Timeline of Earth’s History

Recent History of Life on Earth – 600 millions years ago to the Present

– Well-supported testable explanation of something in nature. – What do we mean by “testable”? – In science, nothing is ever proven  ALWAYS possibility of new discoveries! Scientific Theory

Theory of Evolution Evolution is the change in the genes of a population over time Process where modern organisms descended from ancient organisms over time

Changes in the genes of a population lead to changes in the phenotypes … this can lead to new species over time! The new species are descendants of the earlier ancestors just like you are descendants of your great great great great great great grandparents. You share a family history and share genes but you are not the same.

Theory of Evolution – KEY to Biology! Evolution = the CENTRAL DOGMA in biology It explains the patterns we see in living organisms

Let’s THINK… How does evolution work??

Genetic Variation 1.Genetic variation = diversity of alleles (genotype) 2.Leads to diversity in phenotypes

Genetic Variation 1.Genetic variation = diversity of alleles (genotype) 2.Leads to diversity in phenotypes 3.Variation allows some individuals to succeed during difficult times or environmental changes (better adapted!) 4.Allows the population to survive.

Environmental Changes Individuals better adapted for environmental change are more likely to survive and reproduce

Galapagos Islands tortoises  Shell structure varies depending on habitat. The Hood Island tortoise (left) has a longer neck and curved shell, which is better for reaching sparse vegetation. The Isabella Island tortoise (right) has a dome- shaped shell and shorter neck, which is better for the abundant, close vegetation.

So… What do we call this genetic variation within a population??

Gene Pool 1.All the genes in a population 2.Gene combinations change over time due to forces of evolution We will talk about these tomorrow! 3.Variation in the gene pool allows for evolution!

Gene Pool

Genetic variation in the gene pool allows for the population to change over time (evolution)… Which leads to…

Descent with Modification Organisms evolve from common ancestors with changes in genotypes and phenotypes Common Ancestor = Species that other organisms/species have evolved from Over time, enough changes can occur in a population to have a new species, descended from the original ancestor.

What ultimately allows for evolution to occur from a common ancestor to descended species?

All share a common ancestor… Evident in the DNA and anatomy!

MANY early scientists and naturalists set the foundation for our current understanding of evolution.. However, one naturalist in particular is credited as the “Father of the Theory of Evolution”…

Charles Darwin 1.Father of the theory of evolution 2.Observations lead to theories about how life changes over time 3.Darwin noticed that: - There are patterns of diversity in natural world - Living organisms resemble fossils

Darwin’s Finches of the Galapagos Islands