Why do different animal species have similar anatomical structures?
In: Biology
Same technology stack. We all share mostly the same source code in our DNA. Cells work mostly the same. Skeletal structure has been optimized through trial and error over hundreds of millions of years and hundreds of billions of tweaks and changes.
Everything comes from sharing 80+% or more of the source code and technology.
Similar anatomical structures may be due to homology, which means the structure was inherited from a common ancestor that already had that structure. Humans and sharks both have hearts and two eyes because their last common ancestor did.
Similar anatomical structures may also be due to homoplasy, which means the structures independently evolved in each lineage. Hippos and alligators both have eyes and nostrils on the top of their head, independent adaptations to living mostly submerged in water.
They may have came from the same ancestors before they evolved. Like apes and humans, it is believed that somewhere down the line the apes and humans shared a common ancestor before splitting into different evolutionary path, causing somehow similar anatomical structure.
well animals had a very long time to be different shapes and sizes over a very long time. usually if a shape is bad they get eaten so the animals who arent that shape survive to be other shapes. some of these shapes simply work very well so at some point more than one animal was that shape and it worked really well so they kept it and didnt change shapes.
I would suggest reading Richard Dawkins book _Climbing Mount Improbable_. It does a great job of giving you some examples and explanations to help you understand better evolutionary biology.
Convergent evolution. The animals with the best designed bodies are most likely to survive long enough to breed and pass on their genetics.
An example is ichthyosaurs, sharks and dolphins. All are built very similarly but they’re not related. They’re a reptile, fish and mammal respectively. But that design is great for streamlined swimming and attacking the prey they do. So the animals with those features naturally survived more than those without if their niche was eating the same fish sharks and dolphins do.
One thing to add to what others have said is the trend of cephalization in species. It explains why so many species have their sense organs and mouths at the leading end (head) of their body, which may explain not *why* they have similar organs but why they look similar
https://en.m.wikipedia.org/wiki/Cephalization
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