CHAPTER – 8
How do Organisms Reproduce
– Reproduction is the process by which living organisms produce new
individuals similar to themselves.
– Reproduction ensured continuity of life on earth.
– Reproduction - A bridge to hereditary transmission.
– It involves continuation of characters from the parents to daughter cells by
Copying of DNA (Deoxyribose Nucleic Acid) molecules present in the
chromosomes of the cell.
– Copying of DNAs is also not a foolproof exercise, even minute changes bring
about Variation in the blue print of the offsprings.
– The useful variations are retained while the harmful one does not go beyond.
– Actually variations help the species to withstand drastic environmental
changes, thus save the species from becoming extinct and promotes its
survival for a longer time.
– This inbuilt tendency of variation is the "fuel" for Evolution.
REPRODUCTION
Asexual Reproduction Sexual Reproduction
1. A single parent is involved 1. Both Parents involved
2. Gametes not formed 2. Gametes are formed
3. Progeny is Identical to parent 3. Progeny is only genetically
eg. Fission in Amoeba similar to the parent.
– Asexual Reproduction is extremely useful as a mean of rapid multiplication.
It is common in lower plants and animals.
– Different form of Asexual Reproduction.
1. FISSION : the parent cell divides/splits into two daughter cell-Binary
Fission; splits into many cells-multiple Fission
72 X-Science
, 2. BUDDING : A new organism is produced as an outgrowth of the parent
body part.
3. Spore Formation : Spores are
small, bulb like structure develops
at the top of the erect hyphae of the
fungus plant, released into the air
and germinate, into new
individuals after landing into food
or soil.
4. FRAGMENTATION : It is the accidental process when the broken pieces
of an organism (fragments) grows into a complete organism.
eg. fragmentation in
spirogyra
73 X-Science
How do Organisms Reproduce
– Reproduction is the process by which living organisms produce new
individuals similar to themselves.
– Reproduction ensured continuity of life on earth.
– Reproduction - A bridge to hereditary transmission.
– It involves continuation of characters from the parents to daughter cells by
Copying of DNA (Deoxyribose Nucleic Acid) molecules present in the
chromosomes of the cell.
– Copying of DNAs is also not a foolproof exercise, even minute changes bring
about Variation in the blue print of the offsprings.
– The useful variations are retained while the harmful one does not go beyond.
– Actually variations help the species to withstand drastic environmental
changes, thus save the species from becoming extinct and promotes its
survival for a longer time.
– This inbuilt tendency of variation is the "fuel" for Evolution.
REPRODUCTION
Asexual Reproduction Sexual Reproduction
1. A single parent is involved 1. Both Parents involved
2. Gametes not formed 2. Gametes are formed
3. Progeny is Identical to parent 3. Progeny is only genetically
eg. Fission in Amoeba similar to the parent.
– Asexual Reproduction is extremely useful as a mean of rapid multiplication.
It is common in lower plants and animals.
– Different form of Asexual Reproduction.
1. FISSION : the parent cell divides/splits into two daughter cell-Binary
Fission; splits into many cells-multiple Fission
72 X-Science
, 2. BUDDING : A new organism is produced as an outgrowth of the parent
body part.
3. Spore Formation : Spores are
small, bulb like structure develops
at the top of the erect hyphae of the
fungus plant, released into the air
and germinate, into new
individuals after landing into food
or soil.
4. FRAGMENTATION : It is the accidental process when the broken pieces
of an organism (fragments) grows into a complete organism.
eg. fragmentation in
spirogyra
73 X-Science
