NOTA BIOLOGY SEM1 2021_2022

2) Present of origin of replication/ ori.
3) Able to replicate freely in the host cell.
4) Has selectable marker gene/ ampR/ lacZ.
5) Able to express cloned genes.
6) They are easy to be selected.
7) Have two or more restriction sites/ multiple cloning sites/ unique restriction sites.
8) E.g. Plasmid/bacteriophage /cosmid

Genetic Marker - A gene or DNA sequence with a known location.
Common genetic markers are:

1. Genes coding for resistance to antibiotics
- ampR ~ resistant to antibiotic ampicillin
- tetR ~ resistant to antibiotic tetracycline

2. lacZ gene - coding for enzyme ß–galactosidase
- ß–galactosidase is an enzyme which can hydrolyses
lactose.

No Types of Vectors Diagram

1 Plasmid

i) Small rings/circular chromosome double stranded
DNA molecules that carry genes separate from the
main bacterial chromosome.
ii) A structure in bacterial cells consisting of DNA that
can exist & replicate independently of the
chromosome.
iii) They can be transferred from cell to cell in a
bacterial colony.
iv) Can carry 10-15 kilo base (kb) pairs.

2 Bacteriophage

i) Useful as cloning vector because its molecular
genetics is well known & DNA can be efficiently
packaged in phage particles, which can be used to
infect suitable host.
ii) Can carry 25 kilo base (kb) pairs

3 Cosmid

i) A hybrid vector that used for gene cloning, a hybrid of
plasmid & the cos gene.
ii) Can carry 44 kilo base (kb) pairs

4 Yeast Artificial Chromosome (YAC)

i) Modified plasmid used for cloning large segments
of DNA in yeast cell.

ii) YAC can carry a much longer DNA segment than
can a plasmid vector, a cloned fragment is more
likely to contain an entire gene rather than just a
portion of it

ii) Can carry 500 kilo base (kb) pairs

e) Explain the characteristics of E. coli as host cell (bacteria) and its characteristics. (CLO 3)

Host cell
- Cells in which recombinant DNA can be replicated or recombinant protein can be produced.
- The most commonly used host organism is the bacterium Escherichia coli.
- Other organism that can be used as hosts include yeast cells.
Characteristics of hosts cells
1) Able to receive recombinant DNA/ plasmid through the transformation process.
2) Able to maintain the structure of the recombinant DNA / plasmid from one generation to another.
3) Able to express the gene product of the recombinant DNA/ plasmid.
4) Able to produce large quantities/ amplify the recombinant DNA.

f) Explain modifying enzyme and its function: (CLO3)
i. DNA ligase for DNA ligation
ii. Taq polymerase for DNA amplification using PCR

• Modifying enzyme - enzyme use in modifying the DNA strand.
• DNA ligase which is used to join fragments of DNA by catalyzes the formation of phosphodiester

bonds between adjacent nucleotides in a DNA molecule. This process is called DNA ligation.
• Taq polymerase is used for DNA amplification using PCR.
• By using restriction enzymes & modifying enzyme, genetic engineers are able to cut & recombine any two

DNA molecules from different species

• E.g: cleave with EcoRI and ligate using DNA
ligase.

• Taq polymerase for DNA amplification using PCR

8.2 METHODS IN GENE CLONING

a) Overview using diagram to show the steps in gene cloning by using plasmid (CLO 1)
Gene Cloning - The production of exact copies (clones) of a particular gene using genetic engineering
techniques.

b) Describe the steps in gene cloning by using plasmid as the vector (CLO 3):
Isolation of gene, Cleave/cut, Insertion, Transformation and amplification, Screening (blue/white
screening)

- Steps in gene cloning by using plasmid as a vector:
Step 1: Isolation of gene
Step 2: Cleave
Step 3: Insertion
Step 4: Transformation and amplification
Step 5: Screening

Name of Steps Procedure & Illustrations
i) Isolate plasmid as cloning vector from bacterial cells.
1) Step 1: Isolation of gene ii) Isolate foreign DNA that containing gene of interest from donor cell
(example gene for insulin from human cells).
(Isolation of plasmid & DNA
that contain gene of interest)

2) Step 2: Cleave/ cut i) Isolated bacterial plasmids & foreign DNA are cleaved with same
restriction enzyme. (E.g.: EcoRI)
iii) Producing compatible ends on both the foreign DNA fragments & the
plasmid.

3) Step 3: Insertion i) The fragments of DNA that contain target gene is inserted into plasmid at
the disrupted lacZ gene.
(Insertion of DNA fragment ii) Addition of DNA ligase is used to catalyses the formation of
containing gene of interest into phosphodiester bond to join the two DNA molecules.
plasmid/ vector) iii) Forming a recombinant DNA.

Step 4: Transformation and i) Transformation - Introduction of cloning vector into bacterial cells (host
amplification. cell) by using calcium chloride (CaCl2) heat shock method// electroporation.
ii) Amplification - the production of many DNA copies from one master
region of DNA by cloned each plasmid until there are millions of copies to work
with. This process occurs as the bacteria grow/ reproduce.

iii) This will result in three types of bacteria:
a) Bacteria that take up non-recombinant plasmid.
b) Bacteria that take up recombinant plasmid.
c) Bacteria that do not take up any plasmid.

Step 5: Screening i) Process identification of cells clones carrying recombinant plasmids.
ii) The bacteria that have taken up the different types of recombinant DNA can
be distinguished by their differential resistance to different antibiotics.

Example;
- The cloning vector used, bacterial plasmids possess selectable marker

gene such as lacZ and ampR .
- The lacZ gene sequence contains a restriction site for a specific restriction

enzyme.
- E.g.: by using EcoRI, it will cleave the plasmid at the restriction site at the

lacZ gene.
- If the target gene is inserted within the restriction site, then the lacZ gene

will not function

Example is Blue –white screening.
The bacteria cell is cultured in a medium containing antibiotic ampicillin & the
sugar X- gal (contain lactose).
- Medium antibiotic ampicillin is used to eliminate bacteria cell without
plasmid.
- Sugar X-gal is used to determine the bacteria cell that contain
recombinant plasmid.

1) Result: In the medium antibiotic ampicillin:
- Bacteria cells that contain the plasmid (both recombinant & non-recombinant
plasmid) will grow.
- Bacteria cells without any plasmid will be killed.
Conclusion:
Only the bacteria cell that contain plasmid can survive in antibiotic
ampicillin because there is resistance to antibiotic ampicillin (has ampR gene
/ampicilin resistance gene).

