CHAPTER 1 & 2

Life Span
 Period from birth tothe natural death. Every organism lives only for certain period of time Eg Elephant 60 -90 years, Fruit fly 3-4 weeks, rose 5-7 years, rice 3-4 months.

Reproduction

Producing young-ones of their kind, generation after generation.

Types of reproduction:

 Asexual reproduction :single parent ,capable of producing identical offspring, no variations

Sexual: two parents, gametogenesis and fertilization, variations appear

Modes of asexual reproduction

Binary fission : Organisms considered immortal .Parent body divides into two halves, genetically identical to parent. Amoeba: It is simple or irregular.
Paramoecium : Transverse binary fission.
Multiple fission : parent body divides into many daughter organisms Plasmodium.
 Budding : daughter organisms grow from small buds arising in parent body. Exogenous budding: out side the body eg. Hydra, Yeast.

Endogenous budding : inside the body eg. Gemmule in sponge.Oidia of rhizopus
Conidia : non-motile, exogenous spores in chains eg. Fungi such as Pennicilium
Zoospores : microscopic motile structures eg. Algae -Chlamydomonas
In plants : term vegetative reproduction , units of vegetative propagation called vegetative propagules. Root, stem and Leaf .

Eg rhizome-ginger, tuber/eyes of potato,  offset-water hyacinth, bulbil-agave, leaf buds-bryophyllum.

Terror of Bengal- Water Hyacinth introduced due to beautiful flowers and shape of leaves
Juvenile phase/Vegetative phase : The phase of growth before reproductive maturity in animals/plant

Bamboo spp flowers once in 50-100 years

Strobilanthuskunthianasept-oct 2006 then sept-oct 2018

Oestrous cycle: Non primate mammal female, short duration, no bleeding

Menstrual Cycle: Primate female, duration more, bleeding occurs

Seasonal breeder- wild animals, breeding during optimum conditions

Continuous breeder-Human, domestic mammals can reproduce during through out the year

 The main events of sexual cycle are:

i. Pre-fertilisation events
a. Gametogenesis b. gamete transfer
The process of formation of male and female gametes by meiosis (cell-division) in diploid organism. In haploid its by mitosis.

Homogamete (Isogamete) : - gametes similar eg. Algae-cladophora
Heterogamete(an-isogamete) : - morphologically dissimilar gamete ,male gamete (antherozoid or sperm) ,female gamete (egg or ovum) eg. Human, fucus
 Sexuality in organisms : Bisexual term is used for Homothallic and Monoecious plants Both male and female reproductive structures in same plant eg. cucurbits and coconut.
Unisexual term used for Heterothallic and Dioecious plants Male and female reproductive-structure on different plants.eg. papaya and date-palm.
Flowering plants :male flower- staminate flower and female flower--pistillate flower 

Animals

 Bisexual term is used for Hermaphrodite animals -eg. Earth-worm, Tape-worm, Leech, Sponge.
Unisexual animals have male & female sexes in separate individuals -e.g. insects, frogs, humanbeings

Both earthworm and Tape worm are hermaphrodite/bisexual organism but in earth worm cross fertilization and in tape worm self fertilsation takes place.

Chara an algae-oogonium/nucule female rep part upper position and antheridium/globule lower position on same plant.

meiocyte or gamete mother cell..

Name of organism	Meiocyte (2n)	gamete (n)
Human	46	23
Housefly	12	6
Ophioglossum (fern)	1260	630
Potato	48	24

b) Gamete transfer :- to facilitate fusion.
Male gametes mostly motile and female non-motile,
Water is medium for gamete transfer- in lower plants. Large number of male gametes produced to compensate loss during transportation
Parthenogenesis :- development into new organism without fertilization of ovaeg. Rotifers, honey-bees, whiptail lizard, bird(turkey).
ii. Fertilization

External fertilisation :- outside the body of organism in external- medium (water) eg. majority of algae, fishes, amphibians.
 Advantage :- show great synchrony between the sexes

1. Release of large number of gametes into surrounding medium

2. Large number of offsprings produced.

Disadvantage :- offspring vulnerable to predators, natural disasters.
 Internal fertilisation :- fusion occurs inside female body eg. majority of plants and animals. Egg non-motile and formed inside female body. Male gamete motile, produced in large numbers to reach egg and fuse with it. In seed plants, non- motile male gamete carried to female gamete by pollen-tube.

