Lecture 4

Question 1

Macroevolution

Answer 1

-evolution above the species level: includes big patterns of evolution such as those seen in the fossil record

Question 2

Microevolution

Answer 2

-evolution within species and populations. Darwinian Natural Selection allows the study of microevolutionary mechanisms that underlie macroevolution

Question 3

Natural Selection

Answer 3

-process by which the variants of organisms in a population that are best adapted to the environment increase in frequency relative to less adapted variants over a number of generations

Question 4

Acceptance of natural selection

Answer 4

• not liked in 19th century
• mendelian gentics put down Lamarckian evolution and was consistent with selection
• Early 20th century biologists thought mutation was more important than selection
• 1930s-1940s population genetics shows role of selection, the “Modern Synthesis”
• Modern experiments directly show selection in action in living organisms

Question 5

Darwin’s 4 postulates

Answer 5

• basis of Natural selectin
• Individuals in a species are variable
• some variation is heritable
• more offspring are produced in each generation than can survive
• survival and reproduction are not random with respect to variation among individuals

Question 6

Ugly facts about nature

Answer 6

• Darwin recognizes that every environment is full of competition, predation, and death
• potential for selection is very strong

Question 7

Selective pressures

Answer 7

• birth—–>reproduction

- birth defects, disease, accident, parasites, predation, starvation, competition for mates, environmental extremes

Question 8

Selection

Answer 8

• normalizing: keeps population at present mean
• directional: change in favored state of population
• sorts variation and does not respond to environment: non random
• acts only on existing traits and depends on what genetic variability is available
• can’t achieve perfection in design

Question 9

Selection requires

Answer 9

• reproduction
• heredity
• variation in characteristics among individuals
• variation in fitness

Question 10

fitness

Answer 10

-probability that an individual will survive to reproduce

Question 11

origin of variation

Answer 11

-not understood at all by Darwin and was a weakness of selection theory until genetics re-discovered

Question 12

Mendel

Answer 12

• provided basic rules of heredity

- genes as particulate heritable units

Question 13

Timing of evolution

Answer 13

-evolutionary events may cover millions of years but the action must take place in each generation of an evolving lineage

Question 14

John Endler

Answer 14

• guppies
• sexual selection: males have bright blue spots
• predation: fish eat brightest guppies first so select for males with small spots

Question 15

Origin of Variation

Answer 15

• to be heritable, variation has to result from a genetic change in DNA-a mutation
• mutations occur without regard for the external environment or needs of the organism
• mutations have to change the phenotype to be subject to selection
• there are silent mutations aplenty. they accumulate in the genome=non-Darwinian evolution