Reproduction in Plants and Animals ICSE Class 8: Asexual Methods, Flowers, Pollination and Human Reproductive Organs

What Reproduction in Plants and Animals is about

Weightage: CISCE publishes no question paper, marking scheme or chapter weightage for Class VIII Biology: your school sets and marks the exam. Reproduction in Plants and Animals sits in the Theme: Reproduction in Plants and Animals theme of the CISCE Curriculum for Upper Primary Classes (VI-VIII).Source: CISCE Curriculum for Upper Primary Classes (VI-VIII), RDCD 2016

Key concepts

Binary fission, budding and fragmentation

Binary fission ('splitting into two'): a single-celled organism divides into two equal daughter cells. The nucleus divides first, then the cytoplasm.

• Examples: Amoeba, Paramecium, bacteria.
• Under good conditions it repeats quickly, so numbers double at each division: 1 → 2 → 4 → 8 → 16.

Budding: a small outgrowth, the bud, forms on the parent. The nucleus divides and one part goes into the bud. The bud grows and separates to live on its own (or stays attached, forming a chain or colony).

• Examples: yeast (a fungus), Hydra (a simple animal).
• Unlike fission, the two parts are unequal at first.

Fragmentation: the body of the parent breaks into pieces (fragments), and each piece grows into a complete new individual.

• Example: Spirogyra, a filamentous green alga; a filament breaks into several pieces and each grows by cell division.

Worked example

One Amoeba divides by binary fission four times in a row, and every daughter divides each time. How many Amoebae are there at the end?

Try it first, then show the solutionSolution

1. Each fission doubles the number: 1 → 2 → 4 → 8 → 16.
2. After 4 fissions: 2 × 2 × 2 × 2 = 16.

Answer: 16 Amoebae

Spore formation and vegetative propagation

Spore formation: some organisms form tiny, light, single-celled spores inside a case called a sporangium. When it bursts, the spores spread by air. Each spore has a tough coat that protects it in dry, unfavourable conditions; when it lands on a moist, warm surface it germinates into a new individual.

• Examples: Rhizopus (bread mould), Mucor, ferns and mosses.

Vegetative propagation: new plants grow from vegetative parts (root, stem or leaf) of the parent, not from seeds.

Natural:

Part	Example	How
Stem tuber	potato	buds in the 'eyes' grow into new plants
Rhizome (underground stem)	ginger, turmeric	buds on the rhizome sprout
Bulb	onion	buds in the bulb grow
Runner	grass, strawberry	stems along the ground root at nodes
Leaf	Bryophyllum	buds in the notches of the leaf edge grow into plantlets
Root	sweet potato, dahlia	buds on swollen roots sprout

Artificial (done by people):

• Cutting: a piece of stem with nodes is planted in moist soil; it grows roots. Rose, sugarcane, money plant.
• Layering: a branch is bent down and covered with soil while still attached; once it roots, it is cut off. Jasmine, grapevine.
• Grafting: a cut shoot (scion) of one plant is joined to a rooted plant (stock) of a related kind, and they grow together. Mango, apple, rose.

Advantages: quicker than from seeds; all new plants are identical to the parent, so good qualities are kept; plants that make few or no seeds (banana, rose, sugarcane) can still be grown.

Worked example

Name the method and the plant part used: (i) a potato with 'eyes' grows new shoots (ii) a leaf lying on moist soil gives several tiny plants along its edge.

Try it first, then show the solutionSolution

1. (i) Natural vegetative propagation by stem tuber; the eyes are buds.
2. (ii) Natural vegetative propagation by leaf, as in Bryophyllum; buds in the leaf notches grow.

Answer: (i) Stem tuber (potato) (ii) Leaf buds (Bryophyllum)

Tissue culture

Tissue culture is an artificial method of growing many new plants from a small piece of tissue (a few cells) of a parent plant, in a nutrient medium under sterile (germ-free) conditions.

Basic process:
1. A tiny piece of tissue, usually from a growing tip, is cut from the parent plant.
2. It is cleaned and placed on a sterile nutrient medium (jelly with sugar, minerals and plant hormones) in a glass container.
3. The cells divide to form a shapeless mass of cells called a callus.
4. Pieces of the callus are moved to another medium with hormones that make them form shoots and roots, giving plantlets.
5. The plantlets are moved to pots of soil to harden, then planted out.

Example: orchids, banana, carnation, chrysanthemum and potato are commonly grown by tissue culture.

Advantages: thousands of plants from a tiny piece in a short time; all identical to the parent; disease-free plants; plants can be grown in any season.

Worked example

What is a callus in tissue culture, and why must the work be done under sterile conditions?

Try it first, then show the solutionSolution

1. A callus is the undifferentiated mass of cells that forms when the tissue piece divides on the nutrient medium.
2. The sugary medium would also feed bacteria and fungi, which would grow faster and spoil the culture, so everything is kept germ-free.

