Biol Unit 3 Review

Explain how radiometric dating can be used to determine the absolute age of rock strata.

-A "parent" isotope decays to a "daughter" isotope at a constant rate. Each isotope has a known half-life, the time required for half the parent isotope to decay. -All living organisms have Carbon 14. The most common isotope in nature is Carbon 12. Whenever we die, carbon 12 decreases, but the ratio of carbon 12 to carbon 14 stays the same. As time passes, proportion of carbon 14 decays and becomes another element.

Define evolution and adaptation.

-Adaptation: Inherited characteristics of organisms that enhance their survival and reproduction in specific environments. -Process helps organisms match to the environment where they're at.-(Natural selection increases the adaptation of organisms to their environment over time) -Evolution: organisms that possess heritable traits that enable them to better adapt to their environment compared with other members of their species will be more likely to survive, reproduce, and pass more of their genes on to the next generation. -Long term changes in genetic frequency -(if an environment changes over time, natural selection may result in adaptation to those new conditions and may give rise to new species)

Define adaptive radiation. Describe, with suitable examples, three circumstances under which adaptive radiation may occur.

-Adaptive Radiation: Is the evolution of diversely adapted species from a common ancestor. -3 Circumstances Adaptive Radiations may follow: 1.) Mass extinctions -Adaptive radiation events occurs after mass extinction. Where remaining living organisms repopulate and over time speciate by adapting to new environments and create new species. 2.) The evolution of novel characteristics 3.) The colonization of new regions (Adapting to new environments (Speciation)) -Not necessarily worldwide, can be regional such as the Finches on the Galapagos Islands. Their beak side and length range according to the different fruits that grow on the different islands. All species have same common ancestor from when all islands were together.

Describe how natural selection favors the evolution of drug-resistant pathogens.

-Bacteria that is resistant to antibiotic remains alive while those without resistance die. Now, the ones that are resistant will reproduce and there will be a new population of bacteria that are resistant to that antibiotic. -There were already one or 2 cells that had a mutation that allowed them to survive the penicillin. Now there's a population that's resistant to penicillin

State the evidence that suggests that the common ancestor of multicellular eukaryotes lived 1.5 billion years ago.

-Based on comparisons of DNA sequences the common ancestors of multicellular eukaryotes lived 1.5 billion years ago.

Explain the following characteristics of the Linnaean system of classification: a. Binomial nomenclature b. Hierarchical classification.

-Binomial Nomenclature: two-part names for species. The first part of the name is the genus, the second part, called the specific epithet, is unique for each species within the genus. The first letter of the genus is capitalized, and the entire species name is italicized. Both parts together name the species (not the specific epithet alone) -Hierarchical Classification: A system for grouping species in increasingly broad categories. Taxonomic groups from narrow to broad are: species, genus, family, order, class, phylum, kingdom, and domain. A taxonomic unit at any level of the hierarchy is called a taxon. Broader taxa not comparable between lineages.

Explain how evidence from biogeography supports the theory of evolution by natural selection.

-Biogeography: the geographic distribution of species, provides evidence of evolution. -Darwin explained that species on islands gave rise to new species as they adapted to new environments -it shows that organisms had the same origin, but adapted to their particular surroundings. -An example of how it supports natural selectin would be islands generally have many species of plants and animals that are found no where else in the world. But Darwin showed how most island species are closely related to the species of the nearest mainland or neighboring island. The species on the island are just an altered species that were on the mainland, just altered for island enviorment. This also explains how two islands in opposite ends of the world with the same enviorment are inhabited b different species due to different mainland species.

Distinguish between the bottleneck effect and the founder effect. a. Describe how gene flow can act to reduce genetic differences between adjacent populations.

