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CHAPTER 10
GROWTH
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2
GROWTH
10.1
10.2
10.3
Measurement of Growth
Types of Growth Curve
Growth Pattern
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Learning outcomes
10.1At the end of this topic, students should be able to :
I. Define growth (C1)II. Explain how growth is measured
(C2)
Measurement of Growth
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Growth
Definition:
•An irreversible increase in size or biomass of anorganism over
time or•Any permanent and irreversible increase in
quantitative parameter over a specific timeMay continue
throughout the life of an organism or may
cease at maturity
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Measurement of Growth
Unicellular:
•When a unicellular organism reaches a certain size, itwill
divide to form two separate cellsResults in growth of their
populations
•Population growth of unicellular organisms can bemeasured
inchanges in cell numbers: direct cell countcounting number of
cells of a sample directly
under microscope
changes in cell mass
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Measurement of Growth
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Measurement of Growth
Multicellular:
•Growth can be measured at different biological levelssuch as
growth of a cell, organism or population
Population growth curve
Plotting the numbers of organisms in a
population against set intervals of time
Organism growth curve
Parameter of growth against set intervals of time
Parameters: biomass/wet mass/dry mass, length/height
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PARAMETER ADVANTAGES DISADVANTAGES
Height or lengthA periodic linear measurement
• Easier and quickto measure growth of a whole organism or part
of an organism
• Can be measured continuously
• Not suitable for plant because it measures the aerial position
of the plant
• Does not give much information about the growth of branches/
leaves/root
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PARAMETER ADVANTAGES DISADVANTAGES
Wet massThe mass of an organism in the normal condition
• Easier, convenient to measure
• Same organism can be used for repeated measurements
• Can be used to monitor growth of an organism over the period
of time
• Does not measure true growth
• Inaccurate/ inconsistent due to fluctuation of water in
organism
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PARAMETER ADVANTAGES DISADVANTAGES
Dry massThe mass of an organism after its water content is fully
eliminated
It is more accurate because it is not affected by water
content
• Organism is killedto remove thewater content
• Same organismcannot bemeasuredrepeatedly
• Requires a largeamount ofindividuals fromthe
samepopulation
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Learning outcomes
10.2At the end of this topic, students should be able to :
I. Explain absolute growth curve (C2)
II. Explain absolute growth rate curve (C2)
Types of Growth Curve
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Types of Growth Curves
Absolute Growth Curve
Absolute Growth Rate Curve
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• Also known as actual growth curve• Obtained by plotting the
parameters against time Parameter: mass, length Time: years,
hours
• Shows the overall growth• Sigmoid growth curve
Absolute Growth Curve
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• No growth or slow growth
• Little or no cell division and cell enlargement
• Organism try to adapt to new environment
Gro
wth
Par
amet
er
Time
Lag phase
Log phase
Decelerating / linear phase
Plateau / stationary phase
• Growth rate is maximum• Cell divide and enlarge rapidly as
conditions for
growth are at optimumAdequate nutrients and spaceNo accumulation
of waste products
• Growth begins to decrease/slow• Limited by internal or
external
factors or both
• Overall growth has ceased/stopped
• Cell division rate same as cell death rate
• Net growth rate equal to zero• Followed by senescence and
death
Absolute Growth Curve
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•Obtained by plotting the change in parameter against timeFrom
absolute growth curve
•The curve shows how the growth rate changes during the time of
study•Growth rate increases to a
maximum level initially and later falls until growth rate equals
zero.•Bell-shaped graph
Absolute Growth Rate Curve
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Learning outcomes
10.3At the end of this topic, students should be able to :
I. Explain limited & unlimited growth (C2)
II. Explain isometric & allometric(C2)
III. Explain intermittent growth curve (arthropods) (C2)
Growth Pattern
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Growth Pattern
Limited growth
Unlimited growth
Isometric Growth
Allometric Growth
Intermittent Growth
Growth pattern
