Lecture 4 & 5 Evolution I

Question 1

what is the core theme of evolution?

Answer 1

• evolution accounts for the unity and diversity of life all life on earth is related because it evolved from a common ancestor

Question 2

what did Georges Cuvier hypothesize?

Answer 2

• species DO NOT change over time
• succession of life in Earth’s strata due to: catastrophe –> local extinction –> presence of ew fossils in the stratum
• after catastrophe, new species move into area –> new fossils in stratum

Question 3

what die Jean-Baptist Lamark hypothesize?

Answer 3

• species change over time (Evolution) due to INHERITANCE OF ACQUIRED CHARACTERISTICS
• use and disuse – heritable change : NO experimental evidence
• philosophically opposed to extinction

Question 4

what did Darwin hypothesize about the finches?

Answer 4

• species from south america had colonized the Galápagos and speciated on the islands

Question 5

what is natural selection?

Answer 5

• descent with modification
• process in which individuals with favourable inherited traits are more likely to survive and reproduce because of those traits
• in 1858, Alfred Russell Wallace developed a theory of NS similar to Darwin’s

Question 6

what did Darwin see on the Galápagos Islands?

Answer 6

• finches were different, but related species
• redundant forms from one place to another – common ancestry
• variation on a basic form within a region (descent with modification)

Question 7

what were similarities and dissimilarities of Darwin’s finches?

Answer 7

• similar appearance - but slightly different depending on habitat
• varied in use of food sources and way of feeding

Question 8

what does evolution explain? (patterns…)

Answer 8

• patterns of unity and diversity in living organisms

Question 9

what does descent with modification mean?

Answer 9

• the view that all organisms are related through descent from an ancestor that lived in the past

Question 10

what are observations 1&2 + inference 1

Answer 10

O 1: there is existing variation among individuals within populations
O 2: some of this variation is heritable
I 1: individuals whose inherited traits gave them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals – in the next gen, there will be more ind with that variation than previous

Question 11

what are observations 3,4,5 + inference 2

Answer 11

O 3: organisms produce many more offspring than are able to survive and reproduce themselves - potential to increase exponentially
O 4: most populations are relatively stable in size
O 5: resources are limited – competition is inevitable

I 2: unequal ability of individuals to survive and reproduce will lead to the accumulation of favourable traits in the population over generations - must compete, not all succeed (Thomas Malthus inspired)

Question 12

what is observation 6?

Answer 12

• species generally suit their environment

Question 13

what is a requirement for natural selection to act on variation? (2) (re: geno/phenotype)

Answer 13

• must be seen by enviro - expressed in phenotype (but sometimes phenotype is determined by enviro so it’s not heritable
• be heritable (caused by genotype)

Question 14

true or false: variation is random

Answer 14

• T

Question 15

what is a selective agent?

Answer 15

• component of natural environment that consistently causes differential survival or reproduction (ex: a/biotic factors)

Question 16

what is selective pressure?

Answer 16

• requirement for natural selection

- intensity with which the selective agent acts on a population to evolve

Question 17

is natural selection context independent or dependent?

is it reversible?

Answer 17

• dependent

- yes, it is reversible

Question 18

what is fitness?

Answer 18

• ability to survive, find a mate, produce offspring, and leave its genes in the next generation

Question 19

summarize the five steps of natural selection:

Answer 19

1. heritable variation: individuals vary in their characteristics (pheno) due to varied genetic makeup (geno)
2. resources are limited; more offspring than enviro can produce
3. some phenotypes with favourable traits will be better suited to survive and reproduce
4. over time, increase in proportion of favourable traits and genes coding for them in a population
5. adaptations to new enviro –> new species

Question 20

what evolves over time?

Answer 20

populations, NOT individuals

Question 21

what variation does NS act on?

Answer 21

EXISTING

Question 22

what is adaptation?

Answer 22

inherited characteristic of an organism that enhances its survival and reproduction in a specific environment

Question 23

why is increased and survival + reproduction not necessary sometimes?

Answer 23

all that that’s needed is greater reproductive success– ie more offspring produced regardless of it’s adaptive traits

Question 24

what are five pieces of evidence of evolution?

Answer 24

• observation of pop’n changes in real time - finches, antibiotic resistance
• artificial selection
• fossil record
• similarities b/w organisms
• biogeography

Question 25

what is homology?

Answer 25

- similarity from common ancestry | - related species have characteristics with similar underlying structures but different fxns

Question 26

what are homologous structures?

Answer 26

- anatomical resemblances representing variations on STRUCTURAL themes present in a common ancestor - comparative embryology reveals anatomical homologies are not visible in adult organisms - look at shared embryonic structures

Question 27

what are vestigal structures?

Answer 27

- remnants of features that served important functions in organism's ancestors

Question 28

what are molecular vestigular structures called?

Answer 28

- pseudogenes

Question 29

what are intermediate forms?

Answer 29

- forms that can be identified that appear to be ancestors of current species

Question 30

what are endemic species?

Answer 30

- species that are not found anywhere else in the world