CBSE Class class-12 Biology — Very Short Answer Questions

Study the sequence of bases in a DNA molecule that is shown below and answer the questions. 5' – GAATTC – 3' 3' – CTTAAG – 5' (a) What are such sequences called? Name the enzyme used that recognises such nucleotide sequences. [1] (b) How do these enzymes function? [1]

(a) (i) How does a farmer use dormancy of seed to his advantage? [1] (ii) Differentiate between pea seed and castor seed. [1] OR (b) Identify the stage of follicle where primary oocyte undergoes first meiotic division. Also mention the products of this division. [2]

(a) Analyse the following two cases of sex determination in different organisms: Case I : Males have (XO) sex chromosomes and females have two copies of same sex chromosome (XX). Case II : Females have two different sex chromosomes (ZW) and males have two copies of same sex chromosome (ZZ). Identify the type of heterogamety in each case, giving one example of each. [1+1] OR (b) (i) Differentiate between a DNA and RNA nucleotide. [1] (ii) Name the two types of bonds present within a single nucleotide. [1]

(a) Given below is a pyramid found in an ecosystem, where each bar represents the standing crop available in the trophic level. [Diagram: an inverted ecological pyramid – a wide upper bar labelled 'PC' resting on a narrower lower bar labelled 'PP'.] (i) Identify the kind of pyramid and with the help of an example explain the conditions where this kind of pyramid is possible in nature. [1] (ii) Write any two limitations of ecological pyramids. [1] OR (b) In an ecosystem there was loss of biodiversity due to some project in that area. (i) How will biodiversity be affected? (2 points) [1] (ii) List two major causes of loss of biodiversity. [1]

(a) Define Humoral immune response. [1] (b) Name any two types of antibodies found to give humoral immune response in humans. [1]