Biology 131 exam review pt 2

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Name the 4 observations that lead Darwin to formulate his theory of evolution via natural selection.

1. Members of a population vary in their traits.
2. Offspring inherit traits from their parents.
3. All species tend to produce more offspring than their environment can support.
4. Many offspring usually die due to lack of resources.

What are the 2 inferences Darwin made based upon the 4 observations?

1. Individuals who have traits that allow them a higher chance of survival usually leave more offspring.
2. Unequal ability to survive & reproduce will cause favorable traits (adaptations) to accumulate in a population over generations.

Define evolution.

Descent with modification.

Explain the mechanisms of natural selection.

1. process by which individuals w/ favorable traits reproduce & survive @ higher rate than other individuals.
2. Overtime, will create better match between organisms and environment.
3. If environment changes or organisms move to new environment, NS can lead to an adaptation leading to the origin of a new species.
4. Individuals do not evolve, but rather the population will evolve over time.
5. Can only amplify or diminish heritable traits.
6. The traits selected for depend on the context of the environment (traits that are favorable in one environment may not be favorable n another).

Name 5 main sources of evidence for evolution?

1. Fossil Record
2. Biogeography
3. Comparative Anatomy
4. Molecular Biology (genetics)
5. Embryology

How does the Fossil Record provide support for evolution?

Document changes of organisms over time

How does biogeography provide support for evolution?

Explains distribution of species around the world through events such as continental drift.

How does comparative anatomy provide support for evolution?

1. homology: similar structure due to common ancestry
-vestigial organs: organs with no discernible purpose (ex legs on snakes or whales)
-evolutionary anachronisms: things that don't make sense unless you look at them in light of evolution. (ex avocados can produce asexually, but usually doesn't do so in nature. There must have been an organism that could digest it's pit)
-exaptations: adaptations that used to serve a different function (ex feathers on birds weren't always used for flight)

How does embryology provide support for evolution?

Study of organismal development. More closely related organisms should have more similarities in their development than with distantly related organisms. (ex at some point in development, all embryos have 2 chambered heart and gill pouches)

How does molecular biology/genetics provide support for evolution?

more closely related organisms should share more sequences of DNA (ex chimps share more DNA with humans than with any other organism)

Why is antibiotic resistance occurring so rapidly?

Bacteria reproduces quickly in short periods of time, thus evolutionary development occurs quickly. People take antibiotics when they don't need them, and sometime don't finish the entire dosage, thus leaving the more resistant strains of bacteria to multiply. In some cases, more meds are prescribed than needed. In addition, many antibiotics are used in feed for livestock that we ingest.

What can we do to limit antibiotic resistance?

1. only take meds as needed (more diagnostic testing must be done).
2. finish entire prescription
3. Understand necessary dose
4. Limit antibiotics in livestock feed
5. Look for new drugs in nature.

Why doesn't natural selection create perfect organisms?

1. Natural selection is an editing process, and selection can only occur among currently existing traits which may not always be ideal.
2. Adaptations are usually compromises
3. Chance events: can make previously desirable traits undersirable
4. Depends on time and place: adaptations are subject to environmental conditions which are constantly changing (Red Queen Hypothesis)

What is a population and it's characteristics?

Group of individuals of the same species living in the same place at the same time.

Characteristics: interbreed within population, can be isolated or overlap with other populations, concentrated in center region, small biological unit that can evolve

What is a gene pool?

All the alleles in a population at a given time.

What are p and q?

p= frequency of dominant allele
q=frequency of recessive allele

What are the conditions of Hardy-Weignberg equilibrium?

1. large population size
2. random mating (no mate preference)
3. no gene flow (no individuals moving in/out of population)
4. no mutations
5. no selection/evolution

How does natural selection drive evolution?

Individuals with advantageous traits leave more offspring. The favoring of certain traits over others leads to variation between populations.

What are the different types of natural selection?

1. Directional selection: favors an extreme phenotype (black or white mouse)
2. Disruptive selection: favors both extreme phenotypes over intermediate (black and white mouse)
3. Stabilizing selection: favors intermediate phenotype (gray mouse) over extremes
4. Sexual selection: natural selection for mating success
-intrasexual selection: competition for mates by individuals of the same sex (ex elk rutting season)
-intersexual selection: mate choice (usually by females) peacock plumage
5. Balancing selection: when 2 or more phenotypes are preserved by natural selection.
-Heterozygote advantage: individuals who are heterozygous for a trait have greater fitness than homozygous individuals (ex sickle-cell anemia)

What is genetic drift, and how does it help drive evolution?

1. Change in gene pool of a small population due to a chance event. Can be detrimental to certain alleles in a small population.

