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Why do we age is a classical question in Evolutionary Biology. There are several things to consider when we think of how genes that cause disease, aging, and death to evolve. One explanation for the evolution of aging is the mutation accumulation (MA) hypothesis. This hypothesis by P. Medawar states that mutations causing late life deleterious (damaging) ...


39

71% of the earth's surface is taken up by water. Not surprisingly therefore, the seas are an important source of oxygen. National Geographic claims that photosynthesis by phytoplankton (mostly single-celled phototrophs, such as cyanobacteria, green algae and diatoms) account for half of the earth's oxygen production. The other half, they claim, is produced ...


22

This is a very good question. There is a big ongoing field of research called "evolution of aging/senescence" that tackles this question. I won't give you a complete overview of the different hypothesis the could explain why we age but here is a fundamental concept that is to know. We'll assume that there is some extrinsic mortality, mortality against ...


17

Short answer Between 62,000 and 63,500 feet (18,900 and 19,350 meters) blood begins to boil at body temperature. This altitude, referred to as the Armstrong limit, is generally considered to be the absolute limit compatible with life. At this point, humans cannot survive without pressurization measures. Background Atmospheric pressure drops at higher ...


14

Because evolution isn't about individuals: it's about species. What matters to natural selection isn't how long you live, but how many grandchildren you have. A long lifespan can be an evolutionary advantage, but like any trait, it's only an advantage to the extent that allows you to reproduce more. It would seem that a longer lifespan would be advantageous ...


13

Actually, genetically, there is no reason for animals to continue to exist after they have procreated. If you look at salmon, they die immediately after procreating, which is probably the most efficient way to carry the best genes to the next generation. In the case of mammals, they need to teach their offspring where to find food, where to find water and ...


12

According to a number of citations listed on Kenyon College's MicrobeWiki, rain can contain microorganisms via a process called "bioprecipitation." Essentially, microorganisms, dust and other small particles get swept up into the atmosphere, and cold temperatures cause atmospheric water vapor to freeze around the organism/particle. Once the ice-covered ...


9

I am not sure which class of organisms have the highest contribution in oxygen production but diatoms do have a significant contribution. The introduction in this paper says that diatoms account for 40% of marine photosynthesis which according to this site is "1/4 of the oxygen we breathe."


8

There were some experiments done in microgravity in longer space shuttle missions. The reports show that the fungi develop relatively normal but grow in random orientations instead of orientating upwards. See this images: The upper image shows fungi grown on earth which are subjected to normal gravity. The lower image shows fungi (actually only the fruiting ...


8

Following from MarchHo's comment, I have not been able to find class-specific (in the formal sense) estimates, but if you meant 'class' in an informal sense, the following may be useful. A nice infographic covering the relative biomass of all land mammals is here, and a full table for species groups (at the level of domesticated vertebrates, invertebrates, ...


8

Polar bears (Ursus maritimus) have white fur all year long. There are probably several other examples. @L.Diago gave sheep as example. There are also all white troglodyte species.


7

Months to years - although the actual duration in a specific environment depends on the nature of that environment and is tied to oxygen level. Higher oxygen, faster degradation. Less oxygen, the estrogen molecules interconvert among various closely related molecules which hampers both their detection and their degradation. For more info, please see: ...


7

If you take the line of "The Selfish Gene - Richard Dawkins". Evolution doesn't care about individuals, it cares about genes. So as long as the genes are passed along reliably into the future, evolution may do it with 4 generations per 100 years or 100 generations per 100 years.


7

Trees are definitely not the only source of oxygen. First, all green plants do photosynthesis, not only trees. Moreover, about half of all photosynthesis on earth is done by microorganisms in the oceans known as phytoplankton.


5

To an extent it does; in that we live longer than our mouse-like ancestors. So the question becomes: why not keep extending it to immortality. The key thing is that evolution cares only about the survival of your genes; so if you live for 1000 years or if 10 generations of your family have 1 individual's worth of your genes in each generation (each living ...


5

There is no selection mechanism that would favor high age. By the time it's apparent whether or not an individual can reach a high age healthily, they'll have ceased all reproductive activity. Conversely, people who get cancer at 45 will have likely reproduced already.


