CBSE · Class 10 · Biology · Chapter 7

How do Organisms Reproduce? — Formula Sheet

Board Formulas

8 formulas

1.Reproduction Types★
$Reproduction = Asexual (1 parent, clones) + Sexual (2 parents, variation)$
Asexual is fast but genetically identical; sexual creates variation, useful for evolution.
2.Fission
$Parent cell ⟶ 2 (binary) or many (multiple)$
Binary: Amoeba, Paramecium. Multiple: Plasmodium. Simple asexual mode in unicellular organisms.
3.Budding
$Parent ⟶ parent + bud \to new individual$
Yeast, Hydra. Bud grows on the parent and detaches when mature.
4.Vegetative Propagation★
$Root/Stem/Leaf ⟶ new plant$
Potato (stem tuber), Bryophyllum (leaf buds), rose (stem cutting), ginger (rhizome). Widely used in agriculture.
5.Sexual Reproduction Steps
$Gametogenesis \to Fertilisation \to Zygote \to Embryo \to Development$
Fusion of male and female gametes (n + n → 2n). Zygote is the starting point of a new individual.
6.Pollination and Fertilisation in Flower
$Pollen \to stigma \to pollen tube through style \to ovary \to fusion with egg$
Pollen tube delivers 2 male gametes to the ovule (double fertilisation in angiosperms) — one fuses with the egg, the other with polar nuclei.
7.Menstrual Cycle Length
$Cycle \approx 28 days; ovulation on day \approx 14$
Menstruation (day 1-5), follicular (5-14), ovulation (~14), luteal (14-28). Regulated by FSH, LH, oestrogen, progesterone.
8.Human Chromosome Count in Gametes★
$Gamete: n = 23; Zygote: 2 n = 46$
Meiosis halves the chromosome number in gametes; fertilisation restores the diploid count.