Bio Test 3 Lesson 14

Evolutionary species concept:

- Groups of organisms may be in different stages of speciation, and may share a portion of their gene pools. - Some phenotypically distinct "species" may interbreed and leave fertile progeny.

What are the Hardy-Weinberg Assumptions?

- No mutations - No gene flow - Random mating - No genetic drift - No selection

Biological species concept:

- The members of one species interbreed and have a common gene pool. - Different species are reproductively isolated from one another, i.e. they do not interbreed or leave fertile progeny.

Sympatric speciation

- Two populations are not geographically isolated. - Genetic changes (mutations) occur that cause some individuals in the population to become reproductively isolated from other individuals. - Mutated individuals become a "subpopulation" and establish their own separate gene pool. - Genetic drift and different natural selection pressures allow the two isolated gene pools to accumulate different alleles and allele frequencies. - Organisms in separate gene pools become genetically and phenotypically different from each other. - The two populations will not interbreed. - Evolution and speciation have occurred.

What are the Types of Natural Selection?

-Directional selection - Stabilizing selection - Disruptive selection

2. A mutation in a rabbit population that affects their leg muscles such that some of them are not able to run as fast to escape predators would (Select all that apply.) -Mean that microevolution is taking place. -Indicate that the population is under selection pressure. -Result in a change in allele frequencies in the population. -Mean that the population is not at Hardy-Weinberg equilibrium.

-Mean that microevolution is taking place. -Indicate that the population is under selection pressure. -Result in a change in allele frequencies in the population. -Mean that the population is not at Hardy-Weinberg equilibrium.

18. The research that studied the effect of industrial melanism on moth populations demonstrates that (Select all that apply.) -Microevolution does occur. -Selection pressure can change allele frequencies. -Phenotypes in a population can change. -None of these are correct.

-Microevolution does occur. -Selection pressure can change allele frequencies. -Phenotypes in a population can change.

Explain the Hardy-Weinberg Assumption of No Mutations:

-Mutations are physical changes in the structure of DNA. -Mutations may have an effect on the structure or function of an organism. -Modifications in structure or function may allow the organism to survive in a changing environment, while organisms without modifications may perish. -Organisms with modifications that survive may leave more progeny than those without modifications. -In succeeding populations there will be more modified alleles than in previous generations. -This may result in a distinct evolutionary trend or in speciation.

13. Which of the following statements best matches the evolutionary species concept? (Select all that apply.) -Some phenotypically distinct "species" may interbreed and leave fertile progeny. -Groups of organisms may be in different stages of speciation, and may share a portion of their gene pools. -Different species are reproductively isolated from one another, i.e. they do not interbreed or leave fertile progeny. -The members of one species interbreed and have a common gene pool.

-Some phenotypically distinct "species" may interbreed and leave fertile progeny. -Groups of organisms may be in different stages of speciation, and may share a portion of their gene pools.

10. A population of small river fish lay their eggs among the reeds along the banks of the river. Some of the fish have a genotype that causes them to lay their eggs at the base of the reeds where predators are less likely to find them. Other fish have a genotype that causes the outer layer of the eggs to have a coloration that camouflages them from the view of predators. After many generations the two kinds of fish are not able to interbreed. This is an example of (Select all that apply.) A prezygotic isolating mechanism Stabilizing selection Speciation Disruptive selection

-Speciation -Disruptive selection

Postzygotic isolating mechanisms:

-These are mechanisms that function after successful fertilization has taken place, i.e. the sperm has fertilized the egg. They function in preventing hybrids from developing or reproducing. Zygote mortality—fertilized egg (zygote) spontaneously aborts Embryo or fetus mortality—embryo or fetus spontaneously aborts Hybrid sterility—hybrid grows but produces no viable offspring Reduced F2 fitness—hybrid grows and produces viable offspring, but second generation offspring have reduced survival and fertility

Prezygotic isolating mechanisms:

-mechanisms that prevent fertilization from occurring. They include mechanisms that prohibit attempts at reproductive behavior and mechanisms that prohibit successful fertilization of the egg even though reproductive behavior (e.g. copulation or pollination) might have occurred successfully. Habitat isolation—individuals located in separate habitats Temporal isolation—individuals not in reproductive condition at the same time Behavioral isolation—individuals do not exhibit mutually acceptable reproductive behavior Mechanical isolation—individuals have incompatible anatomical structures

6. If the frequency of the recessive allele is 0.45, what is the frequency of the dominant allele? 1.55 -0.45 0.55 0.45 There is not enough information given to make this computation.

