biology-class-12-unit-08-chapter-01-genetics-and-evolution-evolution-l-2-3-uaehdhfdejy

<div>
<h3 id="successwhat-is-natural-selectionsuccess"><Success>What is natural selection?</Success></h3>
</div>
<div style='float: left; width:100%;font-size:30px;text-align:left;'> 
<ul>
<li>
<p>It is the process whereby organisms better adapted to their environment tend to survive and produce more offspring</p>
</li>
<li>
<p>Why are certain organisms better adapted?</p>
</li>
<li>
<p>Due to variations which are inheritable and provide survival advantage</p>
</li>
<li>
<p>How does these variations occur?</p>
</li>
<li>
<p>Sexual reproduction leading to recombination during meiosis</p>
</li>
<li>
<p>Prolonged exposure to ionising radiations</p>
</li>
<li>
<p>Other atmospheric changes that produce changes either in genes/chromosomes or the germplasm</p>
</li>
</ul>
</div>

<div>
<h4 id="successbiological-evolution-by-natural-selectionsuccess"><Success>Biological Evolution by Natural Selection</Success></h4>
</div>
<div style='float: right; width:100%;'>
<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/219e78e2-bb59-4cf5-d399-c1847dc8c600/public" style='width:100%'>


</div>

<div>
<h3 id="successevidences-for-evolutionsuccess"><Success>Evidences for evolution</Success></h3>
</div>
<div style='float: left; width:100%;font-size:30px;text-align:left;'> 
<p><strong>Question</strong> Is Evolution real? How do we know it?</p>
<p>The evidences for evolution has come from various sources-</p>
<ul>
<li>Palaentology</li>
<li>Morphology and comparative anatomy</li>
<li>Embryology</li>
<li>Biochemistry</li>
<li>Connecting links</li>
<li>Missing links</li>
<li>Direct Observation of evolutionary processes</li>
<li>Anthropogenic Evolution</li>
</ul>
</div>

<div> 
<h3 id="successfossilssuccess"><Success>Fossils</Success></h3>
</div>
<div style='float: right; width:100%;'>
<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/1ef04df6-eeb6-4a7c-695b-95d834dfde00/public" style='width:60%'>

</div>

<div>
<h4 id="successevidences-from-morphology--anatomysuccess"><Success>Evidences from morphology & anatomy</Success></h4>
 </div> 
 <div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
<li>
<p><strong>Homologous organs</strong></p>
</li>
<li>
<p>Organs having common origin and built on same fundamental pattern, but perform different functions and have different appearance</p>
</li>
<li>
<p>These structures are obtained from a common ancestor and show evolutionary relatedness</p>
</li>
<li>
<p>Example - Structure of brain is similar from fishes to mammals</p>
</li>
</ul>
</div>

<div> 
<h3 id="successdivergent-evolutionsuccess"><Success>Divergent evolution</Success></h3>
</div> 
<div style='float: left; width:50%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>Also called adaptive radiation</p>
</li>
<li>
<p>The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography</p>
</li>
</ul>
</div>
<div style='float: right; width:50%;'>
<img src= "https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/fe0df800-adae-418b-7f8b-d799fbb80300/public" style='width:100%'>


</div>

<div> 
<h4 id="successadaptive-radiation-of-marsupials-of-australiasuccess"><Success>Adaptive radiation of marsupials of Australia</Success></h4>
</div> 
<div style='float: left; width:50%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>It give rise to homologous structures</p>
</li>
<li>
<p>Provides strong evidence in favour of organic evolution</p>
</li>
<li>
<p>Example Limb structure in mammals</p>
</li>
</ul>
</div>
<div style='float: right; width:50%;'>
<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/af725004-4b5f-40ba-2ae6-b2818f7c2900/public" width="100%">

</div>

<div>
<h3 id="successconnecting-linkssuccess-1"><Success>Connecting links</Success></h3>
</div>
<div style='float: left; width:50%;font-size:30px;text-align:left;'>
<p><strong>Peripatus</strong> Connecting link between annelida and arthropoda</p>
<p><strong>Missing links</strong> Transitional fossil forms showing characteristics of two different groups of living animals</p>
<p><strong>Seymoria</strong> missing link between amphibian and reptile</p>
</div>
<div style='float: right; width:50%;'>
<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/201d88cb-b743-4f4d-f2d2-5ba520ea9800/public" width="50%">
<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/6579e6c7-3730-4657-1d95-2df37cd85000/public" width="50%">


