Academic Year 2024-25

Grade -MYP 4

Unit 3: Life Processes

Key Concept: System Related concept:
Environment, Form, Function

Global context: Identities and relationships

Students will explore: moral reasoning and ethical judgment; consciousness and
mind

SOI: Systems of reproduction in the natural world have a variety of

different forms but support the same function to increase genetic
variation and continuity of life.

Background information:

Connection with SOI: Living organisms play a vital role in maintaining genetic
variation and ensuring the continuity of life through reproduction. Life cycles of
plants, insects, amphibians, and animals contribute to the ecosystem's balance and
diversity. Detection and response to stimuli through the nervous and endocrine
systems ensure survival and adaptation. Homeostasis and hormonal regulation
during pregnancy or excretion maintain internal stability, essential for thriving in
the natural world. Tropisms in plants further highlight the interconnectedness of
living organisms within ecosystems, fostering resilience and equilibrium.

Purpose: The following notes should be used by students for reference and
revision.

The notes explore the concept of different life cycles followed by living
organisms that help to maintain the natural world and continuity of life.

Life Cycle of a Plant:

• The plant starts life as a seed, which germinates and grows into a
plant.
• The mature plant produces flowers, which are fertilized and produce seeds
in a fruit or seedpod.
• The plant eventually dies, leaving seeds which germinate to produce
new plants.
• Annuals take one year to complete their life cycle.
• Biennials take two years to complete their life cycle, germinating and growing
roots and leaves in their first year, flowering, setting seeds and dying in their
second year. Perennials live for several years after germination.
• Monocarpic plants produce seeds only once but may take several years to
grow to maturity. The Talipot Palm may live for 60 years or more before it
produces flowers and seeds, and then it dies.

“Life Cycle of Plants - (Information + Fun Facts) - Science4Fun.” Science4Fun - Learn Science Experiments, Topics, Ideas and Activities, 14 Apr.
2018, science4fun.info/life-cycle-of-plants/.

To expand on this a bit, here’s the basic stepwise life cycle of a plant.

• A seed sprouts using the energy stored within it.

• The seedling grows into an adult plant. It grows leaves to catch sunlight
and collects nutrients from the soil.
• The plant produces flowers.
• The flower produces pollen, which travels through the air or is carried by
a pollinator like a bee. Some flowers contain both male and female parts
and can self-pollinate, but most plants rely on the wind or pollinators to
reproduce.
• This reliance on pollinators is why many flowers are bright and smelly –
that’s how they attract bees and butterflies!
• The pollen reaches another flower and fertilizes the ovules in that flower.
• The fertilized ovules swell into seeds within the protective structure of a
fruit.
• The fruit that falls is eaten or blows away.
• Plants have all sorts of creative ways to help their seeds travel far and
wide. Burs that stick to your pants, the white fluff of dandelions, and
tasty apples are all ways for the plant to move its offspring to new soil.
• Tasty fruits like acorns and oranges rely on animals to move them
around through poop or dropped morsels.
• The seed eventually makes its way to the soil, where the cycle starts
again.
• The life cycle of a plant takes different amounts of time for different
plants. Annual plants like violets take just a year to complete their life
cycle. Biennials, like mullein, take two years. They spend the first year
growing, and then produce flowers and seeds the next year. Perennials
like pine trees live for several years. And generally, they produce flowers
and seeds every year. Finally, monocarpic plants live for many years but
only produce seeds once.
• Some plants have other methods of reproducing. The banana plant, for
example, can also clone itself. “Daughter” shoots grow from the “mother”
stalk around the roots. This basic plant life cycle is just the beginning –
but it’s enough for most of us.

Life Cycle of an Insect:

Animals have a different kind of lifecycle.

A life cycle is the series of changes an animal goes through
during its life. Insects have fascinating lifecycles.
Some insects have a four-stage lifecycle. The insect lives as an
egg, larvae, pupa, and an adult.
Other shave a three-stage life cycle. The insect is born as an
egg, hatches as a nymph, and changes into an adult.

