Final Stretch!
Who was Charles Darwin?
HW: Begin Evolution Study Guide w/Word Bank
Agenda: 1. Turn in Genetic Disorder Brochures
2. Discuss EOCT Review Tue & Thur
3. Discussion: Charles Darwin and Theory of Evolution
Georgia Performance Standards:
SB 5: Evaluate the role of natural selection in the theory of evolution
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Darwin on the HMS Beagle
 His job was to collect biological and geological
specimens during the ship’s travel.
What can explain the large extent of
biological diversity on earth?
• Evolution – change over time
– How life has changed over time
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
The Galápagos Islands
 Darwin began to collect mockingbirds, finches, &
other animals on the 4 islands.
 He noticed that the different islands seemed to
have their own, slightly different varieties of
animals.
 Later called descent with modification
The Galapagos Islands
• West of South America
• Group of islands each with
different climates
• Tortoises varied from island to
island in neck length and shell
shape
• Finches varied in beak shape
• Characteristics of plants and
animals varied from island to
island
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Evolution
15.1 Darwin’s Theory of Natural Selection
Darwin Continued His Studies
 Darwin inferred that if humans could change
species by artificial selection, then perhaps the
same process could work in nature.
 Think of Biotechnology and Agricultural
Engineering today!!
Journal Entry January 7, 2010
1.How life has changed over time is:
a.Natural Selection b. Descent with modification c. Evolution
2. According to Darwin, the fact that plants & animals may look similar
but show variation is due to
a. Natural Selection b. Descent with modification c. Evolution
3. The process, or driving force, that causes organism to gradually
change in response to their environment is:
a.Natural Selection b. Descent with modification c. Evolution
4. The use of biotechnology today can be considered an example of:
a. Natural Selection b. Artificial Selection
c. Derived trait
5. Charles Darwin took his voyage aboard the HMS _______________
and did most of his research in______________.
a. Bagel; Australia
b. Evolution; South Africa c. Beagle; Galapagos
What did Darwin call the process by which an individual changes over time?
Agenda: 1. Review: Natural Selection
2. Discuss Support/Evidence for Evolution
Georgia Performance Standards:
SB 5: Evaluate the role of natural selection in the theory of evolution
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Natural Selection
 Individuals in a population show variations.
 Variations can be inherited.
 Organisms have more offspring than can survive with
available resources.
 Variations that increase reproductive success will
have a greater chance of being passed on.
 “Survival of the Fittest”
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
The Origin of Species
 Darwin published On the Origin of Species by
Means of Natural Selection in 1859.
 It is a means of explaining how evolution works.
Lamarck’s Theory
•
•
•
•
Pre-Darwin scientist
Inheritance of acquired traits due to use and disuse of features
Structures not used would shrivel and disappear
Early scientist to recognize that organisms had changed over
time
Evolution
Chapter 15
15.2 Evidence of Evolution
Support for Evolution
 The fossil record
 Provide a record of species that lived long ago.
 Show that ancient species share similarities with species
that now live.
Glyptodont
Armadillo
Chapter 15
Evolution
15.2 Evidence of Evolution
Support for Evolution
 Biological Molecules
 Nucleotide changes (mutation) cause a change in amino
acid sequences
 Species with a common ancestor will have fewer
differences in their genes and amino acids.
Chapter 15
Evolution
15.2 Evidence of Evolution
Support for Evolution
 Geographic Distribution
 The distribution of plants and animals that
Darwin saw first suggested evolution to
Darwin.
Rabbit
Mara
Chapter 15
Evolution
15.2 Evidence of Evolution
 Derived traits are newly evolved features, such as
feathers, that do not appear in the fossils of common
ancestors.
 Ancestral traits are more primitive features, such as teeth
and tails, that do appear in ancestral forms.
Homologous Structures
 Anatomically similar structures inherited from
a common ancestor
Chapter 15
Evolution
Analogous Structures
 Same function but different
structure
 NOT inherited from
common ancestor.
Chapter 15
Evolution
15.2 Evidence of Evolution
Vestigial Structures
 Structures that are the reduced
forms of functional structures in
other organisms.
 Evolutionary theory
predicts that features of ancestors that no
longer have a function for that species will
become smaller over time until they are lost.
