BACKGROUND:
Higher plants and animals require more
complex structures in order to maintain their bodily processes. Some
structures found in plants are organs but these are difficult to compare with
those of an animal. Such things as limbs on a tree and plant stems are organs
but in the classical sense we only consider organs to be structures like the
heart or brain. Just as tissues and cells grouped together to form a higher
system, organs do the same. A group of organs working together to perform a
task is called an organ system. An example of an organ system is the
circulatory system which includes the heart, blood, blood vessels, and lymph
vessels in the animal kingdom. In higher animals, there is an organ system for
almost every life process that takes place.
An organism is considered the ultimate
level of organization. At this level all other levels are working together to
make the organism a complete living thing. Thus the definition of an organ
system is: A system that is constituted to carry on the life processes by
means of organs that are functionally independent but mutually dependent.
PROCEDURE:
- Use the worksheet to review organs,
tissues, and cells of a protozoa, a mushroom, a flower and a dog. Some
protozoa have no organs and tissues. It just has one cell. The different
organelles act as the center of activity. Protozoa are so small that they do
not need organs to circulate food, fluid, or wastes. A mushroom is a
multicellular fungus whose external features represent its reproductive
organs. A dog has internal organs composed of different types of tissues, just
like humans.