-Bottleneck effect: a sudden reduction in population size due to a change in the environment. Resulting gene pool may no longer reflect the original population's gene pool. (due to Genetic Drift) -Founder effect: Occurs when a few individuals become isolated from a larger population. (Looks at organisms moved from original habitat to start new population. That population moved to new environment not getting entire sample of entire gene pool.) All frequencies in the small founder population can be different from those in the larger parent population. (due to Genetic Drift) (Ex: Finches on Galapagos) -Gene flow: consists of the movement of alleles among populations. -Gene flow tends to reduce variation among populations over time b/c if extensive enough can blend neighboring populations into a single one with a common gene pool. -It reduces genetic differences between populations because they transfer allels to different populations in the next generation. For example if you have a wild flower population living next to a dominantly white flowered population, the gametes from the white flower population transfer to the next generation of the wild flowers therefore making them white cauing less genetic differences.

Define a clade. Distinguish between a monophyletic clade and paraphyletic and polyphyletic groupings of species.

-Clade: A group of species that includes an ancestral species and all its descendants. -Monophyletic clade: Where all come from a single ancestor -Paraphyletic clade: When all come from a single ancestor but does not include all species -Polyphyletic groupings of species: When it includes all of a species and one from another (that's different from the rest) -Monophyletic - Made up of an ancestral species and all of its descendants. -Polyphyletic - one that does not include the common ancestor of all members of the taxon -Paraphyletic - a group of organisms that includes an ancestor but not all of its descendants

Discuss, with a suitable example, how continental drift explains the current or former distribution of organisms. Explain how continental drift led to Australia's unique flora and fauna.

-Continental drift is the process where tectonic plates move slowly. -Continental drift can cause a continent's climate to change and Separation of landmass can lead to speciation. -When the plates separated, they broke off into several continents and took those animals with them. -Ex: Frog species in the subfamilies Mantellinae and Rhacophorinae began to diverge when Madagascar separated from india. Madagascar & India were close and when continental drift occurred, they took some of the frogs with them. The different climates in Madagascar v.s India caused them to adapt to different climates into new species (Adaptive Radiation). -Australia is the only continent with Marsupials. Australia is very separated from the rest of the continents on earth in climate and ecology. A continental drift separates every continent in various ways. Since Australia is so far from other pieces of land with such a different climate, the flora and fauna have had to adapt to widely different environmental challenges than the organisms around the rest of the world.

Describe how Darwin's observations on the voyage of the HMS Beagle led him to formulate and support his theory of evolution.

-Darwin observed that different types of animals had modifications that made them better suited to their environments. These observations led him to believe that all the animals had come from a common ancestor. -Darwin collected specimens from South American plants and animals -Observed that fossils resembled living species from the same region, and living species resembled other species from nearby regions. -Experienced an earthquake and observed the uplift of rocks -Interest in geographic distribution of species kindled by stop at Galapagos Islands. Hypothesized that species from South America had colonized the Galapagos and speciated on the islands.

Explain what evidence convinced Darwin that species change over time.

-Darwin was convinced that species changed over time after seeing population of finches on the Galapagos Islands.

Explain how diploidy can protect a rare recessive allele from elimination by natural selection.

-Diploidy maintains genetic variation in the form of hidden recessive alleles. Heterozygotes can carry recessive alleles that are hidden from the effects of selection.

Name the reactions that have produced O2 on Earth.

-Early prokaryotes released oxygen into the atmosphere through photosynthesis. -Most atmospheric oxygen is produced during the water splitting step of photosynthesis. The free o2 produced by photosynthesis dissolved in surrounding water and then reacting with dissolved iron. Causing the iron to precipitate as iron oxide which accumulated as sediments. All the dissolved iron precipitates and more free 02 dissolves into the water leaving the water saturated with o2. The o2 finally began to gas out of the water into the atmosphere. This whole process implies that life began to originate from this oxygen revolution.

Explain why evolutionary change is not goal-directed.

-Evolution doesn't happen at will. it is like tinkering, it is a process in which new forms arise by the slight modification of existing forms. By modification if what's already there. *Doesn't happen at will.

Explain the problem with the statement that Darwinism is "just a theory". a. Distinguish between the scientific and colloquial use of the word "theory".

