NCERT Book Class 9 Science (Exploration) Chapter 3 Tissues in Action

Chapter
Tissues in Action
3

Life begins when a single cell divides itself several times to give
rise to a large number of cells. These cells gradually form the skin
(protection), muscles (movement), bones (support), nerves (control
Think It Over and coordination), and all other organs. This process is so intricate
that it is considered one of nature’s greatest engineering marvels.
y How is the study
of cells and tissues Researchers have been trying to understand, replicate and modify this
significant for process for human welfare. To do so, it is essential to understand the
understanding the natural biological processes that govern growth and development in
life processes and plants and animals. What makes cells group together to form tissues?
human welfare? Why do some tissues grow throughout life while others do not?
y How are tissues in In Chapter 2, Cell: The Building Block of Life, you have learnt that
plants and animals the cell is the basic unit of life. Many cells come together to form a
different, and why? multicellular organism. In all multicellular organisms, there is a
y How is the hierarchy of organisation. Cells of similar type performing similar
division of labour function group together to form a tissue, more than one type of tissues
at various levels
form organs, different organs form organ systems and organ systems
of organisation
in multicellular
form an organism. In unicellular organisms, such as amoeba, a single
organisms cell performs all functions of life. In multicellular organisms like plants
correlated with and animals, different groups of cells perform different functions. A
their structure and tissue is a group of cells (similar in structure) that work together to
function? perform a specific function. The formation of different types of tissues
leads to the division of labour, which increases the efficiency of the
body and enables it to carry out complex life processes. For example,