There are two types of reproduction: sexual reproduction and
Sexual reproduction is the creation off offspring through the
fusion of haploid gametes to form a diploid zygote(fertilised
Asexual reproduction is the reproductive process in which
new individuals are produced without the formation of
Asexual reproduction does not involve the fusion of haploid
SEXUAL REPRODUCTION ASEXUAL REPRODUCTION
The production of new individuals
involving sex cells or gametes
The production of new individuals
without involving sex cells
Gametes are formed by meiotic division. The process relies entirely on mitotic
New individuals inherit genes from both
parents through the fusion of the egg and
New individuals get their genes from one
parent without the fusion of an egg and
Present in humans,other
and flowering plants
Present in simple organisms like the
plants such as mosses and potatoes.
Produces offspring that are genetically
different from their parents
Ensures the survival of the species if the
environmental conditions undergo
Produces offspring that are genetically
identical to the parent
Ensures that the adaptations of the
parent for survival are passed down
unchanged to the offspring
Is an advantage if the environment is
1. In humans,the male gametes called sperms
(spermatozoa) are produced in the male reproductive
organs called testes.
2. The female gametes or ova are produced in the female
reproductive organs known as ovaries.
3. These two types of gametes are produced through the
process of meiosis.The gametes are genetically different
from the parent cell
4. During fertilisation,a sperm fuses with an ovum to form
5. As the sperm and ovum have haploid number of
chromosomes (n=23) each,the zygote formed will have
a diploid number of chromosomes (2n=46).
6. During mitosis,the zygote divides mitotically to produce
millions of cell,each cell having 46 chromosomes.
The male reproductive system consists of:
• Gonads that produce male gametes(sperm cells) and sex hormones.
• Accessory glands that secrete fluids essential to sperm movement
• Ducts that carry the sperms and secretions
• The male reproductivestructures include the
testes,scrotum,epididymis,vas deferens (sperm ducts) and penis.
• The male reproductive system also includes the seminal vesicles
and the prostate gland.
• The male gonads (testes) produce both sperms and male sex
hormones.It is enclosed in an external sac called the scrotum.The
scrotum houses the testes outside the body cavity.Outside the
body,the temperature of the testes is about 2-3°C lower than the
normal body temperature thus it becomes ideal for sperm to
• Each testis has about one thousand seminiferous tubules.These are
fine,long coiled tubes arranged compactly.
• The tubules merge to form a tightly coiled tube called the
epididymis.The epididymis lies just outside the testes.
• Sperms are formed in the seminiferous tubules and mature
within the epididymis.The epididymis is connected to the vas
deferens or sperm duct which also stores the sperms.The vas
deferens leaves the scrotum and enters the abdominal cavity.
• The two sperm duct join the urethra which connects the
bladder to the penis.The sperm pass from the seminiferous
tubules through the epididymis and vas deferens into the
urethra.The urethra is the exit route for both sperm and urine.
• Accessory gland add secretions for the transport and survival
of the sperm:
I. The seminal vesicle secrete thick,clear fluid containing
nutrients for the sperm.
II. The prostate gland secretes a milky white fluid that
activates or increases the mobility of the sperm.The sperm
and the secretions from the accessory glands make up the
• Spermatogenesis (spermatozoa formation) takes place in the
densly coiled seminiferous tubules.
• Two types of cells,the germinal epithelial cells and Sertoli
cells,line the seminiferous tubules.
• The Sperm cell consists of head,midpiece and a tail.The head
contains a large nucleus and a specialised lysosome called the
• The acrosome contains hydrolytic enzymes that help to digest
the protective layers surrounding an ovum an help it to
penetrate it during fertilisation.
• The midpiece contains a large number of mitochondria which
helps to provide energy needed for the movement of the tail.
A section of testis showing the seminiferous tubules,epididymis
and vas deferens.
1)Geminal epithelial cells of
a seminiferous tubule divide
by mitosis to produce diploid
grow to become primary
spermatocytes which are
large diploid cells.
3)Each primary spermatocyte
undergoes meiosis I to form two
haploid secondary spermatocytes.
4)Each secondary spermatocyte
divides again during meiosis II to
produce two spermatids.This means a
total four spermatids are formed for
each primary spermatocyte.
5)The spermatids obtain nourishment
from nearby nutritive cells (Sertoli
cells),develop tails and mature into
spermas (spermatozoa) through cell
• The female reproductive system consists of a pair of ovaries,the
Fallopian tubes (oviducts),uterus,cervix,vagina and the external
genital organs which are collectively called the vulva.
• The female gonads or the ovaries produce female gametes (ova)
and secrete female sex hormones :,oestrogen and progesterone
• The Fallopian tubes extend from the ovaries to the uterus.They
have finger-like projections called fimbriae which surround the
ovaries.The combined action of the fimbriae and the beating of cilia
that line the oviducts create a beating of cilia that line the oviducts
create a current that sweeps the ovum along.
• The uterus is a thick-walled,muscular organ that houses the
developing embryo and foetus.
• The ovum in females is produced through oogenesis..
What is Oogenesis??
Oogenesis is the formation of ovum or egg,starts in the
ovary of the female foetus before birth.
How it occurs??
The germinal epithelial cells near the surface of an ovary
multiply by mitosis to form diploid oogonia
The oogonia grow to form primary oocytes (2n)
Each primary oocyte is surrounded by a layer of follicle cells
that nourish the developing oocyte and secrete female
hormones.The primary oocyte and these accessory cells
make up a primary follicle.
As foetal development continues,all primary oocytes
undergo meiosis but stop at prophase I of meiosis I.
The secondary oocyte starts meiosis II which
progresses until metaphase II.The first polar body
may also complete meiosis II to form two polar
At this stage,the secondary oocyte,together with
the layers of follicle cells around it,is now called a
The secondary oocyte starts to grow in the
follicle.The secondary follicle increases in size ad
mature to form Grafiaan follicle.
Later the ovarian wall and the Grafiann follicle
then rupture,releasing the secondary oocyte or
egg into the Fallopian tube.
1)The germinal epithelial cells
divide repeatedly until many
diploid oogonia are formed.
2. The oogonia grow to form
primary oocytes that surrounded
by a layer of follicle cells.
3)The oocytes undergoes the
first meiotic division to become
a secondary oocyte and a first
4)The follicle cells surrounding
the primary focille develop
into the secondary follicle.
The follicle layer of the secondary oocyte thickens and folds to
form the Graafian follicle
5. The secondary oocytes that has complete meiosis II when
it is fertilized by a sperm(n).The final product of meiosis II is the
ovum and the seond polar body
Similarities & Differences between
Spermatogenesis and Oogenesis
Both processes occur in the reproductive organs.
Both involve the process of meiosis.
Both produce haploid gametes that are involved in fertilisation
ASPECT SPERMATOGENESIS OOGENESIS
Site of process In the testes In the ovaries
Cells produced Sperm Ova or egg.
Size of cells Small Big
Consist of the head , middle
pieces and tail
Four funcional cells One funcional cells and
three non-funcional polar
The differences between
spermatogenesis and oogenesis
ASPECT SPERMATOGENESIS OOGENSIS
Meiosis Occurs continuously
Not continues. Stops at
meiosis I. Meiosis II occurs
only if sperm penetrates the
Many mitochondria, less
Fewer mitochondria, more
Infinite number of cells can
Limited number of cells can