I was debating this with my Biology professor earlier.  He told me to post it on here becuase he doesn't know either.
121622
It is due to natural selection. Those of us who can breath oxygen without suffocating survive and those who can't die.
557736
There are many hundreds of thousands of species of unicellular algae that reproduce sexually. \n\nWe have some fossils of brown algae that were in the process sexually reproducing dating back to well before the first multicellular life evolved. We know this because such alage produce silicons 'skeletons' that preserved their structure. \n\nSo we can be absolutely certain that the first sexually reproducing organisms weren't multicellualr.\n\nAs for which the first were, we really can not know. It's almost impossible to tell from fossils whether how a unicellular organism reproduced if it doesn't produce a solid skeleton, and solid skeletons evolved late.
523747
i think that if you categorise it  under physics/biology/chemistry, you might get a better response.\n\nnevertheless:\n\nhttp://school.discovery.com/homeworkhelp/bjpinchbeck/bjscience.html
47753
http://pubs.acs.org/cgi-bin/abstract.cgi/jafcau/1953/1/i03/f-pdf/f_jf60003a008.pdf?sessid=6006l3
502218
Mitochondria are believed by Lynn Margules to have decended from ancient prokaryote because they have their own DNA different from you own( it is the same with cloroplasts). They help out cells turn food into more useable energy for our body. i dont know if their shape changes sorry about that i think im learning it next week
499435
My best guess would be that the chloroplast would be marked as \n"non-self" in the cell and would be degraded in the lysosome. It would be might complicated to keep the chloroplast from being degraded.
431532
This is not an idle claim.\n\nW.r.t. that specific claim about similarities between the DNA of humans and bananas in particular, I found both creationist and scientific references that attribute that quote to distinguished UK Zoologist, Sir Robert May in New Scientist magazine (July 1, 2000).  Unfortunately, I'm not a subscriber to the magazine so I can't get the full article.\n\nBut I found a nice article that explains well what it means when we talk about (and quantify) similarities between human and plant DNA.  For example, the author (geneticist Flo Pauli from Stanford) shows side-by-side human and plant genetic sequences for a protein used in cell respiration found in both plants and animals.  The similarities are shown in red and you can see that there are lots of differences, but also a lot of long sequences in common. \n\nhttp://www.thetech.org/genetics/ask.php?id=83\n\nThis does not make the human and chimp similarities irrelevant at all ... it strengthens the idea that *all* living life forms are related by common descent.  The more recent the common ancestor, the higher the percentage of shared DNA.  This is completely independent evidence of the theory of evolution, which was formulated long before DNA was discovered.
628685
That is unknown, nobody here knows to answer that,you will hear stupid answers and imaginations. Even the scientists don't know.
448189
Your question requires more knowledge of science and genetics than I have.  However, since you haven't received much help with it I thought I would give you a couple of sites.  Try these - they may be of some help to you.  Sorry I couldn't help more.
142437
I think that the notion of parthenogenesis is long obsolete and it is considered a fallacy by the scientific community. Maybe you mean something else?
586343
I don't know how breif this is...but check out this site:\n\nhttp://en.wikipedia.org/wiki/History_of_biology
223478
I'm not sure it's a known thing. Also it seems to be a construct like a ribosome.
73239
This doesn't really belong in Earth Sciences.  Biology or Botany are more specific categories for questions about living matter.  However, I'm in a good mood because it's Friday.  Check the link.
672052
I have studied this topic for nearly 4 years. I believe it is less than 7,000 years. I had trouble with this until I saw how things are dated. Then I knew that there was no "proof" of anything over  about 5500 years old. Every thing over that age, whether 20,000 years or 4.5 billion years is speculation. I have worked in the science industry for about 30 years. I know my way around a lab. I certainly don't know everything, but I know these old dates given to fossils and rocks are speculation. Recent discoveries in DNA and Micro-biology have placed serious doubt in a lot of scientist minds about evolution. I know for a fact that creation is debated by scientists daily. Many can no longer support theories once held by the majority.
288551
In biology we like to have lots of names for the same thing. I think it's just to confuse students!
375103
http://biology.about.com/\nI don't know what your scope is. \nThat site is a very great and big source of biological knowledge. There are so many topics and I hope you will find it useful.\nGood luck!
491103
just an fyi, in genetics one cannot OBTAIN new information, it must be handed down. therefore you can only lose information(de-evolution?). meaning reptiles that dont have genetics for wings cannot randomly grow wings someway down the line.\n\nmy favorite argument is, they dated the earth to be what some odd billion years old? 65? what happened 20 billion years before? if they found this by carbon dating, then how did the carbon have a start? how did it start? how come it just randomly started aging 65 billion years ago if its been around forever? does this rock GAIN more "life" ?