2) Result: In X- gal medium
i) Bacteria with non-recombinant plasmids will form blue colonies because
the bacteria that contain plasmids with intact lacZ (do not carry target gene)
are able to codes the enzyme β- galactosidase, an enzyme which can
hydrolyse X-gal.
ii) Bacteria with recombinant-plasmids containing foreign DNA will form white
colonies because the lacZ gene is not functional, so bacteria cell is not being
able to codes the enzyme β-galactosidase, so cannot hydrolyse X-gal.
Conclusion:
- The bacteria that contain plasmids with intact lacZ (do not carry target gene)
are able to codes the enzyme β- galactosidase, an enzyme which can
hydrolyze X-gal. This will produce a compound which makes the colony blue.
- If the foreign DNA is inserted at a restriction site (that is lacZ) in the gene, the
gene will not function.
- These bacteria which contain recombinant plasmids will form white colonies
because the lacZ gene is not functional (are not be able to codes the enzyme
β-galactosidase, so cannot hydrolyse X-gal).

Summary: Method in gene cloning by using plasmid as a vector

STEP 1: ISOLATION OF GENE
• Isolate plasmid as cloning vector from bacterial cells.
• Isolate foreign DNA that containing gene of interest from donor cell.

STEP 2: CLEAVE/ CUT
• Isolated bacterial plasmids & foreign DNA are cleaved with same restriction enzyme.
• Producing compatible ends on both the foreign DNA fragments & the plasmid.

STEP 3: INSERTION
• The fragments of DNA that contain target gene is inserted into plasmid at the

disrupted lacZ gene.
• Addition of DNA ligase is used to catalyses the formation of phosphodiester bond

to join the two DNA molecules.
• Forming a recombinant DNA.

STEP 4: TRANSFORMATION AND AMPLIFICATION.
• Introduction of cloning vector into bacterial cells by using calcium chloride

(CaCl2) heat shock method through transformation process.
• Amplification - the production of many DNA copies from one master region of

DNA by cloned each plasmid until there are millions of copies to work with

STEP 5: SCREENING.
• Process identification of cells clones carrying recombinant plasmids.
• Only a cell that took up a plasmid, which has ampR gene, will reproduce & form a

colony.
• Colonies with non-recombinant plasmids will be blue, because they can

hydrolyse X-gal.
• Colonies with recombinant plasmids, in which lacZ is disrupted, will be white,

because they cannot hydrolyse X-gal.
• These colonies (white colonies) will be selected.

8.3 APPLICATION OF RECOMBINANT DNA
TECHNOLOGY

a) Briefly explain applications of Recombinant DNA Technology in mass production of insulin using
cDNA (CLO 3).

Production of Human Insulin by E. coli

1. Deficiency in the levels of blood insulin in one of the main causes of diabetes.
2. At one times, diabetes was treated with regular injections of insulin from animals, like cattle & pig.
3. But human insulin from animal sources are different chemically (different in only 2 of 51 amino acids), and

repeated injections from animal insulin led to allergic reactions in many patients.
4. Today human insulin produced by E. coli overcame this problem for many patients & actually save the time &

cost of the treatment.
5. The technique used was through recombinant DNA technology, using E. coli, and the name of this product

is Humulin S.

What is benefits of insulin produced by genetic engineering?
1. The gene used is from human.
2. Insulin produced similar to human insulin.
3. Non allergic.
4. Cheaper & can be reproduce in large amount.
5. Syariah compliance

b) Describe the steps in production of insulin using cDNA (CLO 3).

1. Complementary DNA or cDNA - cDNA is a DNA molecule synthesize in vitro using mRNA template
catalysed by an enzyme reverse transcriptase.

2. A cDNA molecule is identical to a native DNA, but lack the non-coding regions, introns.
3. The major sources of DNA which can be inserted into vectors & be cloned:
4. cDNA made in the laboratory from isolated mRNA.
5. cDNA method produces a more limited kind of gene library, a cDNA library.
6. A cDNA library represents only part of the cell’s genome because it contains only (exons) the genes that

were transcribed.
7. A cDNA molecule therefore corresponds to a gene, but lacks the introns present in the DNA of the genome.

Steps in production of cDNA
1. mRNA extracted from cells.
2. Enzyme reverse transcriptase is used in vitro to
make single stranded DNA.
3. Following enzymatic degradation of mRNA, a
second DNA strand, complementary to the first, is
synthesized by DNA polymerase.
4. This double stranded DNA, called complementary
DNA is the modified by addition of restriction enzyme
recognition sequences at each end.
5. Finally, the cDNA is inserted into vector DNA in a
manner similar to the insertion of genomic DNA
fragments.
6. Therefore, the cDNA that are cloned make up a
library containing a collection of genes.

9.0 REPRODUCTION

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COURSE LEARNING OUTCOMES

9.1 REPRODUCTION IN PLANT

a) State and define the terminologies involve in gamete formation in flowering plants:(CLO1)
i. Male gamete:
microsporangium/pollen sac, microsporocyte/microspore mother cell, microspore, tetrad,
pollen grain/male gametophyte, generative cell, tube cell
ii. Female gamete:
megasporangium, megasporocyte/megaspore mother cell, megaspore,
female gametophyte/embryo sac, antipodal cell, polar nuclei, egg cell, synergid cell.

b) Explain the development of a pollen grain and formation of male gamete. (CLO 3)
c) Explain the development of ovule, embryo sac and formation of female gamete. (CLO 3)
d) Explain double fertilization in the formation of seed. (CLO 3)

9.2 HUMAN REPRODUCTIVE SYSTEM

a) Overview male reproductive organ (testes) and the structure of spermatozoa. (CLO 1)

b) Explain the structure of spermatozoa. (CLO 3)

c) Explain the role of hormones in spermatogenesis: Gonadotropin-Releasing Hormone

(GnRH), Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH) and

Testosterone. (CLO 3)

d) Explain the stages of spermatogenesis and its hormonal control. (CLO 3)

e) Overview female reproductive organ (ovary) and the structure of the secondary oocyte.

(CLO 1)

f) Explain the structure of the secondary oocyte. (CLO 3)

g) Explain the role of hormones in female reproductive cycle: GnRH, LH, FSH, Estrogen

and Progesterone. (CLO 3)

h) Explain the stages of oogenesis. (CLO 3)

i) Explain female reproductive cycle and its hormonal control: (CLO 3)

i. ovarian cycle

ii. uterine/menstrual cycle

9.3 FERTILIZATION AND FOETAL DEVELOPMENT

a) Explain stages that lead to fertilization: (CLO 3)

i. capacitation

ii. acrosomal reaction
iii. fusion of sperm head membrane and oocyte

iv. cortical reaction

b) Define embryogenesis (CLO 1)

c) State developmental stages from zygote to the formation of morula, blastocyst and

gastrula through cleavage (CLO 1)

d) Define organogenesis (CLO 1)

e) State the organ formed from each germ layers during organogenesis. (CLO 1)

9.4 ROLES OF HORMONES DURING PREGNANCY AND PARTURITION

a) Explain the roles of hormones during pregnancy

i. Progesterone

ii. Estrogen

iii. Human chorionic gonadotrophin (hCG) (CLO 3)

b) Explain the role of hormones during parturition/ birth process.

i. Progesterone,

ii. Estrogen,

iii. oxytocin,

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iv. Prostaglandin (CLO3)

9.1 REPRODUCTION IN PLANT

a) State and define the terminologies involve in gamete formation in flowering plants:
recombinant DNA technology (CLO1)
i. Male gamete:
microsporangium/pollen sac, microsporocyte/microspore mother cell, microspore,
tetrad, pollen grain/male gametophyte, generative cell, tube cell

TERMINOLOGIES DEFINITION

Microsporangium/pollen Structure in certain spore-bearing plants in which the
sac microspores are formed.

