Chapter 7_1: Nutrition in Plants

Carbohydrates, proteins, fats, vitamins and minerals are components of food. These components of food are necessary for our body and are called nutrients.

Nutrition is the mode of taking food by an organism and its utilisation by the body. The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic (auto = self; trophos = nourishment) nutrition. Therefore, plants are called autotrophs.

Animals and most other organisms take in ready-made food prepared by the plants. They are called heterotrophs (heteros = other).

PHOTOSYNTHESIS— FOOD MAKING PROCESS IN PLANTS

The synthesis of food in plants occurs in leaves, tiny pores present on the surface of the leaves. These pores are surrounded by ‘guard cells’. Such pores are called stomata.

The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesise (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis (Photo: light; synthesis: to combine).

During photosynthesis, chlorophyll containing cells of leaves, in the presence of sunlight, use carbon dioxide and water to synthesise carbohydrates.

During the process oxygen is released. The carbohydrates ultimately get converted into starch. The presence of starch in leaves indicates the occurrence of photosynthesis. The starch is also a carbohydrate.

The carbohydrates are made of carbon, hydrogen and oxygen. These are used to synthesise other components of food. But proteins are nitrogenous substances which contain nitrogen.

Slimy, green patches in ponds or in other stagnant water bodies. These are generally formed by the growth of organisms called algae.

Plants can then synthesise components of food other than carbohydrates such as proteins and fats.

The plant on which it climbs is called a host. Since it deprives the host of valuable nutrients, it is called a parasite.

Insect-eating plants are called insectivorous insectivorous plants.

Fungi, they have a different mode of nutrition. They secrete digestive juices on the dead and decaying matter and convert it into a solution. Then they absorb the nutrients from it. This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition.

Plants which use saprotrophic mode of nutrition are called saprotrophs.

Some organisms live together and share shelter and nutrients. This is called symbiotic relationship.

In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together. The fungus provides shelter, water and minerals to the alga and, in return, the alga provides food which it prepares by photosynthesis.

The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a soluble form. But Rhizobium cannot make its own food. So it lives in the roots of gram, peas, moongbeans and other legumes and provides them with nitrogen.

Chapter 7_2: Nutrition in Animals

Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body.

The breakdown of complex components of food into simpler substances is called digestion.

DIGESTION IN HUMANS

The canal can be divided into various compartments:

(1) the buccal cavity(2) foodpipe or oesophagus(3) stomach (4) small intestine(5) large intestine ending in therectum rectum and(6) the anus

These parts together form the alimentary canal (digestive tract).

The inner walls of the stomach and the small intestine, and the various glands such as salivary glands, the liver and the pancreas secrete digestive juices.

The process of taking food into the body is called ingestion. Our mouth has the salivary glands which secrete saliva. The saliva breaks down the starch into sugars. The digestive juices break down the proteins into simpler substances.

The liver is a reddish brown gland situated in the upper part of the abdomen on the right side. It is the largest gland in the body. It secretes bile juice that is stored in a sac called the gall bladder. The bile plays an important role in the digestion of fats.

The pancreatic juice acts on carbohydrates and proteins and changes them into simpler forms.

The digested food can now pass into the blood vessels in the wall of the intestine. This process is called absorption. The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus).

The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body. This is called assimilation.

The faecal matter is removed through the anus from time-to-time. This is called egestion.

In Animals, The grass and store it in a separate part of the stomach called rumen partially digested and is called cud. But later the cud returns to the mouth in small lumps and the animal chews it. This process is called rumination and these animals are called ruminants

The grass is rich in cellulose, a type of carbohydrate. Many animals, including humans, cannot digest cellulose.

Chapter 7_10: Respiration in Organisms

The process of breakdown of food in the cell with the release of energy is called cellular respiration. Cellular respiration takes place in the cells of all organisms.

The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps.

Chapter 7_11: Transportation in Animals and Plants

Blood is a liquid, which has cells of various kinds suspended in it, The fluid part of the blood is called plasma.

One type of cells are the red blood cells (RBC) which contain a red pigment called haemoglobin. Haemoglobin bind with oxygen and transports it to all the parts of the body and ultimately to all the cells. The presence of haemoglobin makes blood appear red. The blood also has white blood cells (WBC) which fight against germs that may enter our body.

The presence of another type of cells in the blood, called platelets.

So, two types of blood vessels are present in the arteries and veins of the body.

