9. Changes in a species over time

Question 1

Define an index fossil

Answer 1

Geographically widely spread
Abundant
Easily identifiable
only existed for a short time span

Question 2

Where would the youngest rocks be found in a rock profile?

Answer 2

at the top

Question 3

Define a transition fossil

Answer 3

are intermediate between current and ancestral form.

Question 4

What is an absolute age

Answer 4

determines the age of rock around a fossil using radiometric dating giving it an actual number

Question 5

What is a relative age?

Answer 5

gives a relative order of events, does not predict actual age.

Question 6

What is the half life of Carbon 14?

Answer 6

5730 Years

Question 7

What is the maximum age you can use C14 for dating?

Answer 7

60,000 years

Question 8

What type of radiometric dating is used for rock millions of years old?

Answer 8

Uranium Lead or Potassium Argon

Question 9

What are the steps for a fossil forming in rock (this will need tweaking if it’s ice in the q)

Answer 9

A hard bodied organism is rapidly buried in sediment
Soft tissue decomposes.
Mineralisation occurs in the hard parts
Pressure turns sediment into rock

Question 10

What is a direct fossil?

Answer 10

Fossils where the entire organism or parts of the organism are preserved.

Question 11

What is a trace fossil?

Answer 11

Fossils showing the signs or remains of an organism?s activities e.g. footprints, bite marks.

Question 12

What has ocurred in the fossil record at the end of each period of geological time?

Answer 12

Mass extinction

Question 13

What is a fossil?

Answer 13

the remains or traces of pre-existing life forms preserved in rock, ice or amber

Question 14

Define divergent evolution

Answer 14

Divergent evolution is when species that share a recent common ancestor become more dissimilar over time. These species share homologous structures.

Question 15

Define homologous structures

Answer 15

Homologous structures have a similar structure but have different functions.

Question 16

Define convergent evolution

Answer 16

Convergent evolution is when species independently develop different structures that have a similar function.

Question 17

Define analogous structures

Answer 17

Have a similar function, but are not structurally the same.

Question 18

What is adaptive radiation?

Answer 18

Adaptive radiation is a form of divergent evolution where a number of different species form from a single recent common ancestor.

Question 19

What is the cause of divergent evolution?

Answer 19

This is due to experiencing different selective pressures.

Question 20

What is the cause of convergent evolution?

Answer 20

This is due to experiencing similar selection pressures.
The species do not share a recent common ancestor.

Question 21

What is a vestigial organ?

Answer 21

An organ or structure that is functionless in an organism - remnant feature from an ancestor.

Question 22

Allopatric speciation scaffold

Answer 22

Two populations of ______ are geographically isolated by a permanent geographical barrier of _______.
There is no gene flow.
There are different selection pressures acting on each population of ________.
Mutations accumulate over many generations in each population.
Eventually they can no longer interbreed to produce fertile and viable offspring and would be considered 2 separate species.

Question 23

Compare sympatric speciation with allopatric speciation

Answer 23

Sympatric speciation occurs in the same geographical area (e.g. Lord Howe Island) whereas allopatric speciation is in different geographical areas (e.g different Galapagos islands).
With sympatric speciation there is reproductive isolation first whereas allopatric speciation there is isolation by a permanent geographical barrier first.

Question 24

State the environmental Conditions for Fossilisation

Answer 24

The organism must have a hard body (as the soft tissue usually decomposes)
Hidden from scavengers and left undisturbed for a long time.
There is no oxygen present
Low temperature
High pressure

Question 25

Define half life

Answer 25

A half life is the time taken for a radioactive isotope to decay by half e.g. It takes 5730 years for Carbon 14 to decay into nitrogen 14.

Question 26

Describe stratigraphy

Answer 26

Stratigraphy is where we compare the position of fossils in rock strata to determine the relative order of age using the principle of superposition. This means that the oldest stratum is assumed to be at the bottom and the layers above become progressively younger /they are laid down in chronological order.