Geologic Time Scale
The Geologic Time Scale is divided into _________ categories.
4
This is how long ago humans appeared.
2 million years ago
Which word means gone forever?
Extinct
One ring represents____________.
one year of growth
What is an unborn baby called up until 8 weeks of development?
Embryo
What is the largest unit of geologic time called?
Eon
This is how long ago dinosaurs appeared.
225 million years ago
What does the word preserve mean?
To save
Dark tree rings represent growth during which season?
Summer
True or false: We have the same bones in our forelimb as a whale.
True
What is the smallest unit of geologic time called?
Epoch
This is how long ago cyanobacteria appeared.
2.5 billion years ago
What do scientists believe is the reason as to why dinosaurs went extinct?
Asteroid impact
A wide tree ring represents what?
Good growth, warm and wet.
True or false: Human embryos have a tail, and gills.
True
What is the current Era called?
Cenozoic
This is how long ago anaerobic microbes appeared.
3.8 billion years ago
Index fossils help scientists date the age of unknown fossils. Index fossils need to be widely distributed and ______________.
Live for a short period of time
What is the center of a tree called?
Pith
If two embryos are very common, what does this indicate?
The two species have a common ancestor.
What is the Geologic Time Scale divided up based on?
Fossil evidence
What happened to anaerobic microbes when cyanobacteria appeared?
The microbes died in the presence of oxygen because they didn't need oxygen.
What is the half life of Carbon-14?
5,730 years
What is one limitation to a tree's growth besides being cold and dry?
Poor soil, little sunlight, too close to other trees
Why are the metacarpals in a bat spread out and thin?
For flying