Microsporocyte/microspore Diploid cell in plants that divides by meiosis to give rise to

mother cell four haploid microspores.

Microspore Male spore germinate that give rise to a male
gametophyte or microgametophyte
Tetrad Four spores produced after the process of Meiosis I and
Meiosis II.
Pollen grain/male Cell to produce male gamete. It consists of 2 cells: the
gametophyte generative cell and the tube cell.
Generative cell Cell that will produce 2 sperm cells by mitosis after a
pollen grain lands on the stigma.
Tube cell Cell that will produce pollen tube which deliver the
sperms to the female gametophyte.

a) State and define the terminologies involve in gamete formation in flowering plants:

(CLO1)

i. Female gamete:
megasporangium, megasporocyte/megaspore mother cell, megaspore,
female gametophyte/embryo sac, antipodal cell, polar nuclei, egg cell,synergid
cell.

TERMINOLOGIES DEFINITION

Megasporangium

structure in certain spore-bearing plants in which the
megaspores are formed.

Megasrosporocyte/megaspore diploid cell in plants that divides by meiosis to give rise

mother cell to four haploid megaspores.

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Megaspore Germinate to form the female gametophyte or
Embryo sac /female megagametophyte.
gametophyte multicellular large cell with 8 haploid nuclei, derived
antipodal cell (3 cells) from the surviving megaspore which divides by mitosis
polar nuclei (2 cells) 3 times without cytokinesis.
3 cells, located at the opposite end of the embryo sac
egg cell (1 cell) with unknown function.
synergid cell (2 cells) Cells are not partitioned into separate cells but share
the cytoplasm of the large central cell of the embryo
sac, located in the mid region of the embryo sac.
haploid female gamete forming a zygote after
fertilization, which gives rise to the diploid embryo.
located at the micropyle end, flank the egg and help
attract and guide the pollen tube to the embryo sac.

b) Explain the development of a pollen grain and formation of male gamete. (CLO 3)

Pollen grains are produced in anthers.

1. Each anther consists of 4 pollen sacs or microsporangia.

2. The cells within pollen sacs/microsporangium are called microspore
mother cells / microsporocyte.//
3. Each microsporangium contains numerous numbers of diploid
microspore mother cells / microsporocyte.
4. Each microspore mother cell (microsporocyte) and undergoes meiosis.

5. Producing 4 haploid cells known as microspores/ tetrad.

6. Each microspore divides once by mitosis.

7. Producing a male gametophyte/microgametophyte/pollen grain
that consisting of only two cells (the generative cell & the tube cell.

8. Together, these two cells & the spore walls constitute an
immature pollen grain.

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9. During pollination, pollen grain will be
transferred from anther to the stigma.

1100.. TThhee ppoollelennggraraininwbillegceormmeinmateatounrestmigamlea.
gametophyte when the generative cell divides by
mitosis to form 2 male gametes // Pollen grain
become mature to form two nonmotile sperm cells.

11.Tube cell will produce pollen tube which will
elongate down the style.

12. As the pollen tube elongates through the style and
grows to reach the microphyle, the generative cell
will divide by mitosis.

13. To produce two male gametes (2 sperm cells)

c) Explain the development of ovule, embryo sac and formation of female gamete. (CLO 3)

THE STRUCTURE OF OVULE DESCRIPTION

Ovule located within the ovary.
1) The main tissue in ovule is the nucellus,
which supported by the short stalk
called funicle.
2) The ovule is protected by integuments.
3) There is a tiny opening called micropyle
at the apex of the ovule.
4) And chalaza at the opposite end.

STEP OF DEVELOPMENT OF AN OVULE, EMBRYO SAC & FORMATION OF
FEMALE GAMETE.

AB C D E
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1. The female gametophyte begins to develop within the ovules (megasporangium)
A of the ovary.

2. Each ovule /megasporangium which produces one megasporocytes/ megaspore
mother cell, 2n.

B Megaspore mother cell (megasporocyte) enlarges & undergo meiosis, producing four
haploid megaspores.

C 3 of these megaspores degenerate, only 1 megaspore survives.

The nucleus of surviving megaspore divides by mitosis three times without
cytokinesis to form eight haploid nuclei of cell which are arranged in groups of four
D nuclei at the two poles.

6. One of the nuclei from each pole migrate to the centre of the embryo sac. These two
nuclei are called polar nuclei (n+n). They are not partitioned into separate cells but share
the cytoplasm of the large central cell of the embryo sac.

7.The three cells/nuclei at the opposite end to the micropyle form three antipodal
E cells with unknown function.

8. The three cells at the micropyle end consist of two synergid cells that flank the
egg cell.
9. The synergids function in attract & guide the pollen tube to the embryo sac.

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COMPARISON BETWEEN POLLEN GRAIN AND EMBRYO SAC

SIMILARITIES

Both are haploid structure // both are gametophytes.
Both are produced through mitosis of haploid spore.

DIFFERENCES: POLLEN GRAIN

EMBRYO SAC pollen grain develop in pollen sac /
microsporangium.
Embryo sac develop in microsporocyte / microspore mother cell undergo
ovule/megasporangium meiosis to produce microspore during formation of
Megasporocyte / megaspore mother cell pollen grain.
undergo meiosis to produce megaspore
during formation of embryo sac only 2 nuclei/cell are formed through mitosis with
cytokinesis in pollen grain formation.
Eight nuclei are formed through three times
mitosis without cytokinesis in embryo sac only two haploid cells produced in pollen grain
formation formation.
Seven haploid cells produced after
cytokinesis in embryo sac formation

Embryo sacs surround by integuments pollen grain surround by exine and intine.

Embryo sac retained within flower pollen grain released from the flower.

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d) Explain double fertilization in the formation of seed. (CLO 3)

POLLINATION DESCRIPTION

1) Pollination is a process of transfer of pollen
grain from an anther to a stigma.

2) It occurs when pollen released from
anthers is carried by pollination agents
(wind or animals) to land on a stigma.

3) A pollinator is any agent that transfers
pollen from male to female reproductive
parts of flowers of the same plant species.

4) E.g.: insects, birds, other animals, water

currents, air currents & wind.

DOUBLE FERTILIZATION IN THE FORMATION OF SEED

A BC
A After landing on receptive stigma, the pollen grain absorbs moisture & germinates.

Tube cell producing a pollen tube.

B

The generative cell divides by mitosis to produce two male gametes.

C Pollen tubes grow down the style toward the ovary until it reaches the micropyle.

