Q25 of 44 Page 1

(a) How are polygenic inheritance and multiple allelism different ? Explain with the help of an example each.

(b) List the criteria a chemical molecule must fulfil to be able to act as a genetic material.


OR


State the hypothesis proposed by Oparin and Haldane. How was it experimentally proved by S.L. Miller ? Explain.


(a) Polygenic Inheritance: In this, traits are controlled by three or more genes (multiple genes). These traits are called polygenic traits. The phenomenon shows participation of each allele. Example: For example, human skin colour which is caused by a pigment melanin. The quantity of melanin is due to three pairs of polygenes (A, B and C). If a black or very dark (AABBCC) and white or very light (aabbcc) individuals marry each othe1, the offsprings show intermediate colour also called mulatto (AaBbCc).


Multiple allelism: When more than two alternative forms (allele) of a gene occupy the same locus on a chromosome in a population, these are known as multiple alleles. The ABO blood grouping is a good example of multiple alleles.


(b) The criteria basis which a chemical molecule can act as a genetic material are:


(i) It should be able to generate its replica or carry out replication.


(ii) It should chemically and structurally be stable.


(iii) It should provide the scope for slow changes or mutations essential for evolution.


(iv) It should be able to express itself in the form of 'Mendelian Characters’.


OR


Oparin and Haldane proposed the hypothesis that the first form of life might have come from pre-existing non-living organic molecules and that formation of life was preceded by chemical evolution. They said that the conditions on earth were – high temperature, volcanic storms, reducing atmosphere which contained CH4 (methane) , NH3 (ammonia), etc.


In 1953, this was experimentally proved by Miller who created similar conditions in a laboratory. He created electric discharge in a closed flask containing CH4 , H2 , NH3 and water vapour at 8000 degrees. He observed that amino acids were formed.



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23

Waste Disposal and Waste Management poses a major problem in present times. Generation of garbage and its disposal is a major threat and consequently leads to severe environmental issues. The problem is not with biodegradable and recycled wastes. We realise that the need is to reduce non-biodegradable wastes.

(a) Why is there a great concern of managing non-biodegradable waste in comparison to biodegradable waste ? Explain.


(b) As a member of eco club of your school, suggest any two ways that you will discuss with your fellow members to organise for a “Zero garbage day” once in a month in the school.


 24

(a) Identify the parts labelled 1, 2 and 3 in the diagram given.


(b) Draw a labelled diagram of a human blastocyst.


(c) What is parturition and how is it induced at the end of pregnancy in a human female ?


OR


(a) With labelled diagrams, depict stages in embryo development in a dicotyledenous plant.



(b) Endosperm development precedes embryo development. Why ?


 26

What does an Ecological Pyramid indicate ? Explain the three different types of upright Pyramids in nature with the help of an example each.

OR


(a) Indiscriminate human activities such as alien species invasion, fragmentation and habitat loss have accelerated the loss of biodiversity. Justify by taking one example for each.


(b) State the importance of (i) IUCN Red data list and (ii) Hot spots in conservation of biodiversity.


 1

Write the palindromic sequence that EcoRI recognises.