Arteries carry oxygen-rich blood from the heart to all parts of the body. Since the blood flow is rapid and at a high pressure, the arteries have thick elastic walls.

Throbbing is called the pulse and it is due to the blood flowing in the arteries.

The number of beats per minute is called the pulse rate. A resting person, usually has a pulse rate between 72 and 80 beats per minute

Veins are the vessels which carry carbon dioxide-rich blood from all parts of the body back to the heart. The veins have thin walls. There are valves present in veins which allow blood to flow only towards the heart.

The arteries divide into smaller vessels. On reaching the tissues, they divide further into extremely thin tubes called capillaries. The capillaries join up to form veins which empty into the heart.

The heart has four chambers. The two upper chambers are called the atria (singular: atrium) and the two lower chambers are called the ventricles. The partition between the chambers helps to avoid mixing up of blood rich in oxygen with the blood rich in carbon dioxide.

Animals such as sponges and Hydra do not possess any circulatory system. The water in which they live brings food and oxygen as it enters their bodies. The water carries away waste materials and carbon dioxide as it moves out. Thus, these animals do not need a circulatory fluid like the blood.

The English physician, William Harvey (A.D.1578–1657), discovered the circulation of blood.

The process of removal of wastes produced in the cells of the living organisms is called excretion. The parts involved in excretion forms the excretory system

A mechanism to filter the blood is required. This is done by the blood capillaries in the kidneys .

The wastes dissolved in water are removed as urine. From the kidneys, the urine goes into the urinary bladder through tube-like ureters. It is stored in the bladder and is passed out through the urinary opening at the end of a muscular tube called urethra. The kidneys, ureters, bladder and urethra form the excretory system.

An adult human being normally passes about 1–1.8 L of urine in 24 hours, and the urine consists of 95% water, 2.5 % urea and 2.5% other waste products.

As a result of kidney failure, waste products start accumulating in the blood. Such persons cannot survive unless their blood is filtered periodically through an artificial kidney. This process is called dialysis.

The food has to be transported to all parts of the plant. This is done by the vascular tissue called the phloem.

Thus, xylem and phloem transport substances in plants.

Chapter 7_12: Reproduction in Plants

The flowers perform the function of reproduction in plants. Flowers are the reproductive parts reproductive parts of a plant.

There are several ways by which plants produce their offspring. These are categorised into two types: (i) asexual and (ii) sexual reproduction. In asexual reproduction plants can give rise to new plants without seeds, whereas in sexual reproduction, new plants are obtained from seeds

Asexual reproduction

Bryophyllum (sprout leaf plant) has buds in the margins of leaves (Fig. 12.4). If a leaf of this plant falls on a moist soil, each bud can give rise to a new plant

SEXUAL REPRODUCTION

The flowers are the reproductive parts of a plant. The stamens are the male reproductive part and the pistil is the female reproductive part.

The flowers which contain either only the pistil or only the stamens are called unisexual flowers. The flowers which contain both stamens and pistil are called bisexual flowers. Corn, papaya and cucumber produce unisexual flowers, whereas mustard, rose and petunia have bisexual flowers.

Both the male and the female unisexual flowers may be present in the same plant or in different plants

Anther contains pollen grains which produce male gametes. A pistil consists of stigma, style and ovary. The ovary contains one or more ovules. The female gamete or the egg is formed in an ovule In sexual reproduction a male and a female gamete fuse to form a zygote

The transfer of pollen from the anther to the stigma of a flower is called pollination. If the pollen lands on the stigma of the same flower it is called self-pollination. When the pollen of a flower lands on the stigma of another flower of the same plant, or that of a different plant of the same kind, it is called cross-pollination.

Fertilisation

The cell which results after fusion of the gametes is called a zygote. The process of fusion of male and female gametes (to form a zygote) is called fertilisation. The zygote develops into an embryo.

Chapter 8_2: MICROORGANISMS: FRIEND AND FOE

There are other living organisms around us which we cannot see with eyes alone. These are called microorganisms or microbes.

Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae.

Viruses are also microscopic. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal. Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.

Diseases like dysentery and malaria are caused by protozoans whereas typhoid and tuberculosis (TB) are bacterial diseases.

Microorganisms may be single-celled like bacteria, some algae and protozoa, or multicellular, such as algae and fungi. They can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands.

Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.

Microorganisms have been used for the production of alcohol since ages.

Curd contains several microorganisms. Of these, the bacterium Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd.

Microorganisms are used for the large scale production of alcohol, wine and acetic acid (vinegar). Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices, etc.

