Lana West

Mr. Jameson

Honors Biology

11 February 2010

Check and Challenge: Page 332 Questions 1-4

1. Some plants, animals, and fungi can reproduce both sexually and asexually. How

can you explain the fact that many of these organisms tend to switch from asexual

to sexual reproduction under stresses such as starvation?

The plants, animals, and fungi that tend to switch from asexual to sexual

reproduction under stress such as starvation to conserve energy. They do

this because sexual reproduction takes up a lot of energy, and when the

organism is starving, conserving energy as much as possible is a necessity

for survival. This is the reason why they switch to asexual reproduction: it

takes less energy to perform.

2. Distinguish between pollination and fertilization in plants.

Pollination is the placement of pollen by wind or animal onto the stigma

of a carpel, and is a requirement for fertilization. Fertilization is the union

of the nucleus of an ovum, the unfertilized egg, and a sperm nucleus. But

this would not be possible without pollination.

3. Describe the formation and function of the plant embryo, endosperm, seed, and

fruit.

An embryo is an organism in its earliest stages of development. An

embryo is part of a seed. The embryo is made up of precursor tissues for

the leaves, stem, and root. The purpose of the embryo is procreation, or

the starting point of reproduction. An endosperm is a nutrient-rich

structure formed by the union of a sperm cell and a large cell having two

nuclei. Double fertilization is complete when a second sperm cell fertilizes

the egg. The endosperm provides nourishment to the developing embryo

in seeds of flowering plants. A seed is a fertilized ovule. As the seed

grows, other parts of the flower change. The corolla withers and dies. The

ovary swells and changes into a fruit. The seeds are held inside the fruit.

The seeds must now be distributed to new places to grow into new plants.

4. In what ways are flowering plants better equipped than other plants to reproduce

in a wide range of environments?

Flowering plants are better equipped than other plants to reproduce in a

wide range of environments because of their adaptations:

1. The dominance of the diploid stage in the life cycle, which

allows development of complex structures.

2. The evolution of pollen, which allows transfer of sperm from

plant to plant without the need for water.

3. The evolution of the seed, which protects the dormant embryo

and provides food and protection for the young plant.

4. A variety of adaptations that promote pollen and seed dispersal.