Bio 314 - Exam 2 : Gymnosperms part 2

Synapomorphies of Gnetales

• vessel elements in xylem

• Ephedroid pollen

3 types of Gnetales

1. Ephedra

2. Gnetum

3. Welwitschia

For all of the scientific names just “aceae”

Characteristic of Ephedra:

• Mostly in arid environments

• Shrubs w reduced whorled leaves

• Contains lots of secondary compounds

• Double fertilization

Characteristics of Gnetum

• woody vines

• Leathery leaves

• Wet, tropical climates

• Insect pollination; typically moths

• Both male and female cones produce pollination droplets

• loss of ephedroid pollen

True or false Welwitschia is a monotypic genus (only one species)

True

Where does welwitschia exclusively grow :

Namib desert Africa

3 types of welwitschia leaves

• Cotyledons

• Photosynthetic leaves

• Bracts subtending cones

Conifers tend to have ______ distribution

temperate

Characteristics of Conifers

• all long lived

• slow growing

• slow to reproduce

Best way to describe conifer sperm

lose flagella

Characteristics of confer leaves

• “needle like”

• single vein down the middle

• megaphylls leaves

• Tough think cell wall

Most conifers are

evergreen

Fascicle:

short short + needles

Number of needles in a fascicle is often:

species specific (typically 2-5)

2 Major families of conifers

1. Pinaceae (pines)

2. Taxaceae (Yews)

Pollen Tube

delivers sperm to the female gametophyte inside the ovule

Is water required for sexual reproductions of conifers

No

Conifer Life Cycle

1. Mature sporophyte has both immature ovulate cone + pollen cone

2. Meiosis occurs

3. Pollen grains travel and land in ovule

4. Male gametophyte develops pollen tube to allow sperm to enter ovule

5. Fertilization occurs producing zygote

6. Zygote develops onto mature seed cone and the underdeveloped sporophyte

(Note double fertilization)