Evolution
• Change in inherited traits due to beneficial DNA
mutations leading to the formation of new
species.
• Results in a change in the gene source
Theory introduced by Charles Darwin
1859: “On the Origin of Species by
Means of Natural Selection”
Charles Darwin
• Influenced by Charles Lyell’s “Principles of
Geology” suggesting fossils found in rocks are
evidence of organisms that lived thousands or
millions of years ago.
• Darwin observed variety in animal life and
geological features (Galapagos Islands) &made
connections to Lyell’s theories
• Realized: natural forces gradually change
Earth’s surface and those forces still occur in
modern times (geological evolution)
Charles Darwin History
* Joined the H.M.S. Beagle (1831-1836) as a naturalist to
survey the south seas (South America and the
Galapagos Islands) collecting plant and animal
samples
* On the Galapagos Islands, he observed species that
lived no where else in the world.
Darwin’s Principles of Natural Selection
• Organisms produce more offspring than can
survive
• Variations occur among individuals of a
species
• Genetic variations are passed on to offspring
• Organisms with helpful variations survive
and reproduce while others do not
• Over time, offspring of individuals with
helpful variations make up more of a
population and may become a separate
species
Natural Selection
Individuals with favorable traits
are more likely to survive,
reproduce, & produce offspring
suited for survival in their
environment.
Example:
English peppered moth (Biston
betularia) and the industrial
revolution
Try out this simulation w/ the peppered moths:
http://www.biologycorner.com/worksheets/pepperedmoth.html
Artificial Selection
• The selective breeding of domesticated plants
and animals occurs in Darwin’s time making it
possible to see first hand how variations in traits
could be formed and passed on in animal
populations such as dogs, sheep, and cattle
Evidence of Evolution
1. Biogeography:
Geographical
distribution of species
2. Fossil Record: order in which
fossils appear in layers of
sedimentary rock shows
evolutionary history
Evidence of Evolution
3. Taxonomy: classification
of life forms based on
similarities & differences
4. Homologous structures:
similar structures which come
from a common ancestor
Evidence of Evolution
5. Comparative embryology:
Study of structures that appear
during embryonic development.
6. Molecular biology:
DNA and proteins
Interpretations of time
1. Gradualism: Slow changes in
species overtime
2. Punctuated
Equilibrium:
Evolution occurs in
relatively rapid
change
Adaptive Radiation
• Emergence of numerous species derived from
a common ancestor & introduced to new
environments.
• Example:
Darwin’s Finches
Convergent Evolution
Species
from different
evolutionary
branches may
come to resemble
one another if they
live in similar
environments
Coevolution
• Evolutionary change, one species acts as
a force influencing the adaptations of a
second species
Example:
Humming birds & plants with
tube-like flowers: hummingbird
selects these flowers thus their
pollen is spread and the flowers
survive to pass on their genes…
Macroevolution
Taxonomic groups higher than the species
level
Microevolution
A change in a population’s gene pool over
generations.
Evolutionary changes in species over relatively brief
periods of geological time.
Causes of Microevolution
1. Genetic drift: Change in the gene pool
of a small population due to chance.
Genetic Drift
Bottleneck Effect
• Genetic drift (reduction of alleles in a population)
results from disaster that drastically reduces the
population size.
• Examples:
1. Earthquakes
2. Volcano’s
Genetic Drift
Founder Effect
Genetic drift resulting from the colonization in a
new location by a small number of individuals
Which results in random change of the gene pool
Example:
1. Islands
Causes of Microevolution cont.
2. Gene Flow: gain or loss of alleles from
a population by movement of individuals
Causes of Microevolution cont.
3. Mutation: Change in an organism’s
DNA creating a new allele
4. Non-random mating: selection of
mates other than by chance
5. Natural selection: Differential
reproduction