Egg
• Most insects lay their eggs near the food they like to eat. Moth sand
butterflies lay eggs underneath leaves.
• Dung beetles lay eggs in balls of animal poop. Many flies lay eggs on
meat. Some insects even lay eggs on other animals.
• Many insects make special cases to protect their eggs. Many insects lay
eggs in pools, ponds, or streams. Others lay their eggs underground.
Rarely, a female insect keeps the eggs inside her body. The eggs hatch,
and the young are born alive.
Source: “Butterfly Life Cycle: Article with Lots of Pictures.” Thebutterflysite.Com, 2019, www.thebutterflysite.com/life-
cycle.shtml.

Larva

Most eggs hatch into a worm-like stage called a larva.

Caterpillars, grubs, and maggots are larvae they have long bodies and
many legs. Almost all larvae are eating machines. A larva can eat more
than its own body weight in one day.
Many larvae can destroy crops. Some larvae suck sap from crop
roots. Others devour the leaves. Others eat fruits or vegetables. Beetle
larvae can weaken and kill trees. Some moth larvae eat wool clothing. On
the other hand, the silkworm, a moth larva, makes silk thread.

Source: “Butterfly Life Cycle: Article with Lots of Pictures.” Thebutterflysite.Com, 2019,
www.thebutterflysite.com/life-cycle.shtml.

Pupa

Once the larva has grown, it must totally change its shape. And it must
protect itself while it does so. Many larvae spin cocoons out of silk or
grow hard shells. The pupa does not move much. But inside, the insect
is very busy changing shape.
This change is called metamorphosis.

Metamorphosis:

Metamorphosis is a biological process by which animals,

including insects, amphibians and a few aquatic animals undergo
extreme and rapid physical changes someday after the birth. The effect of
metamorphosis modifies the entire body of an organism. These variations
include the maturation of enzymes, blood cells, the remodeling of the
nervous systems, digestive systems.
It is defined as the process in which an animal’s body structure
abruptly changes through cell growth and differentiation.

Source: Butterfly Life Cycle: Article with Lots of Pictures.” Thebutterflysite.Com, 2019, www.thebutterflysite.com/life-cycle.shtml.

Nymph
In the three-stage life cycle, eggs do not hatch as larvae. They
hatch as nymphs, which look like small adults. Some nymphs do not
have full wings. Others, such as the dragon fly nymph, may live under
water. Nymphs do not turn into pupae. Instead, they shed their skin as
they grow. Each time they shed their skin; they look more like an adult.
Slowly, the nymph transforms into an adult.
Source: “Butterfly Life Cycle: Article with Lots of Pictures.” Thebutterflysite.Com, 2019, www.thebutterflysite.com/life-
cycle.shtml.

Adult

After the metamorphosis is complete, the pupa hatches as an

adult. The adult insect has wings, six legs, and three body parts. Many
larvae that live in water will hatch into adults that live on land. Larvae
that live underground will hatch above the soil. Adult insects will find
mates, and the females will lay eggs. Sometimes, this is all the adults
do. Mayfly adults live for only one day. Most other insects have longer
adult lives. They eat, fly, hunt, and work.

Source: “Butterfly Life Cycle: Article with Lots of Pictures.” Thebutterflysite.Com, 2019, www.thebutterflysite.com/life-
cycle.shtml

Life cycle of an Amphibian:

Egg: The first stage is the egg stage. Eggs are usually laid in or near
water. A frog can lay thousands of eggs at once. The eggs are laid in large
groups. They are covered in jelly which makes them slippery. The jelly
protects them from other animals eating the eggs.
“Learn About the Stages in a Frog’s Life.” ThoughtCo, 2018, www.thoughtco.com/life-cycle-of-a-frog-130097. Accessed 16 July
2019.

