| Class XII |
Biology |
Biology |
6 |
BIOLOGY CHAPTER 6 EVOLUTION 6.1 Origin of Life 6.2 Evolution of Life Forms - A Evolutionary Biology is the study of history of life forms Theory on... |
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| Class XII |
Biology |
Biology |
6 |
formed sometime later. The gases condensed under gravitation and formed the galaxies of the present day universe. In the solar system of the milky ... |
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| Class XII |
Biology |
Biology |
6 |
of amino acids. In similar experiments others observed, formation of sugars, nitrogen bases, pigment and fats. Analysis of meteorite content also r... |
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| Class XII |
Biology |
Biology |
6 |
different periods of history of earth. There has been gradual evolution of life forms. Any population Reprint 2026-27 EVOLUTION hasbuiltinvariation... |
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| Class XII |
Biology |
Biology |
6 |
study showed that life-forms varied over time and certain life forms are restricted to certain geological timespans. Hence, new forms of life have ... |
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| Class XII |
Biology |
Biology |
6 |
whereas analogy refers to a situation exactly Tendril opposite. Wings of butterfly and of birds look alike. They are not anatomically similar struc... |
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| Class XII |
Biology |
Biology |
6 |
a contrasting background’. During postindustrialisation period, the tree trunks became dark due to industrial smoke and soots. Under this condition... |
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| Class XII |
Biology |
Biology |
6 |
finches represent one of the best examples of this phenomenon. Another example is Australian marsupials. A number of marsupials, each differentfrom... |
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| Class XII |
Biology |
Biology |
6 |
in an otherwise hostile environment. Adaptive ability is 118 inherited. It has a genetic basis. Fitness is the end result of the ability to adapt a... |
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| Class XII |
Biology |
Biology |
6 |
the fact that population sizes in reality are limited, means that there had been competition for resources. Only some survived and grew at the cost... |
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| Class XII |
Biology |
Biology |
6 |
equilibrium. Sum total of all the allelic frequencies is 1. Individual (a) (b) 120 (c) Figure 6.8 Diagrammatic representation of the operation of n... |
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| Class XII |
Biology |
Biology |
6 |
Natural selection is aprocessinwhichheritablevariationsenablingbettersurvivalareenabled to reproduce and leave greater number of progeny. A critica... |
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| Class XII |
Biology |
Biology |
6 |
amphibians evolved into reptiles. They lay thickshelled eggs which do not dry up in sun unlike those of amphibians. Again we only see their modern ... |
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| Class XII |
Biology |
Biology |
6 |
language skills and self-consciousness. A rough sketch of the evolution of life forms, their times on a geological scale are indicated in (Figures ... |
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| Class XII |
Biology |
Biology |
6 |
district of Madhya Pradesh. Agriculture came around 10,000 years back and human settlements started. The rest of what happened is part of human his... |
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| Class XII |
Biology |
Biology |
6 |
Describe one example of adaptive radiation. 9. Can we call human evolution as adaptive radiation? 10. Using various resources such as your school L... |
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| Class XII |
Biology |
Biology |
7 |
Chapter 7 Biology is the youngest of the formalised disciplines of natural Human Health and Disease science. Progress in physics and chemistry proc... |
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| Class XII |
Biology |
Biology |
7 |
This is what early Greeks like Hippocrates as well as 7.4 Cancer Indian Ayurveda system of medicine asserted. It was thought that persons with ‘bla... |
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| Class XII |
Biology |
Biology |
7 |
is adversely affected, characterised by appearance of various signs and symptoms,wesaythatwearenothealthy,i.e.,wehaveadisease.Diseases can be broad... |
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| Class XII |
Biology |
Biology |
7 |
to spread typhoid for several years through the food she prepared. Bacteria like Streptococcus pneumoniae and Haemophilus influenzae are responsibl... |
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| Class XII |
Biology |
Biology |
7 |
is responsible for the chill andhighfeverrecurringeverythreetofourdays.WhenafemaleAnopheles mosquito bites an infected person, these parasites ente... |
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| Class XII |
Biology |
Biology |
7 |
filariasis (Figure 7.2). The genital organs are also often affected, resulting in gross deformities. The pathogens are transmitted to a healthy Fig... |
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| Class XII |
Biology |
Biology |
7 |
on mosquito larvae, spraying of insecticides in ditches, drainage areas and swamps, etc. In addition, doors and windows should be provided with wir... |
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| Class XII |
Biology |
Biology |
7 |
epithelium lining the respiratory, gastrointestinal and urogenital tracts also help in trapping microbes entering our body. (ii)Physiological barri... |
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| Class XII |
Biology |
Biology |
7 |
types of our acquired immune response – antibody mediated. The second type is called 135 cell-mediated immune response or cell-mediated immunity (C... |
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