Name 2 types of genetic drift and define them.

1. Founder Effect: when a small group of individuals get separated from the parent population, and establishes a new population whose gene pool differs from parents population. Usually accounts for widespread of inherited disorders (ex Tristan de Cunha colony)
2. Bottleneck Effect: Caused by drastic decrease in population size. Due to chance, certain alleles over/underrepresented, and some alleles are lost due to a sudden chance event. Populations effected will usually show little variation and take much longer for population size to recover. Usually populations affected by humans.

What is gene flow and how does it help drive evolution?

transfer of alleles in/out of population by movement of fertile individuals.If extensive enough, will cause neighboring populations to merge. Natural selection will cause newly introduced alleles to be amplified or diminish.

How can mutations help drive evolution?

the original source of variation. If new mutation gives individual heightened advantage or disadvantage, it can greatly influence population allele frequency.

Why are unfavorable phenotypes maintained in a population?

1. diploid cells: most eukaryotes are diploid, thus genetic variation gets hidden in the form of recessive alleles. The recessive alleles that are unfavorable can be hidden & passed on through heterozygotes, but exposed if 2 heterozygotes mate.
2. Balancing selection: when 2+ forms of a gene preserved in a population through heterozygote advantage & frequency dependent selection (the fitness of a phenotype will decrease if it becomes too common e.g. side-blotched lizard)

What is a species?

A population or group of populations of interbreeding organisms whose members have the potential to interbreed in nature and produce fertile offspring (biological species concept).

What are pre-zygotic reproductive barriers to species interactions? Name some ways in which these occur.

Block fertilization from happening (blocking before the egg and sperm come together).
1. Gametic isolation: no union of male & female gametes
2. Habitat isolation: live in different geographic regions
3. Temporal isolation: different breeding seasons
4. Behavioral isolation: different species have different courtship rituals & distinctive odors
5. Mechanical isolation: structural differences in sex parts

What are post-zygotic barriers? Name some ways in which these can occur.

Reproductive isolation that occurs after fertilization (egg & sperm come together) occurs.
1. Hybrid inviability: hybrid of 2 species usually dies before reaching sexual maturity
2. Hybrid Sterility: Hybrid does not produce functional gametes, thus can't reproduce
3. Hybrid breakdown: offspring of hybrids are feeble of sterile.

Name the mechanisms of speciation.

1. Allopatric speciation: occurs when a populate suddenly gets divided geographically and becomes 2 subpopulations that are reproductively isolated from each other by a geographic barrier. (most common)
2. Sympatric speciation: new species originate without geographic isolation from the parent population. Helps changes occur in single generation.
-Can occur due to polyploidy (species originates by accident due to extra set of chromosomes occurring during cell division making offspring unable to breed with parent population.)

What are the different tempos of speciation?

1. Gradual: Darwinian view suggesting speciation occurs over time and is the accumulation of several small changes through time.
2. Punctuated Equilibrium: coined by Niles Eldredge & Stephen J. Gould in 1972. Suggests that most speciation occur suddenly, then is followed by periods of stasis. The change will occur over a period of a couple of thousand years, then will be followed by millions of years worth of stasis. Correlates to what is observed in fossil record.

What is cladistics?

Method of hypothesizing relationships among organisms (method of constructing phylogentetic trees)

What are the steps for creating a cladogram?

1. Choose the taxa of interest
2. Determine the characters and examine each taxa to determine character states. Be sure to select characters that are homologous.
3. Figure out the order of evolution for each character.
4. Group taxa by synapmorphies (derived/changed states shared by 2+ taxa)

What is a synapmorphy?

Derived or changed character state shared by 2+ taxa. Labeled on cladogram @ node.

What is an in-group?

Group of taxa being studied.

What is an out group?

Taxa outside the group of interest; usually a distantly related relative of in-group.

What is a clade?

Group of organisms that includes an ancestor and all the descendants of that ancestor.

What does it mean to be monophyletic?

The cladogram displays 1 ancestral species with all of it's descendants.

What does it mean to be paraphyletic?

A grouping that includes an ancestral and some (but not all) of it's descendants.

What does it mean to be polyphyletic?

A grouping of related taxon, but no common ancestor.

Name and define the possible mechanisms for biological novelties.

1. Most transformations evolved in increments from much simpler versions that performed a similar function.
2. Exaptations: adaptations of old structures to serve a new purpose
3. Evo-Devo (Evolution and Development): changes in a few genes in early development that cause significant changes later.
-Heterochrony: change in rate or timing of development
(eg: Paedomorphosis: retaining juvenile features into adulthood)

What is Neoteny?

