An organism has spherical symmetry if it can be cut into two identical halves by any cut that runs through the organism's center.
An organism has radial symmetry if it can be cut into two identical halves by any longitudinal cut through its center.
An organism has bilateral symmetry if it can only be cut into two identical halves by a single longitudinal cut along its center which divides it into right and left halves.
The sessile, tubular form of a cnidarian with a mouth and tentacles at one end and a basal disk at the other.
Animal tissue consisting of one or more layers of cells that have only one free surface, because the other surface adheres to a membrane or other substance.
A system designed to transport food and other necessary substances throughout a creature's body.
A sheath of tissue that encloses the vital organs of a mollusk, secretes its shell, and performs respiration.
A tough, multilayered structure secreted by the mantle, generally used for protection, but sometimes for body support.
A muscular organ that is used for locomotion and takes a variety of forms depending on the animal.
Determine the symmetry of the following organisms:
A. Eagle B. Jellyfish C. Centipede D. Mushroom
A. Bilateral. B. Radial. C. Bilateral. D. Radial.
If a sponge is soft, does it contain spicules or spongin? What purpose do these substances serve in a sponge?
It contains spongin. These substances support the sponge.
What roles do amoebocytes play in the anatomy of a sponge?
Amoebocytes help digest and transport nutrients, they help carry waste to be excreted , they bring necessary gases such as oxygen to the cells, and they form the spicules or spongin.
What is the difference between the nematocysts of a hydra and those of a sea anemone?
Hydra nematocysts are triggered with pressure, while the sea anemone's are triggered chemically.
Why do cnidarians not need respiratory or excretory systems?
Cnidarians do not need these systems because their body walls are so thin that gases diffuse right through them.
Some biology books say that jellyfish live "dual lives." Why?
Jellyfish spend part of their lives as polyps and the other part as medusas.
What benefits do earthworms give the plants in the soil they inhabit?
Earthworms bring minerals up from the lower parts of the soil and mix them with the nutrients at the top of the soil, which makes the soil fertile for plants. Their tunnels also allow oxygen to travel the roots of a plant more easily.
If you pick up two earthworms and the first feels very slimy near the clitellum and the second does not, what can you conclude about the first earthworm?
The first one must have recently mated but not yet produced a cocoon.
What similarities exist between the hydra's sexual reproduction and the earthworm's? What differences exist?
The earthworm is hermaphroditic and the hydra can be as well. However, although the hydra can sometimes mate with itself, an earthworm cannot.
Why don't planarians need circulatory systems?
Planarians do not need circulatory systems because the intestine is so highly-branched that all cells are near it, so they can get their food directly from the intestine.
If a flatworm has no complex nervous or digestive systems, is it most likely free-living or parasitic?