Background Information

In sexual reproduction, development of a new individual of species begins with the zygote after fertilization has taken place. The zygote after undergoing certain processes which included cell division and cell differentiation grows into an embryo which eventually grows and develops into a new organism

In oviparous animals, the young ones are hatched from the eggs, in such organism, the new organism can undergo several other changes in stages before it can be like the adult in form and structure.

This is called metamorphosis. In some others, where the eggs hatch into a miniature (adult) an organism that looks like the adult. It is called incomplete metamorphosis, but if it hatches into a larva, it undergoes complete metamorphosis. In most mammals where viviparity occurs, the young ones develop into feotus in the womb before they are born, after birth they begin to develop into infant stage, adolescence stage and full grown adult.

After fertilization at the upper part of the oviduct, It takes around days 14 – 21 of the menstrual cycle for the zygote formed to be developed into an embryo and get implanted in the uterus. This stage is the pregnancy stage and as the embryo grows, the uterus becomes bigger to contain it. The embryonic membranes, amnion and chorion begin to form. Within 10 – 12 weeks, all major organs are formed in the embryo and from that time onwards the embryo becomes a foetus.

Placenta:

This is a disc shaped structure formed where the chorionic villi is embedded in the uterine endometrium tissue. It is linked to the foetus by the umbilical cord.

Arteries from the foetus move through the umbilical cord to the placenta, in the villi of the chorion, there are capillaries which branch from this artery. Materials pass from the blood into the capillaries in the villi. Umbilical veins carry the blood to the foetus.

The circulatory system of the feotus (embryo) is separate from that of the mother. The (foetus) embryo's blood stays within the capillaries of the chorionic villi as illustrated or shown in figure5.4. The blood stream of the foetus and that of the mother do not mix.

BIRTH

During the last week of pregnancy, Oestrogen level in the women rises, Also oxytocin, a hormone secreted by the posterior pituitary gland together with the oestrogen rise, bring about the contraction of the uterus over and over. This is called labour. This labour contraction pushes the baby's head against the cervix, stretching and passing through the cervix, the baby eventually is pushed out of the mother through the vagina.

After pollination, the male gametes will still need to move to the egg in the ovary which is still far from the stigma. To reach the egg cell, the pollen grain germinates to produce a pollen tube, which grows to reach the egg cell. Before germinating, the intine of the pollen grain grows out as a pollen tube through a pore or rupture at the exine.

Energy is required for this and it is obtained from stored food in the pollen grain. The pollen tube grows through the loosely packed cells of the style, into the ovary, it secretes enzymes which digest the cells inorder to provide it with necessary nutrients and energy for growth. When the pollen tube enters the embryo sac through the micropyle of the ovule, the tube nucleus disintegrates. The two male nucleus are now released into the embryo sac. Immediately one fuses with the egg cell to form a diploid (2n) zygote; the other migrates to the center of the embryo sac where it fuses with the two fused polar nucleus to form a triploid (3n) primary endosperm cell. This is called double fertilization and it is common but peculiar to flowering plants. Only one pollen tube enters an ovule. If the ovules are many or more than one, separate pollen tubes enter each separately.

After fertilization, the zygote develops into an embryo, the primary endosperm develops into endosperm tissue, the ovule becomes a seed while the ovary turns to a fruit.

Germination: Seeds can remain alive for long in a dry condition without germinating. They are said to be in dormancy period or resting period at such time. During favourable conditions, seeds can germinate into seedlings.

Germination of seeds refers to all changes that take place when the embryo in a seed starts its growth and development to become an independent seedling.

Conditions necessary for germination
External conditions: Sufficient water; suitable temperature, and adequate oxygen supply.

Dispersal of fruits and seeds

Seed dispersal helps to reduce competition among members of the same species. It also produces favourable environmental conditions for the survival of the species.

1. After fertilization, a zygote is formed which develops into after a few days

2. A development that involves these steps
Egg → Larva → Pupa → Imago is a case of phase of development in an organisms called

3. The whole structure containing the egg in the geasshopper is called

4. The eggs of a cockroach hatches out into a which looks like the adult except that it is wingless.

For question 5 – 9 write down in the spaces provided what the larva of eachof the insects are called.

10. Development or metamorphosis of amphibians is controlled by the hormone

11. At what stage of development of a toad does the coiled intestine appear ?

12. Write two functions of the jelly covering in the egg of a toad

13. What stages of development of a frog is shown in the figure 5.8 a and b above ?

14. At what stage of development in a frog does it breath like a fish?

15. The caterpillar has pairs of spiracles.

16. The structure called Osmeterium in caterpillar is for

18. Label the major parts of the diagram of the pupal stage of a butterfly shown above

19. How many times does a female Tse-Tse fly need to mate in a life time

For questions 20 – 26, write into the space provided in the table, the type of metamorphosis carried out by each of the insects in the table.

Diagram of the Amniotic egg of a chicken showing its development

Use the diagram to answer question 26 to 28

Label the: (26) air space; (27) The amniotic fluid; (28) The embryo.

29. In mammals, the baby receives nourishment from the mother through the

30. The two hormones that are involved in labour which results to birth are and

31. After fertilization in flowering plants, the zygote develops into an embryo while the primary endosperm gives rise to endosperm tissue, the ovule becomes a and the ovary itself turns to a

32. Write down three main functions of a seed

Expression Exercise

1a. What is moulting in an insect?

b. What hormone is involved in the process of moulting?

c. State two similaries and two differences in the life cycle of a cockroach and that of a butterfly

Similarities:

Differrence:

2a. What is parthenocarpy?

b. Explain how an Aphid reproduces parthenogenetically:

c. Write one similarity in the life cycle of a housefly and that of a mosquito

3a. Write three functions of the placenta in the development of foetus in the uterus

b. How does a flowering plant carry out double fertilization?

