UNIT 2 DAY 6 - EVOLUTION IN THE GALAPAGOS

Question 1

Darwin’s 3rd big idea

Answer 1

• divergence of character and the origin of species

Question 2

Explain how species change overtime in ways that fit them to their environment

Answer 2

• Darwin’s initial explanation for splitting involved geographic isolation

Question 3

Why do species split and diverge as they change, allowing us to classify them into groups within groups?

Answer 3

divergence of character

Question 4

divergence of character

Answer 4

• divergence arises from natural selection
• favouring those individuals that, by differing the most from the average member of their species, suffer the least from competition with their neighbours and emerge more often successfully from the struggle of existence

Question 5

intermediates

Answer 5

• Darwin said that they will go extinct, then diverge due to competition will split one species into 2

Question 6

Directional selection

Answer 6

• shifts overall makeup of a population by favouring one extreme over the mean and over the other extremes
• drives all of the population in one direction towards one extreme of a trait

Question 7

Disruptive selection

Answer 7

• shifts the overall makeup of a population by favouring both extremes over the mean
• population moves towards opposite extremes individuals at the extremes suffer less competition

Question 8

Stabilising selection

Answer 8

• prevents the population from evolving by favouring the mean of a trait over either extreme
• prevents evolution
• population will not change over time because selection favours mean trait

Question 9

Evolutionary tree

Answer 9

• shows how divergence of character creates new species
• gaps are extinctions

Question 10

reproductive isolation

Answer 10

• the inability to interbreed successfully even when living side by side
• and reproductive isolation is crucial because, until it evolves, whenever characters begin to diverge within a population, the divergence will be erased by interbreeding between those with the extremes characters and those in the middle

Question 11

missing from Darwin’s idea of divergence

Answer 11

• doesn’t explain reproductive isolation

Question 12

niche

Answer 12

• a role taken by an organism within its community
• make up of the habitat in which organisms lives, activities, resources

Question 13

habitat

Answer 13

physical place that a species inhabits

Question 14

Wolf spider

Answer 14

• lives in woodlands, hunts and reproduces
• must be able to do these things in order to survive and stay in the niche

Question 15

Limitations of ecological niches

Answer 15

• limited number of individuals can be in each niche –> natural selection fixes this –> reproductive rates makes no difference, only a certain number can be supported and live (competition and limited resources)

Question 16

Reproductive efforts are not determined

Answer 16

• by niches because the way an animal breeds has very little to do with how many there are
  –> makes no difference in the eventual size of the population
  –> that lives in niche is set and independent of how fast a species makes babies

Question 17

population niches determine

Answer 17

• size
• the number is fixed and is likely to stay constant
• established when the niche was created

Question 18

Gause’s experiments (niche partitioning)

Answer 18

1. placed paramecium in tubes, let grow and then introduced another species –> first species in tube always survived
2. changed water frequency (as paramecium have a chemical they put in water that is toxic to other chemical) –> reverse results: first species
   survived
3. later observed separation of species in same tube. One lived on top and the other on the bottom (avoiding competition)

Question 19

Gause’s results (niche partitionising)

Answer 19

• how does losing species exist?
• natural selection designs differ species (via adaptation) to AVOID competition –> find their own niches (where it can’t be out competed)

Question 20

Gause’s general principle (exclusion principle)

Answer 20

• that no 2 species could live together indefinitely in the same niche

Question 21

Common cormorant and shag

Answer 21

• David Lack used for the first test of the exclusion principle
• lived in same niche
• both are sea birds: eat different foods, both hunt different places, live in different places
• avoid competition

Question 22

Five New England Warblers

Answer 22

• Studied by MacArthur
• 5 species all living in same area and eat same food
• found they have different hunting techniques and live in different areas of the trees
• hunting methods ensured that each caught a different proportion of total crop

Question 23

Herd of grazing species on the plains of Africa

Answer 23

• feed on different grasses
• all eat what is best suited for them
• big game animals avoid competition by specialising in the kind of food they take

Question 24

small ground finches lived

Answer 24

• alone on the island of los hermanos

Question 25

2 species live together on

Answer 25

• santa cruz

Question 26

Character displacement

Answer 26

• 2 species with overlapping resources use evolve to avoid competition
• sharing is the automatic, unplanned and unthinking result of selection favouring those birds that suffer the least from competition

Question 27

character release

Answer 27

• 2 species with non-overlapping resource use (with distinct niches) will broaden their niche use if they move to places where their sister species is absent
• individuals with traits that would overlap with the sister species now have the opportunity to exploit unused resources and are thus favoured by selection

Question 28

Intraspecies competition

Answer 28

competition between individuals of the same species

Question 29

interspecies competition

Answer 29

• competition between members of 2 different species

Question 30

Why G. fortis on Daphne Major was considered a classic example of character release?

Answer 30

• absents of small finches and no competition the medium ground finches evolved to an unusually small beak/body sizes

Question 31

Situation on Daphne changed in 1982

Answer 31

• new arrival of competitor species
• between 1973-1982 large ground finches visited the island for short periods in the dry season but never bred
• late 1982, breeding populations was established by 2 females and 3 males
• large ground finches depleting food supply
• grants predicted it to cause a selective shift in medium ground finches

Question 32

Grants predicted of selective shift occurred in 2004

Answer 32

• drought in 2004: large ground finches had large enough population to create competition for medium ground finch ( out compete for larger seeds)
• 2004 to 2005 drought: beak size of medium ground finches decreased due to limited resources and competition –> large ground finches were out competing larger beaked medium ground finches

Question 33

Directional selection 2004-2005:

Answer 33

small and medium beaks were favoured

Question 34

3 things that affects survival

Answer 34

• age
• size
• sex

Question 35

selectional differential in 1977-2004

Answer 35

• 1977 selection differentials are large and positive for most traits favouring large beaks/body size
• 2004 selection differentials are large and negative for most traits favouring small beak/body size

Question 36

response to selection for next generation

Answer 36

• because of high heritability of beak size we would expect strong directional selection against large beak size
• observed in 2005