NOTES: - How do organisms reproduce?
Reproduction: is a biological process by which living organisms produces new
individuals similar to themselves. It ensures continuity of life on earth and helps in
evolution of species.
Advantages of Reproduction
● Reproduction ensures continuity of a particular species on earth.
● It creates genetic variation which leads to stability of a species.
● It helps in evolution of a species.
E:g; of evolution :- jaise ham monkey se human being ban gaye( aisa change joh
long time mein ho)
Q1) Evolution kyu ho rha hai?
Ans1) DNA copying ki wajah se.
DNA: (Deoxyribonucleic Acid) is thread-like structure that carries all information
about our traits and is passed from one generation to the next.
OR
A group of molecules that is responsible for carrying and transmitting the
hereditary materials or the genetic instructions from parents to offspring.
Significance of DNA Replication:
→ Preserves body structure.
→ facilitates the inheritance of traits.
→ Introduces diversity during the DNA replication process.
A basic event in reproduction is the creating of a DNA copy.
DNA copying is accompanied by the creation of an additional cellular
apparatus.
,DNA Copying Process Errors in copying (Biochemical reactions are
not fully reliable) Variations in DNA (DNA is not identical to the
original)
Extreme Variation ➔ new cell Mild/Moderate Variation ➔ No severe
Can’t function ➔ Cell dies consequences (Cell continues to function
. Normally)
Variations: Variations are the differences present between the individuals of the
same species or different species.
All sexually reproducing organisms show variations.
Some variations are Non – useful (like MOTH evolution)
Explanation:- Initially the color of the moth was like the color of the trees, so it
was not visible to anyone even while living on the tree, hence it was saved from
being eaten by any other creature. Gradual evolution took place, due to which the
color of the moth changed. ab It is visible on trees so other creatures eat it as
food.
Some variations are useful (like human evolution)
Importance/ Significance of Variation:
(i) Variation helps organisms adapt to changing environments.
(ii) It provides stability to a species and supports evolution.
(iii) DNA variation leads to different forms of a species and the creation of new
species.
Difference between Asexual and Sexual Reproduction
Asexual Reproduction Sexual Reproduction
Only single parent required. Two parents are required.
, No formation of gametes takes place formation of gametes takes
place(sperm in male ,egg in female)
Parents and offspring are identical to Parents and offspring may and may
each other. not similar but are not identical.
No variation takes place. There is variation in the next
generation.
Adopted by lower organisms. Adopted by higher organisms.
Example:- amoeba Example:- human being
Asexual reproduction is a mode of reproduction by which offspring arise
from a single organism and inherit the genes of that parent only. It does not
involve the fusion of gametes.
MODES OF ASEXUAL REPRODUCTION
Vegetative
Fission Budding Spore Formation Propagation
Fragmentation Regeneration
FISSION:-
A unicellular organism, such as bacteria, undergoes division into two or
more organisms. Generally categorized into two types, this process
Involves binary fission and multiple fission.
In fission, parent body divides into two or more daughter cells and each
one then grows into an adult organism.
Unicellular organisms such as protozoans (Amoeba, Paramecium, Euglena,
and Plasmodium) reproduce by this mode of asexual reproduction.
Types of Fission
, i. Binary fission
ii. Multiple fission
Binary fission
Binary fission involves the division of parent into two small, nearly
equal sized daughter individuals.
During binary fission nuclear division takes place first, followed by
the division of cytoplasm into two parts producing two daughter
organisms.
Binary fission occurs in unicellular protozoans like Amoeba,
Paramecium, Euglena, etc
Example:-
Binary fission in Amoeba:
Initially, the nucleus undergoes division into two, followed by
the division of cytoplasm. Ultimately, the parent cell splits into
two daughter cells.
Types of Binary fission
i. Longitudinal Binary fission
ii. Transverse Binary fission
iii. Irregular Binary fission
Reproduction: is a biological process by which living organisms produces new
individuals similar to themselves. It ensures continuity of life on earth and helps in
evolution of species.
Advantages of Reproduction
● Reproduction ensures continuity of a particular species on earth.
● It creates genetic variation which leads to stability of a species.
● It helps in evolution of a species.
E:g; of evolution :- jaise ham monkey se human being ban gaye( aisa change joh
long time mein ho)
Q1) Evolution kyu ho rha hai?
Ans1) DNA copying ki wajah se.
DNA: (Deoxyribonucleic Acid) is thread-like structure that carries all information
about our traits and is passed from one generation to the next.
OR
A group of molecules that is responsible for carrying and transmitting the
hereditary materials or the genetic instructions from parents to offspring.
Significance of DNA Replication:
→ Preserves body structure.
→ facilitates the inheritance of traits.
→ Introduces diversity during the DNA replication process.
A basic event in reproduction is the creating of a DNA copy.
DNA copying is accompanied by the creation of an additional cellular
apparatus.
,DNA Copying Process Errors in copying (Biochemical reactions are
not fully reliable) Variations in DNA (DNA is not identical to the
original)
Extreme Variation ➔ new cell Mild/Moderate Variation ➔ No severe
Can’t function ➔ Cell dies consequences (Cell continues to function
. Normally)
Variations: Variations are the differences present between the individuals of the
same species or different species.
All sexually reproducing organisms show variations.
Some variations are Non – useful (like MOTH evolution)
Explanation:- Initially the color of the moth was like the color of the trees, so it
was not visible to anyone even while living on the tree, hence it was saved from
being eaten by any other creature. Gradual evolution took place, due to which the
color of the moth changed. ab It is visible on trees so other creatures eat it as
food.
Some variations are useful (like human evolution)
Importance/ Significance of Variation:
(i) Variation helps organisms adapt to changing environments.
(ii) It provides stability to a species and supports evolution.
(iii) DNA variation leads to different forms of a species and the creation of new
species.
Difference between Asexual and Sexual Reproduction
Asexual Reproduction Sexual Reproduction
Only single parent required. Two parents are required.
, No formation of gametes takes place formation of gametes takes
place(sperm in male ,egg in female)
Parents and offspring are identical to Parents and offspring may and may
each other. not similar but are not identical.
No variation takes place. There is variation in the next
generation.
Adopted by lower organisms. Adopted by higher organisms.
Example:- amoeba Example:- human being
Asexual reproduction is a mode of reproduction by which offspring arise
from a single organism and inherit the genes of that parent only. It does not
involve the fusion of gametes.
MODES OF ASEXUAL REPRODUCTION
Vegetative
Fission Budding Spore Formation Propagation
Fragmentation Regeneration
FISSION:-
A unicellular organism, such as bacteria, undergoes division into two or
more organisms. Generally categorized into two types, this process
Involves binary fission and multiple fission.
In fission, parent body divides into two or more daughter cells and each
one then grows into an adult organism.
Unicellular organisms such as protozoans (Amoeba, Paramecium, Euglena,
and Plasmodium) reproduce by this mode of asexual reproduction.
Types of Fission
, i. Binary fission
ii. Multiple fission
Binary fission
Binary fission involves the division of parent into two small, nearly
equal sized daughter individuals.
During binary fission nuclear division takes place first, followed by
the division of cytoplasm into two parts producing two daughter
organisms.
Binary fission occurs in unicellular protozoans like Amoeba,
Paramecium, Euglena, etc
Example:-
Binary fission in Amoeba:
Initially, the nucleus undergoes division into two, followed by
the division of cytoplasm. Ultimately, the parent cell splits into
two daughter cells.
Types of Binary fission
i. Longitudinal Binary fission
ii. Transverse Binary fission
iii. Irregular Binary fission