Answer: A mass of unspecialised cells; to stop microbes spoiling the culture.

The flower: four whorls

The flower is the reproductive part of a flowering plant. Its parts are arranged in four rings, or whorls, on the swollen tip of the flower stalk (thalamus or receptacle).

Whorl (outside to inside)	Made of	Function
Calyx	sepals, usually green	protect the flower in the bud stage
Corolla	petals, often brightly coloured and scented	attract insects for pollination
Androecium (male)	stamens: each has a stalk (filament) and a head (anther)	anthers make pollen grains, which carry the male gametes
Gynoecium (female)	carpels or pistil: stigma, style, ovary	stigma receives pollen; ovary contains ovules, each with an egg cell (female gamete)

Calyx and corolla are accessory (non-essential) whorls; androecium and gynoecium are the essential whorls, because they take part directly in reproduction.

A flower with both stamens and carpels is bisexual (mustard, hibiscus); one with only stamens or only carpels is unisexual (papaya, maize, cucumber).

Worked example

Which two whorls are called essential, and why? Name the parts of the gynoecium.

Try it first, then show the solutionSolution

1. Androecium and gynoecium, because they produce the gametes and take part directly in reproduction.
2. Gynoecium: stigma, style and ovary (with ovules).

Answer: Androecium and gynoecium; stigma, style, ovary

Pollination and its agents

Pollination is the transfer of pollen grains from the anther to the stigma of a flower.

• Self-pollination: pollen reaches the stigma of the same flower, or another flower on the same plant. Example: pea, wheat.
• Cross-pollination: pollen reaches the stigma of a flower on another plant of the same kind. It needs an outside agent and gives healthier offspring with more variation. Example: maize, papaya, mustard.

Agents of cross-pollination:

Agent	Three features of the flowers	Examples
Insects (entomophily)	large, brightly coloured petals; scent and nectar; pollen sticky or spiny so it clings to insects	sunflower, rose, mustard, salvia
Wind (anemophily)	small, dull, no scent or nectar; pollen light, dry, smooth and made in huge amounts; feathery stigmas and long filaments hanging out in the wind	maize, wheat, rice, grasses
Water (hydrophily)	small, inconspicuous; pollen light, carried on the water surface (often protected by a slimy covering); long stalks bring female flowers to the surface	Vallisneria, Hydrilla

Artificial pollination (mention only): people transfer chosen pollen by hand, using a brush, onto the stigma of another plant and then cover the flower with a bag. Plant breeders use it to produce new and better varieties (hybrids).

Worked example

A flower is small, green, has no smell, and has feathery stigmas hanging outside. Name its likely pollinating agent and give one more feature you expect.

Try it first, then show the solutionSolution

1. Dull, scentless flowers with feathery, exposed stigmas are wind-pollinated.
2. Expect light, dry pollen produced in very large amounts (or long hanging stamens).

Answer: Wind; light, dry pollen in huge amounts

Fertilisation (flow chart)

Fertilisation is the fusion of a male gamete with a female gamete (egg) to form a zygote.

In a flowering plant, in brief:

Pollen grain lands on the stigma → the pollen grain grows a pollen tube → the tube grows down through the style → it enters the ovule inside the ovary (through a tiny opening, the micropyle) → a male gamete from the tube fuses with the egg cell → zygote → grows into the embryo.

After fertilisation:

• the ovule becomes the seed (containing the embryo);
• the ovary becomes the fruit;
• sepals, petals, stamens, stigma and style usually wither and fall off.

So: ovule → seed and ovary → fruit.

Worked example

Arrange in order: zygote, pollen tube enters ovule, pollen lands on stigma, male gamete fuses with egg, pollen tube grows through style.

Try it first, then show the solutionSolution

1. Pollen lands on stigma → pollen tube grows through style → pollen tube enters ovule.
2. → male gamete fuses with egg → zygote.

Answer: Pollen on stigma → tube through style → tube enters ovule → gametes fuse → zygote

Human reproductive systems: main organs

Humans reproduce sexually. Males make sperms (male gametes) and females make eggs or ova (female gametes).

Male reproductive system:

Organ	Function
Testes (a pair, in a skin pouch called the scrotum)	produce sperms and the male hormone testosterone
Sperm ducts (vas deferens)	carry sperms from the testes towards the urethra
Glands (seminal vesicles, prostate)	add fluid that nourishes sperms and helps them move
Urethra and penis	carry sperms out of the body

The testes lie outside the abdomen in the scrotum because sperms develop best at a temperature slightly lower than body temperature.

