Chapter 30: The Evolution Of Seed Plants Flashcards
As we reduce the role of the gametophyte, we reduce the dependency on _______.
water
What are microspores?
Spores that give rise to male gametophytes
What are megaspores?
Spores that give rise to female gametophytes
What 4 features are common to all seed plants?
- Reduced gametophytes
- Heterosporous
- Ovules
- Pollen
What is a gymnosperm?
A vascular plant in which the seeds are not enclosed by a protective fruit or flower
What is the evolutionary advantage of seeds?
- They are multicellular
- Have a protective seed coat and their own food supply
- Allows them to be protected and remain dormant for years, whereas spores have a shorter lifetime.
List the phylum of gymnosperms
- Cycadophyta
- Gingkophyta
- Gnetophyta
- Coniferophyta
What are the characteristics of the Phylum Cycadophyta?
- Look like palms but aren’t
- Large cones
- Tall unbranched trunks
- Crown of pinnately divided leaves
- Flagellated Sperm
- Thrived during Mesozoic era
What are the characteristics of the Phylum Gingkophyta?
- Fan shaped leaves
- Flagellated sperm
- Hair like veins branch dichotomously (one branches into two)
- Deciduous (sheds annually)
- Dioecious (m/f reproductive parts on separate trees)
Only one species remaining - Gingko biloba
Which gymnosperm has a seed coat with a nauseating odor?
Phylum Gingkophyta
What are the characteristics of the Phylum Gnetophyta?
Gnetum:
- leaves look similar to leaves on flower stems
- seeds look like fruits but aren’t
Ephedra:
- drought tolerant shrub
- cluster of ovulate cones
Welwitschia:
- plant only produces two massive leaves
- strobili in the center
- can live for thousands of years
What are the characteristics of the Phylum Coniferophyta?
- largest of the gymnosperms
- big trees, most are evergreens
- do photosynthesis all year round
- don’t shed their leaves
What phylum does the giant sequoia belong to?
Phylum Coniferophyta
Who’s the oldest tree?
Methuselah
What are 3 key features of the gymnosperm life cycle?
- dominance of the sporophyte generation
- development of seeds from fertilized ovules
- transfer of sperm to ovules by pollen
Explain the life cycle of a pine (gymnosperms)
- Conifer species have ovulate cones and pollen cones
- Microspores develop into pollen grains from the pollen cones and enter the integument of the ovule
- Meiosis occurs and female gametophyte develops
- Sperm fertilizes the egg (2n)
- The seed will grow and produce a sporophyte which develops into a tree
Explain how a gymnosperm’s egg is fertilized.
- The ovule of a cone consists of a fleshy megasporangium (which holds a megaspore) and is surrounded by a protective layer called an integument
- There is an opening in the integument called a micropyle where a pollen grain enters
- While the megaspore is developing, 4 haploid cells are produced and 1 survives.
- The megaspore develops into a female gametophyte that contains eggs
- The pollen grain (containing a male gametophyte) extends a tube to the female gametophyte, releasing its sperm to fertilize it.
- The fertilized egg now develops into a seed. The megasporangium dries out and collapses and in replace there is a food supply that surrounds the seed. A spore wall surrounds the food supply and a seed coat (originally the integument) surrounds everything.
What is an angiosperm?
A flowering, vascular plant in which the seeds are enclosed by a protective fruit or flower