GROWTH
Growth is defined as an irreversible increase in volume, size, number of parts,
length and weight of an organism.
It is an organic process which takes some time to accomplish. Growth however
occur faster in young organisms than older ones.
The three processes involve in growth
CELL DIVISION
This is a process by which cell increases in number and is achieved by cell division
called mitosis. The division of cell commences with synthesis of new protoplasm
leading to the doubling of the chromosomes number in a process called replication
before cell actually divide into two, with each daughter cell having the same
chromosome as parent cell.
There are two types of cell division
(i)Mitosis which is a cell division that lead to growth
(ii)Meiosis is a cell division that lead to formation of gametes
CELL ENLARGEMENT
This is a process which follows cell division. After mitotic division in animals, the
daughter cells absorb nutrients from their surrounding which it uses to increase in
mass and size. Part of the nutrient is used for respiration to generate energy while
the remaining is assimilated resulting in the enlargement of the cells.
CELL DIFFERENTIATION
This process takes place after cell enlargement in which each cell develops into a
special type of cell by changing its shape and structure in order to carry out a
specialized or particular function. Cell differentiation is important in the growth
and development of a mature multi cellular organisms.
MITOSIS
Mitosis is a division of cell which produces two identical cells with the same
number of chromosomes and characteristics as those of the parent cell. Mitosis is a
cell division that lead to growth and it occurs in somatic cell(body cells) such as
skin, bone marrow, lymph nodes and injured places and meristimatic tissues of
plant. Mitosis occurs in five stages namely interphase, prophase, metaphase,
anaphase and telophase.
(i) Interphase- This is a resting stage of the cell: At this stage, the cell has
normal appearance of non-dividing cell condition. chromosomes are not
clearly visible.
, (ii) Prophase- The chromosomes become visible as chromatin threads. The
chromosomes become shorter, thicker and clearly visible. Each
chromosome now forms two district chromatrids joined by a centrometre.
Nucleolus is gradually disappearing and formation of spindle fibres
commence.
(iii) Metaphase- At metaphase the chromosomes (now paired) called
chromatids arranged themselves along the equator or middle of the
spindle. The chromatids are attached to the spindle by centrometre.
(iv) Anaphase- The chromatids of each chromosome separate. They start
migrating to the poles of the cell by elongation of the spindle axis. The
chromatids eventually reach the pole.
Growth is defined as an irreversible increase in volume, size, number of parts,
length and weight of an organism.
It is an organic process which takes some time to accomplish. Growth however
occur faster in young organisms than older ones.
The three processes involve in growth
CELL DIVISION
This is a process by which cell increases in number and is achieved by cell division
called mitosis. The division of cell commences with synthesis of new protoplasm
leading to the doubling of the chromosomes number in a process called replication
before cell actually divide into two, with each daughter cell having the same
chromosome as parent cell.
There are two types of cell division
(i)Mitosis which is a cell division that lead to growth
(ii)Meiosis is a cell division that lead to formation of gametes
CELL ENLARGEMENT
This is a process which follows cell division. After mitotic division in animals, the
daughter cells absorb nutrients from their surrounding which it uses to increase in
mass and size. Part of the nutrient is used for respiration to generate energy while
the remaining is assimilated resulting in the enlargement of the cells.
CELL DIFFERENTIATION
This process takes place after cell enlargement in which each cell develops into a
special type of cell by changing its shape and structure in order to carry out a
specialized or particular function. Cell differentiation is important in the growth
and development of a mature multi cellular organisms.
MITOSIS
Mitosis is a division of cell which produces two identical cells with the same
number of chromosomes and characteristics as those of the parent cell. Mitosis is a
cell division that lead to growth and it occurs in somatic cell(body cells) such as
skin, bone marrow, lymph nodes and injured places and meristimatic tissues of
plant. Mitosis occurs in five stages namely interphase, prophase, metaphase,
anaphase and telophase.
(i) Interphase- This is a resting stage of the cell: At this stage, the cell has
normal appearance of non-dividing cell condition. chromosomes are not
clearly visible.
, (ii) Prophase- The chromosomes become visible as chromatin threads. The
chromosomes become shorter, thicker and clearly visible. Each
chromosome now forms two district chromatrids joined by a centrometre.
Nucleolus is gradually disappearing and formation of spindle fibres
commence.
(iii) Metaphase- At metaphase the chromosomes (now paired) called
chromatids arranged themselves along the equator or middle of the
spindle. The chromatids are attached to the spindle by centrometre.
(iv) Anaphase- The chromatids of each chromosome separate. They start
migrating to the poles of the cell by elongation of the spindle axis. The
chromatids eventually reach the pole.
