Why does menstruation occur?
Menstruation occurs at the time of puberty in females. Menstruation occurs to prevent the pregnancy phase. It releases the tissues which supports the foetus to grow during the pregnancy. Menstruation is the bleeding phase, where an egg released by female does not get fertilized or attached to the uterine wall then uterine lining dies due to deficiency of hormone (progesterone), and the lining of fallopian tube breaks down and then the blood oozes out from the ruptured vessels through the vaginal opening.
Why is variation beneficial to the species but not necessarily for the individual?
Draw a labelled diagram of the longitudinal section of a flower.
What are the functions performed by the testis in human beings?
How will an organism be benefited if it reproduces through spores?
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Asexual reproduction takes place through budding in
(a) amoeba.
(b) yeast.
(c) plasmodium.
(d) leishmania.
How does the embryo get nourishment inside the mother’s body?
What are the advantages of sexual reproduction over asexual reproduction?
What is the importance of DNA copying in reproduction?
How does reproduction help in providing stability to populations of species?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
Find the focal length of a lens of power – 2.0 D. What type of lens is this?
Define 1 dioptre of power of a lens.
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Compare and contrast the arrangement of elements in Mendeléev’s Periodic Table and the Modern Periodic Table.
What changes can you make in your habits to become more environment-friendly?
What is a good fuel?
What is the difference between a reflex action and walking?