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
Atoms. Every element is made of a specific type of atoms.
Likely he will be diagnosed by the hospital as seen as a risk constantly for violence with others. This isn't uncommon in people with drug abuse, or someone who has come from an abusive household. It's quite likely he has faced abuse and may suffer from an emotional mental health disorder. (IE manic depressive disorder, anger issues, or purely a sociopath)
Gause's Competitive Exclusion Principle
The 'competitive exclusion principle' (CEP) states that two species with identical niches cannot coexist indefinitely. ... Gause helped propel ecology by his approach of experimentally testing mathematical models, and his unifying the concept of the niche with resource competition.