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Plant Diversity:
Evolution of Seed Plants
Previously:
Now:
First important change - Vascularization
-addition of cells joined to form tubes within the plant
First important change - Vascularization
-addition of cells joined to form tubes within the plant
phloem
Vascular bundle
xylem
First important change - Vascularization
-addition of cells joined to form tubes within the plant
Phloem – transports sugar and other nutrients
Xylem – transports water and minerals from roots
First important change - Vascularization
-addition of cells joined to form tubes within the plant
Xylem cells - lignified
Lignin
First important change - Vascularization
-addition of cells joined to form tubes within the plant
Lignin – provides support – allows plants to grow taller
Second important change: seeds
LIFE ON LAND – TERRESTRIAL ADAPTATIONS
- Seeds
- Reduced gametophytes
- Heterospory
- Ovules
- Pollen
Second important change: seeds
Why have reduced gametophytes
ovule
Pine cone
(=female
gametophyte)
Protection from UV and
desiccation
Nutrients from sporophyte
HETEROSPORY
Microsporangia  microspores  male gametophyte
Megasporangia  megaspores  female gametophyte
OVULES
Megasporangium + megaspore + integument (developed from sporophyte) = OVULE
POLLEN
Microspore  pollen grain
Pollen wall
Male gamete
Advantages of pollen
1) Outer coat (Pollen wall) protects microspore
2) Permits wide range dispersal by wind, animals
Advantages of seeds
1) Outer coat protects sporophyte embryo
2) Supply of food – allows long term dormancy
GYMNOSPERMS
Cycads
GYMNOSPERMS
Ginkos
GYMNOSPERMS
Conifers
Gymnosperm Life Cycle
ANGIOSPERMS – FLOWERING PLANTS
-distinguished by being able to produce flowers and fruits
ANGIOSPERMS – FLOWERING PLANTS
Flower Structure – four rings of modified leaves
Carpel
Pistil
Style
Ovary
Stamen
Filament
Petals
Anther
Sepals
ANGIOSPERMS – FLOWERING PLANTS
Fruits – mature ovary of an angiosperm
- as seeds develop – wall of ovary thickens
e.g. pea pods
ovule
Ovary wall
Kinds of Fruits
1. Simple – single ovary (one to several seeds)
-fleshy or dry
Pomes
Fleshy
Drupes
Berries
Dry
Nuts
Kinds of Fruits (continued)
2. Aggregate – single flower with many ovaries
Blackberries
Raspberries
3. Multiple fruits - fused ovaries of multiple flowers
Pineapple
ANGIOSPERM LIFE CYCLE
CLASSIFICATION OF ANGIOSPERMS
Monocotyledonous
(“monocots”)
Dicotyledonous
(“dicots”)
Summary - Derived Traits of Seed Plants