chapter twenty three: developing of gametes

Question 1

three steps in sperm formation

Answer 1

1. mature sporophyte produces flowers with anthers
2. each microspore mother cell divides by meiosis; gives rise to four haploid microspores
3. microspores divide by mitosis; gives rise to microgametophytes (pollen grains)

Question 2

pollen grains contain ___ and ___

Answer 2

1 tube cell (vegetative, not reproductive)
1 generative cell

Question 3

4 steps of egg formation

Answer 3

1. mature sporophyte produces flowers with ovules
2. megaspore mother cell divides by meiosis; gives rise to 4 haploid megaspores
3. three megaspores degenerate, one persists and enlarges
4. enlarged megaspore undergoes 3 mitotic divisions; gives rise to megagametophyte

Question 4

the mature megagametophyte consists of ___ haploid nuclei and ___ cells

Answer 4

8
7

Question 5

cells contained in a megagametophyte

Answer 5

1. central cell with two separate haploid nuclei that do not fuse
2. 1 egg
3. 5 support cells that will degenerate

Question 6

two types of support cells in a megagametophyte

Answer 6

two synergids
three antipodals

Question 7

synergids function to ___

Answer 7

guide pollen tube toward the egg

Question 8

antipodals function to ___

Answer 8

help with embryo nutrition

Question 9

flowers that are usually large, greenish, odorless, and produce a large quantity of pollen

Answer 9

wind-pollinated flowers

Question 10

examples of wind pollinated flowers

Answer 10

oak, cottonwood, ragweed, grasses

Question 11

flowers that are usually large, colored, scented, and produce nectar

Answer 11

animal-pollinated flowers

Question 12

most ___ are animal-pollinated

Answer 12

angiosperms

Question 13

examples of animal pollinators

Answer 13

honeybees, hummingbirds, bats, moths, butterflies

Question 14

how many fertilization events do plants require

Answer 14

two

Question 15

four steps of pollination and fertilization

Answer 15

1. pollen lands on the stigma of its same species
2. pollen tube grows down the style to the ovary
3. two sperm cells descend to pollen tube
4. one sperm fertilizes the egg to form a zygote (2n); the other sperm fertilizes the polar nuclei to form the endosperm (3n)

Question 16

after fertilization, the zygote divides to form the ___

Answer 16

embryo

Question 17

dicot embryos form ___ cotyledons

Answer 17

two

Question 18

cotyledons absorb the ___

Answer 18

endosperm

Question 19

monocot embryos form ___ cotyledon

Answer 19

one

Question 20

seed consists of a ___, ___, and ___

Answer 20

embryo, food source (endosperm), and a seed coat

Question 21

mature seeds enter a period of ___ which allows time for a plant to ___ seeds and allows seeds to postpone ___ until environmental conditions are favorable

Answer 21

dormancy
disperse
germination