Wednesday, November 27, 2013

The American Heart Association's Nutrition Committee strongly advises the fat guidelines for healthy Americans over age two.

  1. Limit total fat intake to less than 25–35% of your total calories each day;
  2. Limit saturated fat intake to less than 7% of total daily calories;
  3. Limit trans fat intake to less than 1% of total daily calories;
  4. The remaining fat should come from sources of monounsaturated and polyunsaturated fats such as nuts, seeds, fish and vegetable oils; and
  5. Limit cholesterol intake to less than 300 mg per day, for most people.
  6. For example, a sedentary female who is 31–50 years old needs about 2,000 calories each day. Therefore, she should consume less than 16 g saturated fat, less than 2 g trans fat and between 50 and 70 grams of total fat each day (with most fats coming from sources of polyunsaturated and monounsaturated fats, such as fish, nuts, seeds and vegetable oils).

Nucleic acids and classification

Nucleic acids are complex organic polymers that store and transfer genetic information within a cell. Inside a cell, they are the source of genetic information stored as chromosomes. Nucleic acids are composed of long chains of nucleotides linked by dehydration synthesis.

Two types:
a. Deoxyribonucleic acid (DNA-double helix)
b. Ribonucleic acid (RNA-single strand)
DNA serves as genetic material, whereas RNA plays a vital role in using genetic information to dictate the amino acid sequence to manufacture proteins.

Each Nucleotides are composed of 3 parts:
1- phosphate group (P)
2- pentose sugar (5-carbon)
3- nitrogenous bases: These can be any one of five types given below-
• adenine (A)
• thymine (T) (DNA only)
• uracil (U) (RNA only)
• cytosine (C)
• guanine (G)

DNA, Gene and Genome

DNA: Deoxyribonucleic acid, one of the two forms of nucleic acid in living cells. Polymers of nucleic acids. The genetic material of life. Each strand of DNA consists of a chain of four kinds of nucleotides (because of four different Nitrogenous bases). The order of nucleotide bases in a strand of DNA—the DNA sequence—is genetic information.

Gene: A DNA segment containing biological information which encode for an RNA and/or polypeptide molecule.

Genome: A genome is the full set of genes in each cell of an organism.

The hereditary nature of every living organism is defined by its genome, which consists of a long sequence of nucleic acid that provides the information needed to construct the organism. Genes are the basic unit of genetic information. They determine the nature and the function of the cell. The human genes (about ~ 30- 40,000) are referred to as the human genome. A genome is the full set of genes in each cell of an organism. It is the sequence of the individual subunits (bases) of the nucleic acid that determines hereditary features. By a complex series of interactions, this nucleotide sequence is used to produce all the proteins of the organism in the appropriate time and place. The proteins either form part of the structure of the organism, or have the capacity to build the structures or to perform the metabolic reactions necessary for life.

The human genome consists of two distinct parts:
1. Nuclear genome:
3.2 X 109 bp of DNA
30,000 – 40,000 genes
2. Mitochondrial genome:
circular DNA molecule of 16,569 nucleotides & consisting of 37 genes
Adult human body contains approximately 1013 cells.
Each cell has its own copy or copies of the genome.

Human chromosomes

Chromosome: Discrete unit of genome carrying many genes. Each chromosome consists of very long molecule of duplex DNA and approximately equal mass of proteins.
Each species have their unique number of chromosomes. All Human cells contain 23 pairs of chromosome, which is a total of 46 chromosomes in each cell. Human body cells have two of each type of chromosome, which means that their chromosome number is diploid (2n). 22 of the pairs are called autosomes and are numbered from largest to smallest. The autosomes are not involved in determining sex. The two members of each pair have the same length and shape, and they hold information about the same traits, Except for a pairing of sex chromosomes (XY) in males,
The 23rd pair are the sex chromosomes:
  •  XX in females
  •  XY in males

The Central Dogma of Molecular Biology

The idea that genetic information is stored as DNA, copied into RNA, and then used to build proteins is considered the central dogma of molecular biology.

The instructions in DNA determine the structure and function of all living
things. Every time a cell reproduces, it must make a copy of these instructions for the new cell. When cells need to build a functional molecule (usually a protein), they copy the information in the genes into an RNA molecule instead of using the DNA blueprint directly.

