GROWTH PATTERNS
a) sigmoid growth curve ( organism and population )
b) human growth curve
c) limited growth curve ( annual plants ) and unlimited
growth curve ( perennial plants )
d) isometric growth ( fish ) and allometric growth
( human organs )
e) intermittent growth curve ( arthropods )
22.3 Types of Growth Curves
Objectives
By the end of the lesson the students should
be able to:
give the types of growth curves
describe the types of growth curves
give the example of organisms which
growth pattern follow the growth curves
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Growth patterns
2
Sigmoid Growth Curves
• Organism that have a sigmoid growth
curve are:–Individual organism / large size of
multi cell plants / animals
–Microorganisms population ( yeast,
bacteria )
Growth patterns
Sigmoid Growth Curves
3
Growth Patterns
The Patterns
• patterns of growth vary from species to species
• the patterns of growth in living
multicellular organisms are:
human growth curve
allometric
vs.
isometric
limited
vs.
unlimited
Intermittent growth curve
1
human growth curve
Growth patterns
Human Growth Curves
• In human, the growth curve after birth
appears to consist of two sigmoid curves,
with two main rapid growth phases, the
infant phase and the adolescent phase.
• A slower growth phase is known as the
childhood phase can be found in between
these two rapid growth phases.
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Growth patterns
Human Growth Curves
infant phase
childhood phase
adolescent phase
A
C
D
B
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Growth patterns
Human Growth Curves
• Human growth curve:
i. Prenatal growth ( before birth )
ii. Postnatal growth ( after birth )
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Growth patterns
Human Growth Curves
Prenatal
growth
Postnatal growth
5
Prenatal growth
Growth patterns
Human Growth Curves
• In embryos, the brain and the head
will both start growth and
development together in the early
phase of life, while;
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Prenatal growth
Growth patterns
Human Growth Curves
• The complete development of
hands and feet only occurs in the
later phase.
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Postnatal
growth
Growth patterns
Human Growth Curves
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1. Infant phase:
Growth patterns
Human Growth Curves
•
Very rapid growth rate
•
Irrespective in both male
or female babies.
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2. Childhood phase :
•
•
•
Growth patterns
Human Growth Curves
growth rate is
slower.
beginning at the age
of four,
the rate is slightly
higher in boys than
in girls
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3. Adolescent
phase:
Growth patterns
Human Growth Curves
•
growth rate is rapid.
•
in the earlier part of
this growth phase,
females demonstrate
a more rapid growth
rate
•
i.e. two years earlier
than begins in males.
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3. Adolescent
phase:
Growth patterns
Human Growth Curves
•
At the later part of this
growth phase, the male
growth rate becomes higher
than the female growth rate.
•
This difference results in the
females attaining puberty at
an earlier age compared to
males.
•
Females attain puberty
around the age of 12, while
males attain puberty when
they are about 14 years old.
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4. Adult phase:
•
•
•
Growth patterns
Human Growth Curves
growth rate is zero
most individuals would have attained
maturity.
Males achieve this phase at the age
about 18 while females at the age around
16.
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5. Ageing phase
Growth patterns
Human Growth Curves
• growth rate is negative
• i.e. the body proportion will start to
decrease starting from the age of 30.
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Growth patterns
Human Growth Curves
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Growth patterns
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Limited Growth Curves
• The growth of an
organism to a
maximum fixed size,
which depends on the
type of the organism.
– Relative short life
span
Growth patterns
Limited Growth Curves
• Growth is complete
when the organism
achieves its
maximum size.
– and then
demonstrates the
negative growth,
senescence
• A single Sigmoid growth shape
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Growth patterns
Limited Growth Curves
• e.g. most plants and animals,
including human
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Growth patterns
17
Limited Growth Curves
Annual plant growth curve eg: Pisum sativum ( Pea plant )
Growth patterns
Limited Growth Curves
• In annual plants, the sigmoid growth
curve of dry mass versus time shows a
small reduction in dry mass in the initial
part of growth, due to seed germination.
• During germination, food stored in the
cotyledons is usually used up before the
first leaves undergo photosynthesis.
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Growth patterns
Limited Growth Curves
• This loss of mass is later replaced when the
first leaves develop and start photosynthesis.
• Later, growth rate is very rapid, until it
becomes constant at a later stage.
• This rapid growth rate is maintained until the
plant achieves maturity, after which the rate
gradually reduces until it becomes zero.
