Day 2 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 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 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.