UNIT 2 DAY 5 - EVOLUTION IN THE GALAPAGOS

Question 1

Selective argument

Answer 1

• if in each generation only a few organisms survive, and if organisms vary, and if survival is not random, but instead if influenced by the traits that vary, then a trait that makes survival more likely will be more common among the survivors than it was before mortality ensued

Question 2

Evolution argument

Answer 2

• if such an advantageous trait is more common among survivors, and if the trait is heritable, then it will also be more common among the offspring of the survivors, who then too will have a better chance of surviving
• each generation, the trait will increase in frequency in the species, and the species will change over time in ways that keeps it closely fitted to its environment

Question 3

Selection in Evolution arguments are

Answer 3

• both arguments are deductive
• flaw in deductive arguments –> lead to correct conclusions only if the premises are correct, scientists use deductions not to prove an argument but to make testable predictions

Question 4

Darwin’s finches

Answer 4

denied a starring role in the origin because he didn’t label them by island

Question 5

Daphne Major

Answer 5

small volcanic island in the galapagos about the size and shape of large sports arena

Question 6

Species Grants chose

Answer 6

medium group finches (geospiza fortis)
- chosen because it varied in traits (beak/body size)

Question 7

Medium Ground Finches (1975-1978)

Answer 7

• 1500 birds were colour-banded and measured for 7 external morphological characters
  -continuous records were kept of the banded birds and rainfall

Question 8

Rainfall levels in 1976, 1977,1978

Answer 8

• 1976 and 1978: 127 and 137 mm
• sufficient for production of plants, insects and finches
• 1977: 24 mm –> medium ground finches did not breed at all
• suffered 85% decline population
• seeds were scarce

Question 9

3 ways mortality of Medium Ground Finches was non-random

Answer 9

1. small seeds decline in abundance than large ones, resulting in a sharp increase in average size and hardness of available seeds
2. feeding behaviour changed
   - 1976 only 17% of feeding was on medium or large seeds
   - 1977 49% of feeding was on medium or large seeds
   - small birds had no food source because plant that produced small seeds died in the drought
3. Small seeds declined in abundance faster than large ones resulting in a sharp increase in average size and hardness of available seeds

Question 10

Geospiza fulginiosa

Answer 10

small ground finces

Question 11

Geospiza fortis

Answer 11

medium ground finches

Question 12

Geospiza magnirostris

Answer 12

large ground finches

Question 13

small beak

Answer 13

small seeds

Question 14

large beak

Answer 14

large seeds

Question 15

1977

Answer 15

• severe drought destroyed plant life, reducing the production of seeds on which medium ground finches feed
• mortality was no longer the result of hatching to many chicks, that they could not reproduce

Question 16

Did the finches evolve from the 1977 drought?

Answer 16

• yes, far few birds were alive in 1978 but those that were alive had deeper beaks
• natural selection occured increasing beak size from 8.8mm in 1976 to 9.8mm in 1978
  -parents with deep beaks will have offspring with deep beaks

Question 17

Grants tested Darwin’s Selection and Evolution Argument

Answer 17

• 2 step process
• mortality leads to selection on a trait
• the trait, if heritable, becomes more common in the next generation

Question 18

Darwin’s theory and Lamarck theory

Answer 18

• both involved both evolution of traits that adapted an organisms to its environment and heritability of those traits

Question 19

Lamarck theory of evolution

Answer 19

• individuals themselves evolve by developing adaptive traits during their lifetime, which then pass on offspring

Question 20

Darwin’s theory of evolution

Answer 20

• individuals are stuck with traits they inherit from parents
• individuals are selected, they either live or due based on whatever traits they possess
• populations evolve, they change overtime as traits favoured by selection becomes more common