PRACTICAL ACTIVITIES TO DEMONSTRATE CONTINUOUS VARIATIONS

Height of students

Students should work in pairs, use chalk and metre rule to mark level of top of head onto the wall.
Or door as one student stands straight without shoes, next to the wall or door.
The height for each student is recorded on chalk board.
The frequency distribution of height is recording as the height is grouped into various classes.
A histogram to represent frequency against height is drawn.
The normal bell shaped curve is observed.

Table of Contents

The number of students who can roll their tongue is recorded as well as the number of non-tongue rollers.
The ratio of tongue-rollers to non-tongue rollers is worked out.
Gene for the ability to roll the tongue is dominant, therefore is expected more tongue rollers.

Mitosis

Plasticene is used to represent number and shapes of various chromosomes e.g. 8 in Drosophila melanogaster.
Each stage of mitosis illustrated e.g. interphase.
Each is rolled to appear long is and coiled, prophase is each made into a ball and then shaped to the appropriate length; and split into two to represent chromatids.
Centromeres for different chromosomes can be illustrated in different positions.
Each stage of mitosis is illustrated and telophase can be illustrated by surrounding the “chromosomes” with a long many drawn plasticene to represent cell membrane.
It is manipulated to show how telophase takes place.

Meiosis

The same procedure is followed.
Plasticine with contrasting colours is used to show clearly gene mixing in crossing over.
Each pair of homologous chromosomes is represented by plasticene with two different colours e.g. red (paternal) blue for maternal chromosome.
All the steps in the two stages of meiosis are illustrated up to the production of four haploid gametes.

The finger prints for each student’s thumb, forefinger and middle fingers of the left hand are imprinted on a white paper.
A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad.
For best results students work in pairs.
Observations are made at all forefingers, thumb prints and differences noted.
The main patterns are noted. It is also noted that no two, fingerprints are exactly similar.