Write notes on any three of the following, each with 2 to 3 important points (2½ marks each; total 7½): (a) Single-cell protein (b) tRNA (c) Ecological pyramid (d) Population density attributes (e) Sporulation (f) Outbreeding devices.

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> [!TLDR]
> Short notes (2-3 points each) are given below for all six topics; the question asks for any THREE of these, each worth 2½ marks.
>
> **(a) Single-cell protein (SCP)**
> - SCP refers to the dried cells of microorganisms (algae like *Spirulina*, bacteria, or yeast such as *Saccharomyces*) grown in bulk culture and used as a cheap, protein-rich supplement in animal feed and human food.
> - It is produced rapidly using inexpensive substrates (e.g., whey, molasses, agricultural waste) and helps meet the world's protein demand without requiring large areas of agricultural land.
> - Example: *Spirulina* is commercially cultured in large open ponds/bioreactors and marketed as a nutritional supplement.
>
> **(b) tRNA (transfer RNA)**
> - tRNA is a small, single-stranded RNA molecule folded into a characteristic clover-leaf secondary structure (L-shaped in 3-D), with an anticodon loop and an amino-acid-acceptor (CCA) end.
> - It acts as an **adaptor molecule**: its anticodon base-pairs with the complementary codon on mRNA, while its acceptor end carries the specific amino acid corresponding to that codon, thereby translating the nucleotide code into a polypeptide sequence.
> - Each of the 20 amino acids has one or more specific tRNAs (charged by aminoacyl-tRNA synthetase enzymes) that deliver it to the ribosome during translation.
>
> **(c) Ecological pyramid**
> - An ecological pyramid is a graphical, stepwise representation of the trophic structure of an ecosystem, with producers forming the base and successive consumer trophic levels stacked above.
> - There are three main types: pyramid of number, pyramid of biomass, and pyramid of energy. The pyramid of energy is always upright (energy always decreases at each successive trophic level, per the second law of thermodynamics), while number/biomass pyramids can sometimes be inverted (e.g., pyramid of numbers in a tree ecosystem).
> - It visually summarises how the amount of available energy/biomass/organisms

Q.Write notes on any three of the following, each with 2 to 3 important points (2½ marks each; total 7½):

Concept understanding — Microbes in Industrial Products

Q.Write notes on any three of the following, each with 2 to 3 important points (2½ marks each; total 7½):

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