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Asexual Reproduction Asexual reproduction is natural “cloning.” Parts of the plant, such as leaves or stems, produce roots and become an independent plant. Sexual Reproduction Sexual reproduction produces a greater chance of variation within a species than asexual reproduction would. This variation improves the chances that a species will adapt to his environment and survive. Sex! Asexual Reproduction involves only 1 parent offspring genetically identical to parent involves regular body cells its quick Sexual Reproduction involves 2 parents offspring genetic mix of both parents involves specialized sex cells its slow Which is Better? It depends! Asexual Reproduction advantages Sexual Reproduction advantages does not require special lots of variation within a cells or a lot of energy can produce offspring quickly in a stable environment creates large, thriving population species able to live in a variety of environmental settings able to adapt to changes in the environment disadvantages limited ability to adapt face massive die-off if environment changes disadvantages needs time & energy produce small populations Terms to know: Haploid: having a single set of chromosomes in each cell. Diploid: having two sets of chromosomes in each cell. Mitosis: cell division, which produces two genetically identical cells. Meiosis: reduction division, which produces four haploid reproductive cells. Flowers Flower Parts PARTS of the flower include: Sepals: enclose the flower bud and protect it until it opens Petals: attract pollinators Insect-pollinated flower Floral structures Diagram of an insect-pollinated flower Petal Stigma Anther Filament Style Ovary Ovule Nectar Sepal Wind-pollinated flower Diagram of a wind-pollinated flower Bract Anther Filament Ovary Stigma Functions of parts of the flower sepals petals Protects the flower during the bud stage Attracts insect pollinators by colour and Anthers scent produce and release pollen grains filament positions the anther for effective pickup Stigma style ovaries of pollen by the pollinating agent collects the pollen from the pollinating agent positions the stigma for pollen collection site of fertilisation, protects the developing seeds, aids in seed dispersal Pollination The transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma). Agents of pollination . . . the means that moves the pollen grains from the anther to the stigma. Agents of pollination include: wind; insects; birds; water & rodents. Photomicrograph of pollen grains: Note the spikes that attach pollen grains to insect’s body. structural adaptations of insect-pollinated and wind-pollinated flowers Insect-pollinated flowers Petals large & brightly coloured to attract insects Stigma located inside the flower where the insects have to brush past it Anthers inside the flower where the insects have to brush past them Stigma usually small & sticky so that pollen grains can attach from insect body Flower often strongly scented Large sticky or spiky pollen grains which stick to insects Wind-pollinated flowers Petals small or absent, if present, not brightly coloured Stigma exposed to catch pollen grains blowing in the wind Anthers exposed outside the flower so that wind can easily blow the pollen grains away Stigma large & feathery to catch pollen grains blowing in the wind Flowers have no scent Light & smooth pollen that can be blown in the wind What happens after pollination? pollen grains germinates forming pollen tube the pollen tube grows down style digesting the style tissue The pollen tube enters ovule through micropyle male nucleus moves into ovule male nucleus (male gamete) fuses with the ovum or egg cell (female gamete) i.e. fertilisation occurs ovule becomes seed ovule wall becomes seed coat or testa ovary becomes fruit stigma and the style withers and dry up Pollen is produced in the male organs of the flowers - anthers. Pollination occurs when pollen is transferred from the anthers to the female organs by wind or by animals. If the female stigma is receptive to a pollen grain, the pollen produces a pollen tube, which grows through the female tissue to the egg, where fertilization takes place by the sperm nucleus. Sexual Reproduction in Flowering Plants (Angiosperm) External structure of a Seed Internal structure of a Seed plumule radicle micropyle cotyledon testa (seed coat) Testa; protects the embryo from physical damage & attack from pathogens Micropyle; a hole in the testa that allow water & oxygen to enter into the seed Cotyledons; stores nutrients (starch, protein & lipids) required during germination Plumule; grows into shoot after germination Radicle; grows into root after germination Conditions for seed germination Seed germination is the process in which a plant emerges from a seed & begins grow Conditions needed for seeds germination are: Suitable temperature; for enzymes to work effectively Oxygen; for aerobic respiration to provide energy to growing embryo Water; for chemical reactions to occur in solution, dissolve nutrients for transportation, activate enzymes & soak testa