Notes And Study Material for Exam Papers

Meiosis or reduction division is complicated type of cell division occurring in the reproduction of germ cells at the time of gametic formation. In animals it occurs during gametes formation. Every species has definite number of chromosomes and that this number remains constant in its somatic cells, generation after generation. To keep the number constant the chromosome number in gametes is reduced to half. When male and female gametes and their nuclei fuse, normal number of chromosomes characteristic of each species is restored. The somatic or vegetative cells having the complete number of chromosomes are called diploid (2n). While gametes containing half of the original number of chromosomes are called haploid (n) or monoploid. The events of Meiosis: Meiosis consists of two successive divisions of mother cells. First division is reduction division, during which the chromosome number (2n) in both daughter cells is reduced to half (n), the second division is simple mitotic div...

During life cycle of most animals some diploid cells undergo meiosis and haploid gametes form in a process called gametogenesis. The testes of the male, produces sperms and is called spermatogenesis, in the ovaries of female, the production of oval (eggs) is called oogenesis. Spermatogenesis: Spermatogenesis produces mature sperm as follows: (1)        Spermatogenesis begins in unspecialized germ cells called spermatogomia (singular spermatogonium). The spermatogonium enlarges and becomes primary spermatocyte. (2)        A primary spermatocyte undergoes meiosis (meiotic division I) and produces two smaller secondary spermatocytes). (3)        Both secondary spermatocytes undergo second meiotic division (meiotic division II) to form spermatids each primary spermatocyte gives rise to four spermatids, each with the haploid number of chromosomes. (4)  ...

Animal Systematics: The goal of animal systematics is to arrange animals into group, that reflect evolutionary relationship. Monophyletic group: When groups include single ancestral species and all of its descendents such a group is called monophyletic group, in searching out monophyletic groups, taxonomists look for animal attributes called characters that indicate relatedness. Character: A character is virtually anything that has a genetic basis and can be measured from an anatomical feature to a sequence of nitrogenous bases in DNA or RNA. Polyphyletic groups: They have members that can be traced to separate ancestors. Since each group should have single ancestor, a polyphyletic group reflects insufficient knowledge of the group. Paraphyletic group: It includes some, but not all, members of a lineage. Paraphyletic groups result when knowledge of the group is insufficient. Evolutionary Systematics: It is the oldest of three approaches. It is also called tra...

In 1969, Whittaker described a system of classification that distinguished between kingdom according to cellular organization and mode of nutrition. According to this system members of kingdom monera are bacteria and cyanobacteria. They are prokaryotes members of kingdom protista are eukaryotic and consist of single cells or colonies of cells. Members of kingdom plantae are eukaryotic, multi-cellular and photosynthetic. Plants have walled cells and are usually non motile. Members of kingdom fungi are also eukaryotic and multi-cellular. They also have walled cells and are usually non motile. Fungi are decomposers. Members of kingdom animalia are eukaryotic and multi-cellular and they usually feed by ingesting other organisms or parts of other organisms. Their cells lack walls and they are usually motile. For the first two billion years of life on the earth, living forms were prokaryotic microbes. Molecular studies of variations in base sequences of ribosomal RNA from more than ...

Fiscal policy is the deliberate change in government spending and taxes to stimulate or slow down the economy. In the words of F. R. Glahe “By fiscal policy is meant the regulation of the level of government expenditure and taxation to achieve full employment without inflation in the economy.” J. M. Keynes describes fiscal policy as the steering wheel for the aggregate economy. Main objectives of Fiscal Policy: The objectives of fiscal policy differ with the state of development in the country. In advanced countries of the world, the goal of fiscal policy may be the maintenance of full employment without inflation. In developing countries, the objectives of fiscal policy may be to achieve maximum level of employment and reduction economic inequalities. However, the main objectives of fiscal policy are in brief as under. Removing deflationary gap: J. M. Keynes is of the view that fiscal policy can play a major role in lifting the economy out of depression and closing the ...

The budget of a government is a statement of its finances for a particular year. It indicates how the government or a public body concerned proposes to raise its revenue and incur its expenditure. If the expenditure happens to be in excess of revenue, the government state how the gap is to be met through raising various types of taxes or loans. A government in Pakistan whether federal or provincial has two sections of the budget  (1) Revenue budget (2) Capital budget. The revenue budget is concerned with the current needs and functions of government like defence, civil administration, judicial services, police and beneficent activities in the field of education, health, agriculture etc. The capital budget of the government is concerned with the building of lasting works of a capital nature, like irrigation, canals, dams, roads and other constructions. Major Expenditure Heads of the Federal Budget: As we know Public Expenditure may be (i) Development Expenditure whi...

Direct Tax: A tax is said to be direct when impact and incidence of a tax are on one and same person i.e. when a person on who tax is levied is the same who finally bears the burden of tax. For instance income tax is a direct tax because impact and incidence falls on the same person. Advantages of Direct Tax: Following are advantages of direct tax. 1. Direct taxes afford a greater degree of progression. They are therefore more equitable. 2. They entail less expense on collection and as such are economical. 3. They satisfy canons of certainty, elasticity productivity and simplicity. 4. They create civic consciousness in people. When a person has to bear burden of tax, he takes active interest in affairs of state. Disadvantages of Direct Tax: Disadvantages of direct tax are as follows: 1. It is easy to evade a direct tax than an indirect tax. Tax payer is seldom happy when he pays tax. It pinches him that his hard earned money is being taken by government. So h...