Environmental Issues, Class 12, Biology, CBSE 2 Environmental Issues Causes of air pollution The main causes of air pollution are as follows:(a) Exhaust from Automobiles: Most of the automobiles use fossil fuels. Burning of fossil fuel releases carbon dioxide and carbon monoxide. Carbon dioxide is a greenhouse gas. Carbon monoxide is a poisonous gas even …
1 Theories of Origin of Life and EvolutionTheories of Origin of Life(i) In previous days, people believed that the universe and life on it was an act and result of God’s creation.(ii) There was, however, no evidence to support these claims.(iii) The early scientists and Greeks believed that life on Earth never began on Earth …
– All formulas of the chapter at one glance. 1 Hardy-Weinberg Equilibrium Hardy-Weinberg principle states that the genetic constitution in a population remains constant if there is no external influence. This statement gives us a formula that is used to solve the numerical problems of this chapter. Check the formula and the example below. 2 Calculating …
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1. Comparative morphology and anatomy of individual organ and organ systems of diverse forms of organisms reveal their phylogenetic relationships and thus provides important evidences of evolution.2. Homology is a relationship defined between structures or DNA derived from a common ancestor and illustrates descent from a common ancestor.3. A common example of homologous structures in …
The following are the stages of human evolution: 1. Dryopithecusi) Ancestors of both man and apes. ii) Lived in China, Africa, Europe and India. iii) Predominantly herbivores2. Ramapithecusi) First remains were discovered from the Shivalik range in Punjab and later in Africa and Saudi Arabia. ii) Lived in open grasslands. iii) Thickened tooth enamel, robust jaws and shorter caninesiv) Usage of …
Founder effectIt is the effect on the resulting gene pool that occurs when a new isolated population is founded by a small number of individuals possessing limited genetic variation relative to the larger population from which they have migrated.Sewall wright effectThe sudden and random change in the allele frequency occurring in small or isolated populations by …
1. The Hardy-Weinberg principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.2. The Hardy-Weinberg equation is expressed as: p2 + 2pq + q2 = 1 where p is the frequency of the “A” allele and q is the frequency of the “a” allele …
The salient features of mutation theory are as follows:1. Mutations or discontinuous variations are the raw material of evolution.2. Mutations appear all of a sudden. They become operational immediately.3. Unlike Darwin’s continuous variations or fluctuations, mutations do not revolve around the mean or normal character of the species.4. The same type of mutations can appear …
Natural selection is of three types directional, stabilizing, and disruptive selection.1. Directional selection occurs when natural selection favors one extreme of continuous variation. Over time, the favored extreme will become more common and the other extreme will be less common or lost.3. Stabilizing selection occurs when natural selection favors the intermediate states of continuous variation. Over time, the intermediate …
