Today’s Agenda…3/7

Bellringer: What causes variation among organisms? What will happen to helpful variations? What will happen to harmful variations? (answer all questions)

Notes on Fossils & Extinction Homework: Fossils and Extinction Questions Test corrections due by tomorrow!

What could have caused the two variations?

Mutations Different allele combinations

What will happen when it reproduces? Why?

The frog that survives will reproduce The offspring will have similar traits to the parents The frog will pass on the helpful trait

What will happen to each of the frogs? Why?

The frog that blends in with the environment will survive and reproduce

The frog that did NOT blend in the environment will not survive (it will be eaten by predators or unable to hide from prey)

What will happen to the population of frogs with each variation over time?

The population of the frog with the helpful variation will increase.

The population of the frog with the harmful variation will decrease.

How does this activity show natural selection?

Nature “selected” the frog with the camouflage to survive and reproduce

One frog was better suited to the environment than the other, so it will survive

The frog that is adapted to the environment will survive

One frog is a better fit for the environment so it will survive

How does natural selection lead to evolution?

Evolution is a gradual change in a species over time.

The species of frogs will change over time to include mostly frogs that are well suited to that environment.

The other frog may evolve in an environment it is better suited to

Looking Into the PastLooking Into the PastFossils & Extinction

Study Pack #5

Today’s Targets…

I understand what fossils and the fossil record are.

I can describe the usefulness of the fossil record.

I understand that fossils provide evidence of biological change.

Fossils

Fossils are traces of past organisms preserved in Earth’s crust

Can be actual structures or just imprints of structures

Fossils are normally found in sedimentary rockLayers of sand, silt, clay or mud are compacted and

cemented together with fossils inside

Types of Fossils Page 344 Figure 9 Cast fossils

Minerals fill in cracks to create a castExample: Animal tracks become filled in

Fossils in amber Sticky material from trees harden and trap insects

Imprint FossilsAn organism leaves an imprint on sediment that later hardens

to become rock

Types of Fossils

Mineralized fossilsMinerals replace wood or bonePetrified wood

Frozen fossils

Determining a Fossil’s Age

Relative DatingYounger rock layers are on top of older rock layersProvides an estimate of a fossil’s ageFossils found in lower layers of sedimentary rock are

older than those found in upper layersPage 345

Determining a Fossil’s Age

Determining a Fossil’s Age

Radiometric or absolute datingMore accurateUse the amount of radioactive elements in the rock

where the fossil is found to determine its age

The Fossil Record The fossil record provides us with clues that organisms

have changed over time Organisms have gone from simple to more complex It is incomplete Evidence of evolution

The Fossil Record

Fossils tell us:What organisms in the past looked like & whether they

are similar to those todayHow organisms changed over timeThe roles the organisms played within communities and

food chainsHow Earth’s climate has changed over timeHow Earth’s surface has changed over time

Extinction

Most of the organisms that have ever existed are extinct today

Once a species is extinct, it can never come back to life

Extinction

Natural causes – competition, predation, climate changes, natural disaster

Human activity – habitat destruction, overhunting

Review

In your own words, what is a fossil? In what kind of rock are fossils found? Why aren’t fossils found in igneous rocks? Why aren’t fossils found in metamorphic rocks? What are the different types of fossils? What parts of an organism are preserved as

fossils?

Review

Which provides a more exact age of a fossil: relative or absolute dating?

Which fossil is the oldest? Which fossil is the youngest?

Review

Does the fossil record show all organisms that lived in the past?

Are most of the species of organisms in the fossil record still alive today?

According to the fossil record, how have organisms changed over time?

What clues does the fossil record provide?

Review

What causes extinction? What is probably the greatest cause of extinction

today?