Tag Info

Hot answers tagged

30

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) ...


12

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 ...


10

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 ...


9

The definition of life is a controversy in itself, and as it is simply a word that can be understood by everyone however they wish, there is no "correct" definition. It is thus not really possible to give a "correct" answer to your question, but here are a list of things you may want to consider: Replication of DNA is probably the most agreed common ...


9

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 ...


7

Depends on what kind of life you want! The Database of Essential Genes lists genes essential for life for a number of species, although I would be wary of some of the numbers; bacterial results are probably more reliable but it lists 118 for humans and 2114 for mice. There are a bunch of different numbers for different E. coli strains, with larger numbers ...


7

How can really even draw a defined line of what life is? It's easy, really: just make one. In the answer I linked to I go into the reasons why viruses aren't alive (spoiler alert: no ribosomes) and what our current definition is, but the bigger question is why does it matter? We can draw the line wherever we want to, but it's still an arbitrary ...


7

The definition of life is the main issue here. That is one of the great philosophical questions in Biology (and not only Biology) and is way beyond the simple Q&A format of this site. However, most definitions of life can be boiled down to1: A self replicating entity that interacts2 with its environment. Or, even more simply [1]: Life is ...


5

In men, gout is associated with a higher risk of death from all causes. This would imply that their life expectancy is shorter. From a review by Kim et al. (1): Among men who did not have pre-existing coronary heart disease, the increased mortality risk is due primarily to an elevated risk of cardiovascular death, particularly from coronary heart ...


5

It may never have happened again, however, since all lifeforms on Earth today are similar on a molecular level (DNA), suggesting a common origin. An important distinction to make here is that all extant life on Earth has a common origin. It's completely possible that abiogenesis occurred many times, but whatever organisms emerged as a result became ...


5

OK, so we know a couple of things about life in the universe. Note, however, that this is not really an answer and is also not very biological in nature. So, we don't know how life began on the Earth. However, do know that: (1) The probability of life evolving on a planet in the universe is non-zero (since we exist) and, (2) So far, we have not found ...


4

...many biologist/scientists say that viruses are not living because everything they do is just chemicals carrying out their predefined chemistry. I don't think that's correct. Many definitions of life exclude viruses because they lack the apparatus to perform the life functions themselves, especially reproduction. They don't seem to qualify as ...


3

You're probably thinking of the Spiegelman Monster. It was actually discovered in 1965, but it was discovered that it became shorter over time in 1997. It also wasn't included in that thread, and it has a strange name. http://en.wikipedia.org/wiki/Spiegelman_Monster


3

I wouldn't say that there is an established protocol - claims of alien life are not commonly testable or even legitimate - but if something were discovered and deemed "alive," a fairly good sign it was alien would be if its genetic makeup were based on something other than DNA or RNA. That would be a dead giveaway the organism had side-stepped every known ...


3

There are wikipedia pages on Geological history of oxygenation and on Great Oxygenation Event I don't know much about geology and someone else might be able to give an exhaustive list of evidence (and method of measuring) concerning the oxygen concentration on earth but that would be a very long answer I guess! Rather than a full answer, I give you a list ...


3

According to this, 1.2% of stars have planets that can support life. According to Google, there are 300,000,000,000 stars in the Milky Way. That means 3,600,000 stars can support life. Each of these stars is estimated to have 1-2 planets that can support life. For the sake of simplicity, I'll use 1.5 to represent this, since it is the average of 1 and 2. ...


3

Yes. The Bristlecone Pine, Pinus longaeva, is one example. This species boasts the oldest individual living organisms, and also has been convincingly argued by Lanner and Connor (2001) to show no evidence of senescence. While the Wikipedia page on Biological Immortality (as of June 2013) unfortunately ignores plants, the pages on Negligible Senescence and ...


3

Its not scientifically or logically possible to say 'this is impossible' but since this is a speculative question, I'll hazard an opinion. I'd like to argue that, at Earth standard pressure temperature and atmospheric conditions, C H O and N are not really replaceable. Throw water into the mix as the most common liquid and replacing any or all of these ...


3

News to me is that about 4500 of the 4900 minerals on Earth have been created by life. After reading the article, this isn't what was said. What was said is that life increases mineral diversity on a planet, most notably through biproducts reacting with existing minerals (like Oxygen - a biproduct of photosynthesis - reacting with iron to create ...


2

I now found this Wikipedia article on biological immortality. It's pretty much what I was looking for. Wikipedia describes the phenomenon as follows: Biological immortality refers to a stable or decreasing rate of mortality from cellular senescence as a function of chronological age. Various unicellular and multicellular species may achieve this ...


2

In a word, no. There are some good chemical reasons to expect all life to be carbon-based. Of course, it is no longer a silly fantasy to imagine an artificial intelligence that might qualify as life. (Still FAAAARRRR in the future, though, if ever.)


2

Every species has the ability to reproduce. Of course, individuals within a species can be born with a mutation that keeps them from reproducing, or lose the ability to reproduce at some point in life. However, to say that once these individuals fail to meet that criteria they are no longer forms of life would be a fairly absurd semantics argument. It ...


2

This is the sort of question that should be considered from more than one perspective. Since this is speculation, take it as a given that there is a lot of 'what if' here. I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen. If only plants were left on earth, ...


2

First, you'll need to give a good definition of life, because biologists actually don't have one xD. Second, the life as we know merged only after a huge period of time (hundreds of millions of years), wich we obviously cannot reproduce in a lab. Third, even if some kind of protolife would appear at some point, it would still have to fae the competition ...


2

I am not sure I'm providing the kind of answer you would expect. Your question is very conceptual. For such question it is important to very well define the concepts you're using. For example, the concept of species is not well defined (and will certainly never be well defined as it does not represent a natural category to my point of view). Also, the ...


2

The issue I suspect you are struggling with is the anthropomorphization of the evolutionary process. Evolution is an optimization process driven by random mechanisms...i.e. there is often not a "reason" for why certain things are the way they are. Evolution is not a conscious "designer" that produces things with a specific goal in mind...it simply "picks" ...


2

All of your reasoning is correct - viruses are not motile (i.e. not self-propelled). I don't understand why you think this would cause a difficulty in the case of bacteria. Edit in response to comment @Remi.b Some cursory research on estimating probabilities of collisions between particles engaged in random walks has revealed some very challenging maths. ...


2

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.


2

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.


2

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 ...



Only top voted, non community-wiki answers of a minimum length are eligible