Here’s an outline of the process:
  1. Cells use transcription to copy the information in DNA into newly synthesized RNA molecules.
  2. The information to build proteins is copied into a special type of RNA called messenger RNA (mRNA), which carries the blueprint for the protein from the nucleus to the cytoplasm where it can be used to build the protein.
  3.  In a process called translation, proteins are build from the information carried in mRNA molecules.
Transcription is the process by which the information contained in a section of DNA is transferred to a newly assembled piece of messenger RNA (mRNA). An essential enzyme called RNA polymerase finds the genes within the DNA it needs to copy with the help of proteins called transcription factors. Transcription occurs in the nucleus.

Messenger RNA is the only kind of RNA that carries a protein-building message. By the process of translation, the protein-building information in an mRNA is decoded (translated) into a sequence of amino acids. The result is a polypeptide chain that twists and folds into a protein. Simply, Translation is the process where ribosomes (a type of cellular machinery needed for holding the mRNA when translating) synthesize proteins using the mature mRNA transcript produced during transcription. Translation occurs in the cytoplasm.

Needs of living things

What do you need to live comfortably? The list probably includes food, a home, clothes, and water. But, the basic necessities of every living thing includes:

Light and Carbon Dioxide:

All life forms need energy to survive. Living things use energy to grow, to defend themselves, and to move around – this energy is provided by the Sun – the primary source of energy. Plants use sunlight and carbon dioxide from the air to create their own food by photosynthesis. Many animals then eat the plants, taking this energy into their own bodies. Other animals then eat these plant eaters, passing the Sun's energy from one organism to another. The food organisms take in provides them with energy, and also provides them with the resources, and raw materials they need to build up their bodies, grow, and repair damage.


Living things need water to survive. But why is water so important? All life forms on Earth are comprised almost entirely of water. Your own body is about 60-80% water.Water in your blood helps transport food, and chemicals to your cells. It helps remove waste products from your body. Water is used to cool you down, to warm you up, and to carry out the chemical reactions that allow you to move and grow. Another important use of water, is to keep your body clean. Plants use water to grow, to transport food, and to carry out chemical reactions. In addition, plants use water as part of photosynthesis, to create their own food.


Without food, your body would die in a matter of weeks. Without water, you would day in days. How long do you think you would live without oxygen? Most life forms use oxygen as the main ingredient in many of the chemical reactions needed for life. Organisms get oxygen from their environment in a variety of ways. Many land animals breath oxygen directly from the air, while ocean bearing animals often use the oxygen dissolved in the water to survive.


The Earth’s soil contains minerals, which are essential for health and growth. Plants take in minerals through their roots. Animals get minerals by eating plants and/or other animals.


If it gets too hot or cold, the chemical changes which are necessary for life will stop. In many parts of the Earth, temperatures lie between 25 deg Celsius and 30 deg Celsius. Most living things are adapted to live at these temperatures.

The biosphere:

Biosphere is all those parts of the earth’s surface where living things are found. All of the needs we have mentioned so far, energy, food, water, and oxygen are obtained by organisms in their environment, or the space around them.
Living things are found almost everywhere, from about 9000 meters up mountains to at least 5000 meters under the sea.

Classification of living things

Biologists believe that there may be over two million (2,000,000) different kinds of organisms. Already over 1.5 million (1,500,000) different kinds have been identified and new ones are still being discovered. One biologist estimates that for each kind of organism now alive, another 400 kinds once lived but have since become extinct. Therefore, as many as one billion (1,000,000,000) different kinds of living things may have existed on the earth at one time or another.

How can we keep track of such a bewildering number of organisms? How can we even name the organisms now alive when no known language has two million words in it? Biologists have answers to these questions.

What is classification?

Whenever we work with a large number and variety of things, we usually sort them into groups. Each group contains those things that are similar to one another. We may then separate each of those groups into smaller groups that are even more alike.
The grouping of similar things for a specific purpose is called classification. Although it may be instinctive for human to classify things, there are also practical reasons for doing this. For example, a supermarket manager classifies the foods in his/her store by storing all the cereals together, all the meats together, all the cookies together, and so on. Stamp collectors classify their stamps. They place all the Canadian stamps in one page and all the American stamps in another. The words in a dictionary are classified by alphabetical listings. Clearly, we classify things to make it easier to keep track of what we have, and to find particular items.

Early Biological Classification

Biologists have long recognized the need to classify living things. In fact, humans have been classifying living things for thousands of years. The earliest humans probably classified organisms as plants and animals. They may have further classified plants as edible or poisonous, and the animals as harmful or harmless. However, it was 300 BC before the first serious attempt was made to classify all the organisms known. This attempt was made by the Greek philosopher and scientist, Aristotle and his students.

Aristotle’s Classification System

Since only about 1000 kinds of organisms were known at that time, a very simple classification scheme could be used. Aristotle and his students first classified the organisms as plant or animal. They then classified the animals according to where they lived. This resulted in three groupings: air animals, water animals, and land animals. They classified the plants according to the structure of stems. Those with soft stems were called herbs; those with a single woody stem were called trees; and those with many small woody stems were called shrubs.

Aristotle’s classification system survived for almost two thousand years. However, by the beginning of the 18th century, over 10,000 kinds of organisms were known and Aristotle’s system was unable to classify them all. Many of newly discovered organisms would not fit into any category of Aristotle’s simple system. A new system was obviously needed.

Modern Biological Classification


Taxonomy is the science that deals with the classification of organisms.

The Contribution of Carolus Linnaeus

Carolus Linnaeus, a Swedish botanist, developed a simple classification system that forms the basis of our modern method of classification. At the start of the 18th century about 10,000 kinds of organisms were known. By the end of that century over 70,000 kinds were known. Linnaeus tried to develop a classification system for this large number of organisms. By 1753 his system was well developed and modern taxonomy began.

The Basis for Linnaeus Classification 

Biologists use the word diversity to mean differences, or the number of kinds of living things.
There seem to be so many kinds of living things and they seem to be so different from one another. Yet, if we study them closely, we can see many likenesses. For example, at first glance lions, horses, humans, and mice seem to have little in common. A closer look however, shows that all have hair, a distinct head, four limbs, two ears, and warm blood. That is, they have similar structural features.
Linnaeus decided to use structural features as the basis for his classification system. Therefore, he grouped organisms according to their structural similarities. These organisms with very similar structural features were considered to be the same species. Thus all modern-day humans belong to one species, all house cats belong to one species, and all sugar maple trees belong to one species.

Modern Basis for Classification

Homologous Structure

Carolus Linnaeus used structural features as the basis for his classification system. He grouped organisms according to their structural similarities. Today, taxonomists still use structural similarities as a basis for classification. They look for homologous structures just as Linneaus did.
Homologous structures are structures that show the same basic pattern, the same general relationship to other parts, and the same pattern of development.
However, they need not have the same function. For example, the human arm, the whale flipper, and the bat’s wing, all these appendages are homologous structures that show the same basic pattern. Also, all three appendages are found in the same part of the body. Finally, the bones in all three appendages develop in similar ways. Although their functions are different, they are homologous structures.

Similar Biochemistry

Biochemistry is the study of the chemical compounds formed by living things. Many biologists believe that closely related organisms form similar chemical compounds in their body. They use this belief to help classify organisms. For example, the horseshoe crab was, at one time, classified as a close relative of the true crab. However, chemical analysis showed that its blood was more like spider’s blood than crab’s blood. Thus, the horseshoe crab is now classified as a close relative of spiders.

Genetic Similarity

Most biologists agree that genetic similarity is the best evidence that organisms are closely related. Every organism makes a special compound called DNA that bears hereditary characters. Thus it seems reasonable to assume that the greater the similarity of DNA among organisms, the more closely they may be related.

Selecting a Classification System

Some biologists feel that two kingdom, Plantae and Animalia, are enough to classify all living things. Others prefer three kingdoms; still others use four, and some use five kingdoms.

The Main Classification Groups (Taxa)

There are seven main taxa or classification groups. This system of classification can be compared to a tree. Many leaves (species) are on a tiny twig (genus). Several tiny twigis (genera) are on a larger twig (family). Several larger twigs (families) are on a little branch (order). Some little branches (orders) are on a larger branch (class). Some larger branches (classes) are on a main limb of the tree (phylum). The few main limbs (phyla) make up the whole tree (kingdom).

1. Species: Species (plural also species) is a group of individuals that are alike in many ways and interbreed under natural conditions to produce fertile offspring (children).

