Lesson: How do Organisms Reproduce?
What
is the importance of DNA copying in reproduction?
Chromosome contains information in DNA for
inheritance of features from parent to next generation. For an organism to
produce its own kind, it becomes necessary that the offspring should get DNA that
is similar to the parents. DNA replication is a way through which a cell makes
additional copies of DNA so that they can be transferred to the next
generation. So, DNA copying is an essential part of the process of reproduction.
Why is variation beneficial to the species
but not necessarily for an individual?
Variations are beneficial to a species as
variations help the species to adapt according to changes in external
environment. So, whenever there is a change in external environment, species ensure
required changes to ensure continuity of its life.
However, these variations may not happen in all
organisms of the same species.
For example, if the temperature of water increases
suddenly, then most of the bacteria living in that water may die. A few bacteria
that are more resistant to heat would be able to survive. However, in the
absence of these variants, the entire species of bacteria would have been
destroyed. Thus, these variants help in the survival of a particular species.
However, all variations are not necessarily beneficial for an individual
organism as not all individuals survive.
How does binary fission differ from
multiple fission?
In binary fission, a single cell divides into two
equal halves.
Example: Amoeba and Bacteria divide by binary
fission.
In multiple fission, a single cell divides into
many daughter cells simultaneously. Example: Plasmodium divides by multiple
fission.
How will an organism be benefited if it
reproduces through spores?
Advantages of spore formation:
·
Large
numbers of spores are produced in one sporangium.
·
Spores
can easily spread through water, air or animals and thus is good for the spread
of an organism to more places.
·
Spores
are covered by thick walls to prevent dehydration under unfavourable
conditions. So, a spore can remain dormant till favourable condition become
available.
Can you think of reasons why more
complex organisms cannot give rise to new individuals through regeneration?
The process of regeneration in simple organisms
involves the formation of new organisms from its body parts. Simple organisms
can utilize this method of reproduction as their entire body is made of similar
kind of cells in which any part of their body can be formed by growth and
development.
On the other hand, in complex organisms are made up
of different tissues and organs each having different structures. These organ
systems of a complex body, work together as an interconnected unit and perform
different functions. Through regeneration, different organs can redevelop certain
body parts such as muscles, blood, etc. but not new individuals.
Why is vegetative
propagation practised for growing some types of plants?
Vegetative
propagation is practised for growing some types of plants for the
following reasons.
a) It is useful to grow plants for which viable seeds are not formed or
very few seeds are produced.
b) It is a rapid and cheaper method of propagation.
c) It helps to introduce plants in new areas where
seed germination fails to produce mature plant due to changes in environmental
factors and soil.
d) It is useful to develop different traits of a
species of the same plant.
Why is DNA copying an essential part of
the process of reproduction?
Chromosome contains information in DNA for
inheritance of features from parent to next generation. For an organism to
produce its own kind, it becomes necessary that the offspring should get DNA similar
to their parents. DNA replication is a way through which a cell makes
additional copies of DNA so that they can be transferred to the next
generation. So, DNA copying is an essential part of the process of reproduction.
How is the process of pollination different from
fertilisation?
Pollination: Transfer of
pollen grains from the anther to the stigma is termed pollination. It is a
physical process in which pollen grains move due to certain physical factors
such as air, water, birds or some insects.
Fertilisation: Fusion of
male and female gametes is termed fertilization. The site of fertilisation is
ovule. The product of fertilization is zygote.
What is the role of the seminal
vesicles and the prostate gland?
The secretion from seminal vesicles adds fluid
content to the semen, which lubricates the sperms and provide a fluid medium
for easy transport of sperms.
The prostate gland makes the medium of semen
alkaline.
What are the changes seen in girls at the time of
puberty?
Changes seen in girls at the time of puberty are as
follows:
·
Voice
becomes thin
·
Increase
in breast size
·
Hair
growth under armpit and in pubic area
·
Beginning
of menstrual cycle
·
Increase
in the size of uterus and ovary
How does an embryo get nourishment inside a mother’s body?
After fertilization, a zygote is implanted in the uterine wall. The
lining of the uterine wall thickens to give support to the growing embryo. It
is richly supplied with blood to provide nourishment to the growing embryo. A
special tissue called placenta develops and connects the embryo to the uterine
wall to provide nutrients and oxygen to the embryo. Placenta contains villi on
the embryo’s side of the tissue, and blood spaces on mother’s side surrounding
the villi. This provides a large surface from mother to the embryo and waste
products from embryo to mother.
If a woman
is using a copper-T, will it help in protecting her from sexually transmitted
diseases?
No. Copper-T will not prevent the contact of body fluids. Therefore, it
will not protect her from sexually transmitted diseases.