0.55

How do you compute allele frequencies in a population?

1) In a population of 100 individuals we have the following numbers of individuals in each of the indicated genotypes: 36 homozygous dominant (RR) 48 heterozygous (Rr) 16 homozygous recessive (rr) 2) Each individual has two alleles for the gene since it is a diploid organism. Therefore, we have the following numbers of each of the two alleles "R" and "r" in the population. 3) To calculate the allele frequencies in this population we do the following. A) Number of "R" alleles divided by the total number of alleles in the population equals frequency of "R" allele. B) 120/200 = 0.60 (60% of the alleles are of the "R" type) C) Number of "r" alleles divided by the total number of alleles in the population equals frequency of "r" allele. D) 80/200 = 0.40 (40% of the alleles are of the "r" type) 4) What will be the genotypic frequencies in the next generation? Use a Punnett Square (contingency table) to compute genotypic frequencies for all possible pair-wise combinations of alleles.

Directional selection:

1) Organisms with an extreme genotype are favored over those with a less extreme genotype. 2) Numbers of individuals in the population with the extreme genotype will increase in number and leave more progeny that have the extreme genotype in the next generation. 3) Allele frequencies in succeeding generations will differ from those of preceding generations. 4) Evolution will have occurred.

Stabilizing selection:

1) Organisms with an intermediate genotype are favored over those with either of the extreme genotypes. 2) Numbers of individuals in the population with the intermediate genotype will increase in number and leave more progeny that have the intermediate genotype in the next generation. 3) Allele frequencies in succeeding generations will differ from those of preceding generations. 4) Evolution will have occurred.

Explain the study of the peppered moths and microevolution:

1) Peppered moth populations contained two phenotypes: light color and dark color. 2) In pre-industrial times the trunks of the trees had a natural light color. 3) Moths that had a dark color were easily seen by birds, and were eaten. 4) Moths that had a light color were not easily seen by birds, and were not eaten. 5) Dark-colored moths contributed less of their alleles to the next generation. 6) The number of dark-colored moths in the population decreased. 7) In post-industrial times the trunks of the trees were covered in dark soot. 8) Moths that had a dark color were not easily seen by birds, and were not eaten. 9) Moths that had a light color were easily seen by birds, and were eaten. 10) Light-colored moths contributed less of their alleles to the next generation. 11) The number of light-colored moths in the population decreased. In the case of industrial melanism discussed above, we say that there was selection against moths of a certain phenotype, depending on the environment in which they were found. As the environment changed, the gene pool of the population changed to reflect the changing selection pressure. Other examples of microevolution include the build-up of resistant types of insects in a population with the continued application of the same kinds of pesticides, or the prevalence of antibiotic-resistant bacteria in some of the sexually-transmitted diseases. All of these represent changes in allele frequencies in the gene pool due to environmental selection pressures.

What are the two classes of reproductive isolating mechanisms?

1) Prezygotic isolating mechanisms 2) Postzygotic isolating mechanisms

Disruptive selection:

1) Two or more genotypes are favored over organisms with intermediate genotypes. 2) Numbers of individuals in the population with the extreme genotype will increase in number and leave more progeny that have the extreme genotype in the next generation. 3) Allele frequencies in succeeding generations will differ from those of preceding generations. 4) Evolution will have occurred.

Allopatric speciation:

1) Two or more subpopulations of a population become geographically isolated. 2) Gene flow between the subpopulations is prevented by some isolating mechanism. 3) This forms two separate gene pools. 4) Genetic drift and different natural selection pressures allow the two isolated gene pools to accumulate different alleles and allele frequencies. 5) Organisms in separate gene pools become genetically and phenotypically different from each other. 6) Even when geographical barrier is removed, the two populations will not interbreed because of isolating mechanisms. 7) Evolution and speciation have occurred.

7. In a population that has the following numbers of individuals in each of the following genotypes (AA = 72, Aa = 89, aa = 29) what is the allele frequency for each allele? -A = 0.85, a = 0.15 -There is not enough information given to make this computation. -AA = 144, Aa = 178, aa = 58 -A = 0.61, a = 0.39

A = 0.61, a = 0.39

gene pool:

A gene pool is all of the alleles of all genes of all individuals in the population.

