Plants and animals are organized into levels of increasing complexity: cells, tissues, organs, organ systems, and organisms.
What is one feature that is common to all levels, and how does it benefit the organism?
At each level, the parts of an organism (such as the skeletal system and the excretory system, or the stomach and the
pancreas) are able to function independently of each other. This ensures that damage to one part does not destroy the
entire organism.
At all levels, the parts of an organism are surrounded by outer layers (such as cell membranes and human skin) that are
permeable to some extent. These outer layers form a barrier against harmful substances while allowing necessary
particles to enter and exit.
At all levels, the parts of an organism can be repaired or replaced (for example, by growing scar tissue), or else the
organism has more parts than it needs (such as two kidneys) so that it can still function if one is destroyed. This ensures
that damage to one part does not destroy the entire organism.
At all levels, the parts of an organism are arranged in a branching pattern (such as a tree’s roots or a human hand), with
increasingly smaller units branching out from a larger central unit. This arrangement allows the smaller units to spread
out over a large area, while the central unit is relatively protected from harm.