Tadpole - The second stage is the tadpole stage. A tadpole hatches from
the egg. The tadpole breathes using gills and moves like a fish. It uses its
long tail to swim. Tadpoles eat tiny water plants.

“Learn About the Stages in a Frog’s Life.” ThoughtCo, 2018, www.thoughtco.com/life-cycle-of-a-frog-130097. Accessed 16 July
2019.

Froglet - The third stage is the froglet stage. It grows lungs and legs.
Its gills disappear. Its tail gets shorter until it disappears too. The froglet
swims to the top of the water to breathe air.

“Learn About the Stages in a Frog’s Life.” ThoughtCo, 2018, www.thoughtco.com/life-cycle-of-a-frog-130097. Accessed 16 July
2019.

Adult The last stage is the adult stage. A frog can leave the water now
and live on land. It eats insects, worms and snails. Mother frogs return
to the water to lay eggs.

“Learn About the Stages in a Frog’s Life.” ThoughtCo, 2018, www.thoughtco.com/life-cycle-of-a-frog-130097. Accessed 16 July
2019.

Guiding questions:

Q1. The sexual life cycle involves genetic contribution from both parents.
It involves meiosis for formation of gametes, fertilization and zygote
formation. This provides much greater genetic variation within a species.
There are many variations of sexual life cycles.

The following image describes different types of sexual life cycle in different
groups of organisms.

Analyze the following life cycle of different organisms and evaluate the
method of reproduction in each group of the named organisms.

Source: Life Cycle in Organisms. Digital image. N.p., n.d. Web. 6 Aug. 2018.<http://www.zo.utexas.edu/faculty/sjasper/images/13.5.gif>.

Q2. State the meaning of the term ‘Metamorphosis’.

Q3. Outline life cycle of an insect.
Q4. Outline how nymphs are different from other species of insects in
their life cycle.
Q5. Explain the life cycle of a flowering plant.
 Academic Year 2024-25
Grade -MYP 4

Unit: Life Processes

Key Concept: System Related concept: Environment, Form, Function

Global context: Identities and relationships

Students will explore: moral reasoning and ethical judgment; consciousness and mind

SOI: Systems of reproduction in the natural world have a variety of different

forms but support the same function to increase genetic variation and
continuity of life.

Background information:

 Connection with SOI: In order to maintain the ecosystem, genetic variation

and continuity of life needs to be maintained. This continuity is maintained
by living organisms through reproduction in the natural world that also leads
to variation in ecosystem to maintain the system properly.
 Purpose: The following notes should be used by students for reference and
revision.
 The notes explore the concept of sexual reproduction in animals that helps to
maintain the natural world and continuity of life by maintaining the variety of
species in ecosystem.
Sexual reproduction in animals:

Male reproductive system:

The male reproductive system is a combination of external and internal

organs present on the body of human beings identified as male.
These organs are different for male and female in human beings and are
concerned with the process of reproduction.
The male reproductive organ mainly consist of the testes, scrotum,
epididymis, vas deferens (sperm duct) seminal vesicles, prostate gland
and penis.
Video: https://www.youtube.com/watch?v=T8q3JpTWhrY&t=2s
Parts of male reproductive system and their functions:

1. Testis: Also called testicles they are a pair or oval shaped

organs responsible, or the production of sperms and a male
hormone called testosterone.
2. Scrotum: A loose, pouch-like organ that hangs below and
behind the penis. It maintains the temperature required for
sperm production and it also provides protection to the testicles.
3. Seminal vesicle: One of a pair of pouches attached to the
side of bladder. Its main function is to produce semen (a
thick liquid) that provides nourishment to the sperm cells.
4. Vas deferens: A long tube that connects the testes with
urethra. It is the sperm duct and transports the mature
sperms to urethra.
5. Urethra: It is the tube that carries urine and/or semen to the
outside of the body.
6. Prostrate: A gland that secretes fluid that is meant to protect
and nourish sperms.
7. Penis: It is the thick tube-like primary reproductive organ in the
male human body. It opens outside the body and has an opening
from which semen and urine pass out of the body.
8. Epididymis: A long coiled tube located at the backside or
each testicle. It transports and stores sperm cells produced in
the testes.
9. Urinary bladder: Urine produced by kidney flows down and gets
stored in the bladder It stores and controls its flow.

