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Lecture 12

BIO SCI 94 Lecture Notes - Lecture 12: Sequoiadendron, Moss, Stoma


Department
Biological Sciences
Course Code
BIO SCI 94
Professor
Brandon Stuart Gaut
Lecture
12

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Lecture : Non-Vascular/Vascular Plants &
Vascular Tissue
Land Plants
Recent, in evolutionary terms (475 million yrs ago)
Evolved from green algae
Solved 2 difficult challenges for life on land
1. Sexual reproduction --> embryophyte
2. Survive contact w/ air --> cuticle, pores (stomata)
vascular tissue (eventually): allows nutrients & water to go up & down the plant
4 Groups of Land Plants
1. Non-vascular plants
o Don't have specialized vascular tissues
o Do have embryophytes
2. Seedless vascular plants
o Ferns
3. Gymnosperms --> seed
o Pine trees
4. Angiosperms --> flowers
o Have seeds too
o Most successful
*From textbook
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Non-Vascular Plants
Embryophytes that have a waxy cuticle layer & some have stomata
Lack true vascular tissues which makes transport of water & nutrients from the soil to the leaves difficult
o Thus they're limited to very moist environments & they don't grow tall
Moss Life-Cycle
o
*From textbook
o Mature sporophyte (2n) undergoes meiosis to make spores --> spores (n) dispersed by wind -->
spores undergo mitosis --> spores develop into gametophytes (n) --> made male and female
gametophytes --> sperm has to swim to a female gametophyte --> sperm fertilizes the egg -->
zygote (2n) --> zygote grows out of the top of the gametophyte
Male gametophyte has antheridia (tissue that makes sperm)
Female gametophyte has archegonia (structure that surrounds the egg & protects the embryo
and keeps it from drying out)
Non-Vascular Plants Alternation of Generations (look at the moss life-cycle for reference)
1. Has alternation of generations
2. Gametophyte is dominant (sporophytes are the dominant forms of ferns, gymnosperms, &
angiosperms)
3. Male & female gametophytes are independent; there are separate male & female producing spores
4. Sperm develop in the antheridium (the male reproductive organ)
Motile sperm are released from the antheridium & swim to the egg (in the archegonium)
*From Prof. Gaut's slides
5. Egg develops in the archegonium, a structure of sterile (non-reproducing) cells that shelters the egg
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Egg is fertilized in the archegonium when the sperm swim to it
*From Prof. Gaut's slides
6. Zygote (fertilized egg) develops into an embryo in the archegonium
The archegonium helps protect the egg, the zygote & the embryo from desiccation (drying
out)
The archegonium is the defining feature of embryophytes and an important adaptation for
reproduction on land!
7. In mosses, the sporophyte grows out of the archegonium & is physically attached
Sporophyte is dependent upon the gametophyte for water & nutrients, & the sporophyte is
usually short-lived
8. IMPORTANT: fertilization still requires water, b/c the motile sperm need water to reach the
archegonium & fertilize the egg
2 things limit the distribution & size of mosses
1. Require water for fertilization --> can't inhabit dry environments
2. Don't have a good vascular system --> most of the plant needs to be near water to ensure that all
the cells get water
This limits the size of the mosses (they're usually a few cm in height)
Polytrichum sp. (moss)
o Leafy part; gametophyte
o Stalk coming out: sporophyte
Allisonia (liverworts)
Folioceros fuciformis (hornworts)
Small b/c they don't have vascular tissue
Name 3 non-monophyletic groups.
1. Green algae
2. Nonvascular plants
3. Seedless plants
Which of the following are embryophytes?
A. Nonvascular plants
B. Seedless vascular plants
C. Gymnosperms
D. Angiosperms
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