Download Review Slides - Evolution

THEORIES OF EVOLUTION
Driving Question: How and why do species change
over time?
How they Agreed
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Life has changed gradually over
time and was still changing
Living things change to be better
suited and adapted to their
environments
All organisms are related
Life evolved from fewer, simpler
organisms to many, more complex
organisms.
Jean-Baptiste Lamarck’s Theory of
Evolution
French scientist – published theory 1809
Main features of his theory:
• the law of use and disuse
• the law of inheritance of acquired
characteristics
Organisms could acquire or lose traits during
their lifetime based on if they used them or
not. Acquired traits would be passed to
offspring.
Charles Darwin’s Theory of Evolution
English naturalist – published theory 1859 in
book called On the Origin of Species
Main features in his theory:
• individuals compete for limited resources
• individuals in a population show natural
variation
• individuals with characteristics best suited to
their environment are more likely to survive
to reproduce
• 'successful' characteristics are inherited
Which theory is right?
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Darwin’s theory has been supported by evidence
including genetics
Lamarck’s theory has been disproven
 Changes
that occur during an animal’s life are not
passed on to the animal’s offspring
 Only way traits are passed on is through genes
What about Wallace?
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Alfred Wallace
independently came up with a
theory of evolution through
natural selection
1858 his theory appears in a
paper published along with
Darwin’s paper
1859 Darwin publishes his
book, gets all the credit
James Hutton & Charles Lyell
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Earth is millions of years old
Processes that changed Earth in the past are the
same processes that operate today
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What this meant for
Darwin
 If
the Earth can change
over time, why can’t
life?
 Earth is old enough for
evolution to have
occurred.
EVIDENCE FOR EVOLUTION
Driving Question: How and why do species change
over time?
DNA
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The more similar the DNA coding of two
organisms, the more closely related they are.
Doesn’t mean they evolved from each other, but that
they are more likely to share a common ancestor.
Whale DNA is more similar to Artiodactyls DNA
 Mammals
with even number of toes
 Pigs, deer, cows, goats, hippos, giraffes
What?

What is biogeography?
 The
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study of the geographic distribution of organisms.
What is fauna?
 Animal

life
What is a faunal assemblage?
A
group of living or fossil animals found in a particular
geographic area.
Biogeography is the study of the
geographic distribution of organisms
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Populations of the same
species in different
places adapt to different
local environments.
Similar but unrelated
species - species living
in similar environments
have similar structures
and behaviors.
Influenced by geological
processes (plate
tectonics, sea level
changes, etc)
Fossils
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Record of life changing
over time.
Fossils in the bottom
layers are very different
from the organisms alive
today. As you look at
younger rock layers the
fossils found there are
more similar to
organisms found today.
Find intermediate species
that show change over
time.
Embryology and Development
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Embryos of many different kinds of
animals look very similar and it is
often difficult to tell them apart.
Many traits of one type of animal
appear in the embryo of another
type of animal.
 Human embryos have gill slits
and tail
Since animals develop similarly, it
implies that they are related, have
common ancestors, and they started
the same and developed different
traits through evolution.
Comparative Anatomy
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Similarities in the anatomy of different organisms
helps us understand how they are related.
 Homologous
structures: Structures that are shared by
related species. They are inherited from a common
ancestor. Structures are similar but become modified
through evolution.
 Many mammals have similar limb structures.
Comparative Anatomy
 Homologous
structures: Similar structure, not
necessarily similar function.
Comparative Anatomy
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Vestigial structures: structure in an organism that
has lost all or most of its original function in the
course of evolution
 Humans
– appendix, tail bone, wisdom teeth, plica
semilunaris
 Whale – pelvic bone
 Wings in flightless bird
Comparative Anatomy
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Analogous structures: Body parts that have the
same function, but different structure. These
structures are not inherited from a common
ancestor.
Darwin’s Explanation of How Evolution Occurs
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Variations – differences between individuals of
one species
 Variation
is the rule, not the exception!
 Follows the normal distribution or bell curve:
DARWIN’S THEORY OF
EVOLUTION
Driving Question: How and why do species change
over time?
Darwin’s Explanation of How Evolution Occurs
There is a struggle to survive.
 Limited resources in the environment.
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 Limited
amount of food, water, space, etc.
 Organisms compete for these limited resources
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Darwin’s Explanation:
1. More individuals are born in a species than the
environment can support. There is a struggle to
survive. Organisms compete for limited resources.
Darwin’s Explanation of How Evolution Occurs
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Variations – differences between individuals of
one species
 Variation

