UNIT 2 DAY 6 - EVOLUTION IN THE GALAPAGOS Flashcards
1
Q
Darwin’s 3rd big idea
A
- divergence of character and the origin of species
2
Q
Explain how species change overtime in ways that fit them to their environment
A
- Darwin’s initial explanation for splitting involved geographic isolation
3
Q
Why do species split and diverge as they change, allowing us to classify them into groups within groups?
A
divergence of character
4
Q
divergence of character
A
- 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
5
Q
intermediates
A
- Darwin said that they will go extinct, then diverge due to competition will split one species into 2
6
Q
Directional selection
A
- 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
7
Q
Disruptive selection
A
- 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
8
Q
Stabilising selection
A
- 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
9
Q
Evolutionary tree
A
- shows how divergence of character creates new species
- gaps are extinctions
10
Q
reproductive isolation
A
- 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
11
Q
missing from Darwin’s idea of divergence
A
- doesn’t explain reproductive isolation
12
Q
niche
A
- a role taken by an organism within its community
- make up of the habitat in which organisms lives, activities, resources
13
Q
habitat
A
physical place that a species inhabits
14
Q
Wolf spider
A
- lives in woodlands, hunts and reproduces
- must be able to do these things in order to survive and stay in the niche
15
Q
Limitations of ecological niches
A
- 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)
16
Q
Reproductive efforts are not determined
A
- 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
17
Q
population niches determine
A
- size
- the number is fixed and is likely to stay constant
- established when the niche was created
18
Q
Gause’s experiments (niche partitioning)
A
- placed paramecium in tubes, let grow and then introduced another species –> first species in tube always survived
- changed water frequency (as paramecium have a chemical they put in water that is toxic to other chemical) –> reverse results: first species
survived - later observed separation of species in same tube. One lived on top and the other on the bottom (avoiding competition)
19
Q
Gause’s results (niche partitionising)
A
- 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)
20
Q
Gause’s general principle (exclusion principle)
A
- that no 2 species could live together indefinitely in the same niche
21
Q
Common cormorant and shag
A
- 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
22
Q
Five New England Warblers
A
- 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
23
Q
Herd of grazing species on the plains of Africa
A
- 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
24
Q
small ground finches lived
A
- alone on the island of los hermanos
25
Q
2 species live together on
A
- santa cruz
26
Q
Character displacement
A
- 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
27
Q
character release
A
- 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
28
Q
Intraspecies competition
A
competition between individuals of the same species
29
Q
interspecies competition
A
- competition between members of 2 different species
30
Q
Why G. fortis on Daphne Major was considered a classic example of character release?
A
- absents of small finches and no competition the medium ground finches evolved to an unusually small beak/body sizes
31
Q
Situation on Daphne changed in 1982
A
- 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
32
Q
Grants predicted of selective shift occurred in 2004
A
- 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
33
Q
Directional selection 2004-2005:
A
small and medium beaks were favoured
34
Q
3 things that affects survival
A
- age
- size
- sex
35
Q
selectional differential in 1977-2004
A
- 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
36
Q
response to selection for next generation
A
- because of high heritability of beak size we would expect strong directional selection against large beak size
- observed in 2005