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DE

The tip of the pollen tube enters the ovary through the micropyle.

D The tube cell nucleus degenerate and discharges two male gametes within the embryo

sac.

In the embryo sac. One male gamete (n) fertilizes the egg (n) to form the zygote (2n).

The other male gamete combines with the two polar nuclei to form a triploid (3n)

E endosperm, as a food-storing tissue of the seed.(provide nutrient to the developing

embryo)

The union of two male gametes cells with different nuclei of the embryo sac is termed
double fertilization.

DOUBLE FERTILIZATION DESCRIPTION

Definition The union of two male gametes cells with different
nuclei of the embryo sac.

Important: 1. Double fertilization ensures that the endosperm
The formation of seed will develop only in the ovules where the egg
has been fertilized.

2. The endosperm is rich in nutrients, which it
provides to the developing embryo.

1. After double fertilization, the ovule develops into a
seed & the ovary develops into a fruit enclosing
the seed.

2. It remains attached to the parent plant & continues
to receive nutrients from it as it develops.

3. Initially, these nutrients are stored in the
endosperm, but later in seed development in many
species, the storage function is taken over by the

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swelling storage leaves (cotyledons) of the embryo
itself.
4. The cotyledons store food absorbed from the
endosperm before the seed germinate.

9.2 HUMAN REPRODUCTION SYSTEM
COMBINANT DNA TECHNOLOGY

a) Overview male reproductive organ (testes) and the structure of spermatozoa.
(CLO 1)

TESTES DESCRIPTION

1. The male gonad, testes
(singular, testis) produce sperm
in highly coiled tubes called
seminiferous tubules.

2. The Leydig cells, scattered in
connective tissue between the
tubules, produce testosterone
and other androgens.

3. A system of ducts including
epididymis, vas deferens and
uretra

4. Accessory sex glands like
seminal vesicles, bulbourethral
gland and prostate gland.

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b) Explain the structure of spermatozoa. (CLO 3)

STRUCTURE OF SPERMATOZOA DESCRIPTION

1. Structure of sperm cell consist of
head, middle piece/body and tail
region.

2. The head region consists of
acrosome at its tip which contain
hydrolytic enzyme to help sperm
penetrate the egg cell/ovum.

3. Head region also contain haploid
nucleus at the centre.

4. A centriole basal body for the
flagellum

5. The middle piece/body contain
mitochondria to supply
ATP/energy for movement of tail.

6. Tail drives the swimming of
sperm cell toward egg cell at
Fallopian tube.

7. Ability to swim is essential for the
male fertility.

c) Explain the role of hormones in spermatogenesis: Gonadotropin-Releasing

Hormone (GnRH), Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH)

and Testosterone. (CLO 3)

ROLES OF HORMONES IN SPERMATOGENESIS

d) Explain the stages of spermatogenesis and its hormonal control. (CLO 3)

f) Explain the structure of the secondary oocyte. (CLO 3)

g) Explain the role of hormones in female reproductive cycle: GnRH, LH, FSH, Estrogen

and Progesterone. (CLO 3)

h) Explain the stages of oogenesis. (CLO 3)

i) Explain female reproductive cycle and its hormonal control: (CLO 3)

i. ovarian cycle

ii. uterine/menstrual cycle

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At puberty,
hypothalamus secretes gonadotropin-releasing hormone, GnRH.

GnRH stimulates anterior pituitary gland to secrete
follicle stimulating hormone, FSH and luteinizing hormone, LH.

FSH acts on/ promote activity of LH acts on
Sertoli cell, the Leydig cell

Sertoli cell, Leydig cell
For support and nourish to secrete testosterone and
developing sperm and stimulate promote spermatogenesis
in the testis and responsible for the
spermatogenesis secondary sexual characteristics

in the testis that develop in the male

The negative feedback mechanism controls Testosterone regulates level of GnRH, FSH
the male sex hormone production in males. and LH

Sertoli cell release peptide High testosterone level
hormone inhibin

that reduce FSH secretion by
anterior pituitary gland.

inhibitory effects directly on inhibitory effects
anterior pituitary, reduce indirectly on
the releasing of LH.
hypothalamus, reduce
the releasing of GnRH.

Decrease of GnRH also inhibit secretion of FSH by
negative feedback.

When the sperm count is high, Inhibin increases and
inhibits the output of FSH and reduce of
spermatogenesis.

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SPERMATOGENESIS

● Spermatogenesis is the production of sperm (spermatozoa).

● It happens in the seminiferous tubules of testis, beginning during puberty when a boy is
between about 11 & 15 years old and continuing throughout the rest of life.

Germinal epithelium cells/ primordial
germ cell in testis

~ divide & differentiate into stem cells
that divide mitotically to form
spermatogonia (2n).

Spermatogonia ( 2n cell)
~divide by mitosis to produce more
spermatogonia.

Some spermatogonia
~ Move towards the middle of the tubule
& grow larger, forming primary
spermatocytes (2n).

Primary spermatocytes (2n)
~ Then begins to divide by meiosis I .
To form two secondary spermatocytes (n)

Secondary spermatocytes (n)
~ undergoes the second meiotic division,
producing haploid spermatids (n).

Spermatid (n)
~ obtain the nutrient from the Sertoli cells
& undergo cell differentiation (formation of
structures like flagella and acrosome) &
finally develops as mature sperm
(spermatozoa).

gradually develops into a spermatozoa

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STRUCTURE AT TUBULE DESCRIPTION
SEMINIFEROUS
• During the stages of spermatogenesis take
place, the cells get closer to the lumen in the
middle of the seminiferous tubule.

• They are nourished Sertoli cells (very large,
non-dividing cells).

• Sperms become detach from the Sertoli cells
& release into the lumen.

• Fully formed sperm move from the lumen of
the seminiferous tubules to the epididymis,
carried in fluid secreted by the Sertoli cells.

• Mature sperm are stored in the vas
deferens

• At this stage they do not swim until they are
ejaculated.

At

Spermatogenesis
process

87

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e) Overview female reproductive organ (ovary) and the structure of the secondary
oocyte. (CLO 1)

FEMALE REPRODUCTIVE DESCRIPTION
ORGAN
• ovary locate in the abdominal cavity.

⮚ It flanking & attached by mesentery to, the
uterus.

⮚ Each ovary is enclosed in a tough
protective capsule & contains follicles.

⮚ Each follicle consists of an oocyte.

⮚ Oocyte is a partially developed egg,
surrounded by a group of support cells.

⮚ The surrounding cells (follicle cells)
nourish & protect the oocyte during
oogenesis.

• Oviduct, or Fallopian tube, extends from
the uterus toward each ovary.
At ovulation, the egg released into the
abdominal cavity near the funnel-like
opening of the oviduct.

• The uterus is a thick, muscular organ that
can expand during pregnancy.

⮚ The inner lining of the uterus, the
endometrium, is richly supplied with blood
vessels.

