Biology Form 5 Chapter 4 - 4.6.Growth in multicellular organisms

1. 4.6
GROWTH IN
MULTICELLUL
AR
ORGANISMS

2. A series of changes in the life of an organism
–from zygote to adult – involves two major
processes:
(i) Growth
(ii) Development
Growth Phases
Introduction

3. Any irreversible and permanent increase in
quantitative parameters that can be measured
such as:
Growth Phases
Definition of Growth
size
length
volume
height
number
of cells
dry
masscytoplasmic
mass
surface
area

4. Any qualitative change and involve cell
differentiation:
Growth Phases
Definition of Development
shape
specificity
complexity

5. Growth
Involves 3 processes:
• Cell division – mitosis
• Cell elongation
• Cell differentiation

6. Growth Phases
1. Cell Division
• mitotic cell division in all somatic cells
• Through mitosis, the number of cells increase
exponentially – 1-2-4-8-16-32

7. Growth Phases
1. Cell Division
Plants – occurs in apical meristem (Root tip/shoot tip)
• Cells small, closely arranged, large nucleus
• Thin cell wall, no vacuole, dense cytoplasm

8. Growth Phases
2. Cell Elongation
 Plants - cells elongate & expand due to:Plants - cells elongate & expand due to:
-- absorption of water, into the cells by osmosis,, into the cells by osmosis,
- vacuoles increase in size- vacuoles increase in size
- small vacuoles fuse to form a large central vacuole- small vacuoles fuse to form a large central vacuole

9. Growth Phases
3. Cell Differentiation
• the cell
undergoes change
in shape
 in order to
perform specialized
functions - same set of
genetic information to
produce a diversity of cell
types

10. • e.g. : meristematic vascular cells
• the meristematic cells differentiate into:
 xylem: transportation of
water and minerals
 phloem: transportation of
products of photosynthesis and
hormones
Growth Phases
3. Cell Differentiation

11. GROWTH OF CELLS
CELL DIFFERENTIATION
Guard cell
and stomata
Mesophyll
cell
phloem xylem Parencymatous
cell of cortex

12. Growth Phases
Plants – In Root Tip
Three phases / zones:
1. Cell divisions
2. Cell elongation
3. Cell differentiation

13. THE GROWTH ZONE IN A PLANT SHOOT
Zone of cell division/
growth zone
Zone of cell
elongation
Zone of cell
differentiation
Matured tissue
Leaf
primordium
xylem
phloem
cambium
Apical meristem
-produces leaf primordium
which protects the
meristematic tissue
Axial bud
-containing cells which are
capable to divide to form
side branches.
1. Cell divisions
2. Cell elongation
3. Cell differentiation

17. • 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
/ / /
/ / / / / /
/ / / / /
/ / / /
/ /
Measuring Growth
Surface Area

18. the more appropriate parameters for the
measurement of growth in multicellular
organisms are the weight or mass
Measuring Growth
• fresh mass/weight
• dry mass/weight

19. • Periodic linear measurementPeriodic linear measurement
Eg: Measuring height for human being –
the best way to measure the growth of an
individual
Measuring Growth
Estimate length/ height

20. • the mass of the organism in the normalnormal condition
Measuring Growth
Fresh Mass
The advantages
• easier and convenient to measure
• no need to destroy the specimen
• the same organism can be used for repeated
measurement

21. The disadvantages
• inaccurate and inconsistent
• because it is affected by the fluctuation of
the amount of water in the organism
Measuring Growth
Fresh Mass
( water ~ 70 - 90% wet mass )

22. • the mass of the organism after its water
content is fully eliminated
Measuring Growth
Dry Mass: Definition
• it implies the actual growthactual growth of the organism

23. 1. The specimen is destroyed…
Measuring Growth
Dry Mass: Methods
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.

24. 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

25. 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

26. If an organism’s measurements (height,
weight, etc) are plotted against time, a
growth curve is obtained.
GROWTH
CURVE

27. Sigmoid Curve
Maturity
phase
Senescence
& death

28. GROWTH STAGES
1. Lag phase:
(a)The beginning of the growth process
(b)The rate of growth is generally low
(c)Cell division by mitosis takes place
very actively but there is no increase in cell size.
2. Exponential Growth:
a) The highest growth rate
b) Increase in the number of cells by mitosis
c) Cell size increases by absorbing water and addition of
protoplasmic substances.