-Evolution is supported by an overwhelming amount of scientific evidence. -The scientific meaning of theory would be: It's a well-substantiated, well-supported, well-documented explanation for our observations. -The word theory in colloquial use is closer to the concept of a hypothesis in science.

Explain why extracting a single evolutionary progression from a fossil record can be misleading.

-Evolutionary trends does not necessarily mean they're going to be a certain kind, but actually the fossil record is based on shape but doesn't necessarily mean there's close relatedness.We must not only compare shape but DNA and fossil record too. Evolutionary trends do not imply an intrinsic drive toward a particular phenotype. -Extracting a single evolutionary progression from the fossil record can be misleading because the organism may have also evolved before or after the extraction.

Explain the role of population size in genetic drift.

-Genetic Drift describes how allele frequencies fluctuate unpredictably (randomly) from one generation to the next. -Dramatic in smaller populations. -Reduces genetic variation through losses of alleles -Can cause harmful alleles to become fixed (All homozygous= no way they're going to change unless by mutation).

Explain the following statement: "Only natural selection leads to the adaptation of organisms to their environment."

-Genetic flow and genetic drift occur totally randomly. However, natural selection will allow the genomes that are a good adaptation to the environment pass on to the next generation and cause the genomes that aren't good adaptations die out. -Evolution by natural selection involves both change and "sorting". New genetic variations arise by chance, beneficial alleles are "sorted" and favored by natural selection

Describe how heterozygote advantage and frequency dependent selection promote balanced polymorphism.

-Heterozygote advantage: occurs when heterozygotes have a higher fitness than do both homozygotes. (The sickle-cell allele causes mutation in hemoglobin but also confers malaria resistance. Malaria can not survive in sickle cells. Heterozygous: More resistant to disease & not all bad effects of sickle cell. Homozygous Dominant: Target for malaria. Homozygous recessive: Sickle cell suffering -Frequency dependent selection: The fitness of a phenotype declines if it becomes too common in the population. Selection can favor whichever phenotype is less common in a population. Ex. Frequency-dependant selection selects for approximately equal numbers of "right-mouthed" and "left-mouthed" scale-eating fish. As the left mouth decreases, the right mouth increases. As the right mouth decreases, the left mouth increases.

Explain how the existence of homologous and vestigial structures can be explained by Darwin's theory of natural selection.

-Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor (Homology is similarity resulting from common ancestry) -Vestigial structures are remnants of features that served important function in the organisms ancestors -Both Homologous and vestigial structures are inherited from common ancestors which connects with Darwin's theory of natural selection that individuals inherit traits from their ancestors.

Explain why natural selection can act only on heritable traits.

-In natural selection, organisms that are better suited to survival and reproduction will pass their genes on to the next generation. (because they stay alive long enough to pass those traits on, the others do not) Only heritable traits, that can be passed on, have any affect over the next generation.

Explain thoroughly why an individual organism cannot evolve.

-Individuals are born with a sets of genes that are predetermined. There can be no evolution on that individuals within their lifespan. -Individuals do not evolve, populations evolve over time. Natural selection can only increase or decrease heritable traits that vary in a population. -Natural selection occurs through interactions between individual organisms and their environments. There is little evidence that acquired traits can be inherited by their offspring. Rather, it is the heritable traits that are either amplified or diminished via natural selection.

Distinguish an ingroup from an outgroup. a. Explain how outgroup comparison can be used to differentiate shared ancestral characters from shared derived characters.

-Ingroup: The various species -Outgroup: Is a species or group of species that is closely related to the ingroup. Diverged before the ingroup -It's the most closely related to the ancestor because it has the most shared traits (underwent least amount of evolutionary traits.)

Explain why the fossil record provides an incomplete chronicle of evolutionary change.

-It's incomplete (biased) because of all living organisms, very few become fossils, and we only find a few of those very few. -Few have been fossilized, and even fewer have been discovered.

Explain the mechanism for evolutionary change proposed by Jean Baptiste Lamarck. a. Explain why modern biology has rejected Lamarck's theories.

