Skip to main content

Posts

Showing posts from August, 2019

Eyes: How They Work, Anatomy and Common Condition

 The eye is a complex sensory organ that allows us to see the world around us. The eye works by gathering light from the environment and converting it into electrical signals that can be interpreted by the brain. The basic structure of the eye includes the cornea, iris, pupil, lens, retina, and optic nerve. The cornea is the transparent outer layer of the eye that helps to focus incoming light. The iris is the colored part of the eye that regulates the amount of light that enters the eye through the pupil, which is the black circular opening in the center of the iris. The lens is a clear, flexible structure located behind the iris that helps to focus light onto the retina. The retina is a thin layer of tissue that lines the back of the eye and contains photoreceptor cells called rods and cones. These cells convert light into electrical signals that are sent to the brain via the optic nerve. The rods are responsible for the low light vision and detecting motion, while the cones are resp
Post a Comment
Read more

HUMAN EVOLUTION

When we start to talk about the human evolution, the first line which appear in our mind is hat the human is evolve from monkey or monkey is our ancestor, you also hear about this from most of the people that monkey is our ancestor but this is not true. Monkey and human was originated from common ancestors, so monkey are similar to human but when we talk about similarities the apes were more closer to human than monkey because apes and humans share there ancestors for very recent times. Some evidences for common origin of human and apes : Banding pattern of chromosome no. 3 and 6 of human and chimpanzee is 100% similar. Number of chromosomes are approx same in human (46) and apes (48). DNA content and DNA matching is same in both. This similarity is more than 99% with chimpanzee, 94% with Gibbon, 88% with Rhesus monkey. The skull of baby chimpanzee is more like adult human skull than adult chimpanzee skull. Composition of Hb is same in both. Only one amino acid is differen
Post a Comment
Read more

NEODARWINISM / Modern synthetic theory of organic evolution

Neo-Darwinism is a modified form of Darwinism along with recent researches of Weismann, De Vries, Stebbins, Dobzhansky, Sewall Wright, Mayr etc . According to this theory following factors are responsible for formation of new species : Rapid multiplication Limited food and space Struggle for existence Genetic variations Natural Selection Isolation : Isolation is a segregation of populations by some barriers which prevent interbreeding. The reproductive isolation between the populations due to certain barriers leads to the formation of new species. NATURAL SELECTION Natural selection is a process in which heritable variations enabling better survival are enabled to reproduce and leave greater number of progeny. A critical analysis makes us believe that variation results in changed frequency of genes and alleles in future generation. Coupled to enhance reproductive success, natural selection makes it look like different population and lead to new species formation.
Post a Comment
Read more

DARWINISM (Theory of Natural Selection)

Charles Robert Darwin was born on 12th Feb. 1809 in England. He was an English naturalist, geologist and biologist . Darwin travelled by H.M.S. Beagle ship, from 27 Dec. 1831 to 02 Oct. 1836 through South America, South Africa, Australia and Galapagos Islands. Later on he wrote a book "On the origin of species by means of Natural Selection" (1859) . In this book he gave his theory of Natural selection. Basic concepts of Darwinism : Branching Descent and Natural selection are the two key concepts of Darwinian Theory of evolution and his theory is based on certain observations which are factual. (1) Over production : All organisms have the capability to produce enormous number of offspring or organisms (multiply in geometric ratio). Hence, theoretically population size will grow exponentially if everybody reproduced maximally but the fact is that population sizes in reality are limited. (2) Struggle for existence : Natural resources are limited and
Post a Comment
Read more

LAMARCKISM (Theory of organic evolution)

Organic evolution is the changes in flora and fauna during the course of time. But when we see in our surrounding we didn't observe any changes because these changes are very small so we can't determine it but changes is taking pace in every moment of time and in previous post we see the evidences in favour of organic evolution and today we going to discuss about the theories of organic evolution. There were many theories given by various scientists for organic evolution, some of them we discuss here today.   LAMARKISM / Theories of inheritance of acquired  characters:- Jean Basptiste de Lamarck (1744 - 1829) was a French naturalist who proposed the first logical theory of evolution in his book Philosophie Zoologique (1809) Basic concepts of Lamarckism:- Internal vital forces : Due to the presence of some internal vital forces all organisms have the tendency to increase in size of their organs or entire body Effect of environment and new needs :  Environ
Post a Comment
Read more