This is the smell of alcohol as sugar has been converted into alcohol by yeast. This process of conversion of sugar into alcohol is known as fermentation.

Louis Pasteur discovered fermentation in 1857.

In 1929, Alexander Fleming was working on a culture of disease-causing bacteria. Suddenly he found the spores of a little green mould in one of his culture plates. He observed that the presence of mould prevented the growth of bacteria. In fact, it also killed many of these bacteria. From this the mould penicillin was prepared

Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria.

Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination.

Some bacteria and blue green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers.

Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens.

Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.

Female Anopheles mosquito, which carries the parasite of malaria. Female Aedes mosquito acts as carrier of dengue virus.

Anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus.

Robert Köch (1876) discovered the bacterium (Bacillus anthracis) which causes anthrax disease

Preservatives, we add salt or acid preservatives to pickles to prevent the attack of microbes. Sodium benzoate and sodium metabisulphite are common preservatives.

Pasteurized milk can be consumed without boiling as it is free from harmful microbes. The milk is heated to about 70 0 C for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur. It is called pasteurization.

Our atmosphere has 78% nitrogen gas. Nitrogen is one of the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acids and vitamins.

Chapter 8_8: CELL— STRUCTURE AND FUNCTIONS

Cells are assembled to make the body of every organism

Discovery of the Cell Robert Hooke in 1665 observed slices of cork under a simple magnifying device.

A billion is a thousand million. A trillion is a thousand billion

Organisms made of more than one cell are called multicellular (multi: many; cellular: cell) organisms.

The single-celled organisms are called unicellular (uni: one; cellular: cell) organisms

A white blood cell (WBC) in human blood is another example of a single cell which can change its shape. But while WBC is a cell, amoeba is a full-fledged organism capable of independent existence.

The smallest cell is 0.1 to 0.5 micrometre in bacteria. The largest cell measuring 170 mm ×130 mm, is the egg of an ostrich

Each organ is further made up of smaller parts called tissues. A tissue is a group of similar cells performing a specific function

The basic components of a cell are cell membrane, cytoplasm and nucleus. The cytoplasm and nucleus are enclosed within the cell membrane, also called the plasma membrane. The membrane separates cells from one another and also the cell from the surrounding medium. The plasma Membrane is porous and allows the movement of substances or materials both inward and outward.

It is the jelly-like substance present between the cell membrane and the nucleus. Various other components, or organelles, of cells are present in the cytoplasm. These are mitochondria, golgi bodies, ribosomes, etc.

Nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. A smaller spherical body in the nucleus. It is called the nucleolus.

Nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. The chromosomes can be seen only when the cell divides.

The nucleus of the bacterial cell is not well organised like the cells of multicellular organisms. There is no nuclear membrane. The cells having nuclear material without nuclear membrane are termed prokaryotic cells. The organisms with these kinds of cells are called prokaryotes (pro: primitive; karyon: nucleus). Examples are bacteria and blue green algae. The cells, like onion cells and cheek cells having well organised nucleus with a nuclear membrane are designated as eukaryotic cells. All organisms other than bacteria and blue green algae are called eukaryotes. (Eu: true; karyon: nucleus).

Vacuole could be single and big as in an onion cell. Cheek cells have smaller vacuoles. Large vacuoles are common in plant cells. Vacuoles in animal cells are much smaller.

Several small coloured bodies in the cytoplasm of the cells of Tradescantia leaf. They are scattered in the cytoplasm of the leaf cells. These are called plastids. They are of different colours. Some of them contain green pigment called chlorophyll. Green coloured plastids are called chloroplasts. They

provide green colour to the leaves. You may recall that chlorophyll in the chloroplasts of leaves, is essential for photosynthesis.

Chapter 8_9: REPRODUCTION IN ANIMALS

Doctors collect freshly released egg and sperms and keep them together for a few hours for IVF or in vitro fertilization (fertilization outside the body). In case fertilization occurs, the zygote is allowed to develop for about a week and then it is placed in the mother’s uterus. Babies born through this technique are called test-tube babies.

Cloning of an animal was successfully performed for the first time by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland. They cloned successfully a sheep named Dolly.

Chapter 8_10: REACHING THEAGE OF ADOLESCENCE

Growing up is a natural process. The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence

Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age. Since this period covers the ‘teens’ (13 to 18 or 19 years of age), adolescents are also called ‘teenagers’. In girls, adolescence may begin a year or two earlier than in boys.