Explain the Hardy-Weinberg Assumption of No Gene Flow:

A) Gene flow involves the movement of alleles into or out of a population. B) This is accomplished by the immigration or emigration of sexually reproducing individuals. C) Gene flow can increase the allele variation in a population by introducing new alleles. D) Continued gene flow between two gene pools can make the two gene pools similar. E) Continued gene flow between two gene pools can prevent speciation (evolution) from occurring.

Explain the Hardy-Weinberg Assumption of No Genetic Drift:

A) Genetic drift refers to a change in allele frequencies of a population due to chance. B) Small populations exhibit genetic drift to a greater degree than large populations. C) In a small population the chances are greater that a relatively rare genotype will contribute significantly to the next generation, resulting in a change in allele frequency (evolution). D) Populations that experience a near extinction event have fewer individuals and fewer alleles to contribute to the next generation. This is called the "bottleneck effect." E) Populations that originate from a small number of individuals have a reduced number of alleles. This is called the "founder effect."

Explain the Hardy-Weinberg Assumption of No Selection:

A) Natural selection is a process that favors (allows to survive) one particular genotype over another. B) Natural selection may take the form of abiotic (non-living) factors, such as moisture, temperature, etc. C) Natural selection may take the form of biotic (living) factors, such as predators, competitors, etc. D) Individuals of the favored genotype survive to reproduce with greater frequency, thereby passing more of their alleles to the next generation, than those not favored for survival. E) This change in allele frequency is evidence that evolution has occurred.

Explain the Hardy-Weinberg Assumption of Random Mating:

A) Random mating occurs when individuals pair for sexual reproduction by chance alone. B) Nonrandom mating occurs when an individual will preferentially select one mate over another on the basis of some genetically based trait. C) Nonrandom mating tends to divide the population into genotypic classes, between which there is a reduced occurrence of mating. D) Reduced gene flow between genotypic classes may result in nearly complete or complete segregation, and evolution.

1. What is the correct matching pattern between the following terms and the descriptions below? A. Stabilizing selection I. Organisms with an extreme genotype are favored over those with a less extreme genotype. B. Disruptive selection II. Organisms with an intermediate genotype are favored over those with either of the extreme genotypes. C. Directional selection III. Two or more genotypes are favored over organisms with intermediate genotypes. A-I, B-III, C-II A-III, B-II, C-I A-II, B-I, C-III A-I, B-II, C-III A-II, B-III, C-I

A-II, B-III, C-I

14. What is the correct matching pattern between the terms on the left and the descriptions on the right? A. p I. Frequency of the heterozygous genotype B. q II. Frequency of the dominant allele C. p2 III. Frequency of the recessive allele D. q2 IV. Frequency of the homozygous dominant genotype E. 2pq V. Frequency of the homozygous recessive genotype A-V, B-IV, C-II, D-III, E-I A-I, B-III, C-II, D-V, E-IV A-I, B-II, C-III, D-IV, E-V A-II, B-I, C-V, D-IV, E-III A-II, B-III, C-IV, D-V, E-I

A-II, B-III, C-IV, D-V, E-I

9. In a population that has the following numbers of individuals in each of the following genotypes (AA = 72, Aa = 89, aa = 29), and assuming that individuals carrying the homozygous recessive genotype are sterile, how many individuals of each genotype will there be in a population of 250 individuals? AA = 130, Aa = 100, aa = 20 AA = 93, Aa = 120, aa = 37 AA = 120, Aa = 93, aa = 37 AA = 80, Aa = 100, aa = 70 AA = 110, Aa = 140, aa = 0

AA = 130, Aa = 100, aa = 20

12. In a population that has the following numbers of individuals in each of the following genotypes (AA = 72, Aa = 89, aa = 29), and assuming that the allele frequency does not change, how many individuals of each genotype will there be in a population of 250 individuals. AA = 30, Aa = 200, aa = 20 AA = 50, Aa = 150, aa = 50 AA = 93, Aa = 120, aa = 37 AA = 64, Aa = 156, aa = 30 AA = 37, Aa = 120, aa = 93

AA = 93, Aa = 120, aa = 37

20. The type of speciation in which subpopulations become geographically isolated is called -Sympatric speciation -Reproductive isolation -Allopatric speciation -Reduced fitness -Hybrid sterility

Allopatric speciation

microevolution:

Changes in allele frequencies over a few generations is microevolution. The conditions of the Hardy-Weinberg Law are rarely, if ever, met in real life. Most populations violate one or more of these conditions, causing allele frequencies to depart from equilibrium. Departure of allele frequencies from equilibrium is evidence of a changing population, and evidence that evolution has, or is, occurring.

