Variation

CHAPTER 14: VARIATION 1

CHAPTER 14 : VARIATION

2.1 Variation in Organisms Activity 1 : Complete the table to compare continuous variation and discontinuous variation

Continuous variation Discontinuous variation

Differences are slight and grade into each other Differences

Slight with intermediate Intermediate

Determined by One or a very few genes

Graph

Normal distributionType of

distribution

Influencing factor Genetic factor

Cannot be inherited Inheritance

Activity 2 : Complete the graphic organizer showing the effects of genetic factors on variation.

1.Genetic recombination by c…………... o…………….

during meiosis

2.Independent assortmentof

c…………………

Random f…………………………

between ovum and any spermMutation

Effects of genetic factors on variation


Activity 3 : Match the sequence of events of crossing over during prophase 1.


Activity 4 : Name the type of chromosomal mutation.

Type of mutation Name


Structured items:1.

TABLE 15.1

Colour of flower Group of Hibiscus

Red A and C

Yellow B and D

TABLE 15.2

(a) What is the type of variation shown by the table 15.3 ?

Trait Type of variation

Height Continuous variation

Colour of flower Discontinuous variation

[2 marks ]

(b) Base from the investigation , what is meant by continuous variation ?

__________________________________________________________-

-__________________________________________________________

[ 1 mark }

Group of

Hibiscus

A B C D

Height range 151-155 cm 156-160 cm 161-165 cm 166-170 cm

Number of tree 6 9 10 5


(c)(i) Using results from table 15.1, draw a histogram of number of Hibiscus

tree against the height range (cm).

(ii) Joint the midpoint of each bar to draw a smooth curve .

(iii) Using results from table 15.3 plot a bar graph of number of people against

the ability to roll tongue. [5 marks ]

(d) State the factor that can cause this type of variation for each trait stated.

Traits Factors that cause variation

Height

Tongue Rolling

[2 marks ]

(e) Explain how the students conducted the investigation to determine the

type of variation in the height of people ? [3 marks ]

2.

Features :

* Broad forehead

* Short neck and limbs

* Almond-shaped eyes with folded eyelids

* Thick protruding tounge

* Mental retardation

DIAGRAM 15.3

Diagram 15.3 shows a group of children with a genetic disease due to mutation .

(a) State the genetic disease based on diagram 15.3 . [1 mark ]

(b) What is the type of that mutation ? [1mark ]


(a) How many chromosomes do the children have ? [1 mark]

(b) Mutation are caused by agents called mutagens .

Give two examples of mutagens . [2marks ]

( f ) How do mutagens caused mutation ? [2 marks]

( g ) Table 15.4 below shows genetic diseases caused by chromosome mutation.

Fill in the blank by using the word given .

Male Klinefelter’s syndrome Female Jacob’s syndrome

Turner’s syndrome Male and Female

DiseaseNumber of

Chromosomes

Chromosomes

involved Sex

( 44 + XO )Absence of one sex

chromosome

( 44 + XXY )An extra X

chromosomes

TABLE 15.4 [4marks ]


Essay Items.

1.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

2..

Type of

finger

prints

Curves Right Loops Whorl Left Loops

DIAGRAM 15.4

Diagram 15.4 shows different variation among human beings.

(a ) Determine the type of variation in Diagram 15.4 and 15.5. Give the reasons.

[4 marks]

(b) (i) What are the differences between continuous and discontinuous variation?

(ii) State the factors that cause variation in humans .

[6 marks]


(c) Base from the statement above, explain the three sources of genetic factors

during sexual reproduction [10 marks]

There are three sources of genetic factors in sexual reproduction events : Crossing over during meiosis 1 Independent assortment during meiosis Random fertilisation


ANSWER :2.1 Variation in Organisms Activity 1 : Complete the table to compare continuous variation and discontinuous variation



Differences are discreet and clear cut

Slight with intermediate Intermediate No intermediates

A large number of genes Determined by One or a very few genes

Graph


distributionDiscrete distribution

Environmental factor Influencing factor Genetic factor

Cannot be inherited Inheritance Can be inherited


Activity 2 : Complete the graphic organizer showing the effects of genetic factors on variation.

1.Genetic recombination bycrossing overduring meiosis

2.Independent assortmentof

chromosomes

Random fertilisation

between ovum and any spermMutation

Effects of genetic factors on variation


Activity 3 : Match the sequence of events of crossing over during prophase 1.


Activity 4 : Name the type of chromosomal mutation.

Type of mutation Name

Deletion

Duplication

Inversion

Translocation


Structured items:1.

TABLE 15.1

Colour of flower Group of Hibiscus

Red A and C

Yellow B and D

TABLE 15.2

(c) What is the type of variation shown by the table 15.2 ?

Trait Type of variation

Height Continuous distribution

Colour of flower Discontinuous distribution

[2 marks ]

(d) Base from the investigation , what is meant by continuous variation ?

There is a complete range of measurements for height from 151 cm to 170 cm

[1 mark ]

(c)(i) Using results from table 15.1, draw a histogram of number of Hibiscus

tree against the height range (cm).

