over 60 million years indicate a change in diet to become primarily herbivorous grazers

Horse evolved from a dog-sized mammal with four-toed feet to the much larger modern horse with a single hoof.

Question 8

Case study of common ancestor - Platypus

Answer 8

• Retains primitive traits- reptilian genes for egg-laying and venom
• Species on South America died out
• Southern variety (Tasmania) is larger than Northern (Australian)
• More specialised to aquatic lifestyle -smells underwater, detects electrical impulses of other creatures in the water, stable body temperature (radio telemetry)

Question 9

Radio telemetry (platypus)

Answer 9

Little body temperature variation.
From radio transmitters detecting body temperature e.g. freezing winter in Thredbo River.

Question 10

Radio tracking (platypus)

Answer 10

Uses radio transmitters to detect nocturnal activites.
Max 2.2 kilometres from the burrow, and the distance varied greatly within the study, as little as 0.4 kilometres.

Question 11

Molecular biology techniques (platypus)

Answer 11

DNA microsatellite sequences (genetic fingerprinting)-
the spur on male platypus’ increases in size during mating season is to compete for partners or territory.

Genetic makeup of platypus to determine gender. 52 chromosomes, with 4Y + 4X or 8X

Question 12

divergent evolution

Answer 12

When colonising species adapt to their new environment, resulting in differences between populations, and eventually evolution.
Often through isolation, no longer intermingles

Question 13

example of divergent evolution

Answer 13

• Darwin’s finches
• amphibian to mammal evolution due to death of the dinosaurs

Question 14

convergent evolution

Answer 14

When completely different species live in a similar environment have the same selective pressures applied to them. The unrelated organisms develop similar characteristics in response to experience similar selection pressures.

Question 15

evolutionary model: gradualism

Answer 15

Tiny variation in an organism that happens over a long time to make a better fit for its environment. This variation allows them to survive and thrive resulting in a slow and consistent process of change in the whole population

Question 16

evolutionary model: punctuated equilibrium

Answer 16

A species reacts to rapid change in the environment and dramatically adapts, then followed by a long period of no change (equilibrium) until the next environmental event.
e.g. fossil record of horses. In each era, there is a change of their cheek teeth size, indicating a change of diet that resulted in this change.

Question 17

example of convergent evolution

Answer 17

dolphins and sharks: fins, streamlined body shape and flippers
water rat and platypus: