Tool : Study

Autotrophs: Autotrophs are the green plants which synthesise their food themselves by the process of photosynthesis.

Photosynthesis: the process of preparation of own food by the Green plants with the help of chlorophyll (found in green plants), carbon dioxide and water taken from the environment in presence of sunlight is known as photosynthesis.

Plants use simple chemical substances like carbon dioxide, water and minerals for the synthesis of food.

Chlorophyll and sunlight are the essential requirements for photosynthesis.

Complex chemical substances such as carbohydrates are the products of photosynthesis.

Solar energy is stored in the form of food in the leaves with the help of chlorophyll.

Oxygen is produced during photosynthesis.

Oxygen released in photosynthesis is utilised by living organisms for their survival.

Fungi derive nutrition from dead, decaying matter.

They are saprotrophs.

Plants like Cuscuta are parasites.

They take food from the host plant.

A few plants and all animals are dependent on others for their nutrition and are called heterotrophs.

Parasitic: Organisms that live on the body of other organisms. All parasitic plants feed on other plants as either:

Partial Parasites: Obtain some of their nutrition from the host,

Example: Painted cup

Total Parasites: Dependent completely on the host for nutrition.

Example: Mistletoe.

Nutrition in plants

Saprophytic: Organisms that obtain nutrition from dead and decaying plant and animal matter.

Mushrooms, moulds and certain types of fungi and bacteria.

Insectivorous Plants: Green plants which obtain their nourishment partly from soil and atmosphere and partly from small insects.

Example: pitcher plant, bladderwort, and venus fly trap.

Symbiosis: Mode of nutrition in which two different individuals associate with each other to fulfil their requirement of food.

Lichens found on tree trunks is the association between algae and fungus.

Algae obtains water from fungus and it in turn obtains food from algae.

The main digestive glands which secrete digestive juices are:

1. the salivary glands,
2. the liver and

(iii) the pancreas.

The human digestive system consists of the alimentary canal and secretory glands.

It consists of:

1. buccal cavity,
2. oesophagus,
3. stomach,
4. small intestine,
5. large intestine ending in rectum
6. anus.

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

The stomach wall and the wall of the small intestine also secrete digestive juices.

The modes of feeding vary in different organisms.

Nutrition is a complex process involving:

1. ingestion,
2. digestion,
3. absorption,

1. assimilation and
2. egestion.

Digestion of carbohydrates, like starch, begins in the buccal cavity.

The digestion of protein starts in the stomach.

Bile secreted from the liver, the pancreatic juice from the pancreas and the digestive juice from the intestinal wall complete the digestion of all components of food in the small intestine.

The digested food is absorbed in the blood vessels from the small intestine.

The absorbed substances are transported to different parts of the body.

Water and some salts are absorbed from the undigested food in the large intestine.

The undigested and unabsorbed residues are expelled out of the body as faeces through the anus.

The grazing animals like cows, buffaloes and deer are known as ruminants.

They quickly ingest, swallow their leafy food and store it in the rumen.

Later, the food returns to the mouth and the animal chews it peacefully.

Amoeba ingests its food with the help of its false feet or pseudopodia.

The food is digested in the food vacuole.

It pushes out finger-like pseudopodia which engulf the prey.

Types of Acids:

(i) Mineral Acids: These are acids prepared from minerals present in the earth’s crust.

(ii) Organic Acids: These are acids produced by plants and animals (except hydrochloric acid).

3. Weak Acids: These do not dissociate completely in solution.
4. Examples: tartaric acid, lactic acid.
5. Strong Acids: These dissociate completely in solution. Example: nitric acid, sulphuric acid.

Neutralization: It is the reaction between an acid and a base which results in formation of salt and water.

Acid + Base ———-> Salt + Water

Example: HCl + NaOH ———-> NaCl + H₂O

Neutralisation in Everyday Life:

Indigestion: Too much acid in stomach causes indigestion. It is neutralized by taking an antacid like milk of magnesia.

Ant sting: When an ant bites, it injects formic acid into the skin. The effect is neutralized by rubbing moist baking soda (sodium hydrogen carbonate) or calamine (containing zinc carbonate).

(iii) Soil treatment: When the soil is too acidic, it is neutralized by treating with

quicklime (calcium oxide) or slaked lime (calcium hydroxide).

Bases: Bases are bitter in taste and soapy to touch.

Types of Bases:

1. Weak Bases: These naturally produce less hydroxide ions in solution. Example: magnesium hydroxide, ammonium hydroxide.
2. Strong Bases: These produce more number of hydroxide ions on dissolving in water. Example: Sodium hydroxide(NaOH), Potassium hydroxide (KOH)

Substances which are neither acidic nor basic are called neutral.

An acid and a base neutralise each other and form a salt. A salt may be acidic, basic or neutral in nature.

Solutions of substances that show different colour in acidic, basic and neutral solutions are called indicators.

Indicators: It is special chemical that changes its colour to indicate the presence of a chemical substance.

It is used to confirm the presence of an acid, a base or a neutral solution.

Classification of Indicators:

Natural Indicators:

1. Litmus: It is extracted from lichens. It is available in the form of strips of paper or in the form of a solution.· Acid turns blue litmus red. Bases turn red litmus blue.
2. Turmeric: It remains yellow in neutral and acidic solutions but turns red in alkaline solutions.
3. China rose: It turns acidic solutions to dark pink (magenta) and basic solution to green.
4. Red cabbage: It turns acidic solutions to red and basic solutions to blue.

Other Indicators:

1. Methyl Orange: It gives pinkish red colour with acidic solutions and yellow colour with bases.
2. Phenolphthalein: It is an acid-base indicator. It is colourless in acidic solutions but turns pink in alkali solutions.

