Transcript growth - study

Chapter review…
Growth
Growth phases
Growth rate
Growth
measurement
Definition
Wet/fresh
mass
Phases of growth
Absolute
growth curve
Dry
mass
Growth curve
Absolute
growth rate
curve
Cell division
Cell enlargement
sigmoid
human
Cell differentiation
intermittent
Limited (annual
plants)
Unlimited (perennial
plants)
Growth under extreme condition
Seed dormancy
hibernation
Aestivation
Diapause
Growth Phases
Objectives
By the end of the lesson the students should be
able to:
(i) define the term growth
(ii) name the three phases of growth
(iii) describe the three phases of growth
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Growth Phases
Introduction
A series of changes in the life of an organism
–from zygote to adult – involves two major
processes:
(i) Growth
(ii) Development
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Growth Phases
Definition of Growth
Any irreversible and permanent increase in
quantitative parameters that can be measured
such as:
size
surface
area
length
volume
cytoplasmic
mass
height
dry
mass
number
of cells
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Growth Phases
Definition of Development
Any qualitative change and involve cell
differentiation:
shape
specificity
complexity
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size
cytoplasmic
mass
Growth Phases
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Growth in Unicellular Organisms
 is controlled by the size of its
cytoplasm that is controlled by
its nucleus
 when achieve a certain size, it
divides to produce 2 daughter
cells of smaller size
 cell division is followed by the
growth of 2 daughter cells until
achieve the size of mature
unicellular organism
Growth Phases
Growth in Unicellular Organisms
differentiation is very limited in unicellular
organism
reproduce asexually through binary
fission for population growth to take place
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22.1 Growth Phases
Growth in Unicellular Organisms
1. Repeated divisions
• produce new daughter cells
• of smaller size
2. Limited growth
• i.e. equals to those of parent cells’
• also limited differentiation
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Growth Phases
Growth in Multicellular Organisms
Increase in
Changes
in
Size of organism
Appearance
heightthe complexity
Develop
Weight
function
and
of the
Physical characteristic
organism
Number of cells
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Growth Phases
Growth in Multicellular Organisms
Three phases:
3. Cell differentiation
2. Cell enlargement
1. Cell divisions
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Growth Phases
1. Cell Division
• The basic process in growth
• mitotic cell division in all somatic cells
• Through mitosis, the number of cells increase
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Growth Phases
1. Cell Division
• Gave the living world an opportunity to increase
the size of the organisms
• Rate of division depends on the cell types, the
species and other conditions – physical, chemical
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Growth Phases
2. Cell Enlargement
• the increase in the cell size
and volume
increase in the cytoplasmic
content,
e.g. number of organelles

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Growth Phases
2. Cell Enlargement
 Plants - cells grow by adding organic material to their
cytoplasm, or
- addition of water, into the large central
vacuole, accounts for 90% of plant cell’s
expansion
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Growth Phases
2. Cell Enlargement
 Animals - cells grow by synthesizing a
protein- rich cytoplasm,
a metabolically expensive process
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Growth Phases
2. Cell Enlargement
•
each cell grows to the
limit
the ability of the cell
nucleus to support the
increase in
cytoplasmic volume
•
the cell divides before it
reaches the limit
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Growth Phases
3. Cell Differentiation
• the cell
undergoes change
in form
 in order to
perform specialized
functions - same set of
genetic information to
produce a diversity of cell
types
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• the adult cell divides
repeatedly
resulting in a group of
cells
 the cells start to
differentiate from each
other in its structure and
chemical composition
Growth Phases
3. Cell Differentiation
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Growth Phases
3. Cell Differentiation
• e.g. 1: red blood cells
• in embryonic stages, in the cells destined
to be the blood tissue
• there’s an increase in the amount of
hemoglobin molecules and carbonic
anhydrase
disappearance of nucleus
enhance the ability for
transportation of O2 and CO2
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Growth Phases
3. Cell Differentiation
• e.g. 2: meristematic vascular cells
• the meristematic cells differentiate into:
xylem: transportation of
water and minerals
phloem: transportation of
products of photosynthesis and
hormones
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22.1 Growth Phases
Influential Factors
2 major factors of growth: extrinsic and
intrinsic:
in plants:
• extrinsic factors
light intensity, duration of light period,
temperature, humidity, water, soil and
minerals
in animals: nutrients, oxygen
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22.1 Growth Phases
Influential Factors
• intrinsic factors
in plants: plant hormones @ phytohormones
e.g. auxins, gibberillins, cytokinins
in animals:
hormone secretions of glands
e.g. hypothalamus, pituitary,
thyroid, gonads – promote or
inhibit growth in animals
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Measuring Growth
Objectives
By the end of the lesson the students should be able to:
(i) describe the methods in measuring growth
(ii) define the terms dry mass and wet mass
(iii) describe the advantages and the disadvantages
of measuring dry mass and wet mass of the
given specimens
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Measuring Growth
• Growth involves the increasing of
protoplasm of an organism.
• Growth can be estimated by measuring a
particular parameter over a specific time.
• The best parameter and commonly used to
measure growth are:- Biomass ( dry or fresh ) - Length
- Width
- Size
- Height
- Volume
- Number
- Surface Area
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Measuring Growth
Estimate length/ height
• Periodic linear measurement
Eg: Measuring height for human being –
the best way to measure the growth of an
individual
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Measuring Growth
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Estimate length/ height
• Periodic linear measurement
- Plant
• height is not a suitable
parameter
• the growth is measure by the
length of branches, size of
leave leaves, root and the
food storage structures
underneath the ground.
Auxanometer
Measure Length of stem
Measuring Growth
• Surface area of a leave
can be determine by
draw the outline of the
leave at a graph paper
or square paper (1cm x
1cm) and count the
square inside the leave
outline
• What is the surface are
for the leave?
 20 cm2
Surface Area
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Measuring Growth
the more appropriate parameters for the
measurement of growth in multicellular
organisms are the weight or mass
• wet mass/weight
• dry mass/weight
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Measuring Growth
Wet Mass
• the mass of the organism in the normal condition
The advantages
• easier and convenient to measure
• no need to destroy the specimen
• the same organism can be used for repeated
measurement
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Measuring Growth
Wet Mass
The disadvantages
• inaccurate and inconsistent
• because it is affected by the fluctuation of
the amount of water in the organism
( water ~ 70 - 90% wet mass )
• shows greater variation due to the environment
or the organism behavior
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Measuring Growth
Dry Mass: Definition
• the mass of the organism after its water
content is fully eliminated
• it implies the actual growth of the organism
• the actual growth is the change/increase in
the amount of other substances, apart from
water
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Measuring Growth
Dry Mass: Methods
1.
The specimen is destroyed…
2.
…then transferred into the oven at 110°C
to eliminate its water content.
3.
Next, it is put inside a desiccator to
ensure the water is completely eliminated.
4.
The dried specimen is weighed.
5.
The above procedures are repeated until
a constant value is obtained.
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Measuring Growth
Dry Mass
The advantages
• more accurate
• the amount of water in an organism is not
constant, i.e. depends on the water intake
by the individual organism
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Measuring Growth
Dry Mass
The disadvantages
• destruction of specimens
• in repeated measurement, specimens of the
similar age, size are required (destroyed!) to
avoid or minimize errors in the measurement
• Large samples of genetically identical organism
need to be grown under similar condition
• Time consuming
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