Gymnosperms are "Naked seed plants"

gymnosperms

the first seed plants'

1. “naked seed plants”

   1. not enclosed in fruits

2. include conifers, cycads, ginkgo and gnetophytes

3. 800 of so species divided into 4 phyla

naked

What does “gymno” mean?

seed

What does “sperm” mean?

sporophytes

in most gymnosperms, are woody trees or shrubs

1. leaf shapes are varied

Cycads

phylum Cycadophyta

1. in tropical and subtropical regions

2. produce large cones

3. dominated the Mesozoic era

4. now, most seen as ornamental plants

ginkgos

phylum Ginkgophyta

1. also called maiden-hair tree

2. have distinctive, fan shaped leaves

3. only one species still exists: Ginkgo Biloba

4. no longer grows in the wild

5. male and female organs on seperate plants

   1. fleshy seeds of female have foul odor

conifers

phylum Pinophyta

1. ex. pine trees

2. needle or scalelike leaves

3. produce egg cells and pollen inside cones

4. also called evergreens, retain leaves all year

   1. sheds needles a few at a time

gnetophytes

phylum Gnetophyta

1. botanists struggle with this classifications

   1. some details of life history suggest a close relationship with flowering plants, but molecular evidence places them with conifers

   2. ex. Welwitschin: a desert plant with a single pair of large, strap shaped leaves that persist throughout it’s life

pollen and seed

Conifers produces what two thing in their cones?

sporophyte

The mature { } produces cones, the organs that bear the reproductive structures

1. each female cone scale bears two ovules on it’s upper surface

   1. Inside each ovule, a sporangium undergoes meiosis and produces four haploid megaspores, only one of which develops into a female gametophyte

      1. over many months, the female gametophyte give rise to two or six egg cells

   2. At the same time, male cones have sporangia (on the scales)

      1. through meiosis, sporangia produces microspores, which become windblown pollen grains

   3. Pollination

   4. Pollen grain germinates

      1. Pollen tube grows through the ovule towards the egg cell

   5. 2 haploid sperm nuclei develop inside the pollen tube

      1. one sperm cell nucleus fertilizes the haploid egg cell

      2. the other disintegrates

   6. Resulting zygote is the first cell of the sporophyte generation

2. The whole process is so slow that fertilization occurs about 15 months after pollination

ovules

produce the female reproductive cells (and eventually develops into seed)

1. within the ovule, the haploid tissue of the female gametophyte nourishes the developing diploid embryo, which soon becomes dormant

2. A tough protective seed coat develops

3. if conditions are favorable, the seed germinates

pollination

1. occurs when pollen grains settle between the scales of female cones and adhere to a sticky secretion