The human body undergoes several changes during adolescence. These changes mark the onset of puberty.

At puberty, the voice box or the larynx begins to grow.

The changes which occur at adolescence are controlled by hormones. Hormones are chemical substances. These are secretions from endocrine glands, or endocrine system. The male hormone or testosterone begins to be released by the testes at the onset of puberty.

Once puberty is reached in girls, ovaries begin to produce the female hormone or estrogen which makes the breasts develop.

The production of these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland.

Endocrine glands release hormones into the bloodstream to reach a particular body part called target site.

All human beings have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these are the sex chromosomes, named X and Y. A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes (egg and sperm) have only one set of chromosomes. The unfertilised egg always has one X chromosome. But sperms are of two kinds. One kind has an X chromosome, and the other kind has a Y chromosome.

When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilisation, the zygote would develop into a male child.

Chapter 9_5: THE FUNDAMENTAL UNIT OF LIFE

Cells were first discovered by Robert Hooke in 1665.

Leeuwenhoek (1674), with the improved microscope, discovered the free living cells in pond water for the first time.

It was Robert Brown in 1831 that discovered the nucleus in the cell. Purkinje in 1839 coined the term ‘protoplasm’ for the fluid substance of the cell. The cell theory, that all the plants and animals are composed of cells and that the cell is the

basic unit of life, was presented by two biologists, Schleiden (1838) and Schwann (1839). The cell theory was further expanded by Virchow (1855) by suggesting that all cells arise

from pre-existing cells. With the discovery of the electron microscope in 1940, it was possible to observe and

understand the complex structure of the cell and its various organelles.

Every cell; plasma membrane, nucleus and cytoplasm.

The cell membrane is called a selectively permeable membrane.

Some substances like carbon dioxide or oxygen can move across the cell membrane by a process called diffusion. Diffusion plays an important role in gaseous exchange between the cells as well as the cell and its external environment.

Water also obeys the law of diffusion. The movement of water molecules through such a selectively permeable membrane is called osmosis.

If the medium surrounding the cell has a higher water concentration than the cell, meaning that the outside solution is very dilute, the cell will gain water by osmosis. Such a solution is known as a hypotonic solution

If the medium has exactly the same water concentration as the cell, there will be no net movement of water across the cell membrane. Such a solution is known as an isotonic solution

If the medium has a lower concentration of water than the cell, meaning that it is a very concentrated solution, the cell will lose water by osmosis. Such a solution is known as a hypertonic solution

Thus, osmosis is a special case of diffusion through a selectively permeable membrane.

Unicellular freshwater organisms and most plant cells tend to gain water through osmosis. Absorption of water by plant roots is also an example of osmosis. Thus, diffusion is important in exchange of gases and water in the life of a cell. Only living cells, and not dead cells, are able to absorb water by osmosis.

Different molecules move in and out of the cell through a type of transport requiring use of energy in the form of ATP.

The plasma membrane is flexible and is made up of organic molecules called lipids and proteins.

The flexibility of the cell membrane also enables the cell to engulf in food and other material from its external environment. Such processes are known as endocytosis. Amoeba acquires its food through such processes.

Plant cells, in addition to the plasma membrane, have another rigid outer covering called the cell wall. The cell wall lies outside the plasma membrane. The plant cell wall is mainly composed of cellulose. Cellulose is a complex substance and provides structural strength to plants.

When a living plant cell loses water through osmosis there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.

The nucleus has a double layered covering called nuclear membrane. The nuclear membrane has pores which allow the transfer of material from inside the nucleus to its outside, that is, to the cytoplasm.

The nucleus contains chromosomes, which are visible as rod-shaped structures only when the cell is about to divide. Chromosomes contain information for inheritance of features from parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules.

Chromosomes are composed of DNA and protein. DNA molecules contain the information necessary for constructing and organising cells. Functional segments of DNA are called genes. In a cell which is not dividing, this DNA is present as part of chromatin material. Chromatin material is visible as entangled mass of thread like structures.

An undefined nuclear region containing only nucleic acids is called a nucleoid. Such organisms, whose cells lack a nuclear membrane, are called prokaryotes (Pro = primitive or primary; karyote ≈karyon = nucleus).

Organisms with cells having a nuclear membrane are called eukaryotes.

The cytoplasm is the fluid content inside the plasma membrane. It also contains many specialised cell organelles. Some important examples of cell organelles which we will discuss now are: endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, plastids and vacuoles.

