Chapter 12: Genetics and Evolution

Question 1

Shorthand for nucleotide

Answer 1

nt

Question 2

Shorthand for chromosome

Answer 2

Chr

Question 3

Shorthand for mutation

Answer 3

Mutat

Question 4

What are genes?

Answer 4

Genes are DNA sequences that code for heritable traits that can be passed from one generation to the next.

Question 5

What is a chromosome?

Answer 5

A chromosome is a thread-like structure found inside the nucleus of a cell that carries long strands of DNA, containing the genetic information needed for an organism to function, essentially acting as the “blueprint” for an organism’s traits and development.

Question 6

What are alternate forms of genes called?

Answer 6

Alternate forms of genes are called alleles.

Question 7

What is a genotype?

Answer 7

A genotype is the genetic combination possessed by an individual.

Question 8

What is a phenotype?

Answer 8

A phenotype is the observable manifestation of a given genotype.

Question 9

What are homologous chromosomes? What is the exception of homologous in humans? Are homologous chromosomes identical?

Answer 9

Homologous chromosomes are two copies of each chromosome. The exception of homologous in humans are the sex chromosomes of genotypical males who have one X chromosome and one Y chromosome.

Remember. Homologous chromosomes are not identical to each other. They carry the same genes in the same order but contain different alleles.

Question 10

What is the locus of a gene?

Answer 10

The locus of a gene is the location of a gene on a specific chromosome.

Question 11

Explain dominant and recessive alleles.

Answer 11

Alleles are considered dominant if only one copy is necessary to express a given phenotype.

Alleles are considered recessive if two copies are needed to express a given phenotype.

Question 12

What is a homozygous genotype? Heterozygous? Hemizygous?

Answer 12

A homozygous genotype is when both alleles are the same for a given gene. Simple example being RR (homozygous dominant) or rr (homozygous recessive).

Heterozygous is the alleles are different. Such as Rr.

Hemizygous are a situation in which only one allele is present for a given gene. Such as one X chromosome for genotypical males.

Question 13

What is complete dominance regarding alleles? Codominance? Incomplete dominance?

Answer 13

Complete dominance is there is only one dominant and one recessive allele existing for a given gene.

Codominance is when more than one dominant ellese exist for a gene, for example blood: A and B are codominant in that both A and B antigens will be expressed if both dominant alleles are present on the gene.

Incomplete dominance occurs when a heterozygote expresses a phenotype that is intermediate between the two homozygous genotype. Example is certain kinds of flowers. RR is red, rr is white, Rr is pink. Memorize the F1 and F2 outcome of the following image:

Question 14

What is penetrance and expressivity?

Answer 14

Penetrance is the proportion of a population with a given genotype who actually express the phenotype.

Expressivity is the different manifestation of the same genotype across the population.

Hypothetical mouse ear example:

Question 15

List the varying degrees of penetrance.

Answer 15

Penetrance varies in a population from full penetrance to nonpenetrance:

Full penetrance: 100% of the individuals in a population express.
High penetrance: most express.
Reduced penetrance.
Low penetrance.
Nonpenetrance: no expression.

Question 16

How does expressivity differ from penetrance?

Answer 16

Expressivity is the varying manifested phenotype for a given genotype. Penetrance is the percentage of the population that express a manifested phenotype for a given genotype.

Question 17

What is the main takeaway from Mendel’s law of segregation?

Answer 17

The key takeaway from Mendel’s law of segregation is the separation of homologous chromosomes during anaphase I of meiosis segregate the chromosomes into different cells, making each gamete having only one allele for any given trait.

Question 18

What is the takeaway from Mendel’s second law: independent assortment.

Answer 18

The takeaway from Mendel’s second law is that the inheritance is one gene does not affect the inheritance of another gene. Under genome replication during meiosis, during prophase I chromosomes will recombine allowing for inheritance that is independent of the others. Recall crossing over of homologous chromosomes effectively swapping genetic material and becoming unique among themselves.

Segregation and independent assortment of alleles allow for greater genetic diversity in the offspring.

Question 19

Describe transcription and translation.

Answer 19

Transcription is the creation of mRNA from DNA. Translation is the creation of a protein from mRNA.

Question 20

Recall transformation, transduction, and conjugation of bacteria.

Answer 20

Transformation is when a bacteria picks up genetic material, and thus genes, from its environment.

