Objective: Explain how biological evolution is the consequence of the interactions of genetic variation, reproduction and inheritance, and natural selection and time.

Agenda:1. Origin of Life 2. Earth History

Day 2

Warm Up:On a piece of white paper, draw a circle that is exactly 6 inches in diameter

Note: Not to scale

Earth History• First evidence of life 4 BYA• Oxygen first appeared in the atmosphere 2 BYA• First multicellular life 1 BYA• Snowball Earth 700 MYA• First Animals 700 MYA• Colonization of Land 450 MYA• The Great Dying 250 MYA• Extinction of the Dinosaurs 65 MYA• Mammals Take Over 60 MYA• Humans Ancestors 1 MYA• Human Civilization 10,000 years• Global Pollution Crisis Present

1 billion years= 5.5 hours200 million years= 1 hour100 million years= ½ hour

Formation of Earth• Earth born through a series of collisions over the course of 100 million years • Early Earth was molten rock. Over time the most dense elements formed the planet’s core while the

moderately dense became the crust and lightest the early atmosphere. • Over millions of years the surface cooled enough to let water remain liquid form.• During this time there was still no oxygen in the atmosphere.

During the formation of Earth__________________But ______________________________________So _______________________________________Then _____________________________________

The First Organic Molecules

Mixture of gases simulatingatmosphere of early Earth

Spark simulatinglightning storms

Liquids containing amino acids

Free Oxygen

– Earliest life-forms evolved without oxygen– About 2.2 billion years ago, photosynthetic bacteria

began to release oxygen into the atmosphere.– The increase in oxygen caused some life forms to go

extinct while others were able to adapt and use the oxygen using respiration. Note the importance of genetic diversity.

Endosymbiotic theory

Sexual vs. Asexual•Populations of organisms that reproduce through asexual reproduction can grow quickly. However, because they rely on mutations for genetic variation, every member of the species has similar vulnerabilities.

•Organisms that reproduce sexually produce fewer offspring, but the recombination during sex gives them a large amount of variation. This allows some individuals to be less susceptible to catastrophic disease.