Group of

Hibiscus

A B C D

Height range 151-155 cm 156-160 cm 161-165 cm 166-170 cm

Number of tree 6 9 10 5


(ii) Joint the midpoint of each bar to draw a smooth curve .

Number of Hibiscus tree

10 8 6 4 2

Height range (cm)

151- 156- 161- 166-

155 160 165 170

(iii) Using results from table 15.3 plot a bar graph of number of Hibiscus tree

against the height. [5 marks ]

Number of Hibiscus tree

14

12

10 Height (cm)

(d) State the factor that can cause this type of variation for each trait stated.

Traits Factors that cause variation

Height Genetic and environmental factor

Tongue Rolling Genetic factor

[2 marks ]

(e) Explain how the students conducted the investigation to determine the type of

variation in the height of Hibiscus tree ? [3 marks ]

-The height of each tree is measured using the measuring tape/ruler.

- The height is grouped into five classes of height range


- The height range is recorded in a frequency table.

- A histogram is drawn to show the normal distribution

[ marks ]

2.

Features :

* Broad forehead

* Short neck and limbs

* Almond-shaped eyes with folded eyelids

* Thick protruding tounge

* Mental retardation

DIAGRAM 15.3

Diagram 15.3 shows a group of children with a genetic disease due to mutation .

(a) State the genetic disease based on diagram 15.3 . [1 mark ]

Down Syndrome

(b) What is the type of that mutation ? [1mark ]

Chromosomal mutation

(c) How many chromosomes do the children have ? [1 mark]

47 chromsomes

(d) Mutation are caused by agents called mutagens .

Give two examples of mutagens . [2marks ]

Radioactives radiation , X-rays , ultraviolet light , gamma rays , chemical

substances , formaldehyde , pesticides .

( f ) How do mutagens caused mutation ? [2 marks]

Chromosomal mutation -changes in the structure of chromosomes or the

number of chromosomes.

Gene mutation -Chemical change in the structure of gene, it may also alter


the DNA or genetic code.

( g ) Table 15.4 below shows genetic diseases caused by chromosome mutation.

Fill in the blank by using the word given .

Male Klinefelter’s syndrome Female Jacob’s syndrome

Turner’s syndrome Male and Female

DiseaseNumber of

Chromosomes

Chromosomes

involved Sex

Turner’s

syndrome( 44 + XO )

Absence of one sex

chromosomeFemale

Klinefelter’s

syndrome( 44 + XXY )

An extra X

chromosomesMale

TABLE 15.4 [4marks


Essay Items.

1.

2.

Type of

finger

prints

Curves Right Loops Whorl Left Loops

DIAGRAM 15.4

Diagram 15.4 shows different variation among human beings.


(a ) Determine the type of variation in Diagram 15.4. Give the reasons.

Discontinuous variation.

This is because different people has distinct type of finger print, either curve,

right loop, whorl or left loop. [4 marks]

(c) (i) What are the differences between continuous and discontinuous variation?



Differences are discreet and clear cut

Slight with intermediate Intermediate No intermediates

A large number of genes Determined by One or a very few genes

Graph


distributionDiscrete distribution

Environmental factor Influencing factor Genetic factor

Cannot be inherited Inheritance Can be inherited

(ii) State the factors that cause variation in humans .

Genetic and environmental factors. [ 6 marks ]

(c) Base from the statement above, explain the three sources of genetic factors

during sexual reproduction [10 marks]

There are three sources of genetic factors in sexual reproduction events : Crossing over during meiosis 1 Independent assortment during meiosis Random fertilisation


No. Answer Mark

1(a) -Diagram 15.4 is (height ) continuous variation

-Because the differences between individuals are slight

and can be changed .

-Diagram 15.5 is ( type of fingerprints ) Discontinuous

variation

-Because the differences between individuals are obvious

and cannot be changed

1m

1m

1m

1m

(b)(i)


Differences between

individuals are slightly

with intermediates

There is a complete range

of measurements from

one extreme to the other

for a particular

characteristics.

Differences between

individuals are obvious

There is no gradual

change between two

extremes

2m

2m

(b)(ii) Genetic factors

environmental factors or both.

1m

1m

(c) Crossing over during meiosis

-During prophase I of meiosis, two homologous chromosomes

are paired up in a bivalent.

-The non-sister chromatids break at the chiasma.

-Segment of the chromatids exchange places .

-The exchange of genetic materials between the chromatids

results in new , different genetic combination of genes from the

1m

1m

1m


parents.

-The new genetic combination result in variation .

Independent assortment during meiosis

-During metaphase I of meiosis , homologous chromosomes

arrange themselves randomly at the equator.

-The random arrangement and separation of each homologous

pair is independent of one another.

-Independent assortment produces various genetic

combinations in the gametes .

Random fertalisation

-Each gametes has a unique set or combination of genes .

-A male gamete can fertilise any of the female gametes, .

-so, the fertalisation between a male gamete and a female

gamete occurs randomly.

-As a result , a zygote is formed with variety of gene

combination.

-With random fertilasation , variations occur in the offspring.

1m

1m

1m

1m

1m

1m

1m

1m

1m

1m

( Max:

10 marks )

Variation

Documents

variation chapter

different variation

variation height tongue

marks g table

d table

mark b mutation

type of chromosomal

marks b base