ANTHONY ROHM

EVIDENCE OF EVOLUTION

FossilsEarly developmentBody structures DNA Sequences

1) Evidence that evolution has occurred

Fossils show that living things from the past were very different from the living things of today.

Fossils give clues to how different species are related.

DNA in preserved fossils

Fossils as evidence

2 Fishes, amphibians, reptiles, birds, and mammals, for example, all have a similar body structure—an internal skeleton with a backbone.

3 How bones are arranged in the body also gives clues to evolution.

4 This shows that the animals evolved from a common ancestor.

Body structures as Evidence

5. Homologous Body Structures

Evidence for Evolution:Structural Similarities

6. Patterns of early development can show that animals are related.

7. These animals share a common ancestor that evolved over time into different species.

Early Development as Evidence

Gill pouch

Tail

Chick Human

Evidence for Evolution: Developmental Similarities

Homology: similarities caused by common descent

Scientists study what organisms look like when they are just beginning to develop. For example, the early stages of all animals with backbones all look similar.

8. DNA sequences and proteins give clues to how different species are related.

9. The DNA from fossils is providing scientists with new evidence about evolution.

10. The more alike DNA and protein structures are, the more closely related the species are.

DNA as Evidence

11 Because of its appearance, the tiny elephant shrew was thought to be closely related to mice and other rodents. However, DNA comparisons have shown that the elephant shrew is actually more closely related to elephants.

12 recent DNA comparisons show that dogs are more similar to wolves than they are to coyotes. Scientists had already reached this conclusion based on similarities in the structure and development of these three species.

Elephant Shrew and Elephant

evolution

Evidence

Fossil Record

Extinct Species

common ancestors

Living species

Time

Body StructuresDNA

EVOLUTION

The branching tree shows how scientists think raccoons, lesser pandas, giant pandas, and bears are related. Are bears more closely related to raccoons or giant pandas?

About how long ago did mosses first appear? F 100 million years ago G 150 million years ago H 350 million years agoJ 450 million years ago

Which group of plants would have DNA that is most similar to the DNA of flowering plants? A mosses B fernsC conifers D They would all be equally alike.

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

 Homologous Body Structures

1. What is this type of diagram called?2. What is the purpose of such a diagram?3. What types of evidence did scientists use to

make this diagram?4. Did amphibians evolve from reptiles? Give

evidence for your answer.5. What is the common ancestor of mammals

and turtles?6. Are birds more closely related to mammals

or to reptiles? Explain your answer.7. What could cause scientists to change the

information on this diagram in the future?

1. How many years does the table include, from the first species to the last?

2. Use Figure 16 in your textbook to determine in which era and period Hyracotherium lived.

3. When did Equus first evolve?4. How did scientists probably date these fossils

and the species they represent?5. From the fossil evidence shown, how did

forefeet change over time?6. From the fossil evidence shown, how did skulls

change over time?7. How might the environment in which each of

these species lived have affected the evolution of horses?

1. Using your ruler, draw a line 24 cm in length on a sheet of paper. Make a mark at the halfway point (12 cm).

2. Then, divide this 12-cm segment in half, making a mark at 6 cm. Continue in this way, dividing each progressively smaller segment in half (ignoring all of the other segments) until it becomes too small to accurately measure.

3. Now count each progressively smaller half-segment. How many segments did you count?

Section 17-1

Interest Grabber continued

a. Fossils show that living things are the same as they were in the past.

b. Animals that develop with the same patterns share a common ancestor.

c. Animals with body structures that look alike have different ancestors.

Evidence for evolution

After studying DNA and protein structuresFossilsEarly developmentBody structures

HOW DO SCIENTISTS KNOW SPECIES RELATED?

Concept Map

includes

Evidence of Evolution

Physical remains of organisms

Similar Genes Similar genes Similar genes

which is composed of which indicates which implies which implies

The fossil record

DNASequences

Homologous body

structures

Similaritiesin early

development