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What is involved in the scientific method?
How does natural selection lead to evolution?
Due to the higher reproductive success of organisms that are more “fit,” the chances that the heritable genes of a particular genetic mutation in organisms will result in a species evolving.
What 2 aspects contribute to variation in a population, and which of these are heritable?
There are environmental variations due to the conditions that a species exists in, and there are genetic variations due to differences in the genetic material of a species. The genetic variation can be passed to offspring and those differences will be inherited.
How does artificial selection result in evolution?
Artificial selection can result in rapid evolution when humans choose to select for certain properties that they are interested in. For example, if a type of corn crop produces more edible material, a human will favor that species of corn and grow more of it, quickly changing the allele frequency of that corn.
What is the tree of life and how is important for the study of biology?
The tree of life shows the 3 classifications we currently use to describe all life. It helps us understand the relatedness of all organisms.
What are the sources of new genetic material in a population?
Genetic material can occur in mutations and recombination. Mutation can be random and may be the result of an error in the formation of new genetic material. Recombination can mix those mutations and create new alleles.
What role can this new genetic material play in the population?
If those mutations are beneficial to the reproductive success of an individual, that may result in the population evolving over time.
What is adaptation and how does it relate to evolution?
Adaptation shows how natural selection can seemingly make a species a perfect fit for an environment. Although evolution does not “choose” to direct species a certain way, over time, species with adaptations that are beneficial to its survival and ability to pass on heritable traits will make it seem like those species were made to exist in that environment when they have actually adapted to do so.
How do we measure genetic variation and changes in genetic variation in a population over time?
Genetic variation and allele frequency was originally measured by noting observable genotypes, or phenotypes, and documenting the variation. Now, we are able to observe genetic variation through electrophoresis.
What are the required conditions for H-W equilibrium and would each condition affect the population? How is allele and genotype frequency calculated using H-W, and what can this information tell us?
H-W equilbrium requires no gene flow, no natural selection, no genetic drift, no mutations, and random mating. From allele frequencies, we can also calculate genotype frequency as such: p+q=1, and p2 + 2pq + q2 = 1. If a population is evolving, we can study this population and try to establish which condition of H-W equilibrium is not being met.
What is Hardy-Weinberg (H-W) Equilibrium and how is it used to understand evolution in populations?
H-W is the null hypothesis of evolution, showing that the allele frequency of a population will stay at certain frequencies given a set of conditions.
How did our understanding of Natural Selection develop?
Darwin’s theory of natural selection arose from his curiosity and observations that showed how different species of organisms seemed perfectly adapted to survive in their environments. Combined with the idea that small changes in small timeframes can represent large changes over longer timeframes.
In what ways can natural selection affect change in a population?
Natural selection affects individuals, but over time, a population will evolve.
What is the role of mutations in the process of natural selection?
Beneficial mutations will be positively selected for and harmful mutations will be negatively selected for. This means that those beneficial mutations will be more likely to be passed on to the next generation.
How is sickle cell anemia an example of heterozygote advantage?
Sickle cells in a homozygous form will be very painful to the carrier, and regular blood cells in homozygous form may potentially carry malaria. Sickle cell anemia in a heterozygous form will allow those sickled cells to avoid being affected by malaria.
What is artificial selection and how is it similar and different from natural selection?
Artificial selection is the selective breeding by humans of organisms to favor a certain trait.
How is sexual selection related to natural selection?
Sexual selection is the selection of mate. In many cases, the reason for selection of that mate may be due to the observance of traits that make the mate more fit.
What are the evolutionary tradeoffs in sexual selection?
Sexual selection may help propagate an allele that would otherwise be selected against by natural selection, i.e. peahens select for the large, bright tail of the peacock, which should under most other circumstances should be selected against.
Why does genetic drift affect smaller populations more than large populations?
If genetic drift occurs among a smaller population, a large percentage of that population has drifted. The new population may have a genetic pool that is not representative of the original allele frequencies.
What is the role of genetic drift in bottlenecks and founder events?
