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Evolution Notes 2007
I. Darwin’s influences
A. Jean Lamarck (1749-1849)
1. One of the first scientists to propose
the idea of evolution
2. Evolution-the process by which
modern organisms have descended
from ancient organisms
3. How and why organisms changed
was incorrect.
a. a desire to change
b. use vs. disuse
c. acquired traits were passed on
B. Charles Lyell
1. Geologist
2. Proposed that earth was much older
than other scientist believed
3. Earth changed over time
C. Charles Malthus
1. Limited amount of resources for
humans
2. Believed if population continued to
grow there wouldn’t be enough
resources to sustain population
D. Farmers
1. For many years farmers were
selectively breeding crops
and livestock to make them
better.
2. Artificial selection-mechanism in
which humans allow only
selected organisms to reproduce
E. Darwin’s observations
1. Sailed around the world and noticed
that organisms were specifically
adapted to their environments
2. In South America, observations
supported the idea that the modern
organisms living in South America
were descended from ancient
organisms living there.
3. On Galapagos Islands observed
that organisms were uniquely
adapted to their environments
and resembled the mainland species.
II. Darwin’s Two Main Points
A. Darwin published the book Origin of
the Species which described his theory
of evolution.
B. Main Point 1: Descent with
modification-process by which
descendants of ancestral
organisms spread into various habitats
and accumulate adaptations to different
ways of life
C. Adaptation-inherited characteristic
that improves an organisms ability to
survive and reproduce in a particular
environment
D. Main Point 2: Natural Selectionprocess in which organisms with
inherited characteristics well-suited for
an environment produce more
offspring than do other individuals.
III. Evidence for Evolution
A. Fossil Record
1. fossils – preserved remains or
markings left by organisms that
lived in the past
2. fossil record – chronological
collection of life’s remains in
the layers of rock on earth
3. extinction-when a species
no longer exists
B. Geographic Distribution
1. There are geographical patterns
that exist amongst life forms.
2. These patterns support evolution.
3. Example 1– marsupials in
Australia
4. Example 2 – similarities between
island and mainland species
C. Similarities in structure
1. Homologous structures –
similar structures found in more
than one species with a common
ancestor. Example – forelimbs of
mammals, pg. 301
2. Vestigial structures – remnant
of a structure that may have had
an important function in a
species’ ancestors but has no
clear function in the modern
species. Example “Goosebumps”
in humans, pg. 302
D. Similarities in Development
1. Embryos of closely related
species often have similar stages
of development. Example – All
vertebrates have a embryonic
stage in which pouches appear on
sides of the throat.
2. Homologous structures often
have similar embryonic
development.
E. Molecular biology
1. The more similar two species’
DNA is, the more closely related
the two species are to each other
(and vice versa).
2. All living things share some of
the same genes. This supports
Darwin’s idea that all life forms
are related.
IV. Darwin’s finches (an example of
evolution)
A. Population – group of individuals of
the same species living in the same
area at the same time
B. 13 species on the Galapagos Islands
1. Each species is uniquely
adapted to their environments.
2. They all closely resemble a
finch species living on the
mainland of South America.
C. It is hypothesized that:
1. Islands colonized by a single
finch species from mainland
2. Eventually diversified into
13 different species
3. The different species came
about through natural
selection.
D. Natural selection is dictated by the
environment.
V. A summary of natural selection
A. Species usually produce more
offspring than the environment
can support.
B. This creates competition to survive
and reproduce.
C. Natural variation found in species
allows for change.
D. Natural selection explains how two
populations of the same species
that are isolated can become two
different species.
VI. Pesticides
A. In the long term any single pesticide
is usually ineffective.
B. Resistance to pesticides is an
example of natural selection that
can be witnessed in a human life
time.
VII. Microevolution – a change in a
population’s gene pool
A. Gene pool- all the alleles in all the
individuals that make up the
population
B. Changes in gene pools
1. Frequency of alleles often change
due to survival rates and
reproductive success.
2. Hardy-Weinberg equilibrium –
the frequency of alleles in
a gene pool are constant over
time
3. Genetic variation is random
natural selection is not.
4. Genetic Drift – change in gene
pool of the population due to
chance.
a. The smaller a population is,
the more impact genetic drift
will have on the population.
b. Bottleneck effect –reduces
the amount of genetic
variation in a population
c. Founder effect – when a
small population of
individuals colonizes a
isolated location there is less
genetic variation
5. Gene Flow and Mutation
a. Gene flow – the exchange of
genes with another population,
tends to reduce genetic
differences between populations
b. Mutation – a change in an
organism's DNA
1. If carried by a gamete can
enter the gene pool
2. Mutations often play a role
in evolution since they are
the original source of genetic
variation.
3. Mutations are extremely
important in creating
genetic variation amongst
asexually reproducing
organisms.
6. Fitness– the reproductive
success of an individual
relative to the other
individuals in a population
VIII. Evolotionary biology and health
science
A. Sickle cell example (page 317-318)
B. Antibiotic resistant bacteria
1. Antibiotics – medicines that kill or
slow the growth of bacteria
2. Natural selection of antibiotic
resistant bacteria has lead to
a decrease in the effectiveness
of these drugs.
3. The misuse/overuse of these drugs
speeds up this process.
IX. Evolution is a theory that utilizes
scientific evidence to explain the
diversity of life. A theory is a
well-tested explanation that makes
sense of a great variety of scientific
observations.