BACKGROUND:
Reproduction is important for the survival
of all living things. Without a mechanism for reproduction, life would come to
an end. There are two types of reproduction to learn in elementary grades,
asexual and sexual reproduction. Many teachers are afraid of discussing
reproduction, but if presented as a factual lesson it is easy for the students
to understand the principles without the standard giggles.
Asexual reproduction refers to simple cell
division that produces an exact duplicate of an organism. There are many
different types of asexual reproduction which can be discussed to show
students the variability of modes of reproduction. Some single-celled
organisms reproduce by simple cell division, this is called binary fission. In
this manner, the mother cell simply splits in half producing two daughter
cells. Some cells reproduce by unequal division of the cells, this is called
budding. In this process the bud forms as a knob on the mother cell. The
nucleus divides and identical parts go to the mother cell and the bud. The bud
may grow until it is as large as the mother cell and can form buds of its own.
In some cases buds remain attached to the mother cell. In others, they break
away and live as separate organisms.
Sexual reproduction involves the joining of
male and female sex cells. The sperm refers to the male sex cell and the egg
refers to the female sex cell.
PROCEDURE:
- As you discuss this with students, tell
them that trees, fish, flowers, and many other organisms have sperm and eggs.
Tell students to look at organisms on their way home, to see if they can
predict which ones reproduce by sexual or asexual means.
- There are some reproductive strategies
that are difficult to classify for students. Ferns, fungi, and some protozoa
reproduce by spore production. Spores are formed by divisions of special
mother cells and are released from the parent organism. A single spore
develops into a new organism.
- The worksheet shows students the
difference between asexual and sexual reproduction. The answers are as
follows: 1. yes; 2. in half; 3. little one celled creatures; 4. zygote 5.
female, male, a baby; 6. larger organisms with organs; 7. larger organisms
cannot simply divide, it is more efficient for little organisms to reproduce
in that manner.
