Transcript Evolution

Evolution
The Theory of Natural Selection
15.1 Page 418
Student Performance Standards
• SB5. Students will evaluate the role of
natural selection in the development of
the theory of evolution.
– a. Trace the history of the theory.
– b. Explain the history of life in terms of
biodiversity, ancestry, and the rates of
evolution.
– c. Explain how fossils and biochemical
evidence support the theory.
Lesson Essential Question
• How is the theory of natural selection
related to the theory of evolution?
EVOLUTION
Is the Genetic change in a
species’ gene pool over
time.
A mechanism of evolution is
natural selection.
Who helped to develop this theory of
evolution?
Lamarck and
Darwin
Jean Baptiste Lamarck
1744-1829
Charles Darwin
1809-1882
Lamarck’s Theory of Acquired
Characteristics (1801)
• Believed an organism could change its
physical features in order to survive.
• When the individual reproduced, the
changes made during its lifetime would
be passed on to it’s offspring.
• Hmmmm…….
So, if you were to work out
every day, or study biology
every day, your babies would
inherit the traits you
acquired.
Given our current knowledge of genetics, this
is not possible!
Was Lamarck’s theory true or false?
• Definitely false! Otherwise……..
Charles Darwin (1809-1882)
• English Naturalist
• Contributed the most to our understanding of evolution.
• Sailed around the world to the Galapagos Islands where
he
• Collected specimens of
– plants
– animals
– fossils
Darwin Reached the Galapagos Islands in 1835:
– A series of volcanic islands off the coast of S. America
– Here, Darwin learned the most about variation in species.
– He saw many plants and animals well suited for survival in
their environment.
– He collected finches and observed that they were all
different depending on which island they came from.
– Darwin suspected populations from the mainland changed
after reaching the Galapagos.
Darwin hypothesized that….
• Over long periods of time, species
develop adaptations which allow
them to survive in their
environment.
• This is the theory of NATURAL
SELECTION.
Galapagos Islands
Charles Darwin’s Theory of
Natural Selection
• Organisms can only pass on traits they are
born with.
• There is variation among organisms of the
same species.
• Those best suited to their environment will
survive and reproduce the most (fitness).
• Survival of the fittest
Natural Selection (Cont….)
• Due to DNA mutations, variation exists
among members of the same species.
• The environment selects which
variations will become adaptations
which allow the species to survive.
Polar bears wouldn’t do well in the desert, and crocs wouldn’t do well
in the arctic!
4 Principles of Natural Selection:
1. Variation - differences within a population
exist.
2. Heritability - variations are inherited from
parents.
3. Overproduction – populations produce
more offspring than can survive.
4. Reproductive Advantage – individuals
with variations suitable for the
environment will be able to survive and
reproduce.
So, why do giraffes have such long necks?
• Modern evolutionary theory proposes ancestral giraffes
probably had short necks but that length varied from
individual to individual due to varying genotypes.
• When food supply was limited, individuals with longer necks
survived better because they could utilize a food source
unavailable to the others. So, longer necked giraffes
survived to pass on the trait (alleles) and the offspring inherit
long necks.
Example of Natural Selection
• Peppered Moth
Environments Change
• Peppered Moths Example
• Mid 18th century = England’s industrial
revolution resulted in tons of soot
deposited on trees and rocks.
• The discoloration camouflaged dark
colored moths.
• Where these dark colored moths were
once the minority, they are now the
majority.
On The Origin of Species
• 1859 – Darwin compiled evidence for natural
selection and his book, On the Origin of Species
by Means of Natural Selection, was published
END PART 1
• Complete Vocabulary for homework
• Handouts are due at end of class for a
daily grade .
Tuesday
• Review terms and practice questions
• Breeding Bunnies natural selection
activity.
Terms We’ve Learned:
• Evolution
• Genetic change over time
• Fitness
• the genetic contribution of
an individual to the next
generation's gene pool
• Natural Selection
• Gene Pool
• “Survival of the fittest”
• All the genes in a
population
Practice Question
• Which of the following is true?
A. Natural selection
B. Natural selection
part of it
C. Natural selection
of evolution
D. Natural selection
same thing
results from evolution
includes evolution as
is only one mechanism
and evolution are the
Which is a concept of Lamarck's
work?
• Change results from the survival of the
fittest
• Body structure can change according to
the actions of the organism
According to Darwin's theory of Natural
selection, individuals who survive are the ones
best adapted for their environment. Their
survival is due to the
A. Possession of adaptations developed
through use
B. Possession of inherited adaptations to
maximize fitness
C. Lack of competition within the species
D. Choices made by breeders
Evidence of Evolution
Ch 15 section 2
Evolution
- Any change in the relative
frequencies of alleles in a
population’s gene pool.
- Evolution acts on populations
through generations – not on
individuals.
- Evolution is CHANGE OVER TIME.
What’s a theory?
• Theories are not educated guesses;
they are based on many observations
and investigations.
PBS Video Clips
• http://gpb.pbslearningmedia.org/resour
ce/mck03.pd.sci.evtheory/isntevolution-just-a-theory/
• Watch “Isn’t Evolution Just a Theory?”
Evidence of Evolution
1.
2.
3.
4.
5.
Fossils
Comparative Anatomy
Comparative Embryology
Comparative Biochemistry
Geographical Distribution
Evidence of Evolution
1. Fossil Record:
Fossils -
preserved remains of ancient
organisms
The fossil record is the most significant evidence
for evolutionary change. Shows that ancient
species share similarities with species that now
exist on Earth.
Glyptodont
Armadillo
• The fossil record
is an important
source of
information for
determining the
ancestry of
organisms and
the patterns of
evolution.
2. Comparative Anatomy
-
the study of similarities and differences in the
anatomy (body plan) of an organism:
a. Homologous Structures – anatomically similar
structures inherited from a common ancestor.
b. Vestigial Structures – structures that are the
reduced forms of functional structures in other
organisms (wisdom teeth, coccyx, appendix)
c. Analogous Structures – similar structures not
inherited through common ancestors.
Homologous Structures
Structures that have different mature forms but develop from the
Same embryonic structures suggest a common ancestor:
Vestigial Structures
The wings of kiwis
are too small to be
of any use in flight.
Wisdom Teeth
Mammals once walked on
land
Once used to chew leaves,
nuts, and meats
Appendix
The coccyx (tailbone) is the
remnant of a lost tail.
Once used for digesting cellulose
Analogous Structures
Wing of an eagle and the wing
of a beetle have the same
function but are constructed in
different ways from different
material.
Insect wings composed of
Chitin.
Bird wings composed of bone and muscle
3. Comparative Embryology
The study of similarities and differences
between the embryos of different species.
Bird Embryo
Human Embryo
Embryological Similarities
a) The early embryo stages of all vertebrates (with
a backbone) is very similar.
4. Comparative Biochemistry
common ancestry can be seen in
biochemical molecules.
- similarities exist in the amino acid
sequences (order) of proteins or the
nucleotide sequences of DNA
- the closer an organism’s amino acid
sequences, or DNA sequences, the more
likely they are to be related.
Organism
Amino Acid Sequence
Chimpanzee
Serine-Valine-Leucine-Stop
Human
Serine-Valine-Proline-Stop
Fruit Fly
Serine-Lysine-Valine-Stop
–
5.
Geographic Distribution
- 60,000 years ago, over 100 species of
marsupials only existed in Australia.
This is because Australia was a
continent isolated from the rest of the
world.
Geographic Distribution of the
Ratite Birds due to Plate Tectonics