CLASS: X-SCIENCE-CHAPTER: HOW DO ORGANISMS REPRODUCE-NOTES

CLASS: X-SCIENCE

CHAPTER: HOW DO ORGANISMS REPRODUCE-NOTES

Asexual Reproduction in Plants

•   Spore formation → eg. Bacteria, fungi

•   Budding → eg. Fungi (yeast)

•   Fragmentation → eg. Algae, fungi

•   Vegetative propagation

(a)   Natural method

•   By roots → eg. Sweet potato

•   By stems → eg. Ginger, potato

•   By leaves → eg. Bryophyllum

(b)   Artificial method

•   Cutting → eg. Rose

•   Layering → eg. Strawberry, lemon

•   Grafting → eg. Mango, rose.

•   Micropropagation → eg. Orchids, dahlia

Sexual Reproduction in Plants

•   Flower is the reproductive organ.

•   It has four whorls – Calyx, Corolla, Androecium, Gynoecuim.

•   Calyx and corolla are accessory parts.

•   Androecium - Male reproductive organ producing pollen grains.

•   Gynoecium - Female reproductive organ having ovule (egg).

•   Pollination – Transfer of pollens from anther to stigma for fertilization.

•   Fertilization – Fusion of male and female gametes.

•   Double fertilization (Triple fusion and syngamy) – unique events in the embryo sac of ovules.

Asexual Reproduction in Animals

•   Fission

(a) Binary fission → eg. Amoeba

(b) Multiple fission → eg. Plasmodium

•   Budding → eg. Hydra

•   Regeneration → eg. Planaria, Hydra

Sexual Reproduction (Human)

•   Human being is heterosexual.

•   Reproductive system includes:

(a) Primary sex organs: Testes (males) and ovaries (females)

(b) Secondary sex organs: Genital ducts and glands (males) and fallopian tubes, uterus, vagina (females)

•   Male sex hormone is testosterone and female sex hormones are progesterone and estrogen.

•   Puberty is attained at the age of 13 – 14 years in males and 10 – 12 years in females.

•   The zygote formed after fertilization develops into embryo which gets implanted in uterus.

•   Placenta (a disc-like special tissue) develops between uterine wall and embryo for nourishment of the embryo.

•   Gestation period in humans is 280 days.

Reproductive Health

•   Birth control prevents unwanted pregnancies.

(a) Barrier methods

(b) Chemical methods

(c) Intrauterine contraceptive device

(d) Surgical method

•   Sexually transmitted diseases (STD) are caused by bacteria, protozoa and viruses.

•   AIDS is an incurable viral disease.