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Evolution and Basic Structure of
Plants
• There are four major classes of plants:
– Bryophytes
– Pyeridophytes
– Gymnosperms
– Angiosperms
How are plants classified?
Bryophytes:
1) First land plants
2) Include mosses
3) Nonvascular plants
(grow close to the ground)
4) Lack Seeds
Mosses
How are plants classified?
Pteridophytes:
1) Have Vascular Tissue
2) Lack Seeds
3) Have Lignin in cell walls
Ferns
How are plants classified?
Gymnosperms:
1) Have Vascular tissue
2) Have seeds (plant embryo & food supply)
3) Seeds are “naked”
(not enclosed in an ovary)
4) Have Pollen (male sperm)
Male Pollen Cone
contains
Male gamete (sperm)
Pine Tree
How are plants classified?
Angiosperms:
1) Have Vascular tissue
2) Flowering plants (flower is a reproductive structure)
3) Have seeds surround by ovaries
(fruit)
4) Have pollen
Seed
Ovary
Flower: Reproductive Organ of
plant
Fruit: Seed-bearing part of a plant
+
Seed: Contains plant embryo and
food source
Leaf: Site of gas exchange and
contains most of the chloroplasts
Stem: Transports water and
nutrients upwards and food away
from leaves; support/structure
Roots: Absorbs water and
nutrients from soil; anchors plant to
the ground
Cross-Section of
a Leaf
Cuticle
• Prevents water loss
• Acts as a barrier to fungi and other
invaders
Upper Epidermis
• Closely packed
Palisade Layer
• Photosynthetic cells
• Contain chloroplasts
Spongy Layer
• Contain chloroplasts
• Larger spaces between cells (for gas
exchange)
• Closer to stomata
Veins – Vascular Tissue
• Transports fluids throughout leaf through
the use of xylem and phloem
Stomates (stoma)
• Tiny openings on the lower epidermis
(where gas exchange takes place)
Guard Cells
• Each stoma is surrounded by 2 guard cells
which can change their shape to regulate
gas exchange