Transduction is when a bacteria inherits genetic information, and thus genes, from a vector such as a bacteriophage.

Conjugation is bacteria sex. lol. A sex factor must be present for bacteria to perform conjugation.

Question 21

What are epigenetics? What does the word mean? What are some types and examples of epigenetics? Are there clinical impacts of epigenetics? What is imprinting?

Answer 21

Epigenetics is a general term for changes in DNA that do not involve an alteration to the nucleotide sequence. The prefix epi- means “over” or “above”, so genetic changes that come from sources other than changed nucleotide sequence.

Examples include covalent attachment of different chemical groups to nucleotides or histone proteins including methylation and acetylation. These modifications can increase or decrease the expression of specific genes.

Another example is X-inactivation in cells with two X chromosomes in which one of the X chromosomes is silenced via methylation. The inactive X is called a Barr body.

Clinical impacts include hypermethylation of oncogenes and tumor suppressor genes have been implicated in some forms of cancer.

Imprinting is an epigenetic process in which gene expression is determined by the contributing parent. Differentiated methylation can come from a parent.

Question 22

What is imprinting? What is the book example of imprinting?

Answer 22

Imprinting is an epigenetics process in which gene expression is determined by the contributing parent.

Prader-Willi syndrome: development disorder caused by a deletion in chromosome 15. If the deletion of the region of the chromosome occurs on the paternal chromosome and the maternal copy is heavily methylated.

A totally different outcome happens when the maternal chromosome portion of chromosome 15 is missing and the paternal chromosome is heavily methylated: Angleman syndrome

Question 23

What is a mutation? What are wild type alleles? What are mutant alleles? Mutations can happen in a number of ways, name some.

Answer 23

A mutation is a change in DNA sequence and it results in a mutant allele. Mutant alleles are those that have been changed via a mutation. Wild type alleles are those considered normal or natural and are ubiquitous in the study population.

Mutations can be caused by ionizing radiation and chemical exposures (mutagens). DNA polymerase can make occasional errors. Transposons can insert and remove themselves from the genome.

Question 24

What is a mutagen?

Answer 24

A mutagen is a substance that can cause mutations.

Question 25

How can transposons cause mutations?

Answer 25

Transposons can insert or delete the moves from the genome. If a transposons inserts in the middle of a coding sequence, the mutation could disrupt the gene.

Question 26

What is a nucleotide level mutation? What are the three point mutations?

Answer 26

A nucleotide level mutation occur at the level of a single nucleotide. The three types of nucleotide level mutations are: Silent mutation. Change in nucleotide has no effect on the final protein synthesized from the gene. This often happens when the changed nucleotide is transcribed is the third nucleotide in a codon because of degeneracy (wobble) in the code. Missense mutation. Change in nucleotide results in substituting an amino acid in the final protein. Nonsense mutation. Change in the nucleotide results in substituting a stop codon for an amino acid in the final protein.

Question 27

What is a frameshift mutation? What is a codon? Reading frame?

Answer 27

Frameshift mutations occur when nucleotides are inserted into or deleted from the genome, causing a shift in the reading frame which usually results in either changes in amino acid sequence or premature truncation of the protein (due to generation of a nonsense mutation). Categorized in insertion or deletion mutations. This happens because mRNA is transcribed from DNA using three letter sequences called codons and the translation of mRNA is directional.

Question 28

What is a chromosomal mutation? What are the five common types of chromosomal mutations.

Answer 28

A chromosomal mutation is a larger scale mutation in which large segments of DNA are affected. Deletion chromosome mutation: section of chromosome is deleted. Duplication chromosome mutation: section of chromosome is duplicated in same chromosome. Inversion chromosome mutation: a section is inverted in same chromosome. Insertion chromosome mutation: segment of DNA is moved from one chromosome to another. Considered frameshift mutations. Translocation chromosome mutation: occurs when a segment of DNA from one chromosome is swapped with a segment of DNA from another chromosome.

Question 29

Give an example of advantageous and deleterious mutation. What are inborn errors of metabolism?

Answer 29

An example of an advantageous mutation would be sickle cell disease, a single nucleotide mutation that caused sickle shaped hemoglobin. Heterozygotes for this disease are resistant to malaria as it shortens the lifespan of red blood cells, just short enough for the parasitic Plasmodium cannot reproduce in red blood cells. An example of deleterious mutation would be XENODERMA PIGMENTOSUM (XP) which is an inherited defect in the nucleotide excision repair mechanism. DNA damage caused by ionizing radiation (UV) cannot be repaired. Patients with XP are frequently diagnosed with malignancies, especially of the skin. Inborn errors of metabolism are a class of deleterious mutations, specifically in genes required for metabolism. PHENYLKETONURIA as an example.

