GENES AND VARIATION OBJECTIVES: 16.1 Explain what a gene pool is.
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Transcript of GENES AND VARIATION OBJECTIVES: 16.1 Explain what a gene pool is.
GENES AND VARIATION
OBJECTIVES: 16.1
Explain what a gene pool is.
Identify the main source of inheritable variation in a population.
State determines the numbers of phenotypes for a given trait.
Genetic ________ is studied in a population (a group of individuals of the same ______ that interbreed).
The individuals share a common group of genes called a ____ _____.
A gene pool consists of ___ genes, including all the different _______, that are present in a population.
The relative frequency of an _____ is the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur.
_________ is any change in the relative frequency of alleles in a population.
The two main sources of genetic variation are __________ and the genetic _________ that results from sexual reproduction.
A mutation is any _______ in a sequence of DNA.
They can occur because of mistakes in ________, radiation, or chemicals in the environment.
Many mutation do not produce changes in the _________ of the individual.
Human _____ mutation.
They believed that this man was born with the ___ virus that causes the growth of all these ______ that cover his body and creates the illusion that branches are covering his skin
Most _______ differences are due to gene shuffling that occurs during the production of _______.
Another process, ___________, also occurs during ________ which increases the number of different _________ that can appear in offspring.
The number of _________ produced for a given trait depends on how many ______ control the trait.
Among humans, a widow’ peak – a downward dip in the center of the hair line – is a ______-gene trait.
The allele for the widow’s peak is _________ over the allele for the hair line with no widow’s peak.
Many traits are controlled by two or more genes and are, called _________ traits.
Each gene of a trait has two or more ______.
EVOLUTION AS GENETIC CHANGE
OBJECTIVES: 16.2
Explain how natural selection affects single-gene and polygenic traits.
Describe genetic drift.
List the five condition needed to maintain genetic equilibrium.
The _______ of an organism is measured in its ability to _____ its genes on the next generation.
_______ _______ never acts directly on _____.
Because it is an entire _______ – not a single gene – that either survives and reproduces or dies without reproducing.
If and individual produces many ________, its alleles stay in the gene pool and many increase in frequency.
Natural selection on single-gene traits can lead to changes in allele frequencies and thus to _______.
During the ________ Revolution a lot of soot was put into the atmosphere and it collected on trees.
The soot making the ______ peppermoth more visible.
Because of this the _____ peppermoth became predominant over it white cousin.
Peppermoth of England
Natural selection can affect the __________ of phenotypes in an of three ways.
1. __________ selection – when the individuals at one end of the curve have higher fitness than those in the middle or the other end.
2. ________ selection – when individuals near the center have higher fitness than the individuals at either end of the curve.
3. _________ selection – when the individuals at the upper and lower ends of the curve have higher fitness than those near the middle.
In _____ populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance.
Over time, a series of chance occurrences of this type can cause an _____ to become common in a population.
_____ ______ is the random change of allele frequency.
A situation in which ____ frequencies change as a result of the ________ of a small subgroup of a population.
The ____________ principal states that the allele frequencies in a population will remain _______ unless one or more factor cause those frequencies to change.
Genetic ________ is the situation the allele frequency remains _______.
____ conditions are required to maintain genetic equilibrium from generation to generation:
1. There must be _______ mating; all members of the population must have a equal opportunity to produce offspring.
2.The population must be very large; genetic drift has less ______ on a large population
3.There can be no movement ____ or ___ of the population; new individuals may bring in new _____ in to a population.
4. No _________; if genes mutate from on form into another form, new alleles may be introduce into the population.
5. No ________ selection; all genotypes must have the same probabilities of _______ and __________.
THE PROCESS OF SPECIATION
OBJECTIVES: 16.3
Identify the condition necessary for a new species to evolve.
Describe the process of speciation in the Galapagos finches.
__________ is the formation of new species.
A _______ is a group of organisms that breed with one another and produce ______ offspring.
As new species evolve, population become reproductively ________.
When the members of two populations cannot _________ and produce ______ offspring, reproductive isolation has occurred.
At that point the _________ had different genic pools.
_________ isolation occurs when two populations are capable of interbreeding but have difference in courtship _____ or other reproductive strategies that involve behavior.
__________ isolation occurs when two populations are separated by geographic barriers such as rivers, ________ or bodies of water.
_______ isolation occurs when two or more species reproduce at different times.
Geographic isolation
Speciation in the _______ finches occurred by founding of a new population, geographic isolation, changes in the new population’s gene pool, and _______ competition.
A few finches (_______) from the South American mainland – species A – flew or were blown to one of the Galapagos Islands.
Later a few birds of species A cross to another island (________).
Over time, populations on each island become _______ to their local environment.
One island may have produced a _____ with a thick husk and the birds adapted by growing _____ beaks, resulting in species B.
A few birds from species B fly over to the island inhabited by species A.
Species A will not mate with species B because species A prefers _____ beak size.
The gene pool of the two species are now ______.
The two are now _______ species.