• The neck of the uterus, the cervix, opens
into the vagina.

• The vagina is a muscular but elastic
chamber that is the site for insertion of the
penis & deposition of sperm during
copulation.

⮚ It also serves as the birth canal through
which a baby is born.

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f) Explain the structure of the secondary oocyte. (CLO 3)

STRUCTURE OF SECONDARY DESCRIPTION
OOCYTE
1. Cytoplasm - containing granules of fat &
Secondary oocyte in Graafian follicle cortical granules.

2. Nucleus - a large haploid nucleus (pro-
nucleus)

3. Plasma membrane - surrounds the
cytoplasm of the secondary oocyte.

4. Granulosa cell - layer of follicle cells.
5. Antrum - fluid-filled space; secreted by

granulosa cells.
6. Zona pellucida - secrete by granulosa

cells, function in mediates sperm-egg
recognition during fertilization.
7. Corona radiata - layer of follicle cells
called granulosa cell which protects &
nourish the secondary oocyte.

h) Explain the stages of oogenesis. (CLO 3)

OOGENESIS

Oogenesis is the production of secondary oocyte in ovary
● It happens in the ovary, beginning during fetus continue during puberty and continuing until
menopause.

● It is not a continuous process:

⮚ Begins before birth but arrested at prophase I
⮚ At puberty, under hormonal control but until metaphase II
⮚ Its only completed the meiosis II if fertilized by sperm.

16

1 Begins in the female embryo.
2
3 primordial germ cell divides by mitosis rapidly and
4 differentiate to produce more diploid oogonia (2n).

5 2. Oogonia undergo mitosis and differentiate to

6 become primary oocytes (2n).
At this time, follicle cell surrounds primary
oocytes, forming primordial follicles.

Primary oocytes undergo meiosis I but
remain in prophase I.

Starting at puberty (Anterior pituitary gland
release FSH)

Only one primary oocyte activated each month.
Activated primary oocytes completing the

meiosis I. yield two haploid cells, a first polar body
and a secondary oocyte(n). Unequal of
cytokinesis, produce bigger secondary oocyte

The secondary oocyte undergoes meiosis II but stop at
metaphase II. It will release from ovary during ovulation
process.

If sperm penetrate the secondary oocyte, it will
complete the meiosis II. Producing ovum (n) and
second polar body

If secondary oocyte is not fertilized, it dies and
discharged during menstruation.

17

Development of follicle in ovaries of female

g) Explain the role of hormones in female reproductive cycle: GnRH, LH, FSH, Estrogen

and Progesterone. (CLO 3)

i) Explain female reproductive cycle and its hormonal control: (CLO 3)

i. ovarian cycle

ii. uterine/menstrual cycle

18

FEMALE REPRODUCTIVE CYCLE

Two female reproductive cycle, ovarian and uterine cycle are linked together through hormonal
control.

OVARIAN CYCLE DESCRIPTION

1. Ovarian cycle is referred to sequence of
changes in ovary.

2. Consist of two phase, follicular phase
and luteal phase.

3. Between these two phases is ovulation
process.

During follicular phase,
4. FSH stimulate development of primary

follicle to form Graafian follicle.
5. In ovulation, Graafian follicle rupture,

releasing secondary oocyte.

In luteal phase,
6. the ruptured Graafian follicle develops

into corpus luteum.
7. If fertilization process occurs, corpus

luteum secrete oestrogen and
progesterone that maintain thickening of
uterine lining/ endometrium during
pregnancy.
8. If fertilization does not occur, corpus
luteum degenerates.

19

HORMONAL CONTROL IN OVARIAN CYCLE

Ovarian cycle begins with release of gonadotropin releasing hormone, GnRH by
hypothalamus.
GnRH stimulate anterior pituitary to secrete FSH and LH.
In follicular phase,
FSH stimulates the development of primary follicle to become Graafian follicle//FSH stimulate
follicle to grow/develop.
The developing/growing follicle secrete estrogen.
Start with a slow rise in estrogen secretion.
The estrogen secreted, cause a negative feedback on pituitary gland.
The low level of estrogen keeps FSH and LH level low.
Secretion of estrogen by the growing follicle increases sharply.
The high concentration of estrogen stimulates the release of gonadotropin to increase the
output of GnRH.
GnRH stimulates the anterior pituitary gland to secrete LH and FSH.
LH stimulate ovulation//induces the final maturation of the follicle.
Graafian follicle ruptured and releasing the secondary oocyte.
During luteal phase,
LH stimulates the transformation of the ruptured Graafian follicle into Corpus luteum.
Under continued influence of LH, the corpus luteum secretes progesterone and estrogen.
As the levels of these hormone increase, they exert negative feedback on the hypothalamus
pituitary.
Inhibiting the secretion of LH and FSH.
Near the end of the luteal phase, the corpus luteum disintegrates if fertilization does not occur.
causing the concentration of estrogen and progesterone to decline.
The pituitary begins to secrete enough FSH to stimulate the growth of new follicles in the
ovary// initiating next ovarian cycle.

20

MENSTRUAL CYCLE DESCRIPTION

1. Uterine / menstrual cycle is referring to
sequence of changes in endometrial wall of
non-pregnant female.

2. Averages 28 days
3. Consist of three phase, menstrual flow

phase, proliferative phase and secretory
phase

In menstrual flow phase, menstruation
occurs.

4. If fertilization does not occur and corpus
luteum disintegrates

5. The endometrium disintegrates & uterus
contracts.

6. Small blood vessels in the endometrium
constrict, releasing blood that is shed along
with endometrial tissue & fluid bleeding /
menstruation.

7. Due to low levels of progesterone
(*function in stimulates maintenance the
thickening of the endometrium).

In proliferative phase,

8. endometrium will be repaired and
thickening.

9. Stimulated by estrogen that secreted from
growing follicle in ovary.

In secretory phase,

10. The endometrium/ endometrial lining/
uterine lining continues to thicken,

11. endometrial arteries enlarge & endometrial
glands grow to secrete nutrient fluid rich in
glycogen.

12. Preparing for any implantation of fertilized
egg.

21

HORMONAL CONTROL IN OVARIAN CYCLE

During menstrual flow phase,
Endometria begin to shed due to the low level of progesterone.
Stimulate hypothalamus to secrete Gonadotropin Releasing Hormone (GnRH)
GnRH stimulate the anterior pituitary gland to secrete Follicle Stimulating Hormone (FSH) and

Luteinizing Hormone (LH)
The FSH stimulates the growth and development of follicles in the ovary.
Developing follicles secrete estrogen.

During proliferative phase,

Estrogen repairs and thickens the endometrium.
As follicles mature, they secrete more estrogen which stimulate the anterior pituitary gland to
secrete LH (and FSH).
LH stimulate ovulation.
After ovulation, LH stimulates the formation of corpus luteum.