Question 30

What is nucleotide excision repair? What disease impacts NER?

Answer 30

Nucleotide excision repair (NER) is a DNA repair mechanism that removes bulky DNA caused by environmental factors such as ionizing radiation and chemicals. Lack of NER can cause xeroderma pigmentosum, among other things, which prevents repair of DNA from repairing itself causing malignancies of the skin.

Question 31

What is phenylketonuria? What consequence of mutation is it an example of?

Answer 31

PKU is a disease where phenylalanine hydrolase is defective. This prevents complete metabolism of phenylalanine which causes toxic metabolites to build up causing seizures, learning disabilities, and impairment of cerebral function. PKU is an example of inborn errors of metabolism, a deleterious mutation.

Question 32

What is genetic leakage? Example?

Answer 32

Genetic leakage is a flow of genes between species. Hybrids can be formed in some cases such as mules and beefalo. Mules cannot reproduce, but beefalo (cattle x bison) can reproduce as their parents have the same number of chromosomes (60).

Question 33

What is genetic drift? How does the founder effect correlate with genetic drift? What is the ultimate result of inbreeding, genetic drift, and the founder effect?

Answer 33

Genetic drift refers to the changes in composition of the gene pool because of chance, more pronounced in small populations. The founder effect is an extreme case of genetic drift where small populations of a species find itself in reproductive isolation due to environmental barriers, catastrophic events, or bottlenecks (an event that drastically and suddenly reduce the size of the population available for breeding). The ultimate result of genetic drift, the founder effect, and inbreeding, is a reduction of genetic diversity by encouraging homozygous dominant and recessive genotypes.

Question 34

What is maple syrup urine disease?

Answer 34

Branched chain ketoacid dehydrogenase deficiency affects the metabolism of branched chain AA. Common in Mennonite communities, implying a common origin of the mutation due to a small population experiencing inbreeding.

Question 35

What is inbreeding depression? What is outbreeding?

Answer 35

Inbreeding depression is the reduced fitness of a population due to loss of genetic variation. Outbreeding, or outcrossing, is the introduction of unrelated individuals into a breeding group which can theoretically result in increased genetic variation and increase the fitness of a population.

Question 36

Why would genetic leakage in animals be rare prior to the last century?

Answer 36

With advances in technology we can better understand the fertility factors of hybrid species.

Question 37

Why is genetic drift more common in small populations? What relationship does this have with the founder effect?

Answer 37

Genetic drift occurs due to chance so its effects will be more pronounced with a smaller sample size. The founder effect occurs when a small group becomes reproductively isolated from a larger population allowing certain alleles to take on a higher prevalence in the group than in the rest of the population.

Question 38

What are the six analytical approaches in genetics presented in the book?

Answer 38

Monohybrid crosses Test crosses Dihybrid crosses Sex linked crosses Gene Mapping Hardy Weinberg Principle

Question 39

What is a monohybrid cross? Provide an example.

Answer 39

A monohybrid cross is a cross analysis where only one trait is being studied. Parent generation is P, Filial generation (offspring) is F1, F2, F3, etc. Mendel’s pea plants, purple (P) white (p)

Question 40

A) What is the genotypic and phentotypic result from the monohybrid cross of homozygous dominant (PP) and homozygous recessive (pp)? B) Heterozygous monohybrid cross?

Answer 40

A) The result would be 100% heterozygous dominant and 100% phenotype expressing dominant. B) The result would be 1:2:1 homozygous dominant: heterozygous: homozygous recessive genotype, 3:1 phenotypic dominant: phenotypic recessive.

Question 41

What is the genotypic and phenotypic result of crossover of two heterozygotes for a trait with complete dominance? Definitely want to know this handily.

Answer 41

The genotypic result would be 1:2:1 (PP:Pp:pp) The phenotypic result would be 3:1 (dominant:recessive). Keep in mind that these ratios are theoretical probabilities and will not always hold true especially for small populations. More offspring means closer to theoretic ratios.

Question 42

What is a test cross? What is another term for test cross and why is it called that?

