Animals expend a considerable amount of energy and time on reproduction. After all,
reproduction ensures that the animal's genes are passed on to the next generation. The life cycle
of any particular animal comes to an end, but its genes can be perpetuated as long as
reproduction has taken place.
Usually animals practice sexual reproduction, which involves sex cells (gametes). The gametes
may be specialized as eggs (oocytes) or sperm (spermatocytes), and even if egg and sperm are
produced by the same individual, animals usually practice cross-fertilization. When animals
reproduce sexually, an offspring inherits half its genes from one parent and the other half from
the other parent. Therefore, an offspring has a different combination of genes than either parent.
In this way, variation is introduced and maintained. Such variation is an advantage to the species
if the environment is changing, because an offspring might be better adapted to the new
environment than is either parent.
Animals usually produce gametes in specialized organs called gonads. The gonads are testes for
the production of sperm and ovaries for the production of eggs. These gametes are produced by
germ cells, cells set aside early in development for this specific purpose. The other cells in a
gonad support and nourish the developing gametes or produce hormones necessary to the
reproductive process. Copulation is sexual union to facilitate the reception of sperm by a female.
In terrestrial animals, males typically have a penis for depositing sperm into the vagina of
females.
When gametes mature the cell divides two times. The first division of the gametes provides two
new cells that have the whole set of chromosomes. This is known as mitosis. The second division
is known as meiosis. Meiosis only occurs in reproductive cells, unlike mitosis which occurs in all
cells. The second time the gametes divide they form four gametes with only half of the
chromosomes that a regular cell contains.
Human cells typically contain 46 chromosomes; however, in gametes there are only 23
chromosomes. Then when a sperm gamete and an egg gamete combine to form the zygote, or
fertilized egg, it has a total of 46 chromosomes. After fertilization, the zygote continues to divide
by mitosis developing into a human baby.
These 46 chromosomes determine the characteristics of the offspring such as eye color and skin
color. Gender is also determined by the chromosomes. Males have one X chromosome and one
Y chromosome; whereas, females have two X chromosomes. Therefore the gender of a couple’s
offspring is determined by the father’s sperm cell (whether the offspring receives an X or Y
chromosome from the sperm cell).
Problem Set 1:
,1. What is the general term used to describe animal sex cells? What are the specific male and
female sex cells called?
sex cells are the gametes, males are (sperm) sprematocytes, females are (eggs) oocytes
2. How does it happen that an offspring has a different combination of genes than either parent?
When a male and a female reproduce sexually, an offspring is form and inherits a set of genes
from the mom and a set of genes from the dad. This results in a different combination of genes
than the parents.
3. What advantage is produced by an offspring having a different combination of genes than
either parent?
As a result of the offspring having different combination of genes than their parents, variation is
introduced and maintained. This gives the offspring an advantage if the environment is changing
because an offspring will be better adapted to the new environment than the parents.
4. What is the general term used to describe the organs in which gametes are produced? What are
the names of the specific male and female gamete producing organs?
The production of gametes are in specialized organs called the gonads. The gonads are testes for
the produciton of sperm and ovaries for the production of eggs.
5. List 2 functions carried out by the cells other than germ cells in gamete producing organs.
The other cells in a gonad function to support and nourish the developing gametes or provide the
necessary hormones for the reproductive process.
6. What is the general term used to describe the process of sexual union and what male and
female organs are involved in this process?
Copulation, is the sexual union to house the reception (the welcoming) of sperm by a female. In
animals males have their penis for depositing sperm into the female's vagina.
7. Division of human cells by mitosis produces cells which have how many chromosomes?
Division of human cells by mitosis produces two new cells that have 46 chromosomes.
8. Division of human sex cells by meiosis produces how many cells containing how many
chromosomes in each?
Division of human sex cells by meiosis results in four gametes with 23 chromosomes each.
9. What is the name of the cell produced by union of human egg and a sperm cells and how
many chromosomes does it possess?
,An egg gamete and a sperm gamete combine to form a zyote which has 46 chromosomes.
10. After human egg and sperm cells combine, by what process does the offspring grow in size?
After fertilization take place, the zygote continues to divide by mitosis developing into a human
body.
11. List three characteristics of offspring determined by chromosomes.
The chromosomes determine the characteristics of the offspring such as: eye color, skin color,
hair color and gender.
12. How many chromosomes of what type are possessed by a female and a male?
Males have: XY
Females have: XX
13. Gender is determined by which parent's sex cell?
Gender of the offspring is determined by the father's sperm cell, if the offspring receives an X or
a Y chromosomes from the sperm cell
Female Reproductive System
The female reproductive system (below) includes internal organs: the ovaries, the oviducts
(fallopian or uterine tubes), the uterus, and the vagina as well as external genitalia collectively
known as the vulva. The female reproductive system has more functions than the male’s. It must
produce eggs and estrogen as well as be the site for the development of a baby after fertilization
of an egg occurs.