Source: Bioninja.com.au, 2021, ib.bioninja.com.au/_Media/male-front-labelled_med.jpeg.

Female reproductive system:

Video: https://www.youtube.com/watch?v=-5SOvWaW_OY

1. Ovary: Primary reproductive organ in the female. Ovaries are

the glands that produce the eggs and sex hormones (estrogen
and progesterone).

2. Fallopian tube: Also called oviduct, it is the narrow tube

close to the upper part or the uterus. The egg cells travel
from the ovaries to the uterus through the fallopian tubes.

3. Uterus: Uterus or the womb is the place where the fertilized egg
develops into a baby.

4. Cervix: This is a narrow strip or tissue that connects vagina

and uterus.

5. Vagina: Also called the birth canal. Vagina is a tube-like

structure that opens to the outside and is the opening
through which a baby comes out after it completes its
development in the uterus.

Source: https://images.everydayhealth.com/images/sexual-health/female-reproductive-
system-722x406.jpg?sfvrsn=f0fd2113_0
Reproductive System: Gamete Production:

Gametes are produced by a two-part cell division process called meiosis.

Through a sequence of steps, the replicated DNA in a parent cell is distributed
among four daughter cells.
Meiosis produces gametes with one half the number of chromosomes as
the parent cell. Because these cells have one half the number of
chromosomes as the parent cell, they are called haploid cells. Human sex
cells contain one complete set of 23 chromosomes.
When sex cells unite at fertilization, the two haploid cells become one
diploid cell that contains 46 chromosomes.
The production of sperm cells is known as spermatogenesis. This process
occurs continuously and takes place within the male testes. Hundreds of
millions of sperm must be released for fertilization to take place.
Oogenesis (ovum development) occurs in the female ovaries. In meiosis I of
oogenesis, daughter cells are divided asymmetrically. This asymmetrical
cytokinesis results in one large egg cell (oocyte) and smaller cells called polar
bodies. The polar bodies degrade and are not fertilized.
After meiosis II, the ovum fuses with the sperm cell, and fertilization is
complete.
The fertilized ovum is called a zygote.

Human fertilization and development:

Fertilization is the process in which haploid gametes fuse to form diploid cell
called a zygote. To ensure that each zygote has the correct number of
chromosomes, only one sperm can fuse with one egg.

Video: https://www.youtube.com/watch?v=5EvnCzOpy2o

Video: https://www.youtube.com/watch?v=tH1SJpg0DU8&t=12s

Stages of human development:

Zygotic stage: The zygote is formed when the male gamete (sperm) and female
gamete (egg) fuse.

Blastocyst stage: The single-celled zygote begins to divide into a solid ball of
cells. Then, it becomes a hollow ball of cells called a blastocyst, attaching to
the lining of the mother's uterus.

Embryonic stage: The major internal organs and external features begin to
emerge, forming an embryo. In this stage, the heart, brain, and spinal cord
become visible. Arms and legs start to develop.

Fetal stage: Once the formed features of the embryo begin to grow and
develop, the organism is considered a fetus. Differentiation and specialization
of structures happens during this time.
“Fertilization - Embryology.”
Unsw.Edu.Au,2019,embryology.med.unsw.edu.au/embryology/index.php/Fertilization.

