17. Microevoution: Genetic changes within populations
Penicillin was the first antibiotic drug based on a valuably occurring
substance that kills bacteria
How do bacteria become resistant to antibiotic?
The gnomes of bacteria vary among individuals and some bacteria have
genetic __ that allows them to withstand attack by antibiotics when we give
antibiotics to the infected patient we, create an environment friendly
bacteria that are even slightly resistant to the drug. The surviving bacteria
reproduces and the microorganisms become more common in the later
The evolution of antibiotic resistance in bacteria is an example of a
microevolution (a heritable change in the genetics of the population
A population of organisms include all the individuals of a sigh species that
live together in the same space and time
Darwin recognized the importance of heritable variation within
populations he also realized that __ selection can change the pattern
of rauation in a population from one generation to the next.
17.1 Variation in natural population
Phenotypic variation: the ______ in appearance or function - __ are
passed from generation to generation
17.1a Evolutionary biologists describe and quantify phenotypic variation.
Quantitative variation: Individuals differ in small environmental ways
Qualitative variation: They exist in 2 or more discrete states
intermediate forms are often absent (ex: Snow gasses have either
blue or white feathers.)
The existence of discrete varieties of a chaselces is called
Biochemical polymorphisms (human blood a,b, ab, o)
Phenotypic polymorphisms are described quantitively by calculating
the % or frequency of each point
17.1b phenotypic variation: can have gentile of environmental causes
Phenotypic variation within populations maybe caused by genetic
differences between individuals. By differences in environmental factors
that individuals experience or by _____ between genetics and the
Under some circumstances, organisms with different genotypes exhibit
On the other hand. Organisms with the same genotype sometimes exhibit
Only genetically based variation is subject to evolutionary change.
An organism phenotype is frequently the product of an intersection
between its genotype and environment
How can we determine whether phenotypic variation is caused by
environmental factors or by genetic differences?
We can test for an environmental cause experimentally by changing one
enviormental cariable and measuring the effects on genitcally similar subjects
17.1 c. several process generate genetic variation.
Microevoluationary process has two potential sources: the production of new
_____ and the ____ of existing ______
17.1d. populations often contain substantial genetic variation
_____- this technique separates 2 or more form of a give protein if they differ
significantly in shape, mass or net electrical charge.
17.2 POPULAITON GENETICS
17.2 A) all population have a genetic structure.
Populations are made up with individuals with its own genotype. In diploid
organisms an individual genotype includes 2 alleles of every locus. The ___ of
To describe the structure of a gene pool scientists identify the genotype in
a representative sample and calculate genotype frequencies
Allele frequencies represent the common or rarity of each allele in the gene
Remember that for a gene locus with two alleles. These are 3 genotype
frequencies (padq). The sum of the 3 genotype frequencies must somut the
sme of the 2 allele frequencies.
17.2b) The hardy-Weinberg principle is a null model that dejines how evolution
Null models-predict what they would be if a particular factor had no effect
Hardy Weinberg principle :- Specifies the conditions under which
population of diploid organisms achieve genetic equilibrium (the point at
which neither allele. Fregumes nor genotype frequencies change in success
Hardy Weinberg principles is a mathematical model
1. No mutation are occurring
2. The population is closed to immigration from other populations
3. The population is infinite in size
4. All genotypes in the population survive and reproduce equally well
5. Individuals in the population mate randomly with respect to
Under these restrictive conditions microevolution will not occur
17.3 The agent of microevolution
A population allele frequency will change over time if the
conditions of the Hardy Weinberg model are violated.
17.3a) Mutations create new genetic variation