• G1 phase (Gap 1) – G1 phase is the phase of the cell between mitosis and initiation of replication of the genetic material of the cell. During this phase, the cell is metabolically active and continues to grow without replicating its DNA.

• S phase (Synthesis) – DNA replication takes place during this phase. If the initial quantity of DNA in the cell is denoted as <i>2N</i>, then after replication it becomes <i>4N</i>. However the number of chromosomes does not vary, viz., if the number of chromosomes during G1 phase was <i>2n</i>, it will remain <i>2n</i> at the end of S phase. The centriole also divides into two centriole pairs in the cells which contain centriole.

• G2­ phase (Gap 2) –During this phase, the RNA, proteins, other macromolecules required for multiplication of cell organelles, spindle formation, and cell growth are produced as the cell prepares to go into the mitotic phase.

• M phase

  This is the mitotic phase or the phase of the equational division as the cell undergoes a complete reorganization to give birth to a progeny that has the same number of chromosomes as the parent cell. The other organelles are also divided equally by the process of cytokinesis which is preceded by mitotic nuclear division. The mitotic phase is divided into four overlapping stages:-

• Prophase,
• Metaphase,
• Anaphase, and
• Telophase

 Active transport is the movement of molecules across a membrane from a region of lower concentration to a region of higher concentration against the concentration gradient, often assisted by enzymes and requires energy 

 Passive transport is the movement of ions and molecules across the cell membrane without requiring energy. 

The fluid mosaic model was proposed by S.J. Singer and Garth L. Nicolson. This model explains the structure of the plasma membrane of animal cells as a mosaic of components such as phospholipids, proteins, cholesterol, and carbohydrates. These components give a fluid character to the membranes.

Each phospholipid has a hydrophilic head pointing outside and a hydrophobic tail forming the inside of the bilayer.

Cholesterol and proteins are embedded in the bilayer that gives the membrane a mosaic look. Each component has a specific function to perform.

Inclusion bodies are the non-living structures present in cytoplasm not bounded by, the membrane system. They may either lie free in cytoplasm or may be covered by 2-4 nm-thick, non-protein membrane, e.g., Vacuoles, sulphur granules, etc.

The marine animals termed echinoderms belonging to Phylum Echinodermata of Kingdom Animalia have spiny bodies. 

Characteristics of Echinodermata:

(i) Simple animals may be a star like, spherical or elongate.

(ii) Body triploblastic, coelomate, unsegmented and radially symmetrical.

(iii) Body lacks head but has oral and aboral surfaces. Oral surface of the body has five radial areas called ambulacra.

(iv) Body wall is covered with spiny hard calcareous (calcium carbonate) plates (ossicles) that forms a rigid or flexible endoskeleton.

Example: Echinus (sea urchin) and Asterias (star fish).

An absorption spectrum is constituted by the frequencies of light transmitted with dark bands when energy is absorbed by the electrons in the ground state to reach higher energy states.

Individual Series ;-
When the raw data is presented individually in the form of a series, it is called an individual series. In simple words, individual series is the arrangement of raw data individually. It gives numeric values for a specific situation. In an individual series items are shown singly.
For example, following are the marks of secured by the students in a class out of 100.
56, 77, 88, 49, 60, 92, 70, 81, 69, 51,
As we can see, in the above data, it is not clear that how many students got 56 marks or how many got 77 and so on.
Discrete Series :-
On the other hand, discrete gives data for each specific value of variable. The important thing in the discrete series is that, the variable involved in the series has integer values. Data are presented in a manner that exact measurement of items are clearly shown. 
For example, Given below is a table that shows the wages earned by 30 workers. 
Wages                  No. of Workers (Frequency)
 2500                                 7  
 3000                                 9
 4000                                 5
 4500                                 6    
 5000                                 3
From the above table, it is very clear that 7 workers are getting wages Rs. 2500, 9 workers are getting Rs. 3000 and so on.

In Indirect Oral Investigation, data is collected through indirect sources. Persons who are likely to have information about the problems, are interrogated and on the basis of their answers, factual data have to be compiled. Most of the commissions of enquiry appointed by government collect primary data by this method. The accuracy of the method depends largely upon the type of persons interviewed and hence these persons have to be selected very carefully.
Merits of Indirect Oral Investigation:
(i) It is economical in terms of time, cost and manpower.
(ii) Confidential information can be collected.
(iii) Information is likely to be unbiased and reliable.
(iv) This method is relatively simple to under-stand.
Demerits of Indirect Oral Investigation.
(i) The degree of accuracy of information is less.
(ii) This method leads to doubtful, conclusion due to ignorance and carelessness of the witness.

In Rome the society was highly class conscious and hierarchical. There were multiple social hierarchies present and mobility was also possible between the classes. The whole society of rome was divided into classes known as patrician, senators, equestrians, commons, freedpeople and slaves. Ancient Rome was made up of a structure called a social hierarchy, or division of people into differently-ranked groups depending on their jobs and family. The emperor was at the top of this structure, followed by the wealthy landowners, the common people, and the slaves (who were the lowest class).