Yes

class cyclostomata are without jaws

there eg are :

petromyzon

myxine

The lower an organism is in the food chain the greater its population.

Yes, lobsters are one of the creatures that are capable of regenerating limbs. Also, lobsters have been known to cut off their own limbs as a survival mechanism too.

Chitin has two notably good qualities as an exoskeleton. Since it is a type of protein, it is relatively easy for arthropods to make. And it is quite tough. Its properties are similar to the protein keratin, which is used by mammals for making hair, nails, and horns.

Yes. A nematode is covered by a tough cuticle that is periodically shed through ecdysis.

1. Trilobites

2. Chelicerates

3. Myriapods

4. Hexapods

5. Crustaceans

they all have exo skeleton

No. A unicellular organism is an organism made up of ONE CELL, so they're all microscopic. Microscopic means that you can't see it it without a microscope. And you can see a sea urchin, so it is not microscopic, so it's not unicellular.

An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and jointed appendages. Arthropods are members of the phylumArthropoda(from Greek ἄρθρον arthron, "joint", and ποδός podos"foot", which together mean "jointed feet"), and include the insects, arachnids, crustaceans, and others. Arthropods are characterized by their jointed limbs and cuticles, which are mainly made of α-chitin; the cuticles of crustaceans are also biomineralized with calcium carbonate. The rigid cuticle inhibits growth, so arthropods replace it periodically by molting. The arthropodbody plan consists of repeated segments, each with a pair of appendages. It is so versatile that they have been compared to Swiss Army knives, and it has enabled them to become the most species-rich members of all ecological guilds in most environments. They have over a million described species, making up more than 80% of all described living animal species, and are one of only two animal groups that are very successful in dry environments - the other being the amniotes. They range in size from microscopic planktonup to forms a few meters long.

Arthropods are characterized by segmented bodies, an exoskeleton made from chitin, and joint appendages. They have an internal body cavity (hemocoel) and an open circulatory system which employs hemolymph, a fluid that does not distinguish between interstitial fluid like lymph and oxygen carrying fluid like blood as in most vertebrates. They use a copper-based oxygen carrier molecule instead of the iron-based hemoglobin, which floats unbound around in the hemolymph and is not bound to blood cell proteins. They do not have a dedicated and separate branch of their circulatory system just to oxygenate; internal organs (and cells) are simply bathed in this fluid. Their nervous system is 'ladder-like' on their ventral surface, and their brains formed around the esophagus from fused segment nerve ganglia.

Some of these adaptations of butterflies

are that they can fly

and also they pollinate flowers.

The true count of living arthropods at any given moment on Earth is unknown but some estimates place it at around ten quintillion (10,000,000,000,000,000,000) which is over a billion for every human.

The head, thorax and abdomen are one so a three peice body, three pirs of legs and I can not think of the third...

yes, because it has its skeleton on the outside (its shell)

They have muscles like us, except theirs are smaller and are connected to the inside of their exoskeletons, instead of wrapping around the endoskeleton like we have.

Domain: Eukarya
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Superorder: Heterobranchia
Order: Pulmonata

The name for phylum Arthropoda is derived from "jointed legs" or jointed feet, and arthropods live up to that name. Because of the rigidity of the exoskeleton, joints are apparent in any of their mobile appendages; not just legs but some specialized appendages like swimmerets for aquatic arthropods, antennae, wings, all evidence some kind of jointing. Legs themselves may have specialized adaptations; some insects hear or taste with special organs on the legs or feet. Some crustaceans have legs bearing claws (chela) called chelipeds.

An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda, which together mean "jointed leg", and include the insects,arachnids, and crustaceans. (Ant, Spider and Crab)

No, krill are a type of fish that whales feed on. They are very small.