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CHAPTER 6 STUDY GUIDE– EARTH’S HISTORY
Lesson 1
1. What are the five types of fossils? Give a definition of how each can form.
A. Fossils found in rock include petrified fossils, molds and cast, carbon films, and trace fossils
1. Petrified Fossils- are fossils in which minerals replace all or part of an organism
2. Molds and Cast are the most common fossils
a. Molds- is a hollow area in sediment in the shape of an organism or part of an organism
(hard part of the organism)
b. Cast- is a copy of the shape of an organism
3. Carbon Films- an extremely thin coating of carbon on a rock
4. Trace Films – a type of fossil that provides evidence of the activities of ancient organisms
(footprints, trails, or burrows)
5. Other fossils form when remains of organisms are preserved in substances such as tar,
amber, or ice
a. Tar- a stick oil that seeps from the Earth’s surface
i. Amber- is hardened resin, or sap of evergreen trees
ii. Freezing- preserved even hair and skin
2. How do fossils provide evidence of the past?
- All of the fossils that scientist have collected
- A record of species that have lived on the planet
3. Explain why most plants and animals do not become fossils.
- Fossils only form under the correct conditions
- Even if a fossil is formed, it is susceptible to environmental conditions such as weathering and
erosion, heat and pressure, changing rock types and animal/insect interference
4. Explain the similarities and differences between permineralization and replacement. How are these
similar of different from petrified fossils?
- Petrified Fossil- A fossil in which minerals replace all or part of an organism
- Permineralization- water from the ground seeps into tiny empty spaces and deposits minerals
- Replacement- the hard structures of organisms dissolved and are replaced with minerals
Lesson 2
1. What is a homologous structure?
- Body parts that are structurally similar in related species
- Provide evidence that the structures were inherited from a common ancestor
2. Besides fossils, what other evidence do scientists use to show evolutionary relationships? Briefly
describe each of these things.
A. Similarities in Body Structure
1. Homologous structures
B. Similarities in Early Development
C. Similarities in DNA
1. Proteins
2. Amino acid sequence
3. Why do scientists think the ancestors of whales used to walk on land?
- Biologists believe that for 100 million years the only vertebrates on Earth were water-dwelling
creatures, with no arms or legs.
- At some point these "fish" began to develop hips and legs and eventually were able to walk out
of the water, giving the earth its first land lovers.
- Once the land-dwelling creatures evolved, there were some mammals that moved back into the
water.
- Biologists estimate that this happened about 50 million years ago, and that this mammal was
the ancestor of the modern whale.
- Despite the apparent uselessness, evolution left traces of hind legs behind, and these vestigial
limbs can still be seen in the modern whale.
- There are many cases where whales have been found with rudimentary hind limbs in the wild,
and have been found in baleen whales, humpback whales, and in many specimens of sperm
whales.
- Most of these examples are of whales that had only leg bones, but there were some that
included feet with complete digits.
- It was reported recently that whales and hippos were distantly related.
Lesson 4
1. Why do scientist classify?
Biologist use classification to organize living things into groups so that the organisms are easier
to study
2. What is binomial nomenclature? Why is the use of two names important? Who is the scientist that
first used binomial nomenclature?
Binomial nomenclature- the naming system in which each organism is given a two-part name- a
genus name and a species name. Written in Latin, this system allows scientist all over the world
to use the same name. Swedish scientist named Carolus Linnaeus expanded on Aristotle’s ideas
and created the system called binomial nomenclature.
3. What are the seven levels of classification? Which is the largest, which is the smallest?
Kingdom (largest), phylum, class, order, family, genus, species (smallest)
4. What are four ways that help scientist classify today? (See page 225)
Species with similar evolutionary histories are classified more closely together. Scientist use
knowledge of body structures as well as chemical make-up of fossils to each other and to
modern organisms. Homologous structures, DNA, amino acid sequences, and similarities in early
development.
5. What is a Taxonomic Key or Classification Key? Why are they important to scientist?
Taxonomic Key- is a series of paired statements that describe the physical characteristics of
different organisms. These are “yes” or “no” questions that eventually lead completely
identifying a species. Taxonomic keys are factual representations of the physical
characteristics of a species that allow for easy identification and limit confusion between
scientists all over the world.