BIOLOGY FORM 5BIOLOGY FORM 5

UNDERSTANDING UNDERSTANDING VARIATIONVARIATION

IN ORGANISMSIN ORGANISMS

LEARNING LEARNING OUTCOMESOUTCOMES To state the importance of variation in To state the importance of variation in

organisms.organisms.

To give examples of variation in To give examples of variation in humanshumans

To state the types of variationTo state the types of variation

To compare continuous & To compare continuous & discontinuous variation.discontinuous variation.

VARIATION IN ORGANISMSVARIATION IN ORGANISMS VARIATION :VARIATION : the differences which the differences which exist between living organisms as exist between living organisms as a result of their genotypes &/@ a result of their genotypes &/@ the environment.the environment.

To To withstand harsh environmentalwithstand harsh environmental conditions.conditions.

Examples : height, weight, blood Examples : height, weight, blood group, tongue rolling, eye colour group, tongue rolling, eye colour & sex.& sex.

TYPES OF VARIATIONTYPES OF VARIATION Two types : Two types : continuous & continuous &

discontinuous variation.discontinuous variation.

Continuous variationContinuous variation : :– Differences are slight. Determined by Differences are slight. Determined by

many genes &/@ environmental many genes &/@ environmental influence.influence.

– Bell-shaped normal distribution curve.Bell-shaped normal distribution curve.

– Examples : height & weight.Examples : height & weight.

Discontinuous variationDiscontinuous variation : :– The differences are discrete The differences are discrete

(separate) & clear-cut. (separate) & clear-cut. Determined by different alleles Determined by different alleles of one, two @ only a few genes.of one, two @ only a few genes.

– Not influenced by Not influenced by environmental factors.environmental factors.

– Examples : blood group, Examples : blood group, gender, tongue rolling & ear gender, tongue rolling & ear lobe type.lobe type.

Observe the colour of the hair and colour of the iris…

COMPARE & CONTRASTCOMPARE & CONTRASTCONTINUOUSCONTINUOUS DISCONTINUOUSDISCONTINUOUS

SIMILARITIESSIMILARITIES

Both refer to differences in inherited traits that exist among Both refer to differences in inherited traits that exist among members of a species.members of a species.

DIFFERENCESDIFFERENCES

Have no distinct categories into Have no distinct categories into which individuals can be placedwhich individuals can be placed

Have distinct categories into Have distinct categories into which individuals can be placedwhich individuals can be placed

Tend to be quantitativeTend to be quantitative Tend to be qualitativeTend to be qualitative

Are controlled by a large Are controlled by a large number of genes (polygenes)number of genes (polygenes)

Are controlled by a one gene or Are controlled by a one gene or a small number of genesa small number of genes

Are significantly affected by the Are significantly affected by the environmentenvironment

Are largely unaffected by the Are largely unaffected by the environmentenvironment