What is meant by evolution?

• a gradual change in species over time

• source of all biological diversity

• the process by which modern organisms have descended from ancient organisms

• the biological process that links all species, no matter how they differ

Compare and contrast…

• The organism in (a) died more than 150 million years ago, and its remains were preserved in a rock. What does it look like to you?

• The organism in (b) is a modern bird, the anhinga. How do you know it is a bird? How does it resemble the organism in (a)? How does it differ?

Organisn (a) is called Archaeopteryx

• oldest bird known from the fossil record.

• shares two characteristics with modern birds: feathers and a wishbone

• could not fly, fossil records indicate it lacked a breastbone

• has many reptilelike characteristics: teeth, claws on its wings, a bony tail

Charles Darwin

Darwin’s Route During the Five-year Voyage

Summary of Darwin’s Theory1. Individual organisms in nature differ from

one another. Some of this variation is inherited.

What type of variations can you see?

2. Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce.

3. Because many organisms are produced that can survive, members of each species must compete for limited resources.

4. Because each organism is unique, each has a different advantages and disadvantages in

the struggle for existence.

The lichen katydid is hidden from predators because it

resembles the lichen on which it feeds.

Mimicry

5. Individuals best suited for the environment survive and reproduce more successfully. The characteristics that make them best suited to their environment are passed on to offspring.

Individuals whose characteristics are not as well suited to the environment die or leave fewer offspring.

6. Species change over time. Over long periods, natural selection causes changes in

the characteristics of species, such as in size and form.

Light moth versus dark moth

7. Species alive today have descended with modifications from species that lived in the past.

glyptodon armadillo

8. All organisms on Earth are united into a single tree of life by common descent.

chicken turtle rat

Embryonic development of some vertebrates

Do and discover…

Examples from the fossil record

Evolution modeled as the growth of a bush

How much have you learned?

1. Evolution is the process of the

A. development of one-celled organisms

from mammals

B. change in species over long periods of

time

C. embryonic development of modern humans

D. changing energy flow in food webs

2. Which phrase best defines evolution?

A. an adaptation of an organism to its environment

B. a sudden replacement of one community by

another

C. the isolation of organisms from each other for

many years

D. a process of change in species over a period of

time

3. Evolution is often represented as a branching tree similar to the one shown in the diagram below. The names shown represent different groups of organisms alive today; the lines represent their evolutionary histories.

The statement that is best supported by the diagram is that

A. Annelida and Arthropoda have an ancestor in common

B. Echinodermata are more closely related to Mollusca than they

are to Chordata

C. Mollusca and Arthropoda probably evolved before Porifera

D. Annelida and Arthropoda evolved from Echinoderma

4. The study of fossils has allowed scientists toA. describe past environment and the history of

lifeB. study present ocean temperatures at different

depthsC. analyze the chemical composition of

sedimentary rocks and mineralsD. describe the details of the process by which life

began on Earth

5. The following diagram represents possible lines of the evolution of primates.

Which inference can best be made on the diagram?A. Adaptations for living in trees are inherited by all primates.B. Humans and apes have a common ancestor.C. The embryos of monkeys and apes are identicalD. The period of development is similar in most primates.