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Transcript
Get out your notebook
Write down:
– What is one career that collects evidence for
evolution?
– What is evolution?
History of
Evolutionary
Thought
2
Early Ideas On Earth’s
Organisms
 Aristotle
believed species
were fixed
creations
arranged by their
complexity
 Idea lasted 2000
years
3
Early Ideas On Earth’s
Organisms
Linnaeus – 1st to
group similar
organisms and
assign them Latin
names
Two word name
(Genus species)
Known as Binomial
nomenclature
4
Lamarck’s Theory of
Evolution
Jean-Baptiste Lamarck,
1809
One Of First Scientists
To Understand That
Change Occurs Over Time
Stated that Changes Are
Adaptations To
Environment acquired in
an organism’s lifetime
Said acquired changes
were passed to offspring
5
Lamarck’s Theory of
Evolution
Idea called Law
of Use and
Disuse
If a body part
were used, it
got stronger
If body part
NOT used, it
deteriorated
6
Lamarck’s Theory of
Evolution
 Inheritance of Acquired
Characteristics
 Proposed That By Selective Use Or
Disuse Of Organs, Organisms Acquired
Or Lost Certain Traits During Their
Lifetime
 These Traits Could Then Be Passed On
To Their Offspring
 Over Time This Led To New Species
7
Lamarck’s Theory of
Evolution
Use & Disuse -
Organisms Could
Change The Size Or
Shape Of Organs By
Using Them Or Not
Using Them
Blacksmiths & Their
Sons (muscular arms)
Giraffe’s Necks
Longer from
stretching)
8
9
Lamarck’s Theory of
Evolution
Inheritance Of Acquired Traits
– Traits Acquired During Ones Lifetime
Would Be Passed To Offspring
Clipped ears of dogs could be passed to offspring!
10
Lamarck’s Theory of
Evolution
Tendency Toward Perfection
Organisms Are Continually Changing
and Acquiring Features That Help
Them Live More Successfully In Their
Environment
Example: Bird Ancestors Desired To
Fly So They Tried Until Wings
Developed
11
Lamarck’s Mistakes
Lamarck Did NOT Know how
traits were inherited (Traits are
passed through genes)
Genes Are NOT Changed By
Activities In Life
Change Through Mutation Occurs
Before An Organism Is Born
12
What we know now:
Phenotype: The physical characteristics that
are expressed based on a species’ genes (what
we see)
Genotype: The DNA/genetic code that
determines how an organism looks (we cannot
see it). Passed from generation to generation.
Phenotype can change during life, but
this will never change genotype, so these
traits are not inheritable.
Evolution and Natural
Selection
Charles Darwin the
Naturalist
copyright cmassengale
15
I. Charles Darwin
- Charles Darwin is the father
of evolutionary theory.
- What question is he trying
to solve?
- Why do populations change
over time?
Darwin on HMS Beagle
It took Darwin years to develop his theory of
evolution; eventually published ideas in book
entitled On the Origin of Species
He began in 1831 at age 22 when he took a
job as a naturalist on the English ship HMS
Beagle, which sailed around the world on a
five-year scientific journey.
A map of Darwin’s voyage
The Galapagos Islands
Finches on the islands resembled a
mainland finch
More types of finches appeared on the
islands where the available food was
different (seeds, nuts, berries,
insects…)
Finches had different types of beaks
adapted to their type of food gathering
19
20
Darwin’s Observations
Left unchecked, with
unlimited resources, the
number of organisms of
each species will increase
exponentially, generation
to generation
In nature, populations tend
to remain stable in size
Environmental resources
are limited
21
Darwin’s Conclusion
• Production of more
individuals than can be
supported by the
environment leads to a
struggle for existence
among individuals
• Only a fraction of
offspring survive each
generation
• Survival of the Fittest
22
Darwin’s Observations
• Individuals of a
population vary
extensively in their
characteristics with
no two individuals
being exactly alike.
