Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15: Theory of Evolution Chapter 15 Section I History of Evolutionary Thought Section.

Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 15: Theory of EvolutionChapter 15

Section I History of Evolutionary Thought

Section II Evidence of Evolution

Section III Evolution in Action

http://www.probe.org/galapagos/web-ray_tortoise.jpg

http://www.geol.umd.edu/~jmerck/galsite/research/projects/fitz/currents.gif


Chapter 15

A. The Idea of Evolution

• Evolution is the process of change in the inherited characteristics within populations over generations such that new types of organisms develop from preexisting types.

I. Section 15-1 History of Evolutionary Thought


Chapter 15Evolutionary Relationships Between Whales and Hoofed Mammals


Chapter 15• Ideas of Darwin’s Time– Most people of the time believed species were

permanent & unchanging.

– Scientific understanding of evolution began to develop in the 17th and 18th centuries as geologists and naturalists compared geologic processes and living and fossil organisms around the world.

–Study of “strata”- the layers of rock• Inferred that oldest rock were made first &

would be found on the bottom• Oldest rock would have oldest fossils


Ideas about Geology

• Georges Cuvier –catastrophism- sudden catastrophic events caused mass extinction

• Charles Lyell –uniformitarianism- same mechanisms that shaped Earth’s surface in the past continue to work today.


Darwin was not the first naturalist to propose that species changed over time into new species—that life evolves.

Jean Baptista Lamarck -Theory of Evolution-proposed that individuals could develop traits during their

lifetime, as a result of experience or behavior-idea was: inheritance of acquired characteristics as a mechanism for evolution. Lamarck believed that the

long necks of giraffes evolved as generations of giraffes reached for ever higher leaves.

Lamarck also believed more simple life forms evolved into more complex life forms


Chapter 15B. Darwin’s IdeasDarwin’s Voyage- ship: HMS Beagle

•Studied many things on the islands passed by boat.

•In part because he was so seasick he wanted to get off the boat.

•Basis for his life work.


Chapter 15Darwin’s Ideas

• Descent with Modification– Darwin wrote On the Origin of Species by

Means of Natural Selection.– argued that descent with modification occurs– all species descended from common ancestors– natural selection is the mechanism for evolution.

• Natural Selection– Organisms in a population adapt to their

environment as the proportion of individuals with genes for favorable traits increases.

– Those individuals that pass on more genes are considered to have greater fitness.


Chapter 15

Natural Selection


Darwin’s Evolutionary Theory

(which he liked to call “natural selection”

not “evolution”)

-over many generations, natural selection causes characteristics of populations to change.

-natural selection is responsible for evolution.

-organisms with the best adaptations are more likely to survive & reproduce.


What is survival of the fittest?

• It is NOT- “King of the Jungle”- with the meanest, biggest, most muscular animal killing all the smaller ones.

• Example- 2 dogs- One is the perfect specimen- shiny fur, wins shows, smart, etc. & the other is small, ugly, mangy, living in the alley.

The ugly dog visits every female dog in the county and reproduces many times, but the perfect dog never has puppies-

• which dog will pass on his traits?


Summary: 4 Main Parts of Darwin’s Reasoning

• 1. Overproduction- more offspring are produced than can survive

• 2. Genetic Variation- within a population, individuals have different traits

• 3. Struggle to Survive- individuals must compete with each other to exist.

• 4. Differential Reproduction- Organisms with the best adaptations to environment more likely to survive & reproduce.


Chapter 15II. Section 9-2 Evidence of Evolution

• Evolutionary theories are supported when several kinds of evidence support similar conclusions.

Evidence of evolution can be found by comparing several kinds of data:

A. The fossil record B. Biogeography C. Anatomy and DevelopmentD. Biological molecules.


Chapter 15A. The Fossil Record1. The Age of Fossils

– Geologic evidence supports theories about the age and development of Earth.

– Superposition- if rock layers have not been disturbed, lower strata is oldest.– Relative Age - compare to other fossils– Absolute Age - use radiometric dating

2. The Distribution of Fossils– Fossil record shows the types & distribution of organisms

on Earth have changed over time.

3. Transitional Species– Fossils of transitional species show evidence of descent

with modification.


Evidence of Whale EvolutionChapter 15

Skeletons show sequence of

transitional species that

support the hypothesis that

whales evolved from 4 legged

land-dwelling mammals.

Note: tiny, non-functioning hip

bones in modern whales.


Chapter 15B. Biogeography

• Biogeography - the study of the locations of organisms around the world, provides evidence of descent with modification.

• Example: Australia- The Marsupials there resemble rodents, wolves, cats, anteaters of other continents. May be evidence that these species evolved in isolation.


