Ms. McInnis Evolution 7th Grade Science

Evolution Evolution : changes in form and function over generations Small scale: changes in genetics from generation to generation Large scale: the descent of different species from a common ancestor over many generations

Evolution Basic Idea- All living things on earth have a common ancestor These changes can are documented by the fossil record

Fossil Record The fossil record lets us look at life from the past The fossil record dates back to 4 Billion year ago!

Early Fossil Record Nicholas Steno- saw similarities between Shark teeth and rocks that were called “tongue stones” These “tongue stones” were actually fossilized shark teeth Mary Ann Mantell- found a large tooth (which she thought was a large iguana’s) and it was a dinosaur tooth! This discovery led scientists to understand that fossils are a way to study extinct organisms!

Transitional Forms of Fossils Transitional Fossils : the intermediate fossil stage between the ancestor and the modern day organism

Transitional Fossils Example The Pakicetus is an early ancestor to modern whales, this organism was a land mammal The Pakicetus had nostrils on the front of its skull Today, Gray whales have nostrils on the top of their skull The transitional fossil would be the Aetiocetus

Homologies The theory of evolution states that organisms share similarities that come from a common ancestor Homologies: similar characteristics due to relatedness Ex] Leaves: leaves come in very different structures and have different functions, but common ancestors had leaves

Ex] Forelimb of vertebrates with legs: frogs, birds, rabbits, and lizards all have forelimbs that look different and have different functions BUT all of the organisms above have a radius bone, ulna bone, and humerus bones in their forearm which was found in the common ancestor