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EVOLUTION
What is Evolution?
Change in allele frequencies (the gene
pool) over time in a population
Biological change on a timescale of
generations

Individuals change, but only populations
evolve
What does evolutionary theory explain?
Adaptations


Just about any feature on an organism is an
adaptation – most of the things you think of
By definition: inherited features of organisms
that fit life habits, allowing them to survive and
reproduce
Biodiversity

The diversity and number of species on earth
All those living things on earth-- the whole
“shootmatch”
Natural Selection
a.k.a. “survival of the fittest”
Broken down into four parts
Natural Selection
1. Individuals in a
population vary in their
traits
2. Some of these
differences are
heritable-they can be
passed on from parent
to offspring.
Natural Selection
3. Many more offspring are produced than
can survive
only some will
survive long
enough to
reproduce, and
some will produce
more offspring
than others- some
will have a suite
of traits that are
going to allow
them to reproduce
Natural Selection
4. Individuals with certain traits are more likely
to survive and reproduce. Natural selection
occurs when individuals with certain traits
produce more offspring than do individuals
without those traits
Main Idea:
Heritable variation leads to differential
reproductive success; this is natural
selection
Now, rewrite this statement in your own
words.
Then work on the graphing activity on the
back of your notes.
Ways to Create Evolution
1. Genetic drift - genes will vary (so change) in
population from generation to generation
Ways to Create Evolution
2. Natural Selection – 3 “modes” (explained soon)
Ways to Create Evolution
3. Gene flow or gene migration – transfer of genes
from one population to another (cross breeding)
Ways to Create Evolution
4. Mutation- in genes. This is where new traits
come from.
Ways to Create Evolution
BONUS WAY (HUMAN CAUSED) -- Non-random
mating (like purebred pet breeding)
Natural Selection
Process in which more favorable
traits survive through time
Selection
acts on
individuals
but
populations
evolve
Modes of Natural Selection
Modes of Natural Selection
Directional
Diversifying
Stabilizing
Why does evolution take so long?
Rate of Reproduction




Life span
# of offspring
Growth rate
Length of reproduction cycle
Number of habitats
Size
External environmental forces

Earthquake, weather, etc.
Rate of Evolution
Pressure to change
Ability to change – diversity
Rate of reproduction – Remember
what causes this from your previous
notes!
Biological Diversity
Diversity is the single most
important function of evolution
Reasons for diversity
 Adapt to environmental changes
 Respond to change Ex: pollution,
global warming
 Live in multiple habitats
Adaptation
Natural selection can eventually
lead to adaptation
Definition – characteristic or trait
that improves the survival and
reproduction of an individual or
population
Adaptation is a GENETIC change
Acclimation
Definition – Temporarily
improving survival and
reproductive success
Characteristic or trait is NOT
GENETIC and cannot be
passed on
Types of Adaptation
Models of evolution
Gradualism –
Very slow
adaptation
 Punctuated
Equilibrium –
Rapid burst of
change resulting
in new species

Fossils
Definition: A remnant or trace of a
past organism
Many varieties of dating techniques
are use to determine when the
organisms became fossilized – ex:
strata of rock it is found and
radioisotope dating
Paleontologists are scientists that
study fossils
Relationship Types
Homologous structures – show a
common ancestor

Structures are similar, but adapted to
the new organism
Vestigial structures – structures that
are present but have little to no
functional value (odd traits link them)
Evolution does not result in
perfect organisms
Selection edits existing variation (some survive, some
don’t)
Compromise between adaptations
Historical constraints (like
earthquakes, volcanoes, etc)
Chance (some organisms are simply lucky)