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Lecture 2

BIOB51H3 Lecture Notes - Lecture 2: Exaptation, Heritability, Macroevolution

Biological Sciences
Course Code
Maydianne Andrade

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Evolution by Natural Selection
o This theory is captured by 4 postulates
1. Individuals within populations are variable
Variation exists in almost every measurable characteristic in every species
2. Some of these variations are passed on to offspring (are heritable)
3. Many more offspring are produced than can survive and reproduce
We know this through deduction and observation
o Observation
Predation and parasitism
Catastrophic events
Habitat/food limitation
4. Survival and reproduction are not random
Individuals with favourable traits will produce more offspring over their
lifetime than individuals with less favourable traits
Lamarck vs Darwin
o Lamarck
o Individuals have to change and adapt to their environment
o Darwin
o Individuals are sorted
Darwinian Fitness
o The ability of organisms to survive and reproduce in their environment relative to others
in the same population
Favourable Traits = Adaptations
o Traits that increase the ability of an individual to survive and reproduce relative to
others without the trait
o Adaptations are traits that lead to increased fitness
o Adaptations may have a different function now than it did in the past (or it may have
the same function)
o A type of adaptation
o A trait that served a different function in the past from its current function
o Also known as a co-opted trait
Natural Selection
o Definition
o Differences in the average reproduction of individuals with different phenotypes
in a population
o What type of traits are favoured by natural selection?
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