Dps Science Sa2

8/12/2019 Dps Science Sa2

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Time And Motion

Motion: When an object changes its position with elapse of time in respect to astationary object, such as a building, electric pole, etc., the object is said to be inmotion.

Slow and Fast Motion:If an object A covers a distance in less time and another objectcovers the same distance in more time, the object A is called a faster moving object andobject B is called a slower moving object. In other words, object A has faster motion andobject B has slower motion.

Rectilinear Motion:Motion along a straight line is known as RECTILINEAR MOTION ORMOTION ALONG A STRAIGHT LINE. For example: Motion of a car along a straight line

Curvilinear Motion:Motion along a curve line is known as CURVILINEAR MOTION. Forexample: Motion of car or any moving object along a curve line

Circular Motion:Motion along a circle is known as CIRCULAR MOTION. For example:Motion of cyclist along a circular park.

Speed:Distance covered by an object in unit time is called speed.

Speed may be divided into three types: Uniform speed, Non-Uniform Speed andAverage Speed

Uniform Speed: If an object covers a fixed distance in each unit of time the motion isknown as UNIFORM MOTION or UNIFORM SPEED.

Non-uniform Speed:If an object does not cover a fixed distance in each unit of time themotion is known as NON-UNIFORM MOTION or NON-UNIFORM SPEED.

Average Speed: Total distance covered divided by total time taken is known asAVERAGE SPEED.

Speed is also known as VELOCITY.

Review Question:

Question: 1 A car covers a distance of 100 km in 5 hour, calculate its speed.


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Solution:

Given, Total distance = 100 km

Total time taken = 5 hour

We know that

Question: 2 A car covers 20 km in the first hour and cover 30 km in the last 4 hours.Find its average speed.

Solution:

Given,

Total distance covered = 20 km + 30 km = 50 km

Total time taken = 1 hour + 4 hour = 5 hour

We know that,

Periodic Motion or Oscillatory Motion: When an object repeats its motion after everyfixed interval of time, the motion of the object is called PERIODIC MOTION OROSCILLATORY MOTION.

In many wall clocks pendulum is used even today. A device having a string suspendedwith a fixed point with a bob at bottom is called pendulum.


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The motion of pendulum starting from one extreme end to another extreme end andback to the first extreme end is called one oscillation. Similarly, the motion of a simplependulum from its mean position to extreme left and extreme right and back to themean position is called one oscillation.

Time Period: Time taken to complete one oscillation by the pendulum is called timeperiod.

Review Question:

Question: 1 A pendulum takes 20 second to complete 10 oscillations, calculate itstime period.

Solution:

Given, Number of oscillations = 10

Time taken = 20 second

We know that,

Unit of Time: Time is measured in second. Thus, unit of time is second. Second isdenoted by s.

60 second = 1 minute


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60 minute = 1 hour

24 hour = 1 day

7 day = 1 week

365 days = 1 year

Unit of speed: Unit of speed is meter/second (m/s), or metre/minute (m/min) orkilometer/hour (km/h).

1000 metre (m) = 1 kilometer (km)

Speedometer: A device used to measure the speed of a vehicle is calledSPEEDOMETER.

Odometer:A device used to measure the distance covered by a vehicle.

Distance Time Graph:When distance covered by an object and time taken to cover thedistance is represented on a graph, the graph is called distance time graph.

If a vehicle cover a distance of 5 km every hour and travels for 5 hours, the timedistance time graph for the given vehicle can be plotted as follows using the table givenbelow:


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Distance time graph of a moving vehicle with a constant speed is a straight slanting line.

Speed-time graph for the same vehicle will be a straight line parallel to x-axis.

Important Points:


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Motion: When an object changes its position with elapse of time in respect to astationary object, such as a building, electric pole, etc., the object is said to be inmotion.

Slow and Fast Motion: If an object A covers more distance and object B covers lessdistance in same time, then object A is called in Fast Motion and object B is called inSlow Motion.

Rectilinear Motion: Motion along a straight line is known as RECTILINEAR MOTION ORMOTION ALONG A STRAIGHT LINE.

Curvilinear Motion: Motion along a curve line is known as CURVILINEAR MOTION.

Circular Motion: Motion along a circle is known as CIRCULAR MOTION.

Speed: Distance covered by an object in unit time is called speed. This means Speed isequal to Distance upon Time.

Uniform Speed: If an object covers a fixed distance in each unit of time the motion isknown as UNIFORM MOTION or UNIFORM SPEED.

Non-uniform Speed: If an object does not cover a fixed distance in each unit of time themotion is known as NON-UNIFORM MOTION or NON-UNIFORM SPEED.

Average Speed: Total distance covered divided by total time taken is known asAVERAGE SPEED.

