Echinoderms Flashcards
What is an endoskeleton?
What other animals can you think of that have an endoskeleton?
An endoskeleton is a skeleton inside the organism that still provides the same
structure and support as an exoskeleton (skeleton outside of the organism). All
mammals have endoskeletons (humans, dogs, cats, tigers, etc.), as well as animals
like birds and fish. Animals with exoskeletons include arthropods and some mollusks.
How are Echinoderm larvae different from adult echinoderms in terms of symmetry?
Echinoderm larvae are bilaterally symmetrical, whereas the adult echinoderms are
radially symmetrical.
Give the functions of each of the following structures:
a) Ampulla
b) Tube Feet
c) Madreporite
a) Ampulla - pumps and retracts water
b) Tube Feet - many functions: excretion, gas exchange, motility
c) Madreporite - opening for the water vascular system
Describe in detail how the Sea Star feeds on bivalves.
The sea star has two stomachs. One stomach can be extended through their mouth.
The sea star will engulf and digest its food outside its body with this stomach, and
then bring it back and further digest it with its internal stomach. The cardiac stomach
digests food outside the body and then brings in food (that would be too large
otherwise) into the body and transfers to the pyloric stomach.
What is unique about the Sea Star stomach?
There are two of them, and one can be extended out of their bodies, allowing them to
consume foods that are bigger than them (or things that wouldn’t necessarily fit in
their mouth).
Describe the organization of the Sea Star nervous system.
Include the terms central ring and radial nerves.
Their central ring is the nerve ring around the mouth, and they have radial nerves
spreading across each of their arms.
Describe in detail how a Sea Star is able to move using its water vascular system.
Sea stars possess a water vascular system. Water enters this system through the
madreporite, or sieve-plate, and fills the ring canal and corresponding radial canals in
each arm. Attached to the radial canals are hundred/thousands of tube feet. These
structures consist of two main components, the foot and the ampulla. Think of each
tube foot as like an eyedropper with the ampulla being the bulb that you squeeze in
and out (but water doesn’t shoot out). When the ampulla contracts (squeezes) water
is forced into the foot causing it to extend. This allows for the seastar to push off of
surfaces. When the ampulla retracts water is brought back into the bulb and it creates
a suction effect with the tube foot. This action allows for grip and in some cases it
allows the sea star to hold onto its prey and pry it open.
advantages and disadvantages of the exoskeleton
Having a hard covering on the outside in the form of an exoskeleton is a great defense against predators.
Exoskeletons do not grow with the animal, so arthropods have to molt, shedding their old shell and growing a new one. This is a disadvantage to the whole system since arthropods have very little protection after they shed their old shell until the new one hardens completely.
complete vs incomplete metamorphosis
incomplete metamorphosis is when the baby insect hatches from the egg and looks similar to an adult except they are smaller and do not have wings or reproductive organs.
complete metamorphosis is when a baby insect hatches from an egg and looks completely different from the adult
body regions of arthropods
head, thorax, and abdomen.
The head is specialized for sensory antennae and compound eyes. the head of organisms helps them respond to the environment.
of the thorax is where a segment of legs and possibly wings is fond to help with movement.
the abdomen is a segmented region in which most of the major parts of a thing are held in such as digestive, respiratory, excretory, and reproductive systems. these systems take place inside the abdomen.
echinoderm vs arthropod comparisons
they both sexually reproduce.
they both have an open circulatory system.
they both have a complete digestive system
the differnts is ther covering, Arthropods have a tough, non-living outer shell called exoskeleton, which protect their soft bodies while echinoderms have living endoskeletons, which develop within the deeper skin or body tissues and act as their protective covering