Answer 42

A test cross is used to determine an unknown genotypes through deduction by crossing with a known genotype. ***The unknown genotype will be crossed with homozygous recessive. Test crosses are known as back crosses because the parent generation is determined by the filial generation. Monocross example: If the unknown was PP (homozygous dominant) then the filial generation (F1) will be 100% genotypic heterozygous dominant and 100% phenotypically dominant. If the unknown was Pp (heterozygous), then the filial generation (F1) will be 1:1 heterozygous:homozygous recessive, and 1:1 phenotypically dominant:recessive.

Question 43

What is a dihybrid cross? What kind of linkage are dihybrid crosses specifically useful for?

Answer 43

A dihybrid cross is extending a Punnett square for inheritance of two different genes. This creates a 4x4 Punnett square. This works well for UNLINKED GENES. In order to work a dihybrid cross, you need to separate the genome into gametes. For example: DdGg gametes (4) would be: DG, Dg, dG, dg for the purposes of the calculation approximating the filial generation. Example: P purple, p white, T tall, t short.

Question 44

What is the expected phenotypic result of a dihybrid cross of two parents that are heterozygous for both traits? Is that associated with another ratio? Definitely need to know this. TtPp P purple p white T tall t short

Answer 44

This would be PpTt x PpTt The result would be 9:3:3:1 phenotypic ratio (purpletall:purpleshort:whitetall:whiteshort) The 3:1 phenotypic ratio holds for each individual trait: 12 tall : 4 short 12 purple : 4 white

Question 45

What does sex linked mean? What assumption could be made about sex linked traits? Do Y linked diseases exist?

Answer 45

Sex linked means X linked. It is fair to make the assumption that sex linked traits are recessive unless otherwise specified. Y linked diseases exist but are exceedingly rare.

Question 46

What is a Y linked disease? Do dominant and recessive concept apply?

Answer 46

Y linked diseases are passed from father to son and dominant recessive concepts do not apply as there is only one Y chromosome in genotypical male.

Question 47

What are sex linked crosses?

Answer 47

Sex linked crosses are crosses that help determine x linked traits. Slightly different system is used to symbolize but the crossing strategy is still the same. Xh is typically used for the allele with the trait in question, usually a recessive defective allele. Heterozygote females are considered carriers.

Question 48

Regarding hemophilia as an example of x linked traits, what would be the outcome of a cross between a carrier female and normal male? Cross between carrier female and hemophiliac male?

Answer 48

Cross of carrier female and normal male: 25% carrier female 25% normal female 25% carrier male 25% normal male Cross of carrier female and hemophiliac male: 25% hemophiliac female 25% hemophiliac male 25% carrier female 25% normal male

Question 49

What is gene mapping? Recombination frequency? Genetic map? Map unit (centimorgan)?

Answer 49

Gene mapping is a tool used to determine proximity of genes on a chromosome. Recombination frequency is the likelihood that two alleles are separated during crossover (higher frequency is higher likelihood of alleles being separated). Recombination frequency is roughly proportional to the distance between genes. A genetic map represents the relative distance between genes on a chromosome. One map unit or centimorgan corresponds to 1% chance of recombination occurring between two genes. Recombination frequencies can be added to approximate the order of genes in a chromosome.

Question 50

What is the Hardy Weinberg Principle (HWP) and what are the five criteria mandatory for the Hardy Weinberg Equilibrium (HWE)? What are the equations?

Answer 50

The HWP relies on allele frequency not changing and is a tool used to determine the allele frequency of a population. The five things for HWE to occur are: Very large population (no genetic drift) No mutations that affect the gene pool Mating between indiv is random (no sexual selection) No migration of indiv in or out Genes in population are equally successful at being reproduced. p = frequency of dominant allele q = frequency of recessive allele psquared = frequency of homozygous dom qsquared = frequency of homozygous rec 2pq = frequency of heterozygous p+q=1 psquared+2pq+qsquared=1 All you need to solve any MCAT HWE is the value of p (or psquared) or q (or qsquared).

Question 51

What are the two Hardy Weinberg Equations?

Answer 51

p = frequency of dominant allele q = frequency of recessive allele psquared = frequency of homozygous dom qsquared = frequency of homozygous rec p + q = 1 psquared + 2pq + qsquared = 1 psquared + 2pq = frequency of dominant phenotype All you need to solve any MCAT HWE is the value of p (or psquared) or q (or qsquared).