Periodic Motion or Oscillatory Motion: When an object repeats its motion after everyfixed interval of time, the motion of the object is called PERIODIC MOTION OROSCILLATORY MOTION.

Oscillation: The motion of pendulum starting from one extreme end to another extremeend and back to the first extreme end is called one oscillation.

Time Period: Time taken to complete one oscillation by the pendulum is called timeperiod.

Unit of Time: Time is measured in second.

Unit of speed: Unit of speed is meter/second (m/s).

Speedometer: A device used to measure the speed of a vehicle is calledSPEEDOMETER.

Odometer: A device used to measure the distance covered by a vehicle.


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Clinical Thermometer:Clinical thermometer is used to measure the body temperature.The scale of temperature is graduated from 35C to 42C and or from 94F to 108F.The temperature of human body always remains within this range and this is the rangeon the clinical thermometer. There is a kink make near the bulb of clinical thermometerwhich prevents the automatic fall of mercury level.

Digital Thermometer: In digital thermometer, reading of temperature is displayeddigitally as in digital watches. This is safer because no mercury is used in this. It isimportant to note that mercury is a highly toxic substance.

Maximum-Minimum Thermometer: Maximum minimum thermometer is used tomeasure the daily temperature to prepare weather reports.

Reading of thermometer and measuring of temperature:

Take a clinical thermometer and hold it horizontally with reading scale towardsyour eye.

Do not hold the thermometer from the bulb. Rotate the thermometer slightly clockwise and anticlockwise. By doing this you

will see a shiny thin silvery thread. The end of the silvery thread shows the reading of temperature. If mercury lining

ends at 37, the reading is 37C. Wash the bulb end of thermometer with an antiseptic solution. Give two or three jerks slightly. By doing this the mercury level would fall. When it

falls to 35C or below, put it below the tongue and wait for one minute. Take out the thermometer and read the temperature. Temperature would be near

37C. The normal body temperature is 37C. This can differ from person to person.


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Use of Laboratory Thermometer:

Take some water in a beaker. Take a laboratory thermometer and immerse its bulb end in water; holding it

vertically. Ensure to dip whole portion of bulb end. The bulb end should not touchthe bottom or side of the beaker.

Observe the movement of rise of mercury. When it becomes stable, take thereading of the thermometer.

Repeat this with hot water and take the reading.

Difference between clinical and laboratory thermometer:

Transfer of heat:

Heat is transferred by conduction, convection and radiation.

Conduction:

Transfer of heat from one particle to the adjacent particle is known as conduction of

heat. In solids, heat is transferred by the process of conduction. In this process, thetransfer of heat takes place through adjacent molecules.

Example:When one end of an iron rod is put over flame then part which is nearer to theflame is heated first and heat is gradually transferred to the other end of the rod. Thishappens because particles of iron rod which are nearer to the flame receive the heatand transfers this to the adjacent particles. Subsequently, the adjacent particles transferthe heat to the next adjacent particles. This process continues and heat reaches to theother end of the rod. Thus, heat transfer in solid takes place through conduction.


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rise to the phenomenon which is called the sea breeze. Because of this, people living incoastal areas prefer to live in a sea facing house.

Land Breeze: In coastal areas, the breeze which moves from land towards the sea iscalled land breeze. In the night, the land cools down more quickly than the oceansurface. This makes the air over the water surface warmer than air over the landsurface. Warmer air over the water surface rises in the air and air from the land rushestowards the water surface to fill the gap. This phenomenon continues which creates aflow of air from land to the sea. This phenomenon is called land breeze.

Radiation:

All hot bodies emit heat by the process of radiation. Radiation of heat does not require amedium. Sunlight comes to the earth because of radiation as there is no medium

present between the atmosphere of the earth and the sun.

One can feel the heat of bonfire by standing around it. We get warmth from the roomheater because of radiation.

Reflection and absorption of heat:When heat falls over an object some of the heat isabsorbed by the body and some of the heat is reflected. The temperature of an objectincreases because of absorption of heat.

In conventional room heater you can see the reflector attached with it. The reflector ofthe room heater reflects the heat towards the person sitting or standing near the room

heater.

Reflection is the cause that umbrella is used to protect from heat of the sun in summer.Dark color absorbs more heat while light color reflects most of the heat. Thats whywearing light colored clothes is preferred in summer, dark colored clothes are preferredin winter.

Dark clothes absorb more heat and keep one comfortable in winter. On the other hand,light clothes reflect most of the heat and keep one comfortable in summer.


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Now-a-days many kitchen utensils come in black color, since utensils of black colorabsorb more heat and thus cooking becomes faster.

