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Chapter 15
Theory of Evolution
Theory of Evolution
History of Evolutionary Thought
Section 1
The Idea of Evolution
In the 1830s, Charles Darwin
visited the Galapagos Islands
and noted that groups of
animals varied on each island
Darwin was convinced that
organisms had changed over
time
Proposed the theory of
evolution – development of
new types of organisms from
preexisting types of organisms
over time
Lamarck’s Ideas on Evolution
Jean Baptiste Lamarck supported the idea that
populations of organisms change over time
His idea was the inheritance of acquired
characteristics
No supporting evidence and has been rejected
Darwin’s Ideas
Darwin published a book – On the Origin of
Species by Means of Natural Selection in 1859
proposing a new theory for the way evolution took
place
Goals of the book:
Present the large amount of evidence that evolution occurs
Explain the variety and distribution of organisms on Earth in
terms of natural selection processes that are observable
everyday
Darwin’s Ideas
Descent with Modification
Darwin reviewed evidence that every species –
living or extinct – must have descended by
reproduction from preexisting species and that
species must be able to change over time
First to argue that all species had descended
from only one or a few original kinds of life
Evidence of Descent with
Modification
Galapagos Islands are home
to 13 different species of
finches
Each has a beak that is best
adapted for a certain kind of
food
Darwin suspected that all
descended from one common
ancestor
The ancestors could have
flown from elsewhere after
the islands were formed
Natural Selection
Darwin proposed natural selection as the
mechanism for descent with modification
Natural Selection
Overproduction
More offspring can be produced than can live to
maturity
Genetic Variation
Within a population, individuals have different traits
– some can be inherited. Occasionally, new traits
may appear in a population.
Natural Selection
Struggle to survive
Individuals must compete with each other for
resources
Some variations increase and individual’s chance to
survive and reproduce
Adaptation – a trait that makes an individual successful
in its environment
Natural Selection
Differential Reproduction
Organisms with the best adaptations are most likely
to survive and reproduce
Through inheritance, the adaptations will become
more frequent in a population
Populations may begin to differ as they adapt to
different environments, even if they descended from
the same ancestor
Natural Selection
Evidence of Evolution
Section 2
The Fossil Record
Fossil – the remains or traces of an organism
that died long ago
Among the most powerful evidence of evolution
The Age of Fossils
Relative age – possible to tell a fossil’s age by
comparing it to that of other fossils
The Distribution of Fossils
From the fossil record we can infer:
Different organisms lived at different times
Today’s organisms are different from those of the
past
Fossils found closer together are more like each
other than ones found further away
Where and when different organisms existed
Transitional Species
The fossil record
shows that species
have differed in a
gradual sequence of
forms over time
Biogeography
Biogeography – the study of the locations of
organisms around the world
Darwin and Wallace observed species that
seemed closely related but were adapted to
different environments in nearby regions
They also observed animals that seemed
unrelated but had similar adaptations to similar
environments in regions that were far apart
Anatomy and Embryology
Anatomy – the study of the body structure of
organisms
Embryology – the study of how organisms
develop
As generations passed, different populations of
descendants adapted to different environments
Homologous structures- structures that occur in
different species and that originated by heredity
from a structure in the most recent common
ancestor of the species
Analogous structures – closely related functions
but do not derive from the same ancestral
structure
Anatomy and Embryology
Anatomy and Embryology
Vestigial Structures
– structures that seem
to serve no function
but that resemble
structures with
functional roles in
related organisms
Development of
animal embryos –
some stages of
vertebrate embryo
development are very
alike
Biological Molecules
In all species, DNA and RNA are the molecular
basis for inheritance of traits
Scientists can compare the DNA, RNA, and
proteins from many different organisms and look
for similarities and differences
The greater number of similarities, the more
closely the species are related through a common
ancestor
Evolution in Action
Section 3
Convergent Evolution
Convergent Evolution – the process by which
different species evolve similar traits
Example: Caribbean Anole Lizards
Convergent Evolution
Many different body types on different islands and
different species have the same body types
Lizards that live on tree trunks have stocky bodies
and long legs
Lizards that live on slender twigs have thin bodies,
short legs and tails, and large toe pads
Lizards that live in the grass are slender and have
very long tails
How did all of this happen?
Convergent Evolution
Each species evolved independently on each
island from different ancestor species
Divergent Evolution
Divergent evolution – Process in which
descendants of a single ancestor diversify into
species that each fit different parts of the
environment
Ex: Lizards with genes for large toe pads and short
legs ran so slowly on the trunk and ground that
predators often caught them
Artificial Selection
Artificial Selection –
process when a
human breeder
chooses individuals
that will parent the
next generation
Coevolution
Coevolution – when two or more species have
evolved adaptations to each other’s influence
Ex: Humans develop and use antibiotics to kill
bacteria, many populations of bacteria have evolved
to resist the effects of antibiotics