Question 52

Describe the outcome of a crossing of alleles T and t with p=0.8 q=0.2 Find psquared, 2pq, and qsquared using both a Punnett square and the HWE.

Answer 52

Where p=frequency of T q=frequency of t 2pq=frequency of heterozygous dominant genotype qq=frequency of homozygous dominant pp=frequency of homozygous recessive pp+2pq=frequency of dominant phenotype psquared = .8x.8= .64 qsquared = .2x.2= .04 2pq = 2(.8)(.2)= .32 All equals 1, checks out. Interestingly, the final filial generation still follows the allele frequency prior to the cross: 64% TT = 64%T and 0% t 32% Tt = 16%T and 16% t 4% tt = 0% T and 4% t 80%T and 20%t

Question 53

What two peices of information can be found with HWE?

Answer 53

The relative frequency of alleles in a population. The frequency of a given genotype or phenotype in the population. REMEMBER: there will be twice as many alleles as individuals in a population because each individual has two autosomal copies of each gene.

Question 54

Punnett square questions

Answer 54

Question 55

Assume HWE and 9% of population is homozygous dominant. Solve for Frequency of dominant allele. Frequency of recessive allele. Proportion of population that is heterozygous. Proportion of population with a homozygous recessive genotype. The portion of the population with a dominant phenotype.

Answer 55

Frequency of dominant allele = p Frequency of recessive allele = q Proportion of population that is heterozygous = 2pq Proportion of population with a homozygous recessive genotype = qq The portion of the population with a dominant phenotype = pp+2pq

Question 56

What is natural selection. Is evolution natural selection?

Answer 56

Natural selection, survival of the fittest, is a theory that certain characteristics or traits possessed by individuals within a species may help those individuals have greater reproductive success. Natural selection is not evolution. Natural selection is a mechanism of evolution.

Question 57

What are the basic tenets of Charles Darwin publication on the origin of species?

Answer 57

Organisms produced offspring, few of which survive to reproductive maturity. Variations within an individuals in a population may be heritable. If these variations give an organism even a slight survival advantage, the variation is termed favorable. Individuals with greater preponderance of these favorable variations are more likely to survive to reproductive age and produce offspring. The overall result will be an increase in these traits and future generations. This level of reproductive success is termed fitness, an organisms fitness is directly related to the relative genetic contribution of this individual to the next generation.

Question 58

What does the term fitness mean evolutionarily?

Answer 58

Fitnesses is reproductive success based on favorable variations and likeliness to survive to reproduce.

Question 59

What is the modern synthesis model?

Answer 59

The modern synthesis model adds knowledge of genetic inheritance and changes in the gene pool to Darwin’s original theory. Mutation or recombination results in a change that is favorable to the organisms reproductive success, that change is more likely to pass onto the next generation. The modern synthesis model combines natural selection, Mendelian inheritance, and genetic variation.

Question 60

What is differential reproduction?

Answer 60

Differential reproduction says that overtime those traits passed on by more successful organisms will become ubiquitous in the gene pool.

Question 61

What is inclusive fitness?

Answer 61

Inclusive fitness is a measure of an organism success in the population based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others. Inclusive fitness is a contemporary theory that taken into the benefits of certain behaviors on the population at large.

Question 62

What is punctuated equilibrium? What is a good example of punctuated equilibrium?

Answer 62

Punctuated equilibrium suggests that changes in some species occur in rapid bursts rather than evenly over time. Punctuated equilibrium is a result of research into the fossil record. It was discovered that little evolution would occur within a lineage of related life forms for long periods of time, followed by an explosion in evolutionary change.

Question 63

What are three modes of natural selection?

Answer 63

The three modes of natural selection are stabilizing selection, directional, selection, and disruptive selection. Stabilizing selection keeps phenotypes within a specific range by selecting against extremes. Human fetal birthweight is an example of stabilizing selection. Directional selection is the emergence and dominance of an initially extreme phenotype. An example would be bacterial resistance to antibiotics. Disruptive selection is where two extreme phenotypes are selected over the norm. An example would be Darwin’s finches, which were not observed to have a “ normal beak size.

Question 64

What is a polymorphism, and how is it related to disruptive selection?

Answer 64

Polymorphisms are naturally occurring differences and form between members of the same population. Disruptive selection is facilitated by the existence of polymorphisms.

Question 65

What is adaptive radiation?

