Lecture Twenty Two - Plant diversity IV Flashcards
How do gymnosperms and angiosperms fit into the plant diversity tree?
Both seed plants.
What feature of plants help them to live on land?
The evolution of the seed frees plants from dependance on an aquatic environment.
Where are spore sacs produced?
On the underside of leaves.
How many generations to seed plants?
Three alternations of generations.
The seed is made up of the components from the three alternations of generations.
What are megaspores and microspores?
Megaspores germinate into a female gamete in ferns.
Microspores (smaller than megaspores) germinate into the male gametes in ferns.
These are heterospores when combined.
The heterospores grow into gametophytes.
Megaspores retained by parent sporophyte.
The sperm is delivered to the eggs via the microspore dispersal.
Embryos disperse via seeds.
What features have seeds evolved to protect the seed?
Integuments - the seed coat.
The seed coat keeps the seed dormant until the conditions are favourable.
What is a sporophyll?
The leaf which produces a/many spore sac(s).
The pistil and stamen both are highly modified sporophylls.
What are fruits?
They are matured pistils of flowers.
Label an angiosperm (flower).
Describe the vascular traces of stamens, sepals and petals.
Stamens are petalled in many basal angiosperms.
Petals usually have a single vascular trace, like stamen, while sepals usually have as many vascular traces as leaves of the same species (often three).
Thus, petals seem to have evolved from sterilised stakes, while sepals evolved directly from leaves.
How is the seed plant life cycle different from other plants?
Sperm is free of water dependance in seed plants (gymnosperms and angiosperms).