Slowing down of development so that at an older age they have younger features.

What is Progenesis?

Stopping development at a younger age, then speeding up sexual mature later on in life

What are homeotic genes?

Genes that control the placement and organization of body parts.

How is life classified?

Linnaean Classification system.

What is the approximate age of the earth?

4.6 Ba

Name the major divisions in the history of the earth (eons & eras)

1. Eons: Archaean, Proterozoic, Phanerozoic
2. Eras within Phanerozoic: Paleozoic, Mesozoic, and Cenozoic.

What is the Oparin-Haldane hypothesis?

The early Earth had a reducing atmosphere, and with some lightning & UV radiation, very simple organic molecules could be formed.

What is the Miller-Urey experiment?

Miller & Urey recreated the conditions of the early Earth's atmosphere (composed of ammonia, methane and hydrogen gas) in test tubes, and shocked the systems. As a result very simple organic molecules (amino acids) were formed.

Explain the 4 part process of the origin of life.

1. abiogenesis: abiotic synthesis of simple organic molecules.
2. Synthesis of polymers: combining of simple organic molecules to form polymers.
3. Creation of probionts: molecules packaged into semi-permeable membranes with internal conditions different from external environment.
4. Origin of genetic material that make reproduction possible.

Explain the endosymbiont origin of mitochondria & plastids.

It is likely that the mitochondrion was an organism engulfed by another organism, and later began to reside within larger organism as an organelle. It is likely that this was one of the first endosymbionts since it is shared by all organisms. Plastids, are likely to have been ancient cyanobacteria since they share similar DNA. Possibly 2ndary endosymbionts due to double membrane.

Give a brief summary of the first 2.5 billion years of the earth's history.

1. 4.6 Ba = Earth's origin
2. 4.6-3.9 Ba = molten planet
3. 3.8-3.5 Ba = 1st signs of life (confirmed by Stromatolite fossils)
4. 2.7-2.2 Ba = oxygen levels begin to rise; possibly around time of first eukaryote origin

Give a brief summary of the earth's history from 2.1 Ba.

1. 2.1 Ba first eukaryotes arise
2. 1.5 Ba first multicellular organisms
3. 570 Ma first soft bodied organisms
4. 542 Cambrian explosion

What is plate tectronics? How has it impacted species diversity?

1. Plate tectronics: move of the continents on the earth's crust
2. Affects distribution of species around the world. May also affect habitats, due to rising & lowering of sea level, as well as mountain formation.

Name the major extinctions, their impact & when they occurred.

1. End-Permian (250 Ma): about 90% species go extinct
2. Cretaceous/KT (65 Ma): end of the big dinos

Name the basic features of prokaryotes.

1. 2 domains: Bacteria & Archaea
2. smaller than eukaryotes
3. usually no membrane bound organelles or nucleus
4. Have nucleiod region
5. have capsule used for protection against body's defenses
6. Reproduce via binary fission
7. have a cell wall
8. flagella (1/10th) that of eukaryotes
9. many have plasmids

What are plasmids?

Individual rings of DNA that replicate separately from chromosome.

What are the different modes of nutrition of prokaryotes?

1. Photoautotroph: photosynthesize
2. Chemoautotroph: use inorganic compounds such as carbon dioxide
3. Chemoheterotroph: use inorganic compounds and carbon for energy
4. Photoheterotroph: use light energy and organic compounds

Name the synapmorphies that make Archaea a sister group to Eukarya.

1. histones
2. growth no inhibited by antibiotics
3. no peptidoglycan in cell wall
4. use methionine as initiator
5. have introns

List some of the harms and benefits prokaryotes give to humans.

1. 1/2 human parasites are bacteria
2. decomposers
3. used for fermentation
4. genetically modified for our use
5. used for research
6. symbiotic relationships (500+ species used to aid in our digestion)

Name some general characteristics of Protists. Why is it such a diverse group?

1. Eurkaryotes.
2. most are unicellular
3. nutritionally diverse
4. mainly aquatic
5. Very divers due to endosymbiosis & secondary endosymbiosis

Name the protist groups and one example of a genera.

1. Diplomanadida (Giardia) & Parabasala (Trichomonas)
2. Kinetoplastida (Trypanosoma) & Euglenoids (Euglena)
3. Alveolata (paramecium)
4. Stramenopila (Oomycota)

Why are Charophyta & green algae considered the closest living relatives to plants?

1. peroxisome enzymes
2. similar % of cellulose in cell walls
3. Similar structure of flagella in sperm
4. form phragmoplast (template where cell plate can occur doing mitosis)
5. similar chloroplast DNA

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