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Day 2
Objective: Explain how biological evolution is the consequence of the interactions of
genetic variation, reproduction and inheritance, and natural selection and time.
1. Origin of Life
2. Earth History
Warm Up:
On a piece of white paper, draw a circle that is
exactly 6 inches in diameter
Not to scale
Earth History
First evidence of life
Oxygen first appeared in the atmosphere
First multicellular life
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
Human Civilization
10,000 years
Global Pollution Crisis
1 billion years= 5.5 hours
200 million years= 1 hour
100 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
Spark simulating
lightning storms
Mixture of gases simulating
atmosphere of early Earth
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.