Modern Biology Chapter 32 Plant Life Cycles Modern Biology Chapter 32

Alternation of Generations: the overview

Mosses: Structures involved What you associate with mosses is a gametophyte Gametophytes are haploid

…Because repetition is the spice of life!

Mosses: Development/ Growth Mitosis occurs producing a diploid sporophyte Sporophyte remains attached to the gametophyte Diploid Sporophyte cannot feed itself, but is genetically different than the gametophyte

Mosses: The next generation… Diploid sporophyte produces cells that undergo meiosis; this produces haploid organisms, or gametophytes.  

Ferns

Ferns: Structures involved What you associate with ferns is the sporophyte Sporophyte grows from gametophyte Gametophytes are tiny (10 mm) Antheridium Archegonium

Ferns: Development/ Growth Mitosis occurs producing a diploid sporophyte with fronds Sporophyte remains attached to the gametophyte, crushing it as it increases in size

Ferns: The next generation… Specialized cells, usually on the underside of the fronds, undergo meiosis and produce spores.

Conifers

Conifers: Fertilization Typically the conifers much reach maturity before they can reproduce sometimes up to 30 years. Conifers can reproduce without water for the sperm to swim in. Sexual reproduction can actually take years

Flowering Plant Life Cycles Modern Biology Chapter 32

Flowering plants: Structures involved

Ovule: female sex cell Consists of a mega sporangium surrounded by two integuments

Ovule: female sex cell One large diploid megaspore mother cell undergoes meiosis and produces 4 haploid megaspores

Ovule: female sex cell One megaspore enlarges and the other three wither away….

Ovule: female sex cell Remaining mega spore undergoes three mitotic divisions to produce 8 haploid nuclei

Ovule: female sex cell Two nuclei move to the center of the cell while the remaining 6 move to the polar ends- three to each side

Ovule: female sex cell Cell walls form around the 6 nuclei at the ends One of these 6 cells becomes the egg, (the others die at fertilization) Embryo sac consists of 7 cells and 8 nuclei- this is the mature female gametophyte

Pollen: male sex cell Microspore mother cells undergo meiosis and produces 4 haploid microspores, each of which undergoes mitosis to form two haploid cells

Pollen: male sex cell Wall develops around microspores and the two celled structure is a pollen grain- this is the mature male gametophyte

Pollen: male sex cell The larger cell will produce the tube cell containing the tube nucleus. When attached, the tube nucleus will make a pollen tube The smaller cell is the generative cell It will undergo yet another mitotic division to produce two sperm

Flowering plants: Fertilization (Double Fertilization) Pollen tube grows from pollen (takes about a day)

Flowering plants: Fertilization (Double Fertilization) The two cells produced from the generative cell enter the ovule through the pollen tube One of the sperm fuses with the egg to form a diploid zygote This will be the embryo

Flowering plants: Fertilization (Double Fertilization) The two cells produced from the generative cell enter the ovule through the pollen tube The other sperm fuses with the two nuclei in the megaspore to produce a triploid nucleus. This will be the endosperm- the nutrients contained within a seed so that the embryo has energy to remain alive and begin the growth process

Video!!

Flowering plants: Seed structure

Flowering plants: Seed germination Seeds can remain dormant for many years When the conditions are right, the seed will germinate

Flowering plants: Seed germination Typically roots come before leaves

Flowering plants: fruit