Bio 2 Exam 1 Review PDF

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review of first few chapters that were on the exam...

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Chapter 22: Descent with modification, a Darwinian view of life 1. Identify Darwin and Wallace’s contribution to the theory of evolution, and place it in the context of the ideas proposed previously Darwin proposed:  Adaptations: the characteristics that allow organisms to survive in determined environments  Traits can be accumulated throughout time and manifest at some point  Natural Selection: the theory that states that the organisms with better adaptations to the environment, are a better match to it, have a higher chance of survival in said environment than those who do not.  Studied in the Galapagos Islands  Though that present organism had a common ancestor  INDIVIDUALS DO NOT EVOLVE… POPULATIONS DO  Observation #1: the traits inherited are not always the same (later known as Dominant and Recessive)  Observation #2: the species have the ability to produce more organisms that the environment can support, therefore some of these offspring’s may die because not enough resources. o Inference #1: Organisms with specific traits that survive in their environment are more likely to reproduce and leave offspring o Inference #2: As the organisms with the non-favorable traits for the environment die, they take those traits with them, making all the favorable traits remain. Wallace proposed:  Studied species on South Pacific islands, Malay Archipelago  Proposed a natural selection theory very similar to Darwin  Push that Darwin needed to write his book on development of species 2. Explain five lines of evidence that support the theory of evolution: fossil record, biogeography, convergent evolution, direct observations (natural and artificial selection) and homologies  Fossils: Depth of fossils can help determine relative age; Compare characteristics between species; how they evolved. Ex. Fishapod (Tiktaalik roseae), Illuminates steps leading to evolution of tetrapods, Transitional form – provides link between earlier and later forms  Biogeography: Isolated continents and island groups have evolved their own distinct plant and animal communities, Separation of islands allows insular

animals to evolve independently of their mainland relatives, Fossils and biogeography show evolutionary patterns. Ex. Island fox (Urocyon littoralis) evolved from mainland gray fox (Urocyon cinereoargenteus)

 Convergent Evolution: 2 different species from different lineages show similar characteristics because they occupy similar environments. Often, species independently evolve similar solutions to similar problems. Ex. Giant anteater and echidna both have long snouts and tongues to feed on ants  Selective breeding/artificial selection: There must exist variation in the population in order; Some characteristics can change in only a few generations of selective breeding. Ex. Bacteria resistance to antibiotics came about because the few bacteria that had the genes to resist antibiotics, survived and reproduced.  Anatomical homology: Same set of bones in the limbs of modern vertebrates has undergone evolutionary change to be used for many different purposes, Homologous structures are derived from a common ancestor

 Developmental homology: Species that differ as adults often bear striking similarities during embryonic stages, Presence of gill ridges in human embryos indicates that humans evolved from an aquatic animal with gill slits, Human embryos have long bony tails

 Molecular homology: Similarities in cells at the molecular level indicate that living species evolved from a common ancestor or interrelated group of common ancestors, All living species use DNA to store information, Certain biochemical pathways are found in all or nearly all species

3. Describe the mechanism of natural selection  Variation within a given species  Heritability (not yet understood)  Differential reproductive rates  *GENETIC VARIATION MUST COME BEFORE NATURAL SELECTION/ EVOLUTION* 4. Define the following terms: descent with modification, homology, homologous structure, analogous structure, convergent evolution, fossil, vestigial structure, evolutionary tree, biogeography, artificial selection, adaptation  descent with modification: simply passing traits from parent to offspring  homology: Fundamental similarity due to descent from a common ancestor  homologous structure: an example of an organ or bone that appears in different animals, underlining anatomical commonalities demonstrating descent from a common ancestor.  analogous structure: various structures in different species having the same function but have evolved separately, thus do not share common ancestor.  convergent evolution: 2 different species from different lineages show similar characteristics because they occupy similar environments  fossil: the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.  vestigial structure: is an anatomical feature that no longer seems to have a purpose in the current form of an organism of the given species. Often,