What did Darwin and Wallace Theorize?

Darwin and Wallace theorized on the general principles of natural selection that could produce new species, but they were unaware of any genetic mechanism that could account for how evolution could occur. During that time Gregor Mendel was experimenting with his garden peas, and was providing the information that they needed to make the connection between what they were seeing in nature and what was actually happening in the cell. Unfortunately, Mendel's work would slip into obscurity until the early 1900's when it was rediscovered. At that point in time the science of evolution would make dramatic leaps forward in its efforts to explain the genetic mechanisms that are responsible for the rise of new species.

5. A population of goldenrod plants that is growing on a sand dune contains some individuals that have a genotype that gives them a greater tolerance for dry soil than do other plants. Sand continues to blow onto the dune, increasing its height, and increasing the distance between the plant roots and available water. Eventually a greater number of drought-tolerant goldenrods are found in the population. This is an example of Stabilizing selection A post-zygotic isolating mechanism Disruptive selection Directional selection

Directional selection

industrial melanism:

Environmental changes because of the start of the industrial revolution the prevalence of dark-colored varieties of animals (especially moths) in industrial areas where they are better camouflaged against predators than paler forms.

3. Populations that originate from a small number of individuals have a reduced number of alleles. This is called the Genetic drift effect Disruptive effect Postzygotic isolating mechanism Founder effect Bottleneck effect

Founder effect

19. All of the alleles of all genes of all individuals in the population is called a Hybrid swarm Gene pool Genetic drift Bottleneck Speciation event

Gene pool

8. Which of the following is not a prezygotic isolating mechanism? Habitat isolation Reproductive behavior Hybrid sterility Temporal isolation Behavioral isolation

Hybrid sterility

What is The Hardy-Weinberg Principle?

In 1908 G.H. Hardy and W. Weinberg recognized that the pattern of genotypic and allele frequency computation followed the binomial equation: p2 + 2pq + q2 = 1 Where: p = the frequency of the dominant allele q = the frequency of the recessive allele p2 = the frequency of the homozygous dominant genotype 2pq = the frequency of the heterozygous genotype q2 = the frequency of the homozygous recessive genotype

Random mating:

Individuals form mating pairs by chance and not according to some factor that is controlled by their genotype or phenotype

16. The study of how evolution works at the genetic level is called Metagenesis Microevolution Prezygotic isolating mechanisms Pangenesis Genotype analysis

Microevolution

gene flow:

Migration of alleles into or out of the population

17. In sympatric speciation individuals in the population become reproductively isolated because of Continental drift Mutations Geographical barriers Temporal isolation

Mutations

4. Which one of the following is not one of the assumptions of the Hardy-Weinberg principle? Non-random mating No selection No mutation No immigration or emigration No genetic drift

Non-random mating

What is a species?

Over the centuries biologists have found it difficult to agree upon the definition of species. The most commonly accepted definition is the biological species concept, but there are many notable exceptions to this definition. For example certain species of grasses in the tribe to which wheat belongs are able to interbreed and leave fertile offspring, apparently defying the biological species concept. In fact, species in different genera of this tribe are fully cross-fertile. Other examples of the difficulty of the biological species concept are found in some of the wind-pollinated trees, like oaks, elms, and willows. In these generations one can find populations of trees in which each individual appears to have mixtures of characteristics that belong to different species. One might be tempted to say that the problem in these cases is not with the biological species concept, but rather with the taxonomy. Maybe the species limits need to be broadened to include all individuals that are interbreeding. In some groups, like those cited above, this would be unfortunate since it might result in very large, ill-defined species that have no meaningful relation to nature. Instead, it might be better to consider a different species definition that allows for the possibility that populations may be in the process of speciation, and actually consist of subpopulations in varying degrees of separation. The evolutionary species concept seeks to address this situation. It may be that, through the speciation process, populations pass through an evolutionary species phase where subpopulations become increasingly reproductively separated, until they reach the biological species phase where they become completely reproductively isolated.

the "bottleneck effect.":

Populations that experience a near extinction event have fewer individuals and fewer alleles to contribute to the next generation.

the "founder effect.":

Populations that originate from a small number of individuals have a reduced number of alleles.

