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The Circle of Willis.
Circle of Willis in the head between branches of internal carotid artery Micro-Anastomosis between arterial supply of some organs
cerebral arterial circle (circle of Willis)
The black circle in the eye is called the pupil.
The green hydra (Chlorohydra viridissima) gets its colour from green algae which live inside its tissues in a mutually beneficial relationship. The algae living inside the hydra benefit from having a sheltered safe environment and obtain food by-products from the hydra. The hydra also benefit from algal products. from www.offwell.free-online.co.uk/hydra.htm Hydra eat one celled animals, small crustaceans, worms, insects and other tiny animals. They are also reported to eat small fish fry in the aquarium, where they do occasionally show up. Hydra have a saclike body and a circle of tentacles at around the body opening. This opening is used for both taking in food and eliminating wastes. from http://www.naturalaquariums.com/inverts/hydra.html So this would make them heterotrophs. AliceJM
The radius is the distance between the center of a circle and a point on the circle
A part of a circle between two points on a circle is called is called an arc.
it is between the arctic circle and antarctic circle.
A segment between two points on a circle is
arc
An arc is part of the circumference of a circle
Opposite hemispheres.
A circle is complete and a cycle repeat
An arc is a part of the circumference of a circle.
The longest distance in a circle is its diameter.
It is 90 degrees between the circle's diameter and its tangent
A whole continent exists between the Antarctic Circle and the South Pole.