Fertilization
Gametes are reproductive cells. They are made during the process called meiosis from cells that have
two sets of chromosomes. Meiosis divides the chromosomes so that only one set ends up in each sperm or egg
cell. Cells with two sets of chromosomes are called diploid cells. Since each species has a different number of
chromosome, the symbol 2n is used to indicate a cell is diploid. Gametes, with only one set of chromosomes,
are called haploid cells. The symbol n is used to indicate a cell is haploid.
Fertilization occurs when an egg cell and a sperm cell combine. The two haploid cells produce one
diploid cell, called a zygote. If the gametes were not haploid, then the fertilized zygote would have four sets of
chromosomes.
True or false, plants reproduce sexually. It’s true! Plants produce both egg and sperm cells. The plants
use the wind, insects, or gravity to carry the sperm to the egg in pollen grains. When a pollen grain lands on the
sticky part of a flower, a special tube grows into the sticky part until it reaches the eggs. Then the sperm swim
down this tube to fertilize the egg. This zygote will begin to grow and eventually become part of a seed.
True or false, all organisms reproduce sexually. It’s false! A few simple organisms reproduce
asexually, by binary fission, budding, or vegetative reproduction. But most organisms reproduce sexually.
Insects, fish, reptiles, amphibians, birds, algae, mammals and many other organisms all produce sperm and eggs
to produce offspring that are not clones of the parents, but slightly different. This variation in offspring is very
important to the survival of the species in a changing environment, something you’ll learn more about later.
Matching – One choice may be used twice.
_____ 1. gametes
a. two sets of chromosomes
_____ 2. meiosis
b. one set of chromosomes
_____ 3. diploid
_____ 5. fertilization
c. reproduction by binary fission, budding,
or vegetative reproduction
d. reproduction by the uniting of a sperm
and an egg cell
e. reproductive cells
_____ 6. zygote
f. the process that makes gametes
_____ 7. asexual reproduction
g. a fertilized egg
_____ 4. haploid
_____ 8. sexual reproduction
True or False
_____ 1.
_____ 2.
_____ 3.
_____ 4.
_____ 5.
_____ 6.
_____ 7.
_____ 8.
_____ 9.
Gametes are sperm and egg cells.
Gametes have two sets of chromosomes.
Gametes have one set of chromosomes.
Gametes are haploid.
Gametes are diploid.
Mitosis is a process that makes gametes.
Meiosis is a process that makes gametes.
Fertilization occurs when one cell divides into two cells.
Fertilization is the process in which diploid cells are made into haploid
gametes.
_____ 10. Fertilization is the process in which a sperm cell and an egg cell unite.
_____ 11.
_____ 12.
_____ 13.
_____ 14.
_____ 15.
A fertilized egg is called a gamete.
A fertilized egg is called a zygote.
A zygote is haploid.
A zygote is diploid.
Plants reproduce sexually.
Fill in the Blank
gametes
diploid
2n
zygote
meiosis
fertilization
pollen
mammals
haploid
n
seed
plants
1. __________________ and _____________________ reproduce sexually.
2. To be able to reproduce this way, these organisms must be able to produce _____________.
3. ____________________ is the process that makes gametes.
4. Most cells are __________________ which means they have two sets of chromosomes.
5. The symbol _________ indicates that a cell is diploid.
6. Meiosis makes diploid cells into ___________ cells, cells with only one set of chromosomes.
7. The symbol ________ indicates that a cell is haploid.
8. When gametes are joined together, a ______________ is formed.
9. The process in which egg and sperm are joined is called _______________________.
10. In plants, the sperm is carried by the wind in ______________ grains.
11. When the pollen lands on the sticky part of a flower, a tube allows the sperm to travel to the eggs, where
fertilization occurs. The zygote will become part of a _______.
Answer the Following
1. What are gametes?
2. What does diploid mean? What symbol is used to indicate that a cell is diploid?
3. What does haploid mean? What symbol is used to indicate that a cell is haploid?
4. Are gametes haploid or diploid?
5. What process makes gametes?
6. What is fertilization?
7. What is a zygote?
8. Is a zygote haploid or diploid?