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Lesson Posted on 11 Sep CBSE/Class 11/Science/Biology

Endosperm of Gymnosperms

Vinay

I believe in clearing the concepts of students. I can help you build a strong foundation. Doubts will...

In Gymnosperms seed are not covered as an ovary does not enclose the ovule. Ovarian wall =friut wall (after fertilisation) Ovule has nucelus(2n) nutririvn tissue and one integument. One cell of nucleus get modified, and form Megaspore mother cell (2n) which by meiosis form 4 megaspore(n), 4 out of... read more

In Gymnosperms seed are not covered as an ovary does not enclose the ovule.

Ovarian wall =friut wall (after fertilisation)

Ovule has nucelus(2n) nutririvn tissue and one integument.

One cell of nucleus get modified, and form Megaspore mother cell (2n) which by meiosis form 4 megaspore(n), 4 out of 3 disintegrate and one remain functional.

Functional Megaspore germinates inside ovule and forms female gametophyte(n).

Female gametophyte has Archegonia with egg. After pollination (anemophily;wind) fertilisation takes place. The egg develops into zygot-embryo-seed (2n).

The persistent female gametophyte (n) is now called endosperm. Therefore it is haploid(n).

Gymno seed = three generations ( persistent nucleus is parent sporophyte, the endosperm is persistent gametophyte and embryo is future sporophyte).

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Asked on 12 Aug CBSE/Class 11/Science/Biology

%3Cp%3E1.%20Economic%20importance%20of%20animals%202.%20Economic%20importance%20of%20plants.%20Comes%20in%20which%20chap... read more
%3Cp%3E1.%20Economic%20importance%20of%20animals%202.%20Economic%20importance%20of%20plants.%20Comes%20in%20which%20chapter%20of%20ncert%20biology%20book%3C%2Fp%3E read less

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Asked on 12 Aug CBSE/Class 11/Science/Biology

Economic importance of animals and plants comes in which chapter of biology

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Lesson Posted on 26 Jul CBSE/Class 11/Science/Biology

Nervous system in human.

Sashankar Ray

"A best teacher is who, he never fail to learn." I am a qualified and experienced teacher in Mathematics,Science...

1.What are the main important part of human nervous system. Ans:The main parts of nervous system are Central Nervous System (CNS),Peripheral Nervous System (PNS) and Autonomic Nervous System (ANS). 2.CNS consist of which part of human body? Ans:CNS consist of human brain and spinal cord. 3.PNS consist... read more

1.What are the main important part of human nervous system.

Ans:The main parts of nervous system are Central Nervous System (CNS),Peripheral Nervous System (PNS) and Autonomic Nervous System (ANS).

2.CNS consist of which part of human body?

Ans:CNS consist of human brain and spinal cord.

3.PNS consist of which part of human body?

Ans:PNS consist of cranial nerves(12pairs) and spinal nerves (13 pairs).

4.What is ANS?

Ans:Two sets of nerves (parasympathetic and sympathetic) supplying visceral organs which are antagonistic to eachother.

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Lesson Posted on 21 Jun CBSE/Class 11/Science/Biology

cell organelles function

Vivek Paryekar

I have a total of 5 years teaching experience; I was a teacher in an ICSE school teaching science, especially...

cell is the basic unit of life. now what do you mean by basic. here basic means the smallest unit Membranes & Cell Coverings plasma membrane function What are the main components of cell membranes? What does the composition of a membrane tell you in general about permeability into a cell? Animal... read more

cell is the basic unit of life.

now what do you mean by basic. here basic means the smallest unit

 Membranes & Cell Coverings

  • What is the purpose of the microvilli?
  • specialized cell junctions

-adhesive junctions (desmosomes)

-tight junctions

-gap junctions

  • Cell Coverings in Plants

-cell wall

-plasmodesmata
-middle lamella

2. Endoplasmic reticulum (ER)

        -rough (RER) 
        -smooth (SER)

  • Functions

3. Golgi Apparatus

4. Nuclear envelope

  • Two membrane surrounding chromosomes
  • Comes from ER
  • Contains "pores"
  • What sort of molecules move between nucleus and cytoplasm?

5. Cytoplasmic matrix

What is the matrix?

What does the matrix do?

The cytoplasmic matrix has both a viscous flow like a liquid and elastic deformation like a solid (matrix near plasma membrane is more solid and in the cell center more liquid). Why?

6. Cytoskeleton

What is the cytoskeleton made of?

What does it do?

Examples

Membrane Bound Organelles

7. Nucleus

  • site of storage & replication of most cells hereditary material
  • contains chromosomes
  • contains nucleoli  
  • the degree of DNA packaging in chromatin depends on the state of the cell
  • single large DNA molecule in each chromosome many times longer than the chromosome
  • How is this compaction accomplished?

8. Lysosomes

  • single membrane bound organelle containing digestive enzymes
  • produced from the Golgi Complex
  • Functions
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Lesson Posted on 13 Jun CBSE/Class 11/Science/Biology

Biology Chapter 1: The Cell

Gunjan Sadera

Biology is a subject which can turn boring if not studied in a proper manner. Hence it can made easier...

1. What is Cell Biology?Branch of biology that deals with various aspects of structure, chemistry, development, genetics and functioning of cells are called cell biology. 2. Basic unit :The cell is the basic unit of life as no organism can have life without being cellular because the cell is a unit of... read more

1. What is Cell Biology?
Branch of biology that deals with various aspects of structure, chemistry, development, genetics and functioning of cells are called cell biology.
 
