Chapter 17.1Ideas about Evolution

Mr. Perez

Important Vocabulary

• Gene• Species• Evolution• Natural selection• Variation• Adaptation

• Gradualism• Punctuated

equilibrium

Early Models of Evolution

• A species is a group of organisms that share similar characteristics and can reproduce among themselves to produce fertile offspring

• Many characteristics of a species are inherited when they pass from parent to offspring

• Change in these inherited characteristics over time is evolution

Species

Hypothesis of Acquired Characteristics

• Remember, a hypothesis is an educated guess.

• Jean Baptiste Lamarck (1809)• Proposed the hypothesis that

characteristics, or traits, developed during a parent organism’s lifetime are inherited by its offspring

• Evidence did not support this hypothesis

Lamarck’s Hypothesis

Darwin’s Model of Evolution

• Charles Darwin sailed on the HMS Beagle from England to the South American coast in December 1831

• He recorded observations about the plants and animals he saw– he was amazed by the variety of life on the Galapagos Islands

• Darwin hypothesized that the plants and animals on the Galapagos Islands originally must have come from Central and South America

Darwin’s Observations• Darwin observed 13 species of finches on the

Galapagos Islands• All were similar EXCEPT FOR• Body size• Eating habits• Beaks shape

• He also noted that these finch species were similar to one finch species on the South American coast

• Darwin reasoned that the Galapagos finches competed for food. Finches with beak shapes that allowed them to eat food, survived longer and produced offspring. After generations, these groups became separate species

Natural Selection• After his voyage:• Darwin returned to England to

review his observations• Collected evidence on

inherited traits by breeding racing pigeons

• Studied breeds of dogs and varieties of flowers

• In 1859, his theory of evolution was published in the book Origin of Species

Darwin’s Theory

• “Theory of evolution by natural selection”• Natural selection means that organisms

with traits best suited to their environment are more likely to survive and reproduce

• Populations are all the individuals of a species living in the same area• Members of a population compete for living

space, food and other resources

Principles of Natural Selection

1. Variation exists among individuals within species

2. Organisms produce more offspring than the environment can handle

3. Competition exists among individuals4. The organisms whose variations best fit

them to the environment are the ones who are most likely to survive, reproduce and pass those desirable variations on the next generations

Variation and Adaptation

• Variations are inherited traits that makes an individual different from other members of the species• They result from mutations, or permanent

changes in an organism’s genes• Genes are sections of DNA that contain

instructions for making specific proteins

• Adaptations are any variation that makes an organism better suited to its environment

Changes in the Sources of Genes

• The genetic makeup of a species might change its appearance• Example: Seed-eating finches in the

Galapagos had their genetic make up change, causing their beak size and shape to change

• Environment factors bring about changes• New individuals entering an existing

population can also bring change

Geographic Isolation• Mountains, lakes or other geologic features isolate

(separate) a small number of individuals from the rest of the population

• Over several generation, variations may rise in the smaller population than in the bigger population

• Gene mutations can also occur, adding variation• Over time, the two populations can become so

different that they can no longer breed with each other.

Geographic Isolation

Videos

Natural Selection http://learn.genetics.utah.edu/content/variation/artificial/ Variationhttp://learn.genetics.utah.edu/content/variation/sources/

Classwork Questions

1. Compare Lamarck’s and Darwin’s ideas about how evolution takes place.

2. Why are variations important to understanding change in a population over time?

3. What adaptations would be helpful to an animal that was moved to the Arctic?

4. How does geographic isolation contribute to evolution?

5. Next slide…

STOP HERE

• Stop here, save the rest for next class… BRING M&Ms to class by (A) 2/11 or (B) 2/12

Speed of Evolution

• Scientists do not agree on how quickly evolution occurs.• Some hypothesize that it is a slow and long

process• Others hypothesize that evolution can happen

quickly

• Evidence supports both:1. Gradualism2. Punctuated equilibrium

Gradualism• Darwin hypothesized that evolution takes place

very slowly• The model the describes evolution as a slow,

ongoing process by which one species changes to a new species is called gradualism

• According to the model, a continuing series of mutations and variations over time will result in a new species• Fossil evidence shows an intermediate species,

indicating a gradual change

Punctuated Equilibrium

• However, for some species the fossil record shows few intermediate forms– one species suddenly changes into another

• In the punctuated equilibrium model, evolution comes about when the mutation of a few genes results in the appearance of a new species over a relatively short period of time• The fossil record also gives examples of this

type of evolution

Punctuated Equilibrium Today

• Many bacteria have changed in a few decades• The antibiotic penicillin,

originally came from a fungus• Many bacteria species that were

once killed by penicillin are no longer harmed by it– they have developed a resistance

• This fast development of penicillin-resistance in bacteria supports the model of punctuated equilibrium

Videos

• http://www.pbs.org/wgbh/evolution/educators/course/session5/elaborate_c.html

• http://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0078802849/383939/gradualism_Punctuated_Equilibrium.swf::Gradualism%20and%20Punctuated%20Equilibrium

Classwork Questions

1. How does gradualism differ from punctuated equilibrium?

2. Use this figure to draw a concept map that shows how raccoons, red pandas, polar bears and black bears are related to a common ancestor.

Resources

• Florida Science Grade 8

Glencoe Science & McGraw Hill Publishing• Google Images