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Evolution
• Evolution refers to observable biological changes in a
population (or larger group of related organisms) over
time
• A population is a group of organisms of the same
species that interact and interbreed with each other.
Important Evolution Vocabulary
• Gene – a segment of DNA that
holds the information for
determining a trait.
• Gene pool – all of the genes of
all of the members of a
population.
• Population - a group of reproducing
individuals of the same species in
the same area (same gene pool).
• Alleles are different forms of the
same gene (for example, different
colors of beetle shells)
Microevolution vs. Macroevolution
•Microevolution –
changes to the gene pool of a
single population. Changes can
occur over a short period of
time.
• Example – differences between
dog breeds
Microevolution vs. Macroevolution
•Macroevolution –
changes and patterns over a
long period of time that result in
the origin of new species.
Usually refers to a group larger
than a single population (ex:
birds)
• Example – the evolution of birds
from dinosaurs
Both Microevolution and
macroevolution are dependent upon
genetic mutation and the exchange
of genes.
Microevolution
• When allele frequencies (relative
abundance of alleles of a given gene in a
population) change in a population,
microevolution occurs.
• Natural populations are never in genetic
equilibrium. (genetic equilibrium = no
change)
• Six processes of microevolution (smallscale changes in a population's allele
frequencies) prevent genetic equilibrium:
1. Mutation
A mutation is a permanent small-scale change in an organism's DNA.
For Example: ACCGA -> AGCG
Mutations are the primary source of new alleles
2. Gene Flow
Gene flow is the migration of individuals and their genes among
populations
3. Genetic Drift
Genetic drift is the random change in allele frequencies
over generations.
Genetic Drift Continued: Small populations
repopulating
The Bottleneck Effect:
The Founder Effect:
4. Natural Selection
Natural selection: In a given environment, differential survival and
reproduction among individuals of a population that vary in details
of shared, inherited traits.
Any trait that enhances an individual’s fitness (ability to survive
and reproduce in a particular environment) is called an adaptive
trait. Survival of the fittest?
How do these organism’s traits increase their fitness?
5. Artificial selection
In artificial selection humans choose which traits are passed on.
6. Sexual selection
In sexual selection certain traits are preferentially chosen by mates.
Microevolution Review
Review
Use your COLORED PENCILS to fill out the
microevolution worksheet
Movie time!
Lets watch some super super cute animals get eaten!
Short Evolution Discussion
Are humans still evolving?
Evidence for Evolution
Macroevolution occurs over very long periods of time.
What evidence do we have to show that it occurs?
• Observations of microevolution
• Light color is adaptive in areas of low pollution; dark color is
adaptive in areas of high pollution.
Evidence for Evolution
Macroevolution occurs over very long periods of time.
What evidence do we have to show that it occurs?
• Fossil Evidence
Archaeopteryx
Fossils of whale ancestors
Evidence for Evolution
Macroevolution occurs over very long periods of time.
What evidence do we have to show that it occurs?
• Molecular Evidence (DNA and proteins)
Evidence for Evolution
Macroevolution occurs over very long periods of time.
What evidence do we have to show that it occurs?
• Vestigial Structures
Patterns of Macroevolution
• Over long periods of time, we can observe repeating
patterns that happen to many different groups of
organisms.
• Coevolution
Predator and prey
Host and parasite
Pollinator and flower
Patterns of Macroevolution
• Over long periods of time, we can observe repeating
patterns that happen to many different groups of
organisms.
• Stasis
A lineage exists for millions of years with little or no change (e.g.
Bdelloid Rotifers and Coelacanths).
Patterns of Macroevolution
• Over long periods of time, we can observe repeating
patterns that happen to many different groups of
organisms.
• Adaptive radiation
A burst of speciation that occurs when a lineage encounters a
new set of niches.