BIO101 ‒ Topic 20: Growth and Development in Living Organisms
Course Code: BIO 101
Course Name: General Biology
© Lesuyai Organic Guides 2025
(Original ¦ Educational ¦ Professional ¦ Plagiarism-Free ¦ A4 Format)
20.1 Introduction
All living organisms undergo growth and development as they progress through their life cycle. Growth refers to
an irreversible increase in size or mass, while development involves qualitative changes in form, function, and
organization of cells, tissues, and organs. Together, these processes ensure survival, reproduction, and adaptation
of living organisms.
20.2 Definition of Growth and Development
Growth: A permanent and irreversible increase in size, mass, or number of cells in an organism.
Development: The series of changes that occur as an organism matures from a simple to a more complex and
functional form.
20.3 Characteristics of Growth
• Increase in cell number and size.
• Irreversible in living organisms.
• Requires nutrients and energy (metabolic process).
• Growth occurs in specific regions (e.g., root and shoot tips in plants).
• Growth follows a definite pattern or rate.
20.4 Measurement of Growth
Growth can be measured using physical or physiological parameters, depending on the organism.
In Plants:
• Increase in height, leaf area, root length.
• Increase in fresh or dry weight.
In Animals:
• Increase in body weight, height, or length.
• Changes in organ size.
Instruments Used:
• Ruler (length)
• Weighing balance (mass)
• Growth curve charts
20.5 Factors Affecting Growth
1. Internal Factors:
• Genetic makeup ‒ Determines growth rate and final size.
• Hormones ‒ Chemical messengers regulating growth and development.
Course Code: BIO 101
Course Name: General Biology
© Lesuyai Organic Guides 2025
(Original ¦ Educational ¦ Professional ¦ Plagiarism-Free ¦ A4 Format)
20.1 Introduction
All living organisms undergo growth and development as they progress through their life cycle. Growth refers to
an irreversible increase in size or mass, while development involves qualitative changes in form, function, and
organization of cells, tissues, and organs. Together, these processes ensure survival, reproduction, and adaptation
of living organisms.
20.2 Definition of Growth and Development
Growth: A permanent and irreversible increase in size, mass, or number of cells in an organism.
Development: The series of changes that occur as an organism matures from a simple to a more complex and
functional form.
20.3 Characteristics of Growth
• Increase in cell number and size.
• Irreversible in living organisms.
• Requires nutrients and energy (metabolic process).
• Growth occurs in specific regions (e.g., root and shoot tips in plants).
• Growth follows a definite pattern or rate.
20.4 Measurement of Growth
Growth can be measured using physical or physiological parameters, depending on the organism.
In Plants:
• Increase in height, leaf area, root length.
• Increase in fresh or dry weight.
In Animals:
• Increase in body weight, height, or length.
• Changes in organ size.
Instruments Used:
• Ruler (length)
• Weighing balance (mass)
• Growth curve charts
20.5 Factors Affecting Growth
1. Internal Factors:
• Genetic makeup ‒ Determines growth rate and final size.
• Hormones ‒ Chemical messengers regulating growth and development.