-Lamarck hypothesized that species evolve through the use and disuse of body parts and the inheritance of acquired characteristics -The mechanisms proposed are unsupported by evidence -Proposed a mechanism for how life changes over time -He recognized that evolutionary change explains patters in fossils and the match of organisms to their environment, but proposed an incorrect mechanism -Principle 1: Use and Disuse- Idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate. -Principle 2: Inheritance of acquired characteristics- sated that an organism could pass these modifications to its offspring. -Today, our understanding of genetics refutes this mechanism b/c experiments show that traits are acquired by use during an individuals life are not inherited in the way proposed by Lamarck. -Modern biology has rejected his theories because there is no evidence to support someones acquired characteristics being passed on to the offspring.

Discuss how systematists use the principle of maximum parsimony in reconstructing phylogenies.

-Maximum parsimony assumes that the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely -The simplest; the least amount of changes is the most logical one -Systematics can never be sure of finding the best tree in a large data set, so they narrow the possibilities by applying the principle of maximum parsimony.

Explain why meiosis and random fertilization alone will not alter the frequency of alleles or genotypes in a population.

-Meiosis and random fertilization alone do not alter the gene pool because the genes do not actually change. The genes keep going back into the gene pool.

Explain how molecular clocks are used to determine the approximate time of key evolutionary events. a. Explain how molecular clocks are calibrated in actual time.

-Molecular clocks uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change. -Molecular clocks are calibrated by plotting the number of genetic changes against the dates of branch points known from the fossil record.

Explain the statement "It is the population, not the individual, that evolves."

-Natural selection acts on individuals, but only populations evolve.

Explain in general terms how a complex structure such as the human eye can be the product of gradual evolution.

-Natural selection can only improve a structure in the context of its current utility. Depending on the species needs, a certain structure can improve or go away according to its needs -The human eye came about as a result of descent with modification from a more simple human eye.

Explain the mechanism for evolutionary change proposed by Charles Darwin in "On the Origin of Species".

-Natural selection is the mechanism of descent with modification -Natural selection is a process in which individuals with favorable inherited traits are more likely to survive and reproduce.

Distinguish between artificial selection and natural selection.

-Natural selection: Does not create new traits, but edits or selects for traits already present in the population. ~The local environment determines which traits will be selected for or selected against in any specific population. ~Natural selection is the a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits. -Artificial selection: Humans have modified other species by selecting and breeding individuals with desired traits. -Natural selection is when genes are passed on naturally through animal intercourse. Artificial selection is when they are passed on unnaturally through human intervention examples would be breeding and artificial insemination.

Define neutral variations. a. Explain why natural selection does not act on these alleles.

-Neutral variation: is a genetic variation (differences in DNA sequence) that does not confer a selective advantage or disadvantage. -Natural selection doesn't act on these alleles because the tendency for directional and stabilizing selection to reduce variation is countered by mechanisms that preserve or restore it.

Describe the observations and inferences that led Darwin to propose natural selection as a mechanism for evolutionary change.

-Observation 1: Members of a population often vary in their inherited traits (Lady bugs are not identical, traits vary) -Observation 2: All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce. -Inference 1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals -Inference 2: The unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

Describe the mass extinctions that ended the Permian and Cretaceous periods. Discuss a hypothesis that accounts for each of these mass extinctions, and summarize the evidence for each hypothesis. "A sixth mass extinction may be currently underway." Explain this statement.

