A good introduction to learning about the characteristics of living things is to get the kids brainstorming as to what makes a living thing living.
I do this with my 7th graders but it can be modified for any grade level.
Set up a petri dish about half full with water on an
overhead projector. Make sure students have some paper and are ready
to write their observations. Tell the students that you will be putting
something in the dish and to watch the screen closely. Carefully, go
into a drawer or some hidden compartment to get a glob of duco-cement (a type
of glue) on the end of a pair of forceps. Drop it in the water and let the
students write down as many observations as they can.
The duco-cement swirls and moves rapidly as it congeals in the water. It
has the appearance of a protist. Observations kids may make are :
it moves, it changes color, it spins...
If you drop a second one in, they can observe them "fighting" or perhaps even eating.
Practice this before you do it for the class. it's difficult to get
just the right drop size.
This leads to a great discussion of living things since they will all
insist that "it must be living - it moves!"