Oviparous :animals lay eggs outside the female body.Eggs can be fertilized/ unfertilized. Fertilized eggs covered with hard calcareous shell, laid in safe place in the environment. Unfertilised eggs laid in water. Example- fishes, frogs, reptiles, birds
Viviparous: animals bear and rear the embryo inside female body, give birth to young-ones. Advantage- proper embryonic care, protection, survival chances of young-ones greater. Examplecows, whales, human beings .
Embryogenesis :- development of embryo from zygote by cell division (mitosis) and cell differentiation.

In flowering plants :- zygote formed inside ovule

Sepal	Fall off
Petal	Fall off
Stamen	Fall off
Zygote(2n)	Embryo
Primary endosperm nucleus	Endosperm (3 N)
Synergid(n)	Disintegrate
Antipodals(n)	Disintegrate
Ovary	Fruit
Ovule	Seed
Ovary wall	Pericarp (epicarp + mesocarp + endocarp)
Integument	Seed coat (testa + tegmen)

 Parthenocarpy :ovary without fertilisation develops into fruit.
Clone : A group of individuals of the same species that are morphologically and genetically similar to each other & their parents and are produced by single parent &asex reproduction

PARTS OF A FLOWER

Four whorls -calyx (sepals), corolla (petals), androecium (Male reproductive organ-unit stamen), gynoecium (Female reproductive organs-carpel)

Male Reproductive Organ

Androecium consists of Stamens- filament and anther
Atherbilobed and dithecous- 4 Microsporangiate.

MICROSPOROGENESIS:

The process of formation of micro spores from pollen mother cell through meiosis is called microsprogenesis. Structure of Microsporangia: wall layers- Epidermis, endothecium, middle layers and Tapetum , in the centresporogenous tissue Tapetum :Inner most layer of wall of microsporangium .Cells have dense cytoplasm. Generally have more thanone nucleus .Nourishes the developing pollen grain.

Microspore mother cell (2n)/PMC/Meiocyte undergo Meiosis  ? Microspore tetrad (n)› Microspore (n) ? Pollen grains (n)

Pollen grains:
i) Exine ii) Intine

Exine is mass of sporopollenin..(Hardest natural substance).Due to this pollen has no effect of high temp, enzyme, acids and alkali. Found as fossils

Intine is made of cellulose and pectin.
Mature pollen grains have two cells -large vegetative cell& small generative cell.
Generative cell forms two male gametes by mitotic division.
Pollen allergies- asthma, bronchitis- egparthenium or carrot grass

Pollen tablets used to increase the performance of athletes and race horses.

Pollen are preserved at -196 temp

Gynoecium / carpel (the female reproductive organ)
 anatropous ovule)Megasporangium

 Each Carpel consists of ovary ,style& stigma.
 Ovules are attached to ovary by placenta.
Funicleis stalk of ovule .
Hilum, a region where funicie is attached to the body of ovule
Micropyle a pore for entry of pollen tube & to imbibewater.

Megasporogenesis
	Megaspore mother cell (2n) of nucellus region at micropylar end Meiosis
	?
	4 Megaspores (n) (3 megaspores degenerate, 1 remains functional)
	?
	Funtional Megaspore (n) (Divides 3times by mitosis)
	?
	8 Nucleated 07 celled Embryo Sac/female gametophyte formed
	?	?	?
	2 polar nuclei at center(n each )	3 cells at chalazal end called antipodals(n)	3 cells group at micropylar end -the egg cell(n) & 2 synergids(n)

Yucca-Moth : The moth deposits its eggs in the locule of the ovary and flower in turn get pollinated by the moth.