• Much of this
variation between
individuals is
inheritable.
23
Darwin’s Conclusion
• Individuals who
inherit
characteristics most
fit for their
environment are
likely to leave more
offspring than less fit
individuals
• Called Natural
Selection
24
Darwin’s
Theory
of
Evolution
•The unequal ability of individuals to
survive and reproduce leads to a gradual
change in a population, with favorable
characteristics accumulating over
generations (natural selection)
•New species evolve
25
Evolution
- Evolution is when a POPULATION of
organisms changes over time
- Darwin proposed the idea that evolution
happens through natural selection.
- Developed from his idea of artificial
selection = nature provides variation and
HUMANS select variations they find useful
Natural Variation and Artificial
Selection
Key Concept:
In Artificial Selection, Nature
Provided The Variation Among
Different Organisms, And
Humans Selected Those
Variations That They Found
Useful
27
28
II. Natural Selection
-
Natural selection is the way evolution
happens. That is, natural selection is
how organisms change over time.
-
Natural selection is when nature selects
a. organisms with good genes to live and pass
on their genes and…
b. organisms with bad genes to die out
II. Natural Selection
- In any population, there
are differences between
species.
- For example: These fish
are different sizes,
shapes and speeds.
- What causes these
differences?
- Mutations (alterations in
DNA sequences)
II. Natural Selection
- Organisms with
helpful traits, such as
being fast, survive
better in their
environment,
compared to being
slower.
II. Natural Selection
- Over time, only the
organisms with the
good genes (in this
example, fast fish) will
survive and the new
population of fish will
look very different
from their ancestors:
Ancestors (Great-Grandparents)
New population of fish
II.
Natural Selection
Sometimes called “Survival of the
Fittest”
- Fitness: the physical traits and behaviors
that enable organisms to survive and
reproduce in their environment
- Common Descent: the idea that all species
have common ancestors
Darwin’s Theory of Natural Selection
1.Individual Organisms In Nature Differ From One Another. Some Of
This Variation Is Inherited
2.Organisms In Nature Produce More Offspring Than Can Survive,
And Many Of These Offspring Do No Reproduce
3.Because More Organisms Are Produced Than Can Survive, Members
Of Each Species Must Compete For Limited Resources
4.Because Each Organism Is Unique, Each Has Different Advantages
& Disadvantages In The Struggle For Existence
5.Individuals Best Suited To Their Environment Survive & Reproduce
Successfully – Passing Their Traits To Their Offspring.
6.Species Change Over Time. Over Long Periods, Natural Selection
Causes Changes That May Eventually Lead To New Species
7.Species Alive Today Have Descended With Modifications From
Species That Lived In The Past
8.All Organisms On Earth Are United Into A Single Tree Of Life By
Common Descent
You are Darwin. Explain why and
how this change could happen.
Finch Beak Size
These two finches
came from the same
ancestor.
According to Darwin,
how did they come to
look different?
What would Lamarck
had said?
Exit Ticket
What is the process that natural selection drives called? (Points….1…0…)
a. Speciation
b. Natural Selection
c. Evolution
d. Degradation
Which one of these is an example of natural selection? (Points…1…0…)
a. A snake loses its skin once a month to remove parasites.
b. A population of fish with an avian predator gradually changes over time from grey-blue to a
green color as the color of the water in their pond becomes greener due to green algae
growth.
c. A single giraffe stretches his neck every day until it grows longer so that he can eat taller
vegetation.
d. A dog barks to warn its owner when someone comes to the door.
Predict what would happen in the following scenario: (Points…5…4…3…2…1…)
There is a large population of wolves. They all have different length fur in their coats. Some have very
long, thick fur. Others have very long, thin fur. And still others have short, thin fur. There are no
wolves with short, thick fur. Predict what would happen to the wolf population if there was a
climate change that caused the temperatures to drop 20 degrees throughout the year. (If you
need more room please use the back of this page).