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Life Span: Period frm birth to natural death
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Life span not related to size (e.g. mango – short; peepal
– long)
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Reproduction significance: Continuity of species
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Factors on which mode of reproduction depends:
habitat, internal physiology
etc.
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Cell div mode of rep in unicellular org.
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In favourable condition –
Binary fission: In amoeba & paramecium (two equal
halves)
In Unfav conditions:
Encystation & Sporulation
(formation of minute Amoeba or Pseudopodiospores)
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Budding: yeast (2 unequal halves)
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In Fungi & Algae: Asexual rep through spores:
Types:
Zoospores – motile; zygospores – non motile
Conidia – in Penicillium; Gemmules – in Sponges
Fragmentation – Hydra
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Water Hyacinth (terror of Bengal), high rate of veg
propagation.
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Veg propagules: Potato: Buds (eyes), Banana & Ginger:
Rhizome;
Bryophyllum: Adventitious buds on leaf margins…… Key
feature: NODE
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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
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Sexual Rep: Elaborate, Complex & Slow.
Offspring not identical to parents
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Common pattern of sexual rep:
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.
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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
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Events: Pre-fertilization, Fertilization & Post fertilization
 |
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Gametogenesis: Male & Female, haploid, may be homogametes
(isogametes) or heterogametes.
Male: antherozoid or sperm; female: egg or ovum
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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
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Sexuality in animals:
Bisexual (Hermaphrodite): Earthworm, Sponges, tapeworm
& leech
Unisexual: Rest
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Gamete Formation: Haploid
Parents body may be
haploid: e.g. fungi, algae, Bryophytes. Produce gametes by
mitosis
Diploid: e.g. pteridophytes, Gymnosperms, Angiosperms and
all animals.
Produce gametes by Meiosis
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Site of meiosis in diploid organisms: Meiocytes (gamete
mother cells)
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Gamete Transfer: organisms where both male & female
gametes: fungi & Algae
To compensate for loss during transfer, male gametes
produced in large numbers.
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In bisexual flowers – self fertilization
In unisexual flowers – cross fertilization, so pollination
important.
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Fertilisation/ Syngamy:
Dev of new organisms without fertilization :
Parthenogenesis
Seen in Rotifers, Honeybees & some Lizards.
Site of Fertilization: Outside (External), Inside mother’s
body (Internal) fertilization.
Disadvantages of Ext Fertilization: Gametes can be
destroyed by predators.
Technique to avoid this – large number of gametes
released.
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Post Fertilization Events: Formed in medium (external
fert)/ In Mother’s body (Int Fert)
Types of development;
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  Embryogenesis: Zygote Cell Division & Cell
Differentiation Embryo
Parts of flower after fertilization:
Petals: wither & fall
Sepals: Wither and Fall (Exception- Brinjal, Tomato)
Pistil: Remains attached
Stamen: wither & Fall
Ovary: Fruit (Wall of fruit – Pericarp)
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And now some questions:
- Why unicellular organisms are considered immortal?
- Why progeny of asexual reproduction called Clones?
- What are vegetative Propagules?
- Characterize: Veg, rep & senescent phase in annual,
biennial & Perennials
- Differentiate: Seasonal & Continuous Breeders
