cells, human reproduction and...

Cells, Human Reproduction and Heredity4

4-5EXPERIMENT 4.1

Examining the different parts of a light microscope2. Referring to the information in the table below, examine the various parts of the microscope

carefully. Then label the diagram of a microscope in Fig. (a).

(a) objective (b) clip

(c) diaphragm (d) mirror

(e) eyepiece (f) coarse adjustment knob

(g) fine adjustment knob

3. (a) The magnifications of the three eyepieces are 5 X, 10 X and 15 X.

(b) Which eyepiece is the longest? 5X

(c) Which eyepiece is the shortest? 15X

(d) Eyepieces of greater magnifications are ( shorter / longer ).

4. (a) The magnifications of the three objectives are 4 X, 10 X and 40 X.

(b) Which objective is the longest? 40X

(c) Which objective is the shortest? 4X

(d) Objectives of greater magnifications are ( shorter / longer ).

5. (a) What is the magnification of the microscope when you are using a 5X eyepiece and

a 4X objective to observe an object? Show your calculation.

5X 4X 20X× =

(b) What is the highest magnification you can get with this microscope?

15X 40X 600X× =

Unit 4 Cells, Human Reproduction and Heredity2

4-7EXPERIMENT 4.2

Using a light microscope8. Draw what you see and write down the magnification.

P

Magnification: ( )

9. Note the nature of the image observed:

(a) Under the microscope, the letter is seen as d .

Comparing with the object, the image is magnified ( magnified / diminished ) and

inverted ( upright / inverted ).

(b) (i) Move the slide to the left. What happens to the image?

The image moves to the right ( left / right ).

(ii) Move the slide towards you. What happens to the image?

The image moves away from ( towards / away from ) me.

11. Draw what you see and write down the magnification.

Specimen: Cork

Magnification: ( )

(a)

Thread

( )

(b)


Table salt

( )

(c)

4-11Thinking

What is the purpose of lowering a cover slip onto the stain?

To reduce water loss of the specimen and prevent the objective lens from getting wet

4-11EXPERIMENT 4.3

Examining ox eye cells5. Draw a labelled diagram of several cells in the space provided.

Magnification: ( )

4-13Thinking

What is the purpose of adding iodine solution to the epidermis?

To stain the cells so that we can observe the structures of the cells more clearly


4-13EXPERIMENT 4.4

Examining onion epidermal cells6. Draw a labelled diagram of several cells in the space provided.

Magnification: ( )

4-14Activity 4.1

Examining the photomicrographs of different types of cellsExamine the different cell types. Complete the table below to summarise the structures of animal

cells and plant cells (‘✓’ – present; ‘✗’ – absent).

Structure

Animal cells Plant cells

Human cheek cells

Human kidney cell

Chicken red blood

cell

Epidermal cells in an

onion

Leaf cells in a crop

plant

Leaf cells in a moss

Cell membrane ✓ ✓ ✓ ✓ ✓ ✓

Cell wall ✗ ✗ ✗ ✓ ✓ ✓

Cytoplasm ✓ ✓ ✓ ✓ ✓ ✓

Nucleus ✓ ✓ ✓ ✓ ✓ ✓

Chloroplasts ✗ ✗ ✗ ✗ ✓ ✓

1. Based on your observations, which structures are common to animal and plant cells?

They have a cell membrane, cytoplasm and a nucleus.

2. What are the key differences between animal and plant cells?

Plant cells have a cell wall. Some plant cells have chloroplasts.


4-16Activity 4.2

Examining the photomicrographs of the full set of chromosomes found in human body cells

1. How many chromosomes are there in a human body cell? 46

2. Do the male and female human body cells contain the same type of sex chromosomes?If not,

what are they?

No, a male has one X and one Y chromosome; a female has two X chromosomes.

4-19Activity 4.3

Watching a video clip about cell division1. Why is it necessary for a cell to divide?

It is for the growth of living things.

2. What happens to the genetic materials just before a cell divides?

Each chromosome makes a identical copy of itself.

3. What ensures that the two daughter cells contain the same genetic material?

Cell division is an very organised process.

