Alternation of generations

Transcription

1 Plant Life Cycles Allplants alternate between two phases in their life cycles Alternation of generations Sporophyte (diploid) Begins when sperm fertilizes egg (zygote) Diploid zygote divides by mitosis to create a mature sporophyte Meiosis produces haploid cells called spores Haploid spores released Alternation of generations Gametophyte (haploid) Begins with spores created by meiosis Spore grows into gametophyte Male gametophyte creates sperms Female gametophyte creates eggs Sperm & egg create diploid zygote (process repeats) Group Goup1: Seedless, ess, nonvascular ascua plants pa ex: moss Nonvascular plants have a dominant gametophyte t phase moss gametophytes look like green carpet moss sporophytes shoot up as stalklike structures sporophyte (2n) capsule spores (1n) gametophyte (1n) 1) Moss gametophytes grow near the (haploid stage) 2) Through water, sperm from the male gametophyte will swim to the female gametophyte to create a diploid zygote 3) Diploid sporophyte will grow from the gametophyte where the zygote islocated 4) Sporophyte will create and release haploid spores 5) Spores land and grow into new gametophytes 6) The process repeats sporophyte gametophyte gametophyte

2 Plant Life Cycle Comparisons Plant type Sporophyte Gametophyte Dominant? Moss Stalk with cup More familiar, GAMETOPHYTE (capsule) at tip, which is where spores are carpet like plant that produces specialized gametes produced Fern More familiar, leafy plant with clusters of spore producing sacs (sori) Haploid plant body (prothallus) is size of a finger nail, produces both male and female parts Conifer More familiar like pine trees, Pollen grains are male produces male and gametophytes female cones that sperm, female microscopic eggs Group 2: Seedless, Vascular Plants Ex: Ferns Ferns Seedless, vascular plants Vascular: allows taller growth Rhizoids: under stems draw nutrients Fronds: leaves uncurl sporangia on underside Sori: clusters of sporangia See appendix B in your text book Fern Life Cycle Sporophyte phase Dominant stage Sporangia produces haploid spores Spores released into air Gametophyte phase Spore grows into prothallus Archegonium: produces female egg Antheridium: produces male sperm Sperm swims to egg Zygote begins sporophyte stage 1) Sporophyte creates and releases haploid spores 3) From the haploid spores, a prothallus (haploid gametophyte) grows in the soil Rhizoids anchor Let s zoom in Adult Sporophyte (diploid)

3 4) Sperm swim through water from the antheridium to the archegonia Let s zoom back out 5) Diploid sporophyte (fiddlehead) grows from the prothallus prothallus eventually dies 6) Fiddlehead uncurls into fronds of ferns 7) Cycle repeats Sporangia creates spores to be released Plant Life Cycle Comparisons Plant type Sporophyte Gametophyte t Dominant? Moss Stalk with cup More familiar, GAMETOPHYTE (capsule) at tip, which is where spores are carpet like plant that produces specialized gametes produced Fern More familiar, leafy Haploid plant body plant (fronds)with clusters of spore producing sacs (sori) (prothallus) is size of a finger nail, produces both male and female parts Conifer More familiar like Pollen grains are pine trees, produces male and male gametophytes female cones that sperm, female microscopic eggs Group 3: Seed producing, Vascular Plants 1) Seed plants don t depend on water to reproduce Pollen (contains sperm) combines with egg Egg hardens into a seed 2) Nourishment and protection Nourish: Nutrients inside seed for the embryo Protection: Hard shell 3) Allow dispersal Carried by wind, water, animals Group 3: Seed producing, Vascular Plants Type 1: Gymnosperms Seeds not enclosed in a fruit produced inside cones Cone = reproductive structure Male cones: produce pollen Female cones: produce eggs and seeds

4 Group 3: Seed producing, Vascular Plants Gymnosperm example: Conifers Cone plants Needle like leaves Common to lumber industry Evergreen, Pine, Redwood, Cedar The sporophyte is the dominant phase for seed plants 1) Male and female seed cones grow in adult sporophytes 2) Pollen grains released from the male seed cones Pollenisthe malegametophyte Let s zoom into the female seed cone 7) After seeds harden, the cone reopens and the seeds are released 3) Pollen grain sticks to the female ovule 4) Pollen tube grows from the male spore 5) Two nuclei transfer into female spore one fertilizes the egg 6) Diploidembryo develops (sporophyte stage restarts)

5 8) Seed will land 9) Seedling grows into (sporophyte) the the cycle repeats Plant Life Cycle Comparisons Angiosperm Life Cycle Plant type Sporophyte Gametophyte Dominant? Moss Stalk with cup More familiar, GAMETOPHYTE (capsule) at tip, which is where spores are produced carpet like plant that produces specialized gametes Fern Conifer More familiar, leafy plant with clusters of spore producing sacs (sori) More familiar like pine trees, produces male and female cones that Haploid plant body (prothallus) is size of a finger nail, produces both male and female parts Pollen grains are male gametophytes sperm, female microscopic eggs Flowering plants are pollinated when pollen grains land on stigma Wind pollinated flowers small flowers and large amounts of pollen Animal pollinated flowers larger flowers and less pollen (more efficient) Fertilization takes place within the flower Male gametophytes, or pollen grains, are produced in the anthers male spores produced in anthers by meiosis each spore divides by mitosis to form two haploid cells= pollen grain pollen grain stamen anther

6 One female gametophyte can form in each ovule of a flower s ovary o Many cells can be made in the ovule one cell becomes the egg one cell becomes 2 polar nuclei the rest die 1 Pollen grains are released eased Wind or animals Polar nuclei (2n) 2 Pollen grains land on the stigma (pollination) 3 Pollen tube grows and 2 sperm nuclei transfer into the ovule Let s zoom in

7 222 Flower Life Cycle 4 Flowering plants go through the process of double fertilization female gametophyte 222 Flower Life Cycle 5 Each ovule becomes a seed Endosperm provides food supply for embryo endosperm seed coat Double Fertilization egg The surrounding ovary grows into a fruit embryo sperm polar nuclei ovule 1 sperm fuse with the polar nuclei = triploid (3n) endosperm 1 sperm fuse with the egg = zygote 222 Flower Life Cycle 6 Seeds get dispersed 7 Seed germinates(sporophyte), and the cycle starts over Plant Life Cycle Comparisons Plant type Sporophyte Gametophyte Dominant? Moss Stalk with cup (capsule) at tip, which iswhere spores are produced More familiar, carpet like plant that produces specialized gametes GAMETOPHYTE Fern More familiar, leafy plant Haploid plant body (prothallus) with clusters of spore producing sacs (sori) is size of a finger nail, produces both male and female parts Conifer More familiar lk like pine Pollen grains are male (gymnosperm) trees, produces male and female cones that gametophytes sperm, female microscopic coscopc eggs Flower (angiosperm) More familiar apple tree, peach tree, zucchini, berries, etc Contain flowers that produce male and female spores Pollen grains are male gametophytes 2 haploid cells = pollen tube + sperm, Female gametophyte in ovule egg + 2 polar nuclei