Chapter 15C. Anatomy and Physiology

• Analogous structures -are similar in function but have different evolutionary origins.

(Does not show evidence for evolution)

• Homologous structures have a common evolutionary origin. (shows evidence of evolution)

• Vestigial structure- structures that are reduced in size & function- but may have been complete & functional in an organism’s ancestor. (shows evidence of evolution)


Chapter 15Forelimbs of Vertebrates

The organisms show

Homologous parts-

Anatomical structures

that have related structure,even if

the function is different.

Shows a relatedness- used to

show a common ancestor.


Homologous structures

Comparing the structural features found in different organisms reveals a basic similarity.

example is the forelimb of mammals - Although function is quite different, they are similar structurally.


Analogous structures

• We must look at structures that look & function the same but are not derived from the same embryonic tissue.

• These features do not show recent, related ancestry.


Vestigial structures

• Features which serve no useful function any longer in the organism.

• Examples: the pelvis bone in the whale, tailbone & appendix in humans, pelvis & leg bones in some snakes, etc


D. Biological Molecules-Chromosomes & Macromolecules

• Compare Macromolecules like DNA, RNA & Proteins. • Can indicate a common evolutionary history.

• Example- the number of differences in amino acids is a clue to how long ago 2 species “Diverged”

• Divergent Evolution- 2 species become more and more dissimilar.

• Convergent Evolution- Species which have different ancestors, but have become more similar


Chapter 15Section 2 Evidence of Evolution

Hemoglobin Comparison


Proteins indicate degree of relatedness. Differences - Amino Acids in Protein Cytochrome C

• (From Atlas of Protein Sequence and Structure, 1967-68 by Margaret O. Dayhoff

Number of different amino acids found in human cytochrome C as opposed to selected organisms

Organism # of amino acids different compared to humans

Human 0 Self (Family Hominidae, Order Primates)

Monkey 1 Different family (Pongidae), same order (Primates)

Pig, bovine, sheep 10 Different order (Carnivora), same class (Mammalia)

Horse 12

Dog 11

Rabbit 9

Chicken, Turkey 13 Different class (Aves), same phylum (Chordata) - homeothermic

Duck 11

Rattlesnake 14 Different class (Reptilia), same phylum (Chordata) - poikilothermic

Turtle 15

Tuna 21 Different class (Ostheichthys), same phylum (Chordata) - poikilothermic

Moth 31 Different phylum (Arthropoda), same Kingdom (Animalia)

Candida fungus 51 Different Kingdom (Fungi)


What is a Phylogenic Tree ?

• A family tree that shows evolutionary relationships thought to exist among organisms.

• Is a hypothesis about the relationships.

• Is subject to change - as more evidence is learned.



Chapter 15

Developing Theory

• Modern scientists integrate Darwin’s theory with other advances in biological knowledge.

• Theories and hypotheses about evolution continue to be proposed and investigated.


Chapter 15

Case Study: Caribbean Anole Lizards (p 308) text

• Convergent evolution - organisms that are not closely related resemble each other because they have responded to similar environments.

• Divergence and Radiation– In divergent evolution, related populations become

less similar as they respond to different environments.– Adaptive radiation is the divergent evolution of a

single group of organisms in a new environment.

Section 3 Evolution in Action


Chapter 15

Natural Selection of Anole Lizard Species


Chapter 15

Artificial selection.- when a human breeder chooses individuals that will parent the next generation.

(ex- dogs)

Co-evolution – When 2 or more species have adapted to each other’s influence.

(ex- flowering plants & pollen carrying insects


Chapter 15

Coevolution

• The increasing occurrence of antibiotic resistance among bacteria is an example of coevolution in progress.

Section 3 Evolution in Action


Question: Beak size in these finches is

correlated to the size of seeds they can eat. What can be inferred from the graph?

1. In wet years, the finches that survive are mostly those that can eat larger seeds.

2. In dry years, the finches that survive are mostly those that can eat larger seeds.

3. In all years, the finches that survive are mostly those that can eat larger seeds.

4. In all years, the finches that survive are mostly those that can eat smaller seeds.

Chapter 15

The graph below shows the variation in average beak size in a group of finches in the Galápagos Islands over time. These finches eat mostly seeds. Use the graph to answer the question that follows.

Answer- In dry years, the finches that survive are mostly those that can eat larger seeds.


Question:What does the diagram

imply about warbler finches and armadillos?

1. They are unrelated.

2. They are equally related to glyptodonts.

3. They share a common ancestor.

4. They did not evolve from older forms of life.

Chapter 15

The diagram below shows possible evolutionary relationships between some organisms. Use the diagram to answer the question that follows.

Answer: They share a common ancestor.

Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15: Theory of Evolution Chapter 15 Section I History of Evolutionary Thought Section.

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