</div>

<div>
<h3 id="successconnecting-linkssuccess-2"><Success>Connecting links</Success></h3>
</div> 
<div style='float: left; width:50%;font-size:30px;text-align:left;'>
<p><strong>Missing Links</strong> Transitional fossil forms showing characteristics of two different groups of living animals</p>
<p><strong>Archaeopteryx</strong> missing link between reptile and bird</p>
</div>
<div style='float: right; width:50%;'>
<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/64411f3d-7e13-4c85-9d6a-e737bcda9400/public" width="100%">

</div>

<div> 
<h3 id="success-direct-observationsuccess"><Success> Direct observation</Success></h3>
</div>  
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<p><strong>Artificial Breeding Programme/Hybridisation</strong></p>
<ul>
<li>
<p>Man has bred selected plants and animals for agriculture and horticulture</p>
</li>
<li>
<p>Domestication of wild varities has also been done</p>
</li>
<li>
<p>The intensive breeding programme has created breeds that
differ from other breeds but still are of same group/species</p>
</li>
<li>
<p>What does this suggest?</p>
</li>
<li>
<p>If within hundreds of years, man could create new breeds, could not nature have done the same over millions of years?</p>
</li>
</ul>
<p><strong>Evolutionary change in beak shape of Darwin’s finches have been observed</strong></p>
</div>


</div>

<div> 
<h3 id="successanthropogenic-evolutionsuccess"><Success>Anthropogenic evolution</Success></h3>
</div> 
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>Industrial Melanism is one example of man made or anthropogenic evolution</p>
</li>
<li>
<p>Before Industrialisation → more white winged moths were present</p>
</li>
<li>
<p>After Industrialisation → more dark winged moths were observed</p>
</li>
<li>
<p>What had happened?</p>
</li>
<li>
<p>Before Industrialisation → tree trunks were light, thick growth of white lichen over the trunk, easy for white moth to camouflage</p>
</li>
<li>
<p>After Industrialisation → smoke and soot from Industries made barks dark in colour, lichens do not grow in polluted areas, dark winged moth or melanic moth could easily camouflage</p>
</li>
</ul>
</div>

<div> 
<h3 id="successlets-discusssuccess"><Success>Let’s discuss</Success></h3>
</div> 
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>Is it possible to have chemical evolution of life in the present conditions of earth?</p>
</li>
<li>
<p>No, it is not possible to have chemical evolution of new living forms today because the environmental conditions prevalent then and now has undergone sea change.</p>
</li>
<li>
<p>The primitive earth had conditions suitable to initiate chemical evolution of life as evident from Miller & Urey’s Experiment</p>
</li>
</ul>
</div>
<div style='float: right; width:0%;'>
<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-08-chapter-01-genetics-and-evolution-evolution-l-2_3-uaehdhfdejy-124-2890.8.jpg"></p>
<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-08-chapter-01-genetics-and-evolution-evolution-l-2_3-uaehdhfdejy-22.jpg"></p>
</div>

<div> 
<h3 id="successlets-discusssuccess-1"><Success>Let’s discuss</Success></h3>
</div>  
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<p>Do you agree that the rate of appearance of new forms is linked to the life cycle or life span of an organism How?</p>
<ul>
<li>
<p>Yes</p>
</li>
<li>
<p>We know that new forms arises out of the reproductive fitness gained from inherited advantageous variations (Natural Selection)</p>
</li>
<li>
<p>And in due course of time, the variant population outgrows the other forming a new species altogether over a period of time (speciation)</p>
</li>
<li>
<p>Organisms having shorter life span will show new forms within days as in bacteria. For the same thing to happen in fishes or fowls would take millions of years as their life spans are in years</p>
</li>
</ul>
</div>

<div>
<h3 id="successlets-discusssuccess-3"><Success>Let’s discuss</Success></h3>
</div>
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<p><strong>Differences between Darwinian variation and Hugo de vries’s Mutation</strong></p>
<table>
<thead>
<tr>
<th>Natural selection</th>
<th></th>
<th>Mutation</th>
<th></th>
</tr>
</thead>
<tbody>
<tr>
<td>Variations are small and directional</td>
<td></td>
<td>Mutations are random and directionless</td>
<td></td>
</tr>
<tr>
<td>Evolution is gradual</td>
<td></td>
<td>Single step large mutation called Saltation</td>
<td></td>
</tr>
</tbody>
</table>
</div>