Crayfish are invertebrates which means they don't have a backbone. They are also arthropods, which means that they have a protective exoskeleton on the outside of their body. Other arthropods include insects, spiders, and centipedes. Crayfish continually shed their exoskeleton and regrow a new one. During this transition is when they are most vulnerable to predators because they aren't protected by their outer shell.
Crayfish are found all over the world in many different freshwater environments, such as rivers, creeks, springs, and swamps. But this doesn't necessarily mean that you will be able to find them. They are somewhat cryptic because they dig out homes for themselves under rocks and blend in well with their environment. Crayfish will ardently defend this dwelling against intruders using their strong front claws
The surface tension of a liquid results from an imbalance of intermolecular attractive forces, the cohesive forces between molecules: A molecule in the bulk liquid experiences cohesive forces with other molecules in all directions. A molecule at the surface of a liquid experiences only net inward cohesive forces.
There have be found some fossils of ancient remains over the years. What the fossils from Atapuerca revealed about the hominins living in Europe at this time is below:
- The Skull is known to show Interbreeding that took place with neandertals and their relatively healthy population.
- The Fragment shows that there was a possibility of cannibalism in that area.
It shows that possible cannibalism took place as there were Cutmarks on various hominin bones found at Atapuerca mirror.
The relatively healthy population was found out through the study of the dentition of the Atapuerca hominins by anthropologists. It gave them a view into their diet and overall health.
The interbreeding with the Neandertals was shown through the Nuclear DNA that was gotten from bones and teeth of bones found at Sima de los Huesos
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