Download Lamarck Vs. Darwin

Darwin and Lamarck
Evolution
 What is evolution? A change over time.
Examples of Evolution
Two Main Theories of Evolution
1. Acquired Characteristics
2. Natural Selection
Acquired Characteristics
 Introduced by Jean-Baptiste Lamarck(1744-1829)
 Believed living things on Earth had changed gradually
over time, were still changing, and would keep changing
– not believed by most!
 Living things change so they have a better chance of
surviving in the environment.
 Said animals were “selecting themselves” to survive.
Species never went extinct; they just kept changing.
Theory of Acquired Characteristics
 States that if an individual wanted to change
something about the way its body worked, it could.
 When that individual reproduced, the changes
that it had made during its lifetime would be
passed on to its offspring.
Examples of Lamarck’s Theory of
Acquired Characteristics
 Giraffes’ long necks and elephants’ trunks
 Giraffes that needed longer necks would use it more
and stretch it out. Their babies would then have longer
necks too, and they would then stretch them even more
and pass on even longer necks to their babies.
Why Lamarck’s Theory Is Wrong
 Physical injuries are not passed to offspring
 Skills are not passed to offspring
 Fossil evidence shows organisms have gone extinct
 GENETICS!
Theory of Natural Selection
 Introduced by naturalist (person who studies plant
and animals by observing them) Charles Darwin
(1809-1882)
 Studied animals, especially finches and tortoises, in
the Galapagos Islands
 Also believed living things continuously change to
increase their chance of surviving in their environment.
 Believed nature selected organisms with the best traits
to survive and organisms could become extinct if they
were not well adapted to their environment.
Theory of Natural Selection
 Darwin believed organisms only pass on the traits they
themselves are born with.
 All organisms, even of the same species, are slightly
different from one another. These differences are called
variations.
 Certain variations make some organisms better suited to
their environment than others. Since the ones that are
better adapted have a survival advantage, they also live
longer and are able to reproduce more. Every time they
reproduce they pass their successful traits down to their
offspring.
 “Survival of the Fittest”
The Principles of Natural Selection
 1. Organisms produce more offspring than can survive.
 2. Variations occur among individuals of a species.
 3. Some variations are passed to offspring.
 4. Some variations are helpful. Individuals with
helpful variations survive and reproduce better than
those without these variations.
 5. Over time, the offspring of individuals with helpful
variations make up more of a population and
eventually may become a separate species.
Conclusion