• e.g: pea plant
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Growth patterns
Unlimited Growth Curves
• Refer to non-stop growth
over a relatively long life
span
• Example organisms
demonstrate unlimited
growth:
• Obelia colonies,
• coral reefs and
• multiple season woody
trees
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Growth patterns
Unlimited Growth Curves
• The growth curve for unlimited growth comprises a
series of small sigmoid curves.
• This type of curve shows that there is an
increase in the mass and size every season.
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Growth patterns
Unlimited Growth Curves
• In plants that demonstrate unlimited growth,
there is no fixed rate and the growth
continues until enemies, natural
catastrophe or diseases cause destructive
effects on them.
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Growth patterns
Unlimited Growth Curves
Unlimited growth curve ( perennial plants )
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Growth patterns
Unlimited Growth Curves
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Allo= Gk. different
Growth Patterns
Allometric Growth
 The growth of an organism within which different
organs grow at different rates from each other and
from the overall growth.
• involves the change in size and external
shape/ features of the organism
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Allo= Gk. different
• involves the
change in size
and external
shape/ features
of the organism
Growth Patterns
Allometric Growth
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Growth Patterns
Allometric Growth
 It shows the correlation between the growth and
development of the organism
• e.g. in mammals: the growth rates of the
lymphatic and reproductive tissues is different
• i.e. the growth rates of both tissues are the
highest at the different stages of development
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Growth Patterns
Allometric Growth
• the mammalian lymphatic tissues
grows rapidly during the early
childhood years
• but during adolescence its
growth rate is lower, why?
• the mammalian reproductive tissues
grows faster during the stage of
adolescence, why?
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This is because lymphoid tissues are required by a young
individual to give it natural immunity and defense againts
disease.This function is less needed during the adult phase.
The reproductive system only starts to grow and
develop during the adolescent phase.
Similarly, in embryos, the brain and the head will both
start growth and development together in the early
phase of life, while the complete development of hands
and feet only occurs in the later phase.
Growth Patterns
Allometric Growth
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Growth Patterns
Allometric Growth
ALLOMETRIC GROWTH
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Growth Patterns
Isometric Growth
 The growth of an organism within the organs
grow at the same rates with the other parts of the
body.
• the relative size of the organs is constant
• i.e. the size of the organs increase, but the
external features remain the same
• e.g. fish, grasshoppers, cockroaches
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Growth Patterns
Isometric Growth
• not accompanied by a change in shape of the organism
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Growth Patterns
 e.g. in grasshoppers
Isometric Growth
• the relative proportion of the organs and whole body (size and shape
remain the same
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Growth Patterns
 e.g. in a cucumber leaf
Isometric Growth
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Growth Patterns
Intermittent Growth Curve
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• It is a discontinuous growth occurs in insects & other
arthropods metamorphosis.
• Growth is limited by the hard exoskeleton during certain
periods until the ecdysis / moulting process takes place.
• Then, growth occurs very suddenly at a rapid
pace.(rate of movement)
• Produces a step-like (intermittant) growth curve.
• Each stage in between ecdysis is known as instar.
Growth Patterns
Intermittent Growth Curve
 in arthropods e.g. insects
adult
Ecdysis @
5th instar
Ecdysis
3rd instar
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Growth Patterns
Intermittent Growth Curve
Ecdysis:
• also known as moulting
• a process of changing the old exoskeleton of
arthropods replaced with new soft layer and later
becomes harden again.
• occur periodically to allow growth and
development.
• during ecdysis, arthropod breathes in a lot of air
- body expands and break the old exoskeleton
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Growth Patterns
Intermittent Growth Curve
Ecdysis:
1. when old exoskeleton is removed,
2. arthropod once again breathing in more air to
increase it size before
3. newly formed layer of chitinious exoskeleton
hardens.
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22.5 Ecdysis and Metamorphosis
Ecdysis
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Growth Patterns
Intermittent Growth Curve
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Metamorphosis: Definition
• a process of changing in shape which occur
from one stage to the following stage in
animals (insect).
• two types: complete and incomplete
complete metamorphosis occur in
holometabolic insects e.g. housefly, butterfly
incomplete metamorphosis occur in
hemimetabolic insects e.g. cockroach
grasshopper
Complete Metamorphosis
larva
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Incomplete Metamorphosis
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