REPRODUCTION IN PLANTS
Sexual rep: fusion of 2 nuclei of reproductive/ sex cells (gametes)to form a zygote (genetically dissimilar offspring)
Asexual rep: no fusion of 2 reproductive cells, by means of budding, spore formation, vegetative rep, binary fission

Mitosis: cell division in body/ vegetative cells, 2 identical daughter cells produced, same # of chromosomes as parent cell, growth results, ensures daughter cell have same chromosome # like parental cells (diploid condition maitained)

Meiosis/ reduction division: cell division in reproductive organs at time of formation of sex cells/ gametes, 4 daughter cells produced, reduced chromosome # (diploid > haploid), gametes (sperm, ova)= haploid, n =23, when gametes fuse: ensures zygote w/ diploid chromosome # > maintain genetic stability (genetically dissimilar offspring)

Man: 46 chromosomes (2n, n = 23)

Natural vegetative reproduction in flowering plants
Vegetative rep or propagation: separation of some part of parent plant which can develop into a new complete plant > several plants from 1 parent plant, occurs by means of underground storage organs (rhizomes, bulbs, corms, tubers)
Food stored underground: enables survival in unfavourable conditions, favourable > food used > rapid development of buds > new plants, perennation: survival of plants from year to year, underground storage organs = perennating organs

Artificial vegetative propagation
Marcotting:
A ring cut though bark of branch (remove phloem, not xylem) > earth rich in manure applied round ringed area of branch, held in place by coconut husks (food subs accumulate above band) > roots appear from band, strong enough > branch cut off > rooted branch planted

Cutting: cutting made by cutting off a shoot from plant (just below node, leaves near bottom should be removed) > leave cutting in jar of water / moist soil > roots grow from end of stem and from where leaves removed

Grafting: stem (scion-not suitable to grow in soil) inserted into rootstock (suitable to grow), bound tightly > scion grows

Natural vegetative propagation
Runners: parent plant grows long stems = runners/ stolons which have a bud at each node, buds grow shoots & roots (new plant), new plants obtain food from parent plant through runner until grow own roots > runner withers > dies away
Bulbs: bulb = underground bud, stem v short and never grows above ground, leaves- thick fleshy as contain stored food, bulbs- white > underground no photosynthesis
Main shoot and side shoots grow above ground, turn green, photosynthesis > food from photosynthesising shoots used to produce a daughter bulb at base of side shoot
Bulb = modified shoot (presence of 1reduced stem, 2fleshy scale leave, 3terminal & lateral buds)
Rhizomes- horizontal stems (underground) that arise from lateral buds
Rhizome = modified stem (presence of 1(inter)nodes, 2buds, 3scale leaves)
Corm- leave which are above ground photosynthesise, food stored in stem of corm > enables growth of lateral buds which emerge into new corms (contractile roots pull old and new corm inside ground: prevent new corm from being exposed on ground dry up)
Potato = stem tuber (presence of 1buds-eyes, 2scars left by scale leaves-eye brows, 3terminal buds)

Advantages of Artificial propagation
-plants w/ desired qualities can be grown
-fruits and flowers can be obtained more than once within a short period

Advantages of Asexual rep
-new plants exactly resemble parents (good qualities retained)
-mature faster as food subs largely available
-dont depend of processes (pollination, fertilization, dispersal of fruits and seeds)
-new plants obtain food from parent plants despite unfavourable conditions
-dont result in indiscriminate and widespread distribution of new plants (> wastage of large # of offspring)

Disadvantages of Asexual rep
-retain undesirable qualities of parent plants
-no variations > not adapted to conditions
-develop much faster > overcrowding & competition
-strength and vigour of succeeding generations gradually reduces

Advantages of Sexual rep
-combine characteristics > more adapted for survival , increases vigour , variations
-only fittest survive > major evolutionary changes

Disadvantages of Sexual rep
-necessary for 2 gametes to fused together
-may produce individuals w/ undesired qualities

A Flower
Reproductive part of a plant meant for propagation of species
Has 4 whorls; calyx, corolla, Androecium, Gynoecium (has all whorls- complete flower, < 4-incomplete, papaya)
Calyx and coralla- non-essential, Androceium & Gynoecium- essential whorls
Flowers: bisexual (have (fe)male organs) or unisexual (male/female sex organs-papaya)
Calyx- made of green sepals that protect flower while in bud stage & for photosynthesis
Corolla- made of petals (colour due to pigment anthocyanins), attracts insects for cross-pollination
Androecium- male part of flower, consists of stamens (each w/ anther lobe (consists of pollen grains which produce male gametes) and stalk/filament)
Gynoecium- female part of flower, consists of many pistils (each w/ stigma, style, ovary and ovules), stigma receives pg during pollination while ovary consists of ovules which produce the female gametes

Pollination: transfer of pg from the anther to the stigma
self-pollination: ...to stigma of same flower (bisexual flower)
cross-pollination: ...to stigma of a diff flower on same plant or to a flower of another plant of the same species
Agents of pollination: animals (insects), water, air

Advantage of self-pollination
-almost certain to occur
Disadvantage of self-pollination
-continued self-pollination > weakened individuals
Advantages of cross-pollination
Healthier offspring, seeds more abundant and viable, individuals better adapted, new varieties created,
Disadvantage of cross-pollination
-relies on external agents, by wind- large amt of pg wasted

