Theory of Evolution
Chapter 15
Introduction: Isn’t Evolution
Just a Theory?
Jean-Baptiste de Lamarck
● French scientist - Suggested that acquired
traits were inherited through choosing to use or not
use parts of their bodies.
● He believed organisms have a desire to become more
complex and perfect and they would then pass these
traits onto their offspring.
● This is known as the Theory of Acquired Characteristics.
Charles Darwin
● English Naturalist - Developed Theory of Evolution
based on Natural Selection
● Sailed around the world as a naturalist on HMS Beagle
● Wrote a groundbreaking book “On the Origin of
Species” published in 1839
Charles Darwin
● Notable Stop on Voyage - Galapagos Islands
● Plants and animals resembled the species in South
America
●Not identical, but similar
● Changed once they reached the islands
● Descent with modification (Natural Selection)
● Change over time = new species = evolution
Video: Who was Charles Darwin?
Lamarck vs. Darwin
Artificial Selection
● Directed breeding to produce desired traits in
offspring.
●
Natural Selection
● When an organism with a favorable variation
survives and passes on that variation to the
next generation
● Some competitors in the struggle for survival
are better equipped than others.
● Those less equipped will die:
● Not able to reproduce, so their genes die with
them
● Weeded out from the gene pool
Video: How Does Evolution
Really Work?
4 Principles of Natural Selection
1. Variation: Variation exists within the genes of
every population or species
2. Inheritance: Variations are passed from parents
to offspring
4 Principles of Natural Selection
3. Differential survival (Survival of the Fittest):
populations produce more offspring than can
survive. Some individuals with a trait are more
likely to survive and reproduce than those
without the trait.
4. Adaptation- Reproductive advantage: Some
variations allow the organism that possesses
them to have more offspring than the organism
that does not possess them
Natural Selection
● Given enough time, natural selection could
modify a population enough to produce a new
species.
● Evolution takes place because of natural
selection.
Evidence of Evolution
• Theory of evolution states that all organisms
on Earth have descended from a common
ancestor
• The following serve as evidence of evolution:
●Fossils
●Comparative Anatomy
●Comparative Embryology
●Comparative Biochemistry
1. Fossils
• Fossil record shows how a
species has changed over time by
comparing it to modern species
• Fossils can provide us evidence
about:
●Anatomy (size, shape, bone
structure)
●Habitat (where they once lived)
●Diet (what they ate)
1. Fossils
2. Comparative Anatomy
• Compares traits found in different organisms
to see if they share a common ancestor
2. Comparative Anatomy
Homologous Structures Analogous Structures
• Structure with a common
evolutionary
• Same structure and/or same
function
• Share a common ancestor
• Structure that do not have a
common evolutionary origin
• Different structure, but
similar in function
• Have different ancestors
Homologous or Analogous?
2. Comparative Anatomy
• Vestigial structure - a structure in a present
day organism that no longer has a
purpose/function, but was probably useful to
an ancestor
• Can you think of
other examples?
The femur and pelvis of a whale are vestigial
structures. They do not help the whale, but
may have helped its ancestors.
Vestigial Structures in Humans
• Appendix
• Tail bone
• Goosebumps
• Wisdom Teeth
C. Comparative Embryology
• Looking at evolutionary
relationships between
vertebrate embryos
• Embryos – the earliest
stage of growth and
development in an
animal
C. Comparative Embryology
1.
2.
3.
4.
5.
6.
7.
Can you match any of these early stage embryos with
the names of the organisms listed below? If so, what
are your guesses?
Rabbit
Human
Cow
Fish
Salamander
Tortoise
Pig
Chicken
8.
Comparative Embryology
Fish
Salamander Tortoise Chicken
Pig
Cow
Rabbit
Human
Which embryo is least like the
others?
D. Comparative Biochemistry
• Using biological molecules to see evolutionary
relationships through similar patterns in DNA
or amino acid sequences.
●The more closely related a species is, the
greater the number of sequences will be
shared.
D. Comparative Biochemistry
Which is most closely related to the Human?
D. Comparative Biochemistry
Which is most distantly related to the Human?
Video: How Do We Know
Evolution Happens?
Fitness
● Measure of the relative contribution that an
individual makes to the next generation.
● Who will survive?
● Who will produce the most offspring?
● Whose offspring will most likely survive to
produce viable offspring?
Adaptation
● Trait shaped by natural selection that increases
an organism’s reproductive success
Choose one of the organisms and explain its
adaptation?
Camouflage
● An adaptation that allows an organism to blend
in with its surroundings
Mimicry
● An adaptation where one species evolves to
look like another
● Why would this be beneficial?
Mimicry Example: Yellow Jacket
wasp and the syrphid fly
Mimic Octopus Video
Mutations
● Changes in the DNA
● When too many changes occur, the allele
frequency in a population will change
Selection of Traits
● Stabilizing Selection: All extremes are
eliminated
● The average expression leads to higher fitness
● Directional Selection: Increase in either of the
extremes of a trait
● One of the extreme traits lead to higher fitness
● Disruptive Selection: Increase in BOTH of the
extremes of a trait
● Both of the extreme traits lead to higher fitness
Selection of Traits
Directional Selection
● Peppered Moths of England during the
Industrial Revolution
● Industrial melanism - darkening of
populations over time in response to
industrial pollution.
Peppered Moth Video
Species
● A group of similar organisms that can breed
and produce fertile offspring
Reproductive Isolation
● The inability of a species to breed successfully
with related species
● Leads to speciation
Adaptive Radiation
● One species evolves into several other species
● All occupy the same habitat, adapt to different
niches
Coevolution
● Species evolve in close relationships with
other species
● Old world swallowtail caterpillar and fringed
rue
● Garter snake and rough-skinned newt
● Yucca moth and yucca plant
Convergent Evolution
● Organisms not closely related independently
evolve similar traits.
Pace of Evolution
● Gradualism: Slow
● Many generations
● Evolution proceeds
in a small gradual
step
● Punctuated
Equilibrium: Random
● Rapid spurts of
genetic change cause
a species to change
(diverge) quickly