-Permian: 251 million years ago. 96% of marine species became extinct. Separate the Paleozoic from the Mesozoic. Also 8 of 27 known orders of insects were wiped out. This all happened over a span of 500,000 years. Caused by volcanic eruptions releasing carbon dioxide which warmed the climate and drops in oxygen concentration because of the slowed mixing of ocean water. -Cretaceous: Separates the Mesozoic from the Cenozoic. (All dinosaurs except for birds died off) Organisms went extinct: About half of all marine species, and many terrestrial plants and animals. Meteorite impacted about 65 million years ago. Dust clouds caused from impact would have blocked sunlight for months-> years which kills plants and a lot of living organisms, and disturbed global climate. -Hypothesis: Number of factors contributed: 1.) A lot of volcanic eruptions: (lava, ash, poisonous gas) 2.) Global Warming: Resulting from the emission of large amounts of CO2 from the volcanoes (Cyclic process) 3.) Reduced Temperature gradient from equator to poles 4.) Oceanic Anoxia from reduced mixing of ocean waters (Lack of oxygen because ocean waters not mixing properly b/c of all events mentioned above) -Sixth mass-extinction may be well underway: A Human caused mass extinction is likely to occur unless dramatic action is taken. We are contributing to the global warming and increasing the rate of extinction. Extinction rates tend to increase when global temperature increase.

Explain how quantitative and discrete characters contribute to variation within a population.

-Phenotypic variation has to do with genetic variation. -Discrete character: Some phenotypic differences due to differences in a single gene and can be classified on an "either-or" basis -Quantitative character: Other phenotypic differences due to the influence of many genes and vary in gradations along a continuum.

Explain why it is crucial to distinguish between homology and analogy before selecting characters to use in the reconstruction of phylogeny. a. Describe how homology and analogy can be distinguished from each other

-Phylogenetic trees show patterns of descent, not phenotypic similarity. Since they show common ancestry, it can only include homology and not analogy because they are related. -Homology: Same shape/ structure through common ancestry (similarity in characteristics resulting from shared ancestry) -Analogy: Same function from independent groups that are not through common ancestry. (similarity between 2 species that is due to convergent evolution. Performing a similar function but having a different evolutionary origin )(wings of insects and wings of birds)

Distinguish between phylogeny and systematics.

-Phylogeny:is the study of evolutionary history of a species or group of related species done by systematics. -Systematics: classifies organisms and determines their evolutionary relationships (How close they are in evolution) **Systematics depict evolutionary relationships in branching phylogenetic trees.** **Phylogenies show evolutionary relationships**

Define the terms population, species, and gene pool

-Population: Is a localized group of individuals of same species that can reproduce successfully and their offspring is fertile (capable of interbreeding and producing fertile offspring) -Gene pool: Consists of all the alleles for all loci in a population -Species: a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.

Explain what Darwin meant by "descent with modification".

-Refers to the view that all organisms are related through descent from an ancestor that lived in the remote past -Organisms share many characteristics. Over evolutionary time, the descendants of the common ancestor have accumulated diverse modifications or adaptations that allow them to survive. -Summarized Darwin's perception of the Unity of Life -underlying mechanism was natural selection

Distinguish between shared ancestral characters and shared derived characters. a. Explain why shared derived characters are useful in establishing a phylogeny.

-Shared ancestral characters:Is a character that originated from an ancestor of the taxon (trait appeared early on in history of taxon shared by all members of the group). -Shared derived characters: Is an evolutionary novelty unique to a particular clade. (Trait appears later in evolutionary history, not shared by all). -Inferring Phylogenies using derived characters: When inferring evolutionary relationships, it is useful to know in which clade a shared derived character first appeared. -because they are unique to particular clades it should be possible to determine the clade in which each shared derived characteristic appeared and use that info to infer evolutionary relationships.

Explain how female preferences for showy male traits may benefit the female.

-Showy male traits indicate good health and good genes and that's what females want. -Also even though the showiness may attract predators, if it gains the male a mate then the frequency for reproduction of that phenotype increases.

Explain why bird and bat wings are homologous as vertebrate forelimbs but analogous as wings.

-The common ancestor of birds and bats had forelimbs but could not fly. Bird and bat wings are homologous as forelimbs because they are similar due to their ancestors. They are analogous as functional wings because they adapted the structures to fly due to their environment.

Explain how the fossil record may be used to test our current understanding of evolutionary patterns.

-The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time. -It allows us to study species that have been extinct for years -Fosils show the evolutionary changes that occurred in various groups of organisms. Over time these fosils show that decent with modification produced increasingly large differences among related groups of organisms, resulting in diversity of life.

Explain the neutral theory of evolutionary change.

