Saturday, April 27, 2019

Plant and Animal Tissues

Biology Notes on Plant and Animal Tissues

Plant and Animal Tissues biology notes for rrb ntpc, ssc and group d exam

Tissue is a group of structurally similar cells performing a specific blood, muscles, xylem, phloem, etc.
     Branch of Biology which deals with the study of tissues is known as Histology.

Monday, April 8, 2019

Cell Division Notes for RRB NTPC and SSC Exams

StudyOnline Present Study Notes on 'CELL DIVISION' for RRB NTPC, Group D and SSC Exams

Cell Division :- Cell Division is the process in which One mother cell divides into two or more daughter cells. it was first  proposed by a scientist Nageli and was observed by Flamming in 1882.

Cell Division usually occurs in the following three ways:-
  1. Amitosis,
  2. Mitosis,
  3. Meiosis
Amitosis:- It is also known as direct cell division. It occurs in some bacteria, yeast, Amoeba, etc. In this type of cell division mother cell divides in two daughter cell.

  • Division of cytoplasm is called Cytokinesis.
  • Division of Nucleus is called Karyokinesis.

Mitosis cell Division:- It usually takes place in somatic cell of animal. In this type of cell division mother cell divides in two daughter cell of same number of chromosomes. It occurs in various phases such as prophase, metaphase, anaphase and telophase.

Mitosis cell division notes for rrb ntpc and ssc exams
Mitosis cell division (image source:- wikipedia)

Prophase:- centrosomes that is consist of two centrioles start dividing. centrioles start moving apart and reach opposite poles.
Chromosomes are already duplicated as paired chromatids.
Sister chromatids attached to each other at a small region called centromere.
Spindle fibers appear between daughter centrioles forming the achromatic spindle.
Nuclear membrane and nucleolus disappear.

Metaphase:- Each chromosomes gets attached to spindle by its centromere.
Chromosomes line up one plane at equator.

Anaphase:- Centromere attaching the two chromatids divides or splits.
The two sister chromatids of each chromosomes separates and  are drawn apart towards opposite poles pulled by shortening of spindle fibres.
A furrow starts in the cell membrane at the middle in animal cell.

Telophase:- Two sets of daughter chromosomes reach opposite poles.
Spindle fibres disappears.
Chromatids thin out in the form of chromatin fibres.
Nuclear membrane is formed
The cleavage furrow starts deepening in the animal cell
Nucleoli appear
Two daughter cell formed from one mother cell with equal number of chromosomes.

Differences between mitosis in Animal and Plant cell

Animal CellPlant cell
1 Aster are formed Aster are not formed
2 Cytokinesis by furrowing of cytoplasm Cytokinesis by cell plate formation
3 Occurs in most tissues through the body Occurs mainly at the growing tips

Meiosis cell Division :-
It occurs in reproductive cells and is called reproduction division. In this type of cell division one mother cell divides in four daughter cells with half the chromosomes of the mother cells.
It consist of two stage of division that occur successively in an organism with one time chromosomes replication
First meiotic division (Meiosis 1)
Second Meiotic Division (Meiosis 2)

Meiosis cell division notes for governmenr exams
Meiosis cell division (image source :- wikipedia)

Meiosis 1 :- In this type of division, parental chromosomes replicate to produce identical sister chromatids and the number of chromosomes reduces from diploid(2n) to haploid(n).
Like mitosis, it also involves the four phases of division i.e Prophase 1, Metaphase 1, Anaphase 1, Telophase 1.

Meiosis 2 :- The mitotic division is exactly the same in overall process as mitotic division.There is no reduction in the number of chromosomes and the haploid nuclei diploid mitotically in order to produce four haploid daughter nuclei. The phase involves in meiosis ll are prophase 2, metaphase 2, Anaphase 2 and Telophase 2. After the meiosis ll four daughter cells are formed from the original single parent cell and each one is haploid (n) in nature.

Differences between Mitosis and Meiosis :-

1 It occurs in somatic (body) cell It occurs in reproductive cell
2 It provide for growth and replacement
through life
It provide for gamete formation
3 Mother cell to daughter cell (2n-2n)
Mother cell to Daughter (2n-n)
4 One mother cell to two daughter
cell formation
One mother cell to four daughter
cell fomrmation

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Tuesday, March 26, 2019

The Human Eyes and Its Major Defects

Study Notes On Human Eye for RRB NTPC, SSC and Other Exams

The human eyes and their defects for rrb ntpc, rrc group d and ssc exams

The Human Eyes

The Human Eyes situated in the sockets of the skull called orbits. The eye ball is mainly spherical in structure.

Cornea :-

It is the transparent spherical membrane covering in the front of the eyes. Light enters in the eyes through this membrane. Most of the refraction of light rays entering the eye occurs at the outer surface of the cornea.

Tuesday, March 12, 2019

Different Branches of Science for Railway Exams

Branches of science

The different branches of science, notes for Railway exams

In the past examination conducted by RRB Bord you noticed that how the science is an important subject. For the upcoming Railway exams 'StudyOnline' brings regular post for crack the upcoming exams. Today we will learnt about the Different Branches of Science so let's start

Wednesday, March 6, 2019

DNA, RNA and Chromosomes, Notes for RRB NTPC, RRC and SSC exams

DNA, RNA and Chromosomes, Notes for RRB NTPC, RRC and SSC exams

DNA, RNA and Chromosomes, Notes for RRB NTPC, RRC and SSC exams

Biology is the the most important subject in the recent RRB, SSC or any other exams. The trand of question from science continuesly rising.To avail the opertunity we provide this article on DNA, RNA and Chromosomes that will surly help you in the exam.
To better understand this article you should read my article on Cell : The Unit of Life

Thursday, February 28, 2019

Vitamins, Must questions asked in RRB Exams

Vitamins, Must questions asked in RRB Exams

Vitamins and their Sources

vitamins and their chemical names for rrb ntpc, rrc group d, ssc exams
The chapter VITAMINS is most import for RRB Exams. You know that RRB recently published huge vacancy around 130000 post for this year. To achieve your target and get selected in this post you have to do hard work according to syllabus. We are going to publish some most important topics that help you in this exam.