During secretory phase,

The corpus luteum secretes large amounts of progesterone AND small amounts of estrogen.
The high level of progesterone inhibits the release of GnRH.
Which inhibits FSH and LH secretion by negative feedback mechanism.
oestrogen and progesterone maintain the thickening of endometrium.

IF FERTTILIZATION OCCUR (HAVE IF FERTTILIZATION DOES NOT OCCUR
PREGNANCY)
(NO PREGNANCY)
• LH also stimulate corpus luteum secretes
large amounts of progesterone AND small • If fertilization does not occur, the corpus
amounts of oestrogen to continue luteum disintegrate/degenerate.
development and maintenance of the uterine
lining. • Progesterone and oestrogen levels fall, cause
constriction of artery in endometrium.
• This process is continued if pregnancy occurs
to ensure the embryo can implant. • Blood and endometrial tissue are

• Actually, hCG from developing placenta shed/discharged through menstruation.
maintains the activity of corpus luteum (to • FSH and LH secretion is no longer inhibited,
secrete estrogen & progesterone) until
placenta fully developed then allowing another cycle to begin.
• Anterior pituitary will secrete enough FSH to

stimulate the growth of new follicle in the

ovary.

• After 4 months pregnancy, corpus luteum is
degenerated.

• High concentration estrogen & progesterone
has negative feedback effect on the
hypothalamus/anterior pituitary gland. It
inhibits secretion of FSH and LH.

22

HORMONES COORDINATE THE UTERINE CYCLE WITH THE OVARIAN CYCLE

23

9.3 FERTILIZATION & FEOTAL DEVELOPMENT
.3.

a) Explain stages that lead to fertilization: (CLO 3)
i. capacitation
ii. acrosomal reaction

iii. fusion of sperm head membrane and oocyte
iv. cortical reaction

STAGES DESCRIPTION

1. Definition: the enhancement of the sperm function in the female
reproductive tract.

2. Secretion of female reproductive tract alter certain molecule on the surface of
sperm’s acrosome (glycoprotein coat and seminal proteins)

CAPACITATION 3. and increase the motility of sperm / sperm become more active.

4. Capacitation is important because:

i. It allows hydrolytic enzymes (hyaluronidase & protease) in the acrosome
to be released.

ii. Makes the sperm possible to penetrate an egg in the next stage.

ACROSOMAL 1. When sperm reach secondary oocyte the acrosome membrane will be rupture
REACTION & release of hydrolytic enzymes (hyaluronidase & protease) from the
acrosome.

.
2. Hyaluronidase will digest the corona radiata.

• When sperm head reach zona pellucida, it binds to the receptor sperm site
(glycoproteins) in zona pellucida which is at egg’s membrane.

• First sperm that bind to the zona pellucida layer will trigger changes in
acrosome of the sperm.

3. Protease will digest a path through the zona pellucida to the surface of the
secondary oocyte

FUSION OF 1. Acrosomal reaction enable one sperm cell to penetrate the weakened zona
SPERM HEAD pellucida.
MEMBRANE &
SECONDARY 2. The sperm head membrane will fuse with the secondary oocyte’s plasma
membrane (two membrane fuse), releasing sperm nucleus into the cytoplasm
OOCYTE of the secondary oocyte.
MEMBRANE

CORTICAL 1. Cortical granules fuse with plasma membrane and release enzyme into zona
REACTION pellucida via exocytosis

2. causing the zona pellucida harden to form fertilization membrane
3. which blocks the entrance of other sperms // prevent polyspermy// Act as
4. slow block to polyspermy
5. Secondary oocyte complete Meiosis II and form ovum and second polar body
6. Female and male pronucleus develops.
7. Male and female pronucleus fuse to form diploid zygote.

24

EXTRA INFORMATION.
• How zona pellucida change to form fertilization membrane?
• The fusion of the secondary oocyte membrane & sperm membrane
triggers a signal-transduction pathway that causes the secondary oocyte’s
endoplasmic reticulum to release calcium (Ca2+) into the cytosol.
• The Ca2+ release from the ER begins at the site sperm entry & then
propagate a wave across the fertilized secondary oocyte.
• High Ca2+ in cytosol brings about the change in the cortical granules, which
lie just under the secondary oocyte’s plasma membrane.
• The cortical granules fuse with the plasma membrane & release their
contents, including enzyme into the zona pellucida via exocytosis.
• These enzymes will thicken & harden the zona pellucida to form
fertilization membrane preventing polyspermy (prevents other sperm from
entering the secondary oocyte) know as slow block polyspermy.
• The same time: the secondary oocyte completes meiosis II to produce an
ovum & a second polar body (activation of the secondary oocyte).
• Then, fusion of egg (ovum) & sperm nuclei occurs in the cytoplasm.
• The sperm nucleus is drawn towards the ovum nucleus & they fuse to
form the zygote.

25

b) Define embryogenesis (CLO 1)

c) State developmental stages from zygote to the formation of morula, blastocyst

and gastrula through cleavage (CLO 1)

Embryogenesis: Process by which embryo forms and develops that involve cell
division and cell differentiation.

DEVELOPMENTAL STAGES FROM DESCRIPTION
ZYGOTE THROUGH CLEAVAGE
MORULA 1. After fertilization, zygote begins to
divide through cleavage in oviduct.

2. In cleavage, zygote is dividing into
many smaller cells; from one cell of
zygote into two cell, four cell, eight cell
and so on

3. As a result, embryo do not enlarge in
size because cells retained in zona
pellucida.

4. Embryo typically arrive at uterus as a
solid sphere ball of cells, consists 16
cells & more (about 50 cells), known as
morula

BLASTOCYST 1. Blastocyst is formed from morula
through cleavage.

2. As morula divide, a fluid-filled cavity
form in the centre, transforming into
blastocyst.

3. Blastocyst consists of a fluid-filled
hollow spherical ball of cells, about 100
cells.

4. Comprising the outer layer trophoblast
and inner cell mass.

5. Trophoblast will develop into future
chorion

6. Inner cell mass will develop into future
embryo and extraembryonic
membrane

7. The fluid-filled cavity is known as
blastocoel.

8. Blastocyst cells are called
blastomeres.

9. Blastocyst attaches /implants to the
endometrium wall usually after 7 days
after fertilization

10. Usually after seven days after
fertilization.

11. Blastocyst obtain nourishment
through the trophoblastic/chorionic villi
from endometrium

12. Cells within the inner cell mass migrate
and divide to epiblast (upper layer) and

26

GASTRULA hypoblast (lower layer)
13. Epiblast develop into embryo and

amnion
14. Hypoblast develop into yolk sac

1. Gastrulation / formation of gastrula
take place after blastocyst implantation
complete.

2. The blastomere cells will divide and
rearrange to form 3 germ layers
(ectoderm, mesoderm and endoderm)

3. The epiblast forms the ectoderm and
endoderm.

4. Mesoderm develops in between the
ectoderm and endoderm.

5. Blastocyst develops into gastrula.
6. End up with formation of three germ

layers and extraembryonic membrane
(chorion, amnion, yolk sac, and
allantois)

27

b) Define organogenesis (CLO 1)
c) State the organ formed from each germ layers during organogenesis. (CLO 1)

Organogenesis: The formation of organs through 3 germ layers (ectoderm,
mesoderm and endoderm), that already formed in gastrulation process.

