Arthropods are categorized as invertebrates with jointed appendages and an exoskeleton. These go crunch-crunch when you step on them and they have limbs. Because of the exoskeleton, these organisms need to molt, or shed their old exoskeleton. This leaves the organismA living individual made up of cells. vulnerable for a short periods of time, but it is a process necessary for growthAn increase in size and number of cells.. Ever had soft-shelled crabs? They are recently-molted crabs.
Arthropods, which includes the group of insects, are incredibly diverse in body structure. However, all the variants have a common body plan of three parts: Head, thorax, and abdomen. They are kind of like a modular home, you need a kitchen, a bedroom, and a bathroom, but you get to choose the configuration of each. Your thorax is your chest. I’ll leave you to figure out the other two for yourself. Some arthropods have a combined headRounded proximal end that fits into the acetabulum of the hip bone. and thorax called a cephalothorax.
The appendages are diverse as well. On this grasshopper we’ve got wings, walking legs, and jumping legs. And on this lobster, we’ve got claws for grasping, legs for walking and jumping, and swimming appendages on the tail.
Arthropods do not have a dedicated blood supply contained in vessels like mollusks and annelids. Each body cell bathes in an interstitial fluidThe fluid surrounding cells within tissues. (that word just means “the fluid between the cells”) which exchanges with the outside environment. Their respiratory systemThe organ system responsible for gas exchange (oxygen and carbon dioxide). is just a system of tubes, or tracheae (like our windpipe) throughout their body. Their movements create pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. gradients to move the air closer to the cellsThe basic structural and functional units of life. for exchange.
Arthropods have a differentiated digestive system. We can see that they have a crop for food storage (much like a stomach), and some gastric pouches for overflow. Arthropods, especially insects have an incredible diversity of feeding appendages. In factA statement based on direct observation that is repeatedly confirmed., the lack of overlap in feeding strategies and food sources is what contributes to the incredible fitness of arthropods. This mosquito has a straw to suck your blood. These horse chestnut leaves have been mined by hungry moths.
We all learned the caterpillar turns into a cocoon and then a butterfly emerges, which is an accurate representation of the larva, pupa, adult life cycle of insects, one group of arthropods. The life cycle ensures that adults and larvae have different feeding strategies and therefore do not compete for food. This, again, increases fitness, success, and widespread distribution. Camouflage is another fitness contributor for insects. This hummingbird moth is showing something called mimicry. By mimicking a common bird in his environment, he can escape his own predators. Stick bugs mimic well…sticks. Some little insects even mimic a smear of bird poop. Good strategy: who wants to eat bird poop?
List of terms
- organism
- growth
- head
- interstitial fluid
- respiratory system
- pressure
- cells
- fact