29. 3. Maturity Stage
a) Growth rate is low
b) Cells achieve the optimum size(adult)
and there is no more increase in size of
the cell.
a) A little cell division to replace damaged cells
4. Stationary (Adult) Stage
a) Growth rate is zero
b) Cells still divide to replace damaged / dead cells
5. Senescence Stage
a) Growth rate is negative because of loss of tissues due to aging
process

30. HUMANS GROWTH CURVE
VIDEO

32. GROWTH CURVE OF A HUMAN

33. GROWTH CURVE OF A HUMAN
Time / year
Growth ( height/
weight)
At birth
Rapid growth
Slow growth
Very rapid growth
Very little
growth death
senescence
adult /Adolescence /
childhood
baby

34. GROWTH OF A BOY AND A GIRL
Rate of increase in height Kadar pertambahan berat
Age /
years
Height/cm
boy
girl
Freshweight
Rate of increase in weight
boy
girl
Age /
years

35. GROWTH CURVE OF
INSECTS
VIDEO

37. Grasshoppers moult (shed skin) 5 times from 1st
instar to adult

38. Growth curve of insects
– staircase shape

40. PRIMARY &
SECONDARY
GROWTH IN PLANTS

41. VIDEO

42. Growth in Plant

43. Meristem
Actively dividing tissue.
• Apical meristem: These are found at the
tips of roots and shoots and are
responsible for primary growth of the
plant. They increase its length.
• Lateral meristem:
• Cambium & Cork Cambium
• They are responsible for secondary
growth and cause an increase in girth

44. Primary & Secondary Growth
• All plants exhibit primary growth
• Woody plants also undergo secondary
growth (increase in girth wood)
• Herbaceous plants do not undergo
secondary growth

45. Primary Growth
• Primary growth leads to an increase in length
of the plant shoots or roots.
• It is due to the activity of apical meristems.
http://www.ucalgary.ca/~biolcore/biol233/plant5/apicalm
agon.seowon.ac.kr/~bioedu/bio/ohp/t-188.jpg
Root apical meristem (RAM)
Shoot apical meristem (SAM)

46. THE GROWTH ZONE IN A PLANT SHOOT
Zone of cell division/
growth zone
Zone of cell
elongation
Zone of cell
differentiation
Matured tissue
Leaf
primordium
xylem
phloem
cambium
Apical meristem
-produces leaf primordium
which protects the
meristematic tissue
Axial bud
-containing cells which are
capable to divide to form
side branches.

47. THE GROWTH ZONE IN A PLANT ROOT
Root hair
phloem
xylem
Matured tissue
Zone of cell division/
growth zone
Zone of cell
differentiation
Zone of cell elongation
cortex
Apical
Meristem
Root
cap

48. SECONDARY GROWTH IN
PLANTS
Secondary growth leads to the increase in thickness of a
plant. This is due to lateral meristems. (dicots only)
(perennial plants only)

49. Structure of Dicot Stem

50. Lateral meristem – vascular cambium & cork cambium
.Vascular cambium divides to form cambium ring.
.Cambium ring divides tangentially to form secondary xylem inside & secondary
hloem outside.
.Cork cambium divides to form cork outside.
.Lenticels develop to allow gaseous exchange between air & stem
.Primary xylem, phloem and pith are “squashed”. Epidermis ruptures.

53. Secondary Growth
Xylem
year 1
year 2
year 3
PithVascular
Cambium
Phloem
Cork
Cork Cambium
Note:
Xylem = wood
Cork, Cork cambium and
Phloem = bark
http://www.umanitoba.ca/faculties/science/biological_sciences/lab9/images/til
• Each year a new ring of xylem – produces a hard inner core
called wood
• Spring - fast growth – cells large, thin wall
• Autumn - slow growth – cells small , thick walls
• Light & dark rings – annual rings – calculate age of tree

54. Structure of Dicotyledonous Root

55. dicotyledonous root
Lateral meristem – vascular cambium & cork cambium
1.Vascular cambium divides to form cambium ring.
2.Cambium ring divides tangentially to form secondary xylem inside & secondary
phloem outside.
3.Cork cambium divides to form cork outside.
4.Primary xylem & phloem compressed.

57. THE END

58. Chapter review…Chapter review…
Growth
Growth phases
Growth curveGrowth curve
sigmoid human Secondary growth
(plants)
insects
Primary growth
(plants)
Growth
measurement
Wet/fresh
mass
Dry
mass
Definition
Phases of growth
Cell division
Cell enlargement
Cell differentiation