Pregnancy and hormonal regulation:

Pregnancy is the time from fertilization of an egg, also known as conception,

to birth. Getting pregnant and growing a human from scratch is a very
complicated biological process that takes a lot of resources.
As a result, pregnancy can have a wide range of effects on the mother, both
physically and emotionally.
Each egg that is released during a menstrual cycle travel to your uterus.
However, unlike unfertilized eggs that proceed unaltered and then disintegrate
when they get there, a fertilized egg develops into a tiny human embryo on
the way. On reaching the uterus, the embryo implants itself in the uterine
wall, develops into a fetus, and steadily grows, until about nine months later it
is ready to emerge into the outside world as a newborn baby.

“Human Reproduction.” Leavingbio.Net, 8 Sept. 2019, leavingbio.net/human-reproduction/.

Menstrual cycle:

 Once every month or so (28 days), from the age of puberty, a woman's ovary
releases an egg cell. This process is known as ovulation.
 It occurs about 14 days after the start of the woman's last menstrual period.
The egg goes through the fallopian tube. This is where the egg cell is fertilized
by a man's sperm cell.
 Menstruation is when blood and tissue from the uterus comes out of the
vagina because the egg released during ovulation have not been fertilized.
 Video: https://www.youtube.com/watch?v=vXrQ_FhZmos
Source: Thereallife-Rd.com, 2021, www.thereallife-rd.com/wp-content/uploads/2018/04/Screen-
Shot-2015-12-14-at-8.09.54- pm.png. Accessed 16 Dec. 2021.

Hormonal changes that occur during pregnancy:

The menstrual cycle refers to the normal changes in your ovaries and uterus that
make an egg accessible for fertilization and prepare your uterus for pregnancy. It
typically occurs once every 28 days.
On ovulating normally, an egg, or ovum emerges from one or other of your
ovaries, leaving behind a structure called the corpus luteum. This structure
produces large amounts of progesterone and estrogen; hormones that help
prepare your uterus for implantation of a fertilized egg.
If the egg is not fertilized, the corpus luteum degenerates, causing
progesterone and estrogen levels to drop, and menstruation to begin. If the
ovum is fertilized, on the other hand, the corpus luteum remains intact and
continues to maintain the hormone levels you need to keep your uterus baby
friendly.
Eventually, the placenta develops the ability to secrete the necessary
hormones itself, and the corpus luteum typically disappears after 3 to 4
months.
In addition to progesterone and estrogen, human chorionic gonadotropin also
spikes in early pregnancy. The levels of this hormone double every two days in
the first 10 weeks of pregnancy. Its primary role is to prevent any further
menstruation, and to prepare the placenta - the organ that connects the
fetus to the uterus. The placenta allows the fetus to be supplied with
nutrients and oxygen, as well as providing a route for the removal of toxic
waste products.
“Human Reproduction.” Leavingbio.Net, 8 Sept. 2019, leavingbio.net/human-reproduction/.
Accessed 27 Sept. 2019.

Although many signs and symptoms of pregnancy are related to hormonal

changes, there are also many that occur due to the growing foetus invading
the spaces that were previously occupied by your other organs.

“Human Reproduction.” Leavingbio.Net, 8 Sept. 2019, leavingbio.net/human-reproduction/.

Guiding questions:

Q1. Explain how ovum/egg cell passes down to uterus.

Q2. Explain how the structure of the sperm cell enables it to reach to the

ovum.

Q3. State where each of the following is produced.

a. the egg cells.

b. the fertilized egg

c. the foetus

Q4. Describe the role of progesterone during the menstrual cycle and during
pregnancy.

Resources:

 SEER Training Modules, Introduction to the Reproductive System. U. S.

National Institutes of Health, National Cancer Institute. Accessed 24
January 2014 (http://training.seer.cancer.gov/anatomy/reproductive/)
 “Fertilization - Embryology.” Unsw.Edu.Au, 2019,
embryology.med.unsw.edu.au/embryology/index.php/Fertilization.
 Hormonal Control of Human Reproduction – Concepts of Biology-1st
Canadian Edition.” Opentextbc.Ca, 2019, opentextbc.ca/biology/chapter/24-
4-hormonal-control-of-human- reproduction/.