Arthropods have what type of skeleton

It can be thick and hard for protection, thin and soft for flexibility, and even stretchy for movement. It can be heavy or it can be light to allow for flight. It can be permeable, letting water or gases in and out, or it can be solid and waterproof. It can also be different colors.

Because the cuticle is so versatile, this main feature has allowed insects to become one of the most successful groups of animals on Earth. A spider's body has two segments: a cephalothorax and an abdomen. Insects have a brain, a nervous system, a heart, a gut for digestion, and tubes called tracheae to breathe oxygen. Spiders have eight legs and, in general, have "simple" eyes instead of the "compound" eyes that give many insects much better vision. Most insects, such as beetles, wasps, and flies, go through complete metamorphosis.

They begin life as an egg that hatches to a larva. The larva eats, grows, and sheds, then turns into a pupa in which chemical changes take place. The final stage is changing into the adult insect, which is able to reproduce. In more primitive insects, such as grasshoppers and stick insects, another type of development is used.

This process is called incomplete metamorphosis where the insect hatches from the egg as a miniature version of the adult. The insect continues to grow, and every time it molts it gets larger until it reaches adulthood. Insects are divided into two main groups: the wingless insects like bristletails and silverfish; and the winged insects like dragonflies, cockroaches, grasshoppers, stick insects, beetles, flies, butterflies, ants, and bees.

While most crustaceans are mobile, one exception is the barnacle. Barnacles are free swimming as larvae, but when they metamorphose, the head reduces and is cemented to the substrate with a strong chemical glue. The barnacle secretes a hard protective shell around itself and filter feeds from inside this shell, using elongated appendages to collect food particles.

Due to their lack of mobility, barnacles are one of the few arthropods that are hermaphroditic. The crustacean body is clearly divided into a head, an abdomen, and a thorax.

While the insects have a flexible joint between the head and thorax, crustaceans tend to have the two sections fused together. Crustaceans have two antennae on the head, followed by mandibles , maxillae , and maxillipeds , all structures for handling food Fig.

The thorax contains the walking and swimming legs. The front pairs of appendages are often modified into claw-bearing appendages.

The abdominal section contains appendages called swimmerets Fig. These appendages produce water currents that pass over the gills for respiration. Female crustaceans typically use swimmerets to hold onto eggs for brooding , or keeping the eggs with them until they are ready to hatch. The abdomen also contains the tail appendages. Lobsters and crayfish have external structures that make it possible to identify their sex.

Males and females can be identified by their swimmerets, the appendages on the abdomen. The female swimmerets have hairs, making them look like feathers; the male swimmerets are relatively hairless Fig. In the male, the sperm openings are at the base of the last walking legs.

During mating the male transfers the sperm by using the first pair of its abdominal swimmerets behind the walking legs. In males, the swimmerets are large and point toward the front of the body. When brought together in the midline of the body, these two appendages form a tube through which sperm pass to the female. The female keeps the sperm in a saclike receptacle whose opening is between the third pair of walking legs.

The openings of the female reproductive tract are at the base of the second pair of walking legs. Some days or weeks after receiving the sperm, the female releases several hundred fertilized eggs.

These eggs are attached to her swimmerets by a glue-like secretion. The eggs hang like grapes on a stem for weeks to months until hatching. In crabs the abdomen is much smaller than in lobsters and crayfish, and the reproductive structures are not as easy to see.

In males the abdomen is narrow and fits into a groove on the under side of the thorax. In females the abdomen is flat and broad for sheltering eggs, covering most of the underside of the thorax Fig. Investigate the behavior of various aquatic invertebrate taxa through careful experimentation and observation.

This document may be freely reproduced and distributed for non-profit educational purposes. Skip to main content. Search form Search. Join The Community Request new password. Main menu About this Site Table of Contents. Home Biological Invertebrates Phylum Arthropoda. Phylum Arthropoda. MS-LS Use argument based on empirical evidence and scientific reasoning to support an explanation for how characteristic animal behaviors and specialized plant structures affect the probability of successful reproduction of animals and plants respectively.

MS-LS Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms. MS-LS Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. MS-LS Develop and use a model to describe why asexual reproduction results in offspring with identical genetic information and sexual reproduction results in offspring with genetic variation.

