This document outlines major events in the evolution of life on Earth over the past 4.6 billion years, including the following key points: - 3.5 billion years ago, unicellular life evolved and photosynthetic bacteria began releasing oxygen into the atmosphere. - Around 500 million years ago, fish-like vertebrates evolved and invertebrates like trilobites were common in the oceans. - By 360 million years ago, four-limbed vertebrates moved onto land and seed plants and large forests appeared. - The mass extinction event around 248 million years ago led to the demise of over 90% of marine life and 70% of terrestrial life.

1. Evolution

2. History
4.6 billion Years Ago
The Earth forms and is bombarded by meteorites and
comets.

3. 3.5 billion Years Ago
Unicellular life evolves. Photosynthetic bacteria
begin to release oxygen into the atmosphere.

4. 555 million Years Ago
Multi-cellular marine organisms are common. The
diverse assortment of life includes bizarre-looking
animals like Wiwaxia.

5. 500 million Years Ago
Fish-like vertebrates evolve. Invertebrates, such as
trilobites, crinoids, brachiopids, and cephalopods,
are common in the oceans.

6. 450 million Years Ago
Arthropods move onto the land. Their descendants
evolve into scorpions, spiders, mites, and
millipedes.

7. 400 million Years Ago
http://www.youtube.com/watch?v=mneDhOtVEQw&feature=you
Megaladon Pre-historic Shark

8. 360 million Years Ago
Four-limbed vertebrates move onto the land, and
seed plants and large forests appear. The Earth's
oceans support vast reef systems.

9. 250 million Years Ago
The supercontinent called Pangea forms. Conifer-like
forests, reptiles, and synapsids (the ancestors of
mammals) are common.

10. 248 million Years Ago
Over 90% of marine life and 70% of terrestrial life
go extinct during the Earth's largest mass
extinction. Ammonites are among the survivors.

11. 225 million Years Ago
Dinosaurs and mammals evolve. Pangea has begun
to break apart.

12. 130 million Years Ago
As the continents drift toward their present positions,
the earliest flowers evolve, and dinosaurs dominate the
landscape. In the sea, bony fish diversify.

13. 65 million Years Ago
A massive asteroid hits the Yucatan Peninsula, and
ammonites and non-avian dinosaurs go extinct.
Birds and mammals are among the survivors.

14. 4 million Years Ago
In Africa, an early hominid, affectionately named
"Lucy" by scientists, lives (in Ethiopia). The ice ages
begin, and many large mammals go extinct.

15. 130 000 Years Ago
Anatomically modern humans evolve. Seventy thousand
years later, their descendents create cave paintings —
early expressions of consciousness.

16. EVOLUTION (Think/Pair/Share)

17. EVOLUTION (Think/Pair/Share)
Biological evolution is descent with modification.
This encompasses small-scale evolution
(changes in gene frequency in a population
from one generation to the next) and large-
scale evolution (the descent of different
species from a common ancestor over many
generations).
Evolution helps us to understand the history of
life.

18. The Theory of Evolution
What is a theory? (Think/Pair/Share)
(Hint! Think of atomic or cell theories... Or
the theory of relativity.)

19. Everyday: An educated guess
Scientific: An explanatory model that accounts for a
body of facts that have been repeatedly confirmed.
Theories provide a basis for explaining observations
of the natural world and for making predictions.
Scientific theories are confirmed explanations of
nature and are the most reliable, rigorous, and
comprehensive form of scientific knowledge.