Plant Classification & Life Cycles

Plant Classification & 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 1: Seedless, Nonvascular Plants • Live in moist environments • Liverworts • Hornworts • Mosses

Mosses • Lack true leaves • Leaf-like structures only 1 cell thick • Rhizoids anchor into soil • Early inhabitant of new ecosystems (succession)

Moss Life Cycle • Gametophyte phase • Dominant stage • Carpet of moss growing near ground • Archegonium: produces female egg • Antheridium: produces male sperm • Sperm swims through water to fertilize egg • Sporophyte phase • Stalk grows up from the gametophyte • Sporangia houses haploid spores • Spores land and new gametophyte grows See appendix B in your text book

1) Moss gametophytes grow near the ground (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 is located 4) Sporophyte will create and release haploid spores . . . . . sporophyte gametophyte

5) Spores land and grow into new gametophytes 6) The process repeats . . . . . ground gametophyte

Plant Life Cycle Comparisons

Group 2: Seedless, Vascular Plants • Vascular system allows nutrient transport to greater heights • Club mosses • Horsetails • Ferns

Ferns • Seedless, vascular plants • Vascular: allows taller growth • Rhizoids: underground stems draw nutrients • Fronds: leaves uncurl • sporangia on underside • Sori: clusters of sporangia

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 See appendix B in your text book

1) Sporophyte creates and releases haploid spores . . . . Adult Sporophyte (diploid) ground

2) Spores land in the soil . . . . ground

3) From the haploid spores, a prothallus (haploid gametophyte) grows in the soil -- Rhizoids anchor Let’s zoom in ground

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 ground

6) Fiddlehead uncurls into fronds of ferns. 7) Cycle repeats -- Sporangia creates spores to be released . . . . ground

Group 3: Seed producing, Vascular Plants • Type 1: Gymnosperms • Cycads • Ginko • Conifers • Type 2: Angiosperms • Anything that flowers

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

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 Group 3: Seed producing, Vascular Plants

Gymnosperm example: Conifers Cone plants Needle-like leaves Common to lumber industry Evergreen, Pine, Redwood, Cedar Group 3: Seed producing, Vascular Plants

Conifers • Seed advantages • Don’t depend on water • Protects & nourishes embryo • Allow plants to grow in new locations • Conifers: woody cone houses seeds • Male cones: produce pollen • Female cones: produce egg • Pines, redwoods, spruce, 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 -- Pollen is the male gametophyte Let’s zoom into the female seed cone

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) Diploid embryo develops (sporophyte stage restarts)

7) After seeds harden, the cone reopens and the seeds are released

8) Seed will land ground

9) Seedling grows into (sporophyte)…the cycle repeats ground

Angiosperm Life Cycle

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 inanthers by meiosis • each spore divides bymitosis to form twohaploid cells= pollen grain pollen grain stamen anther

One female gametophyte can form in each ovule of a flower’s ovary. • Many cells can be made in the ovule • one cell becomes the egg • one cell becomes 2 polar nuclei • the rest die Polar nuclei (2n)

1. Pollen stick to animal or released into wind

Animal finds a new flower to feed on

2. Pollen transferred to the stigma (pollination)

3. Pollen tube grows and 2 nuclei transfer into the ovule .

female gametophyte egg sperm polar nuclei ovule 4. Flowering plants go through the process of double fertilization. Double Fertilization 1 sperm fuse with the polar nuclei = triploid (3n) endosperm 1 sperm fuse with the egg = zygote

endosperm seed coat embryo • Endosperm provides food supply for embryo 5. Each ovule becomes a seed. 6. The surrounding ovary grows into a fruit.

7. Flower dries up and fruit falls to ground.

8. Animals eat fruit….seeds come out the other end…

9. Seeds get dispersed 10. Seed germinates,(sporophyte) and the cycle starts over ground

22.2 Flower Life Cycle Plant Life Cycle Comparisons

End of the Semester!

Plant Classification & Life Cycles