THE ORGAN FORMED FROM DESCRIPTION
EACH GERM LAYERS DURING
• The outermost primary germ layer in an
ORGANOGENESIS animal embryo.
ECTODERM
• Develops into the nervous system,
MESODERM epidermis & sweat glands.

• The middle primary germ layer in animal
embryo.

• Develops into the reproductive system,
urinary system (kidneys), muscle,
bones, skin, cardiovascular system
(blood & blood vessels).

ENDODERM • Innermost primary germ layers in an

animal embryo.
• Develops into the lungs, liver, the lining

of the digestive organs & some

endocrine glands.

28

9.4 ROLES OF HORMONES DURING
PREGNANCY AND PARTURITION

a) Explain the roles of hormones during pregnancy (CLO 3)
i. Progesterone
ii. Estrogen
iii. Human chorionic gonadotrophin (hCG)

• Appropriate levels of hormones are essentials for maintaining pregnancy &
preventing spontaneous abortion.

ROLES OF HORMONES DESCRIPTION
DURING PREGNANCY
• In the first 4 months of pregnancy, trophoblast cells of
HUMAN CHORIONIC the implanted blastocyst/embryo //the chorion secrete
GONADOTROPIN (hCG), hCG,

ESTROGEN • maintains the activity of corpus luteum (to secrete
estrogen & progestrerone).

• To maintain the thickening of endometrium/uterine

lining for embryonic development.
• After the 4 month of pregnancy, corpus luteum

begins to disintegrate.

• The placenta takes over the function of secreting

oestrogen & progesterone.

• Estrogen stimulates • Estrogen &

the development of progesterone cause the
mammary ducts (in continued development of
mammary gland) in the endometrium & thus
breast to prepare for prevent menstruation.

lactation & also • Both hormones
stimulates the inhibit the release of FSH
growth of uterus. from the anterior pituitary,

• During late hence prevent development
pregnancy, estrogen of follicles in the ovaries.

level increases than

progesterone

PROGESTERONE. • Progesterone
completes the
stimulates the
development of
mammary glands in
breast by estrogen &
prepare for lactation.

• High level of
progesterone to
prevent miscarriage.

29

• Progesterone also
inhibits the contraction
of uterine muscles
during end pregnancy.

(The level of
progesterone decreases
just before birth.)

STAGE OF PREGNANCY DESCRIPTION
FIRST TRIMESTER
● In the first 4 months of pregnancy
● Trophoblast cells of the blastocyst/ embryo secrete

hCG // chorion secrete hCG
● hCG maintains the corpus luteum
● Corpus luteum will continue to secrete oestrogen

and progesterone.
● to maintain the thickening of endometrium/

endometrial lining/ uterine lining for embryonic
development
● high level of progesterone to prevent the
miscarriage.
● The hCG high level/ level increases (dramatically)
during the first trimester
● End of the first trimester placenta takes the role of
corpus luteum to secrete oestrogen and
progesterone.

SECOND TRIMESTER ● Placenta is fully developed.
● hCG secretion decline
● corpus luteum begins to disintegrate.
● placenta takes the role of corpus luteum to secrete

oestrogen and progesterone.
● to maintain the thickening of endometrium/

endometrial lining/ uterine lining for embryonic
development.

30

THIRD TRIMESTER ● Estrogen stimulates the development of mammary
ducts (in mammary gland) in breast to prepare for
lactation & also stimulates the growth of uterus.

● Progesterone completes the stimulates the
development of mammary glands in breast by
estrogen & prepare for lactation.

● Progesterone also inhibits the contraction of uterine
muscles during end pregnancy.

● Estrogen level increases just before birth
● The level of progesterone decreases just before

birth
● Preparation for birth process

b) Explain the role of hormones during parturition/ birth process.

i. Progesterone,

ii. Estrogen,

iii. Oxytocin,

iv.Prostaglandin (CLO3)

ROLES OF HORMONES DURING DESCRIPTION
PARTURITION
1. During the last weeks of
pregnancy, estrogen level
increases

2. Stimulates the formation of
oxytocin receptor on the uterus.

3. Oxytocin is secreted by the fetus &
the mother’s posterior pituitary
gland.

4. Oxytocin stimulates the powerful
contraction of smooth muscle the
uterus & stimulates the placenta to
secrete prostaglandin which
enhance the contraction.

5. The physical & emotional stresses
of the mother stimulate the
production of more oxytocin &
prostaglandin by positive
feedback.

6. Contraction of uterus is rhythmic
and results in opening of the
cervix. To enhance more
contraction that push the baby out.

31

10 GROWTH

10.1 Define growth Size
Measurement of Biomass
How growth is
growth measured

GROWTH 10.2 Absolute growth 1. Lag phase
Type of growth curve
2. Log phase
10.3 Absolute growth
Growth pattern rate curve 3. Decelerating
(linear) phase

4. Plateau
(stationary)

phase

Limited growth
(annual plants)

Unlimited growth
(perennial plants)

Isometric growth (fish)

Allometric growth (human organs)

Intermittent growth curve
(arthropods)

LEARNING OUTCOMES:

At the end of this lesson, students should be able to explain:

10.1 Measurement of growth
a) Define growth (CLO 1)
b) Explain how growth is measured (CLO 3)

10.2 Type of growth
a) Explain absolute growth curve (CLO 3)
i. Lag phase
ii. Log phase
iii. Decelerating (linear) phase
iv. Plateau (stationary) phase
b) Explain absolute growth rate curve (CLO 3)

10.3 Growth pattern
a) Explain limited growth (annual plants) & unlimited growth (perennial plants) (CLO 3)
b) Explain isometric growth (fish) & allometric growth (human organs) (CLO 3)
c) Explain intermittent growth curve (arthropods) (CLO 3)

10.1 MEASUREMENT OF GROWTH

• Growth is an irreversible & permanent increase in size (length & width) & biomass of an organism over a
specific time.

• Growth can be measured by using a certain parameter over a period of time.
• Parameter chosen must be appropriate to the organism whose growth is to be measured.
• Example: height, appropriate for human but not trees (cannot measure growth of root).
• The measurement of growth is based on :

✓ Size
✓ Biomass

Measurement of Growth

Size Biomass

Wet Mass Dry Mass Lenght Width Height Volume Surface
area

Advantages • Easy & quick to be carried
• No need to kill the organism.

• Can be measured continuously
to observe growth.

SIZE Disadvantages • Measures in one or linear
BIOMASS dimension.

• Does not measure /consider
growth in other direction or
dimension.

