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The Digestive System     Digestive System in Various Organism Single-celled organisms can directly take in nutrients from their outside environment. Multicellular animals, with most of their cells removed from direct contact with the outside environment, have developed specialized structures for obtaining and breaking down their food.   Animals Depend on Two Processes: Feeding and Digestion

• Animals are heterotrophs, they must absorb nutrients or ingest food sources.

 

• Injective eaters, majority of animals, use a mouth to ingest food.

 

• Absorptive feeders, such as tapeworms, live in a digestive system of another animal and absorb nutrients from that animal directly through their body wall.

 

• Filter feeders, such as oysters and mussels, collect small organisms and particles from the surrounding water.

 

• Substrate feeders, such as earthworms and termites, eat the material (dirt or wood) they burrow through.

 

• Fluid feeders, such as aphids, pierce the body of a plant or animal and withdraw fluids.

  Stages in the Digestive Process Food for the most part consists of various organic macromolecules such as starch, proteins and fats. These molecules are polymers made of individual monomer units breaking these large molecules into smaller components involves:  

movement: propels food through the digestive system

 

secretion: release of digestive juices in response to a specific stimulus

 

digestion: breakdown of food into molecular components small enough to cross the plasma membrane

 

absorption: passage of the molecules into the body’s interior and their passage throughout the body

 

elimination: removal of undigested food and wastes

  Three processes occur during what we loosely refer to as “digestion”.   Digestion proper, which is the mechanical and chemical breakdown of food into particles/molecules small enough to pass into the blood.   Absorption is the passage of food monomers into the blood stream. Assimilation is the passage of the food molecules into body cells,   The Human Digestive System The human digestive system, is a coiled, muscular tube (6-9 meters Song when fully extended) stretching from the mouth to the anus. Several specialized compartments occur along this length: mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus. Accessory digestive organs are connected to the main system by a series of ducts: salivary glands, parts of the pancreas, and the liver and gall bladder (biliary system).                                (A) The Mouth and Pharynx Mechanical breakdown begins in the mouth by chewing (teeth) and actions of the tongue. Chemical breakdown of starch by production of salivary amylase from the salivary glands. This mixture of food and saliva is then pushed into the pharynx and esophagus. The esophagus is a muscular tube whose muscular contractions (peristalsis) propel food to the stomach.   In the mouth, teeth, jaws and the tongue begin more...

The Excretory System     Excretory Systems in Various Animals Excretory systems regulate the chemical composition of body fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Components of this system in vertebrates include the kidneys, liver, lungs, and skin.   Not all animals use the same routes or excrete their wastes the same way as humans do. Excretion applies to metabolic waste products that cross a plasma membrane. Elimination is the removal of feces.   (A) Nitrogen Wastes Nitrogen wastes are by product of protein metabolism. Amino groups are removed from ammo acids prior to energy conversion. The  (amino group) combines with a hydrogen ion (proton) to form ammonia   Ammonia is very toxic and usually is excreted directly by marine animals. Terrestrial animals usually need to conserve water. Ammonia is converted to urea, a compound the body can tolerate at higher concentrations than ammonia. Birds and insects secrete uric acid that they make through large energy expenditure but little water loss.   Amphibians and mammals secrete urea that they form in their liver. Amino groups are turned into ammonia, which in turn is converted to urea, dumped into the blood and concentrated by the kidneys.   (B) Water and Salt Balance The excretory system is responsible for regulating water balance in various body fluids.   Osmoregulation refers to the state aquatic animals are in: they are surrounded by freshwater and must constantly deal with the influx of water Animals, such as crabs, have an internal salt concentration very similar to that of the surrounding ocean. Such animals are known as osmocon-formers, as there is little water transport between the inside of the animal and the isotonic outside environment.   Marincomposltione vertebrates, however have internal concentrations of salt that are about one-third of the surrounding seawater. They are said to be osmoregulators. Osmoregulators face two problems: prevention of water loss from the body and prevention of salts diffusing into the body. Fish deal with this by passing water out of their tissues through their gills by osmosis and salt through their gills by active transport.   Cartilaginous fish have a greater salt concentration than seawater, causing water to move into the shark by osmosis; this water is used for excretion. Freshwater fish must prevent water gain and salt loss. They do not drink water, and have their skin covered by a thin mucus. Water enters and leaves through the gills and the fish excretory system produces large amounts of dilute urine. Terrestrial animals use a variety of methods to reduce water loss: living in moist environments, developing impermeable body coverings, production of more concentrated urine. Water loss can be considerable: a person in a 100 degree F temperature loses 1 liter of water per hour.   Excretory System Functions

