Download Chapter 32 Theories of Evolution

Chapter 32 Theories of Evolution
Introduction
• Biologists have classified more than 1.5 million
species of organisms for far.
• Many scientists estimate that there may be 10
million species of organisms living on earth.
***Review Classification
• What does a Scientific name consist of?
1.
2.
3.
4.
Kingdom order
Class species
Phylum Genus
Genus species
Classification Review
• What is the correct way of writing the
scientific name for a Lion?
1. panthera leo
2. Panthera leo
3. Panthera leo
4. panthera Leo
Introduction cont.
• As we know there are differences between
organisms of different species.
• In addition, there are also differences among
organisms of the same species (variations).
Why are there so many variations
among organisms?
• Evolution is responsible for this great diversity!
• Evolution: the process by which organisms
change over time.
• Until the 19th century, most
scientists believed that
organisms existed as they had
first appeared on earth.
• However, by the 1800’s
geologists were finding and
studying many fossils.
• What do you think these fossils
showed?
• Scientists began wondering
how and why living things may
have changed?
Evolution
Evolution cont.
During this time 2 biologists proposed
a theory on evolution:
Lamarck's Theory
• Proposed his theories in 1809
• 1st hypothesis:
– Organisms develop traits, or characteristics by
the use or disuse of body parts.
• Ex: If the body part is used, it becomes
larger and stronger. If the body part is not
used, it becomes smaller and weaker.
Lamarck's Theory cont.
• 2nd hypothesis:
– Acquired characteristics, or the traits that
organisms develop during their lifetimes, are
passed from parents to their offspring
• Ex: Giraffe
• He didn’t have any observations or evidence to
support his theory.
• Therefore most scientists did not support his
theory.
Lamarck's Theory cont.
Investigations of Charles Darwin
• British Naturalist born in 1809.
• At the age of 22 Darwin voyaged on the HMS
Beagle.
• HMS Beagle went on a mapping and collecting
expedition to South America and the South
Pacific.
What did Darwin observe during his 5 year
voyage?
• How earthquakes and other geological
processes change the land.
• He observed thousands of species of plants
and animals
• Collected fossils
• Notes on all his observations
Darwin’s Finches
Darwin’s Theory of Evolution
• 20 years after his voyage, he published a book
called On the Origin of Species by Means of
Natural Selection.
• What are Darwin’s main ideas about evolution?
1. Overproduction
2. Competition
3. Variations
4. Survival of the Fit
Darwin’s Theory of Evolution cont.
1. Overproduction: Each species produces many
more organisms than can survive and reproduce.
• Ex: Crabs, codfish, salmon, sea turtles
Darwin’s Theory of Evolution cont.
2. Competition: due to overproduction of offspring,
organisms must compete for limited resources
(food, water, & a place to live)
Darwin’s Theory of Evolution cont.
3. Variation: differences among traits, occur
among members of the same species.
Darwin’s Theory of Evolution cont.
4. Survival of the Fit: Organisms with traits that
make them well adapted to their environment
have a better chance to surviving and
reproducing (natural selection).
Darwin’s Theory of Evolution cont.
• Organisms that survive and reproduce pass on
their traits to their offspring.
• As the process of natural selection continues
through many generations, species change
and become better adapted to their
environment.
• As a result, evolution occurs by natural
selection.