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ISC Class 12 Biology Solved Question Paper 2014

Long Answer Type

21.

(a) Mention the important features of the Neanderthal man.
(b) What are homologous organs? How do they help in providing evidence for organic evolution?

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22.
a. Describe the different types of vascular bundles.
b. Give three anatomical differences between a monocot root and a dicot root.
c. Explain the effect of light and temperature on photosynthesis.

(a)
1) Radial Vascular Bundle: In these, the xylem and phloem are arranged in different radii / alternative with each other.

2) Conjoint Collateral: Xylem and phloem are present on the same radius. Phloem located on the outer side of the xylem. (Open and closed types).

3) Conjoint Bicollateral: Phloem and cambium on the outer and inner side of the central xylem / central xylem with outer phloem outer cambium and inner phloem inner cambium.

4) Concentric: One type of vascular bundle surrounded by the other. (Amphicribal– Phloem surrounds xylem and Amphivasal (leptocentric) – xylem surrounds phloem).

Monocot root	Dicot root
Cambium is absent	Cambium appears at the time of secondary growth.
Pith is well developed	Pith is small or absent
Vascular bundles are numerous	Vascular bundles are numerous

c. Effect of light on photosynthesis:
i. High light intensity may become inhibitory as they bring about photo-oxidation/solarisation of chlorophyll. Reduce turgidity and close stomata.
ii. Different wavelengths influence photosynthesis differently. Green is least effective, blue and red regions are most effective.
iii. Increase in light and intensity up to a certain limit increases the rate of photosynthesis.
iv. Intensity of light affects the rate of photolytic reaction and controls the rate of ATP and NADP production.

Effects of temperature on photosynthesis.

Temperature:

i. Increase in temperature up to a certain optimum, increases the rate of photosynthesis.

ii. Low temperatures inhibit the rate of photosynthesis by declining CO2 diffusion rates or directly affecting enzymatic action / photosynthesis stops at 40C.

iii. Optimum temperature for photosynthesis ranges between 30 C and 35 C.

iv. High temperature increases transpiration, wilting of leaves / stomatal closure – affects photosynthesis.

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23.

(a) Explain the transpiration pull theory for ascent of sap.
(b) Explain the process of spermatogenesis in humans.
(c) Define the following:
(i) Placentation
(ii) Parthenocarpy
(iii) Diffusion

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24.

(a) Why are xylem and phloem classified as complex tissues? Describe the structure of phloem.
(b) Describe the ultra-structure of chloroplast.
(c) State three functions of the placenta.

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25.

(a) Describe the experiment performed by Griffith. What conclusions did he infer from his observations?
(b) What is artificial insemination? Mention two ways in which it is useful in breeding of dairy animals.
(c) What is single cell protein? Give its source and significance.

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26.

(a) How did Hershey and Chase prove that DNA is the genetic material?
(b) Give one main application of each of the following:
(i) MRI
(ii) Ultrasound
(iii) ECG
(c) Explain the role of stem cells in medical treatment.

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27.

(a) Write short notes on:
(i) Multiple Alleles
(ii) Artificial measures to control population
(b) What complications will arise if the blood of an Rh positive person is transfused to an Rh negative person and vice versa?
(c) State any three goals of the human genome project.

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