1. Unit 8 Evolution

2. What is Evolution?
A well-supported scientific theory stating that
organisms change over time

3. Evidence in stone
Preserved remains of a
once living organism is
called a FOSSIL
Fossil evidence supported
that organisms changed
gradually

4. Anatomical Evidence
Comparative Anatomy: study of
similarities and differences between
organisms
Homologous Structures
Analogous Structures
Vestigial Organs

5. Homologous Structures
As similar organisms adapt to different
environments, the function of their appendages
changed
 A bird’s arms became
wings to flap
 A human’s arm is used
to pick-up, carry, grasp,
etc…
 A horse’s arm became
a fore-leg to run on

6. Analogous Structures
Different organisms began living in similar
environments, their appendages evolved to
perform the same function
 A butterfly has wings to fly that
are made from an exoskeleton
 A sparrow has wings to fly that
have an endoskeleton
Butterfly Bird

7. Vestigial Structures
Structures which remain in organisms but have
no obvious function
Leg bones in snakes and whales
Appendix in humans **
Ear muscles in humans

8. Comparative Embryology
Examining the
embryos of
organisms
Organisms with
similar embryos are
thought to be more
closely related

9. Biochemical Evidence
(aka Molecular Biology)
Comparison of the amino acid and DNA
sequences
 Chimp and human hemoglobin are VERY similar

10. Genetic Evidence
DNA passes on traits
When mutations occur the genes and
chromosomes can change
Humans have imposed change through
selective breeding
The higher the percentage of similarities
the closer the relationship between two
organisms

11. Jean Baptiste de Lamark
First to recognize that
organisms change
Published his hypotheses
in 1809
Theory was disproved!

12. Jean Baptiste de Lamark
3 Key Assumptions:
Desire to Change: organisms have an
inborn urge to better themselves
Law of Use and Disuse: body parts that are
used will develop; those not used will
become smaller/disappear
Inheritance of Acquired Characteristics:
organisms pass on traits acquired during
their lifetime

13. Charles Darwin
Credited for the theory of evolution
HMS Beagle sailed in 1831 – Galapagos Islands
Published Origin of Species in 1858

14. Darwin’s Observations
Observed tortoises,
iguanas, and finches
The islands had different
climates and vegetation
The animals were
similar… but had
noticeable differences
WHY?

15. Darwin’s Assumptions
Variations
 Differences among members of the same species
Struggle for Existence
 Predation and competition
Overproduction
 More offspring are produced than will survive
Survival of the Fittest (Natural Selection)
 Individuals best suited for the environment will survive,
reproduce, and pass on traits to their offspring
Descent with Modification
 Principle that species change but descend from common
ancestors

16. Lamark’s Giraffes

17. Darwin’s Theory of Natural Selection
Variations help
members of a species to
survive in a given
environment
The environment selects
the beneficial adaptation
and over time this trait
will become more
prevelant

18. Darwin’s Finches

19. Fossil Formation
Water carries small Dead organisms are buried The preserved remains
rock particles to lakes by layers of sediment, may later be discovered
and seas which forms new rock and studied.

20. Fossil Record
Preserved remains of a once living
organism is called a FOSSIL
IE: amber, sedimentary rock, tar, and ice
Fossil record is incomplete

21. Relative Dating
Used to ESTIMATE
the age of fossils
Older fossils are in
deeper layers of rock

22. Genes and Evolution
In terms of genetics, evolution is the change in
frequency of alleles in a population’s gene
pool
Natural selection leads to change in gene frequency
Molecular clocks use mutation rates to estimate
how recent a common ancestor was

23. Hox Genes
Genes which control an organism’s basic body plan
Anterior/posterior ends
Limbs, wings

24. Genetic Drift
Changes in the gene
pool of a small
population due to
random chance
ex: small group
colonizes a new habitat
– founder effect

25. Speciation
Gradualism – change in species
is slow and steady
Punctuated Equilibrium – long
periods of stability followed by
short periods of rapid change

26. Punctuated Equilibrium vs.
Gradualism

27. Speciation – Isolating Mechanisms
For new species to form, reproductive
isolation needs to occur
Organisms don’t interbreed
- gene pools become separate
- Behavioral, Geographic, Temporal

28. Adaptive Radiation
A single species evolves into many species
Often occurs when a niche opens up

29. Convergent
Evolution
Organisms come to
resemble one another
but evolved
differently
Analogous structures!
Examples:
Dolphins and sharks
Marsupials and mammals

30. Coevolution
Organisms with close ecological relationships
evolve together
Pollinators and flowers

31. Ancient Earth
Atmosphere was composed of gases:
CO2, N2, water vapor, CH4, H2S
No O2
Earth formed ~4.6 billion years ago

32. First Organic Molecules
1950’s Miller & Urey
reproduced
conditions of ancient
Earth
Electric sparks
simulated lightning
Amino acids began to
form

33. First Cell

34. Oxygen Accumulation in
Atmosphere

35. What is a Primate?
Binocular Vision
Developed brain
Long fingers & toes
Rotating shoulders

36. What makes us Human?
Characteristics of
the Hominine Family
Bipedal
Opposable Thumbs
Larger Brains

37. Did we evolve from chimps?

38. Hominine Evolution
Ardipithecus ramedus “Ardi”, 4.4 mya
Australopithecus afarensis “Lucy”, 3.2 mya
Homo habilis “handy man”, ≈ 2 mya
Used tools, first of the genus Homo
Homo erectus, “Java Man”, ≈ 1.6 mya
1st to use fire
Homo neanderthalensis ≈ 200,000 years ago
Homo sapien
Modern Human ≈ 100,000 years ago

39. Family Tree or Bush?