22- Reproduction

Question 1

What are the advantages of asexual reproduction in plants?

Answer 1

• Good in stable environments
• Bypasses vulnerable seedling stage
• Doesn’t need pollinators
• Doesn’t waste resources

Question 2

What are the disadvantages of asexual reproduction in plants?

Answer 2

• Lower dispersal of progeny

- Slows down rate of adaptation (problems for large scale agriculture - vulnerability of clones e.g. potato famine)

Question 3

What are the advantages of sexual reproduction in plants?

Answer 3

• Speeds the rate of adaptation
• Purges deleterious mutations
• Adapts to rapidly evolving parasites

Question 4

How did petals evolve in angiosperms from gymnosperms?

Answer 4

Modified stamens

Question 5

How did the male reproductive parts of an angiosperm evolve from gymnosperms?

Answer 5

Leaves with pollen producing organs were modified

Question 6

How did the female reproductive parts of an angiosperm evolve from gymnosperms?

Answer 6

Leaves with ovules were folded in and modified to protect the ovules.

Question 7

In what other ways did flowering plants evolve to make them more economising (expending less energy, more efficient)?

Answer 7

• Having less non-ovular parts - less whorls, no sepals, fewer stamens
• Inflorescences - more ovules per ‘flower’

Question 8

What do the master genes, A, B and C do ?

Answer 8

C = makes carpels
A = makes sepals
B + C = makes stamen
A + B = makes petal

Question 9

What triggers a plant to flower?

Answer 9

Temperature.
At first, plants relied on seasons to determine when they flower, however, this is becoming less dependable.
Plants now rely on changes in day and night to determine when they flower.
Photoperiod - the period of time each day during which an organism receives illumination

Question 10

Where are male gametophytes found?

Answer 10

Within a pollen grain.

Question 11

Where are microsporocytes found?

Answer 11

Within a pollen sac - microsporangium

Question 12

How many microspores are produced from the diploid mother microsporocyte during meiosis (for male gametes)?

Answer 12

4

Question 13

When a pollen grain lands on the sigma and a pollen tube begins to grow, what happens the (now mature) male gametophyte

Answer 13

The nucleus divides through mitosis, forming two sperm.

Question 14

What is the female gametophyte?

Answer 14

The multicellular embryo sac (within an ovule, enclosed in an ovary)

Question 15

How many megaspores are produced from the diploid mother megasporocyte during meiosis (for female gametes)?

Answer 15

4, but only one survives as the megaspore.

Question 16

After the megaspore is formed, it undergoes three mitotic divisions to form what?

Answer 16

The embryo sac

Question 17

Why is it called double fertilisation in plants?

Answer 17

1. The male and female gametes come together to form the embryo
2. The other male gamete fuses to the polar nuclei to form the endosperm (has male and female genetic components)