4a. How does epigeal germination differ from hypogeal germination?

b. Write three examples of plants that carry out epigeal germination and three examples of plants that carries out hypogeal germination.

(a) Identify the type of dry fruit in the diagram above and label the parts indicated

(b) Write two differences between a legume and a capsule dry fruits.

Label each of the diagrams in figure 6.7B and 6.7C

b. Write two example each, of the various types of fruits listed below

1. True fruits
2. False fruits
3. Simple fruits
4. Aggregate fruits
5. Composite fruits

Practical Activities

Finding and Examining toad eggs and Tadpoles

Materials/Apparatus
Glass jars, hand lens

Method/ procedure

1. Pair up your selves and discuss where you are most likely to see toad eggs and tadpoles.
2. You can visit any nearby and suitable pond or stream close to the school compound.
3. Collect strings of toad eggs, feel them and gently place them with pond water in the glass jar after careful observation.
4. Also collect as many tadpoles as you can, but put pond weed in the jar containing the tadpoles.
5. Examine the stages of development of the tadpoles with the hand lens and see if you can observe various stages of development among the tadpoles.
6. Also use the hand lens to examine the eggs, note the colour and also the smell.

Questions

1(i) Write down where you found the strings of eggs?

(ii) What did you observe about the different sizes of the tadpoles and their stages of development

(iii) Why do you have to put pond weed into the glass jar containing the tadpoles

(iv) What is the colour and smell of the eggs (if you perceived any smell)

(v) What does your observation of the tadpoles in the pond or stream lead you to conclude about parental care among toads

2. Discovering the parts of a fruit

Material/Apparatus needed
Certain fruits such as mango, tomato, Coconut, Scalpel or knife

Method/procedure

1. Using the scalpel or knife, cut each of the fruits into two equal halves. Using the fruit stalk as the starting point.
2. Observe each section carefully and compare them with the drawings in figure 6.8A-C
3. Try to identify all laballed parts
4. Try to draw each section of the fruits you cut and label your diagram carefully using the diagram in fig 5.95 as a guide.

Questions

(i) What type of fruit can each of the fruits be categorized into. State the category in the space below.

1. Coconut
2. Mango
3. Tomato

(ii) Which parts of the flower is represented as shriveled remains on the tomato fruit.

(iii) State two ways by which tomato differes from the other fruits

Test of Practical Work

Classify each of the fruits displayed in the diagram according to the following

State one method of seed dispersal for the plants whose fruits are shown in a, b, c, and d.

(a) The diagram above is divided into A and B, state the right name for A and B

(b) What class or groups of vertebrates can they be found?

Can they be found in males or females?

(c) How does exchange of gases take place in the foetus?

(d) How is the foetus blood neatly separated from having direct contact from that of the mother though exchange of materials still take place?

Nov 1990q3
1. Study the diagrambelow and use it to answer question 1

(a) Name the parts labelled I - V

(b) In which of the labelled parts is food stored

June 1994Q7 a-b
3. Study the diagram below and use it to answer Question 3

(a) Name the parts labelled I - V

(b) What is the function of the part labelled I

May/June 2001 Q1
4. You are provided with Specimen A: Tadpole with internal gill and limb;
specimen B: Mosquito pupa.

(a) Identify Specimen A and B without reasons

(b)i Examine the ventral part of specimen A and list four observable feature

(ii) Suggest the diet of specimen A, giving reasons

(iii) Identify one feature on the ventral part of specimen A which is not used by the organism at this stage. Give a reason for your answer.

(c) Describe two observable features in each specimens A and B which suggest their Habitats.

(d) Make a labelled drawing of 4cm – 10cm long of the lateral view of specimen A.
(Draw in your biology practical note book).

June 2003 Q 1
5. You are provided with specimen A in group H a bony fish (Tilapia) and specimen B in group I

a Tadpole

1. Name the adult stage of specimen B
2. List four external features common to specimen A and B

ii. In a tabular form, list four observable differences between specimens A and B

iii Make a labelled drawing of 8cm to 10cm long of specimen A to show its external features
(Draw in your practical biologgy note book)

iv. State, how four of its external features adapt the specimen A to its environment

V Name two classes of food that specimen A provides in human nutrition.

June 2000 Q1

6. Specimen A: Bean seed Specimen B: Fresh fruit of pride of Barbados/Bean pod

(a)i. Identify specimen A and B without reasons

ii. Give four differences between specimens A and B

specimens A

specimens B

Using sharp knife, scalpel or blade, cut specimen B into two equal halves to expose the internal structure;

(b)i. Make a labelled drawing of 8cm to 10cm to show the observable internal structures of specimen B.
(Draw in your Biology practical note book)

ii. State the dispersal mechanism of specimen B

JUNE 2000 WASSCE BIOLOGY PRACTICAL - QUESTION

You are provided with a bean seed as specimen A, a pride of barbados fruit (pod) as specimen B

1(a) (i) Identify specimens A and B without reasons[2marks]

(ii) Give four differences between specimens A and B [4marks].

Using a sharp knife, scarpel or blade, cut specimen B into two equal halves to expose the internal structures;

(b) (i) Make a labeled drawing of 8cm to 10cm long to show the observable internal structures of specimen B. [9marks]