Collect water and filter body fluids.

Remove and concentrate waste products from body fluids and return other substances to body fluids as necessary for homeostasis.

Eliminate excretory products from the more...

Photosynthesis     Structure of leaf

• Plants are the only photosynthetic organisms to have leaves (and not all plants have leaves). A leaf may be viewed as a solar collector crammed full of photosynthetic cells.

                                                     

• The raw materials of photosynthesis, water and carbon dioxide, enter the cells of the Seat, and the products of photosynthesis, sugar and oxygen, leave the leaf.

 

• Water enters the root and is transported up to the leaves through specialized plant cells known as xylene.

 

• Land plants must guard against drying out (desiccation) and so have evolved specialized structures known as stomata to allow gas to enter and leave the leaf. Carbon dioxide cannot pass through the protective waxy layer covering the leaf (cuticle), but it can enter the leaf through an opening (the stoma; plural = stomata; Greek for hole) flanked by two guard cells.

 

• Likewise, oxygen produced during photosynthesis can only pass out of the leaf through the opened stomata.

 

• Unfortunately for the plant, while these gases are moving between the inside and outside of the leaf, a great deal water is also lost.

 

• Cottonwood trees, for example, will lose 100 gallons of water per hour during hot desert days. Carbon dioxide enters single-celled and aquatic autotrophs through no specialized structures.

  Chlorophyll and Accessory Pigments

• A pigment is any substance that absorbs light-The color of the pigment comes from the wavelengths of light reflected (in other words, those not absorbed).

 

• Chlorophyll, the green pigment common to all photosynthetic cells, absorbs all wavelengths of visible light except green, which it reflects to be detected by our eyes.

 

• Black pigments absorb all of the wavelengths that strike them.

 

• White pigments/lighter colors reflect all or almost all of the energy striking them. Pigments have their own characteristic absorption spectra, the absorption pattern of a given pigment.

 

• Chlorophyll is a complex molecule. Several modifications of chlorophyll occur among plants and other photosynthetic organisms. All photosynthetic organisms (plants, certain protistans, prochlorobacteria, and cyanobacteria) have chlorophyll a. Accessory pigments absorb energy that chlorophyll a does not absorb. Accessory pigments include chlorophyll b (also c, d, and e in algae and protistans), xanthophyll’s, and carotenoids (such as beta-carotene). Chlorophyll absorbs its energy from the Violet-Blue and Reddish orange-Red wavelengths, and little from the intermediate (Green-Yellow-Orange) wavelengths.

  The Carbon Cycle

• Plants may be viewed as carbon sinks, removing carbon dioxide from the atmosphere and oceans by fixing it into organic chemicals. Plants also produce some carbon dioxide by their respiration, but this is quickly used by photosynthesis. Plants also convert energy from light into chemical more...

Diversity in Living Organisms     Differentiation in Plants   (i) Thallophyta  

• Plants that do not have well differentiated body design fall in this group.

 

• The plants in this group are commonly called algae. These plants are predominantly aquatic.

              E.g.: Spirogyra, cladophora and chara.   (ii) Bryophyte  

• These are called the amphibians of the plant kingdom. There is no specialized tissue for the conduction of water and other substances from one past of the plant body to another.

