Arthropods

Arthropods

• The phylum Arthropoda makes up over 75% of the world’s species.

• Arthropods include insects, centipedes, millipedes, spiders, ticks, scorpions, mites, lobsters, shrimps, crabs, and crayfishes.

Arthropods• A typical arthropod is an invertebrate

animals with bilateral symmetry, an exoskeleton, and joint structures called appendages.

• An appendage is any structure, such as a leg or antenna, that grows out of the body of an animal.

• In arthropods, appendages are adapted for a variety of purposes, including sensing, walking, feeding and mating.

• Joint appendages are useful because they allow for more powerful movements during locomotion, and they enable the appendage to be used in many different ways.

Body Structure

• The body of arthropods is made up of three segments:

Head

Thorax

Abdomen

Exoskeleton• The success of arthropods as a group can be attributed in part to the

presence of an exoskeleton.

• The exoskeleton is a hard, thick, outer covering made of protein and chitin.

• In some species, the exoskeleton is a continuous covering over most of the body. Example: Beetle

• In other species, the exoskeleton is made of separate plates held together by hinges. Example: Spider

• What are some advantages and disadvantages to having and exoskeleton?

Desert Tarantula Japanese Beetle

Molting• While the exoskeleton provides protection, one disadvantage is

that the exoskeleton cannot grow with the animal.

• Therefore, arthropods must go through a process called molting, where they shed their exoskeleton and grow a new one.

• What are advantages and disadvantages to molting? Cicada molting

Arthropod Behaviors

Black Widow Spider

• Female is black with a red, hourglass-shaped spot on her underside.

• After mating, female eats the male.

Arthropod Behaviors

Praying Mantis

• Female praying mantises eat males. Therefore, males have to “sneak up” on females in order to mate.

• Males also perform a mating dance so females know not to eat them.

Social Insects

• Bees, ants, wasps and termites are known as social insects because they form elaborate and complex social systems which rely on communication and social interaction.

Bees Ants Wasps Termites

Bees• Bees demonstrate a

hierarchical system (Caste System)

Queen Bee – The boss. She lays all of the eggs.

Worker Bees – Only females. Perform daily functions of hive (honey, wax, building)

Drone Bees – Only males. Tend to Queen and fertilize eggs.

Queen Bee

Bees• Bees communicate through dance.

• Upon returning from a rich nectar source, a worker bee will perform one of two dances, a “round dance” or a “waggle dance,” in order to tell the other bees where to find more nectar.

• A “round dance” indicates that nectar is nearby, but gives no direction.

• A “waggle dance” indicates that nectar is far away and provides a direction for the bees to follow.

“Round dance”

“Waggle dance”