The Geological Timescale Flashcards
How do geologists divide the history of the earth?
Into geological time units
What is the purpose of a geological timescale?
To represent a timeline of life on earth, from the origin of the earth
How are time units characterised?
By the specific group of fossils found relating to that time unit
What is an aeon?
The largest unit of time
What is an era?
The three time units that an aeon is divided into
What are the three eras?
Plaeozoic
Mesozoic
Cenozoic
What are periods?
The further units of time that eras are divided into
What period precedes the palaeozoic era?
The Precambrian period
What does the geological timescale show us?
That life on earth was initially simple and became more complex
What is a fossil record?
A list of all of the fossils of different ages that have been discovered by palaeontologists
Why is a fossil record incomplete?
Not all fossils have been found
Not all organisms become fossils
Where do the gaps in fossil records occur?
Where one kind of organism evolved into another
Which fossils are the rarest?
Fossils of transitional forms
What is the archaeopteryx?
It is the most primitive bird known
What is important about the archaeopteryx?
It is the missing link between birds and reptiles