              E.g.: moss (fumaria) and marchantia   (iii) Pteridopheysta  

• In this group plant body is differentiated into roots, stem and leaves and has specialized tissue for the conduction of water and other substances from one plant of the plant body to another.

 E.g- marsilea, ferns, and horse tails.   (iv) Gymnosperms  

• The plant of this group bear naked seeds and one usually perennial and evergreen and woody.

 E.g.: pines such as deodar.   (v) Angiosperms  

• The seeds develop inside an organ which is modified to become a fruit. These are also called flowering plants.

 

• Plant embryos in seeds have structures called cotyledons. Cotyledons are called seed leaves because in many instances they emerge and become green the seed germinates.

 

• The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed.

 

• Plants with seeds having a single cotyledon are called monocotyledons or monocots. Eg- paphiopedilum.

 

• Plants with seeds having two cotyledons are called dicots. Eg- ipomoce.

  Differentiation of Animals   (i) Porifera   These are non-mobile animals attached to some solid support. There are holes or pores all over the body. These lead to a canal system that helps in circulating water throughout the body to bring in food and  They are commonly called sponges mainly found in marine habitats.   (ii) Coelenterate

• These are animals living in water. The body is made up of two layers of cells. One makes up cells on the outside of the body and the other makes the inner living of the body.

 

• Some of these species live in colonies while others have a solitary life e.g. span (Hydra) jellyfish are common example.

  (iii) Platyhelminthes  

• There are three layers of cells from which different tissues can be made. This allow outside and inside body linings as well as some organs to be made.

 

• Thus there is some degree of tissues formation.

 

• They are either free living or parasitic. e.g. Planarians, liver flukes.

  (iv) Nematode  

• These are very familiar as parasitic worms more...

The Animal Kingdom     Invertebrates Of the million or more animal species in the world, more than 98% are invertebrates. Invertebrates don’t have an internal skeleton made of bone. Many invertebrates have a fluid-filled, hydrostatic skeleton, like the jelly fish or worm. Others have a hard outer shell, like insects and crustaceans. There are many types of invertebrates. The most common invertebrates include the protozoa, annelids, echinoderms, mollusks and arthropods. Arthropods include insects, crustaceans and arachnids.   (i) Protozoa Protozoa are simple, single-celled animals. They are the smallest of all animals. Most protozoa are microscopic in size, and can only be seen under a microscope. However, they do breathe, move and reproduce like multicelled animals.   There are several types of protozoa. The amoebas are dear, shapeless cells. Flagellates have a body shape looking like a hair. Although we can't see them, protozoa do a lot for us. Protozoa play a useful role in the food chain as a source of food for fish and other animals. Some protozoa are helpful to humans by eating dangerous bacteria. Unfortunately, other protozoa are parasites and can be harmful to humans by transmitting disease.   Protozoa eat tiny algae and bacteria. Some protozoa absorb food through their cell membrane. Others surround and engulf their food or have openings to collect food. They digest their food in stomach-like compartments called vacuoles. Protozoa take in oxygen and give off carbon dioxide through the cell membrane. Protozoa reproduces by splitting in half.   (ii) Worms and Leeches There are about 9,000 species of Annelids known today, including worms and leeches. They can be found almost anywhere in the world. Annelids have existed on Earth for over 120 million years.   Annelids have bodies that are divided into segments. They have very well-developed internal organs. One common characteristic of annelids is that they don't have any limbs.   Some annelids may have long bristles. Others have shorter bristles and seem smooth, like the earthworm.   There are many types of worms. Commonly known worms include earthworms, roundworms and flatworms. Most worms are small, measuring fractions of an inch to several inches long. Other worms, such as the ribbon worm, can grow up to 100 feet in length. Some worms are considered Parasites, in that they live inside the human body.   (iii) Mollusks Mollusks were among the first inhabitants of the Earth. Fossils of mollusks have been found in rocks and date back over 500 million years. Mollusk fossils are usually well preserved because of their hard shell. Most mollusks have a soft, skin-like organ covered with a hard outside shell. Some mollusks live on land, such as the snail and slug. Other mollusks live in water, such as the oyster, mussel, clam, squid and octopus.   Land living mollusks, like the snail, move slowly on a flat sole called a foot. Ocean living mollusks move or swim by jet propulsion. They propel themselves by ejecting water from their body. For example, more...