The endoplasmic reticulum (ER) is a large network of membrane-bound tubes and sheets. There are two types of ER– rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

RER looks rough under a microscope because it has particles called ribosomes attached to its surface. The ribosomes, which are present in all active cells, are the sites of protein manufacture. The manufactured proteins are then sent to various places in the cell depending on need, using the ER.

The SER helps in the manufacture of fat molecules, or lipids, important for cell function. Some of these proteins and lipids help in building the cell membrane. This process is known as membrane biogenesis. Some other proteins and lipids function as enzymes and hormones.

Thus, one function of the ER is to serve as channels for the transport of materials (especially proteins) between various regions of the cytoplasm or between the cytoplasm and the nucleus.

The Golgi apparatus, first described by Camillo Golgi, consists of a system of membrane-bound vesicles arranged approximately parallel to each other in stacks called cisterns.

Its functions include the storage, modification and packaging of products in vesicles.

Golgi carried out was a revolutionary method of staining individual nerve and cell structures. This method is referred to as the ‘black reaction’.

He shared the Nobel Prize in 1906 with Santiago Ramony Cajal for their work on the structure of the nervous system.

Lysosomes are also known as the ‘suicide bags’ of a cell. Structurally, lysosomes are membrane-bound sacs filled with digestive enzymes. These enzymes are made by RER.

Mitochondria are known as the powerhouses of the cell.

The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphopshate) molecules. ATP is known as the energy currency of the cell.

Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes. Therefore, mitochondria are able to make some of their own proteins.

Plastids are present only in plant cells. There are two types of plastids – chromoplasts (coloured plastids) and leucoplasts (white or colourless plastids). Like the mitochondria, plastids also have their own DNA and ribosomes.

Plastids containing the pigment chlorophyll are known as chloroplasts. Chloroplasts are important for photosynthesis in plants.

Chloroplasts also contain various yellow or orange pigments in addition to chlorophyll.

Leucoplasts are primarily organelles in which materials such as starch, oils and protein granules are stored.

Vacuoles are storage sacs for solid or liquid contents. Vacuoles are small sized in animal cells while plant cells have very large vacuoles.

Chapter 9_6: TISSUES

Chapter 9_7: DIVERSITY IN LIVING ORGANISMS

A eukaryotic cell has membrane-bound organelles, including a nucleus, which allow cellular processes to be carried out efficiently in isolation from each other

Further, nucleated cells would have the capacity to participate in making a multicellular organism because they can take up specialised functions. Therefore, this is a basic characteristic of classification. Cells that group together to form a single organism use the principle of division of labour.

All living things are identified and categorised on the basis of their body design in form and function

Charles Darwin first described this idea of evolution in 1859 in his book, The Origin of Species

Biodiversity means the diversity of life forms. It is a word commonly used to refer to the variety of life forms found in a particular region

The warm and humid tropical regions of the earth, between the tropic of Cancer and the tropic of Capricorn, are rich in diversity of plant and animal life. This is called the region of mega diversity.

Of the biodiversity of the planet, more than half is concentrated in a few countries – Brazil, Colombia, Ecuador, Peru, Mexico, Zaire, Madagascar, Australia, China, India, Indonesia and Malaysia

Biologists, such as Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) have tried to classify all living organisms into broad categories, called kingdoms. The classification Whittaker proposed has five kingdoms: Monera, Protista, Fungi, Plantae and Animalia, and is widely used.

The modification Woese introduced by dividing the Monera into Archaebacteria (or Archaea) and Eubacteria (or Bacteria) is also in use. Broadly, a species includes all organisms that are similar enough to breed and perpetuate

Arolus Linnaeus in the eighteenth century. The scientific name of an organism is the result of the process of classification which puts it along with the organisms it is most related to.

Certain conventions are followed while writing the scientific names: 1. The name of the genus begins with a capital letter. 2. The name of the species begins with a small letter. 3. When printed, the scientific name is given in italics. 4. When written by hand, the genus name and the species name have to be underlined separately.

Chapter 9_13: WHY DO WE FALL ILL

Some diseases last for only very short periods of time, and these are called acute diseases. We all know from experience that the common cold lasts only a few days. Other ailments can last for a long time, even as much as a lifetime, and are called chronic diseases

Robin Warren (born 1937) and Barry Marshall (born 1951), showed that patients could be cured of peptic ulcer (a bacterium, Helicobacter pylori, was responsible for peptic ulcers) only when the bacteria were killed off from the stomach. For this achievement, Marshall and Warren (seen in the picture) received the Nobel Prize for physiology and medicine in 2005.

