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.