Answer 65

Adaptive radiation describes the rapid rise of a number of different species from a common ancestor allowing for various species to occupy different niches. Adaptive radiation is an evolutionary process where a single ancestral species rapidly diversifies into many new species, each with distinct adaptations that allow them to occupy different ecological niches within a given environment, often triggered by a change in the environment that opens up new resource opportunities; essentially, a rapid burst of evolution from a common ancestor leading to a variety of specialized forms within a lineage.

Question 66

What is a niche?

Answer 66

A niche is a specific environment including habitat, available resources, and predators, for which of species is specifically adapted.

Question 67

What is a species defined as?

Answer 67

The species is defined as the largest group of organisms capable of breeding to form fertile offspring.

Question 68

What is speciation?

Answer 68

Speciation is the formation of a new species through evolution.

Question 69

What is isolation regarding speciation?

Answer 69

If we took two populations from the same species and separating them geographically for a long period of time, different evolutionary pressures would lead to different adaptive changes. If enough time passed, the changes would be sufficient to lead to isolation, which means the progeny of these populations could no longer freely interbreed.

Question 70

What are the two mechanisms of reproductive isolation? What do they mean?

Answer 70

Prezygotic and postzygotic mechanisms. Prezygotic mechanisms prevent formation of the zygote completely. Postzygotic mechanisms allow for fusion, but yield either non-viable or sterile offspring.

Question 71

What are some examples of prezygotic mechanisms of isolation?

Answer 71

Temporal isolation (breeding at different times) Ecological isolation (living in different niches within the same territory) Behavioral isolation (lack of attraction between members of the two species due to differences in pheromones, courtship displays, and so on) Reproductive isolation (in compatibility of reproductive anatomy) Gametic isolation (Intercourse can occur, but fertilization cannot)

Question 72

What are some examples of postzygotic mechanisms of isolation?

Answer 72

Some examples of postzygotic mechanisms of speciation are: Hybrid inviability (formation of a zygote that cannot develop to term) Hybrid sterility (formation of a hybrid offspring that cannot reproduce) Hybrid breakdown (forming first generation hybrid offspring that are viable and fertile, but second generation hybrid offspring that are inviable or infertile)

Question 73

What are the three patterns of evolution?

Answer 73

The three patterns of evolution are divergent evolution, parallel evolution, and convergent evolution.

Question 74

What is divergent evolution?

Answer 74

Divergent evolution refers to the independent development of dissimilar characteristics in two or more lineages sharing a common ancestor. Example would be seals and cats. They are both mammals in the order Carnivora, yet they differ in general appearance. These two species live in a very different environment and adapted to different selection pressures while evolving.

Question 75

What is parallel evolution?

Answer 75

Parallel evolution refers to the process where by related species evolve in similar ways for a long period of time in response to analogous environmental selection pressures. A good example would be the woolly mammoth and the common elephant. The woolly mammoth went extinct 4000 years ago, but look markedly similar to the modern common elephant. Another example would be all the many marsupials in Australia

Question 76

What is convergent evolution?

Answer 76

Convergent evolution refers to the independent development of similar characteristics and two or more lineages not sharing a recent common ancestor. Fish and dolphins have come to resemble one another physically, though they belong to different classes of vertebrates. They evolved certain similar features and adapting to the conditions of aquatic life.

Question 77

What is the molecular clock model?

Answer 77

The molecular clock model is the correlation of the degree of genomic similarity with the amount of time since the two species split off from the same common ancestor. The more similar the genome, the more recent the two species separated from one another.

Question 78

What are the key tenets of natural selection?

Answer 78

Natural selection states that certain traits that arise from chance are more favorable for reproductive success in a given environment, and then those traits will be passed on to future generations.

Question 79

What are the key tenets of the modern synthesis model?

Answer 79

The modern synthesis model takes natural selection and explains that selection is for specific alleles, which are passed on to future generations through formation of gametes. The alleles for these favorable traits arise from mutation.

Question 80

What are the key tenets of inclusive fitness?

Answer 80

Inclusive fitness explains that the reproductive success of an organism is not only due to the number of offspring it creates, but also the ability to care for young. It explains change is not only at the individual level, but change based on the survival of the species.

Question 81

What are the key tenets of punctuated equilibrium?

Answer 81

Punctuated equilibrium states that for some species, little evolution occurs for a long period, which is interrupted by rapid bursts of evolutionary change.