The atmosphere sure changed a lot because of life, which might have had its effects on incoming solar radiation? Which might have changed the temperatures of some ocean currents/continental plates? I donโt think it would differ significantly
I know that DNA encodes proteins. Truthfully, everything besides that (including โwhat are proteinsโ) mostly wooshes over my head, but thatโs not relevant because whenever I search this question I never even find it addressed anywhere....
I recently had a course in developmental biology and this is what I can remember the best:
From the moment of fertilization, the egg has a โpolarityโ, thus a direction like up and down, left and right etc. This can be established by e.g. the entry point of the sperm or protein produced by the mother in one side of the egg. From here on out protein gradients and interactions on cell membranes specify where cells are and thus what kind of tissue they should become
This early polarity leads to a certain pattern of cell division. An important part of this is the folding in of tissue layers called gastrulation, creating the beginning for the gastrointestinal tract.
In vertebrates a streak starts to form in the embryo. This is the start of the vertebrae and the neural tube in it. Also blocks of cells called somites start to form. These blocks are very important for all kinds of tissues in the body.
Hox genes make the cells in somites get an identity like head, arm etc. So in the end Hox genes are probably what you are looking for. If leg Hox genes are expressed where fruitfly normally have antennae, you get this horror:
Iโd guess no, the number of digits and limbs is conserved very well across tetrapods (itโs in their name after all). Fucking with the amount of limbs will probably lead to some developmental errors in the early embryo.
Image description: Pokemon card showing an agressive goose. Powerups: Intimidate, can only be activated during spring. Show those heretics whoโs boss. Deal 1 extra damage for each month the opponent has been out of combat. Shit everywhere, you only eat grass but you are not very good at digesting grass. Deal 20 extra damage to...
If life never emerged on Earth, would the continents still be more or less the same today? In other words, does life affect the formation and movement of continents significantly?
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How does DNA decide the shape of the body?
I know that DNA encodes proteins. Truthfully, everything besides that (including โwhat are proteinsโ) mostly wooshes over my head, but thatโs not relevant because whenever I search this question I never even find it addressed anywhere....
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cross-posted from: lemmy.world/post/14623597
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