14/ macroevolution

Question 1

problem with determining rates of evolution

Answer 1

• fossil record generally lacks transitional forms - fossilisation is rare, esp for short lived species
• new taxa appear abruptly in fossil record
• sudden changes, then periods of stasis

Question 2

punctuated equilibrium theory by gould and eldredge

Answer 2

• rates of evolutionary change between stasis and speciation are different
• different processes at work - speciation took place in small pops and was not under influence of nat selec
• speciation evolution is faster than stasis
• not fully accepted

Question 3

example of how selection can explain rapid evolutionary change

Answer 3

• homo erectus had brain size of 920ml, the 20,000 yrs later homo sapiens have 1400ml brain
• big jump
• for this speed, only 1 in 500 small brains need to be removed from pop per gen - possible

Question 4

how is stasis compatible w selection

Answer 4

• if selection pressures do not vary greatly over time then net change should be minimal - stabalising selection

Question 5

actual difference between apparent stasis and divergence in terms of changes in traits

Answer 5

• stasis: looks like a zigzag on graph, similar start and end point but fluctuations in traits nevertheless - change is happening, its just reversed later
• divergence: bigger net change. sustained directional change

Question 6

evolution: divergent vs convergent

Answer 6

• divergent: lineages split and separate
• convergent: lineages that are not closely related evolve similar adaptations bc they live in similar environment

Question 7

ecomorphs: what are they, example - islands

Answer 7

• organisms (can be in same species) that evolve similar traits due having similar habitats
• yet occupy distinct microhabitats so are morphologically and behaviourally distinct
• anolis lizards - 6 ecomorphs
• each island has a representative from each ecomorph - evolved similar traits based on similar habitats

Question 8

adaptive radiation

Answer 8

• evolution within a rapidly multiplying lineage
• requires differentiation of single ancestor into multiple species
• variation in morphological traits that allow exploitation of range of environments
• caused by ecological opportunity - lack of ecological constraint, fill niches created by other species going extinct

Question 9

hawaiian honeycreepers

Answer 9

• diversified across hawaii
• occupy almost all habitats - different morphologies

Question 10

morphological expansion of acanthomorpha

Answer 10

• spiny finned fish
• low diversity before cretaceous-palaeogene
• expanded after extinction of non-acanthomorph competitors, into their niches