Female reproductive system:

Organ	Function
Ovaries (a pair, in the lower abdomen)	produce eggs (ova) and the female hormones oestrogen and progesterone
Oviducts (fallopian tubes)	carry the egg from the ovary to the uterus; fertilisation takes place here
Uterus (womb)	a muscular, hollow organ where the baby develops
Cervix and vagina	the narrow neck of the uterus and the passage leading outside

Fertilisation of an egg by a sperm forms a zygote, which develops in the uterus into an embryo and then a baby.

Worked example

Name the organ where (i) sperms are made (ii) eggs are made (iii) fertilisation takes place (iv) the baby develops.

Try it first, then show the solutionSolution

1. (i) Testes. (ii) Ovaries.
2. (iii) Oviduct (fallopian tube). (iv) Uterus.

Answer: (i) Testes (ii) Ovaries (iii) Oviduct (iv) Uterus

Reproduction in Plants and Animals in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Asexual Reproduction and Tissue Culture
• Flower, Pollination and Fertilisation

Reproduction in Plants and Animals: key facts

Binary fission

$1\to 2\to 4\to 8;\text{after }n\text{ divisions: }{2}^n$

Equal daughter cells; Amoeba, bacteria.

Whorls from outside

$\text{calyx}\to \text{corolla}\to \text{androecium}\to \text{gynoecium}$

Last two are the essential whorls.

Stamen and carpel

$\text{stamen}=\text{filament}+\text{anther};\text{carpel}=\text{stigma}+\text{style}+\text{ovary}$

Male and female parts.

Fertilisation

$\text{male gamete}+\text{egg}\to \text{zygote}\to \text{embryo}$

In the ovule of a plant; in the oviduct in humans.

After fertilisation

$\text{ovule}\to \text{seed};\text{ovary}\to \text{fruit}$

Other parts wither.

Reproduction in Plants and Animals: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Reproduction in Plants and Animals

The question patterns to expect, and the method that works for each.

Tricks to remember Reproduction in Plants and Animals

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Can Children Always Grow? (Calyx, Corolla, Androecium, Gynoecium)

  The whorls from outside in.

  Use it when: Order of the flower whorls.

• Andro = man, Gyno = woman

  Androecium is the male whorl; gynoecium the female.

  Use it when: Naming the reproductive whorls.

• Show-offs and scatterers

  Insect flowers show off (colour, smell, nectar); wind flowers scatter (dull, light pollen, feathery stigmas).

  Use it when: Features of pollinating agents.

• OO-SF: Ovule → Seed, Ovary → Fruit

  Ovule and seed are both small; ovary and fruit are both the bigger container.

  Use it when: Changes after fertilisation.

• Fission = Fifty-fifty, Budding = Baby on the side

  Fission gives two equal halves; budding gives a small outgrowth.

  Use it when: Telling fission from budding.

Reproduction in Plants and Animals: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 6-mark question split into 3 + 2 + 1 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Reproduction in Plants and Animals

The slips examiners see most often, and what to write instead.

• ✗Mistake: Calling budding in yeast binary fission

  In budding, the new individual begins as a small outgrowth; fission splits into two equal halves.

  ✓Do this: Fifty-fifty = fission; baby on the side = budding.

  Usually costs: 1 mark.

• ✗Mistake: Confusing pollination with fertilisation

  Pollination is transfer of pollen to the stigma; fertilisation is fusion of gametes inside the ovule.

  ✓Do this: Pollination comes first; fertilisation comes after the pollen tube reaches the ovule.

  Usually costs: 1-2 marks.

• ✗Mistake: Saying the ovary becomes the seed

  The ovule becomes the seed; the ovary becomes the fruit.

  Wrong working

  Ovary → seed, ovule → fruit

  Right working

  Ovule → seed, ovary → fruit

  ✓Do this: Small (ovule) to small (seed); container (ovary) to container (fruit).

  Usually costs: 1 mark.

• ✗Mistake: Giving features without examples

  Questions on pollinating agents usually carry a mark for an example.

  ✓Do this: Always add: sunflower (insect), maize (wind), Vallisneria (water).

  Usually costs: 1 mark per agent.

• ✗Mistake: Writing that fertilisation in humans happens in the uterus

  It takes place in the oviduct; the zygote then moves to the uterus.

  ✓Do this: Oviduct = meeting place; uterus = growing place.

  Usually costs: 1 mark.

Practice questions on Reproduction in Plants and Animals

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   The male part of a flower that produces pollen is the:
   (a) stigma
   (b) ovary
   (c) anther
   (d) sepal

   Hint

   Head of the stamen.

   Answer

   (c)

2. Q2 · 1 mark · Very short answerExam level

   Name the method of reproduction in Rhizopus.

   Hint

   Bread mould.

   Answer

   Spore formation.

3. Q3 · 2 marks · Short answerExam level

   Name two artificial methods of vegetative propagation, with one example each.

