NCERT Book Class 9 Science (Exploration) Chapter 2 Cell: The Building Block of Life

Chapter
Cell: The Building
2 Block of Life

It is widely accepted amongst the scientific community that life
originated in water. Some researchers believe that life may have
originated in small water pools with changing environmental
Think It Over conditions rather than in the oceans. Hot springs are examples
of such environments. In India, the hot springs of Puga Valley in
y Where does a cell Ladakh maintain very high temperatures (nearly at the boiling
come from? point of water) even in a cold climate. These environmental
y How have conditions seem to be similar to those on the early Earth, about
technological 3.5 billion years ago. The organisms living in these hot springs
interventions are mostly heat-loving bacteria called thermophiles, which are
facilitated the
unicellular.
creation of new
knowledge in Scientists from the Birbal Sahni Institute of Palaeosciences,
understanding the Lucknow, studied these hot springs and found that calcium carbonate
world beyond the formed rapidly around them. These deposits may have protected
naked eye? early organic molecules from harmful radiation and extreme
y How is the cell conditions, and they may have also helped in the formation of the
structural and first protective membrane — the barrier that defines a cell.
functional unit of
life? All living organisms are made up of cells. The cell represents the
basic level at which life exists. Some organisms, such as bacteria or
y How does a cell
multiply? yeast consist of only one cell (unicellular), while others like plants,
fish, birds or humans are made up of millions of cells (multicellular)
that work together. A group of similar cells performing similar