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Biology 10-3

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Define artificial selection.
- the process by which humans change a species by breeding for certain traits
- humans are acting as the selective agent (determining which traits are favorable)
Define heritability.
- the ability of a trait to be passed down from one generation to the next
- things that are acquired in an organism's life are not heritable (for example, a broken bone)
- in order for artificial selection to occur, traits must be heritable (traits have to be in germ cells)
Define natural selection.
- a process in which individuals that have inherited beneficial adaptations produce more offspring than others
- the environment acts as the selective agent (the environment determines which traits are favorable)
- heritable differences are the basis for natural selection
Define population.
- all the individuals in a species that live in an area
What are the four main principles of natural selection?
- overproduction
- variation
- adaptation
- descent with modification
What is "descent with modification"?
- over time, natural selection will result in species with adaptations that are beneficial for survival and reproduction in a particular environment
- more individuals will have the trait in every following generation, as long as the environmental conditions stay the same
- evolution is the final outcome of natural selection, descent with modification is the end result
What is overproduction?
- organisms have more offspring that can survive
- occurs naturally
- this results in competition among offspring for resources
- increases the chance of some surviving
What is variation?
- heritable differences that exist are the basis for natural selection
- differences are the result of different genetic material
- individuals of a species differ due to genetic variation
What is adaptation?
- some individuals have certain variations that allow them to better survive than other individuals in their environment
- these individuals are "naturally selected" to live longer and produce more offspring that also have those adaptations
Define fitness.
- a measure of the ability to survive and produce more offspring
- organisms are the best fit for that environment, they are not always going to be the strongest or fastest
What are the similarities between artificial selection and natural selection?
- organisms breed to create new organisms
- descent with modification is the same
What is the difference between artificial selection and natural selection?
- in artificial selection, humans are the source of selection
- in natural selection, the environment is the source of selection
Why doesn't the survival of fittest accurately reflect Darwin's concept of evolutionary fitness?
- because the usual term for fitness (strong and fast) is different than the biological term for fitness (best fit organisms for the environment)
How would you explain a species that has remained the same over millions of years?
- there hasn't been a change in the environment
Why do some individuals survive and others don't?
- there is variation in different populations
Natural selection acts on ____ rather than the genetic material.
- phenotypes
Are new alleles made through natural selection?
- no, they are made through genetic mutations
What happens to traits in changing environments?
- a trait that is already in an environment can become more favorable if the environment changes
- as the environment changes, different traits become favorable
- a trait that is an advantage today may become a disadvantage
How can adaptations be compromises?
- some adaptive characteristics do not result in perfectly suited organisms
- some structures might take on new functions
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