Plant Reproduction What Are the Basic Features of Plant Life Cycles? How Is Reproduction in Seed Plants Adapted to Drier Environments? What is the Function and Structure of the Flower?
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.
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 REPRODUCTION! 1:21
Asexual Reproduction • Binary fission • happens in bacteria, amoeba, some algae • one parent cell splits into 2 identical daughter cells • Budding • happens in yeast, hydra, corals • parent produces a bud • bud gets detached and develops into offspring which is identical to parent
Binary Fission Rod-Shaped Bacterium, hemorrhagic E. coli 2 daughter cells are identical to parent
Spore Formation Fern Fungi
Sexual Reproduction in Animals • involves specialized sex cells called gametes • the union of a male and female gamete results in the formation of a zygote that develops into a new individual
Sexual Reproduction in Plants Female Parts Male Parts (Pistil) pollen (male) + ovule (female) → single-celled zygote → multi-celled embryo (contained in a seed) → new individual
Sexual Reproduction in Plants • stamen is the male part and contains pollen • carpels or pistil is the female part and contains ovule (eggs) • pollen grains from the anther are transferred to the stigma by the process of pollination • self pollination (plant pollinates its own eggs) • cross pollination (pollen from one plant pollinates another plants eggs)
Pollination • flowers are designed to lure insects to help with the pollination process • also wind, animals, birds can transport pollen
Some Organisms do Both • most plants that produce seeds (sexual reproduction) can also reproduce asexually by things like cuttings or runners • this gives them an advantage for survival sponges and hydra mosses
Asexual Reproduction advantages does not require special cells or a lot of energy can produce offspring quickly in a stable environment creates large, thriving population disadvantages limited ability to adapt face massive die-off if environment changes Sexual Reproduction advantages lots of variation within a species able to live in a variety of environmental settings able to adapt to changes in the environment disadvantages needs time & energy produce small populations Which is Better?It depends!
Asexual Reproduction • Natural “cloning.” Genetically Identical. • Fast, no mate required. • Beneficial for plants that must compete for scarce resources (Stable Environs). • Part of a single plant divides by mitosis to give rise to a new plants. • Spreading of runners (strawberries) • Production of bulbs (daffodils) • Sprouting of rhizomes (irises)
Sexual Reproduction • Fusion of egg and sperm cells (haploid), from meiosis, gamete formation and fertilization. • May be limited to a certain season. • Slower than asexual reproduction. • Allows genetic mixing, increasing variability in a population. Two parents give rise to genetically variable offspring. Favored in variable environments.
Alternate “Generations” • All plant life cycles are characterized by alternatingofportions (haploid-to-diploid-to-haploid). • Multicellular diploid plants (sporophytes) and multicellular haploid plants (gametophytes) take turns producing each other during the reproductive life cycle. • Sporophyte: diploid (2n), produce haploid spores by meiosis. • Gametophyte: haploid (n), produce gametes by mitosis.
Life Cycle • Diploid sporophyte (spore-forming plant) produces haploid spores by meiosis. • Spore germinates (begins to grow and develop); divides repeatedly by mitosis forming a haploid gametophyte (gamete-forming plant). • Gametophyte produces haploid sperm and eggs by mitosis (gametes are produced at different times to prevent self-fertilization).
Life Cycle • Sperm and egg fuse to form a diploid zygote (fertilized egg). • Zygote undergoes repeated mitosis to form a new diploid sporophyte plant.
Non-Flowering Plants • Mosses, ferns, and related plants have motile, swimming sperm. • Reproduction in these plants requires wet conditions, and requires having male and female parts close together. • Living conditions, plant size, and genetic mixing is limited.
Group 1: Seedless, Nonvascular Plants Live in moist environments to reproduce Grow low to ground to retain moisture (nonvascular) Lack true leaves Common pioneer species during succession Gametophyte most common (dominant) Ex: Mosses, liverworts, hornworts
A. How Do Mosses/Liverworts Get Water? • Nonvascular plant • Only about 2 to 5 cm tall, cling to damp soil, sheltered rocks, and the shady side of trees • Leaves have only one or two cells • Rhizoids: root-like fibers that are on the outside; take in water from surroundings Continue on to next slide.
A. How Do Mosses/Liverworts Get Water? • Spores: cells that can develop into new organisms (seedless) • Close relative club mosses, horsetails, ferns, and spike mosses are VASCULAR • They grow thick and tall Click this link to see pictures of moss and answer Question 1 on your sheet.
Life Cycle of Mosses • Asexual reproduction: a plant that needs only one type of cell to reproduce • This process uses spores • Sexual reproduction: a plant that needs two types of cells to reproduce • This process completes the cycle to allow reproduction Continue on to next slide.
Alternation of generations: process of going from asexual reproduction to sexual reproduction B. Life Cycle of Mosses Click this link to learn more about what causes moss to grow and answer Question 2.
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 zygote 4) Sporophyte will create and release haploid spores Diploid sporophyte . . . . . egg zygote zygote egg egg zygote egg zygote male male Haploid gametophytes female female female male female male
5) Haploid spores land and grow into new gametophytes 6) The process repeats . . . . . ground Haploid gametophytes
. . . . . sporophyte egg zygote egg zygote egg zygote egg zygote male male Haploid gametophytes female female female male female male
Group 2: Seedless, Vascular Plants Vascular system allows Taller growth Nutrient transportation Live in moist environments swimming sperm Gametophyte stage Male gametophyte: makes sperm Female gametophyte: makes eggs Sperm swims to fertilize eggs Sporophyte stage Spores released into air Spores land and grow into gametophyte Ex: Ferns, Club mosses, Horsetails
Parts of a Fern • Fronds: the front leaves of ferns • Rhizome: underground stem which ferns grow from; roots sprout from this Continue on to next slide.
Life Cycle of Ferns • Reproduce by alternation of generation; just like mosses • Fern seeds are on the fronds of the ferns and scatter on the ground Click this link to see the different types of ferns and the life cycle of a fern.
1) Sporophyte creates and releases haploid spores Adult Sporophyte . . . . ground
2) Haploid spores land in the soil . . . . ground
3) From the haploid spores, gametophyte grows in the soil Let’s zoom in Fern gametophytes are called a prothallus ground
4) Sperm swim through water from the male parts (antheridium) to the female parts (archegonia)…zygote created Let’s zoom back out egg zygote egg zygote egg zygote
5) Diploid sporophyte grows from the zygote sporophyte Fern gametophytes are called a prothallus ground
6) Fiddle head uncurls….fronds open up 7) Cycle repeats -- Haploid spores created and released . . . fiddlehead frond . ground
2) Haploid spores land in the soil . . . . ground
3) From the haploid spores, gametophyte (called the prothallus) grows in the soil Let’s zoom in ground
4) Sperm swim through water from the male antheridium to the female archegonia Let’s zoom back out egg zygote egg zygote egg zygote
5) Diploid sporophyte grows from the zygote fiddlehead sporophyte ground
6) Fiddlehead uncurls….fronds open up. 7) Cycle repeats . . . . ground
Review • Why do moss grow so low to the ground? • Which stage is the main stage of moss: sporophyte or gametophyte? • How do moss reproduce? • What is the major difference between moss and ferns? • What are the leaves of ferns called? • What is needed for moss and ferns to reproduce? • Which stage is the main stage of ferns: sporophyte or gametophyte? • What stage is created when sperm and egg fuse: sporophyte or gametophyte? • Name the gametophytes of ferns.