DD BOT 131 Life Cycles and Alternation of Generations

DD BOT 131 Life Cycles and Alternation of Generations -...

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Unformatted text preview: Life Cycles Think of how many different life forms there are on planet Earth Alternation of Generations In order to continue living, each species requires some form of reproduction Typical "body" cells of plants and animals are diploid Typical "reproductive" cells of plants and animals are haploid, (maybe they should have been called monoploid) Haploid (1n) A cell with one set of DNA in nucleus. The single set of DNA contains a mixture of DNA from mother and father Diploid (2n) A cell with two sets of DNA in nucleus. Half of the DNA comes from the mother and the other half comes from the father 1 Two types of cell reproduction occur during the life of an organism (plants and animals included)... included)... Mitosis Cells divide and make new cells that are exact copies of themselves One cell makes two cells by mitosis 1) Mitosis 2) Meiosis After cell division occurs, cells may change (differentiate), but DNA in cell doesn't change Mitosis Cells divide and make new cells genetically different from themselves One cell makes four cells by meiosis Meiosis One diploid cell makes two diploid cells Fig. 12-7, p. 250 Daughter cells contain half the amount of DNA of parent cells. DNA is in a "recombined" form. Meiosis Occurs in flowers or other reproductive structures One diploid cell makes four haploid cells Fig. 12-7, p. 250 Fig. 12-7, p. 250 2 A sporophyte (multicellular plant made of diploid cells) A sporophyte makes spores by meiosis A gametophyte (small multicellular plant made of haploid cells), makes gametes by mitosis. Spore Single haploid cell made by meiosis. Spores then divide by mitosis and make small multicellular haploid organisms called gametophytes Gamete Single haploid "sex" cell which sex" is either male (sperm), or female (egg) How does an animal make an animal? In animals, gametes (sperm and eggs) are made from diploid cells by meiosis In plants, gametes (sperm and eggs), are made from haploid cells by mitosis Mitosis Sperm Animal Meiosis Zygote Egg Multicellular 2n diploid Single cells 1n haploid Single cell 2n diploid How does an animal make an animal? Mitosis How does a plant make a plant? Plant Multicellular 2n diploid Mitosis Sperm Animal Meiosis Sperm Zygote Mitosis Zygote Egg Multicellular 2n diploid Single cells 1n haploid Single cell 2n diploid Egg Single cell 1n haploid Single cell 2n diploid Haploid part of life cycle is only one cell big 3 How does a plant make a plant? Plant Multicellular 2n diploid Meiosis Male and female Spores Single cell 1n Haploid Mitosis How does a plant make a plant? Plant Multicellular 2n diploid Mitosis Male gametophyte Mitosis Mitosis Sperm Zygote Meiosis Female gametophyte Egg Single cell 1n haploid Male Mitosis and Plants have Mitosis female Female Spores this extra Male gametophyte Sperm Zygote Multicellular 1n Haploid Single cell 2n diploid step, Single cell 1n everything Haploid Haploid gametophyte Egg Single cell 2n diploid under this Multicellular 1n green blob Single cell 1n haploid How does a plant make a plant? Plant Multicellular 2n diploid Meiosis Male and female Spores Single cell 1n Haploid Mitosis BOTH diploid and haploid phases of a plant life cycle are MULTICELLULAR. MULTICELLULAR. Male gametophyte Mitosis Mitosis Sperm Zygote This is called "Alternation of Generations" Generations" A multicellular diploid generation and a multicellular haploid generation Female gametophyte Egg Single cell 1n haploid Multicellular 1n Haploid Single cell 2n diploid Haploid part of life cycle has multicellular component Make sure you remember that... that... A sporophyte makes spores A gametophyte makes gametes Fig. 12-8, p. 251 4 The gametophyte makes gametes The sporophyte makes spores Fig. 12-8, p. 251 Fig. 12-8, p. 251 Remember..... Plants in the sporophyte phase of their life cycle Both diploid sporophytes and haploid gametophytes are multicellular Dominant generation is bigger -Lives longer -Feeds itself high Relative dominance gametophyte sporophyte low Algae and fungi Bryophytes Lower vascular plants Conifers Flowering plants Evolved long ago Evolutionary time Evolved recently 5 ...
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