Chapter 15
Evolution
15.2 Evidence of Evolution
 Comparisons of the similarities in organisms are
seen in comparative anatomy and in the fossil
record.
 Organisms with closely related morphological
features have more closely related molecular
features.
More Terms
• Fitness – ability of an individual to
survive and reproduce in a specific
environment
• Adaptation – inherited characteristic
that increases an organism’s chance
of survival
–Can be physical traits as well as
behavioral traits
Chapter 15
Evolution
15.2 Evidence of Evolution
Camouflage
 Allows organisms to
become almost
invisible to predators
Leafy sea dragon
Chapter 15
Evolution
15.2 Evidence of Evolution
Mimicry
 One species evolves to resemble another species.
Western coral snake
California kingsnake
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Natural Selection
 Acts to select the
individuals that
are best adapted
for survival and
reproduction
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
 Stabilizing selection operates to eliminate
extreme expressions of a trait when the
average expression leads to higher fitness.
 Ex. Siberian Husky
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
 Directional selection makes an organism more
fit.
 Favors the extremes
 Ex. Greyhound Dog
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
 Disruptive selection is a process that splits a
population into two groups.
 Ex. Black, White, & Gray Rabbits
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Mechanisms of Evolution
 Population genetics
 Hardy-Weinberg principle states that when allelic
frequencies remain constant, a population is in
genetic equilibrium.
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Write these down & know these!
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Genetic Drift
 A change in the allelic frequencies in a population
that is due to chance and random mating
 In smaller populations, the effects of genetic drift
become more pronounced, and the chance of losing
an allele becomes greater.
 Marble Example
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Nonrandom Mating
 Promotes inbreeding & could lead to a change in
allelic proportions favoring individuals that are
homozygous for particular traits
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Founder Effect
 The loss of genetic variation that occurs when a
new population is established by a very small
number of individuals from a larger population
Island 1
Island 2
Mainland
Island 3
Evolution
15.3 Shaping Evolutionary Theory
Bottleneck
 a significant percentage of a population or species
is killed or otherwise prevented from reproducing
and can rebound later
 Often caused by a natural disaster
What is a gene pool?
• Gene pool – combined genetic
info of all members of a
population
– Contains two of more alleles
(genes) for the same trait
– Allele frequency – number of
times an allele occurs in a
gene pool compared to the
number of times another
allele occurs (expressed in
percents)
Section 16-1
Relative Frequencies of Alleles
allele for
brown fur
allele for
black fur
Sample Population
48%
heterozygous
black
36%
homozygous
brown
Frequency of Alleles
16%
homozygous
black
Gene Flow
• Genes entering or leaving a population
• AKA. Migration
– Emigration Genes LEAVING a population
– Immigration INCOMING genes in a population
What are sources for genetic variation?
• Mutations – random change in the DNA, may
cause evolution in future populations
• Genetic shuffling – occurs in meiosis when
gametes are formed
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
 Sexual selection operates in populations where
males and females differ significantly in
appearance.
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
 Prezygotic isolation
prevents reproduction
by making fertilization
unlikely.
•In behavioral isolation, patterns of
courtship may be different.
•In temporal isolation, different groups
may not be reproductively mature at the
same season, or month, or year.
•In ecological isolation, not in the same
habitat where they are likely to meet.
Eastern meadowlark and Western meadowlark
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
 Postzygotic isolation occurs when fertilization
has occurred but
a hybrid offspring
cannot develop
or reproduce.
 Prevents offspring
survival or
reproduction
Liger
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Allopatric Speciation
 A physical barrier divides one population into
two or more populations.
Abert squirrel
Kaibab squirrel
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Sympatric Speciation
 A species evolves into a new species without a
physical barrier.
 The ancestor species and the new species live
side by side during the speciation process.
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Adaptive Radiation
 Can occur in a relatively short time when one species
gives rise to
many different
species in
response to the
creation of new
habitat or some
other ecological
opportunity
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Coevolution
 The relationship between two species might be
so close that the evolution of one species
affects the evolution of the other species.
 Mutualism
 Coevolutionary arms race
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Convergent Evolution
 Unrelated species
evolve similar traits
even though they live
in different parts of
the world.
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Rate of Speciation
 Evolution proceeds in small, gradual steps
according to a theory called gradualism.
 Punctuated equilibrium explains rapid spurts of
genetic change causing species to diverge
quickly.
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory