Evolution & Natural Selection SB5

2 Names you need to know…. Charles Darwin – Father of Evolution Jean Baptist Lamarck – Acquired Characteristics

Lamarck’s contribution Life evolves as environment changes Acquired characteristics (not genetic)

Darwin Connects the Pieces The Origin of Species

Darwin’s Life As a child, he was fascinated with nature At 16 he became a physician Then joined the Beagle for a 5 year voyage

Darwin Observes Collected thousands of plants & animals Each had wondrous adaptations

Galapagos Islands – off the coast of South America

What is evolution? Change in Genetic frequency over time Over a large number of years, evolution produces tremendous diversity in forms of life.

Galapagos Finches

Finch Adaptations

Natural Selection is a Mechanism for Evolution… Has 4 Parts… Fill in the chart…

Big Idea #1 Production of more individuals than the environment can support leads to a struggle for existence - only a fraction of the offspring survive

Big Idea #2 Individuals in a population show variations among others of the same species.

Big Idea #3 Variations that increase reproductive success will be more common in the next generation, with favorable characteristics accumulating over generations SOTF

Big Idea #4 Variations are inherited

So…Natural Selection in a nutshell… Organisms better suited to the environment are more likely to survive and reproduce than organisms less suited to the environment SOTF

Mechanisms of Evolution Bottleneck Effect Analogy-a change in a population’s allele frequencies due to a substantial reduction in population size

Amish – 6 fingers Polydactyly, or extra fingers and toes, is more common among some Amish groups in Pennsylvania. This is because Amish communities were founded by small groups of people. One of the founders of an Amish community was a carrier for a gene that results in extra fingers and toes. The founder then passed this gene onto his or her children. Now, because there weren't many outside contacts, the trait spread in the population.

EX: Cheetah’s have little resistance Cheetahs, which have very little genetic variation, are presumed to have gone through several genetic bottlenecks. Scientists have also found that many cheetahs suffer from genetic defects due to inbreeding, possibly the result of a population bottleneck—a sharp decline—that occurred perhaps as far back as 10,000 years ago.