4. All cells in your body contain the same genetic material. Suggest how they can develop

different structures to carry out different functions.

They are speciallised into different types of cells (cell differentiation).

4-21EXPERIMENT 4.5

Examining various tissues in a pig’s liver and lung (Demonstration)

2. (a) What is the colour of the lung? pink

(b) Why does the lung have such a colour?

It contains many blood capillaries.

3. (a) What is the colour of the liver? pink

(b) Why does the liver have such a colour?

It contains many blood capillaries.


4. Try to identify the tissues present in each organ. Put in a ‘✓’ if the tissue is present and a ‘✗’ if

the tissue is absent.

Lung Liver

Is epithelial tissue present? ✓ ✓

Is connective tissue present? ✓ ✓

Is blood present? ✓ ✓

Is nervous tissue present? ✓ ✓

Is muscular tissue present? ✓ ✓

4-23EXPERIMENT 4.6

Examining a human torso model (Demonstration)

1. Your teacher will show you a human torso model. In the head region of the model, identify four

external organs that are responsible for detecting changes in the environment.

eyes ears nose skin

2. With the help of Fig. 4.17, identify three organs found in the model that form:

(a) the digestive system

liver stomach small intestine (or large intestine)

(b) the breathing system

nose lungs trachea

4-25TEST YOURSELF 4.1

1. A 2. B 3. C

4. (a) F (b) F (c) T (d) T

4-31Thinking

What is the advantage of an ovum having a size much larger than a sperm?

The egg is much larger than a sperm as it contains a large amount of food reserves in the cytoplasm. This is important for

the initial development of the embryo.


4-32Activity 4.5

Examining the chromosomes found in human sex cells1. How many chromosomes are there in a human sperm or ovum? 23

2. How is the number of chromosomes in a sperm or an ovum different from that in a human body

cell (as shown in Activity 4.2)?

The number of chromosomes in a sperm or an ovum is half of (half of /the same as)

that in a body cell.

3. If a sperm fuses with an ovum, what will be the number of chromosomes found

in the fertilised ovum? 46

4-33Thinking

Why does fertilisation always occur in the oviduct, but not in the uterus?

It is because the ovum remains alive for about 24 hours after ovulation. There is not enough time for the ovum to move

to the uterus. Hence, fertilisation always occurs in the upper part of the oviduct.


1. Fill in the blanks with the structures of the male and female reproductive systems.

Male reproductive system Female reproductive system

(b) ovum

(d) ovary

(f) oviduct

(a) sperm

(c) testis

(e) sperm duct

(g) penis (h) vagina

Type of sex cells

The place that produces sex cells

The tube that carries sex cells away from the place of production

The place that releases or receives sperms


2. Complete the table below to indicate the similarities and differences between a human sperm

and a human ovum.

Sperm Ovum

Shape looks like a tadpole looks like a sphere

Relative size smaller larger

Number of chromosomes 23 (one set) 23 (one set)

Food storage no yes

Movement can move cannot move

3. (a) F (b) T (c) T

4-53Activity 4.9

Analysing the passing of a trait in a family1. What is the trait of both parents (individuals 1 and 2)? curly hair

2. How many individuals in the second generation have straight hair? two

3. If individual 11 is a male with straight hair and individual 12 is a female with curly hair, complete

the above tree by drawing the correct symbols.

3 4

1 2

5 6

10 11 127 8 9

I

II

III

4-54Thinking

Can you give more examples of continuous variation in humans?

Pulse rate, foot length


4-55Thinking

Can you give more examples of discontinuous variation in humans?

Right-handed and left-handed, gender and fingerprints

4-56EXPERIMENT 4.8

Observing and analysing variations in humans

Part A Ability of tongue rolling

1. Can you roll your tongue? (Answer varies with students.)

2. Record the number of students that can or cannot roll the tongue in your class.

Able to roll the tongue Not able to roll the tongue

Number of students

3. Draw a bar chart in the space below to show the number of students with and without the

ability of tongue rolling in your class.

