Key Points: Chapter 1 Reproduction In Organisms

XII	Chapter 1:  Reproduction In Organisms
QUESTIONS	NOTES
	Life Span: Period frm birth to natural death
Why unicellular org immortal?	Life span not related to size (e.g. mango – short; peepal – long)
	Reproduction significance: Continuity of species
Sexual vs asexual rep	Factors on which mode of reproduction depends: habitat, internal physiology etc.
Y asexual rep progeny k/a clones?	Cell div mode of rep in unicellular org.
	In favourable condition - Binary fission: In amoeba & paramecium (two equal halves) In Unfav conditions: Encystation & Sporulation (formation of minute Amoeba or Pseudopodiospores)
	Budding: yeast (2 unequal halves)
Asexual vs vegetative What are veg. Propagules?	In Fungi & Algae: Asexual rep through spores: Types: Zoospores – motile; zygospores – non motile Conidia – in Penicillium; Gemmules – in Sponges Fragmentation – Hydra
	Water Hyacinth (terror of Bengal), high rate of veg propagation.
	Veg propagules: Potato: Buds (eyes), Banana & Ginger: Rhizome;  Bryophyllum: Adventitious buds on leaf margins…… Key feature: NODE
	In simple org: asexual rep in fav conditions; sexual in unfav (provides variations, enables protection by hard seed coat) In higher org: sexual rep common, asex rare. In animals only sexual
	Sexual Rep: Elaborate, Complex & Slow. Offspring not identical to parents
Veg, rep & senescent phase in annual, biennial & Perennials	Common pattern of sexual rep: Complete juvenile/vegetative (in plants) phase Beginning of rep phase (flowering in plants) senescent phase Length of the 3 phases variable in different organisms Hormones responsible for transition between 3 phases. Unique: Bamboo perennial but flowering once in lifetime Strobilanthus kunthiana once in 12 yrs.
Seasonal Breeders vs Continuous breeders.	Animals: e.g. birds seasonal breeders in nature (in captivity; exploited) Placental Mammals: Cyclical changes in ovaries & Hormones Non primate mammals: Oestrous Cycle Primate mammals: Menstrual cycle
Events: Pre-fertilization, Fertilization & Post fertilization
	Gametogenesis: Male & Female, haploid, may be homogametes (isogametes) or heterogametes. Male: antherozoid or sperm; female: egg or ovum
	Sexuality in plants: Unisexual/Dioecious/Heterothallic e.g. papaya, date palm OR Bisexual/Monoecious/Homothallic Male: staminate; Female: Pistillate If make and female flower on different plants: dioecious If male & female flower on same plant: Monoecious
	Sexuality in animals: Bisexual (Hermaphrodite): Earthworm, Sponges, tapeworm & leech Unisexual: Rest
	Gamete Formation: Haploid