I am not sure, but from what I can conclude from diagrams and from a recent dissection no, the crayfish does not have a liver. Although you should consider asking your Biology teacher just to be sure.
why do
the crayfish fight
You don't mention the species of either, so it is impossible to tell if one species will try to eat the other or not.
Recognising your own species is important when you're looking for a mate because interspecies mating is generally unviable or, at best, produces sterile offspring. this would mean the species would go extinct. Also if animals of the same species did not recognise other animals of the the same species they might fight which would not be good and also eat each other which could cause fatal diseases.
It depends on how much your two Pokemon like each other. The more they like each other, the faster they'll produce eggs. Pokemon are more likely to like each other more when they are the same species and have different original trainers. So the best is same species, different trainer IDs. Next best is same species, same trainer and different species, different trainer IDs. And least is different species, same trainer ID.
competitors
Two different species that belong in the same class will also share the same phylum and kingdom in their classification. This means they will be more closely related to each other than species in different classes.
Yes! It is the same species. This species is also known as the Niger Giraffe. It is the only species that live in the northern-western parts of Africa.
well, cannibalism is when organisms of the same species or race starts to destroy, or eat each other.
Crab, shrimp, and lobsters are in the same phylum as crayfish. They are all in the arthropoda phylum. Arthopods have an exoskeleton, a segmented body, and jointed appendages.
Because each species has to have its own role in the environment
No they do not. think of all different types of dogs, a great dane could mate with a little beagle, because they are all the same species. they have gamete compatabilty. the look different from each other but they are the same species. Looks dont matter
Lobsters are saltwater and crayfish (crawdads) are freshwater.
Mutualism. It is when both species benefit from each other. you know how people in movies are like "I hate you" then the other person says "the feeling is mutual" Mutual means it is the same way. So that is how I like to remember it. Mutual means BOTH have the same feeling. So mutualism means they BOTH benefit from each other