Insect pollination: Pollen grains and nectar are the rewards. These flowers are large, colorful, fragrant.

Wind Pollinated flowers- pollen grains light and non sticky, well exposed stamens, large feathery stigma,  single ovule in ovary, flowers packed into inflorescence

In water hyacinth and water lilly pollination is by insects/wind.

Water pollination:

Either female flower reach at the surface of water by long stalk and pollen are released on water surface egVallisneria

Or as in Sea grasses female flower remains submerged in water and ribbon like pollen with mucilage coating reaches to stigma inside the water.

Cleistogamous flowers of viola, commeliana, oxalis do not open at all and don’t require pollinators, continuous self pollination leads to inbreeding depression.

Pollen grains geminate on stigma & pollen tube grows through style.

 Pollen tube reaches micropyle& releases two male gametes into embryo-sac .

Filliform apparatus guides the entry of pollen tube.

Double fertilization=Syngamy+Triple fusion

Syngamy :Fusion of one male gamete(n) with egg (n)Zygote(2n)Produced First

Triple Fusion Fusion of two Polar Nuclei(n+n=2n) and secondMale Gamete(n).

product PEN(3n)-Endosperm

Stages of embryo development after fertilization:

1.    Zygote divides by mitosis into suspensor & embryo cells
2. Suspensor cell forms a globular basal cell which remainsembedded in the endosperm & a multicellular suspensor bearing the embryo
3.Globular embryo becomes heart-shaped & then mature embryo with radicle, plumule&Cotyledons

The portion of embryonal axis above the level of cotyledons= Epicotyl , it terminates with plumule.

The single cotyledon of grass family is called-Scutellum

True Fruit develops only from the ovary, e.g. mango, tomato
False Fruit develops from parts of the flower other than the ovary e.g. apple, strawberry, peach

Seeds two types:

i)              Albuminous/ (with Endosperm)-wheat, maize, castor

ii)            Non albuminous(without Endosperm)-endosperm consumed during embryo development eg. Pea, ground nut

Coconut water- Free nuclear endosperm, white kernel of coconut-Cellular endosperm

Perisperm: residual persistent nucellus in seeds of black pepper and beet

Special mechanism of reproduction:-

I)             Apomixis- Production of seeds without fertilisation e.g. Mango, citrus

Methods:

a)    Diploid egg cell is formed without reduction division and develops into embry without fertilization

b)    Some of the nucellar cells protrude into embryo sac and develop into embryo.

Apomictic seeds are better than hybrids as these are less expensive and their will be no segregation of characters in the progeny.
ii) Polyembryony- Occurrence of more than one embryo in aseed e.g.Orange.

Outbreeding devices:

Continued self-pollination result in inbreeding depression. Flowering plants have developed many devices to discourage self-pollination & encourage cross-pollination.

1.    Bearing unisexual flowers Unisexuality 

2.    Anther & stigma mature at different times Dichogamy 

3.    Anther & stigma placed at different positions Heterostyly 

4.    Pollen grains of a flower do not germinate on the stigma of the same flower Self incompatibility it is genetical mechanism.

Artificial Hybridisation: cross-pollination performed by man for crop improvement.
i) Emasculation i.e. removal of anthers from the flower bud of a bisexual flower before the anther dehisces using a pair of forceps
ii) Bagging i.e. covering the emasculated flowers with a bag of suitable size to protect them fromcontamination with unwanted pollen

Pollen -pistil Interaction:
i) All the events from pollen deposition on the stigma until the entry of the pollen
tube into the ovule are together called pollen-pistil interaction.
ii) It is a dynamic process involving pollen recognition by stigma/pistil through chemical means for compatible pollen by accepting them and if incompatible rejecting them.

iii)           Accepted pollen are allowed to germinated and their pollen tubes are guided towards egg apparatus.