A brief look at Annelids

Annelids are the organisms having bilateral symmetry. They are triploblastic with tube within the tube body plan. They are metamerically segmented with closed circulatory system.The excretory organ of annelids is Nephridium. Cuticle of annelids is non-chitinous and albuminoid. Annelids have Schizocoelic coelom.

Among annelids great power of regeneration is observed in Chaetopterus. A clam worm possesses 2 pairs of eye. Nereis is gregarious, nocturnal and carnivorous. Eunice is an example of Errantia.

Phylum annelida resembles Mollusca in embryonic features because both have identical conspicous segmentation in body muscles ans nervous system.

The phylum annelida is divided in to 4 classes:

A. Polychaeta

B. Oligochaeta

C. Hirudinea

D. Arachinnelida

Natural Selection

One of the basic mechanisms for evolutionary change is natural selection. Darwin’s grand idea of evolution is considered simple but it is often misunderstood. Natural selection determines the capacity of survival and reproduction of organism. Natural selection means the acquiring and inheritance of certain character that makes an organism to compete better in their wild condition . For example, imagine the population of beetles. Some are green and some are brown. Most of the green beetles are eaten by birds but not brown because of their color. Also, less number of brown offspring are eaten which allows brown beetles to have large number of offspring and lastly they become more common in population.
Industrial Melanin
It is a classic example of natural selection operating as a result of human activity. Industrial melanism is the phenomena by which various species of moths have undergone genetic modification. Body color was an action in response to the darkening of their natural habitat. It is due to the production of air pollutant such as soot, associated with the industrial revolution. This phenomena has been observed in more than 70 species of moths in England and over 100 species in U.S.

Evolution

Mysterious things are turned to obvious things efficiently using science. The study of evolution works to convert much that were mysterious in to things, every evolutionary biologist now finds it obvious. The collection of data, the composition of many possible interpretations and rejection of quite few of them and going through controversies. The theme of biological evolution is that all life on earth shares a common ancestor. Evolution simply means modification of descents. Evolution helps us to understand the history of life. The central idea is that all living things evolve from common ancestor. The person identified with the discovery of evolution is Charles Darwin. Particularly, evolutionary biology is based on and stimulated by the accurate observation of nature.
The change in genotype and phenotype of living things with respect to time helps an individual to be well suited to environment. With modification, the common ancestor gave rise to the fantastic diversity that we can get in the fossil records and around us today. Evolution says that all the living things in the earth are related to each other. For example, Human and trees, whales and birds must be related to each other. Reproduction falls under one of the unique character of living things. Replication of DNA is a very important factor in reproduction that can be passed on. This is very accurate process and sometimes rare mistakes occurs known as mutation. Mutation might not play any role in phenotype of organism but it may be viable in many cases. Very few cases are found to survive after mutational change. So, in extreme cases mutation can act as the decision maker for the life and death of an organism. Giraffe for instance have long necks but they might not have it before. At some point of time mutation could have caused the giraffe to have long neck and they survived but the giraffe with shorter neck died due to scarce of food in the ground level or grasses. Hence by this process giraffes with longer necks might have evolved.

Ribosomes-Facts

Ribosomes are also called Palade's granules or engine of the cell or protein factories. The ribosomes were discovered and named by Palade. Ribosomes are smallest and most abundant cytoplasmic organelle.Ribosomes are made up of protein and RNA in about equal amounts. Ribosomal RNA contribute about 80% of cell RNA. Ribosomes are attached to the RER through glycoproteins known as ribophorins. They are about 20nm in diameter. the mass of ribosomes is expressed in Svedberg units.

They are of two types:

1.Cytoplasmic ribosomes: It is 70s type in prokaryotic and 80s type in eukaryotic cell.

2.Organelle ribosomes: They are 70s, 55s, 73s, 67s, 60s types and found in organelle of eukaryotic cells like plastids, mitochondria and nucleus.

Charles Darwin

Charles Darwin (1809-1882) is “one of the most important people of nineteenth century”. It is difficult to characterize Darwin despite his acknowledged importance. He was as much a cultural product as a shape of culture. He was the man who conducted his own observations and experiments but collected data tirelessly from others. Born in Shrewsbury in 1809 as the fifth of six children born to Dr.Robert Darwin and his wife Susannah Wedgwood, Darwin entered Shrewsbury school for his education. At the age of 16 he was sent to Edinburgh University to study medicine. Darwin was not interested in medicine instead his interest lay elsewhere in gathering stones and insects. Recognizing that he has no interest in being a medical man, he was sent to Christ College, Cambridge University. Charles earned his bachelor’s degree in technology in 1831. He made friends like John Henslow who was both botanist and mineralogist during his tenure as student in Cambridge. It was Henslow who suggested Darwin to Captain Robert Fitz Roy of the HMS Beagle. HMS Beagle under the command of Captain Fitz Roy, sailed from Davenport which was twice been driven back by heavy southwestern gales. The expedition was originally planned to last for two years, but it almost lasted for almost five years. As the naturalist, the purpose of the voyage was to chart the coast of Patagonia and Tierra del Fuego and to carry the chain of chronometric readings round the world. He spent most of his time exploring on land.
During the Voyage of Beagle he pursued and published serious studies on such diverse topics as coral reefs, earthworm, barnacles, fertilization in plants and the descent of man. Much of his interest in variation was no doubt stimulated by observations during a four year cruise around the world visiting natural habitats with rich and diverse fauna.
Darwin did not become an evolutionist on the Voyage that turned him in to. In the HMS Beagle, Darwin not only shares his scientific observations but also the views of the people and societies. He visited, from the elegant signorians in the street of Buenos Aires to the pitiful Tekeenicas Indians who lived at sustenance level and worse in wilderness of Tierra del Fuego. During his observation he was not only surprised by the difference between species but also from their similarities. He wrote in his journal of the Galapagos Islands, “ …yet all shows the marked relationship with those of America though separated from that continent by an open space of ocean, between 500 and 600 miles in width”. From these findings he proposed ‘Theory of Evolution’ which says that all living things are related and descended from common ancestor. His general theory mainly states that the life developed from non-life and stresses a purely naturalistic “descent with modification”.

