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EVOLUTION
How Species Change
Over Many Years
A Quick Review

1. When looking at rock layers, where are
the oldest rocks/fossils located?

2. What type of rock consists of fossils?
GOAL
 To
define evolution and the 4 ideas
associated with the theory
Evolution

Species


A group of similar organisms that
can interbreed to make fertile
offspring
Ex: All lions mate with one
another
– Lions + Tigers = infertile Ligers or
Tiglons
Evolution

Evolution

A change in a species over time
Evolution

Evolution

How has man
changed over time?
Evolution

Lamarck’s
Theory





Theory of use & disuse
An organism gets a new organ if it
needs it
Use it more & it will grow bigger
New organ is passed to offspring
What do you think about the
validity of Lamarck’s Theory?
Give an example
Evolution

Darwin’s
Theory



Theory of natural selection
Better explanation of evolution
The survival & reproduction of the
organisms best adapted to their
surroundings
Parts of the Theory of Natural
Selection

Part One:
Survival of
the Fittest


Organisms overproduce offspring
Organisms that are better
competitors or more fit, will
survive
Ex: Survival of the Fittest
Dandelions produce many seeds
 This ensures some will live- others will not
be able to find enough food & sunlight

Ex: Survival of the Fittest
Tadpoles- many hatch at once
 Fierce competition- stronger, faster ones
will find food faster & outrun enemies

Parts of the Theory of Natural
Selection

Part Two:
Variation
and
Adaptation

Offspring that survive have
structures or behaviors that make it
better “adapted” to its
environment

Certain differences or variations
help some to out-compete others
– Even within a species
– Ex: Finch Beaks
Variations in Finch Beaks
Variations in Beaks and Feet
Parts of the Theory of Natural
Selection

Part Two:
Variation
and
Adaptation


Variation= small differences
within one structure of a species
that make an organism more fit
Adaptation= changes in structures
or behaviors that make an
organism more fit
Variation & Adaptation Example

How would a variation in polar bear coats help
certain polar bears to have greater fitness?
– There are variations in polar bear coats
– Some polar bears have thicker coats of fur than others=
better protection to cold
– They are more likely to survive- this adaptation to
their surroundings makes them a better competitor
Variation & Adaptation Example



What happens to the fitness of a thick coated
polar bear if the environment become warmer?
Which type of polar bear has the better
variation in coat?
“The fittest that survive may change with their
surroundings”
Parts of the Theory of Natural
Selection

Part Three:
Reproduction

Individuals that are more fit:
– Survive longer
– Reproduce more
– Pass on the beneficial traits or
differences
What causes evolution?

Causes of
Evolution

Mutations or natural
accidental mistakes in the
animal’s DNA
What causes evolution?

Causes of
Evolution


Negative Mutation: Organism
dies because it can’t compete
(extinction)
Positive Mutation: Organism
becomes a better competitorincreases survival & reproductive
chances
Extinction

Extinction

Occurs when many small
adaptations occur over time (or
negative mutations)

Those with new adaptations outcompete older “versions” of the
species
Assessment


A hummingbird’s beak, giraffe’s neck & vampire
bat’s teeth all help them to do what better?
What are adaptations- how do they affect the
organism?
Evidence Supporting Evolution

Evolutionary
Evidence

1. Fossil Record- documents the
change in organisms over billions
of years
Fossil Evidence
Evidence Supporting Evolution

Evolutionary
Evidence

2. Anatomical Evidence- similar
body structures
– Homologous Structures=
similar body parts that evolve
suggest common ancestry
Homologous structures
What similarities do you see among the
structures in the diagrams below?
 What do these homologous structures
indicate?

Homologous Structures
Evidence Supporting Evolution

Evolutionary
Evidence

3. Embryological Evidencesimilarities in the embryos of very
different organisms
Evidence Supporting Evolution

Evolutionary
Evidence

4. Chemical and Molecular
Evidence
– The more similar the DNA
code, the more closely related
two organisms are
DNA Homology
Peppered Moth Scenario

The Peppered Moth has been forced to
evolve based on pollution from factories.

Nowhere to Hide
Peppered Moth Scenario

Which moth ended up being more “fit” or a
better survivor or competitor? Why?
Websites

“Becoming Human” interactive
documentary
Assessment
A change in the future that may affect the
evolution of living things is global warming
 How might global warming affect
evolution? Why?
