Variation And Natural Selection Flashcards
What is variation?
The differences which exist between individuals belonging to the same species.
What is continuous variation?
When there is a gradual change in characteristics across a population, e.g. height, weight, length of fingers.
If a feature shows continuous variation it should give a normal distribution curve, where most individuals are around the average or mean value and there are relatively few at either extreme.
What is discontinuous variation?
In this the population can be clearly divided into discrete groups or categories.
There is a sharp distinction between individuals with no in between values. E.g. hand dominance, blood groups, tongue rolling.
How should continuous and discontinuous variation be measured on a graph?
Continuous - histogram
Discontinuous - bar chart
What are some causes for variation?
Genetic makeup, e.g. eye colour
Environmental factors, e.g. increase sunshine resulting in greater plant growth
Combination of both, e.g. height - genotype gives potential to be tall, though this is only achieved with good diet and overall good health.
How does natural selection (and thus evolution) work?
If there is a lot of variation in a species in a particular area, it is likely that over time some of these organisms will be better equipped to prosper and survive in that environment.
These adaptations are important when organisms have to compete with each other for resources. This ensures only the strongest and best adapted of each species will survive and be able to obtain vital resources. This is known as Survival of the Fittest.
What is the theory of evolution?
The theory of evolution explains how species change over long periods of time and how new species come into being.
How did Charles Darwin come up with the theory of evolution?
He studied the variation in plants and animals during his 5 year voyage around the world in the late 19th century in the HMS Beagle.
Whilst studying wildlife in the Galápagos Islands he noticed the native finches showed wide variation - eg in beak shape and size - from Islands to island. He deduced these differences made the finches better adapted to their particular environment.
He concluded that each locality one or more finches happened to acquire, by random mutation, a beak shape more suitable for the food sources in that location. This gave them a competitive advantage over other members of their species, enabling them to breed and pass on the mutation to the next generation, which construed until it spread throughout the population.
What is natural selection?
The survival of organisms that are best suited to surviving and reproducing in their environment.
What are fossils?
The remains of living organisms that have been preserved (usually in rocks) for millions of years.
What is extinction?
When species or whole families of organisms die out, and there are no more living examples of it left.
What factors contribute to extinction?
Rapid climate or environmental change
Impact of man
Hunting by animals
Impact of a new disease
A change or loss of habitat
Failure to compete with other species
What are some examples of extinction?
The dodo - 1600’s Mauritius was colonised by the Dutch, who killed the bird for food, cleared its habitat, and introduced species that ate its eggs and young, e.g. rats.
Woolly mammoth - became extinct due to climate change, eliminating it’s natural habitat.
The corncrake - local bird virtuality eliminated from NI due to a reduction in growing hay and increase in silage cutting. This is where they lay their eggs, and when the hay is cut too early the chicks aren’t mature enough and are killed.
What is selective breeding?
When the course of natural selection is manipulated by deliberately selecting particular characteristics or traits in many plants or animals that are of use to us.
