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?