Exam 3 chapter 31 cont

Question 1

What feature did land plants evolve in order to cope with dessication and what problem did this feature introduce

Answer 1

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

Question 2

Why was increased UV radiation a problem for land plants and what was the evolutionary solution

Answer 2

UV radiation damaged DNA.

Flavonoids served as sunscreen that protected them from UV radiation

Question 3

What were the first land plants that lacked rigidity and grew low to the ground

Answer 3

nonvascular plants

Question 4

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

Answer 4

Vascular tissue, tracheids and vessels

Question 5

In which groups of plants do you see vessel elements

Answer 5

Angiosperms and gnetophytes (these are gymnosperms)

Question 6

Do green algae practice alternation of generations? Why or why not

Answer 6

No, because they lack two different stages (gametophyte and sporophyte). NO SPOROPHYTES IN GREEN ALGAE

Question 7

What are the name of the male and female gametes

Answer 7

Antheridium and archegonium

Question 8

What two important obstacles in green land plants have to overcome to make the water-to-land transition

Answer 8

Gamete dispersal

Lack of motility

Question 9

What innovations allowed plant reproduction in dry environments

Answer 9

Dessication-resistant spores encased in sporopollenin
Gametes produced in complex, multicellular structure
Embryos retained and nourished by the parent plant

Question 10

What are gametangia? What living land plant groups still have these

Answer 10

They are specialized reproductive organs that protect gametes from drying and damage. All living land plants EXCEPT angiosperms have these

Question 11

All land plants undergo alternation of generations. What is alternating

Answer 11

Alternates between a multicellular haploid phase called the gametophyte and a multicellular diploid phase known as the sporophyte

Question 12

What are the events that are always involved in alternation of generation

Answer 12

• 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

Question 13

What do zygotes become? Spores

Answer 13

Zygotes develop into sporophytes and spores are developed into gametophytes

Question 14

What is produced by fertilization of sperm and egg

Answer 14

zygotes

Question 15

What does in mean when a certain stage is “dominant” over the other

Answer 15

It is larger and longer lived

Question 16

In early land plants (nonvascular plants), which stage in the alternation of generations is dominant? Why does this make sense

Answer 16

Gametophyte. This make sense because these evolved from green algae and they didn’t even have a sporophyte stage

Question 17

In ferns and other vascular plants, which stage is dominant

Answer 17

sporophyte

Question 18

What might be a reason for transition from a dominant haploid gametophyte stage to a dominant sporophyte stage for plants

Answer 18

Because the sporophyte stage is diploid, therefore you would have a second copy as a backup during bad weather, etc

Question 19

What is a major difference that separates gymnosperms and angiosperms from earlier plants that has to do with the spores

Answer 19

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

Question 20

What is a pollen grain

Answer 20

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

Question 21

What does sporopollenin protect plants against

Answer 21

desiccation

Question 22

What are the two key reproductive structures of flowers? Which is male and which is female

Answer 22

Stamens (male) and carpels (female)

Question 23

How is heterospory in angiosperms different than that of gymnosperms

Answer 23

Angiosperms have double fertilization. One fertilization produces embryo and the other produces endosperm to nourish embryo

Question 24

What selective pressure likely first drove the evolution and diversification of flower sepals, petals, and scents

Answer 24

Attraction of animal pollinators

Question 25

What do the pollinator and plant each gain through their mutualistic relationship

Answer 25

Pollinator gets food and plant gets fertilized