, The ovaries are the main reproductive organ in females. The ovaries are two glands that are
almond shaped. One ovary is on each side of the uterus, below the uterine tubes. The ovaries are
held in place by the suspensory, ovarian, and broad ligaments. The suspensory ligaments attach
the ovaries to the pelvis wall. The ovarian ligaments attach the ovaries to the uterus. The broad
ligaments hold the ovaries in place in the pelvis.
Inside each ovary are ovarian follicles which each hold an immature egg. Ovulation, or release of
a mature egg, occurs approximately every 28 days. The ovarian follicle becomes the corpus
luteum after ovulation. The corpus luteum helps maintain pregnancy if an egg is fertilized; if not,
it disintegrates.
The female reproductive system also contains a duct system like males. The duct system includes
the oviducts, uterus, and vagina. The oviducts, also called uterine or fallopian tubes, extend from
the ovaries to the uterus. Each tube has three sections: infundibulum, ampulla and isthmus and
three coats: the outer serous coat, the middle muscular coat, and an inner mucosa coat.
The fallopian tube functions include capturing an egg from the ovary at the time of ovulation;
nourishing the fertilized egg or zygote during its early cell divisions; and delivering the
developing embryo into the uterine cavity when it is time for implantation. The different parts of
the fallopian tube correspond to these various functions.
The oviducts are not connected to the ovaries but have fingerlike projections called fimbriae on
the infundibulum end of the tube furthest from the uterus. When an egg (oocyte) bursts from
follicle within an ovary during ovulation, it is most often swept into an oviduct by the combined
action of the fimbriae and the beating of the cilia that line the oviducts. The egg is quickly
moved into the ampulla region of the tube where it is most often fertilized. The mucosa layer of
the ampulla provides nourishing fluid that allows repeated cell divisions. Over the next several
days, the combination of muscular contractions and cilia move the egg through the isthmus
toward the uterus. When the dividing egg (zygote) reaches the stage (blastocyst) where the outer
membrane dissolves, it is delivered into the uterus.
The uterus is a hollow, thick-walled muscular organ shaped like an inverted pear connecting the
uterine tubes and the vagina and in a forward-tilted position between the bladder and the rectum.
reproduction ensures that the animal's genes are passed on to the next generation. The life cycle
of any particular animal comes to an end, but its genes can be perpetuated as long as
reproduction has taken place.
Usually animals practice sexual reproduction, which involves sex cells (gametes). The gametes
may be specialized as eggs (oocytes) or sperm (spermatocytes), and even if egg and sperm are
produced by the same individual, animals usually practice cross-fertilization. When animals
reproduce sexually, an offspring inherits half its genes from one parent and the other half from
the other parent. Therefore, an offspring has a different combination of genes than either parent.
In this way, variation is introduced and maintained. Such variation is an advantage to the species
if the environment is changing, because an offspring might be better adapted to the new
environment than is either parent.
Animals usually produce gametes in specialized organs called gonads. The gonads are testes for
the production of sperm and ovaries for the production of eggs. These gametes are produced by
germ cells, cells set aside early in development for this specific purpose. The other cells in a
gonad support and nourish the developing gametes or produce hormones necessary to the
reproductive process. Copulation is sexual union to facilitate the reception of sperm by a female.
In terrestrial animals, males typically have a penis for depositing sperm into the vagina of
females.
When gametes mature the cell divides two times. The first division of the gametes provides two
new cells that have the whole set of chromosomes. This is known as mitosis. The second division
is known as meiosis. Meiosis only occurs in reproductive cells, unlike mitosis which occurs in all
cells. The second time the gametes divide they form four gametes with only half of the
chromosomes that a regular cell contains.
Human cells typically contain 46 chromosomes; however, in gametes there are only 23
chromosomes. Then when a sperm gamete and an egg gamete combine to form the zygote, or
fertilized egg, it has a total of 46 chromosomes. After fertilization, the zygote continues to divide
by mitosis developing into a human baby.
These 46 chromosomes determine the characteristics of the offspring such as eye color and skin
color. Gender is also determined by the chromosomes. Males have one X chromosome and one
Y chromosome; whereas, females have two X chromosomes. Therefore the gender of a couple’s
offspring is determined by the father’s sperm cell (whether the offspring receives an X or Y
chromosome from the sperm cell).
