B6 Evolution (page 76) Flashcards
What is the Theory of Evolution?
All of today’s species have evolved from simple life forms that first started to develop over three billion years ago. (charles Darwin)
Charlies Darwin came up with a really important theory about Evolution called what?
Evolution by natural selection.
What did Charles Darwin know about Phentotypic variation?
He knew that organisms in a species show a wide variation in their characteristics (phenotypic variation).
Darwin also knew that organisms have to compete for limited resources in an ecosystem
What did Charles Darwin conclude about organisms with the most suitable characteristics for the environment?
Darwin concluded that the organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive.
This idea is called the ‘Survival of the fittest’
The successful organisms that survive are more likely to do what?
they are more likely to reproduce and pass on the genes for the characteristics that made them successful to their offspring.
The organisms that are less well adapted would likely do what?
they would be less well adapted and would be less likely to survive and reproduce, so they are less likely to pass on their genes to the next generation.
Over time, beneficial characteristics become more common in the population and the species changes, what is this called?
it evolves.
(evolution)
Who was Charles Darwin?
He transformed the way we understand the natural world with ideas that, in his day, were nothing short of revolutionary.
(revalutionary means involving or causing a complete or dramatic change).
Why wasn’t Charles Darwin’s theory ‘Evolution by natural selection’ perfect?
Because the relevant scientific knowledge wasn’t available at the time, he couldn’t give a good explanation for why new characteristics appeared or exactly how individual organisms passed on beneficial adaptations to their off spring.
What discovery supported Charles Darwin’s idea theory ‘Evolution by natural selection’ and how?
the discovery of Genetics supported Charles Darwin’s idea.
It provided an explantion of how organisms born with beneficial characteristics can pass them on (i.e. via their genes) and showed that it is genetic variants (see page 75) that give a rise to phenotypes that are suited to the environment.
Other evidence was also found by looking at fossils of different ages (the fossil record) - this allows you to see how changes in organisms developed slowly over time.
The relatively recent discovery of how bacteria are able to evolve to become resistant to antibiotics also further supports evolution by natural selection. The theory of evolution by natural selection is now widely accepted.
What is Speciation?
The development of a New Species
Over a long period of time, the phenotype of organisms can change so much because of natural selection that a completely new species is formed. This is called speciation.
When do Speciation happen?
it happens when populations of the same species change enough to become reproductively isolated. - This means that they can’t interbreed to produce fertile offspring.
What is Extinction?
This is when NO individuals of a species remain.
The fossil record contains many species that don’t exist any more, these species are said to be what?
Extinct.
What reasons do species become extinct?
1) The environment changes too quickly (e.g. destruction of habitat).
2) A new predator kills them all (e.g. humans hunting them).
3) A new disease kills them all
4) They can’t compete with another (new) species for food.
5) A catastrophic event happens that kills them all (e.g. a volcanic eruption or a collision with an asteroid).