An active immune system recruits many cells to the affected tissue to kill off the disease-causing microbes. This recruitment process is called inflammation.

Chapter 10_6: Life Processes

Oxidising-reducing reactions are some of the most common chemical means to break-down molecules. For this, many organisms use oxygen sourced from outside the body. The process of acquiring oxygen from outside the body, and to use it in the process of break-down of food sources for cellular needs, is what we call respiration

The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act. Bile salts break them down into smaller globules increasing the efficiency of enzyme action. The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats. The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.

The break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm. Further, the pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration. Breakdown of pyruvate using oxygen takes place in the mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide.

The other product is water. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration.

The force that blood exerts against the wall of a vessel is called blood pressure. This pressure is much greater in arteries than in veins. The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg. Blood pressure is measured with an instrument called sphygmomanometer. High blood pressure is also called hypertension.

Chapter 10_7: Control and Coordination

All information from our environment is detected by the specialised tips of some nerve cells. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell.

Nervous tissue is made up of an organised network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

Nerves from all over the body meet in a bundle in the spinal cord on their way to the brain. Reflex arcs are formed in this spinal cord itself, although the information input also goes on to reach the brain

Thinking involves more complex mechanisms and neural connections. These are concentrated in the brain, which is the main coordinating centre of the body. The brain and spinal cord constitute the central nervous system. They receive information from all parts of the body and integrate it.

The brain has three such major parts or regions, namely the fore-brain, mid-brain and hind-brain.

The fore-brain is the main thinking part of the brain. It has regions which receive sensory impulses from various receptors.

Many of these involuntary actions are controlled by the mid-brain and hind-brain. All these involuntary actions including blood pressure, salivation and vomiting are controlled by the medulla in the hind-brain.

Think about activities like walking in a straight line, riding a bicycle, picking up a pencil. These are possible due to a part of the hind-brain called the cerebellum.

Iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxin

Growth hormone is one of the hormones secreted by the pituitary.

Chapter 10_8: Reproduction:

The chromosomes in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules. The DNA in the cell nucleus is the information source for making proteins.

Therefore, a basic event in reproduction is the creation of a DNA copy. Cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell, and they will need to be separated from each other

For unicellular organisms, cell division, or fission, leads to the creation of new individuals.

Many bacteria and protozoa simply split into two equal halves during cell division.

Simple animals like Hydra and Planaria can be cut into any number of pieces and each piece grows into a complete organism. This is known as regeneration

Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.

The tiny blob-on-a-stick structures are involved in reproduction. The blobs are sporangia, which contain cells, or spores, that can eventually develop into new Rhizopus individuals

Stamens and carpels are the reproductive parts of a flower which contain the germ-cells.

The seed contains the future plant or embryo which develops into a seedling under appropriate conditions. This process is known as germination.

Chapter 10_9: Heredity and Evolution

Origin of life on earth Darwin’s theory of evolution tells us how life evolved from simple to more complex forms and Mendel’s experiments give us the mechanism for the inheritance of traits from one generation to the next. But neither tells us anything about how life began on earth in the first place.

Molecular Phylogeny: Trace the changes in DNA backwards in time and find out where each change diverged from the other.

Chapter 12_11 BIOTECHNOLOGY: PRINCIPLES AND PROCESSES

Biotechnology deals with techniques of using live organisms or enzymes from organisms to produce products and processes useful to humans

The European Federation of Biotechnology (EFB) has given a definition

‘The integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services’.

The two core techniques that enabled birth of modern biotechnology are:

(i) Genetic engineering: Techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism.

(ii) Maintenance of sterile (microbial contamination-free) ambience in chemical engineering processes to enable growth of only the desired microbe/eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc

The techniques of genetic engineering which include creation of recombinant DNA, use of gene cloning and gene transfer.

In a chromosome there is a specific DNA sequence called the origin of replication, which is responsible for initiating replication. Therefore, for the multiplication of any alien piece of DNA in an organism it needs to be a part of a chromosome(s) which has a specific sequence known as ‘origin of replication’.

Thus, an alien DNA is linked with the origin of replication, so that, this alien piece of DNA can replicate and multiply itself in the host organism. This can also be called as cloning or making multiple identical copies of any template DNA

The cutting of DNA at specific locations became possible with the discovery of the so-called molecular scissors’– restriction enzymes.