Mitochondria

Mitochondria are the membrane bound organelles. They are found in the eukaryotic cells. The size of mitochondria ranges from 1-10 micrometers. The outer surface of mitochondria is smooth but the inner surface has folds known as cristae. They increases the inner surface area. It is the cristae where the food combine with oxygen which results in the formation of ATP which is the chief source of energy in our body.That is why mitochondria are also called as the power house of cell.
Mitochondria are the unique organell in our body. They have their own genome. That is why the clones can not be totally similar to that of parent. The number of mitochondria varies from organism to the type of tissues.

Penicillins and Cephalosporins

Antibiotics are used to kill bacteria. Penicillin is the first antibiotic to cure bacterial infection in humans which is produced naturally by a fungus called Penicillium chrysogenum. Penicillin and the drug called Cephalosporin are produced by the fungi of same genus Cephalosporium. They are closely related in structure and function. They are effective due to their binding property to the enzyme that catalyze the formation of cross-links between individual strands within the peptidoglycan. If the cross-links are unavailable, the bacterial cell wall become weak resulting in the tearing out of cell wall which destroys the cell. Penicillin and Cephalosporin cause little side effect in human because of their specific binding property.Since, human cells lack the enzyme involve in cross-linking peptidoglycan, they are not affected by these antibiotics.
Due to the widespread use of these antibiotics, some bacterias have developed an enzyme that break these drugs making them ineffective. Hence researchers have developed molecules closely related to penicillin and Cephalosporin in structure and carry out the same function but not largely affected by these bacterias. They include methicillin, ampicillin, ceftriaxone, etc.

Quantum numbers

Quantum numbers are used to specify the position of an electron in the space. There are four quantum numbers:
a.Principal quantum number(n): It was proposed by Bohr. Its value ranges from one to infinity. It can never be zero negative or fractional. It determines main energy levels,average distance of nucleusand energy of electron.
b.Azimuthal quantum number(l): It was given by Sommerfield.It represents subshell. It determines orbital angular momentum of electrons,shape of subshell and energy associated with orbital angular momentum of electron. Its value ranges from 0 to (n-1).
c.Magnetic quantum number(m): It was given by Lande. It explains the orientation of orbitals in space. It explains Starks and Zeeman effect.For a given value of l there are (2l+1) values of m ranging from -l to +l.
d.Spin quantum numbers(s): It was given by Goudsmit and Uhlenbeck. It is used to describe spin orientation of electron. Its value is either +1/2 or - 1/2.

Is evolution completely scientific?

We can find puzzling questions in the evolutions which are under intense research and scientists are still to conform. Assumed evolutionary sequence states that fish gave rise to amphibian. This change would require millions of years and have involved many transitional forms. But no such series of fossils have been found till date.
There are puzzles in the phylogeny of animals. The first puzzle is that 60-80 different structural types of animals in the early Cambrian suddenly appeared. The second puzzle is that why no major new types originated in the 500 millions years since the Cambrian.
The principle source of new genetic variation is mutation. Most errors are due to errors in the replication process during meiosis that is not corrected by any mechanism. There is no mutation pressure. Most of the variation of genotypes available for selection in a population is the result of recombination, not of new mutation.
Is the evolution slow continuous change in gene of the organism? But we do have certain genetic fact that takes us to dark. The example of pleiotropic gene is one of them. There are pleiotropic genes that control most of the genes. So, what happens if changes occur to that gene? Will a new organism evolves with a new genetic makeup? If yes, why these are not described by fossils.
Mammals and Dinosaurs are a classic example of independent replacement but the molecular evidence questions the whole record. The fossil record shows the rapid rise in the early tertiary, after the end cretaceous mass extinction. But according to molecular theory the mammal and dinosaurs co-existed for about 30 millions years of cretaceous. This does not prove that mammals competed with dinosaurs.
Antievolutionists claim that there are limit to the amount of change that can be made. There is creationist like Gish who claims that there are some limitations within “basic kinds”, without being able to express exactly that why changes are restricted within them. Others claim that the limit lies in the availability of genetic variety. When limit is reached it ceases variation, “might conceivably be renewed by mutation, but whether this happens is not known,” of course it is unknown.

Plant Growth

Growth is the outcome of cell division, cell enlargement and cell differentiation. Scientifically, growth is the increase in dry weight. Plant growth is measured by Auxanometer.
Plants grow faster than animals and some grows much taller than animals. Plant growth is completed in four phases:
A. Lag phase: It is the initiating phase.
B. Log/ Exponential phase: It is the phase in which maximum growth occurs.
C. Stationary phase: This is the phase in which growth remains constant.
D. Decelerating phase: In this phase the growth rate decreases.
The idea of existence of growth promoting substance in plant was given by Charles Darwin. The major plant hormones are auxin, gibberellin, cytokinin, ethylene and abscissic acid.