Natural selection Flashcards
What is the struggle for survival?
when more animals are born than will survive to reproduce (natural selection)
What is Darwin’s theory of evolution?
organisms best adapted to conditions will survive (survival of the fittest)
What happened when Darwin proposed his theory?
The public was outraged and did not believe him.
What are the steps (acronym) for natural selection?
Variation, Inheritance, Selection, Time, Adaptation (VISTA)
What does variation refer to?
a variation must exist in populations of single species
What does inheritance refer to in natural selection?
there is a variation due to genes inherited by parents
What does selection refer to in VISTA?
only the ‘fittest’ organisms possess characteristics which allow them to survive.
- these characteristics are passed onto offspring via genes
What does ‘survival of the fittest’ mean?
Organisms which adapt to changing environment survive, and are deemed ‘fit’, and those which do not adapt become extinct.
What happens in artificial selection?
Humans speed up what happens in nature, humans select desirable traits.
Who proposed speciation?
Charles Darwin
What is speciation?
Species living in different conditions evolve in different directions. Over generations, populations vary and eventually a new species develops.
How does natural selection apply in geographical regions?
Naturals selection is based on environmental conditions.
When does speciation usually occur?
same species, different location, different pressures = new species
- generally occurs when populations are isolated.
What are the evidences of evolution?
The fossil record, DNA hybridisation, comparing anatomy.
What is the fossil record?
fossils which depict the timeline of evolution. Evolutionary changes can be observed in fossils.
How do fossils form?
found in sedimentary rock when seas and lakes lay layers of sedimentary rick over millions of years. Occurs when not decomposed and conditions are right. Rock presses down and creates a mould, mould is filled and creates fossil.
Where are the oldest fossils found?
In the lowest layers, younger fossils found in upper layers.
How complex will organisms be on lower levels?
Simple organisms on lower levels, more complex on higher levels.
How can fossil record be used to find a common ancestor?
If a new species evolves from ancestral species, fossil records could contain organism that have same features of both modern + ancestors.
What is DNA hybridisation?
DNA is heated and separated, single strands are placed next to each other and bonded. If strands are similar, high amount of bonding will occur.
What does homoduplex mean?
both strands from the same DNA
What does heteroduplex mean?
DNA strands from different species.
When does pairing take place in DNA hybridisation?
when complementary bases are found.
When did mammals first appear?
~200mybp, evolved from reptile ancestors
what would you see in mammals related by evolution?
expected to see similar structures regardless of way of life
What is an example of anatomical similarities in mammals?
forelimb of all mammals very similar in number and structure of bones present.
what is an example of a homoogous structure?
the Pentadactyl limb
What is a homologous structure?
structure that is similar in closely related organisms, changed slightly due to different selection pressures in different environments.
What is an analogous structure?
arise in unrelated organisms due to action of different selection pressures.
Analogous structures illustrate concept of convergent evolution. What is convergent evolution?
an unrelated group of organisms develop similar characteristics. e,g insect wing and bird wing.
What is divergent evolution?
organisms develop structural differences over time, speciation occurs due to different selection pressures.