these vestigial structures were organs that performed some important function in the organism at one point in the past.  Evolutionary (or phylogenic) tree: branching diagram or "tree" showing the inferred evolutionary relationships among various biological species based upon similarities and differences in their physical or genetic characteristics.  biogeography: Study of the geographical distribution of extinct and modern species  artificial selection: Programs and procedures designed to modify traits in domesticated species, by breeding only organisms with desirable traits. *THIS HAS AN END GOAL*  adaptation: a change or the process of change by which an organism or species becomes better suited to its environment. Chapter 23: Evolution of populations 1. Explain how the smallest unit of evolution is a population  Population is the level that evolve because the mutations that happen in the individuals are usually very small and unnoticeable/nonharmful  These mutations accumulate from individual to individual until eventually something DOES change due to these accumulations and a new “species” arise  The individuals themselves stay the same and when they mate, their OFFSPRING are the ones that can be changed. 2. Discuss why variation in populations is common and is necessary for natural selection  Variation in a trait had to be there to begin natural selection  NOTICE: Natural selection shrinks the gene pool/gene variation, because it goes from large quantity of genes and pick specific ones because X, Y and the ones that are not in this selection disappear, leading to extinction. 3. Use the Hardy-Weinberg equilibrium to answer questions about allele frequency, genotype frequency, and evolution in a population  p+q=1

 p and q represent the different alleles. So ‘p’ could be A and ‘q’ could be a genotype.

4. Describe the five conditions required for Hardy-Weinberg equilibrium and recognize that all these conditions are not met in real populations, hence allele and genotype frequencies change over time  No new mutations occur  No natural selection occurs  The population is so large that allele frequencies do not change due to random sampling error  No migration occurs between different populations  Random mating  In reality, no population meets these conditions  If frequencies are not in equilibrium, an evolutionary mechanism is at work 5. Differentiate the 4 patterns of natural selection (directional, disruptive, stabilizing, balancing) and the mechanisms that lead to them  Directional selection: one extreme phenotype is favored, phenotype moves toward that extreme over time

 Stabilizing selection: extreme phenotypes are less fit than the optimal intermediate phenotype – most common in stable, unchanging environments

 Disruptive selection: 2 or more extreme phenotypes are fitter than the intermediate phenotype

 Balancing selection: maintains genetic diversity  For a single gene, heterozygote favored  No Harmful alleles persist in the population because two harmful diseases can balance each other out. (Ex. Malaria and Sickle Cell, if a person as homozygous of the Malaria allele, then they will die due to malarial infection. However, if the person has heterozygous of both alleles then the person lives due to protection form both)  Negative frequency-dependent selection o Rare individuals have a higher fitness

6. Define sexual selection and distinguish between intra- and intersexual selection  Sexual selection: A form of natural selection in which individuals with certain inherited characteristics are more likely than others to obtain mates

 Intrasexual selection: describes competition among members of the same sex (two deer’s fighting)  Intersexual Selection: Between members of the opposite sex; Usually females choice and often results in showy characteristics for males (peacock) 7. Recognize that natural selection is not goal-oriented, and cannot produce perfect organisms  Environments/niches change. 1. Selection can only occur on existing variations 2. Evolution is limited by historical constraints (evolution doesn't scrap together parts all of a sudden) 3. Adaptations are often compromises (seals walk poorly on land) 4. Chance events can affect evolution (environment changes) 8. Indicate why genetic drift has a greater effect in small populations, and identify particular situations in which genetic drift occurs  It's much easier to change the ratio of alleles in small populations, sometimes even eliminating the other allele(s) present and possibly fixing harmful alleles into a population  An example using the bottle-neck effect, is where there is a population of green, yellow, and brown frogs living in a pond. The pond dries up to half its size then later refills but there are only yellow and brown frogs now.