   Hint

   Cutting, layering, grafting.

   Answer

   Any two: cutting (rose, sugarcane); layering (jasmine); grafting (mango).

4. Q4 · 2 marks · Short answerExam level

   State the function of (i) corolla (ii) stigma.

   Hint

   Attract; receive.

   Answer

   (i) Petals attract insects for pollination. (ii) The stigma receives pollen grains.

5. Q5 · 1 mark · Assertion-reasonHarder exam level

   Assertion (A): Wind-pollinated flowers produce pollen in very large amounts.
   Reason (R): Most pollen carried by wind is wasted and never reaches a stigma.
   (a) (A) is true and (R) is false.
   (b) (A) is false and (R) is true.
   (c) Both (A) and (R) are true, and (R) is the correct explanation for (A).
   (d) Both (A) and (R) are true, but (R) is not the correct explanation for (A).

   Hint

   Wind is not aimed.

   Answer

   (c)

6. Q6 · 2 marks · Short answerHarder exam level

   Five Amoebae each undergo binary fission three times in a row (every daughter divides each time). How many Amoebae are there at the end?

   Hint

   Each doubles to 8.

   Answer

   Each gives 2 × 2 × 2 = 8; 5 × 8 = 40 Amoebae.

7. Q7 · 3 marks · Short answerHarder exam level

   Give three advantages of vegetative propagation.

   Hint

   Speed, sameness, seedless plants.

   Answer

   It is quicker than growing from seed; the new plants are identical to the parent, so good qualities are kept; plants that produce few or no seeds (banana, sugarcane, rose) can be grown.

8. Q8 · 1 mark · Very short answerHarder exam level

   Why are the testes placed outside the abdomen in the scrotum?

   Hint

   Temperature.

   Answer

   Sperms develop best at a temperature slightly lower than normal body temperature.

9. Q9 · 3 marks · Short answerHarder exam level

   Name the male and female gametes in humans, the organs that make them, and the cell formed when they fuse.

   Hint

   Sperm, egg, zygote.

   Answer

   Male gamete: sperm, made in the testes. Female gamete: egg (ovum), made in the ovaries. Fusion forms a zygote.

10. Q10 · 2 marks · Short answerHarder exam level

    What is artificial pollination and why do plant breeders use it?

    Hint

    Hand, brush, bag.

    Answer

    People transfer chosen pollen by hand (with a brush) onto the stigma of another plant and cover the flower with a bag. Breeders use it to combine good qualities of two plants into new, better varieties.

11. Q11 · 2 marks · Short answerHarder exam level

    Give two differences between binary fission and budding.

    Hint

    Equal or unequal; examples.

    Answer

    In binary fission the parent divides into two equal daughters, and the parent no longer exists; in budding a small outgrowth forms and separates, and the parent remains. Fission: Amoeba; budding: yeast, Hydra.

12. Q12 · 3 marks · Short answerHOTS / competency

    A bacterium divides every 30 minutes. Starting from one, how many divisions and how many hours are needed to reach 1024 bacteria?

    Hint

    2 to what power is 1024?

    Answer

    1024 = 2¹⁰, so 10 divisions; 10 × 30 = 300 minutes = 5 hours.

13. Q13 · 3 marks · Short answerHOTS / competency

    A student removes all the stamens from a bisexual flower before it opens and covers it with a paper bag. Will it produce fruit? Explain, and say what must be done to get seeds.

    Hint

    Self- and cross-pollination both blocked.

    Answer

    No fruit will form on its own: with no stamens there is no pollen for self-pollination, and the bag stops insects or wind bringing pollen from other flowers. To get seeds, pollen from another flower of the same kind must be dusted onto the stigma by hand (artificial pollination), then the bag replaced.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Two organisms that reproduce by binary fission?Show answer

   Amoeba and bacteria (also Paramecium).

2. 2.Name a plant that reproduces by leaf buds.Show answer

   Bryophyllum.

3. 3.What is a callus?Show answer

   A mass of unspecialised cells formed in tissue culture.

4. 4.Function of sepals?Show answer

   Protect the flower in the bud.

5. 5.Example of a water-pollinated plant?Show answer

   Vallisneria (or Hydrilla).

6. 6.What does the ovary become after fertilisation?Show answer

   The fruit.

7. 7.Where are sperms produced?Show answer

   In the testes.

8. 8.Where does fertilisation take place in humans?Show answer

   In the oviduct (fallopian tube).

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you give one example of each asexual method?
• ☐Can you list the steps of tissue culture?
• ☐Can you name the four whorls and their functions?
• ☐Can you give three features of insect-, wind- and water-pollinated flowers?
• ☐Can you draw the fertilisation flow chart?
• ☐Can you name the main human reproductive organs and their functions?

Reproduction in Plants and Animals: frequently asked questions