Acid, Base and Salts     1.  Acid

• Then word ‘acid’ is derived from a Latin word, which means “sour”. The sour taste of most of the fruits and vegetables is due to various types of acids present in them. The digestive fluids of most of the animals and humans also contain acids.

 

• An acid is a compound, which on dissolving in water yields hydronium ions as the only positive ions. The characteristic property of an acid is due to the presence of these hydronium ions.

 

• Acids are compounds that contain Hydrogen (Hydrochloric, HCl; Sulphuric, Nitric, However, not all compounds that contain Hydrogen are acids (Water, Methane, Acids are usually compounds of nonmetals with Hydrogen and sometimes Oxygen.

 

• Acids can be classified in various ways, depending on the factors mentioned below:

 

Classification Based on the Strength of the acid.

 

Classification Based on the Basicity of the Acid.

 

Classification Based on the concentration of the acid.

 

Classification Based on the presence of Oxygen.

 

• The strength of an acid depends on the concentration of the hydronium ions present in a solution. Greater the number of hydronium ions present, greater is the strength of acid. However, some acids do not dissociate to any appreciable extent in water such as carbonic acid. Therefore, these acids will have a low concentration of hydronium ions.

 

• Strong Acid: An acid, which dissociates completely or almost completely in water, is classified as a strong acid. It must be noted that in these acids all the hydrogen ions (H+) combine with water molecule and exist as hydronium ions Examples of strong acids are: hydrochloric acid, sulphuric acid, nitric acid etc.

 

• Weak Acid: An acid that dissociates only partially when dissolved in water, is classified as a weak acid. Most of the molecules remain in solution in molecular from itself in such acid. Examples are: acetic acid, formic acid, carbonic acid etc.

 

• Acids are generally sour in taste. Special type of substances are used to test whether a substance is acidic or basic. These substances are known as indicators. The indicators change their colour when added to a solution containing an acidic or a basic substance. Turmeric, litmus, china rose petals (Gudhal), etc., are some of the naturally occurring indicators.

 

• The most commonly used natural indicator is litmus. It is extracted from lichens. It has a mauve (purple) colour in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue. It is available in the form of a solution, or in the form of strips of paper known as litmus paper. Generally, it is available as red and blue litmus paper.

 

• The solutions more...

Atomic Structure    

• An atom is the smallest particle of the element that can exist independently and retain all its chemical properties. Atoms are made up of fundamental particles: electrons, protons and neutrons.

 

• Dalton’s Atomic Theory: John Dalton provided a simple theory of matter to provide theoretical justification to the laws of chemical combinations in 1805. The basic postulates of the theory are:

 

• All substances are made up of tiny, indivisible particles called atoms.

 

• Atoms of the same elements are identical in shape, size, mass and other properties.

 

• Each elements is composed of its own kind of atoms. Atoms of different elements are different in all respects.

 

• Atom is the smallest unit that takes part in chemical combinations.

 

• Atoms combine with each other in simple whole number ratios to form compound atoms called molecules.

 

• Atoms cannot be created, divided or destroyed during any chemical or physical change.

 

• Representation of an Atom by a Symbol: Dalton was the first scientist to use the symbols for elements in a very specific sense. When he used a symbol for an element he also meant a definite quantity of that element, that is, one atom of that element. A symbol signifies a shorthand representation of an atom of an element. The symbol of any element is based the English name or Latin name (written in English alphabets) and many of the symbols are the first one or two letters of the element’s name in English. The first letter of a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase). Examples are: (i) hydrogen- H (ii) aluminium- Al and not AL (iii) cobalt- Co and not CO. Symbols of some elements are formed from the first letter of the name and a letter, appearing later in the name. Examples are (i) chlorine, Cl, (ii) zinc, Zn etc.

