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Evolution
Darwin & Determination
Theories before Darwin:
James Hutton – Geologic Change
stated that the earth is millions or billions of
years old.
Jean-Baptiste Lamarck - Use or Disuse (use it
or lose it)
stated that organisms either use
characteristics or lose those characteristics.
Charles Darwin:
• Born 1809
•Born to a wealthy family (father was a doctor and
member of aristocratic class).
•Mother died when Charles was young.
•Charles was a Naturalist and Entomologist.
•Sent to Medical School at 18 and failed
out at 19.
•Went to Seminary school and received a degree in
Divinity from Cambridge University.
•
While there he became friends with John S.
Henslow (botany professor) who set him up
as Ship’s Naturalist on the H.M.S. Beagle.
•Beagle set sail around the world in 1831
(Charles was 22 years old).
•Stayed in the Galapagos Islands
for a couple of weeks, then
headed towards Asia.
•Charles had been sending everything he collected
back to Henslow in England.
Darwin Left England in 1831
The HMS Beagle’s Voyage
Darwin returned 5 years later in
1836
Marine Iguana, photo courtesy of mtchm, flickr
creative commons
Blue-footed booby
courtesy of stirwise, flickr creative commons
, photo
Finch, photo courtesy of
stirwise, flickr, creative commons
Giant
tortoise, photo courtesy of
Planetgordon, flickr creative commons
● Each was adapted to
eating a particular type of
island food
●He concluded that all came
from one ancestral species
Cactus finch, photo courtesy of zrim,
flickr creative commons
•Upon returning home, he found that he had become
quite noted as a collector and a scientist and
became a fellow of the geological society.
•Spent two years arranging notes and specimens
from the trip and displaying them for other
scientists. Got married (Wedgwood Family).
•Charles began to get ideas of a “transmutation”
theory to explain some of the differences that
he saw in animals.
• He was urged to write a book about
it and his travels.
•In 1844 he wrote the manuscript for
a book but didn’t want to publish.
•In 1859, when others were coming up with similar
theories, he published On the Origin of
Species by Means of Natural Selection.
•Charles Darwin died at his home in
1889 from a heart attack and was
buried in Westminster Abbey.
Evolution: is the slow , gradual
change in a
population of organisms over time; change over time
Checkpoint
1. Darwin traveled to which islands?
2. What was the name of his ship?
3. Name 4 species he observed on the
islands.
4. He developed what theory?
5. This theory explained how organisms
_______________ over _________
Darwin’s Theory
1. Variation exists among individuals in
a species. These traits are inherited.
2. Individuals will compete for resources
3. Competition would lead to the death of some,
while others would survive
4. Individuals that had advantageous variations
are more likely to survive and reproduce.
.
Darwin called this - Natural Selection
Those organisms that are best “fit” to the
environment will survive the environment and
reproduce.
Adaptation – a characteristic that an organism has
that allows it to survive.
Extinction – all members of a population dying out
due to not having beneficial adaptations.
What’s
the
point?
Survival of the fittest:
If you outcompete other
organisms for few resources you
will live to pass on your genes.
Ex: Camouflage & mimicry
Say in a species of blob….there exists blobs
of all shapes and sizes (variation)
Blobs eat the little purple organisms that live
underground and on the surface.
During a particularly hot year, food became less
abundant (competition), blobs that had the ability
to dig into the soil to get food had a better chance
of survival.
Many blobs died that year…….
The ones that survived mated and passed their
genes to the next generation. (reproduction)
The next generation had more blobs with the pointed
noses. That is NATURAL SELECTION.
1.Variation
2.Competition
3.Survival
4.Reproduction
Artificial Selection - humans selected variations
they found useful and bred animals and plants
for those traits.
Much of our agriculture (food,
animals, clothing) is a result of
artificial selection that has
occurred over many generations.
We can influence the
EVOLUTION of a species
Checkpoint
1. What was the name of Darwin’s book?
2. The theory states that
a) individuals of a species have differences, called_________
b) these individuals ________________ for resources
c) some will die, others will ____________________
d) survivors will _________________________ and pass
traits to offspring
3. Any trait that helps an organism survive is called an
_______________________________
4. When humans influence evolution be breeding for desired
traits, it is called _______________________________
We will be in the
computer lab
tomorrow: D204.
Evidence for Evolution
Biogeography and Fossil Evidence
shows…..
● similarities between extinct animals and animals that are
alive
● earth’s layers, and species that lived at each time
● Fossils found at lower layers of rock are simpler than
those found at upper layers.
Dinosaurs have always fascinated us, movies such
as Jurassic Park capitalize on that fascination.
How do we know what dinosaurs looked
like?
We create a picture based on the bones
we find (fossils) and use modern reptiles
to guess at their texture and skin color.
Comparative Anatomy
●Homologous structures – these are parts of the
body that are similar, but have different functions
Suggests common
ancestry
All forelimbs of
vertebrates have the
same pattern of
bones.
ex. The flippers of whales,
and the wings of birds
Comparative Anatomy
Analogous structures:
are UNLIKE
homologous structures
in that the structures
appear similar but do
not imply common
ancestry.
EX: wings of a bird and
wings of an insect.
