Lecture 14: Macroevolution

Question 1

Macroevolution 2 types:

Answer 1

• gradualism (smooth branches for tree)

- punctuated equilibrium (block lines, right angles and straight lines)

Question 2

Gould & Eldridge:

Answer 2

punctuated equilibrium;
1) Fossils stay the same for millions of years
2) when new groups appear intermediated are often lacking.
SUGGESTS…speciation has ben rapid

Question 3

why do gaps occur in the fossil record?

Answer 3

1) Fossilisation relies on sédimentation. sedimentation is spatially uncommon
2) Even where sedimentation occurs it is not continuous (only 1-10% of tie represented)
3) Even where sedimentation occurs, fossilisation doesn’t always happen

Question 4

Solnhofen limestone

Answer 4

upper jurassic 140 mya

• fossils found where those from flying species
• this is because the lagoon/water was an anoxic bed = no O2 present
• organisms would die & fall into water, nothing to decompose or scavenge them so fossils were formed

Question 5

Can selection alone explain the pattern of evolution? need to explain..

Answer 5

1) rapid change

2) periods of stasis

Question 6

explanation of rapid change:

Answer 6

Homo erectus - 920ml brain –20,000yrs–> Homo sapiens - 1400ml brain. 30% increase of brain size, 20,000 is considered rapid! For this speed of evolution, selection need only eliminate 1 in 500 individuals per generation

Question 7

explanation of stasis:

Answer 7

organisms such as Nautilus & Lingula that have not changed for millions of years. - little/ no change to their environment, so no evolutionary change is beneficial –> STABILISING SELECTION (EXTREMES)

Question 8

Patterns of evolution:

Answer 8

• Convergent evolution

- Adaptive radiation

Question 9

convergent evolution:

Answer 9

e. g. Pangolin, Aardvark, Anteater, Echidna
- all eat ants and termites
- are toothless, relatively long extended snouts & long sticky tongue.
- BUT all from different areas of earth. No recent common ancestor

Question 10

Adaptive radiation:

Answer 10

• A single species undergoes speciation to produce a large number of species adapted to a variety of habitats.
  1) evolution of a character that allows exploitation of a new environment e.g. amniote egg (reptiles)
  2) reduction in competition from other groups
  a) mass extinction
  b) colonisation (change in climate;continental drift;chance colonisation)