 

• Other symbols have been taken from the names of elements in Latin, German or Greek. For example, the symbol of iron is Fe from its Latin name ferrum, sodium is Na form natrium, potassium is K from kalium. Therefore, each element has a name and a unique chemical symbol.

 

• Size of the Atom / Elements: Atoms are very small, they are smaller than anything that we can imagine or compare with. One hydrogen atom, the smallest atom known, is approximately mm in diameter. Atomic radius is measured in nanometers. 1 m = 109 nm.

 

• Atomic Mass: The mass of a particular atom is taken as a standard unit and the masses of other atoms are related to this standard. Hydrogen being the lightest element and being more...

Chemical Bonding    

• Atoms are made up of three smaller particles called protons, neutrons and electrons. The protons and neutrons are found in the nucleus of the atom. Protons have a single positive charge. This is called the Atomic Number of an atom. The Atomic Number tells us the number of electrons that the atom contains. It is these electrons that determine the chemical properties of the atom and the way it combines with other atoms to form specific compounds. Electrons have a single negative charge. Normally, atoms are electrically neutral so that the number of electrons is equal to the number of protons.

 

• Electrons orbit around the nucleus. Electrons cannot orbit the nucleus of an atom in any orbit. The electrons are restricted to specific paths called orbitals or shells. Each shell can only hold a certain number of electrons. When a shell is full, no more electrons can go into that shell. The key to the properties of atom is the electrons in the outer shell. A complete outer shell of electrons is a very stable condition for an atom.

 

• Valency: Hydrogen is the simplest element. It has one electron. Its outer shell only holds two electrons. Valency can be simply defined as the number of Hydrogen atoms that an element can combine with. The atoms with full electron shells (Helium, Neon, Argon) are chemically inert forming few compounds. The atoms don’t even interact with each other very much. These elements are gases with very low boiling points. The atoms with a single outer electron or a single missing electron are all highly reactive. Sodium is more reactive than Magnesium. Chlorine is more reactive than Oxygen Generally speaking, the closer an atoms is to having a full electron shell, the more reactive it is. Atoms with one outer electron are more reactive than those with two outer electrons, etc. Atoms that are one electron short of a full shell are more reactive than those that are two short.

 

• Chemical bonds are what hold atoms together to form the more complicated aggregates that we know as molecules and extended solids. The forces that hold bonded atoms together are basically just the same kinds of electrostatic attractions that bind the electrons of an atom to its positively-charged nucleus. Chemical bonding occurs when one or more electrons are simultaneously attracted to two nuclei

 

• Mainly 3 Types of bonds can be present in Chemical Compounds.

 

Electrovalent or lonic Bond: It is formed by Transferring of Electrons between 2. Atoms. These types of bonds are mainly formed between Metals and Non - Metals. These compounds exist in solid form. These compounds have high boiling Point. Melting Point and thermal stability.

 

Covalent Bond: It is formed by equal sharing of Electrons between 2 Atoms. This type of bond is mainly formed between non more...

Chemical Reactions and Equations      

• Atoms and Molecules, Elements and Compounds: There are about a hundred different types of atoms in the Universe. Substances made up of a single type of atom are called Elements. Some elements are made up of single atoms: Carbon(C), Helium (He), Sodium (Na), Iron (Fe) etc. He, Fe, and Na are the Chemical Symbols of the elements.

 

• Some elements are made up of groups of atoms: Oxygen (\[{{O}_{2}}\]), Ozone (\[{{O}_{3}}\]), Chlorine(\[{{C}_{13}}\]) etc. These group of atoms are called molecules.