-The neutral theory of molecular evolution contends that most evolutionary change at the molecular level is driven by genetic drift rather than natural selection. The neutral theory does not suggest that random drift explains all evolutionary change: natural selection is still needed to explain adaptation.

Explain the statement: "A phylogenetic tree represents a hypothesis about evolutionary relationships."

-The tree of like is like an estimation of evolution in the past

Explain how scientists determined the approximate time when HIV-1 M first infected humans.

-They had data on the years that HIV was in humans and they used an adjusted best-fit line (which accounts for uncertain dates of HIV sequences)

Describe the conditions in the interior of a supercontinent such as Pangaea.

-Tropical climate all around (PANGEA) OR -Formation of the supercontinent Pangea had many effects: (AFTER PANGEA) 1.) A deepening of ocean basins 2.) A reduction in shallow water habitat 3.) A colder and drier climate inland

Explain why mutation has little quantitative effect on allele frequencies in a large population.

-because mutatations occur in the somatic cells most of the time and are lost whenthe individual dies. Therfore it doesn't get passed on through different generations.

Explain how sexual recombination generates genetic variability.

-gametes have different genetic background and sexual reproduction rearranges exisiting allels into fresh combinations for each generation. This provides much of the genetic variation that makes evolution possible. -In sexually reproducing organisms, most genetic variation results from recombination of alleles. -Sexual reproduction can shuffle existing alleles into new combinations through 3 mechanisms: 1.) Crossing over 2.) Independent assortment 3.) fertilization

Explain why the majority of point mutations are harmless.

-this is because they only will change the phenotype, also they usually occur in non coding regions, where no protein products are made. But if they do occur in amino acids it wouldn't have an effect on the proteins function. -Majority are harmless because hey are a change in one base in a gene, and doesn't always cause a frame shift. -Mutations in noncoding regions of DNA are harmless -Mutations in a gene can be neutral (silent) -Mutations that result in a change in protein are often harmful, but can sometimes be beneficial because it allows adaptation more advantageous than the previous

List four reasons why natural selection cannot produce perfect organisms.

1.) Natural selection can act only on existing variations (Only on what's present in population) 2.) Evolution is limited by historical constraints (Common ancestry has certain features natural selection has to work with) 3.) Adaptations are often compromises (Showiness of peacock. Healthier, stronger, but more visible to predators) 4.) Chance, natural selection, and the environment interact (tailoring for best fit for the organism of that environment)

List the five conditions that must be met for a population to remain in Hardy-Weinberg equilibrium.

1.) No mutations 2.) Random mating 3.) No natural selection 4.) Extremely large population size 5.) No gene flow

Define relative fitness

Relative fitness: The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals.

Write the Hardy-Weinberg equation. Use the equation to calculate allele frequencies when the frequency of homozygous recessive individuals in a population is 25%.

p^2+2pq+q^2=1; p+q=1; p=1-q; q=1-p ALLELE FREQUENCIES --> p=.25, q=1-p, so q=1-.25 =.75 q=.75 (.25)^2+2(.25)(.75)+(.75)^2=1

Distinguish among directional, disruptive, and stabilizing selection. a. Give an example of each mode of selection.

~3 modes of natural selection: -Directional selection: favors individuals at one end of the phenotypic range (favors one) ~Ex: Black rock from lava covers new Mexico. Light mice are more easily spotted than dark mice, so it pushed for the selection to be towards dark mice. -Disruptive selection: Favors individuals at both extremes of the phenotypic range (Favors both) ~Ex: pop of black bellied seedcrack finches in Cameroon whose members have two distinct beak sizes. Small biled for soft seeds and large birds for hard seeds to crack them. Birds with intermediate sized bills were insufficient for the soft seeds and the hard seeds, have low realitive fitness. -Stabilizing selection: Favors intermediate variants and acts against extreme phenotypes (Favors middle) ~Ex: Babies born less than 6.5 lbs are born premature and babies born more than 10 lbs are at a disadvantage. The preferred weight is in the middle.