1. WET MASS • Definition: Mass of an organism
under normal conditions that is
without removal of body water
content.

2. DRY MASS • Definition: Mass of an organism
after removing all its water
content from its body by drying
process.

WET MASS

ADVANTAGES DISADVANTAGES

 Easy to measure, requires little preparation of  Doesn’t measure true growth because it may give
the sample. inconsistent readings.

 Doesn’t cause injury to an organism.  Influenced & fluctuations in water content of the body

 Can be used to monitor growth of an
organism over a period.

 Can used the same organism for repeated
measurement.

DRY MASS

ADVANTAGES DISADVANTAGES

 Accurate measurement of the amount of  (Many) organisms must be killed.
organic matter present
 Growth of the same specimen can’t be measured
continuously.

 Need many genetically identical specimens grown
under similar condition to measure growth to obtain a
representative reflection of growth.

 Can’t be used to monitor growth of an organism over a
period.

 Time consuming.

DIFFERENTIATE BETWEEN DRY MASS & WET MASS

WET MASS DRY MASS

 Wet mass is mass of an organism under normal  Dry mass is mass of an organism after removing all

conditions that is without removal of body water its water content from its body by drying process.

content

 Wet mass can use the same organism for repeated  Dry mass growth of the same specimen can’t be

measurement measured continuously

 Wet mass doesn’t measure true growth because it  Dry mass gives accurate measurement of the

may give inconsistent readings & there is amount of organic matter present

influenced & fluctuations in water content of the

body

10.2 TYPES OF GROWTH CURVE

GROWTH CURVE

ABSOLUTE GROWTH CURVE ABSOLUTE GROWTH RATE CURVE

When a parameter is measured at intervals over a When an increase in size is measured over a series
period of time (through out the growth of an organism). of equal time intervals.

Produce S-shaped / sigmoid curve. Produce bell-shaped curve.

Absolute Growth Curve

• Most growth curve of organisms is sigmoid.
• It has S-shaped growth curve.
• Also known as actual / absolute growth curve.
• Growth starts slowly at first, then a rapid period of growth until reach maturity, growth begins to slow

down & stops.
• Have 4 phases:

✓ Lag phase
✓ Log / exponential phase
✓ Decelerating phase

✓ Stationary phase

1. Lag phase Absolute growth curve

2. Log / • Very slow growth
exponential • Occur due to :
phase
✓ Organism just try to adapt to new environment.
3. Decelerating ✓ Very few cells at initial stage.
phase
✓ These cells are actively dividing but actual increase in size is small.
4. Stationary
phase • Rapid growth or growth speed up exponentially.
• Cell divide & enlarge rapidly.
• A period when there is no constraints on growth due to:

✓ excessive nutrients
✓ enough space

✓ no accumulation of waste product / diseases

• Growth becomes slow down.
• A period when the growth becomes limited by internal or external factors or

both.
• Example of internal factors:

✓ maturity of organism,
✓ limited by genotype of an individual which determines a certain maximum

size.
• Example of external factors:

✓ limited food supply,
✓ not enough space due to competition.

• Constant growth.
• Cells are still dividing but only at a rate that replaces the dead cells
• The number of new cells formed is the same as the number of dead cells

(rate cell division = rate of cell mortality).
• Net growth rate is zero, size of organism remain constant during this phase.

Absolute Growth Rate Curve

• Bell-shaped curve.
• The steepest part of the curve shows the period where the growth is most rapid.
• At the peak of curve is inflection point.
• After inflection point, rate of growth decreases to zero as the adult / maximum size is achieved.
• Useful for showing:

✓ When growth is most rapid (the peak of the curve).
✓ how the rate of growth changes with time (the slope of the curve)

10.3 Growth Patterns

TYPES OF
GROWTH
PATTERNS

Limited Unlimited Isometric Allometric Intermittent
Growth Curve Growth Curve Growth Growth Growth Curve

Limited Growth Curve (Annual Plants)

• Definition : Refers to the growth of an organism until a steady maximum size is achieved.
• At this stage, growth is completed & they stop growing.
• Many organism has limited growth curve shown by only one sigmoid curve.
• Sigmoid curve is a growth average representing all organisms where young organism undergo

rapid growth.
• Followed by a continuous steady growth.
• Towards maturity, growth rate slows down (negative growth) until no growth occurs before death.
• Example of limited growth is in annual plants.
• An annual plant is a plant that completes its life cycle, from germination to the production of seed,

within one year, and then dies.

1)

2)

3)

4)

Unlimited Growth Curve (Perennial Plants)

• Definition : Refers to the growth of an organism that grow continuously throughout its life.
• Growth pattern consists of cumulative series of sigmoid curves.
• Each sigmoid curve represents 1 year’s growth.
• Each sigmoid curve can be divided into 4 parts (spring, summer, autumn and winter)
• E.g: woody perennial plants (plant living for more than two years)

• Description of 4 parts in each sigmoid :
 Spring – low temperature & light intensity, moderate rate of photosynthesis, small increase
in growth of plants.
 Summer – high temperature & light intensity, high rate of photosynthesis, large increase in
growth of plants.
 Autumn – the falling temperature in autumn reduces the rate of photosynthesis (moderate
rate of photosynthesis) & small increase in the growth of plants.
 Winter – Low rate of photosynthesis & minimum growth.

• The following season, the process is repeated.
• Overall, the annual growth patterns shows a series of sigmoid curves.
• An organism will continue to grow until it is restricted by environmental factors which killed the

organism such as:
✓ the presence of parasites
✓ natural predators
✓ outbreak of disease

Unlimited Growth Curve

Isometric Growth (fish)

• Isos: same; metron: measure
• Definition : Growth in which the various organs within an organism grow at the same rate as the rest

of the body.
• The organism increase in size without changing its shape.
• Its shape is consistent throughout development.
• The relative proportion of the organ & whole body remains the same.
• Example: fish
• Growth curve is typically sigmoid.

The relative proportions of any two structures are the same in a young & an adult.

Allometric Growth (human organs)

• Allos: other metron:measure
• Definition : Growth in which the various organs / parts within an organism grow at different rate as the

rest of body.
• As the size of organism increase, the shape will changes.
• Example : growth of human organ & tissues.
• In human : head, lymphoid tissue & reproductive organs grow at very different rate.
• Human organs and tissue are :

✓ Head
✓ Lymphoid tissue
✓ Reproductive organs

1. Head :
 The head grows rapidly in the first five years after birth & thereafter it does not grow much.
 The head & brain develop earlier than other parts of the body.
 As a result of allometric growth, the head of a baby is much larger relative to the rest of the body as
compared to an adult.

2. Lymphoid tissue
 The lymphoid tissue - produces white blood cells to overcome infection.
 Grows rapidly from birth to early adolescence.
 Because the risk of infection is high in early life, as immunity has not yet been acquired.
 After that, it the growth rate decreases to half its maximum size by adult stage.

3. Reproductive organs
 The reproductive organs grow slowly in early life but rapidly at puberty.
 Reproductive organ is the last organ to develop & differentiate (in most animals).