Sample Paper Biology Class 12
Biology Unsolved Sample Paper Solutions ISC Class 12
(ix) (a) 5
A logistic (sigmoidal) growth curve has 5 phases. They are lag phase, log phase, deceleration phase, negative down acceleration phase, and stationary phase.
(x) (b) International Union for Conservation of Nature
The International Union for Conservation of Nature is an international organization working in the field of nature conservation and sustainable use of natural resources.
(xi) (d) heterotrophs
Decomposers are organisms that break down dead or decaying organisms to get energy. Decomposers speed up the decomposition process. Thus, they are heterotrophs.
(xii) (c) Assertion is true but Reason is false.
Plant-animal interactions involve co-evolution of mutualists. E.g.: evolution of flower and pollinator. Plants need animals for pollination and seed dispersal and animals get rewards like pollen, nectar and juicy fruits. They evolve side by side.
(i) In self-pollinated species the seeds are not formed because of self-incompatibility where there is no growth of pollen tube on the stigma of a flower that prevents the fusion of gametes and thereby developing into an embryo. Hence, in such species seed could not be formed.
A bioreactor is a vessel or a fermenter like an apparatus that is used to grow organisms such as bacteria or fungi under controlled environmental conditions e.g. pH, temperature, dissolved oxygen, etc. It can be used for the production of compounds of pharmaceutical importance, antibodies or vaccines.
A stirred tank reactor is cylindrical has a curved base that assists in the mixing of the reactor contents. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor. Alternatively, air can be bubbled through the reactor. The function of the agitation system is to provide good mixing and thus increase mass transfer rates through the bulk liquid. The agitation system consists of the agitator and the baffles that are used to break the liquid flow to increase turbulence and mixing efficiency.
Luteal phase is the period between ovulation and the onset of the next menstrual flow. It lasts for about 12-14 days (from 16th–28th day) of menstrual cycle.
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