˗ˏˋ evolution forces ´ˎ˗

Question 1

what is the universal ancestor?

Answer 1

the first living organism, from which all living things are descended.

Question 2

what are phylogenies?

Answer 2

genetically determined family lineages.

Question 3

what are the origins of life?

Answer 3

how the first living organism came into being.

Question 4

what is the phylogenetic tree of life?

Answer 4

a family tree of all living organisms, based on genetic relationships.

Question 5

what is lamarckian inheritance?

Answer 5

• an idea that offspring inherit any traits their parents picked up during their lifetimes.
• the giraffes.

Question 6

what is pangenesis?

Answer 6

• promoted by darwin.
• an early model for inheritance that combines the lamarckian idea of inheriting acquired characteristics with the idea that particles from different parts of the body make their way to the sex cells.

Question 7

what is the law of use & disuse?

Answer 7

lamarckian idea, supported by darwin, that limbs or organs not used during an organism’s lifetime, would disappear off their offspring.

Question 8

who is august weismann?

Answer 8

• in 1892 attempted to prove whether or not offspring inherited acquired characteristics.
• cut tails on mice, bred them, but their offspring still had tails.

Question 9

what is modern synthesis?

Answer 9

the integration of darwin’s, mendel’s, and subsequent research into a unified theory of evolution.

Question 10

what are polymorphisms?

Answer 10

multiple forms of a trait; alternative phenotypes within a given species.

Question 11

what is a population?

Answer 11

a group of individuals of the same species who are geographically near enough to one another that they can breed and produce new generations of individuals.

Question 12

what is the simple definition of evolution?

Answer 12

a change in the allele frequencies in a population over time.

Question 13

what are allele frequencies?

Answer 13

ratio, or percentage, of one allele (one variant of a gene) compared to the other alleles for that gene within the study population.

Question 14

what are genotype frequencies?

Answer 14

ratios or percentages of the different homozygous and heterozygous genotypes in the population.

Question 15

what are mutationists?

Answer 15

group of early biological scientists who believed that variation was caused by mutations in distinct, inherited cells.

Question 16

what are biometricians?

Answer 16

group of early biological scientists who believed that individual mutations of discrete hereditary units could never account for the continuous spectrum of variation seen in many traits.

Question 17

who revealed the existence of chromosomes?

Answer 17

wright and dobzhansky.

Question 18

what must occur for two organisms to be of the same species?

Answer 18

• viable offspring: offspring that are healthy enough to survive to adulthood.
• fertile offspring: offspring that can reproduce successfully to have offspring of their own.

Question 19

what is a subspecies?

Answer 19

• a distinct subtype of a species.
• geographically isolated population with unique phenotypes; however, it remains biologically and behaviorally capable of interbreeding with other populations of the same species.

Question 20

what does evolution require?

Answer 20

• population of breeding individuals.
• some kind of a genetic change.

Question 21

what are the four forces of evolution?

Answer 21

• mutations
• genetic drift
• gene flow
• natural selection

Question 22

what is a mutation?

Answer 22

• changes in genetic code.
• original source of all the genetic variation found in every living thing.

Question 23

what is a deleterious mutation?

Answer 23

mutation producing negative effects to the individual such as the beginnings of cancers or heritable disorders.

Question 24

what is a beneficial mutation?

Answer 24

mutations that produce some sort of an advantage to the individual.

Question 25

what is a spontaneous mutation?

Answer 25

• a mutation that occurs due to random chance or unintentional exposure to mutagens.
• in families, it is the first case, as opposed to mutations that are inherited from parents.

Question 26

what is an inherited mutation?

Answer 26

a mutation that has been passed from parent to offspring.

Question 27

what is UV crosslinking?

Answer 27

a type of mutation in which adjacent thymine bases bind to one another in the presence of UV light.

Question 28

what are DNA repair mechanisms?

Answer 28

enzymes that patrol and repair DNA in living cells.

Question 29

what is an autosomal recessive disease?

Answer 29

a phenotype produced by a gene on an autosomal chromosome that is expressed only in individuals homozygous for the recessive allele.

Question 30

what is xeroderma pigmentosum?

Answer 30

an autosomal recessive disease in which DNA repair mechanisms do not function correctly, resulting in a host of problems especially related to sun exposure, including severe sunburns, dry skin, heavy freckling, and other pigment changes.

Question 31

what is a point mutation?

Answer 31

a single-letter (single-nucleotide) change in the genetic code, resulting in the substitution of one nucleic acid base for a different one.

Question 32

what is a synonymous mutation?

Answer 32

a point mutation that does not change the resulting protein.

Question 33

what is a nonsynonymous mutation?

Answer 33

a point mutation that causes a change in the resulting protein.

Question 34

what are insertions?

Answer 34

mutations that involve the addition of one or more nucleotides into a DNA sequence.

Question 35

what are deletions?

Answer 35

mutations that involve the removal of one or more nucleotides from a DNA sequence.

Question 36

what are transposable elements?

Answer 36

fragments of DNA that can “jump” around in the genome.

Question 37

what are indels?

