30-Plant Diversity II-The Evolution of Seed Plants.ppt -...

Plant Diversity II: The
Plant Diversity II: The
Evolution of Seed Plants
Evolution of Seed Plants
Chapter 30
Chapter 30

Concept 30.1: Seeds and pollen grains
are key adaptations for life on land
•
Characteristics common to all seed plants
1. Seeds- housing for the embryo
2. Reduced gametophytes (size)- sporophyte is larger than
gametophyte
3. Heterospory- being able to produce both male and female
spores
4. Ovules- eggs
5. Pollen- vehicle for sperm

Gametophyte/sporophyte relationships
• Gametophytes of seed plants develop within the walls of spores retained
within tissues of the parent sporophyte
• No longer dependent on water for fertilization
Figure 30.2

Ovules and Production of
Eggs
•
An ovule consists of a megasporangium (tissue that makes the megaspore),
megaspore (eventually becomes the egg), and protective integuments (hair, nails,
skin in humans; acts as a barrier)
Figure 30.3a

Pollen and Production of Sperm
• Microspores (sperm) develop into pollen grains
– Contain ♂ gametophyte
•
Pollen can be dispersed by water, air or animals, eliminates the need for
water in fertilization )means transporting egg from one plant to that of
another
•
Sperm is smaller than the egg

If a pollen grain germinates,
…
• It gives rise to a pollen tube that discharges sperm into the ♀ gametophyte within the
ovule
•
Germination- development into something more complex
•
Pollen tube releases sperm into female gametophyte
Figure 30.3b

A Seed
• Develops from the whole ovule
• Includes sporophyte embryo, food supply, protective coat
•
Every seed contains a plant embryo
• Sporophyte is the dominant generation
• Some seeds are going to be harder than others
•
Seeds can survive even when eaten by animals and stays whole throughout the digestive system, come out
through defecation and seed is now dispersed
Figure 30.3c
Pine seed