Genetic drift due to bottlenecks and founder events could create different allele frequencies in the new populations. If those new populations are small enough, they could undergo fixation due to the small amount of variation in that population.
How can migration affect a population?
Migration can mix populations and introduce new alleles to an existing gene pool.
What is a molecular clock and why is it useful for our understanding of evolution?
A molecular clocks shows us the rate of evolution of a particular allele. We can better understand how fast (or slow) these mutations are taking place.
What are the definitions of a species and why is a species so difficult to define?
A species can be defined in many ways, but it has been hard to find 1 definition that suits every species.
We mainly use the BSC, but what are the complications in using this definition?
Although it is the main speciation concept, it is hard to use in the present time. That requires mating 2 organisms and then observing whether the offspring is capable of mating.
How is the morphospecies concept used and what are the difficulties related to using it?
It suggests that different species look different and same species look the same; however, there is evidence that this concept cannot be applied broadly. There are many species that look like other species, but will not mate with the other species.
What role does reproductive isolation play in maintaining species?
Reproductive isolation can keep species apart and the barriers that create the isolation can be the source of that.
What are examples of pre-zygotic mechanisms of reproductive isolation?
Pre-zygotic mechanisms can be lock-and-key differences, mating behavior differences, and environmental and spatial differences that keep different species apart.
What are examples of post-zygotic mechanisms of reproductive isolation?
How do species diverge and form new species?
Can be from moving (Allopatric), hybridization (Sympatric), co-speciation, polyploidy.
What are the different processes of speciation (both allopatric and sympatric)?
Dispersal and Vicariance
What would you expect relationships between species to be following a vicariance event?
After vicariance, I would expect daughter species that become separated would maintain similarities.
What is an ecological niche?
Is a certain setting that a species can be filled whether it is a habitat or available food source.
What is adaptive radiation and what is the role of natural selection in adaptive radiation?
Adaptive radiation can show how quickly evolution can occur. When a species spreads throughout different ecological niches, a species in each niche will be a new species that is particularly adapted for that niche.
How can instantaneous speciation occur?
Instantaneous speciation can occur in hybridization, in which two different species produce offspring that can only reproduce with its own new hybrid species and neither of the parent species.
How are parasites and host systems an example of co-evolution? (including malaria – see Case 4)
As a new host species is split from a host population, the parasite that is tied to the new host will be a new species as well. Although with malaria, it is unclear the relationship of the malaria that affected chimpanzees and their most closely related humans.
What is reinforcement and how does it affect speciation?
Reinforcement of reproductive isolation occurs when species undergo natural selection in favor of enhanced pre-zygotic isolation to prevent production of less fit offspring.
What information can be learned from phylogenies?
Phylogenies help us observe how species and might be related and how certain traits may have been passed down from shared ancestors.
What is a sister group? Monophyletic group? Paraphyletic group? Polyphyletic group?
A sister group is two species descended from a common ancestor. A monophyletic group is an ancestor and all of its descendants. A paraphyletic group is an ancestor, and not all of its descendants. A Polyphyletic group includes species that don’t have a shared ancestor.
What is a character and a character state?
Characters are anatomical, molecular, or physiological features based on genetics. Their state is their observed condition i.e. whether or not a trait is present.
What are homologous and analogous traits? How are homologies and analogies represented on a tree?
Homologous traits are traits that are derived from a common ancestor. Analogous traits are similar traits that evolved independently of each other, much like the wings of bats and birds.
What is a synapomorphy and how is this related to homologous traits?
A trait derived from a common ancestor.
How are phylogenies determined, and how is parsimony a component of these determinations?
Phylogenies are hypotheses of relationships between species. Parsimony suggests that the simplest answer, the tree with the least # of changes is the most likely.
How are fossils used in determining evolutionary relationships?
Fossils can help describe the changes in species, particularly over time. They can help show what changes occurred for species and how the environment shaped the different species.
How do fossils form and what biases exist in the fossil record?
