Evolution Flashcards
Define variation.
Differences within or between species.
What is continuous variation?
Continuous variation is where there are two extremes and a full range of values in the middle; most are individuals are in the middle but a minority are at each extreme.
What is discontinuous variation?
Discontinuous variation is where there are distinct categories and no intermediate values.
What are genetic causes of variation?
Genes define our characteristics, and the combination of alleles we receive from our parents is unique.
What are environmental causes of variation?
Many characteristics can be affected by the environment i.e. if a tree that was supposed to be 6m tall was planted where there was little water it may not grow very high of a pat is overfed it may become obese.
What were Darwin’s four observations?
Offspring appear genetically similar to their parents
No two individuals are identical
Organisms have the ability to produce large numbers of offspring
Populations tend to remain fairly stable in size
What did Darwin’s observations cause him to conclude?
There is a struggle to survive
Better adapted individuals survive and pass on their characteristics
Over time, a number of changes may give rise to a new species
What fossil evidence is there to support evolution?
Fossils show changes over time
There are ways to date fossils
Fossils show links between groups of organisms
Many fossils are of an organism that no longer exists
It is possible to compare the DNA extracted from some fossils
What DNA evidence is there for evolution?
Genes can be compared by sequencing the bases in DNA; more distantly related species have more differences in their DNA thus must have evolved as a different species further back in time
How are variations, adaption and selection major components of evolution?
Variation must occur before evolution can take place
Variation arises due to random mutation and sexual reproduction
Once variety exists certain individuals have a selective advantage over others
Individuals with the mutations will survive and reproduce
Their offspring will inherit the mutation
The next generation will be better adapted to their environment
Over time the group of organisms become well adapted to the environment
Why is resistance a problem?
Exterminators i.e pesticides or antibiotics are designed to kill an organism, if one of these organisms develop resistance through a mutation it will survive and pass on its gene creating a resistant species.
What molecular evidence is there to support evolution?
Two closely related species will have similar or identical biological molecules as they will have separated more recently.
Define speciation.
The formation of a new species.
