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ALTERNATION OF GENERATIONS. 1.Alternation of generations: haploid (n) stage that produces gametes followed by diploid (2n) stage producing spores. 2.Haploid:

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Presentation on theme: "ALTERNATION OF GENERATIONS. 1.Alternation of generations: haploid (n) stage that produces gametes followed by diploid (2n) stage producing spores. 2.Haploid:"— Presentation transcript:

1 ALTERNATION OF GENERATIONS

2 1.Alternation of generations: haploid (n) stage that produces gametes followed by diploid (2n) stage producing spores. 2.Haploid: gametes; half the number of chromosomes in somatic cell, indicated by n, result of meiosis. 3.Diploid: somatic cells; double number of chromosomes in gametes, indicated by 2n; result of fertilisation.

3 1.Gametophyte: generation producing gametes in gametangium/ gametangia sexual stage. 2.Sporophyte: generation producing spores in sporangium/ sporangia – asexual stage. NB: In higher plants the generations alternate in the life cycle of a plant; in lower plants reproduction is either through gametes (sexual) or spores etc. (asexual).

4 1.A haploid gametophyte generation that produces gametes (n) by mitosis... the gametes (n) fuse to form zygote (2n), the start of... 2.A diploid sporophyte generation that produces spores (n) by meiosis.

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6  Mosses (Bryophyta)  Ferns (Pterophyta/ Pteridophyta)  Seed plants (Spermatophyta) 1. Gymnospermae (cone-bearing plants producing seeds) 2. Angiospermae (flowering plants producing seeds) Exam guidelines require study of mosses and flowering plants to highlight alternation of generations.

7 Leaf-like structures of moss gametophyte Sporangium of moss sporophyte

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9 Fern leaf (sporophyte) with sori (groups of sporangia

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11 GYMNOSPERMS ANGIOSPERMS

12 Female cones at different agesMale cones Gymnosperms have two types of sporangia – female and male

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17 Mosses Gametophyte dominant Ferns, gymnosperms and flowering plants Sporophyte dominant


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