Lecture Notes -- History of Plants Bio104/download word document for ease of reading.

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470 Mill years ago

Evidence sheets of moss on rocks and the edge of water

Journey of evolution - to land

Earth changed from tropical - to seasons (hot cold, dry, wet)

Further adoption to land -climate


Mosses, Liverwort, etc.

Are used as examples of plants without most modern evolutionary adoption

But: they are not the primitive ancestors of other plants

NOTE: vascular plants came first; non vascular plants came as a branch

Characteristic of Bryophytes

Non vascular plant

Have no veins (vascular tissue)

No roots for penetration of the soil

Are small

Lack support to get big

Parts mostly stay close the ground

So they can get water and nutrients

Other characteristics

No functioning stomata (pores)

They have little control over water loss

Have little or no cuticle

Reproduces via spores (not seeds)

Have flagellated sperm

NOTE: Peat Moss

Genus- Sphagnum-comes from Canada

Agriculture- used as soil additive - retains moisture

Is acidic - prevents seeds form damping off (damping off is a fungus decease)

Also used as fuel

Grows very fast

Does not root

Form mats many feet thick

Make bricks -burn good

Better than wood

Worse than coal

Trends in plant evolution

1. better vascular tissue

a. xylems=veins in plants

Carries water

Dissolves-nutrients (N, P, K)

b. "most primitive xylem are called tracheids

Is made out of dead cells

c. advanced xylem -(mixture more vessel elements)

Occurring in seed plants-gymnosperm (no flowering seed plants)

Has a vessel element

2. Unequal branching

a. Earliest vascular plant - no branch

b. Then two branch

c. Then dicatomous branch-equal branching

d. Unequal branching

Get tall faster

More efficiently in food competition

3. Secondary Growth

Growth in diameter (girth)

Through adding layers of xylem

They grow taller

Persist form season to season

Survive from season to season...