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Genes, Ecology, and Evolution Final Exam
Terms in this set (6)
Briefly describe five ways in which equatorial rainforests are similar to coral reefs.
1. Both equatorial rainforests and coral reef biomes possess light as a limiting factor for both environments. Many organisms within a rainforest compete for light, which is very limited and creates high structural complexity within the rainforest. Similarly, the photic zone of a coral reef biome has great structural complexity as many organisms utilize this zone for light consumption, which also increases the competition for light as well.
2. Both equatorial rainforests and coral reefs have organisms that contain high apparency, like bright colors and complex structures that aid in reproductive fitness. The zooxanthellae that produce chlorophyll for the coral reefs and the presence of bright feathers in a rainforest bird species work in the same way of attracting/keeping a mate to enhance their genetic diversity and capacity to reproduce.
3. Both equatorial rainforests and coral reefs are being converted due to environmental and human factors. Rainforests are being demolished due to logging and agriculture expansion, which is producing a negative impact on the environment and decreasing the production of oxygen within our atmosphere. Similarly, coral bleaching is being brought upon by increasing temperatures due to an increase in nutrients from agriculture and deforestation. In the same way as rainforests, the death of coral is contributing to an unfavorable oceanic environment and decreasing the health of Earth's atmosphere.
4. Both equatorial rainforests and coral reefs are the main biome contributors for photic productivity. Coral reefs are right under rainforests in photic productivity in which reefs actively remove CO2 from the atmosphere and create calcium carbonate structures beneath the water which resembles an ecosystem service. Similarly, rainforests adopt high complex 3-D structures to induce the most favorable structural variations for maximum photic productivity.
5. Both equatorial rainforests and coral reefs are located near or close to the equator which contributes to increased temperatures and continual warming effects. Organisms within both biomes can be affected by the warming temperatures, producing significant changes within their habitats and may alter their genetic diversity within populations.
From the BIOL 214 lectures and assigned materials, describe three examples of phenotypic plasticity. For each, mention the key environmental factor or factors influencing the trait (or traits).
1. Dramatic changes in Tundra day length induces phenotypic plasticity in Tundra organisms. Year-round arctic organisms use day length to modify their physiology and utilize the lengthening or shortening of days as triggers to recognize if summer or winter seasons are approaching--photoperiodism.
2. Ephemeral plants within the Desert biome exhibit phenotypic plasticity. Unfavorable conditions such as the onset of a drought or an increase in temperature trigger the ephemerals to go through their very short life cycle in order to produce seeds that can go dormant until favorable conditions return until they germinate to produce the next generation of ephemerals.
3. The co-evolution of large carnivores with large herbivores in response to the savanna environment is also an example of phenotypic plasticity. When the biodiversity increases for large herbivores when savanna biome conditions are favorable, the body size of carnivores will also increase in response to biodiversity of the herbivores.
From the BIOL 214 lectures and assigned materials, describe three examples of evolutionary trade-offs. For each, mention the key biotic or abiotic factors that influence the fitness of a phenotype or genotype.
1. An example of an evolutionary trade-off would be the value of red coloration in northern cardinal males. The red coloration suggests a cardinal male is sexually mature and thus increases reproductive fitness. Although, the trade-off is imposed by the cost for cardinal males to have this red coloration by the increase in predation due to a decrease in camouflage.
2. An example of an evolutionary trade-off is the relationship between the sloth and their defecation behavior. The benefits for sloths to defecate on the ground are the photosynthetic algae that clings to their fur to provide a food source and camouflage as well as the moths that lay eggs in the sloths feces that remain on the forest floor. Although the trade-off for these mutualistic relationships is the increased mortality of sloths from exposure to ground predators that would otherwise not be able to reach the sloths if they remained in the treetops. This ultimately reduces the survival fitness of sloths to escape predators and survive to produce the next generation.
3. An example of an evolutionary trade-off is the Asian gerbil and its ability to survive extreme conditions without sufficient food, water or shelter. The excess of brown fat and thus mitochondria in addition to increased microvilli present in their small intestines provide the gerbil with the opportunity to eat their feces and survive on ephemeral plant seeds. The trade-off is imposed by the fact that gerbils are more sensitive to toxins from food or waste, so even though their diet can consist of a wider variety of resources, their ability to survive from contamination is greatly decreased. This affects changes in gene expression along with survival fitness.
From the BIOL 214 lectures and assigned materials, describe three examples of convergent evolution. For each, mention the key environmental factors leading to selection for a particular trait.