is the rule, not the exception!
Gene Pool – combined genetic information of all
the members of a population.
 Genetic
variation – variation in alleles of genes in
a gene pool
Darwin’s Explanation of How Evolution Occurs
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Darwin’s Explanation:
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2. Within every species there is naturally
variation.
Sources of Genetic Variation:
Mutations - changes in the DNA.
 Gene flow - any movement of genes from one population to
another.
 Sexual Reproduction - genetic shuffling can introduce new
gene combinations into a population.
 Lateral Gene Transfer – pass genes from one individual to
another, common in bacteria – important process in the
evolution of antibiotic resistance

Darwin’s Explanation of How Evolution Occurs
Advantageous traits are adaptations.
 Adaptation: an inherited characteristic that
increases an organism’s chance of survival.
Adaptations increase fitness.
 Fitness: ability of an individual to survive and
reproduce in its specific environment.
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Darwin’s Explanation of How Evolution Occurs
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Natural Selection – selection pressures in each
environment causes changes in the inherited
characteristics of a population. It directs these
changes in ways that increase a species’ fitness
in its environment.
Darwin’s Explanation of How Evolution Occurs
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Survival of the Fittest – Individuals better suited
to their environment – high fitness – survive and
reproduce more successfully.
 Not
the biggest, strongest, fastest
Darwin’s Explanation of How Evolution Occurs
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Descent with Modification – over time, natural
selection produces organisms with different traits.
Organisms descend, with changes, from their
ancestors.
Darwin’s Explanation of How Evolution Occurs
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Darwin’s Explanation:
3. Some variations give organisms an advantage
over others in the struggle to survive.
Quick reaction time, can get away faster
Evolution in Action –
Do you know why deer have eyes on the side of their
head and we have eyes on the front of our head?
 Wider eye distance, better peripheral vision. Closer eye
distance, better depth perception. Prey vs. Predator.