Fossils are formed from the remains of organisms in sedimentary rock. Because a certain set of circumstances must be met to create fossils, there can exist a lot of bias as to what is fossilized. If organisms exist in a time where there is not a lot of rock present. Organisms without bone or hard tissue that can be fossilized. If there is an abundance of a certain organism, but that organism cannot be fossilized, then they may not be represented in our history.
How is fossil age determined (both relative and radiometric)?
Fossil age can be determined based on what layer of rock it is in. With a basic understanding of the different layers of sediment and when they existed, we can determine when an organism that is fossilized in that sediment existed. We can also determine the amount of C14 in an organism. With knowledge of the half-life of C14, we can make an estimation on to the age of the fossil.
How do transitional forms found in the fossil record contribute to our understanding of evolution?
Transitional forms can show us the path that organisms evolved in. They can show the gradual transition from long-ago species to what we recognize today.
How have past mass extinctions affected evolution (especially the post-Permian and Cretaceous)?
The post-Permian and Cretaceous extinctions eliminated a significant portion of life on our planet, and with it a significant amount of the gene pool. The Permian extinction eliminated 90% of marine life and opened those previously occupied habitats for the surviving 10%. Similarly, when dinosaurs were wiped out during the Cretaceous extinction, those habitats in which they were predators became habitable by other organisms (notably, mammals)
What is the significance of the carbon cycle to all life on earth?
The carbon cycle is extremely important in showing how energy is transferred from organisms and the environment. It illustrates the main driving factor that determine how organisms interact with the environment.
Explain the short-term carbon cycle – photosynthesis and respiration – and the role of these processes in atmospheric CO2 concentrations.
Photosynthesis consumes CO2 and produces carbohydrates for energy and releases oxygen. Organisms, like humans, consume carbohydrates in an aerobic process (requiring oxygen).
How do we determine recent and historical atmospheric CO2 concentrations, and what is the relationship between these concentrations and temperature?
We can measure CO2 concentrations in fossilized material or in blocks of ice that trap CO2 from a long time ago. The concentrations of CO2 have steadily increased over time. Temperature cycles through different time periods. The concentrations may fluctuate during the year depending on the season. During the summer months, CO2 concentrations decrease due to the increased activity of plant life. During the winter months, CO2 concentrations increase due to the decreased activity of plant life.
What are the major sources and sinks of CO2?
The major sources of CO2 are from the burning of fossil fuels and deforestation. The sinks, or where CO2 accumulates in the oceans, lands, and in the atmosphere.
How does carbon cycle through the earth? What are the major reservoirs and fluxes of carbon?
A major reservoir is in rock, but organisms, the sea, and the atmosphere also serve as reservoirs. The major flux of carbon occurs from sedimentary rock, which is the largest reservoir.
Why are shell-building animals and corals considered a sink of carbon?
They are formed by Calcium Carbonate which form shells and corals.
What are the geological processes involved in the cycling of carbon?
Plate tectonics play a role in cycling carbon. As plates rub against one another, material can enter magma under the earth’s surface and be expelled into the atmosphere through volcanos.
What roles do humans play in the carbon cycle?
Humans respirate, consuming oxygen, and exhale CO2 into the atmosphere. But more importantly, humans burn massive amount of fossil fuels and deforest the earth, creating more CO2.
How does carbon cycle through a community?
As a food web, we can recreate the path that carbon is cycled through a community. It is produced by plants, algae, and photosynthetic bacteria, which is then consumed by primary consumers.
How much energy moves on to the next tropic level and how does this affect biomass of the next level?
As we move through the trophic levels of the pyramid, the amount of energy that is available is roughly 10%
What changes occurred in oxygen levels on earth over time?
Only relatively recently in earth’s history has oxygen been available in an amount that is able to sustain the organisms we recognize today. The availability of oxygen helped with the diversity of life that is now sustainable on our planet.
What are the features of the prokaryotic cell?
A prokaryotic cell has no membrane-bound nucleus and no organelles.
What are the evolutionary relationships between the two domains of prokaryotes and the eukaryotes?
