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Should human beings be considered a nonnative (invasive species) or a "keystone species?" In your explanation please use at least one example of a nonnative species to and one example of a "keystone" species to help illustrate your point. Show why humans do or don't act as invasive or keystone species. Use specific behaviors and impacts in your answers. Limit your response to no more than 500 words.

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Casey Durgan
Casey DurganLv2
28 Sep 2019
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22. What are the major carbon sinks and sources on earth?

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25. How do we know that global warming is and will have animpact on populations, communities, and ecosystems?

26. Given what we know about Japanese knotweed, global change,and human activity, explain the interactions and consequences ofJapanese knotweed invasion on our water supply. You need toinclude, the physiology of the plant, the population ecology of theplant, the water cycle (ecosystems), and global change.

27. Regional climate change models predict that this area willget warmer and receive more rainfall. They also predict thatagriculture (i.e. growing plants) will suffer. Explain why. Becomplete in your answer. There are several factors at workhere.

28. Why are sea-levels increasing globally? Give a detailedanswer. What are some likely consequences going to be (other thanlosing land).

1.

An area has two different Anopheles species, both of which can vector Plasmodium, although Plasmodiumdevelops best and is transmitted best by species B. Species A is dominant because its larvae outcompete species B in the main shared breeding sites, small lakes and ponds. Therefore the population of B is currently small. The small lakes and ponds are also the source for the main food source in the region, fish, grown in fish farms. There is grazing land, but other than chickens, the local population does not have livestock. Species A is largely endophagous and endophilic, species B is exophilic. In other sites, both species A and B will also feed on cattle, and B appears to prefer cattle. Both species also like to roost during the hot day in rock overhangs and small caves. To give some context to your answers use the IPM terminology considered in class.

A) The national malaria control agency sends in a new person to develop a malarial control strategy. (S)he recommends oiling the lakes and ponds, and intensive house spraying . Discuss why each of these two options would be a good or bad idea. In your answer consider effects on species A, species B, and malaria incidence. And remember, the idea is to help the local population.

B) Develop an alternative targeted strategy that might work well in this situation. Explain why this would be a good fit. Use only strategies that have been used successfully in the field, and avoid "just spray everything" strategies. Explain why your strategy should work.

2.

After roughly 15 years we have the first malaria vaccine going into phase 4 trials. Meanwhile a Zika vaccine is starting phase 2b trials, only 2-3 years after the first major outbreak in Brazil.

A) Discuss in some detail why it is so much more difficult to develop a vaccine for malaria than for e.g. the Zika or rubella virus. I am looking for at least 2 reasons, and a brief explanation of those reasons. Just stating that one is complex and the other simple is insufficient. If that is what you want to say, back it up with facts.

B) Both the CRISPR bacterial defense system and the adaptive immune system in mammals have means to recognize “signatures” of invading organisms. In what way are the two systems different?

3.

The malaria control team in a given area has access to 5 different drugs, chloroquine, mefloquine, pyrimethamine, amodiaquine, and artimisinin. Nothing else will be available for the foreseeable future. Some resistance to all 5 is already observed.

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For years we have been able to analyze the fossils of extincthumans like those of Neanderthals. Their bones gave us clues to howthey looked, how they lived, and how they might be related to us.In the last few years, we have been able to get a better view intothese extinct species and their relationship to our species. Thanksto next generation genomic sequencing technologies, we have beenable to obtain genetic data on Neanderthals, Denisovans and othersthat have allowed us to make direct comparisons between our speciesand theirs. In addition, we have been able to observe the presenceof DNA from these extinct species within our own genomes which tellus that we had kids with these now extinct humans.

If we take Neanderthal DNA as an example, we find that we share99.5 percent of our DNA with them. Which means that we andNeanderthals were separated from each other for more than 500,000years. This also means that we were genetically similar enough tobe able to have offspring with each other. We see evidence of thisgenetic introgression between us and Neanderthals when we look atour DNA. Interestingly, if we obtain one thousand DNA samples fromGrossmont College students, we estimate that we would be able toextract at least 20% of the Neanderthal genome from them. Thismeans that 20% of our collective nucleotide sequences are sharedwith Neanderthals but this doesn’t mean that 20% of our genes areNeanderthal specific genes. Of the twenty-one thousand genes thatNeanderthals had, only a few dozen of their genes survive withinour genome. The same holds true for Denisovans. What is moreinteresting is that older versions of ourselves have a tendency tohave higher levels of DNA from extinct humans compared toourselves. In other words, over the course of thousands of years wehave been slowly weeding out the DNA of the other humans from ourgenome in favor of our genes.

One basic question that we might like to ask is why have we beenlosing Neanderthal and Denisovan genes over time? Also, why do westill have a significant amount of DNA segments that don’t seem tobe going anywhere? The answer to this has to do with selection.

The answer to the first part of the question has to do with thefact that we were not fully genetically compatible with the otherhuman species to begin with. Basically, to have had Neanderthal orDenisovan genes in the past meant that an individual's level offitness was reduced. To get rid of their genes in favor of our ownwould mean that the relative fitness of individuals would increaseovertime.

The answer to the second question has to do with the fact thatDNA segments from Neanderthals and Denisovans that did not code forproteins remained because there was little selective pressureagainst them. As far as genes are concerned, the only Neanderthaland Denisovan genes that remain only exist because they had aselective advantage or at least have been neutral to ourspecies.

DNA segments that that were neutral or that had a selectiveadvantage, whether genes or not, simply remained because they wereadvantages or there was little selective pressure against them.

Your task for this week is to look for information about oneNeanderthal or Denisovan gene that survive within our species andto tell me what function that gene has and how that gene mayincrease the fitness of modern human populations.

  • In your post, discussONE Neanderthal orDenisovan gene that is currently found within our species.
    • Tell us about the gene and its function. Explain what it doesfor us. (Make sure you give a citation.)
    • Explain in your own words any possible advantages that yourNeanderthal or Denisovan gene might have. Make sure you give ininformed opinion that is grounded in your research.

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