Theory of Evolution Evolution is the change in
- Slides: 34
Theory of Evolution
Evolution is the change in allele frequencies in a population over time.
Remember alleles? Alleles are the different variations of a particular genetic trait. Allelic frequency deals with how often a particular allele appears in a population.
Allelic Frequency 12 green alleles and 8 brown alleles in this population
Jean Baptiste Lamarck French Naturalist 1809 - published ideas on evolution
Lamarck’s Hypothesis During organism’s lifetime, physical features increase or decrease in size based on use disuse Organisms pass down acquired traits to offspring
Lamarck’s Hypothesis Fiddler Crabs Copyright Pearson Prentice Hall
Lamarck’s Hypothesis Copyright Pearson Prentice Hall
Believed that those parts of the body used extensively would become bigger and stronger and would be passed to offspring.
Those body parts that were not used would disappear l Legless salamanders
Thomas Malthus - 1798 Pop. growth limited by disease, famine, war Human population increasing faster than supply of resources
Charles Lyell Leading geologist of Darwin’s time. Believed the Earth was very old and had changed slowly over long periods of time.
Charles Darwin The theory of evolution proposed by Darwin explains how evolution works. He realized that there is a struggle for existence among individuals.
Voyage on the Beagle Darwin was 22 when he set sail on the HMS Beagle as the ship’s naturalist. Spent 5 yrs observing and collecting specimens from jungles, grasslands, desert, etc.
Galapagos Islands of relatively recent volcanic origin that lie on the equator about 900 km west of the S. American coast.
Darwin noticed…
Darwin observed the various adaptations of plants and animals that inhabited such diverse environments.
Darwin’s Finches Darwin collected 13 types of finches that, although quite similar seemed to be different species. Some were unique to individual islands while others were on two or more islands that were close together.
After the Voyage… Spent 20+ years studying collections Results: variations w/in same species enable some to survive & reproduce, while those w/other variations do NOT survive or reproduce
Also studied… Farmers’ breeding of plants & animals with desirable traits Artificial selection selective breeding of plants/animals w/desirable traits
Origin of Species In 1859, Darwin published his book, The Origin of Species by means of Natural Selection.
Natural Selection Organisms with favorable variations for a particular environment will survive and reproduce —and pass these variations to offspring. “Survival of fittest” Fitness – ability of an organism to survive & reproduce in its specific environment
For example… If a rabbit lived in an environment where it snowed all the time—what color of fur would be more advantageous? l Why?
Environment determines which traits are advantageous
Main points of Darwin’s theory of natural selection: l Genetic variations exist in populations l Overproduction of offspring– struggle for existence (limited resources) l Organisms best adapted will survive, reproduce and pass traits to next generation. l Ex: hummingbirds with longer beaks.
CONCEPT REVIEW: True or False 1) Changes in the phenotype of a species over time is called evolution. TRUE
CONCEPT REVIEW: True or False 2) An organism can pass down an acquired trait to its offspring. FALSE
Which of the following does not belong with the others? These are people who shaped Darwin’s Thinking. Charl es Lyell Gregor Mendel Thomas Malthus Jean-Baptiste Lamarck
Fill in the missing idea These all describe The main points of Darwin’s theory Populations have genetic variations Struggle for existence There are more offspring than the environment can support Organisms w/favorable variations will survive, reproduce and pass traits to offspring
CONCEPT REVIEW: Multiple Choice A farmer’s use of the best livestock for breeding is an example of A) B) C) D) Natural selection Artificial selection Common descent Extinction
CONCEPT REVIEW: Multiple Choice A farmer’s use of the best livestock for breeding is an example of A) B) C) D) Natural selection Artificial selection Common descent Extinction
Use the main points of Darwin’s theory of natural selection to explain
Natural Selection Video
Are You Able to… Explain how natural selection causes populations to change over time? ? Describe what determines which traits are advantageous? ?
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