AFAIU, in ‘lower animals’ alternating modes of reproduction are very common. In ‘higher animals’, it’s not so. Has to do with when meiosis happens in the life cycle and what stages are for dissemination. So no, it’s never an accident, but for a deeper reason you should ask someone else.
Not sure what you mean—lots of things are “accidents” in the sense of encoding a possibility that could have gone the other way. Any time a similar type of thing gets reinvented by evolution in a different way, that thing is a type of accident. For example, the vertebrate eye (molluscs use something a bit different), the vertebrate jaw as a modified branchial arch (invertebrates use modified limbs for jaws), etc. etc.
An example of something that I don’t think is an accident is that animals do not photosynthesize. I think this is not an accident because you can’t support the energy requirements of a multicellular thing that moves around on our timescales with photosynthesis—you have to ingest high energy-density things (e.g. other organisms) directly.
Some plants and fungi have alternation of generations, and I think all animals do not. But animals differ a lot from fungi and plants in being highly mobile heterotrophs. I am wondering if something about animal characteristics channels them to avoid alternation of generations, just as multicellular mobility channels them to avoid photosynthesis, or whether it is an accident in the set of protista-like ancestors in the animal lineage. I could certainly imagine an animal with alternation of generations (isn’t that what Giger’s aliens are?)
Ah. Now I see. What you call ‘accident’ I call ‘event’, because such a great thing as alternation has consequences for most areas of an organism’s life. It might have gone the other way, but that it is still so widespread is exactly as accidental as the placement of a brick in the middle of the wall.
If I am not mistaken (I can look it up sometime), practically all plants and fungi have it. In lower animals, some stages of a life cycle can be mobile founders, and later ones would live in tightknit colonies. Asexual/sexual alternation is pretty common, too. See wiki on trematodes.
No idea about Ginger’s aliens, except that they just might be accidentally transmitted to humans when humans eat their ‘rightful’ hosts. Some frog parasites go on living in snakes… (Is that what you mean?)
AFAIU, in ‘lower animals’ alternating modes of reproduction are very common. In ‘higher animals’, it’s not so. Has to do with when meiosis happens in the life cycle and what stages are for dissemination. So no, it’s never an accident, but for a deeper reason you should ask someone else.
Not sure what you mean—lots of things are “accidents” in the sense of encoding a possibility that could have gone the other way. Any time a similar type of thing gets reinvented by evolution in a different way, that thing is a type of accident. For example, the vertebrate eye (molluscs use something a bit different), the vertebrate jaw as a modified branchial arch (invertebrates use modified limbs for jaws), etc. etc.
An example of something that I don’t think is an accident is that animals do not photosynthesize. I think this is not an accident because you can’t support the energy requirements of a multicellular thing that moves around on our timescales with photosynthesis—you have to ingest high energy-density things (e.g. other organisms) directly.
Some plants and fungi have alternation of generations, and I think all animals do not. But animals differ a lot from fungi and plants in being highly mobile heterotrophs. I am wondering if something about animal characteristics channels them to avoid alternation of generations, just as multicellular mobility channels them to avoid photosynthesis, or whether it is an accident in the set of protista-like ancestors in the animal lineage. I could certainly imagine an animal with alternation of generations (isn’t that what Giger’s aliens are?)
Ah. Now I see. What you call ‘accident’ I call ‘event’, because such a great thing as alternation has consequences for most areas of an organism’s life. It might have gone the other way, but that it is still so widespread is exactly as accidental as the placement of a brick in the middle of the wall.
If I am not mistaken (I can look it up sometime), practically all plants and fungi have it. In lower animals, some stages of a life cycle can be mobile founders, and later ones would live in tightknit colonies. Asexual/sexual alternation is pretty common, too. See wiki on trematodes.
No idea about Ginger’s aliens, except that they just might be accidentally transmitted to humans when humans eat their ‘rightful’ hosts. Some frog parasites go on living in snakes… (Is that what you mean?)