Darwin’s Explanation of How Evolution Occurs
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Darwin’s Explanation:
4. More of these individuals will survive and
reproduce than will those with less
favorable traits.
 Natural Selection – Types of Selection
 Directional, Stabilizing, Disruptive
Stabilizing Selection: When individuals near the center of the
curve have higher fitness than individuals at either end.
Directional Selection: When individuals at one end of the curve have
higher fitness than individuals in the middle or at the other end. Evolution
causes an increase in the number of individuals with the trait at one end
of the curve.
Disruptive Selection: When individuals at the upper and lower ends of the
curve have higher fitness than individuals near the middle. Creates two
distinct phenotypes.
Artificial Selection
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Artificial Selection:
Humans breed animals
or plants for particular
traits. They select the
variations they want.
 Humans
can cause
species to evolve.
Natural Selection
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Change in the gene pool is not by chance.
Due to selection pressures
 Survival
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of the fittest = Reproduction of the fittest
Sexual selection
Genetic Drift Activity
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Genetic Drift – in a small population, an allele can
become more or less common by CHANCE.
 By
chance some individuals have more offspring, so
over time, their alleles can become more frequent in the
population.
Genetic Drift
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Bottleneck effect – a change in allele frequency
following a dramatic reduction in the size of a
population. Can reduce the gene pool (genetic
diversity).
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Usually caused by a disaster like a disease
Founder effect – allele frequencies change as a result
of the migration of a small subgroup of a population
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For example, several members of a fruit fly population
ended up in Hawaii. The fruit flies evolved in several
hundred species.
Darwin’s Explanation of How Evolution Occurs
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Darwin’s Explanation:
5. Many traits are passed from parents to offspring.
6. More individuals with favorable traits reproduce,
so the # of individuals with favorable traits
increases in each generation. The # with less
favorable traits decreases.
Darwin’s Explanation of How Evolution Occurs
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Darwin’s Explanation:
7. Eventually the favorable trait becomes the most
common form and over many generations (and
usually millions of years) such differences
accumulate until a new species results.
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Speciation
 Isolating
Mechanisms
 Adaptive Radiation
Genetic Equilibrium
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What does equilibrium mean?
A population that is not evolving, allele frequencies
in the gene pool do not change
Hardy-Weinberg Principle
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Allele frequencies in a population should remain
constant unless one or more factors cause the
frequencies to change.
Five conditions that can disrupt genetic equilibirum
and cause evolution to occur:
1.
2.
3.
4.
5.
Nonrandom mating (sexual selection)
Small Population Size
Immigration and Emigration
Mutations
Natural Selection
Speciation
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Species – a population or group of populations
whose members can interbreed and produce fertile
offspring.
Speciation – the formation of new species.
Speciation
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There are four types of isolating mechanisms that
can cause speciation.
Speciation: Reproductive Isolation
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Reproductive Isolation – When the members of
two populations cannot interbreed and cannot
produce fertile offspring.
 Three
ways that reproductive isolation can develop:
 Behavioral
Isolation – different behaviors prevent
interbreeding
 Geographic Isolation – populations are separated by
geographic barriers
 Temporal Isolation – species reproduce at different times
Speciation: Reproductive Isolation
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Reproductive Isolation
 Behavioral
Isolation – two populations are capable of
interbreeding but differences in courtship rituals or
other types of behavior prevent them from mating.
Speciation: Reproductive Isolation
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Reproductive Isolation
 Geographic
Isolation – two populations are separated
by geographic barriers (rivers, mountains or bodies of
water) that prevent mating.
Speciation: Reproductive Isolation
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Reproductive Isolation
 Temporal
times.
Isolation – Species reproduce at different
Speciation: Adaptive Radiation
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Founder Effect – the loss of genetic variation that
occurs when a new population is established by a
very small number of individuals from a larger
population.
Adaptive Radiation – a single species evolves into
several different species usually in response to new
environments.
Galapagos Islands
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Darwin – 1835 – went to Galapagos aboard the
HMS Beagle
Speciation – Galapagos Finches
1. Founders arrive
2. Separation of Populations
3. Changes in Gene Pool
4. Reproductive Isolation
5. Ecological Competition
6. Continued Evolution
Funky scardey cats run every Christmas!
See figure 16-7
Speciation – Galapagos Finches
MACROEVOLUTION
Jigsaw Activity
Macroevolution vs. Microevolution
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Microevolution – small scale, short time frame –
within a single population or species
Macroevolution – large scale, long time frame
(millions to billions of years) – includes more than
one species
Both involve natural
selection, mutations,
genetic drift and
migration
Image Source: http://evolution.berkeley.edu/evolibrary/article/evoscales_01
Macroevolution
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Paleontologists study fossils to learn about the
patterns of macroevolution.
 Fossils
are classified into clades (group of organisms
that consists of a common ancestor and all of its
descendants, it is a branch on the tree of life)
Image Source: http://evolution.berkeley.edu/evolibrary/search/imagedetail.php?id=260
Models of Evolution
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Evidence shows that evolution
occurs at different rates for
different organisms at different
times throughout the history of
the Earth.
Two Models
1. Gradualism – Slow and
steady evolution over time.
Models of Evolution
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2. Punctuated Equilibrium
- slow and steady is not
always the case. Most of
the time the species are in
equilibrium (structures don’t
change even though genes
may change). Then
equilibrium is interrupted
by brief periods of rapid
change.

Rapid on geologic time
scale may be 1000s of
years
Types of Macroevolution
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Extinct – species dies off, no longer exists.
Background extinction – natural rate of extinctions
due to natural processes like natural selection.
Mass extinction – event in which many species
become extinct over a relatively short time period.
6
mass extinctions
Types of Macroevolution
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Coevolution – two species evolve in response to
changes in each other over time. Usually these
two species can’t survive without each other.
 Ants
and Acacia
Types of Macroevolution
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Convergent Evolution – evolution produces
similar structures and characteristics in very
distantly related organisms because they evolve
in very similar environments.
Types of Macroevolution
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Speciation – one species evolves into two or more
species.
Types of Macroevolution
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Adaptive
Radiation = rapid
speciation - a single
species or a small
group of species
evolves over a
relatively short time
frame into several
different forms that
live in different
ways (different
ecological niches).