HS-LS Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

HS-LS Communicate scientific information that common ancestry and biological evolution are supported by multiple lines of empirical evidence. The content and activities in this topic will work towards building an understanding of the phylum Arthropoda.

Introduction to Phylum Arthropoda The phylum Arthropoda contains a wide diversity of animals with hard exoskeletons and jointed appendages.

Subphylum Chelicerata Chelicerata from the Greek word chela meaning claw is the subphylum of arthropods that includes spiders, mites, scorpions, and horseshoe crabs.

They carry their eyes atop a little tower on their back weird! Crustaceans are mostly marine, and dominate the ocean to the same degree that insects dominate the land and air.

Despite their aquatic diversity, there are very few terrestrial crustaceans, just as there are very few truly aquatic insects. Crustaceans have biramous appendages. Each leg has an additional process, like a little miniature leg branching off from the main leg. Many groups of crustaceans have lost this extra appendage during subsequent evolution.

The Order Decapoda have five pair of walking legs, and include the familiar crabs, lobsters, and crayfish. The first pair of appendages are usually modified as antennae. Crustaceans have two pair of antennae. Another set of anterior appendages are modified as mandibles, which function in grasping, biting, and chewing food. Male crayfish also use one pair of legs as a copulatory organ.

All crustaceans share a common type of larva called a nauplius larva. They are one of the few successful terrestrial crustaceans. They feed on decaying vegetation in the leaf litter.

Uniramians have a single pair of antennae, and uniramous appendages. They probably evolved from oligochaete worms. Class Chilopoda - 2, sp. Centipedes dwell in damp places under old logs and stones. They are carnivorous, eating mostly insects. They are highly segmented, and have one pair of legs per segment. The first trunk segment bears poison fangs. Centipedes are very dangerous, and their bite is extremely painful. Class Diplopoda - 10, sp. Millipedes share the same habitat as centipedes, but they are mostly herbivorous, feeding on decaying vegetation in the leaf litter.

Animals that feed on detritus are called detritivores. Each segment of the millipede is actually two segments fused together hence the double set of legs. They can secrete a defensive fluid that smells bad, and a few species actually secrete tiny amounts of cyanide gas to protect themselves! Class Insecta - , sp. If we knew all the different insects on Earth, there could be as many as 30 million species. Insects evolved about mya, with cockroaches and dragonflies among the first to appear.

Insects have a head, thorax, and abdomen, with three pair of legs 6 legs on the thorax. Crustaceans have legs on the abdomen as well as on the thorax. Most insects have one or two pairs of wings.

They are the only invertebrates that fly. Most have compound eyes , and can communicate by sound and scent, using powerful chemical hormones called pheromones. Insects have extremely elaborate mouthparts, consisting of pairs of appendages fused into a lower lip labium , and an upper lip labrum , with other appendages called maxillae aiding in chewing.

These mouthparts are highly modified in various groups for chewing, sucking, and piercing. Insects undergo metamorphosis as they develop, changing from one form to another as they mature. The juvenile stages look like tiny versions of the adults. Their larvae are often radically different from the mature adult like the butterfly and the caterpillar. They not only look different, they live in different places and eat different food. Observe the preserved arthropods on display.

How do the various groups use their legs to walk, swim, feed or mate? Watch the way the millipede moves. Look at the legs. See how the waves of muscle contraction pass down through the segments? The polychaete worm Nereis moves in exactly the same way. Handle the millipedes very gently. They are someone's pets. They also make great pets for dorm rooms - they need little care, don't take up much room, and don't make noise or messes, unlike your roommate.

Disturb the centipedes to get them moving around. Can you see the poison fangs? Notice how flat the body is, and contrast the number of legs with those of the millipede. Why does each container hold only a single centipede? Don't open the jars unless you have a thing for extreme pain.

Play around with the roly-polys. Oh, go ahead, it's cool. They won't bite. Watch the way they roll up into a ball when disturbed. Not all isopods can do this, but rolling up into an armored ball is a great defensive tactic. Compare our teeny tiny terrestrial version with the enormous preserved marine isopods. Look at the live brine shrimp, hermit crabs and fiddler crabs. Treat them gently more pets.