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Lecture 6

ANT203Y1 Lecture Notes - Lecture 6: Sickle-Cell Disease, Blood Transfusion, Daphne Major


Department
Anthropology
Course Code
ANT203Y1
Professor
Julia Gamble
Lecture
6

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Lecture 6: Natural Selection and The Origin of Species
A few core concepts:
Culture very pronounced in humans, but observable in other species
Niche:
environment that an organism interacts with
can be specific or general
defined by area they live in, what they eat, when they are active
can be symbiotic relationship
Natural Selection:
Variation: if everyone was the same, there would be nothing change
Allows for selection (some individuals have to be more reproductively successful)
Selective agent:
changes how an individual is likely to survive or be viable
Types of natural selection:
Balancing: similar to stabilizing but subtly different
involves discontinuous traits
hetero advantage: eg. Sickle cell
if that environment wasn't there, it would be detrimental
Stabilizing: extremes ones selected against so we move toward center and center becomes more
common
Directional: trait that goes from low to high frequency (eg. Human skin tone)
Disruptive: push the curve in one direction
maybe due to an environmental change (slightly less extremes are selected for)
can lead to 2 different groups (can diversify an originally single population)
Finch video:
Grant study:
Daphne major island: studying galapagos finches
Charles Darwin wrote about it initially (islands rose less than 5 mya)
15 species of finches all together in diff islands
DNA shows that all finches are more related to each other than any one particular than in
the mainland
Therefore, one species came from the mainland and then evolved into the rest 15
In 1977, a bad drought happened
now only harder, bigger seeds are left behind so birds with the smallest beaks have the
most difficulty (80% of the medium ground finches died)
the larger the beak, the higher the chance of surviving the drought
the offspring of the survivors had much larger beak size
In 1983, it became too rainy, so much vine that it covered cactus
now with drought 2 years later, only smaller seeds remained so the larger beaked birds
were having mad difficulties, so smaller beaked survived (offspring had smaller beaks)
opposite direction of evolution
Why cant diff finch species mate with each other?
They have diff mating behaviour (different mating calls/songs: males only responded to
songs of their own species)
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