Following are the two advantages of using unleaded petrol as fuel in automobiles:
i. Unleaded petrol does not have lead compounds therefore does not inactivate the catalytic converter.ii. It does not emit harmful compounds, thus causes less pollution and helps in preventing health diseases like bronchitis, asthma and lung diseases.
Why do moss plants produce very large number of male gametes? Provide one reason. What are these gametes called?
Mosses are bryophytes and they need water for fertilisation. During the transfer of male gametes, many of them are destroyed or lost. Thus, moss plants produce very large number of male gametes to compensate for the loss during transport.
These male gametes are called antherozoids.
Explain the different steps involved during primary treatment phase of sewage.
The primary phase of sewage treatment involves physical removal of particles by filtration and sedimentation.
Different steps involved during the primary treatment are as follows:
i. Initially, floating debris of sewage water is removed by sequential filtration.
ii. Then, grit (soil and small pebbles) are removed by sedimentation.Effluent (that is the supernatant formed when all the solids settle from the primary sludge) is then taken for secondary treatment.
How many chromosomes do drones of honeybee possess? Name the type of cell division involved in the production of sperms by them.
Drones of honey bees are haploid and possess 16 chromosomes.
Drones produce sperms by mitosis.
What is a cistron?
(a) Select the homologous structures from the combinations given below :
(i) Forelimbs of whales and bats
(ii) Tuber of potato and sweet potato
(iii) Eyes of octopus and mammals
(iv) Thorns of Bougainvillea and tendrils of Cucurbita
(b) State the kind of evolution they represent.
(a) Homologous organs or structures are those that are similar in anatomy or structure and have a common origin, but perform different functions.
From the given options, following are homologous structures:
i. Forelimbs of whales and bats are similar in structure but perform different functions of swimming and flying, respectively.
ii. Thorns of Bougainvillea and tendrils of Cucurbita are both modifications of a stem arising from axillary bud but perform different functions of protection (thorns) and climbing (tendrils), respectively.
(b) The evolution represented by homologous organs or structures is divergent evolution as they have a common origin but have diverged (became dissimilar) with time into different structures performing different functions.
(a) Why are the plants raised through micro-propagation termed as somaclones?
(b) Mention two advantages of this technique.
(a) The plants raised through micropropagation are called somaclones because they are genetically identical to the original plant from which they were grown.
(b) The advantages of micro-propagation are as follows:
(i) It helps in the propagation of a large number of plants in a short span of time.
(ii) It helps in recovery of healthy plants from diseased ones. It helps in producing plants that are disease and pest resistant.
Retroviruses convert their RNA into DNA by the method of reverse transcription, thus it is possible that the DNA of the infected host possesses DNA even when retroviruses do not have their own DNA.