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/sci/ - Science & Math


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>> No.16023285 [View]
File: 198 KB, 1411x833, spiders.jpg [View same] [iqdb] [saucenao] [google]

is insect a case of gene loss? originally same genes as humans but they lost like 30% of the genes and became more simplified creatures, then somehow copying these remaining genes further and futher evolving them and becoming very succesfull in their own niches

first there was ancestor of fish, somekind of weird worm which wasnt yet segmented

then it gave birth to octopus

after octopus (and snails) had separated from the original worm, the worm changed into a segmented type

then the segmented worm evolved into fish (pieces of fish vertebrae are the segments)

on the other hand the worm also evolved into insect ancestors some 700 million years ago, we would be talking about ocean creatures as insects themselves start on land and were never in the sea

centipedes are very segmented, each segment is kinda like a piece of human vertebrae. on the other hand insects have less segments, only the head, middle body and abdomen so you can think of them being two pieces of vertebrae

however in insects the segmentation continues in their legs as well

only centipedes, insects and spiders have so called arthropod legs, I am not entirely sure what part of human is corresponding to their legs, maybe lungs because in unsegmented worms the hairs that come out of them are the worms lungs and the hairs look like insects legs..

in terms of genes, insects are a succesfull case of "lost of genes"
they originally had all the genes a fish would have but they lost majority of it and became twisted into the form they are now, they dont contain an inner vertebrae but instead the vertebrae manifests itself as insect segmentation of the whole body

what continues to be same for fish and insect is a hollow notochord inside the creature (in fish its inside vertebrae, in insects its just stays there inside their body running from brain to anus, if a notochord is cut in half insect is paralyzed)

>> No.15975339 [View]
File: 198 KB, 1411x833, spiders.jpg [View same] [iqdb] [saucenao] [google]

A gene comparison

Altough spiders are arthropods like insects and there for not a unique group of their own, they are the most ancients.

You see, spiders never evolved chewing mouthparts while other arthropods have it. Actually most of the more complex forms of life have chewing mouthparts, spiders dont as they did not evolve.

This is due to being so ancient anad unchange for hundreds of millions of years. Ancestors of spiders went extinct, they have certainly been the eyrypterids so called sea scorpions. They came to land 333 million years ago and gave rise to land scorpions and one group of land scorpions eventually evolved into spiders and lost their tails and the venom gland on tails were genetically shifted to appear onto their jaws instead. Spider venoms and scoprion venoms are essentially same stuff.

So now we see here a genetic comparison between multiple spiders and some human relatives thrown in for a good measure. Comb jelly is there to provide an outgroup.

Humans and spiders do share one thing: both are bilaterian animals and had the same ancestor who lived maybe 800 million years ago on the bottom of the sea. While a comb jelly and human shared ancestor a longer time ago, probably 1.1 billion years. Comb jelly is the first animal that appeared on Earth. Animal is not a plant, yet it is alive. Another mandatory requirement of an animal is to be multicellular form of life, single celled life is never an animal despite how much it would behave like an animal. Animals and fungus are more similar to each other than neither are to plants.

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