2. Genus: Genus (plural genera) is a group of species that are closely similar in structure and evolutionary origin.

3. Family: Family is a group of similar kinds of genera. That is, similar genera are grouped to form a taxon called Family.

4. Order: Similar families are grouped to form a taxon called order.

5. Class: Similar orders are grouped to form a taxon called class.

6. Phylum or Division: Similar classes are grouped to form a taxon called phylum or division. Zoologists favor phylum and botanists favor division.

7. Kingdom: All the phyla or divisions that contain animals are grouped in the kingdom Animalia,
and all the phyla or divisions that contain plants are grouped in the kingdom Plantae.

Tuesday, November 26, 2013

Phylogenetic System of Classification

Carl R Woese introduced a completely new approach in classification of organisms in 1977 that is based on evolutionary (phylogenetic) relationship among organisms. He meticulously analysed ribosomal ribonucleic acid (rRNA), genetic molecules that coordinate part of protein production. Because rRNA shows only slight variation from one generation to the next, it is an excellent tool for revealing the evolutionary, or family, relationships among organisms. Woese spent nearly a decade analysing the rRNA of various types of bacteria and arranging them into a microbial evolutionary tree. Use this concept all organisms are now classified into three kingdoms.
 They are
(1) Archaea,
(2) Bacteria, and
(3) Eukarya.

Binomial Nomenclature

Once Linnaeus had decided on a basis for classifying organisms, he then developed a system for naming them. His system is quite simple. He gave each species a name that consists of two words. This system is called binomial nomenclature. He used Latin words for these names because all scientists wrote in Latin in time of Linnaeus. Thus, the human is Homo sapiens, and the domestic (house) cat is Felis domesticus. The first word of each name is called the genus and the second word is called the species. The genus begins with a capital letter and the species does not. The genus and species are either printed in italics or underlined.

The Genus Concept
A genus (plural genera) groups species that are similar. For example, maple trees belong to the genus Acer. Thus sugar maple (Acer saccharum), silver maple (Acer saccharinum), and red maple (Acer rubrum) belong to the same genus Acer. Their leaves are similar and other features are similar but not identical. Every genus has characteristics that make it stand out clearly from other living things.

The Species Concept
Linnaeus grouped as a species those organisms that he felt were very similar in structural features. In simple terms, a single species is a distinct kind of organism, with a characteristic shape, size, behaviour, and habitat that remains constant from year to year.
A species (plural also species) is defined as a group of individuals that are alike in many ways and interbreed under natural conditions to produce fertile offspring (children).
Potato (Solanum tuberosum) and the eggplant (Solanum melongena) belong to the same genus because they are similar in many ways. However, they belong to two different species because they are not identical and they have reproductive barrier, that is, they cannot mate (cross or breed) with one another to produce fertile offspring. The members within a species can mate or cross. Thus all varieties of potatoes are in the species because they can interbreed to produce fertile offspring.

Why Use Scientific Names?

One reason for using Latin scientific name instead of common names is that common names can be confusing or misleading. For example the common name for a domestic cow is “la vache” in French, ‘die Kuh” in German, “la vaca” in Spanish, and “garoo” in Bengali. However, in all languages the scientific name is the same, and there is no confusion if we call the cow Bos taurus.

How life began

The theory is, about 15 billion years ago (15,000,000,000) the Universe was nothing more than a very small speck of mass. This speck was probably no bigger than the head of a pin. Everything in the Universe, all the galaxies, stars, planets, and even the matter making up your body, was squished up tightly in this tiny space.

Eventually, after a very long time, this speck exploded. All of a sudden, in a giant flash of unimaginable heat and power, the Universe was born. Over a period of billions and billions of years, the Universe became what we see today. Slowly stars began to form, and around these stars planets formed.

About 4.6 billion years ago our Earth looked very different than it does today. Instead of the beautiful blues, greens and whites of today, it would have looked red and orange. The surface of our planet was covered in oceans of hot lava. Instead of breathable oxygen, the atmosphere contained a mix of deadly poisons.