Answer 37

short for insertions and deletions.

Question 38

what are frameshift mutations?

Answer 38

• types of indels that involve the insertion or deletion of any number of nucleotides that is not a multiple of three.
• these “shift the reading frame” and cause all codons beyond the mutation to be misread.

Question 39

what are retrotransposons?

Answer 39

transposons that are transcribed from DNA into RNA, and then are “reverse transcribed,” to insert the copied sequence into a new location in the DNA.

Question 40

what are DNA transposons?

Answer 40

transposons that are clipped out of the DNA sequence itself and inserted elsewhere in the genome.

Question 41

what are crossover events?

Answer 41

chromosomal alterations that occur when DNA is swapped between homologous chromosomes while thy are paired up during meiosis I.

Question 42

what are nondisjunction events?

Answer 42

chromosomal abnormalities that occur when the homologous chromosomes (in meiosis I) or sister chromatids (in meiosis II and mitosis) fail to separate after pairing.
- result is that both chromosomes or chromatids end up in the same daughter cell, leaving the other daughter cell without any copy of that chromosome.

Question 43

what are chromosomal translocations?

Answer 43

the transfer of DNA between non-homologous chromosomes.

Question 44

what is neurofbromatosis type 1 (NF1)?

Answer 44

• an autosomal dominant genetic disorder affecting one in every 3,000 people.
• caused by mutation of the NF1 gene on chromosome 17, resulting in a defective neurofibromin protein.
• characterized by neurofibromas, café-au-lait spots, and a host of other potential symptoms.

Question 45

what is genetic drift?

Answer 45

random changes in allele frequencies within a population from one generation to the next.

Question 46

what is asexual reproduction?

Answer 46

reproduction via mitosis, whereby offspring are clones of the parents.

Question 47

what is sexual reproduction?

Answer 47

• reproduction via meiosis and combination of gametes.
• offspring inherit genetic material from both parents.

Question 48

what is ellis-van creveld syndrome?

Answer 48

• an autosomal recessive disorder characterized by short stature (dwarfism), polydactyl (development of more than five digits), abnormal tooth development, and heart defects.
• affects approx 60,000 individuals worldwide.
• rate among lancaster amish population is more like 1 in every 200 births.

Question 49

what is gene flow?

Answer 49

• the movement of alleles from one population to another.
• admixture in humans.
• hybridization in non-human populations.

Question 50

what is natural selection?

Answer 50

an evolutionary process that occurs when certain phenotypes confer an advantage or disadvantage in survival and/or reproductive success.

Question 51

what is directional selection?

Answer 51

a pattern of natural selection in which one phenotype is favored over the other, causing the frequencies of the associated advantageous alleles to gradually increase.

Question 52

what is balancing selection?

Answer 52

a pattern of natural selection that occurs when the extremes of a trait are selected against, favoring the intermediate phenotype (aka stabilizing selection).

Question 53

what is disruptive selection?

Answer 53

a pattern of natural selection that occurs when both extremes of a trait are advantageous and intermediate phenotypes are selected against (aka diversifying selection).

Question 54

what is sickle cell anemia?

Answer 54

• an autosomal recessive genetic disorder that affects millions of people worldwide.
• most common in africa, countries around the mediterranean sea, and eastward as far as india.
• homozygotes for the recessive develop the disorder, which produce misshapen red blood cells that cause iron deficiency, painful episodes of oxygen-deprivation in localized tissues, and a host of other symptoms.
• sickle cell allele confers a greater resistance to malaria.

Question 55

what is sexual selection?

Answer 55

an aspect of natural selection in which the selective pressure specifically affects reproductive success (the ability to successfully breed and raise offspring).

Question 56

what is the hardy-weinberg equilibrium?

Answer 56

• mathematical formula that allows estimation of the number and distribution of dominant and recessive alleles in a population.
• only gives us an estimate based on the data for a snapshot in time.

Question 57

what is microevolution?

Answer 57

changes in allele frequencies within breeding populations – that is, within a single species.

Question 58

what is marcoevolution?

Answer 58

changes that result in the emergence of new species, the similarities and differences between species, and their phylogenetic relationships with other taxa.

Question 59

what is speciation?

Answer 59

• the process by which a single population divides into two or more separate species.
• two types: allopatric and sympatric.

Question 60

what is allopatric speciation?

Answer 60

speciation caused by long-term isolation (physical separation) of subgroups of the population.

Question 61

what is sympatric speciation?

Answer 61

when a population splits into two or more separate species while remaining located together without a physical (or cultural) barrier.

Question 62

what is adaptive radiation?

Answer 62

the situation in which subgroups of a single species rapidly diversify and adapt to fill a variety of ecological niches.

Question 63

what is an ecological niche?

Answer 63

a set of constraints and resources that are available in an environmental setting.

Question 64

what is positive assortative mating?

Answer 64

a pattern that results from a tendency for individuals to mate with others who share similar phenotypes.

Question 65

what is negative assortative mating?

Answer 65

a pattern that occurs when individuals tend to select mates with qualities different from their own.