Features promoting self-pollination
Homogamy: ripening of anthers and stigma at same time
Cleistogamy: bisexual flowers that dont open at all, closed flowers

Features promoting cross-pollination
Dichogamy: ripening of anthers and stigma at diff times (protandry-male 1st: anthers, protogyny-female 1st: stigma)
Unisexuality: self-pollination is not possible
Self-sterility: pg sterile to ovules of same flower
Heterostyly: placement of sex organs at diff heights

Fertilisation
Pollen grains land on stigma > stigma secrete sugary fluid (sucrose) > pg germinate, absorbed fluid > vol of cytoplasm ^ > burst > cytoplasm flows out to form pollen tube
(many pg germinate > form pollen tube, only 1 reaches micropyle, sugary fluid can't support all)
tip of pollen tube secretes enzymes (digest style) > tube grows through style (vegetative nucleus followed by generative nucleus) > reach micropyle > generative nucleus divide into 2 male gametes > tip of pollen grain breaks down and disappears > gametes enter embryo sac > 1 gamete fuses w/ egg nucleus to form diploid zygote = fertilisation, if the 2nd male gamete fuses w/ the secondary nuclei = double fertilisation

After fertilisation
Zygote > embyo > plumule, radicle, 1/2 cotyledons (may or may not store food)
Primary endosperm nucleus > endosperm (may or may not persist as a food store)
Nucellus > disappears
Integuments > outer > testa, inner > tegmen
Ovary wall > pericarp
Petals, stames, sepals > wither, dry up, die (some plants sepals remain)
Fruit = fertilised ovary
Seed = fertilised ovule (zygote, primary endosperm nucleus, nucellus, integuments, ovary wall)

After fertilisation: ovary > fruit, ovules > seeds
A mature seed is covered by hard leathery testa which encloses tegmen (membranous layer), tegmen + testa = seed coat
Embryo consists of 1/2 cotyledon (monocot/ dicot), which may or may not store food
seeds store food subs in cotyledons which are massive- non-endospermic seeds, beans
seeds store food sub in endosperm which is quite massive, cotyledons-small & rudimentary- endospermic seeds, maize, rice, wheat

STRUCTURE OF A SEED
testa: protects seeds from damage by fungi, bact and insect, mechanical injuries, retains moisture
hilum: scar which marks pt of attachment to ovary wall
micropyle: small hole through which water enters and gaseous exchange takes place
plumule: embryonic shoot, consists of cotyledons and embryonic leaves, cotyledons store food subs to supply energy for early stages of germination
radicle: embryonic root, fixes plant into soil and absorbs water (to a certain extent)
cotyledons/endosperm: food storage tissue

Importance of water in the seedling
for seed: soften testa & activate enzymes
-Activate enzymes, help conversion of stored starch > sugar & protein > amino acids, transport sugar in solution from cotyledons to growing regions, expand vacuoles of new cells: root & shoot grow + leaves > expand, maintain turgor of cells: shoot upright & leaves expands, provide water for photosynthesis, transport salts from soil to shoot

Importance of oxygen
Most testas impermeable to O₂, softened > splits > O₂ enters > aerobic resp > large amt of energy > new cells > growth

Importance if temp
^ temp > ^ speed of chemical reactions > germination faster , also optimum temp for enzyme activity > energy

dormancy: state of seed - does not germinate despite favourable external conditions, controlled by internal mechanism

Importance of dispersal
-ensures variability and colonisation of new habitats
-reduces chances of inbreeding
-prevents overcrowding and competition for space, light, water and minerals
-reduces vulnerability to epidemic diseases

Vegetative rep	Sexual rep
No new varieties	New varieties arise that may be better than parent
Offspring can obtain food from parent	Food reserves limited to cotyledons and endosperm
New plants produced in conditions suitable for parent	Conditions may no be favourable for germination of seeds
Lack of dispersal mechanism > overcrowding	Dispersal methods allow colonisation of other areas

Insect-pollinated flowers	Wind-pollinated flowers
Large, bright scented flowers w/ nectar (insects respond to colour and scent > attracted to flower > collect/ eat nectar from nectaries or pg from anthers)	Dull, scentless and nectarless flowers
Mostly in bisexual flowers	Takes place in unisexual flowers
Stigmas often small and is deep in corolla, sticky to catch pg	Stigma long, feathery (^ SA), protrudes above petals
Stamens may be within corolla tube	Stamens long, protrude above petals (large anther lobe)(wind more likely to dislodge pg)
Less pollen produced	Large amt of pollen produced (large amt wasted)
Pollen large, heavy an sticky	Pollen small, light and smooth- easily carried by wind

Seedlings grown in dark	Seedlings grown in sunlight
leaves and stem yellowish, chlorophyll absent	leaves and stem green, chlorophyll present
leaves small and folded out	leaves larger and widely spread
internodes long and slender	internodes short and thick
etiolatednot	etiolated
veins not prominent	veins prominent

Sexual reproduction in animals
Genetics
Cell Strcuture and Organisation
Enzymes
Animal and Plant Nutrition
Transport in Plants and Transpiration
Support, Movement and Locomotion
Transport in Man
Respiration
Excretion
Homeostasis
The Eye
Nervous System
Chemical Control of Plant Growth
The Use and Abuse of Drugs
Diversity of Organisms
Nutrient cycles and Ecology
Parasitism
The Human Impact on the Environment

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