There are three basic steps in genetically modifying an organism —

(i) identification of DNA with desirable genes; (ii) introduction of the identified DNA into the host; (iii) Maintenance of introduced DNA in the host and transfer of the DNA to its progeny.

Genetic engineering or recombinant DNA technology can be accomplished only if we have the key tools, i.e., restriction enzymes, polymerase enzymes, ligases, vectors and the host organism.

In the year 1963, the two enzymes responsible for restricting the growth of bacteriophage in Escherichia coli were isolated. One of these added methyl groups to DNA, while the other cut DNA. The later was called restriction endonuclease Hind II always cut DNA molecules at a particular point by recognising a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for Hind II.

Restriction enzymes belong to a larger class of enzymes called nucleases.

These are of two kinds; exonucleases and endonucleases.

Exonucleases remove nucleotides from the ends of the DNA whereas; endonucleases make cuts at specific positions within the DNA.

Restriction endonucleases are used in genetic engineering to form ‘recombinant’ molecules of DNA, which are composed of DNA from different sources/genomes. When cut by the same restriction enzyme, the resultant DNA fragments have the same kind of ‘sticky-ends’ and, these can be joined together (end-to-end) using DNA ligases

Separation and isolation of DNA fragments:

The cutting of DNA by restriction endonucleases results in the fragmentes of DNA. These fragments can be separated by a technique known as gel electrophoresis.

The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as elution. The DNA fragments purified in this way are used in constructing recombinant DNA by joining them with cloning vectors.

Vectors used at present, are engineered in such way that they help easy linking of foreign DNA and selection of recombinants from non-recombinants.

Bacteriophages because of their high number per cell, have very high copy numbers of their genome within the bacterial cells. Some plasmids may have only one or two copies per cell whereas others may have 15-100 copies per cell

Origin of replication (ori): if one wants to recover many copies of the target DNA it should be cloned in a vector whose origin support high copy number.

Selectable marker: the vector requires a selectable marker, which helps in identifying and eliminating non transformants and selectively permitting the growth of the transformants.

Cloning sites: In order to link the alien DNA, the vector needs to have very few, preferably single, recognition sites for the commonly used restriction enzymes.In this, a recombinant DNA is inserted within the coding sequence of an enzyme, â-galactosidase. This results into inactivation of the enzyme, which is referred to as insertional inactivation.

Vectors for cloning genes in plants and animals : Agrobacterioum tumifaciens, a pathogen of several dicot plants is able to deliver a piece of DNA known as ‘T-DNA’ to transform normal plant cells into a tumor and direct these tumor cells to produce the chemicals required by the pathogen. Similarly, retroviruses in animals have the ability to transform normal cells into cancerous cells.

In a method known as micro-injection, recombinant DNA is directly injected into the nucleus of an animal cell.

In another method, suitable for plants, cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA in a method known as biolistics or gene gun.

And the last method uses ‘disarmed pathogen’ vectors, which when allowed infecting the cell, transferring the recombinant DNA into the host.

PROCESSES OF RECOMBINANT DNA TECHNOLOGY

DNA is enclosed within the membranes; we have to break the cell open to release

DNA along with other macromolecules such as RNA, proteins, polysaccharides and also lipids. This can be achieved by treating the bacterial cells/plant or animal tissue with enzymes such as lysozyme (bacteria), cellulose (plant cells), chitinase (fungus)

The RNA can be removed by treatment with ribonuclease whereas proteins can be removed by treatment with protease, other molecules can be removed by appropriate treatments and purified DNA ultimately precipitates out after the addition of chilled ethanol.

Cutting of DNA at Specific Locations: Restriction enzyme digestions are performed by incubating purified DNA molecules with the restriction enzyme the cut out ‘gene of interest’ from the source DNA and the cut vector with space are mixed and ligase is added. This results in the preparation of recombinant DNA

Amplification of Gene of Interest using PCR: PCR stands for Polymerase Chain Reaction. Polymerase chain reaction (PCR) : Each cycle has three steps: (i) Denaturation; (ii) Primer annealing; and (iii) Extension of primers

Insertion of Recombinant DNA into the Host Cell/Organism: Since, due to ampicillin resistance gene, one is able to select a transformed cell in the presence of ampicillin. The ampicillin resistance gene in this case is called a selectable marker

Obtaining the Foreign Gene Product: Any protein encoding gene is expressed in a heterologous host, is called a recombinant protein.

To produce in large quantities, the development of bioreactors, where large volumes (100-1000 litres) of culture can be processed, was required. A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions (temperature, pH, substrate, salts, vitamins, oxygen).

