Chapter 4 Change Over Time
Lesson 1: What do Fossils Reveal?
Paleontologists are scientists who study what
life on Earth was like in the past.
Fossils are the preserved remains or traces of an
organism that lived in the distant past.
Fossils can be the remains of a dead organism
Fossils are trace fossils when evidence of an
organism is found preserved, not its remains
Trace fossils include imprint fossils, such as a
footprints
Hardened tree sap becomes amber and can
preserve whole organisms
What do fossils reveal?
Fossils provide a record of Earth’s living things
Fossils also provide evidence for how living
things have changed
Fossils allow scientists to learn about
individual organisms and species
Geologic time scale presents the history of the
Earth in a time line.
Extinction is the death of all the member of a
species.
Mass extinction is the extinction of a huge
number of species at about the same time.
Paleontology is the study of ancient life.
Lesson 2: Natural Selection
Selective breeding is the practice of choosing
organisms, plants or animals, with desirable traits
to reproduce.
For example: Border collie herding dogs; wheat
plants that produce more grain.
Natural selection is the process by which the
organisms best adapted to their environments
survive and reproduce.
For example: the bacteria that can resist
antibacterial soap will survive and reproduce.
Who was Charles Darwin?
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He was an English naturalist who first developed
the idea of natural selection.
He published his ideas and evidence in a book
called, On the Origin of Species, in 1859.
He concluded that the species he observed had
changed over many generations, and in doing
so, they became better adapted to their
environments.
His ideas are still the subject of debate today.
Homologous structures are structures that are
similar in different species.
It supports the theory of evolution; even
though the structures look different, they are
organized in the body the same way.
It also suggests that species have common
ancestors.
Homologous structures help scientists learn
how similar structures can be adapted for
different uses.
For example: the dolphin’s arm was adapted
for swimming and life in the water after it
lived on land first.
There is DNA evidence that supports the theory
that species may have all come from one
common ancestor.
Organisms are still evolving today. For example,
bacteria are evolving to resist soaps and
antibiotics.
1. Carefully examine the sketches of the animal forelimbs
above.
2. Discuss with a partner how they are alike and write your
answer in your notebook.
3. Discuss how they are different and write your answer in
your notebook.
4. Discuss how each animal uses its forelimb.
5. Circle bones that are similar.