Fossil Evidence Of Change

Fossil Record

• A fossil is any preserved evidence of an organism.

• Plants, animals and bacteria can form fossils

• About 99% of species that ever existed are now extinct, but only a tiny percentage are preserved as fossils

Thinking Time!!!

• Why do you think only a small percentage of organisms are preserved as fossils?

Relative Dating• Relative dating is

a method used to determine the age of rocks by comparing them with those in other layers

Where in the picture do you think a terrestrial ecosystem replaced an aquatic one?

How evolution takes place• Punctuated Equilibrium- Suggests

that species evolve very rapidly and then stay the same for a large period of time

• Gradualism- Suggests that organisms evolve through a process of slow and constant change

Speciation• Cannot accurately determine when one

species becomes another species.• Two hypotheses:

–Phyletic speciation- Suggests that abrupt mutations occur after a species has existed for a long period of time. Results in a shifting to new species.

–Divergent speciation- Suggests that a gradual accumulation of small changes that eventually turns into a new species.