Evolution Mechanisms
Evolution Mechanisms
Evolution Mechanisms
Evolution
Greek
philosophers
such as
Anaximander
proposed that “life
changes over
time”,
2600 years ago!
In many textbooks, there is confusion
about some terminology.
A species is:
▪ http://learn.genetics.
utah.edu/content/var
iation/related/
Anatomical Studies
1. Homologous- modified structure seen
among different groups
▪ Similar in structure & function
▪ Ex: forelimbs-reptiles, mammals, birds
2. Analogous- similar in
function, different
structure
ex: insect vs bird
wing
3. Vestigial- structure
once used but not now
ex: appendix in humans
eyes of sightless
species
Mechanisms of
Evolution
The Galapagos Islands:
Darwin notes:
▪ Island species varied from the
mainland species, and island-to-island
▪ Each island had either long or short
necked tortoises depending on the
island's vegetation
The Galapagos Islands:
▪ Darwin noted:
▪ Finches: Bill shapes are adaptations
to different means of gathering food.
▪ Galapagos finch species varied by
nesting site, beak size, and eating habits
Outine: 4 Mechanisms of
Evolution
1. Natural Selection
2. Mutation
3. Migration/Gene Flow
4. Genetic Drift, Founder effect, and
Bottlenecking
#1 Natural Selection:
Natural Selection –
A gradual, non-random process by
which biological traits become either
more or less common in a population
Genetic Variation: Genetic
differences within a population.
▪ http://learn.genetics.
utah.edu/content/var
iation/related/
Anatomical Studies
1. Homologous- modified structure seen
among different groups
▪ Similar in structure & function
▪ Ex: forelimbs-reptiles, mammals, birds
Physical Barriers Cause Speciation:
1. Allopatric Speciation aka Geographic Isolation
– a physical barrier divides a population
Geographic Isolation
▪ Common ancestor of all canines (wolves, dogs, foxes)
believed to have been part of a single population on
Pangaea.
▪ After the continents split, isolated populations adapted in
various ways that coincided with their habitats.
▪ This process known as geographic isolation can lead to
new evolved species (or speciation!)
2. Sympatric Speciation aka Reproductive
Isolation – developing different mating seasons,
mating rituals, and reproductive structures