Chapter 7 Section 1

Identify 2 kinds of evidence that show that organisms have evolved.

Describe one pathway through which a modern whale could have evolved from an ancient mammal.

Explain how comparing organisms can provide evidence that they have ancestors in common.

Respond to this prompt:

The cockroach originated on Earth more than 250 million years ago and is thriving today all over the world. A giant deer (more than 2 m tall!) evolved less than 1 million years ago and became extinct around 11,000 years ago.

Why do you think one animal thrived and the other perished?

Vocabulary: Adaptation:

◦ An adaptation that helps an organism survive and reproduce in its environment

Species:◦ A group of organisms that can mate with one

another to produce fertile offspring Evolution:

◦ The process in which populations gradually change over time; inherited characteristics within a population change over generations – new species sometimes arise

Text page 166; figures 1,2,3

Compare the frogs.

Discuss the unique adaptations of each◦ If you see a frog that looks like one of these frogs,

can you assume that they are both the same species?

◦ How can you tell?

Vocabulary:

Fossils:◦ The remains or imprints of once-living organisms

found in layers of rock◦ most commonly preserved in sedimentary rock

Fossil record:◦ A historical sequence of life indicated by fossils

found in layers of the Earth’s crust◦ organized by estimated ages and physical

similarities

Fossil record provides evidence about the order in which species existed

Scientists think that all living species descended from common ancestors

Ex: whales and hoofed animals pg. 169, figure 6◦ “tree of life”◦ gaps in fossil record

Case study: Evolution of the Whale◦ Whales are mammals (breathe air, give birth to

live young, produce milk)◦ Seem similar to fish

◦ Ancient ancestor: four-legged land mammal

◦ Fossil evidence (pg. 170-171) Pakicetus, Ambulocetus, Dorudon, Modern toothed

whale

◦ Walking whales: shared traits, hip bones…

Comparing Skeletal Structures◦ Compare: your arm, wing of a bat, leg of a cat,

flipper of a dolphin◦ Similar structure and order of bones◦ Common ancestor

Comparing DNA◦ The greater the similarities in DNA for two sets of

species, the more closely related through a common ancestor

◦ All existing species have DNA

Use the words adaptations, population, and evolution in a sentence.

Why are scientists unsure about some parts of the “tree of life” on Earth?