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Yogita Ingle 23 hours ago
The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen sensitive lymphocytes.
Bone marrow : Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are formed. Maturation of B-lymphocyte occurs here.
Thymus : Thymus is the site for T-lymphocytes maturation. Thymus is situated near the heart.
The secondary lymphoid organs are spleen, lymph nodes, tonsils,Payer's patches of small intestine and appendix.
Spleen : It is a bean-shaped organ which is the largest single mass of lymphoid tissue in the body. In foetus the spleen produces all type of blood cells but in adult it only produces lymphocytes.
Lymph nodes : These are small solid structures found at intervals along the lymphatic system. They are composed of lymphoid tissue and act as filters for the lymph. Lymph nodes also produce lymphocytes and plasma cells.
Tonsils : Usually there are only 6 tonsils. They act as filters to protect the body from bacteria and aid in the formation of white blood cells.
Peter's patches : They are clusters of lymph nodules found in small intestine along the ileum. They produce lymphocytes.
Mucosal-Associated Lymphoid Tissue (MALT) : MALT are significant aggregation of lymphoid tissues which are seen in relation to the mucosa of the major tracts like respiratory, alimentary canal and urinogenital tracts. It constitute about 50% of the lymphoid tissue in human body. They don't serve as filters of lymph. They are centres of lymphocytes production. Phagocytic macrophages and dendritic cells are also present.
Posted by Anuj Maurya 1 day, 4 hours ago
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Yogita Ingle 23 hours ago
Immune system consists of-
- Lymphoid organs
- Lymphoid tissues
- B- cells and T-cells
- Antibodies
Lymphoid organs-
The organs where origin and/or maturation and proliferation of lymphocytes occur are called lymphoid organs.
Lymphoid organs are of two types-
1. Primary lymphoid organs
2. Secondary lymphoid organs.
The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes.
The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.
<div class="google-auto-placed ap_container" style="width: 100%; height: auto; clear: none; text-align: center;"><ins class="adsbygoogle adsbygoogle-noablate" data-ad-client="ca-pub-1840315902857894" data-ad-format="auto" data-adsbygoogle-status="done" style="display: block; margin: auto; background-color: transparent;"><ins id="aswift_4_expand" style="display: inline-table; border: medium none; height: 0px; margin: 0px; padding: 0px; position: relative; visibility: visible; width: 955px; background-color: transparent;"><ins id="aswift_4_anchor" style="display: block; border: medium none; height: 0px; margin: 0px; padding: 0px; position: relative; visibility: visible; width: 955px; background-color: transparent; overflow: hidden; opacity: 0;"><iframe allowfullscreen="true" allowtransparency="true" frameborder="0" height="200" hspace="0" id="aswift_4" marginheight="0" marginwidth="0" name="aswift_4" onload="var i=this.id,s=window.google_iframe_oncopy,H=s&&s.handlers,h=H&&H[i],w=this.contentWindow,d;try{d=w.document}catch(e){}if(h&&d&&(!d.body||!d.body.firstChild)){if(h.call){setTimeout(h,0)}else if(h.match){try{h=s.upd(h,i)}catch(e){}w.location.replace(h)}}" scrolling="no" style="left:0;position:absolute;top:0;border:0px;width:955px;height:200px;" vspace="0" width="955"></iframe></ins></ins></ins></div>The thymus is a lobed organ located near the heart and beneath the breastbone.
Spleen, tonsil, lymph node, Peyer’s patches of small intestine and appendix are secondary lymphoid organs where proliferation of lymphocytes take place.
The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells.
The spleen is a large bean shaped organ mainly contains lymphocytes and phagocytes which acts as a filter of the blood by trapping blood-borne microorganisms and has a large reservoir of erythrocytes.
The lymph nodes are small solid structures located at different points along the lymphatic system.
Lymph nodes serve to trap the antigens and these antigens trapped are responsible for the activation of lymphocytes and cause the immune response.
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Gemmules are internal buds formed inside freshwater sponges, e.g. Spongilla. These are formed during unfavourable conditions and help in perennation and dispersal.
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Yogita Ingle 23 hours ago
Angiosperms are flower-bearing plants and are the most diverse group of terrestrial plants. The flowers form the reproductive part of angiosperms with separate male and female reproductive organs. Each contains gametes – sperm and egg cells respectively.
Pollination helps the pollen grains to reach stigma via style. The two sperm cells enter the ovule-synergid cell. This proceeds to fertilization.
In angiosperms, fertilization results in two structures, namely, zygote and endosperm, hence named, double fertilization.
Double fertilization is a complex process where out of two sperm cells, one fuses with the egg cell and the other fuses with two polar nuclei which result in a diploid (2n) zygote and a triploid (3n) primary endosperm nucleus (PEN) respectively.
Since endosperm is a product of the fusion of three haploid nuclei, it is called triple fusion. Eventually, the primary endosperm nucleus develops into the primary endosperm cell (PEC) and then into the endosperm.
The zygote becomes an embryo after numerous cell divisions.
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Source organism : Bacillus thuringlensis
Target pest : cotton ball worms
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Recombinant DNA technology involves several steps in specific sequence. These steps are as follows:
- Iisolation of DNA,
- Fragmentation of DNA by restriction endonucleases,
- Isolation of a desired DNA fragment,
- Ligation of the DNA fragment into a vector,
- Transferring the recombinant DNA into the host,
- Culturing the host cells in a medium at large scale
- Extraction of the desired product.
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CBSE syllabus for 2019-20 is now available for download in CBSE official website and myCBSEguide Mobile App.
For the latest syllabus of 19 - 20 click on the below link o my cbse guide to getan idea of deleted topics :
<a href="https://mycbseguide.com/blog/cbse-released-syllabus-for-2019-20/">https://mycbseguide.com/blog/cbse-released-syllabus-for-2019-20/</a>
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- A food chain is a series of organisms where all the organismsare dependent on next organism as a source of food.
- The series of organism take part at various biotic levels to form a food chain.
- Each step of the food chain forms a tropic level.
- The producers (green plants) are at the first tropic level.
- Primary consumers (herbivores) are at the second tropic level.
- Secondary consumers (small carnivores) constitute the third tropic level.
- Tertiary consumers (larger carnivores) form the fourth tropic level.
- Producers have the greatest number of individuals
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