Arthropods are animals with jointed appendages. The term arthropod literally means "joint foot." Distantly related to annelids, arthropods are the first group of animals to have jointed appendages. There are over 5 million species of arthropods composed of insects, spiders, crustaceans, and scorpions. A main feature of arthropods is their segmented body and coleom.
Skeletal- Arthropods have a rigid exoskeleton composed of chitin. The exoskeleton acts as a shell and is the main defense of the organism. Insects' exoskeletons are more flexible and can flex better to their movements, while crustaceans and scorpions have a more rigid, inflexible exoskeleton that doesn't respond as well to their movements. Arthropods have the ability to molt, or shed their old exoskeleton and regrow a larger, tougher exoskeleton. The new skeleton grows underneath the old one.
Muscular- Arthropods have distinct regions in their body. The regions are the head, thorax, and abdomen. Sometimes the head and thorax are fused together, like in crabs, to form a cephalothorax. Many arthropods have muscular wings that give them the ability to fly. Arthropods only have striated muscles attached to the exoskeleton and contain no smooth muscles. The muscles contract and pull on the exoskeleton for movement.
Muscular- Arthropods have distinct regions in their body. The regions are the head, thorax, and abdomen. Sometimes the head and thorax are fused together, like in crabs, to form a cephalothorax. Many arthropods have muscular wings that give them the ability to fly. Arthropods only have striated muscles attached to the exoskeleton and contain no smooth muscles. The muscles contract and pull on the exoskeleton for movement.
Circulatory- Arthropods have an open circulatory system, but have a heart. They have a dorsal vessel that runs through the abdomen and thorax. This dorsal vessel collects hemolymph, the blood of the arthropods, and pushes it towards the head. The hemolymph is then squirted on to the brain and head and flows freely back through to coleom. Inside the dorsal vessel, there are hearts that prevent back flow and push the blood towards the head.
Respiratory- The way that Arthropods respirate is through small tubes called tracheae. These tubes connect throughout the body and deliver oxygen to all of the cells. On the outside of the body are tiny holes called spiracles where the gas exchange occurs. Most arthropods don't have lungs, but some aquatic species have gills that take in air then deliver to the tracheae.
Respiratory- The way that Arthropods respirate is through small tubes called tracheae. These tubes connect throughout the body and deliver oxygen to all of the cells. On the outside of the body are tiny holes called spiracles where the gas exchange occurs. Most arthropods don't have lungs, but some aquatic species have gills that take in air then deliver to the tracheae.
Excretory- In arthropods, the excretory system is complete. They have an anus that excretes all solid waste. Some arthropods have specialized tubes called Malpighian Tubes, that extract waste from the digestive system and connect into the rectum to dump the waste and excrete it. In arthropods, their adaptation for water conservation has led to their urine being saltier than their blood to reduce as much salinity. In crustaceans, ammonia urine is excreted through their gills or permeable membranes. Land arthropods excrete uric acid as their feces.
Digestive- Arthropods range in all types of diets from carnivores, herbivores, parasites, and filter feeders. Most arthropods have a digestive system made of a foregut, midgut, and hindgut. The foregut contains the mouth, esophagus, and the crop that holds food before digestion. The midgut is the stomach and the hindgut is the intestine, anus and rectum. After the intestine, the Malpighian tubes dump into the rectum. The foregut and hindgut are lined with chitin and the midgut is the main absorption system. Some arthropods also have digestive glands that are in the foregut that secrete enzymes to break down the food and go leave the body, in the cases of spiders and other poison using animals.
Digestive- Arthropods range in all types of diets from carnivores, herbivores, parasites, and filter feeders. Most arthropods have a digestive system made of a foregut, midgut, and hindgut. The foregut contains the mouth, esophagus, and the crop that holds food before digestion. The midgut is the stomach and the hindgut is the intestine, anus and rectum. After the intestine, the Malpighian tubes dump into the rectum. The foregut and hindgut are lined with chitin and the midgut is the main absorption system. Some arthropods also have digestive glands that are in the foregut that secrete enzymes to break down the food and go leave the body, in the cases of spiders and other poison using animals.
Nervous-In arthropods, there is a central brain that connects to a longitudal, ventral nerve cord. Lateral nerves extend from the main ventral cord and there are clusters of nerves, called ganglia, that are spaced throughout the ventral cord. For one cell, there are many different nerves that cause different contractions depending on which nerve is fired, versus humans having one nerve for one cell. Nerve endings are located on the outside of the body in hairs, pits, cones, or slits in mouths, gills, or antennas. Many carnivorous arthropods use nerve endings in their feet to sense vibrations from prey. Lots of arthropods have eyes that sense light, but can't see very well. Lots of arthropods have multiple eyes, like spiders, or compound eyes, like flies and insects.