History of Life

History of Life

Additional Focus Area

How does a fossil's placement in rock layers show how life has varied and changed over Earth's history?

• New rock layers are deposited on top of older ones

  • The oldest fossils are located at the bottom (layer C)

• These show how organisms have changed over time

• useful for dating and correlating fossils based on specific characteristics

• must be distinctive or easily recognizable, abundant (widespread on Earth)

• often lived briefly and went extinct

Index Fossil

• Reveals a limited history of life on Earth based on the fossils that have been collected.

Fossil Records

Fossil basics

Why are fossils rare?

​Fossils are rare because their formation and discovery depend on chains of ecological and geological events that occur over deep time. Only a small fraction of the primates that have ever lived has been preserved as fossils.

​Very specific conditions are needed for a fossil to form!

Multiple Choice

Why are the oldest fossils found deeper underground?

• Less advanced organisms lived deeper underground.

• Deeper rock layers are less suitable for fossilization.

• Fossils move downward as rock layers shift.

• New rock layers are deposited on top of older ones.

Multiple Choice

Fossils are...

• always the skeletons of bones of organisms

• rare because fossilizing conditions are uncommon

• created after every animal and plant does and decomposes

• evidence of every organism that has ever lived on Earth

Multiple Choice

Which statement about fossils is FALSE?

• Fossils can be preserved remains or trace fossils such as footprints

• The fossil record is the sum total of what scientists know about fossils

• Fossils are commonly found because every animal does and leaves a fossil

• It is rare to find a fossils because very specific conditions are needed for a fossil to form

Multiple Choice

The fossil record reveals...

• a limited history of life on Earth based on the fossils that have been collected

• the complete history of animal and plant life on Earth

• that all animal and plant life on Earth will eventually become fossils

• that every organism that has ever lived on Earth is still alive today

Multiple Choice

Why do scientists find different fossils in different rock layers?

• Different organisms lived at different depths underground

• Rocks change shape after they form

• Organisms have changed over time

• Different scientists are doing the digging

Multiple Choice

Which statement most accurately describe the fossil record?

• The fossil record allows scientists to learn information about the history of life on Earth

• The fossil record only contains fossils consisting of animal and plant remains

• The fossil record contains fossils from every organism that has ever lived on Earth

• The fossil record provides information about organisms but not about their environment

What scientific techniques are used to determine the age of a fossil?

*Relative dating

• compares fossils to other fossils in rock layers

• where the fossil is locatd related to other fossils in the same area

• measures the amount of Carbon 14 in the fossil.

• Carbon 14 has always been present in living organisms in specific amounts

• This determines ACTUAL age

Radioactive dating

What scientific techniques are used to determine the age of a fossil?

Multiple Choice

In radioactive dating, scientists determine the age of a fossil by...

• measuring the amount of carbon-14 in the fossil

• measuring the weight of the fossil

• comparing the fossil to other fossils found in the area

• comparing the fossil to currently living species

Multiple Choice

When scientists do not know the actual age of a fossil but want to compare its age to another fossil, they use

• radioactive dating

• relative dating

• record dating

• absolute dating

Multiple Choice

According to relative dating, where are the youngest fossils located?

• At the top layer

• At the bottom layer

• In the middle layer

• It depends on the geographic location of the fossil find

Multiple Choice

In relative dating, scientists determine the age of a fossil by...

• Measuring the half-life of the fossil

• Measuring the amount of Carbon-14 in the fossil

• Comparing the fossil's carbon to other carbon sources in the area

• Comparing the fossil to other fossils found in rock layers in the same area

How does comparing the bodies of ancient and modern organisms show how life has changed over time and how different species are related?

• Compare their structures; they will have similar structures and anatomical traits

• For example: birds are closely related to dinosaurs (they share a common ancestor)

​

​To tell if species are closely related...

Multiple Choice

By comparing the wing of a monarch butterfly with the fossilized wing of an extinct dodo bird, a scientist determines that they have completely different structures. Which conclusion might the scientist draw from these observations?

• Both animals are of the same species

• The two species' wings are homologous (same).

• Birds evolved from butterflies

• The two species are not closely related

Multiple Choice

By comparing the fossilized wing of an extinct bird with the arm of a modern reptile, a scientist determines that the bones of both structures are very similar. Which concluson might the scientist draw from these observations?

• The two species have a common ancestor.

• There are no major differences between birds and reptiles.

• Both animals are of the same species.

• The two species are able to reproduce with each other.

Multiple Choice

A scientist is comparing the bone structures of a hippo, a pig and a whale. What evolutionary information might the scientist discover by comparing the anatomical structures of these living animals?

• Evidence that the animals share a common ancestor

• How the predator-prey relationships of the animals changed over time

• Why the animals have the same structures that perform the same functions

• Evidence that the animals share a similar diet

How does comparing embryos of different species show how they are related?

Emryos show a history of life...

• if they are similar in appearance, they show common ancestors

• if they show developmental similarities that show common ancestors

There are shared features in embryos that are NOT in adult organisms

• Embryonic stages my be similar

• For example, humans have gills during the embryonic stages that link them with other organisms

• Related organisms may undergo similar embryonic stages even if their adult forms are different

Multiple Choice

Why do scientists examine embryos to investigate the history of life?

• Scientists use embryos to identify differences in the genetic structures of different organisms

• Scientists use embryos to determine how humans are related to chimpanzees

• Comparing embryos of different species reveals differences in their bone structures and how those structures relate to different functions

• Comparing embryos of different species reveals developmental similarities that support the idea that all living things share a common ancestor

Multiple Choice

The embryos of fish, chickens, and humans all go through a phase in which they have gill-like slits in their necks. These gill slits do not function as gills in the embryo. In fish, they develop into adult gill slits. In chickens and humans, they dissappear as the embryo continues developing. What does this suggest about the history of life?

• Fish, chickens and humans all share a common ancestor

• Different forms of life evolved separately throughout Earth's history

• Embryonic chickens and humans developed gills in order to breathe

• Adult chickens and humans used to have functioning gills

Multiple Choice

The notochord is an embryotic structure in humans that develops into the spinal cord in the adult. What does the notochor suggest about humans' relatedness to other species?

• Humans are related to other species that possess spinal cords as ADULTS

• Humans are related to other species that possess notochords as EMBRYOS

• Humans are related to other species that possess notochords as ADULTS

• Humans are related to other species that possess spinal cords as EMBRYOS