Although prokaryotic cells were originally dismissed as simple, the diversity of prokaryotic cells and abundance of them have shown them to be highly evolved organisms.
How does diffusion limit prokaryotic cell size?
Because prokaryotes rely on diffusion, they tend to be smaller in size. A smaller cell allows for greater surface area relative to the cell size. The volume of a cell increases exponentially faster than the surface area, so a larger cell becomes untenable.
Why is it difficult to use the biological species concept to determine bacterial species and their relationships?
Because bacteria reproduce asexually, the BSC does not apply. Also, it is hard to track species in such a simplified way as the transmission of DNA in bacteria can occur in many different ways, including conjugation, transduction, and transformation.
What are the different approaches to metabolism in prokaryotes (i.e. energy and carbon sources)?
Prokaryotes can be photoautotrophs (acquire carbon from and use sunlight as energy), chemoautotrophs (gain carbon from CO2, energy from chemical reactions), photoheterotrophs (use sunlight for energy, but acquire carbon from chemical), and chemoheterotrophs.
What are the conditions needed for fermentation?
Fermentation will typically occur in oxygen-poor environments, but with a large amount of available organic matter.
How is sulfur cycled through biological systems and why is this important to living organisms?
Sulfur is an important component of amino acids in our bodies. Sulfur is available to us through the things that we eat, which is made available to plants by assimilation. For assimilation to occur, there must be bacteria that can oxidize H2S to SO4. Decomposition and reduction can take the sulfur and convert it to H2s.
How is nitrogen cycled through biological systems and why is this important to living organisms?
Nitrogen is important to the growth of plants and is extremely important in our body as a key component of proteins and nucleic acids.
What is the significance of nitrogen fixation and where does this process occur?
Nitrogen fixation is an important part of the nitrogen cycle in which bacteria convert nitrogen gas to ammonia which is then biologically available to plants, either as ammonia or nitrate. Anammox or denitrification can also take these products and convert them back to N2 gas.
What are the roles of nitrogen fixation and denitrification in moving nitrogen between the atmospheric and biological reservoirs?
Where are the aerobic and anaerobic locations most likely to be in a microbial mat?
Aerobic prokaryotes in microbial mats would most likely be found nearer to the surface, where oxygen is available to them. Anaerobic prokaryotes, which don’t need oxygen to respire will be found away from the surface.
How do scientist determine diversity in the prokaryotes, and what are the challenges?
Because bacteria and archaea separated over a billion years ago, it is hard to determine what traits evolved independently and what was shared over common ancestry. Horizontal gene transfer also complicates the process.
What are cyanobacteria?
Is the classification of bacteria that can perform oxygenic photosynthesis.
How are archaea similar and different from bacteria?
Archaea and bacteria are both prokaryotic in cell structure, but their membrane and cell composition allow for survival in extreme conditions or conditions where energy is less available to an extent where bacteria and eukaryotes would not be able to survive.
What are the extreme lifestyles of the archaea that have evolved? How could natural selection have played a role in the evolution of these extreme abiotic tolerances?
Thermophilic, Hyperthermophilic, Halophilic, and Acidophilic. It is believed that Archaea may have existed in times when less oxygen was available, so anaerobic metabolism allowed Archaea to survive in extreme conditions.
What are stromatolites?
Are essentially fossils of bacteria. They are layered structures that record the existence of bacterial mats.
How is co-evolution of symbiotic prokaryotes with eukaryotes similar and different to co-evolution in parasite-host systems?
Coevolution in prokaryotes and eukaryotes may be much more symbiotic in that benefits are provided to both. For example, the bacteria in the stomach of animals may help make different material biologically available to the animal, while the animal provides a steady stream of nutrition.
How diverse in the microbial community in humans? (also see Case 5)
The bacteria that exists in humans can be very different depending on the region the human is in. This may help our understanding of the development of allergies and immunities.
In what ways can bacteria be harmful or beneficial to humans?
Bacteria is important to help us digest different types of food sources. Bacteria is also responsible for nitrogen fixation to help grow crops.
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