Chemical Changes are changes in which the composition and chemical properties of the substance get changed.

In chemical changes new substances are produced. The most of the chemical changes are irreversible and permanent.

Note: Some chemical changes are reversible, known as reversible chemical changes.

Example: burning of a candle, formation of curd from milk, ripening of fruits.

Some Chemical Reactions in daily life:

Rusting of Iron: Rusting is the process in which iron turns into iron oxide.

It happens when iron comes into contact with water and oxygen. The process is a type of corrosion that occurs easily under natural conditions.

Prevention of Rusting:

1. By Painting
2. By Oiling and greasing
3. By Chromium plating
4. By Galvanizing
5. By Alloying

Cooking of food: Cooking causes breakdown of complex molecules of carbohydrates, fats and proteins into smaller molecules.

It is regarded as a decomposition reaction.

Cooked food is easier to digest than uncooked food.

3. Decay of Organic Substances: Microorganisms like fungi and bacteria produce enzymes which break down complex organic compounds into smaller substances.

It is also regarded as a decomposition reaction.

Some substances can be obtained in pure state from their solutions by crystallization.

In vegetative propagation new plants are produced from different vegetative parts such as leaves, stems and roots.

Flower is the reproductive part of a plant.

A flower may be unisexual with either the male or the female reproductive parts.

A bisexual flower has both the male and the female reproductive parts.

The male gametes are found inside the pollen grains and female gametes are found in the ovule.

Pollination is the process of transfer of pollen grains from the anther of one flower to the stigma of the same or another flower.

Pollination is of two types, self-pollination and cross-pollination.

In self-pollination, pollen grains are transferred from the anther to the stigma of the same flower.

In cross-pollination, pollen grains are transferred from the anther of one flower to the stigma of another flower of the same kind.

Pollination takes place in plants with the help of wind, water and insects.

The fusion of male and female gametes is called fertilization.

Fertilized egg is called zygote.

Zygote develops into an embryo.

Fruit is the mature ovary whereas ovule develops into a seed, which contains the developing embryo.

Seed dispersal is aided by wind, water and animals.

Seed dispersal helps the plants to:

1. prevent overcrowding,
2. avoid competition for sunlight, water and minerals
3. invade new habitats.

Periodic events are used for the measurement of time.

Periodic motion of a pendulum has been used to make clocks and watches.

Motion of objects can be presented in pictorial form by their distance-time graphs.

The distance-time graph for the motion of an object moving with a constant speed is a straight line.

Uniform Motion ANd Non – Uniform Motion:

1. Uniform motion: An object moving with a constant speed is said to be in uniform motion. The average speed is the same as the actual speed.
2. Non-Uniform motion: If the speed of a moving object keeps changing, the object is said to be in non-uniform motion.

Speed: It is the distance covered by an object in a unit time.

Speed = Total distance/ Total Time

Basic unit of speed is m/s.

Distance-Time Graph: Motion of objects can be presented in pictorial form by their distance-time graphs.

The distance-time graph for the motion of an object moving with a constant speed is a straight line.

It is formed by light rays that actually pass through the screen.

An image which cannot be obtained on a screen is called a virtual image.

It is formed by light rays that seem to pass through the screen.

The image formed by a plane mirror is erect.

It is virtual and is of the same size as the object.

The image is at the same distance behind the mirror as the object is in front of it.

In an image formed by a mirror, the left side of the object is seen on the right side in the image, and right side of the object appears to be on the left side in the image.

A concave mirror can form a real and inverted image.

When the object is placed very close to the mirror, the image formed is virtual, erect and magnified.

A Convex mirror is the mirror that curves out; the reflecting surface is convex.

Image formed is virtual, upright and diminished. Image formed by a convex mirror is erect, virtual and smaller in size than the object.

A Concave lens is the lens that is thinner at the center than at the edges.

It is a diverging lens.

Image formed is virtual, erect and diminished.

A convex lens can form real and inverted image.

When the object is placed very close to the lens, the image formed is virtual, erect and magnified.

When used to see objects magnified, the convex lens is called a magnifying glass.

White light is composed of seven colors.

Properties of Light:

1. Rectilinear Propagation of Light: It is the property of light by which it travels in a straight line in any direction.

The direction of path in which light make a ray.

2. Reflection of Light: It is the bouncing back of light after striking the surface of an object.

Shiny smooth surfaces reflect almost all the light.

3. Dispersion: It is the phenomenon of splitting of white light into its seven colors. White

light is mixture of: Violet, Indigo, Blue, Green, Yellow, Orange and Red (VIBGYOR) colors.

Sewage is a liquid waste which causes water and soil pollution.

Wastewater is treated in a sewage treatment plant.

Treatment plants reduce pollutants in wastewater to a level where nature can take care of it.

Where underground sewerage systems and refuse disposal systems are not available, the low cost on-site sanitation system can be adopted.

By-products of wastewater treatment are sludge and bio gas.

Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.

We should not defecate in the open. It is possible to have safe disposal of excreta by low cost methods.

Sewage Treatment:

Aeration: Air is bubbled through the wastewater while it is continuously stirred.

Filtration: Aerated water passes through a deep filter of layered sand, fine gravel and medium gravel.

Chlorination: Chlorine is added and mixed to the filtered water until water is clear.

Wastewater Treatment Plant (WWTP):

Wastewater passes through screens to remove large objects.

To go to a grit and sand removal tank at low speed.

Water is allowed to settle in large tank.

Floating solids are removed with skimmer.

Settled solids (sludge) are removed  with scraper.

Clear water is called clarified water.

Water is then decomposed by anaerobic bacteria in a tank and air is passed.

Microbes settled at bottom as activated sludge and water from top is removed.