Gymnosperms and Angiosperms, the seed plants

    I. Reasons why sed plants are very successful
   II. Gymnosperms = naked seeds.
            A. seeds are formed on open surface of cone scale.  No flowers or fruits!
            B. Four divisions:  Cycad, Ginkgo, Gnetae, and Conifer (pines, redwoods, hemlocks, cedars….)
            C. Evolutionary advancements over the ferns
                    1. Seeds
                    2. Lack of dependence on water for fertilization.  Has air-borne pollen.
                    3. More dominant sporophyte
                    4. Advanced vascular tissue
                    5. Secondary growth (lateral thickness)
            D. The sporophyte generation is dominant with the gametophyte generation is contained in and dependent on the sporophyte.
            E. The sporophyte produces two types of spores (heterosporous):
                    1. megasporangium undergo meiosis to produce megaspores that give rise to egg cells  (located in ovulate cones = female cones)
                    2. microsporangium undergo meiosis to produce microspores that give rise to pollen grains (located in staminate cones = male cones)
            F. Sexual Reproduction
                    1. Pollination and fertilization
                        a)  pollen is carried by the air (wind borne).  Exception:  Cycads are both wind and beetle pollinated.
                        b)  pollen grains from the male cone stick to the sticky parts of female cones.
                        c)  the pollen grain tube cell forms to transfer male sperm to female gametophyte for fertilization
                    2. trees can be monoecious (male and female cones on the same tree) or dioecious (male and female cones on separate trees).
                    3. Seeds are multicellular dormant 2n embryo’s surrounded by nutritive tissue (residual 1n megagametophyte tissue).
 

    III. Angiosperms = covered seeds. Flowering Plants.
            A. Has flowers, fruits, and seeds (that form within fruits).
            B. They are found in almost every terrestrial environment
            C. Evolutionary advancements over the gymnosperms:
                    1. Flowers (many use animal pollinators to assure greater reproductive success)
                    2. Fruits and seeds are adapted for various types of dispersal
                    3. Double fertilization: the seed has a 2n embryo and 3n endosperm (nutritive tissue).
            D. The sporophyte produces two types of spores (heterosporous):  egg cells and pollen grains
            E. Parts of a typical flower (see flower hand out)
                    1. Male parts: the stamen = the male sex organs composed of the filament and the anther, the organ that produces pollen.  Inside the pollen are the two male sperm (the male gametophytes).
                    2. Female parts:  the carpel (also called a pistil) consists of:
                        a) The stigma is the region of a carpel that serves as a receptive surface for pollen grains
                        b) The style leads to the ovary, which is at the base of the carpel.
                        c) The ovary is the enlarged base of a carpel (or fused carpels) that contains the ovules (female gametophytes).
            F. Sexual Reproduction
                    1. Pollination:
                        a) pollen lands on the stigma, then the pollen tube grows down the style through the ovary and into the ovule to the egg.
                    2. Double fertilization:
                        a) one sperm nucleus fuses with an egg cell in ovule making 2n zygote
                        b) another sperm nucleus fuses with two 1n polar nuclei in the ovule making 3n endosperm (nutritional food source)
                    3. Development
                        a) ovule develops into a seed
                        b) ovary develops into a fruit (non-fertilized tissue)
            G. Two classes of angiosperms: monocots and dicots
                    1. As the zygote grows into the embryo, the first leaves of the young sporophyte develop and are referred to as cotyledons (seed leaves).
                        a) Monocots (monocotyledons). Examples: grasses, corn, lily, etc.
                        b) Dicots (dicotyledons). Examples: beans plants, oak trees, roses, etc.
 
 

    FEATURE                                                MONOCOTS                                                         DICOTS
   cotyledons                                                             1                                                                           2

    leaves                                                        narrow  leaves                                                     broad leaves
                                                                       parallel venation                                                 net venation

    root system                                              fibrous root                                                          taproot

    number of floral parts                            in 3's                                                                      in 4's or 5's
 

KNOW THE PARTS OF A TYPICAL FLOWER:

Additional sites of interest:
Monocots vs. Dicots