Asexual reproduction
- Parents
- One parent
- Cell division
- Mitosis
- Offspring
- Genetically identical copies (clones)
- Examples
- Budding in yeast and hydra, mould spores, potato, Bryophyllum, cuttings
- Strength
- Fast; builds numbers quickly when conditions suit
Class 9 BiologyChapter 11NCERT Exploration, Grade 9
Reproduction: How Life Continues
A mango tree dies, its seeds do not. How every kind of life makes more of itself.
- 5 topic pages
- 26 interactives
- 30 quick checks
- 29 flashcards
- 18 practice questions
Think it over
- A potato left in a dark cupboard sprouts with no seed in sight. What does that tell you about where new plants can come from?
- Two puppies from the same litter rarely look exactly alike. Why not, when they share both parents?
- You are not a copy of either parent. Where exactly does the mixing happen?
How life continues
Watch any living thing for long enough and the same story plays out: birth, growth, maturity, reproduction and, at the end, death. What lives on is the next generation. The seeds of an old mango tree become young trees; a calf, a kitten or a child carries its parents' kind forward. Making new individuals of your own kind is reproduction, and it is how life on Earth carries on.
There are two broad ways to do it. In one, a single parent makes near exact copies. In the other, the young inherit genetic material from two parents, so each one is a fresh mix. Over many generations those small differences help living things cope with a changing world, and can even give rise to new species.
Two ways to make more life
Sexual reproduction
- Parents
- Two parents
- Cell division
- Meiosis makes gametes, then fertilisation
- Offspring
- A new mix of both parents (variation)
- Examples
- Flowering plants, frogs, birds, humans
- Strength
- Variation helps a species adapt and survive change
The chapter, section by section
- NCERT 11.1 and 11.1.1
Asexual reproduction: one parent, exact copies
- One parent, no partner, and young that match it gene for gene: that is asexual reproduction. Bacteria, amoeba, yeast, hydra, sponges and many plants do it.
- Vegetative propagation: new plants from growing parts such as stems and leaves (potato, ginger, sugarcane, money plant, Bryophyllum).
- NCERT 11.2 and 11.2.1
Sexual reproduction and variation
- Sexual reproduction: the young get a share of genetic material from each of two parents.
- Full-set gametes would double the chromosome number every generation. Meiosis prevents that by halving it: 46 in human body cells, 23 in gametes.
- NCERT 11.2.2 to 11.2.5
Sexual reproduction in flowering plants
- Flowering plants (angiosperms) are the most diverse plants on Earth; the flower is their reproductive organ.
- A complete flower has sepals, petals, stamens (male: filament and anther with pollen) and a pistil (female: stigma, style, ovary with ovules).
- NCERT 11.3 and 11.4
Sexual reproduction in animals
- Animals reproduce asexually (budding in hydra) and/or sexually. Sexual reproduction must get the gametes together and keep the young alive.
- External fertilisation: frogs and most fish, in water. Many eggs, many lost, low survival.
- NCERT 11.5.1 to 11.5.10
Reproduction in human beings
- At puberty the reproductive organs mature and begin to make gametes: sperm in males, eggs in females.
- Male: testes (in the scrotum) make sperm and a hormone; sperm pass through the vas deferens to the urethra; seminal vesicles and prostate add fluids.
The chapter at a glance
- Reproduction keeps each kind of living thing going and hands genetic information on to the next generation.
- Asexual reproduction: one parent, mitosis, identical offspring. Examples: budding, spore formation, vegetative propagation.
- Cutting, grafting, layering and tissue culture let farmers grow many identical plants.
- Sexual reproduction: two parents; meiosis halves the chromosomes in gametes (46 to 23 in humans), and random mixing creates variation.
- Flowers carry male stamens and a female pistil inside rings of sepals and petals; pollen reaches the stigma by self- or cross-pollination.
- A pollen tube takes the male gamete to the egg in the ovule; the zygote grows into an embryo, seeds come from ovules and fruit from the ovary.
- Frogs and most fish fertilise externally and lay many eggs; reptiles, birds and mammals fertilise internally.
- In humans the testes make sperm and the ovaries make eggs; ovulation is around day 14 of a typical 28-day menstrual cycle.
- If fertilisation happens, the zygote implants and pregnancy lasts about nine months; the mother needs good food, check-ups and rest.
- Condoms, pills and IUDs such as the Copper-T are birth control methods; condoms also help prevent STIs.