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.