Exam 3 chapter 31 cont Flashcards
What feature did land plants evolve in order to cope with dessication and what problem did this feature introduce
Cuticle – the cuticle introduced the problem of being able to get air through the cuticle. The stoma solved this problem. First they were just pores but then evolved guard cells
Why was increased UV radiation a problem for land plants and what was the evolutionary solution
UV radiation damaged DNA.
Flavonoids served as sunscreen that protected them from UV radiation
What were the first land plants that lacked rigidity and grew low to the ground
nonvascular plants
In order to grow erect, a plant must transport water against gravity and stay upright despite gravity and wind. What innovations allowed them to do this
Vascular tissue, tracheids and vessels
In which groups of plants do you see vessel elements
Angiosperms and gnetophytes (these are gymnosperms)
Do green algae practice alternation of generations? Why or why not
No, because they lack two different stages (gametophyte and sporophyte). NO SPOROPHYTES IN GREEN ALGAE
What are the name of the male and female gametes
Antheridium and archegonium
What two important obstacles in green land plants have to overcome to make the water-to-land transition
Gamete dispersal
Lack of motility
What innovations allowed plant reproduction in dry environments
Dessication-resistant spores encased in sporopollenin
Gametes produced in complex, multicellular structure
Embryos retained and nourished by the parent plant
What are gametangia? What living land plant groups still have these
They are specialized reproductive organs that protect gametes from drying and damage. All living land plants EXCEPT angiosperms have these
All land plants undergo alternation of generations. What is alternating
Alternates between a multicellular haploid phase called the gametophyte and a multicellular diploid phase known as the sporophyte
What are the events that are always involved in alternation of generation
- sporophyte produces haploid spores by meiosis
- spores germinate, divide by mitosis, and develop into multicellular, haploid gametophytes
- gametophytes produce unicellular haploid gametes by mitosis
- two gametes unite during fertilization to form a diploid zygote
- the zygote divides by mitosis and develops into multicellar, diploid sporophyte
What do zygotes become? Spores
Zygotes develop into sporophytes and spores are developed into gametophytes
What is produced by fertilization of sperm and egg
zygotes
What does in mean when a certain stage is “dominant” over the other
It is larger and longer lived
In early land plants (nonvascular plants), which stage in the alternation of generations is dominant? Why does this make sense
Gametophyte. This make sense because these evolved from green algae and they didn’t even have a sporophyte stage
In ferns and other vascular plants, which stage is dominant
sporophyte
What might be a reason for transition from a dominant haploid gametophyte stage to a dominant sporophyte stage for plants
Because the sporophyte stage is diploid, therefore you would have a second copy as a backup during bad weather, etc
What is a major difference that separates gymnosperms and angiosperms from earlier plants that has to do with the spores
Early land plants are homosporous, which means that they have a single type of spore that develops into a bisexual gametophyte (produces both egg and sperm) so they can self-fertilize
Gymnosperms and angiosperms have heterospory which is the production of two different spore types by different structures
What is a pollen grain
Tiny mail gametophyte that is surrounded by a tough coat of sporopollenin
Because it has this sporopollenin, they can be exposed to air for long periods of time
What does sporopollenin protect plants against
desiccation
What are the two key reproductive structures of flowers? Which is male and which is female
Stamens (male) and carpels (female)
How is heterospory in angiosperms different than that of gymnosperms
Angiosperms have double fertilization. One fertilization produces embryo and the other produces endosperm to nourish embryo
What selective pressure likely first drove the evolution and diversification of flower sepals, petals, and scents
Attraction of animal pollinators
What do the pollinator and plant each gain through their mutualistic relationship
Pollinator gets food and plant gets fertilized
