Chapter 30: Evolution of seed plants

Question 1

When was the origin of seed plants?

Answer 1

approx. 360 million years ago

Question 2

What 3 things does a seed compose of?

Answer 2

1. embryo
2. food/nutrients
3. protective coat

Question 3

What are 4 common features to all seed plants?

Answer 3

1. Reduced gametophytes (in size)
2. Heterospory
3. Ovules
4. Pollen

Question 4

What is one advantage of reduced gametophyte size?

Answer 4

• it provides protection from environmental stresses and it protects from UV radiation and drying out

Question 5

What are 2 types of spores that seed plants produce?

Answer 5

1. Megasporangia (female part) –> megaspores –> female gametophytes –> egg
2. Microsporangia (male part) –> microspores –> male gametophytes –> pollen/sperm

Question 6

What is the name of the layer of sporophyte tissue that protects the megasporangium?

Answer 6

Integument

Question 7

What 3 things does an ovule consist of?

Answer 7

megasporangium, megaspore and integument

Question 8

What does a pollen grain consist of? and what develops the pollen grain?

Answer 8

The microspore develops into a pollen grain.

Pollen grain consists of a wall of pollen and male gametophyte

Question 9

What is pollination?

Answer 9

transfer of pollen to the ovules of another plant

Question 10

How does the sperm travel to the egg? What is an advantage of that?

Answer 10

through a pollen tube. That way, the plants don’t have to live in moist environments

Question 11

Describe the alternation of generation of Gymnosperms (pine trees) in 9 steps

Answer 11

1. The ovulate and pollen cones appear on the same tree
2. Microsporophytes divide by meiosis and produce haploid microspores.
3. A microspore develops into a pollen grain (and has male gametophyte and pollen wall).
4. Pollination occurs when pollen grain reaches ovule of female cone
5. pollen grain germinates forming a pollen tube that makes its way through megasporangium
6. while pollen tube is developing, the megasporocyte is undergoing meiosis, producing 4 haploid cells and one survives as a megaspore
7. megaspore develops into female gametophyte that contains 2-3 archegonia where eggs form
8. by the time eggs mature, 2 sperm cells develop in pollen tube and go to female gametophyte
9. fertilization occurs more than a year after pollination and zygote develops into embryo. The ovule becomes a seed.

Question 12

What is the difference between gymnosperms and angiosperms?

Answer 12

gymnosperms include pine trees, their seeds are not enclosed in an ovule. Also, they do not flower

angiosperms have their seeds enclosed in an ovule, and they are flowering plants

Question 13

What 3 structures does the female part of angiosperms (carpel) consist of?

Answer 13

1. Stigma (where pollen attaches)
2. Style (where pollen tube goes down)
3. Ovary (where eggs are produced)

Question 14

What 2 structures does the male part of angiosperms (stamen) consist of?

Answer 14

1. Anther (produces pollen)

2. Filament

Question 15

What are fruits?

Answer 15

they consist of a mature ovary, and thickening of ovary walls.
In pea pods, the pea is the mature ovules and the pod is the ovary

Question 16

Describe the 8 steps of angiosperm alternation of generation?

Answer 16

1. On the anther, each microsporangium contains microsporocytes that divide via meiosis to produce microspores
2. A microspore develops into a pollen grain
3. The generative cell of gametophyte divides forming 2 sperm and a pollen tube is formed
4. Megasporangium on each ovule, contain megasporocytes that divide by meiosis to produce 4 megaspores –> 1 survives and forms female gametophyte
5. After pollination, 2 sperm cells discharge into each ovule
6. Double fertilization occurs: when one sperm fertilizes the egg forming a zygote and the other sperm fertilizes the central cell forming endosperm (food supply for the zygote) n–> 3n
7. Zygote develops into embryo thats packaged with food
8. When germinates, the embryo develops into mature sporophyte.

Question 17

Seed plants are _______ dominant

Answer 17

sporophyte

Question 18

The gametophyte is _______ on the sporophyte in seed plants

Answer 18

dependent

Question 19

What are the advantages and disadvantages for being gametophyte dependent on sporophyte?

Answer 19

Gains: nourished and protected by sporophyte
losses: more stress on sporophyte and more energy used to keep embryo nourished

Question 20

What are the advantages and disadvantages of pollen? (male gametophytes)

Answer 20

Gains: male gametophytes are protected by pollen grain and water is not necessary for fertilization
Loss: Needs some mechanism to carry pollen around (air, insects…etc..)

Question 21

What are the advantages and disadvantages of ovule? (female gametophytes)

Answer 21

Gains: protected by sporophyte (non-motile)
Losses: extra care for sporophyte

Question 22

What are the advantages and disadvantages of seeds? (fertilized ovules that contain the next generation sporophyte?)

Answer 22

Gain: protection, dispersal, food storage, dormancy
Loss: great energy cost to plant

Question 23

What is the main method of spore dispersal in gymnosperms?

Answer 23

Pollination by wind

Question 24

What are 4 extant phyla of gymnosperms? Briefly describe them

Answer 24

1. GInkophyta (has one extant species called ginkgo biloba)
2. Phylum Cycadophyta (large cones and look like palm trees)
3. Phylum Gnetophyta (they all look morphologically different and live in different parts of the world)
4. Phylum Coniferophyta (most common species of gymnosperms and they have scale like leaves, long needs or flat leaves. They are mostly evergreen and can survive in extreme coldness)

Question 25

What phylum makes up angiosperm?

Answer 25

Anthophyta

Question 26

What is the difference between monoecious flowers and dioecious flowers?

Answer 26

Monoecious flowers have male and female flowers on the same individual plant
Dioecious flowers have male and female flowers on different individual plants

Question 27

What are 3 Adaptive advantages to angio sperm-style fertilization

Answer 27

1. Food store for seed (endosperm) develops only after fertilization, so that the plant does not spend lifetime making food for the seed
2. Female gametophyte reduced in size and therefore cheaper to produce
3. Production of small female gametophyte takes only a few days rather than months

Question 28

How many percent of the human caloric intake comes from land plants?

Answer 28

about 80%