Explain Natural Selection:

Probably the most often violated assumption of the Hardy-Weinberg principle in natural populations is the absence of any selection pressure. It is difficult to imagine a population that exists in nature that is not subject to some kind of selection forces that favor or disfavor some genetically-based structure or function. There are three types of selection pressure. In each of them there are selection forces that cause the genetic composition of the population to change through time. The genetic change of a population through time is called evolution.

11. Which of the following is a postzygotic isolating mechanism? (Select all that apply.) Reduced F2 fitness Zygote mortality Hybrid sterility Embryo or fetus mortality

Reduced F2 fitness Zygote mortality Hybrid sterility Embryo or fetus mortality

Reproductive isolating mechanisms:

Reproductive isolation means that gene flow does not occur between species.

See Lesson info for charts

See Lesson info for charts

What is Modes of speciation?

Speciation has occurred when two groups of organisms do not, and would not, be able to produce fertile progeny

Speciation:

Speciation is the process of forming a new species from a pre-existing species. We can think of it as a natural result of the process of microevolution. If selection pressures remain relatively constant over a long period of time, the genetic constitution of the population may have changed significantly, to the point that the resulting population is genetically distinct from its previous condition. We would say that a new species has been formed. Speciation is not usually a sudden process, but rather one that proceeds slowly through many generations. We can deduce from the fossil record that speciation has occurred in the past; and we can see that it is occurring in populations today. Since speciation is a slow process, and some populations today are undergoing speciation, it makes defining a species and determining species limits very difficult for some groups of organisms.

Explain The Hardy-Weinberg principle:

The Hardy-Weinberg principle states that allele frequencies in the gene pool of a sexually reproducing population will remain in equilibrium as long as the following five conditions are met: 1) No mutations—No changes in alleles occur, or they are balanced by opposite allele changes. 2) No gene flow—Migration of alleles into or out of the population does not occur. 3) Random mating—Individuals form mating pairs by chance and not according to some factor that is controlled by their genotype or phenotype. 4) No genetic drift—The population is very large, and changes in allele frequencies due to chance alone are insignificant. 5) No selection—No selective factor or agent favors one genotype over another.

15. Populations that experience a near extinction event have fewer individuals and fewer alleles to contribute to the next generation. This is known as The bottleneck effect Darwin's effect A prezygotic isolating mechanism Extirpation Temporal isolation

The bottleneck effect

population:

a group of individuals of the same species that are interbreeding and leaving offspring.

selection:

agent favors one genotype over another

What are the 2 modes of speciation?

allopatric speciation sympatric speciation

selection pressure:

an agent of differential mortality or fertility that tends to make a population change genetica

genetic drift:

changes in allele frequencies due to chance

mutations:

changes in alleles

Embryo or fetus mortality:

embryo or fetus spontaneously aborts

Zygote mortality:

fertilized egg (zygote) spontaneously aborts

Reduced F2 fitness

hybrid grows and produces viable offspring, but second generation offspring have reduced survival and fertility

Hybrid sterility

hybrid grows but produces no viable offspring

Behavioral isolation:

individuals do not exhibit mutually acceptable reproductive behavior

Mechanical isolation:

individuals have incompatible anatomical structures

Habitat isolation:

individuals located in separate habitats

Temporal isolation:

individuals not in reproductive condition at the same time

Adaptive radiation:

is a type of allopatric speciation. -rapid development of many new species from a single ancestral species. The new species have subsequently spread out and become adapted to different habitats. Genetic variation in the ancestral species made it possible for natural selection to favor certain genotypes for survival in new habitats. Eventually these subpopulations became genetically isolated and genetically more divergent than their parental or sibling subpopulations, i.e. evolution.

biotic:

living

abiotic:

non-living

speciation:

the formation of new and distinct species in the course of evolution.

Microevolution:

the study of how evolution works at the genetic level. We do this by computing the relative frequency of alleles in the gene pool of a population through succeeding generations.

A classic example of microevolution:

the study of the peppered moths and industrial melanism conducted by researchers in England just after the opening of the industrial revolution.