9. Define the following terms: gene pool, population, microevolution, macroevolution, bottleneck effect, founder effect, genetic drift, gene flow, migration, fitness  gene pool: all of the alleles for every gene in a given population

 population: Members of the same species that are likely to encounter each other and thus have the opportunity to interbreed  microevolution: small scale change relating to changes in a single gene in a population over time  Macroevolution: larger scale changes relating to formation of new species or groups of species  bottleneck effect: population reduced dramatically and then rebuilds without some alleles from the previous gene pool

 founder effect: Small group of individuals separates from a larger population and establishes a new colony  genetic drift: changes allelic frequency due to random chance unrelated to fitness  gene flow: occurs when individuals migrate between populations having different allele frequencies  migration: seasonal movement of animals from one region to another.  fitness: is an organism’s realized ability to reproduce relative to other individuals. * More offspring relative to others = more fitness* Chapter 24: Origin of species and macroevolution 1. Describe the various definitions of species (biological, morphological, ecological and phylogenetic species concept), and the limitations of each

 Biological (or Reproduction isolation): Prevents one species from successfully interbreeding with other species  Drawbacks: o Does not apply to asexual species o Can interbreed and yet do not? o Cannot be applied to extinct species  Morphological: Based on physical characteristics  Drawbacks: o How many traits to consider o Arbitrary in traits that vary in a continuous way o members of the same species can look very different while members of a different species can look very similar  Phylogenetic (or Evolutionary): Fossil and DNA evidence can be used to piece together evolutionary relationships  Drawbacks: o The cutoffs are arbitrary  Ecological: Variety of factors related to an organism’s habitat can be used to distinguish one species from another  Drawbacks: o Ecological characteristics aren’t always in line with evolutionary history 2. Discuss why reproductive isolation is necessary for divergence in populations  The existence of biological factors (barriers) impede members of two species from interbreeding and producing viable, fertile offspring 3. Identify the eight mechanisms of reproductive isolation Prezygotic Barriers- Prevent formation of zygote Postzygotic Barriers- Block development of viable, fertile individuals  Habitat Isolation: Geographic barrier prevents contact among individuals

 Temporal Isolation: Individuals reproduce at different times of the day or year

 Behavioral Isolation: E.g. differences in song or dance

 Mechanical Isolation: Size or incompatible genitalia prevents mating  Gametic Isolation: Gametes fail to unite successfully; Important in species that release gametes into the water or air  Reduced Hybrid Inviability: fertilized egg cannot progress past an early embryo  Reduced Hybrid Sterility: interspecies hybrid viable but sterile, e.g. Mules  One of the common reasons for hybrid sterility is that the parent species have different numbers of chromosomes and thus meiosis cannot separate cells with equal numbers of chromosomes.  Hybrid Breakdown: hybrids viable and fertile but subsequent generations have genetic abnormalities 4. Explain common ways in which sympatric speciation can occur  Sympatric speciation: speciation in the same habitat  Much less common then allopatric speciation  Mechanisms:  temporal isolation  gametic isolation  polyploidy  adaptation to local environments  sexual selection

5. Recognize that allopatric speciation is the most common way in which new species arise  Allopatric speciation: geographic isolation prevents gene flow between two or more populations.  Over time, differences in DNA build up between the separate populations and they become different species.  Hybrid zones are places where two populations can interbreed, allowing gene flow; Populations stay connected.

6. Define the following terms: speciation, reproductive isolation, fusion, biological species concept, allopatric speciation, sympatric speciation, hybrid zone, polyploidy, hybrid, intraspecific, interspecific, adaptive radiation  speciation: formation of a new species, requiring reproductive isolation

 reproductive isolation: Prevents one species from successfully interbreeding with other species  Fusion: A process in which gene flow between two species that can form hybrid offspring weakens barriers to reproduction between the species. The process cause their gene pools to become increasing alike and can cause the two species to fuse into a single species.

 biological species concept: definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do not with members of other such groups.  allopatric speciation: Formation of new species in populations that are geographically isolated form one another.  sympatric speciation: formation of new species in the same habitat  hybrid zone: A geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry.  polyploidy: A chromosomal altercation in which the organism possesses more than two complete chromosome sets. It is the results of an accident of cell division.  hybrid: the offspring of two plants or animals of different species or varieties, such as a mule (a hybrid of a donkey and a horse).  intraspecific: produced, occurring, or existing within a species or between individuals of a single species.  interspecific: existing or occurring between different species.