1. Convergent evolution is expressed in gain of function viruses or superviruses. Convergent evolution is exhibited as a virus becomes more virulent in the wild strain versus a virus become more virulent in the lab strain. Comparing the two pathways to increased virulence and their ability to independently evolve similar traits is the key to determining the selection for the more virulent strain.
2. An example of convergent evolution is the relationship between sugar gliders and flying squirrels within the equatorial rainforest biome. Both organisms have developed the ability to move habitats and escape predators through flying and gliding. Although, these species are not evolutionarily related, but morphologically related, which is a key characteristic of convergent evolution when comparing both of these organisms' ability to enhance their survival fitness through advantageous movement throughout the rainforest's complex structure.
3. An example of convergent evolution is the development of the stomata within desert plants. The desert plant stomata has evolved the capacity to open or close in order to allow the passage of gases throughout the day to aid photosynthesis. Desert plants will have their stomatas open at night during lower desert temperatures and closed during the day to avoid major water loss within the plant. This action of convergent evolution between the plant, stomata, and external temperature has increased the overall survival fitness of desert plants.
From the BIOL 214 lectures and assigned materials, describe three instances in which changes in cis-acting regulatory DNA sequences were critical to an important evolutionary outcome.
1. Because DNA polymerase can make mistakes through errors in replication that would otherwise be incorporated into the incorrect DNA strand, certain mutations in LUCA, contained within cis-acting regulatory promoter regions, were put in place to decrease the high error rate in early evolutionary organisms. Such modifications to the promoter region included the incorporation of several adenines and thymines which prevailed in our ancient ancestors and modern organisms. Species that lived in extreme heat environments would have encountered denatured DNA due to the double bonds of adenine and thymine unwinding quicker than those of guanine and cytosine, so the ultimate advantage of the adenine and thymine promoter region would be a bubble region for RNA polymerase to bind for DNA transcription.
2. The developmental pattern of the lactase gene is reflected by a protein that binds to a DNA regulatory sequence in order to induce lactase transcription, but is labelled as a negative regulator protein and therefore keeps transcription of lactase at low levels. Although, some individuals have a mutation within the binding site in the regulatory sequence which causes no repression of the lactase gene and continual expression. This change in a cis-acting regulatory sequence has led to favorable selection for individuals with the lactase persistence allele, or those who possess "lactose tolerance" and can thus pass on the favorable trait to the next generation to allow their offspring opportunities to consume high quality food and survive through all seasons.
3. Eukaryotic genes contain intron excision, along with spliced-together exons and promoter sequences. For specific sets of mRNA like the lac operon, the regulation of transcription involves changes in promoter and regulatory elements. Modern organisms have developed the ability for coded binding sites on DNA transcripts to allow access to only certain molecules or proteins, specifically glucose or lactose for the lac operon. The genetic changes that have occurred in the lac operon regulatory sequences have modified the way lactose is digested in modern organisms and the way it is controlled to maintain mRNA transcription and simply keep the organisms from developing negative effects if the binding sites and proteins were not absolutely specific to one another.
From the BIOL 214 lectures and assigned materials, describe three instances in which changes in amino-acid encoding DNA sequences were critical to an important evolutionary outcome.
1. When rhizobium bacteria invade legume plant root hair, the plant cells will change their gene expression in order to produce hemoglobin to bind up oxygen for nitrogen-fixation. Because nitrogen-fixation cannot occur when oxygen is present, the rhizobium-legume complexes provide the correct environment for an oxygen-free fixation and lots of energy for the rhizobia bacteria. The outcome of this encoded DNA sequence change has created an evolutionarily significant complex that propagates a mutualistic relationship between two different organisms.
2. Molecular spandrels contain significant changes in DNA sequences that have contributed to evolutionary outcomes. If there is a selective pressure for darker color in Tundra mammals, a genetic change in the transcription factor gene will control the outcome for the selective pressure for darker color. The change in DNA sequencing of the transcription factor gene will increase in order to produce a downstream effect for darker color on the color-controlling gene, but will also have an effect on the limb length gene if they are encoded on the same area of an mRNA transcript. This creates a significant genetic change in response to the desired selective pressure, but also a by-product from other sequences of coded DNA.
3. Another example of when a change within an encoded gene sequence can affect the outcome of gene function and what the gene accomplishes at the biochemical level is pereskia and cacti. Both desert plants have spines along their bodies, but going from a pereskia plant to a cacti plant would be a change in gene function based off of a change in the coded DNA sequence. Furthermore, transitioning from bark to stomata would be a change in gene expression because the bark gene will ultimately be shut off in the modern evolutionarily advanced cacti plants as compared to the pereskia plants which contain genetic coding for bark.
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