Problem Set 1:
,1. What is the general term used to describe animal sex cells? What are the specific male and
female sex cells called?
sex cells are the gametes, males are (sperm) sprematocytes, females are (eggs) oocytes
2. How does it happen that an offspring has a different combination of genes than either parent?
When a male and a female reproduce sexually, an offspring is form and inherits a set of genes
from the mom and a set of genes from the dad. This results in a different combination of genes
than the parents.
3. What advantage is produced by an offspring having a different combination of genes than
either parent?
As a result of the offspring having different combination of genes than their parents, variation is
introduced and maintained. This gives the offspring an advantage if the environment is changing
because an offspring will be better adapted to the new environment than the parents.
4. What is the general term used to describe the organs in which gametes are produced? What are
the names of the specific male and female gamete producing organs?
The production of gametes are in specialized organs called the gonads. The gonads are testes for
the produciton of sperm and ovaries for the production of eggs.
5. List 2 functions carried out by the cells other than germ cells in gamete producing organs.
The other cells in a gonad function to support and nourish the developing gametes or provide the
necessary hormones for the reproductive process.
6. What is the general term used to describe the process of sexual union and what male and
female organs are involved in this process?
Copulation, is the sexual union to house the reception (the welcoming) of sperm by a female. In
animals males have their penis for depositing sperm into the female's vagina.
7. Division of human cells by mitosis produces cells which have how many chromosomes?
Division of human cells by mitosis produces two new cells that have 46 chromosomes.
8. Division of human sex cells by meiosis produces how many cells containing how many
chromosomes in each?
Division of human sex cells by meiosis results in four gametes with 23 chromosomes each.
9. What is the name of the cell produced by union of human egg and a sperm cells and how
many chromosomes does it possess?
,An egg gamete and a sperm gamete combine to form a zyote which has 46 chromosomes.
10. After human egg and sperm cells combine, by what process does the offspring grow in size?
After fertilization take place, the zygote continues to divide by mitosis developing into a human
body.
11. List three characteristics of offspring determined by chromosomes.
The chromosomes determine the characteristics of the offspring such as: eye color, skin color,
hair color and gender.
12. How many chromosomes of what type are possessed by a female and a male?
Males have: XY
Females have: XX
13. Gender is determined by which parent's sex cell?
Gender of the offspring is determined by the father's sperm cell, if the offspring receives an X or
a Y chromosomes from the sperm cell
Female Reproductive System
The female reproductive system (below) includes internal organs: the ovaries, the oviducts
(fallopian or uterine tubes), the uterus, and the vagina as well as external genitalia collectively
known as the vulva. The female reproductive system has more functions than the male’s. It must
produce eggs and estrogen as well as be the site for the development of a baby after fertilization
of an egg occurs.
, The ovaries are the main reproductive organ in females. The ovaries are two glands that are
almond shaped. One ovary is on each side of the uterus, below the uterine tubes. The ovaries are
held in place by the suspensory, ovarian, and broad ligaments. The suspensory ligaments attach
the ovaries to the pelvis wall. The ovarian ligaments attach the ovaries to the uterus. The broad
ligaments hold the ovaries in place in the pelvis.
Inside each ovary are ovarian follicles which each hold an immature egg. Ovulation, or release of
a mature egg, occurs approximately every 28 days. The ovarian follicle becomes the corpus
luteum after ovulation. The corpus luteum helps maintain pregnancy if an egg is fertilized; if not,
it disintegrates.
The female reproductive system also contains a duct system like males. The duct system includes
the oviducts, uterus, and vagina. The oviducts, also called uterine or fallopian tubes, extend from
the ovaries to the uterus. Each tube has three sections: infundibulum, ampulla and isthmus and
three coats: the outer serous coat, the middle muscular coat, and an inner mucosa coat.
The fallopian tube functions include capturing an egg from the ovary at the time of ovulation;
nourishing the fertilized egg or zygote during its early cell divisions; and delivering the
developing embryo into the uterine cavity when it is time for implantation. The different parts of
the fallopian tube correspond to these various functions.
The oviducts are not connected to the ovaries but have fingerlike projections called fimbriae on
the infundibulum end of the tube furthest from the uterus. When an egg (oocyte) bursts from
follicle within an ovary during ovulation, it is most often swept into an oviduct by the combined
action of the fimbriae and the beating of the cilia that line the oviducts. The egg is quickly
moved into the ampulla region of the tube where it is most often fertilized. The mucosa layer of
the ampulla provides nourishing fluid that allows repeated cell divisions. Over the next several
days, the combination of muscular contractions and cilia move the egg through the isthmus
toward the uterus. When the dividing egg (zygote) reaches the stage (blastocyst) where the outer
membrane dissolves, it is delivered into the uterus.
The uterus is a hollow, thick-walled muscular organ shaped like an inverted pear connecting the
uterine tubes and the vagina and in a forward-tilted position between the bladder and the rectum.