2. Basic unit :
The cell is the basic unit of life as no organism can have life without being cellular because the cell is a unit of both structure and function.
 
Organisms types ( on the basis of cell types)

Unicellular or acellular (organisms made of a single cell)

Eg: chlamydomonas, acetabularia, bacteria,yeast,amoeba
   
Multicellular (organisms made of many cells)

E.G., newly born infant (2 x 1012 cells)

3. Discovery of the cell:
   
1: Zacharias Janssen (1590): built the first microscope

2: Galileo (1610): Modified Microscope

3: Robert Hooke (1635-1703): a developed new microscope with which he studied the internal structure of a number of plants. His work was famous for the study of cork cells.

Robert Hooke > took a piece of cork of Spanish oak > prepared thin slice by means of sharp pen knife > deep planoconcave lens used  for throwing light > latter observed > cork had honeycomb structure with number of box-like compartments, each having a pore and separated from others by diaphragms > named as cellular (now known as cells).

Hooke microscope and structure of cork cells

4: Leeuwenhoek (1673): first to describe and sketch a live cell. He observed protozoa, spermatozoa, red blood cells etc.

5: Malpighi (1675) & grew (1682): gave an account of the internal structure of plants.

6: Mirbel (1802): said "Plants are formed by membranous cellular tissue"

7: Dutrochet (1824): stated " all organic tissues are really globular cells of an extreme smallness which are united by cohesion"

8: Robert Brown (1831) discovered the presence of nucleus in the cells of the orchid root.

9: Dujardin (1835): living semifluid substance of cells > named sarcode

10: Schleiden (1838): found all plant cells to have a similar structure- cell wall, a clear jelly-like substance and a nucleus.

11: Schwann(1838): discovered that animal cells lacked the cell wall.

12: Purkinje and Mohl (1838): renamed sarcode or jelly-like the substance of the cells as protoplasm

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Lesson Posted on 07 May CBSE/Class 11/Science/Biology Tuition/BSc Tuition/BSc Zoology Exam Coaching/Medical Entrance Coaching +1 Tuition/Class IX-X Tuition less

What is Sickle-cell haemoglobin?

Durgapada Rana

I am an experienced, qualified teacher and tutor, having 10+ years of experience in teaching. More than...

HbS forms as a result of a single amino acid substitution in the β-chain of Hb. Replacement of the glutamate residue at position 6 in the β-chain by a valine residue is the only chemical difference between HbA and sickle-cell haemoglobin. The residue is present on the outer surface of the molecule.... read more

HbS forms as a result of a single amino acid substitution in the β-chain of Hb. Replacement of the glutamate residue at position 6 in the β-chain by a valine residue is the only chemical difference between HbA and sickle-cell haemoglobin. The residue is present on the outer surface of the molecule. The change produces a sticky hydrophobic spot on the surface that results in the abnormal quaternary association of haemoglobin. This makes the deoxyHbS less soluble than deoxyHbA. Insoluble deoxyHbS forms polymers that aggregate into tubular fibres. The formation of insoluble deoxyHbS fibres distorts the RBC into the elongated sickle-shaped structure which is characteristic of the disease, sickle-cell anaemia. Sickle-cell anaemia and sickle-cell trait are different. Sickle-cell describes a condition in which an individual has one abnormal allele of the β-globin gene(heterozygous). A person with sickle-cell anaemia has two copies of the abnormal β-globin gene(homozygous).

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Answered on 09 Feb CBSE/Class 11/Science/Biology

Sujoy D.

Tutor

Plasmolysis is the process of water leaving plant cells, allowing the cytoplasm and plasma membrane to shrink away from the cell wall. This causes plants to wilt. Indeplasmolysis, water from the outside environment rushes into the cell through a process called osmosis, which creates turgor pressure. read more

Plasmolysis is the process of water leaving plant cells, allowing the cytoplasm and plasma membrane to shrink away from the cell wall. This causes plants to wilt. Indeplasmolysis, water from the outside environment rushes into the cell through a process called osmosis, which creates turgor pressure.

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Answered on 27 Jun CBSE/Class 11/Science/Biology

This is the second time I appeared for NEET and not sure, if I can clear it this time. With time I'm... read more
This is the second time I appeared for NEET and not sure, if I can clear it this time. With time I'm losing my interest and concentration as well. I know most of the concepts and don't wanna go all over them again. I want to join college. What other options do I have. read less

NIO Schools

Tutor

If you are worried about losing a year, It would be better for you to take admission in an undergraduate course of your choice. You can concurrently prepare for NEET, without the regret and burden of wasting another year. There are plenty of options to choose from, for undergraduate courses such as,... read more

If you are worried about losing a year, It would be better for you to take admission in an undergraduate course of your choice. You can concurrently prepare for NEET, without the regret and burden of wasting another year.

There are plenty of options to choose from, for undergraduate courses such as,  Agriculture, Medical Biotechnology, Biochemistry, Microbiology, Bioinformatics etc..

Some of these courses are also taught in govt. medical colleges such as AIIMS.

Plan well and achieve your goal. best of luck

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Answered on 01/03/2017 CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Prashanth K

Technical Trainer

Rs. 30,000/-
Answers 144 Comments 1
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