Lecture 2: Evolution by natural selection

homology

a similarity that exists due to inherited trait of common ancestor

why homology constitutes evidence for evolution

species inherit traits from common ancestors

Vestigial traits

reduced or incompletely developed structure that has no function, or reduced function, but clearly similar to functioning structures in closely related species

why vestigial traits constitute evidence for evolution

reflect ancestry

Transitional forms

Fossils showing intermediate traits between ancestral and derived species

how transitional forms constitute evidence for evolution

show gradual change predicted by evolution

ring species

Populations connected in a geographic ring where neighboring populations can interbreed, but populations at the ends of the ring cannot.

why ring species constitute evidence for evolution

how speciation can occur gradually

first postulate of the theory of evolution by natural selection

There is variation in traits among individuals

second postulate of the theory of evolution by natural selection

Variation in traits is passed from parent to offspring (at least in part): heritability

third postulate of the theory of evolution by natural selection

More offspring are born than will survive to produce: some will reproduce more than others

fourth postulate of the theory of evolution by natural selection

Differential fitness (survival and reproduction) is not random: it is tied to variation in traits among individuals

adaptations

traits that increase fitness relative to those without it