How are the modes for reproduction different in unicellular and multicellular organisms?
In unicellular organisms, asexual reproduction occurs where there is only one parent is involved and no gamete production or parthenogenesis occurs, where one parent cell gets divided into two or multiple daughter cells by binary or multiple fission (eg. Binary fission shown in bacteria, amoeba, planarians and multiple fission shown in plasmodium).
In multicellular organisms, sexual reproduction occurs where two parents are involved to form a zygote or parthenogenesis occurs. All mammals human beings, apes etc. show sexual reproduction process where mother shows viviparity, i.e, gives birth directly to the young ones.
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?
Why does menstruation occur?
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.
What are the advantages of sexual reproduction over asexual reproduction?
How does the embryo get nourishment inside the mother’s body?
What is the importance of DNA copying in reproduction?
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?
Show how you would connect three resistors, each of resistance 6 Ω, so that the combination has a resistance of (i) 9 Ω, (ii) 4 Ω.
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
What happens to the image distance in the eye when we increase the distance of an object from the eye?
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
What is the role of decomposers in the ecosystem?
What precaution should be taken to avoid the overloading of domestic electric circuits?
Find the power of a concave lens of focal length 2 m.
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?
State the principle of an electric generator.
Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) → 2Pb(s) + CO2(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and c
(iv) all