{Section 5.1

Change Over Time

Adaptation: A characteristic 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.

Fossils: The remains of imprints of once-living organisms, sometimes found in layers of rock.

Fossil Record: A timeline of life that is known as indicated by fossils found in the Earth’s crust.

Vocabulary

After reviewing the vocabulary terms for this section, what are some things you already know about this section?

Are there any topics of interest or things you remember from other classes?

What do you already know?

Different organisms have different characteristics, or adaptations, that allow them to survive in their habitat (find food, protect itself, and reproduce).

Living things with similar characteristics may be members of the same species.

There are many species of organisms on Earth today, but have they always existed? What existed before now that no longer exists? What will exist in the future?

Scientists have evidence that Earth and the species on Earth have change a great deal, or evolved, over time.

Differences Among Organisms . . .

Scientists estimate that the planet is over 4.6 billion years old . . . Have the species that exists today always been here? Explain your thoughts . . .

Evidence of changes in species over time can be found in fossils found deep within the Earth’s surface.

By studying fossils, scientists are able to create a timeline of life (known as the fossil record). Fossils found deeper in the Earth’s surface are not quite as similar to modern day organisms as newer fossils.

Evidence of Changes Over Time . . .

The fossil record provides evidence about the order in which species have existed.

Scientists observe that all living organisms have characteristics in common and inherit characteristics in similar ways . . . So, scientists believe that living species descended from common ancestors.

Scientists examine fossil records to figure out the relationship between extinct and living organisms.

EXAMPLE: Scientists believe that whales and some types of hoofed mammals have a common ancestor.

Scientists use this evidence to sketch out a “tree of life” that includes all known organisms. Evidence of

Ancestry . . .

Case Study: Evolution of the Whale Scientists believe that the ancient

ancestor of whales was probably a mammal that spent time on land and in water.

Scientists have studied the characteristics of ancient four-legged mammals and, though modern day whales do not have hind limbs, they have tiny internal hip bones. This evidence supports that whales may have an ancient land dwelling ancestor. (see p. 112-113 in your text)

Examining Organisms . . .

Scientists can study and compare organisms’ DNA to determine how traits have changed over time.

HYPOTHESIS: If species that have similar traits evolved from a common ancestor, the species will have similar genetic information.

Scientists also study skeletal structures of organisms and compare them.

If you look at the skeletal structure of a dolphin flipper, bat wing, human arm, and cat leg, you can see how there are similarities.

Scientists believe that skeletons of organisms changed over time to perform different functions. Comparing

Organisms . . .

http://www.youtube.com/watch?v=9R8hpPY_9kY&list=PL6090C98C77B3C295

Tree of life . . .

http://www.pbs.org/wgbh/evolution/educators/lessons/lesson3/act2.html

Small Group Activity . . .