BIO CHAPTER 14
Why is genetic diversity important?
- diverse gene pool gives a population more flexibility to survive in a changing environment. - the more genetically diverse a populations is the more ways it has to adapt
Hardy-Weinberg equilibrium 5 necessary conditions
1.No mutation introducing new alleles into the population 2.No natural selection favoring some alleles over others 3.An infinitely large population size (and, therefore, no genetic drift) 4.No influx of alleles from neighboring populations (i.e., no gene flow) 5.Random mating of individuals
example of nonadaptive evolution
A mutation causes an increase in the incidence of antibiotic sensitivity in a population of Staphylococcus aureus. The gene pool of a drastically reduced population of northern elephant seals is vulnerable to chance events.
hybrid inviability
A postzygotic barrier in which hybrid zygotes fail to develop or to reach sexual maturity
founder effect
A type of genetic drift in which a small number of individuals leaves one population and establishes a new population, resulting in lower genetic diversity than in the original population.
bottleneck effect
A type of genetic drift that occurs when a population is suddenly reduced to a small number of individuals, and as a result alleles are lost from the population.
Gene flow is the movement of ________ between different populations of the _______ species
Alleles, same
nonadaptive evolution
Any change in allele frequency that does not by itself lead a population to become more adapted to its environment; the mechanisms of ____________ are mutation, genetic drift, and gene flow.
Types of genetic drifts
Bottleneck effect Founder effect
Each of the 13 species evolved from only 1 mainland species.
Galápagos finches
Describes a frequency of genotypes and phenotypes in a nonevolving population
Hardy-Weinberg equilibrium
behavior isolation
Isolation caused by differences in courtship or mating behaviors
inbreeding
Mating between closely related individuals. ___________ does not change the allele frequency within a population, but it does increase the proportion of homozygous individuals to heterozygotes.
reproductive isolation
Mechanisms that prevent mating (and therefore gene flow) between members of different species.
Non adaptive examples
Mutation Gene flow Genetic drift
How do different evolutionary mechanisms influence the composition of a gene pool?
Mutation-occur in the gamete-producing cells during DNA, when fertilized will enter the gene pool Migration (gene flow)- movement of alleles from one population to another. Genetic drift- allele changes by chance only, decrease genetic diversity of a population, more effect in smaler populations. natural selection- if the allele benifits the organism the frequency should increase.
Genetic diversity in a population is reflected by
Number of different alleles
genetic drift
Random changes in the allele frequencies of a population between generations; genetic drift tends to have more dramatic effects in smaller populations than in larger ones.
Inbreeding of closely related individuals occur is what type of populations
Small and isolated
Occurs when a gene pool seporated, gene flow is restricted, and populations diverge genetically over time
Speciation
gametic isolation
Sperm of one species may not be able to fertilize eggs of another species
Which of the following must be true if a population is undergoing evolution? Select the TWO answers that are correct. A high mutation rate is increasing genetic variability in the population. Genetic drift is causing random changes in the gene pool. The most advantageous of the alleles are increasing in frequency. The allele frequency of the population is changing over time. The gene pool is changing over the course of generations.
The allele frequency of the population is changing over time. The gene pool is changing over the course of generations.
biological species concept
The definition of a species as a population whose members can interbreed to produce fertile offspring.
speciation
The genetic divergence of populations, leading over time to reproductive isolation and the formation of new species.
gene flow
The movement of alleles from one population to another, which may increase the genetic diversity of a population.
inbreeding depression
The negative reproductive consequences for a population associated with having a high frequency of homozygous individuals possessing harmful recessive alleles.
Hardy-Weinberg principle
The principle that, in a nonevolving population, both allele and genotype frequencies remain constant from one generation to the next.
allele frequency
The relative proportion of an allele in a population.
population genetics
The study of the genetic makeup of populations and how the genetic composition of a population changes.
gene pool
The total collection of alleles in a population.
Which statements are true for both genetic bottlenecks and the founder effect?
They both result in a smaller gene pool. They both happen by chance.
What is a gene pool?
Total collection of alleles in a population
Can evolution be adaptive and non adaptive
True
What is an effect of gene flow?
an increase in the variety of alleles within the gene pool of a population
temporal isolation
form of reproductive isolation in which two populations reproduce at different times
In the Galapagos Islands, which of the following would have prevented the evolution of the many different species of finches
frequent migration of finches between the islands
hybrid infertility
hybrid offspring are sterile or have low fertility
How does the gene pool of an evolving population compare to the gene pool of a nonevolving population?
in an evolving population the gene pool is changing from generation to generation, in nonevolving population allele and genotype frequencies do not change over time. ( Hardy-Weinberg equilibrium)
mechanical isolation
mating is attempted, but morphological differences prevent its successful completion
Plants pollinated by the hummingbird do not receive pollen from plants pollinated by the bumble bee. This is an example of _____.
mechanical isolation
There are five characteristics that a population must have to NEVER experience a change in allele frequencies. Which of these is NOT one of them? no mutations a large population size natural selection no gene flow a lack of random mating
natural selection
Ecological isolation
species occur in the same area, but they occupy different habitats and rarely encounter each other
Two species of mice breed at different times of the year. This is an example of which type of isolation?
temporal
example of gene flow
the carriage of seeds between two separate urban forests by wildlife such as squirrels and rats that travel back and forth between the two
Hardy whinburg equilibrium equation
•Baseline to judge if a population is evolving •Hardy-Weinberg equation p2 + 2 pq + q2 = 1 •p2 is the frequency of homozygous dominants •2 pq is the frequency of heterozygotes •q2 is the frequency of homozygous recessives