REPRODUCTION IN ORGANISMS: Key Points

Life Span: Period frm birth to natural death

Life span not related to size (e.g. mango – short; peepal – long)

Reproduction significance: Continuity of species

Factors on which mode of reproduction depends:  habitat, internal physiology etc.

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)

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

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.

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 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

Site of meiosis in diploid organisms: Meiocytes (gamete mother cells)

Gamete Transfer: organisms where both male & female gametes: fungi & Algae To compensate for loss during transfer, male gametes produced in large numbers.

In bisexual flowers – self fertilization In unisexual flowers – cross fertilization, so pollination important.

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.

Post Fertilization Events: Formed in medium (external fert)/ In Mother’s body (Int Fert) Types of development; Undergoes period of rest- fungi & Algae  (develops thick wall to protect from desiccation and damage) Undergoes Meiosis – Haplontic life cycle – forms haploid spores Forms embryo

Embryogenesis: Zygote                  Cell Division & Cell Differentiation                                                         Embryo Oviparous vs Viviparous 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)

And now some questions:

1. Why unicellular organisms are considered immortal?
2. Why progeny of asexual reproduction called Clones?
3. What are vegetative Propagules?
4. Characterize: Veg, rep & senescent phase in annual, biennial & Perennials
5. Differentiate: Seasonal & Continuous Breeders

Key Points: Evolution (Big Bang & Origin) Part 1

XII	EVOLUTION
QUESTIONS	NOTES
	Age of universe: 20 bn yrs ago Age of Earth: 4.5 bn yrs ago Life appeared: 4 bn yrs ago
	Universe m/o clusters of galaxy. Galaxy m/o clusters of stars, clouds of gases & dust. BIG BANG THEORY: explains origin of universe.
	Composition of Earth: Water vapour, methane, CO2, NH3 (frm molten mass on Earth’s surface) No atmosphere
	Processes on Earth post big bang led to formation of CO2, water etc.
	Theories of Origin of Life: ·       Panspermia: Life came from outer space as ‘spores’ ·       Spontaneous generation: Life originated from decaying matter ·       Life comes from pre-existing life – Louis Pasteur ·       Abiological Origin of life: Oparin & Haldane ·       Exp demo of above: Miller
Define Biogenesis	Biogenesis/ Chemical Evolution: Inorganic molecules            Non-living organic molecules s/a proteins, RNA etc.                                                   Life Conditions required: High temp, Volcanic storms, reducing atmosphere containing CH4, NH3 etc
	Miller’s exp: Flask with: CH4, NH3, H2 (red. Atm)                      Water vapour                      Electric Spark (high temp – 800°C) Result: Amino acids formed Further Proof: ·       Others obtained sugars, pigments, fats, N bases in similar exp ·       Meteorite content reveals similar material from other places in space

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

Why DNA is preferred Genetic Material

Genetic material should be capable of:

1. Stability: storing genetic information, chemical & Structural stability
2. Expression: able to express in from of traits or 'Mendelian Characters'
3. Replication: Be able to duplicate genetic material accurately
4. Inheritance: pass on copies of genetic information to next generation 
5. Evolution: allow production of variations through mutation or recombination

DNA vs RNA as genetic material

Both DNA and RNA have ability to act as genetic material but RNA preferred because:

1. DNA has Deoxyribose while RNA has Ribose - Chemical stability
2. Thymine in DNA while Uracil In RNA - Chemical stability

Chemically less reactive

➤Stability proved by Transformation (Griffith's experiment)

1. DNA double stranded, RNA single stranded - structural stability
   
2. Ability to replicate: complementary base pairing in dsDNA allows accurate copying during semiconservative replication 

Both DNA & RNA can express themselves through proteins. In fact protein synthesis cannot occur without RNA.

Ability to undergo mutation: both DNA & RNA able to mutate. In fact RNA mutates faster than DNA.

RNA being more reactive, and DNA being more stable; DNA was preferred over RNA as genetic material.

Now having read the topic try answering these questions:

1. Why is RNA more suitable in a catalytic role?
2. It is difficult to develop vaccines against RNA viruses s/a Rhinovirus (common cold Virus) or HIV?  
3. Justify, RNA is better suited for transmission of genetic information.