Still, there was no life. No fishes to fill these oceans, no plants to cover the rocky surface, no animals to graze the wilderness. Just a barren wet rock, orbiting the Sun. The Earth's atmosphere now contained a mix of very poisonous gases, including carbon monoxide, carbon dioxide, nitrogen oxides, hydrogen sulfide, methane, and cyanide. Breathing this air would cause death to most life forms as we know them.

What forces changed this barren wasteland into the beautiful garden that it is today?

Biologists believe that the process that created life is something called evolution. Earth's ancient oceans while lifeless, were filled with the chemicals needed for life. These chemicals were not alive, but they were there sloshing around. They call these chemicals “primordial soup.”
Instead of alphabet letters, this soup was filled with amino acids, proteins, lipids, and other basic components that are commonly found in lifeforms today.

The Miller Experiment About Life Began

When scientists set about solving the problem of how life began, they first looked for a source of the chemicals out of which living things are made. They devised an experiment, that under the primitive Earth’s conditions, the complex chemicals of life could form from simple, inorganic precursors. In 1953, Stanley Miller tested the theory:

  1.  Miller essentially put methane, or natural gas, ammonia, hydrogen gas, and water vapour into a beaker, based on the theory of what the primordial atmosphere would have looked like.
  2. Next, he simply put an electric charge through that mixture to simulate lightning going through an early atmosphere.
  3. After sitting around for a couple of days, all of a sudden there was this brown ‘soup’ all over the reaction vessel.
  4. On analysis of the vessel, rather than only having methane and ammonia, he actually had amino acids, which are the building blocks of proteins, fatty acids and other complex biological molecules.
  5. So the chemistry that Miller was discovering in this wonderful experiment was not some improbable chemistry, but a chemistry that is widely distributed throughout our solar system.
  6. The experiment used water (H2O), methane (CH4), ammonia (NH3) and hydrogen (H2).
  7. The chemicals were all sealed inside a sterile array of glass tubes and flasks connected together in a loop, with one flask half-full of liquid water and another flask containing a pair of electrodes.
  8. The liquid water was heated to induce evaporation, sparks were fired between the electrodes to simulate lightning through the atmosphere and water vapour, and then the atmosphere was cooled again so that the water could condense and trickle back into the first flask in a continuous cycle.
  9. The chemicals found in the 'soup' of Miller's experiment were found to be accumulated in lakes and ponds, where they changed, combined, and re-combined in millions of different ways over vast periods of time.
  10. Complexity increased until cell like structures appeared with the first major characteristics of life: the ability to reproduce and grow, feeding on materials from the ‘primordial soup’ in which they formed.

Life's Beginnings Organ of Earth

The presence of life in its present form would not be possible if the earliest life forms had not changed constantly, adapting to their environment and circumstances. Getting from the far left in figure 6 to the far right, where humans appeared, involved billions and billions of tiny changes, starting with the first cell that appeared about a billion years after the planet itself was formed.

  1. Two types of prokaryotic cells were present when life began and are still around today: Archaebacteria and bacteria. (Single celled)
  2. Prokaryotic cells increased in complexity over the time
  3. Eukaryotic cells first appeared approximately 1.5 billion years ago. Development of the green pigment chlorophyll enabled the use sunlight energy to make food from water and carbon dioxide, releasing oxygen into the Earth’s atmosphere for the first time.
  4. These, the first plants gave rise to the Plant Kingdom we know today. They not only maintain an oxygen rich atmosphere, but make the food upon which all other life depends.

Defination of biology

What is biology?
The word biology comes from the Greek words bios, which means life, and logos, which means thought. Thus, biology is the science that deals with the study of life.
A Brief History of Biology
Biology is a very old science. In fact, it probably began in prehistoric times.
Over thirty thousand years age, cave dwellers in France and Spain decorated the walls and ceilings of their caves with paintings of animals. These paintings show that the cave dwellers had closely observed the structure and behaviour of many animals.
When humans were mainly hunters of animals and gathers of edible plants, they studied biology at a simple level. They had to know the behaviour of their prey and, of course, the behaviour of animals that might prey on them. They also had to observe the growing conditions required by the various plants as they collected them for food.

