Changes in a species over time Flashcards
Define an index fossil
Geographically widely spread
Abundant
Easily identifiable
only existed for a short time span
Where would the youngest rocks be found in a rock profile?
at the top
Define a transition fossil
are intermediate between current and ancestral form.
What is an absolute age
determines the age of rock around a fossil using radiometric dating giving it an actual number
What is a relative age?
gives a relative order of events, does not predict actual age.
What is the half life of Carbon 14?
5730 Years
What is the maximum age you can use C14 for dating?
60,000 years
What type of radiometric dating is used for rock millions of years old?
Uranium Lead or Potassium Argon
What are the conditions required for fossilisation?
Hard parts that are rapidly covered in sediment
There is no oxygen present (decrease the rate of decomposition).
Low temperature (to also decrease the rate of decomposition)
Hidden from scavengers.
Left undisturbed for a long time.
What is a direct fossil?
Fossils where the entire organism or parts of the organism are preserved.
What is a trace fossil?
Fossils showing the signs or remains of an organism?s activities e.g. footprints, bite marks.
What has ocurred in the fossil record at the end of each period of geological time?
Mass extinction
What is a fossil?
the remains or traces of pre-existing life forms preserved in rock, ice or amber
Define biogeography
the distribution of plants and animals in a particular area.
Define divergent evolution
Divergent evolution is when species that share a recent common ancestor become more dissimilar over time. These species share homologous structures.
Define homologous structures
Homologous structures have a similar structure but have different functions.
Define convergent evolution
Convergent evolution is when species independently develop different structures that have a similar function.
Define analogous structures
Have a similar function, but are not structurally the same.
What is adaptive radiation?
Adaptive radiation is a form of divergent evolution where a number of different species form from a single recent common ancestor.
What is the cause of divergent evolution?
This is due to experiencing different selective pressures.
What is the cause of convergent evolution?
This is due to experiencing similar selection pressures.
The species do not share a recent common ancestor.
What is a vestigial organ?
An organ or structure that is functionless in an organism - remnant feature from an ancestor.
Allopatric speciation scaffold
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.
Compare sympatric speciation with allopatric speciation
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 whereas allopatric speciation there is isolation by a permanent geographical barrier.