5

Ignoring for the moment the question of politics, let's consider the various definitions of the term "invasive species" that are in use. Colautti and MacIsaac write in their discussion of invasive species terminology (1): The greatest confusion [among the discussed ecological terms] surrounds the common term ‘invasive’ and its various derivatives (...


5

The cost would increase; either because pollination services are not provided and the supply is decreased; or because the cost to producers goes up as they must pay for artificial pollination. See the extremely detailed analysis in Winfree et al. edit I imagine what you're actually asking for is a $ figure "per apple". This depends on the location, crop, ...


5

The roots do actually continue to hold soil without being alie. The stabilizing properties are structural in nature. You begin to lose those though as the roots decompose, and the important roots against erosion, millions of fine root hairs, will go first. But leaving the roots in on a dead tree will help for a bit, but isn't a long term solution.


4

The problem is not really that we don't understand some stuff (lthough this is certainly true) but that an ecosystem, or the biosphere is a highly complex network of interactions. This network is continuously displaying some chaotic (determinist but not foreseeable) behavior. In such a system it becomes very hard or practically impossible to predict what the ...


4

There can be perhaps 10 trillion rodents and bats on the planet, so the humans and livestock probably are small compared to a rainforest rodents and bats. The biggest bat colony is 40 million, they decline without unmanaged forests, can reach 4-10 bats per hectare, and the world population might normally be in 10s of billions, save for the use of pesticides ...


4

Here’s how it works. Every morning when the sun breaks over the horizon — no matter what time of year it is — a clock starts ticking inside the trees. After a specific number of hours, the plants’ cells start producing high levels of a molecule known as the FT protein. This protein is responsible for initiating processes that help the plant grow. But the FT ...


4

The classical division of humans and animals has always been self-centered and artificial. Humans are animals, competing with other organisms under exactly the same rules. Evolution involves trade-offs, strategies, and adaptation. Humans have been set on a path to use their brains to compete, rather than claws. But the concepts are the same. It happens that ...


3

I am assuming that by longer life, you mean slower aging, because evolution can do little if a mountain falls on a person! So, why don’t organisms have slower, or better, zero rate of aging? The theory I am describing is based upon life history theory. Life history theory assumes that: Resources available to any organism are limited, Life processes like ‘...


3

If I understand your question correctly, I've seen this idea in many papers, sometimes stated clearly and sometimes in more implicit terms. After a quick look I found a paper which should be relevant as a starting point for you: Mayor et al. 2007. Spectrum of selection: new approaches to detecting the scale-dependent response to habitat. Ecology 88(7). In ...


3

Remi.b's answer is spot on - predicting the effects of losing a given species is nigh on impossible. However, I do think that there are some general trends that can give us some intuition, and make the campaign to protect certain species more than just an ethical issue. Biodiversity (i.e. having a wide range of different organisms (and genetically diverse ...


3

Most animals are not well adapted to deal with avalanches. For example, more mountain goats are killed by rock slides than by predators. http://www.nationalgeographic.com/lewisandclark/record_species_150_11_2.html Meanwhile, a mountain at risk of snow avalanche must be deep in snow, right? At that point, there is very little food to be found; it's all ...


3

Many organisms including plants, bacteria, insects, fishes and even mammals have been GMed. Most of them have experimental purposes, but GM crops have been released for commercial purposes. Maybe the most amazing between them is triticale, which is a hybrid of wheat (Triticum) and rye (Secale). Triticale, BT Potato, BT Tomato, BT Maize (I am not sure), BT ...


3

From an ecological sense, cycles of living beings are intertwined. Breaking cycles affects life being able to live, reproduce, and die in a manageable way. Insects, animals, and plants help feed each other and help them reproduce. Fewer insects are less of a food source for animals and can't pollinate plants as much. Reduced animal populations are less of a ...


2

Calories and dollars are the most obvious and straightforward, but including additional variables complicates the accounting. . A great paper that used energy has been updated in a more recent publication. Emergy is an interesting alternative. Current work includes the Natural Captial project that "aims to integrate the values of nature into all major ...


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