1. Chapter 15
Theory of Evolution

2. Theory of Evolution

3. History of Evolutionary Thought
Section 1

4. 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

5. 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

6. 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

7. Darwin’s Ideas

8. 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

9. 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

10. Natural Selection
 Darwin proposed natural selection as the
mechanism for descent with modification

11. 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.

12. 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

13. 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

14. Natural Selection

15. Evidence of Evolution
Section 2

16. The Fossil Record
 Fossil – the remains or traces of an organism
that died long ago
 Among the most powerful evidence of evolution

17. The Age of Fossils
 Relative age – possible to tell a fossil’s age by
comparing it to that of other fossils

18. 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

19. Transitional Species
 The fossil record
shows that species
have differed in a
gradual sequence of
forms over time

20. 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

21. 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

22. Anatomy and Embryology

23. 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

24. 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

25. Evolution in Action
Section 3

26. Convergent Evolution
 Convergent Evolution – the process by which
different species evolve similar traits
 Example: Caribbean Anole Lizards

27. 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?

28. Convergent Evolution
 Each species evolved independently on each
island from different ancestor species

29. 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

30. Artificial Selection
 Artificial Selection –
process when a
human breeder
chooses individuals
that will parent the
next generation

31. 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