1. Growth and development
title
Growth and development

2. 21.1 What are growth and development?
content
21.1 What are growth and development?
21.2 How to measure growth changes?
21.3 Growth and development in plants
21.4 Growth and development in animals

3. 21.1 What are growth and development?
zygote
adult
grows
develops

4. by mitotic cell division
Growth
a non-reversible increase in size and weight of an organism
by mitotic cell division
results from
cell division
increase in cell number
increase in cell volume
cell enlargement

5. second mitotic cell division first mitotic cell division
Growth
cell division
second mitotic cell division
repeated divisions
first mitotic cell division
zygote
daughter cells
a ball of cells
cell enlargement

6. forming specialized cells to perform different functions
Development
an increase in complexity of the body organization
results from
forming specialized cells to perform different functions
differentiation of cells
into different types of cells
forming tissues, organs
and systems

7. Development cell differentiation
a cell in this region differentiates into e.g. a red blood cell
a cell in this region differentiates into e.g. a nerve cell
(newly formed red blood cell contains a nucleus)
cell differentiation
(mature red blood cells in humans contain no nucleus)

8. similar cells group together
tissue
other tissue(s)
tissue
different tissues group together
Three levels of structural organization are present in an organism
other organ(s)
organ
different organs group together
system

9. 21.2 How to measure growth changes?
By measuring :
Dry mass or dry weight
Fresh mass or fresh weight
Size
Choice of quantity depends on the type of organism.

10. Dry mass or dry weight the mass/weight with water removed
commonly used for plants

11. Dry mass or dry weight Advantage Disadvantages
Accurate measurement of the amount of organic matter in an organism
Time-consuming
Organisms killed, so growth of the same specimen cannot be measured continuously
Large number of specimens needed

12. Greater variation due to changes in environment or behaviour
Fresh mass or fresh weight
the mass without body water removed
Advantages
Disadvantage
Organism remains alive
growth can be measured continuously
Greater variation due to changes in environment or behaviour
Easy and quick

13. Size measurement of length/height, surface area or volume
for structures having a regular shape
for structures that grow mainly by elongation
for flat structures

14. Size Advantages Disadvantage Organism remains alive
growth can be measured continuously
Size is measured in one dimension, growth in other dimensions cannot be taken into account
Relatively easy and convenient

15. Size is measured in one dimension, growth in other dimensions cannot be taken into account

16. 21.3 Growth and development in plants
cells that can carry out mitosis throughout the plant’s life
Mitotic cell division of a plant
occurs in regions which have
meristems
e.g. apical meristem at the tip of a shoot/root

17. Growth and development at the root tip
Region of cell division
the cells divide mitotically to produce new cells
the cells formed earlier will be pushed further behind the root tip
region of cell division
dense cytoplasm with no vacuole
root cap
apical meristem

18. Growth and development at the root tip
Region of elongation
the cells enlarge by taking in water
region of elongation
smaller vacuole
thinner cell wall

19. Growth and development at the root tip
xylem vessel
larger vacuole
region of differentiation
thicker cell wall
root hair
Region of differentiation
the cells become specialized for performing different functions

20. Measuring growth of the main root of a seedling using ink
Carry out Practical 21.1
Measuring growth of the main root of a seedling using ink

21. Growth and development at the shoot tip
Growth in shoots is similar to that in roots.
young leaf
region of cell division (apical meristem)
region of elongation
region of differentiation

22. Growth curve of an annual plant
plant which lives for only one growing season 5 10 15 20 25 30 40 50
time (weeks)
dry mass (g)
3 stages
Dry mass decreases during early stage of germination
because the stored organic food is respired to provide energy for growth.

23. rate of photosynthesis
Growth curve of an annual plant 5 10 15 20 25 30 40 50
time (weeks)
dry mass (g)
Dry mass increases once the leaves are produced.
rate of photosynthesis
rate of respiration
>
food produced
food consumed
>

24. Growth curve of an annual plant
death 5 10 15 20 25 30 40 50
time (weeks)
dry mass (g)
Dry mass decreases
due to dispersal of fruits and seeds.

25. 21.4 Growth and development in animals
Plants
Animals
Cell division occurs only in regions that have meristem.
Cell division occurs in all parts of the body.

26. Growth curve of a human 5 stages infancy rapid growth rate childhood
adolescence
rapid growth rate
adult stage
old stage
Growth curve of a human

27. Change in body proportion from infancy to puberty
Growth curve of a human
with
Different body parts
Different growth rates
For example:
Relative size of head _________ with age.
decreases
Infancy
Childhood
Puberty
Infancy
Childhood
Puberty
Change in body proportion from infancy to puberty

28. Change in body proportion from infancy to puberty
Growth curve of a human
with
Different body parts
Different growth rates
For example:
Relative length of trunk ________________ with age.
remains the same
Infancy
Childhood
Puberty
Infancy
Childhood
Puberty
Change in body proportion from infancy to puberty

29. Change in body proportion from infancy to puberty
Growth curve of a human
with
Different body parts
Different growth rates
For example:
Relative length of legs _________ with age.
increases
Infancy
Childhood
Puberty
Infancy
Childhood
Puberty
Note that proportions change at different rates in boys and in girls.
Change in body proportion from infancy to puberty

30. Different organs also grow at different rates.
Growth curve of a human
Different organs also grow at different rates. 5 10 15 20 30 40 50 60 70 80 90
100
relative rate of growth
age (years)
brain
whole body
reproductive organs

31. Concept diagram Growth of organism size weight cell division
is the
non-reversible increase in
involves
size
weight
cell division
cell enlargement by
mitotic cell division

32. Development of an organism
Concept diagram
Development of an organism
results from
cell differentiation
leads to
increase in
variety of cell types
complexity of cells
form
form
tissues
organs
form
systems