 adaptive radiation: the diversification of a group of organisms into forms filling different ecological niches. Chapter 25: History of life on earth 1. Discuss how eukaryotic cells evolved from prokaryotic cells  The endosymbiont theory:  mitochondria and plastids were formerly small prokaryotes that began living within larger cells  the prokaryotic ancestors of mitochondria and plastids probably entered the host cell as undigested prey or parasites 2. Explain the biases of the fossil record

3. Describe the main steps necessary for the evolution of life on earth, and plausible hypotheses (with evidence, when available) about how these steps occurred 1. Nucleotides and amino acids produced prior to the existence of cells  Formation of organic molecules  Hypothesis’s: o Reducing atmosphere hypothesis (Miller and Urey Experiment): organic molecules were formed by the environment of prehistoric Earth.

o Extraterrestrial hypothesis: meteorites brought organic carbon to Earth, including amino acids and nucleic acid bases  Opponents argue that most of this would be destroyed in the intense heating and collision o Deep-sea vent hypothesis: biologically important molecules may have been formed in the temperature gradient between extremely hot vent water and cold ocean water  Supported by experiments

2. Nucleotides and amino acids became polymerized to form DNA, RNA and proteins  Experimentally, prebiotic synthesis of polymers not favorable in aqueous solutions o Hydrolysis competes with polymerization  Experiments have shown spontaneous formation of nucleic acid polymers and polypeptides on clay surface or hydrothermal vents.

3. Polymers became enclosed in membranes  Protocells: Aggregate of prebiotically produced molecules and macromolecules that acquired a boundary, such as a lipid bilayer, that allowed it to maintain an internal chemical environment distinct from that of its surroundings  4 characteristics of protocell: o Boundary separated external environment from internal contents o Polymers inside the protobiont contained information o Polymers inside the protobiont had enzymatic function o Protobionts capable of self-replication  Two Potential origins of cells: o Coacervates: Association of charged polymers o Liposomes: Vesicles surrounded by lipid bilayer 4. Polymers enclosed in membranes acquire cellular properties

 Protocells acquire cellular properties

 RNA world hypothesis o Majority of scientists favor RNA as the first macromolecule of protobionts o 3 key RNA functions  Ability to store information  Capacity for self-replication  Enzymatic function – ribozymes  DNA and proteins do not have all 3 functions

4. State the age of the earth, and within order of magnitude, approximate time of appearance of: prokaryotes, eukaryotes, multicellular eukaryotes, animals, land plants, humans  Earth is 4.6 billion years old  Order of Appearance:  Prokaryotes- 3.5-3.8 BYA  Single-cellular eukaryotes- 2 BYA

   

Multicellular eukaryotes- 1.5 BYA Animals- 700 MYA Land Plants- 300 MYA Humans- 170 TYA

5. Describe how the earth’s environment has changed over its history, and how major environmental changes have affected living organisms  Anaerobic prokaryotes originated, flourished, and declined as the oxygen content of the atmosphere rose  Continental drift (plate tectonics) alters the habitats where organisms live, the physical environment, and climate change  Continental drift promotes allopatric speciation  Mass extinctions can reduce a thriving and complex ecological community to a pale shadow of its former self  Adaptive radiations; groups of organisms increased in diversity as they came to play new ecological roles in their communities  Other major environmental changes: Climate/temperature change, atmosphere, land masses, flood, glaciation, volcanic eruptions, meteoric impacts. 5. Estimate the age of a fossil using radiometric dating, and explain how depth of a fossil in sedimentary rock can help understand the relative age of a species  The order of fossils in rock strata tells us the sequence in which the fossils were laid down  In radiometric dating a "parent" isotope decays to a "daughter" isotope at a characteristic rate  The rate of decay is expre...