Ability of tongue rolling

Able to roll the tongue Not able to roll the tongue

Num

ber

of s

tude

nts

Number of students with and without

the ability of tongue rolling in the class

10

20

30

40


Part B Ear lobe

1. Which kind of ear lobes do you have?

(Answer varies with students.)

2. Count and record the number of students with free ear lobes and attached ear lobes in your

class.

With free ear lobe With attached ear lobe

Number of students

Percentage of students

3. Draw a bar chart in the space below to show the percentage of students with free ear lobes and

attached ear lobes in your class.

Types of ear lobe

Free ear lobe Attached ear lobe

Percentage of students with free ear lobesand attached ear lobes in the class

20

40

60

80

Per

cent

age

of s

tude

nts

(%)

Part C Hand span

1. Measure your hand span with a ruler to the nearest cm.

My hand span is (Answer varies with students.) cm.


2. Record the hand spans of all students in your class below.

Hand span (cm) Number of students Hand span (cm) Number of students

< 10 15 – 16

10 – 11 16 – 17

11 – 12 17 – 18

12 – 13 18 – 19

13 – 14 19 – 20

14 – 15 > 20

3. Draw a histogram in the space below to show the distribution of hand span among the students

in your class.

010 12 14 16 18 20 22 24 26

Distribution of hand span among the students in the class

2

4

6

8

Num

ber

of

stud

ents

Hand span (cm)

4. Based on your histogram, find out the following:

(a) The longest hand span in your class is cm.

(b) The shortest hand span in your class is cm. (Answer varies with students.)

(c) Most students have a hand span of cm.

(d) My hand span falls into the ( lower / middle / higher ) range of the class.


5. (a) Describe the shape of the graph.

The largest number of people have the mean hand span and there are very small numbers at the two extremes.

(b) What can you conclude about the distribution of hand span of your class?

There is a continuous range of intermediate lengths of the hand span among students in the class.

4-64Makers ’ Lab 4.1

Making a DNA model Makers’ finding

1. How many parallel chains is a DNA model made up of? two

2. What kinds of base pairing can you find in the origami model of DNA?

pairing with

pairing with

TA

GC

Makers’ creation

Draw the design of your DNA model in the space below.


4-68Activity 4.10

Finding the instructions encoded in DNA1. What is the base sequence in the DNA segment that codes for the following protein?

Ala – Tyr – Gly – Ser - Leu

GCCTACGGGTCACTA

2. What protein will be formed from a DNA segment with the following base sequence?

(a) CATCATCATCATCAT

His HisHis His His– – – –

(b) AAAAATGGGGCC

Lys GlyAsn Ala– – –


1. C 2. A

3. Fill in the blanks to illustrate the relationship between nucleus, chromosome, DNA and base

pairs.

(a) nucleus (b) chromosome (c) DNA

(d) G (guanine) (e) base pair

4-77REVISION EXERCISE

A. Multiple-choice Questions1. C

5. D

2. A

6. A

3. C

7. D

4. C

8. D

B. Short-answer Questions 9. (a) Which cell did he observe wrongly? cell A

(b) Explain your answer for (a).

Cell A contains chloroplasts so it should be a plant cell. Thus, it should have a cell wall.

(c) Suggest where you can find cell C. plant root

(or other reasonable answers)


10. (a) Name the structures labelled.

A: sex glands B: urethra

C: penis D: sperm duct

E: testis

(b) What are the functions of structure E? Put a “✓” in the correct boxes.

Produce sperms ✓

Provide nutrients for the sperms

Produce semen ✓

(c) A couple wants to prevent pregnancy permanently. Suggest one male birth control method

to them. Briefly explain the principle of the method.

Male sterilisation, structure D is tied and cut so that there is no sperm in the semen.

11. (a) What do the circles in the tree represent? What do the squares represent?

Circles represent females and squares represent males.

(b) How many pairs of individuals in the tree have children?

3

(c) From whom could Susan have inherited her big nose?

individual 8 (her father), individual 3 (paternal grandfather) and individual 1 (maternal grandfather)

(d) Which part of the human cell contains the genetic material that determines this trait?

nucleus

cells, human reproduction and...

Documents