 

• Molecules can also be made up of combinations of different types of atoms. These substances are called compounds: Common Salt (NaCl), Methane(\[C{{H}_{4}}\]), Ammonia(\[N{{H}_{3}}\]) etc. \[{{O}_{2}},\] \[C{{H}_{4}},\] \[N{{H}_{3}},\] are the Chemical Formulas of Oxygen, Methane and Ammonia respectively. CH4 means that a single molecule of methane contains one atom of Carbon and four atoms of Hydrogen. This chemical formula could have been written but the \[{{C}_{1}}{{H}_{4}}\] is never written. Similarly, a molecule of Ammonia \[(N{{H}_{3}})\] contains one atom of Nitrogen and three atoms of Hydrogen.

 

• A change in which one or more new substances are formed is called a chemical change. A chemical change is also called a chemical reaction. The change may conveniently be represented by a chemical equation.

 

• Chemical reactions occur when different atoms and molecules combine together and spit apart. For example, if Carbon (C) is burnt in Oxygen (\[{{O}_{2}}\]) to form Carbon Dioxide, a Chemical Reaction occurs. This reaction can be written: \[C+{{O}_{2}}\to C{{O}_{2}}\]. This is called a Chemical Equation. The substances on the left hand side of the equation are called the Reactants. The substances on the right hand side are called the Products.

 

• There is one very important rule with chemical equations: The number of individual atoms on each side of the equation must be the same. On the left had side, there is an atom of Carbon and a molecule of Oxygen (containing two atoms). On the right hand side there is a molecule of carbon dioxide (containing one atom of carbon and two atoms of Oxygen). The number of atoms on the left hand side is equal to the number of atoms on the right hand side. All that has changed is the arrangement of the atoms. In a chemical reaction atoms are re-arranged; no atoms are destroyed or created.

 

• Hydrogen gas is mixed with Oxygen gas. If the mixture is sparked, it explodes to form water. This chemical reaction can be expressed as: \[{{H}^{2}}+{{O}_{2}}\to {{H}_{2}}O\]. On the left had side, there is a molecule of Hydrogen (containing two atoms) and a molecule of Oxygen (also containing two atoms). On the right hand side there is a molecule of water (containing two atoms of Hydrogen and one atom of Oxygen). The left hand side has one extra atom of Oxygen. more...

Matter and Its Nature     A. Matter and its Nature

• Anything that possesses mass, occupies space, offers resistance and can be perceived through one or more of our sense is called matter.

 

• Matter is made up of particles. Particles of matter have space between them and are continuously moving and attract each other.

 

• Matter can exist in three states-

Solid

Liquid

Gas.

 

• Solid has a definite shape, distinct boundaries and fixed volumes, Solids have a tendency to maintain their shape when subjected to outside force. Solids may break under force but it is difficult to change their shape, so they are rigid.

 

• Liquids have no fixed shape but have a fixed volume. They take up the shape of the container in which they are kept. Liquids flow and change shape, so they are not rigid but can be called fluid.

 

• A gas has no definite volume or shape. Gases are highly compressible as compared to solids and liquids. The liquefied petroleum gas (LPG) cylinder that we get in our home for cooking or the oxygen supplied to hospitals in cylinders is compressed gas. Compressed nature gas (CNG) is used as fuel these days in vehicles.

 

• The forces of attraction between the particles (inter-molecular force) are maximum in solids, intermediate in liquids and minimum in solids, intermediate in liquids and minimum in gases. The spaces in between the constituent particles and kinetic energy of the particles are minimum in the case of solids, intermediate in liquids and maximum in gases.

 

• The arrangement of particles is most ordered in the case of solids, in the case of liquids layers of particles can slip and slide over each other while for gases, there is no order, particles just move about randomly.

 

• In spite of above differences all kinds of matter have a common property, the property of having a mass.

 

• The states of matter are inter-convertible. The state of matter can be changed by changing temperature or pressure.

 

• On increasing the temperature of solids, the kinetic energy of the particles increases. Due to the increase in kinetic energy, the particle start vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the particles. The particles leave their fixed positions and start moving more freely. A stage is reached when the solid melts and is converted to a liquid. The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

 

• The process of melting, that is, change of solid state into liquid state is also known as fusion.

 

• During the melting, the more...