According to the image, which rock layer is the oldest?
Layer A
How can radioactive dating help us date fossils?
Igneous rock layers can give exact ages and we can use them to estimate the age range of fossils found between them.
In a rock layer, where are the younger organisms found?
Closer to the surface.
Describe what can cause a gap in the fossil record.
Possible answers: Erosion prevents sediment from covering an organism, erosion destroys existing fossils
Would a glacier make a good environment for forming fossils? Why or why not?
It would be a poor environment because the frozen water prevents sediment from moving and there are not many living things.
Why are fossils rarely found in metamorphic and igneous rocks?
The heat needed to create the rocks usually destroys the organism before it can become a fossil.
In what type of rock are fossils most commonly found?
Sedimentary
Describe the steps needed to create a fossil.
1. An organism dies. 2. The organism is covered by sediment. 3. Pressure builds. 4. Water and minerals replace the organism.
What is a gap in the fossil record?
It is a time period when no fossils formed.
What does relative dating tell us about fossils?
It tells which fossils are younger or older.
Between 275 and 70 mya, the majority of fossils found are of dinosaurs. What can scientists conclude about the dinosaur population at the time?
Dinosaurs were the dominant animal alive during that time.
What is a fossil record?
It is the layers of rock and the fossils preserved in them.
Name two traits that make for a GOOD environment for forming fossils.
Possible answers: mud or wet sediment, water to move sediment, pressure can build up, organisms live in the area, no erosion
Can animal footprints become fossils?
Yes! Since footprints are the traces of a living thing, they can be fossilized.
The earliest multicell organism fossils are of marine animals. What can scientists conclude about Earth at this time?
The Earth was primarily covered with water.
Rock layers are called __________________.
Strata
True or False: Items that indicate human life (like phones and pencils) can become fossils.
False! These items are not living or made directly by a living organism (like a footprint), so they can't become fossils.
Radioactive dating can be used on which rock type(s)?
ONLY igneous rocks!
Ancient dragon flies are much larger than modern day dragon flies. What can scientists conclude about Earth's atmosphere in the past?
There was more oxygen in the air, which allowed the dragon flies to grow larger.
When using indirect evidence, can scientists know for sure what happened in the past?
They can't! Indirect evidence only allows them to make an educated guess.