B6 Natural Selection And Evolution Flashcards
Complete the sentence
Natural selection increase advantageous ……………
Phenotypes
What does genetic variation mean?
There’s a big mix of genetic variants (alleles) present in the population.
When do genetic variants arise?
When DNA randomly mutates.
Complete the sentence.
Occasionally a genetic variant can have a big effect on an organisms ……………
Phenotype
Complete the sentence
Most genetic ………… have no effect on phenotype and some of them only have a small influence on a phenotype.
Variants
Complete the sentence
Those genetic variants that do affect phenotype give rise to …………that make an organisms better suited to a particular environment.
Characteristics
What s an advantageous phenotype?
Characteristics that an organism inherits that mean it is better suited to an environment.
Complete the sentence
The resources living things need to survive are limited. Individuals in a community must …….. for these resources to survive.
Compete
How can a genetic variant give individuals a better chance of survival?
Genetic variants give individuals an advantageous phenotype, so they will have a better chance of successfully competing for resources and so have an increased chance of surviving, reproducing and passing on their genes.
How does an advantageous phenotype affect the next generation?
A greater proportion of individuals in the next generation will inherit the advantageous variants and so they’ll also have the phenotypes that help survival.
Complete the sentence
Over many generations, the advantageous phenotype becomes more …….in the population.
Common
Complete the sentence
The best characteristics are……………….and the species becomes more and more adapted to its environment.
Naturally selected
Example of natural selection
Rabbits ears
Once all rabbits had short ears and managed ok.
Then a gene mutated and one rabbit had big ears. This rabbit could hear better and was always the first to dive for cover at the sound of a predator.
He fathered a whole family of rabbits with big ears, and soon the boy rabbits left were the big eared rabbits because they were quicker to hear predators.
Eventually there were no short ear rabbits
What is evolution?
The change in inherited characteristics of a population over several generations, through the process of natural selection.
What is speciation?
When a new species is formed through evolution by natural selection.
The species phenotype change a so much that a completely new species is formed.
What effect can a physical barrier have on a species?
Speciation.
Conditions on each side of the barrier will be slightly different so the phenotypes that are beneficial will be different for each population.
Natural selection acts on each population to increase the proportion of the advantageous phenotype in that population, until they are so different that they can no longer breed together.
How does how quickly a species reproduces affect the speed at which a species evolves?
Some species reproduce very quickly and can therefore evolve more quickly. (Bacteria can be ready to start diving in just 20 minutes)
Some species reproduce much more slowly and there for take longer to evolve. (Humans usually only start reproducing after around 20-30 years)
Musk oxen have thick fur, which is advantageous in the cold climate in thick they live. Explain how the musk oxen may have developed this characteristics over many years. (4 marks)
Some of the musk oxen may have had a genetic variant/allele which gave them thicker fur (1 mark).
These oxen would have been more likely to survive and reproduce (1 mark) and so pass on the genetic variant/allele for thicker fur (1 mark).
This process of natural selection may have continued over many generations, until all the musk oxen had thick fur (1 mark).