When human began an agricultural way of life about ten thousand years ago, they had to know much more about plants and animals. For example, they had to know when to collect seeds for their next year’s crop, when to plants seeds, and how much moisture the various types pf plants needs. They also had to know what to feed their animals, how long the animals would live, and what might kill the animals. In a sense then, they were biologists because the studied living things. From such early beginnings came the science of biology.
Prehistoric humans had to rely on their senses alone to make observations. They had no laboratories, microscopes, dissecting kits, or other equipment.
What other living things is it like? While seeking answers to such questions, they probably discovered that the wide variety of living things had much in common, as well as many differences. They probably grouped similar living things and named each group. For example, they might have noted that all flying animals with feathers had much in common. They may have grouped them under one name such as birds. This process of grouping similar things is called classification.
These early Biologists also would have observed other patterns in nature, such as regular migration of birds and life cycles of plants and animals.
As century passed, humans became more knowledgeable and curious. They began to ask more complex questions such as: What is it made of? and, How is it put together?

Modern Biology and Biology Today

Modern Biology
Modern biology began during the 17th century when humans finally had the knowledge, skill, and equipment to seek answers to such questions. During that century Robert Hooke (1635-1703) and Anton van Leeuwenhoek (1632-1723) introduced a new tool, the microscope, to the scientific world. Another pioneer of modern biology was William Harvey (1578-1657), an English physician. He showed the importance in biological studies of well-designed experiments and careful observations. He traced the pattern of circulation of blood in humans, and showed that it travelled in one direction through the arteries and veins in a circular path.
The search for still more knowledge by curious scientists led them to ask even more complex question: What do the parts of a living thing do? How do the parts work? With the asking of such questions, biology truly came of age.

Biology Today

Modern biology is vast science. Over 1,500,000 different kinds or species of organisms have been identified and new ones are still being discovered. Biologists think that there may be over 2,000,000 different species on earth. They range in size and complexity from tiny bacteria to trees and humans. Because biology is such a large field, it is broken down into several subdivisions for easier study. These observations are formed according to the group of organisms being studied or the approach taken to the study of the organisms.

Modern biology is vast science. Over 1,500,000 different kinds or species of organisms have been identified and new ones are still being discovered. Biologists think that there may be over 2,000,000 different species on earth. They range in size and complexity from tiny bacteria to trees and humans.
The current rate of extinctions is about 1,000 times faster than normal, and human activities are responsible for the acceleration. At this rate, we will never know about most of the species that are alive on Earth today. Does that matter? 
Biologists think so. Whether or not we are aware of it, we humans are intimately connected with the world around us. We are profoundly changing the entire fabric of life on Earth. The changes are, in turn, affecting us in ways we are just beginning to fathom. Ironically, the more we learn about nature, the more we realize we have yet to learn.

Organism of Biology

Group of Organisms Being Studied
Examples of some of the main fields of biology formed using this method of subdivision are:
Botany           The study of plants.
Zoology          The study of animals.
Microbiology   The study of microscopic organisms.
Bacteriology   The study of bacteria.
Virology         The study of viruses.
Mycology        The study of fungi.
Entomology    The study of insects.
Ornithology    The study of birds.
Approaches taken to the Study of organisms
Examples of some of the main fields of biology formed using this second method of subdivision are:
Taxonomy      The classification of organisms.
Morphology    The study of the external form and structure of organisms.
Anatomy        The study of the internal structure of organisms.
Physiology      The study of the function of organisms.
Cytology         The study of cells.
Ecology          The study of the relationship of organisms to their environment.
Genetics         The study of inheritance

Pathology       The study of diseases.

What is the difference between a living and a nonliving thing?

You would have no trouble deciding that a dog running down the street was alive; nor would you have any trouble deciding that a stone was nonliving. However, if you ask yourself whether a bean seed, an apple, or a potato is living or nonliving, you may have problems deciding on the answer. All these appear just as nonliving as a stone. Yet we know that all three can produce a living plant. Since it seems unlikely that a nonliving thing can produce a living plant, we can assume that the bean seed, apple, and potato are living. What, then, are the characteristics of living things?

     What is life?

  1. Atom
  2. Molecules
  3.  Cells 
  4. Organisms
  5.  Communities
  6.  Ecosystem
  7.  The Biosphere

The building blocks—atoms—that make up all living things are the same ones that make up all nonliving things.
Atoms join as molecules. The unique properties of life emerge as certain kinds of molecules become organized into cells.
Higher levels of organization include multi celled organisms, populations, communities, ecosystems, and the biosphere.