Legs and exoskeletons were extremely useful, as these enabled the creatures to resist gravity, which is not a concern in the bouyancy of water.

That it's hungry.. >.<

three paits of jointed legs.

Edit: Be Real Man. The real answer is that the water pushes heavy stuff up to make them lighter in water then in land.

edit: really you both are rong the real answer is:Afaik this depends on the animal in question. Some insects, for example, do not grow in size at all when adults and thus avoid this problem. Animals that do shed their exoskeleton can move, the underlying soft exoskeletong along with the internal pressure of the animal are enough to facilitate this. But at least many crayfish (and likewise many otehr arthropods that shed their exoskeleton) hide until their exoskeleton has hardened again - that is, they can move, but will not unless they really have to. They just hide in some nook and wait.

And what comes to other disadvantages of chitious exoskeleton: it allows muscles to attach only inside of the exoskeleton, quite unlike human muscles for example work. This provides poorer strength production, which is why arthropods cannot really grow much larger than what we see around us. For similar reasons, virtually all the largest arthropods live in water, because there you need less strength to move heavy weights.

Even though we know that ants are mighty strong compared to their size, human-sized ants would collapse even udner their own weight and they could not carry a hundred or so times their weight like small ants do!

an arthropod sheds it old exoskeleton when it has grown to a point where it needs a larger exoskeleton. This process is called ecdysis.

They can change colors, yes. They can change from looking like a golden lady bug to looking like a lady bug by controlling the amount of moisture present under their shell.

Arthropods that damage plant parts to the point of interfering with or terminating biological, botanical, and zoological life cycles and natural histories are bugs that are bad for the garden. A garden-friendly behavioral standard can be set by adult birds and lepidopterans, who rarely feed upon nectar and pollen to the point of exhausting the plant's ability to keep producing such food sources which simultaneously are respectively attractants for and participants in reproduction-oriented activities. A garden-unfriendly standard is found among such defilers as aphids, insects that deplete a plant's life-giving nutrients channeled by capillary action upward from roots and photosynthetic products transported downward from leaves.

Ovoviviparous refers to an animal that retains the egg inside of them until it hatches and gives birth to larval young. Two insects that do this are Sarcophagid flies and tachinids.

Trilobites, and eurypterids (giant marine scorpions).

Ammonites are not arthropods but molluscs.

On the biological ruler, arthropods tend towards the small end of the spectrum, owing to physical limits imposed by their methods for respiration, gas exchange and circulatory system; a high surface area to volume ratio serves them quite well on these counts.

The smallest arthropods known are a crustacean parasite, Stygotantulus stocki, around a hundred micrometers long (about 4 thousandths of an inch).

bane of arthropods does extra damage to Spiders, cave spiders, and silverfish

This depends on the type of arthropod, but most do not. Most arthropods never migrate further than 200 feet from their place of birth.

it grow a new exoskeleton

Bilateral, meaning left and right are equal.

The most obvious answer is the Chilopoda, the centipedes. The Diplopoda or millipedes seem to have two pairs of legs per segment, though actually that is because their real segments are joined in twos so that what looks like one segment really is a double segment and therefore bears four legs.

Yes, arthropods have to moult in order to increase in size, because their exoskeleton is rigid and inhibits growth. The process is called ecdysis and is not limited only to arthropods; it is a characteristic of their clade, ecdysozoa, which includes nematodes and other phyla. Arthropods are more vulnerable when moulting because their new exoskeleton is soft and therefore more vulnerable to predators. The new exoskeleton takes a while to harden; many will hide and wait during this time. Arthropods will usually moult multiple times during their lifespan; the process is also associated with lost limb regrowth.

Three body parts{segments } of Arthropods are head , thorax and abdomen .Technically these are called tagma and they are made up of segments .

Arthropod exoskeletons are naturally hard because of the composition of the protein used (a chitin composite); crustaceans further harden it using a process called biomineralization.

Chitin chemically is a long-chain polymer, a nitrogenated polysaccharide comparable to cellulose, which allows for hydrogen bonding between polymers for additional strength. By embedding in sclerotin and mineralizing it, arthropods achieve an advantage of gaining a greater toughness and less brittleness than minerals alone but being stiffer and harder than pure chitin.

who care

They use the smaller of the two claws to pick it up.

no they don't

The exoskeleton of arthropoda is made of a tough protein called chitin, a long-chain polymer comparable to cellulose. It fills the same role as the protein keratin in other animals (found in hair, nails, hooves, claws, beaks, etc). Some arthropods, like crustaceans, further harden their exoskeleton by biomineralization with calcium carbonate. Because it is inflexible, the organism has to periodically shed their entire exoskeleton in order to grow.