General > Biology
Sexrepro (Real Life) questions
Numsgil:
The Cambrian Explosion, the time when multicellularity developed and the number of species exploded in number, had a number of relatively simoltaneous (at least, that's more or less the concensus as I understand it) advances:
1. Eukaryotes. Both much, much larger than regular bacteria and more highly organized.
2. Eukaryotes gain mitochondira. Basically symbiotic bacteria that live inside cells and help them metabolize.
3. Sexual Reproduction.
Maybe a few others. This is an area of active research, so it seems alot of what I thought I knew seems to be becoming obsolete :/
shvarz:
Many genes try to cheat and reproduce themselves to higher frequencies in population, both from males and from females. In females there is huge conflict between the two X chromosomes, because one of them gets permanently shut down. Also, when an egg is formed in females, only one of the X chromosomes gets picked and so there are genes which move the chances away from random for that too.
Ramiro:
--- Quote from: Endy ---How come sperm don't asexually reproduce themselves. Wouldn't that make it more likely that their own individual traits would be passed along the line?
--- End quote ---
Basically there are two types of cell division MEIOSIS and MITHOSIS. The first produces cells with one copy of each chromosome from mother cells with the two copies, thats the way sperm cells are made. As they have ONE copy of each chromosome they can no longer make Meiosis. They could still make mithosis but for that they should make a copy of every one of their chromosomes and they simply do not have enough energy to do that, they are built to the sole purpose of swiming
Brwagur:
Sperm cells are basicly a nucleus surounded with a plasma membrane, I dont think that there is any room for any other organelles besides some mitochondria so I dont think that it can produce enough proteins, ect. for it to divide or even survive for any extended period of time.
MacadamiaNuts:
--- Quote from: Testlund ---Maybe we should ask why there are multicellular organisms at all?
--- End quote ---
My guess is that big cell concretions created a microsystem where cells that were trapped inside had to find a way to adapt and 'steal' what they needed from the lucky outer cells. If they didn't do that, they would have died while only the layer of cells in the surface kept living, like corals and stromatolites. During harsh conditions, it helped them too by letting the outer cells die while keeping a benign enviroment inside.
All our cells carry the same DNA, so we are a big concretion of conspecs that use gene switches to choose a proper function depending where they are in the system.
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