Comparative Anatomy
Vestigial Organs
Organs that are found in you that have no purpose
in the body, but are found and used in other
organisms.
1. You have an appendix.
2. Snakes have hipbones. 
3. Whales have
hipbones too.
3. Molecular biology (Biochemistry)
Segments of our DNA called
genes are much like that of
other species and provide
evidence for Evolution and a
common ancestor.
4. Embryonic Similarities
All vertebrate organisms look similar during
formation. Also, the process follows the same steps.
Checkpoint: With your partner, find the answers in your notes.
1. ____________ evidence shows when organisms lived on the
earth
2. Species that are closely related will have similar _______
3. A _______________ organ is one that has no function.
4. _________________ structures look the same but have
different functions, like the arm of a human and the flipper of a
whale.
5. ____________ of different animals develop in the same way.
The Theory of Evolution:
Darwinism
We have discussed the 4 supporting
evidences of evolution.
Biogeography
Comparative anatomy
Molecular Biology
Embryology

Now we are going to discuss the 4
mechanisms of HOW Evolution occurs…
#1
Natural Selection:
Natural Selection – AKA “Survival of the
Fittest”
A gradual, non-random process by
which biological traits become either
more or less common in a population
As you can see there is a variation in the phenotype of these
beetles: Green or brown


Genetic Variations –
differences within a population
Increases or decreases an organisms
chance of survival
Inherited and controlled by alleles
Allelic frequencies in a populations gene
pool will change due to natural
selection
Genetics Determines
Evolution:
Gene Pool – All the alleles in a
populations genes. In other words every
form of a trait
Allelic Frequency – the % of any specific
allele w/in a gene pool
Genetic Equilibrium – allele frequency
remains the same over generations
 Populations in genetic equilibrium
are not evolving
Factors that affects genes can affect
equilibrium
 Mutations [negative, positive]
Negative more than likely causes
death
Positive may be beneficial and
passed on to future generations
The genetic variation in this scenario are
the genes that code for the color of the
beetle.
3 Types of Natural Selection that
Act on Variation:
1. Stabilizing Selection – natural
selection that favors average individuals
3 Types of Natural Selection that
Act on Variation:
2. Directional selection – natural
selection that favors an extreme form
of a trait
3 Types of Natural Selection that
Act on Variation:
3. Disruptive selection – individuals w/
either extreme form of a trait
#2 Mutation
Mutation: change in a gene; alteration of
a nucleotide sequence.
EX: A mutation causes two green
beetle parents to have a brown
beetle
#3 Migration
Migration: Movement of some individuals
to another population
Gene Flow – transfer of
alleles from one
population to another
population through
immigration of
individuals. This
disrupts allele
frequency.
#4 Genetic Drift
Genetic Drift: some individuals may by
chance and not because of “fitness”
leave more descendants and therefore
pass on their genes.
Change can be simply a random thing.
Bottleneck Effect
- having an event
that kills off
members of a
species randomly by
chance.
Founder Effect
- a new colony is
formed by a few
members of the
original population
Checkpoint: With your partner, use your notes to find the
answers.
1. ____________ ______________ is also known as survival of
the fittest.
2. Three types of natural selection act on variation:
a. ______________
b. ______________
c. ______________
3. _________________ are changes in the amino acid
sequence of gene and can have positive or negative outcomes.
4. ________ _________ occurs when individuals of genes move
to another population.
5. Sometimes individuals pass on their genes due to chance
rather than fitness resulting in ____________ _________.
So how do new species
come about?
The Evolution of Species:
Species – organisms that look alike can
interbreed to produce fertile offspring
Speciation – evolution of a new species.
Donkey
*NOTE: Organisms within the same species have
reproductive success ( ability to pass genes onto
the next generation in a way that they too can
pass on those genes.)
Mule
Horse
He can not
have offspring
because his
+
=
parents are two
different
Physical Barriers Cause Speciation:
1. Geographic Isolation – a physical
barrier divides a population
2. Reproductive Isolation – the inability
of organisms to mate and breed fertile
offspring
Genetic material becomes so
different fertilization cannot occur
Behavior – mating seasons are
different
These Bowerbirds have different mating seasons and
rituals. These 2 factors contribute to Reproductive
Isolation
Shifts from the Average Cause
Speciation:
Directional Selection
Stabilizing Selection
Disruptive Selection
Does evolution
happen fast or slow?
Both!
Speciation Rates - the time it takes for evolution to
occur.
2 Theories:
#1 Gradualism: – idea that species
originate through a gradual change of
adaptations
# 2. Punctuated Equilibrium : things
staying the same for a period of time
then rapidly changing due to a
catastrophic event.
There are TWO types of
Evolution
#1 Divergent Evolution
– accumulation of
differences between
groups which can lead
to the formation of
new species
Adaptive Radiation – ancestral species evolves
into an array of species to fit a particular
environment or niche.
#2 Convergent Evolution – organisms not
closely relate, independently evolve
similar traits (to adapt to similar
environments.)
Macroevolution
When one species
is replaced by
another species.
Australopithocene skull
Homo Sapien Skull
Microevolution
Species giving rise
to several different
species.
All citrus came from an
original species of
citrus tree