The processes include separation and purification, which are collectively referred to as downstream processing.

Chapter 12_12: BIOTECHNOLOGY AND ITS APPLICATIONS

The applications of biotechnology include therapeutics, diagnostics, and genetically modified crops for agriculture, processed food, bioremediation, waste treatment, and energy production

Three critical research areas of biotechnology are:

(i) Providing the best catalyst in the form of improved organism usually a microbe or pure enzyme.

(ii) Creating optimal conditions through engineering for a catalyst to act, and(iii) Downstream processing technologies to purify the protein/organic compound.

BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE

For increasing food production

(i) agro-chemical based agriculture(ii) organic agriculture; and(iii) Genetically engineered crop-based agriculture.

Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO)

GM plants have been useful in many ways. Genetic modification has:

(i) Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).(ii) Reduced reliance on chemical pesticides (pest-resistant crops).(iii) Helped to reduce post-harvest losses.(iv) Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of

soil).(v) Enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice. In addition to these uses,

GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceutical

BT toxin is produced by a bacterium called Bacillus thuringiensis (Bt for short). BT toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides; in effect created a bio-pesticide. Examples are Bt cotton, Bt corn, rice, tomato, potato and soyabean etc

A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi). RNAi takes place in all eukaryotic organisms as a method of cellular defense.

Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant. The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells. These two RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA of the nematode. The consequence was that the parasite could not survive in a transgenic host expressing specific interfering RNA. The transgenic plant therefore got itself protected from the parasite.

BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE

At present, about 30 recombinant therapeutics have been approved for human-use the world over. In India, 12 of these are presently being marketed.

Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges.

In mammals, including humans, insulin is synthesised as a prohormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin.

The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form.

Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo.

The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase.

Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.

PCR is now routinely used to detect HIV in suspected AIDS patients. It is being used to detect mutations in genes in suspected cancer patients too. It is a powerful technique to identify many other genetic disorder.

ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.

Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals.

In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre). The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk

The Indian Government has set up organisations such as GEAC (Genetic Engineering Approval Committee), which will make decisions regarding the validity of GM research and the safety of introducing GM-organisms for public services.

Thousands of years in Asia’s agricultural history, there are an estimated 200,000 varieties of rice in India alone. The diversity of rice in India is one of the richest in the world. Basmati rice is distinct for its unique aroma and flavour and 27 documented varieties of Basmati are grown in India.

In 1997, an American company got patent rights on Basmati rice through the US Patent and Trademark Office. This allowed the company to sell a ‘new’ variety of Basmati, in the US and abroad.

Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment.

The Indian Parliament has recently cleared the second amendment of the Indian Patents Bill, which takes such issues into consideration, including patent terms emergency provisions and research and development initiative.

Chapter 11: The Human Eye and the Colourful World

The ability of the eye lens to adjust its focal length is called accommodation.

Sometimes, the crystalline lens of people at old age becomes milky and cloudy. This condition is called cataract. This causes partial or complete loss of vision. It is possible to restore vision through a cataract surgery

A normal eye can see objects clearly that are between 25 cm and infinity.

A human being has a horizontal field of view of about 150° with one eye and of about 180° with two eyes.

Our two eyes are positioned on the front of our heads, and it thus reduces our field of view in favour of what is called stereopsis.

Myopia is also known as near-sightedness. A person with myopia can see nearby objects clearly but cannot see distant objects distinctly

Hypermetropia is also known as far-sightedness. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly. The near point, for the person, is farther away from the normal near point (25 cm).

Presbyopia The power of accommodation of the eye usually decreases with ageing. For most people, the near point gradually recedes away. They find it difficult to see nearby objects comfortably and distinctly without corrective eye-glasses.

The acronym VIBGYOR will help you to remember the sequence of colours. The band of the coloured components of a light beam is called its spectrum.

The splitting of light into its component colours is called dispersion.

Any light that gives a spectrum similar to that of sunlight is often referred to as white light.

The phenomenon of scattering of light by the colloidal particles gives rise to Tyndall effect. This phenomenon is seen when a fine beam of sunlight enters a smoke-filled room through a small hole.

At noon, the Sun appears white as only a little of the blue and violet colours are scattered. Near the horizon, most of the blue light and shorter wavelengths are scattered away by the particles. Therefore, the light that reaches our eyes is of longer wavelengths. This gives rise to the reddish appearance of the Sun.