Woolen Cloth:Woolen clothes are used in winter season. Wool is a poor conductor ofheat. In addition to it; air gets trapped in woolen fiber to further increase the poorconductivity of wool. This prevents the radiation of heat of our body to the surroundingand prevents the cold from surrounding to affect our body. Thus, wearing woolen clothmakes one comfortable in winter season.

Important Terms:

Temperature:The reliable measure of hotness or coldness of anything. Thermometer:A device to measure the temperature. Degree Celsius:Unit of measurement of temperature. Clinical Thermometer:A device to measure the temperature of human body. Laboratory Thermometer:Used to measure the temperature in laboratory. Maximum-Minimum Thermometer:Use to measure the temperature of climate. Conduction:Mode of transfer of heat in solids. Convection:Mode of transfer of heat in liquids and air. Radiation:Mode of transfer of heat without medium. Conductor:Materials that allow the flow of heat through them. Insulator:Materials that do not allow the flow of heat through them. Land breeze: Breeze that flows from land surface to sea surface in summer

nights. Sea breeze: Breeze that flows from sea surface to water surface in summer

days.

Acid, Base and Salt

Acid Base Salt Indicator Neutralization or Neutralization Reaction Use of neutralization

Substances can be divided into three types Acid, Base and Salt.

ACID: Taste of acid is sour. There are many substances that contain acid and so tastesour. For example lemon, curd, pickles, orange juice, vinegar, etc.

Substances that taste sour are called acidic. The chemical nature of such substance isknown as ACIDIC.

The word acid comes from Latin ACERE which means sour.


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Acid Rain: Carbon dioxide, sulphur dioxide and nitrogen dioxide which are releasedfrom vehicles and chimneys mix with droplets of rain and turn the rain water acidic.When this acidic rain water falls over earth, it is known as acid rain. Acid rain damagesthe buildings and is harmful for plants and animals.

Taj Mahal; which is made of marble is in threat because of acid rain. Many parts of TajMahal and other many historical buildings and monuments have got damaged due toacid rain.

Characteristics of Acid:

Sour in taste. Turns blue litmus paper red. Turns the solution of China rose to dark pink colour (magenta).

Characteristics of Base:

Bitter in taste. Turns red litmus paper blue. Turns solution of China rose to green. Turns turmeric paper to red.

Neutralisation:

When solution of acid is mixed with the solution of base, both of them neutralize eachother and a third substance; called salt; is formed. Such phenomenon is calledneutralization or neutralization reaction. The solution formed because of mixing ofsolution of acid and base is neither acidic nor basic in nature. Such solution is known asneutral solution.

Salt formed because of neutralization reaction may be acidic or basic in nature. Acidicor Basic nature of salt depends upon the strength of acid and base. In neutralizationreaction heat is evolved. Reactions in which heat is evolved are known as exothermicreactions. Thus, neutralization reaction is an exothermic reaction.

Sodium hydroxide is a base and hydrochloric acid is an acid. When solution of sodium

hydroxide is mixed with the solution of hydrochloric acid, both neutralize each other andcommon salt (Sodium chloride) is formed. Since, it is an exothermic reaction, soreaction mixture becomes slightly hot. The reaction involved in this can be written asfollows:

Sodium chloride is the chemical name of common salt which is used in household.


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Neutralization Reaction in Everyday Life:

There are many uses of neutralization reaction in everyday life.

Indigestion: Our stomach releases hydrochloric acid to kill bacteria; if any; present infood. Hydrochloric acid released in our stomach also helps in the digestion of food.Sometime our stomach produces more hydrochloric acid than required. Production ofmore hydrochloric acid in the stomach manifests as indigestion. This condition can bepainful and causes pain in the stomach.

To get rid of such symptoms, a medicine made of milk of magnesia (a base) is takenorally. Milk of magnesia, being a base neutralizes the hydrochloric acid and gives relieffrom pain because of indigestion.

Ant sting: Ant sting or bee sting contains methanoic acid. Methanoic acid is also knownas formic acid. Bee or ant injects formic acid into our skin, while biting. Injection of acidby ant or bee results in pain at the place of bite.

Rubbing baking soda over the skin gives relief from pain due to ant or bee sting. Bakingsoda, which is a base, neutralizes the effect of acid injected by bee or ant. Anotherbase, such as zinc carbonate (Calamite solution) is also used in the case of ant or beesting.

Soil Treatment: Sometimes soil becomes acidic or basic due to excess use of fertilizersor wrong method of harvesting. Acidic or basic nature of soil affects the yield as plants

do not grow properly on such soil.

Acidic soil is treated with slaked lime or quick lime. Slaked lime (Calcium hydroxide) andquick lime (Calcium oxide) are bases. Use of slaked lime or quick lime neutralizes theacidic nature of soil.

Basic soil is treated with organic matter. Organic matter releases acid and neutralizesthe basic nature of soil.

Factory Waste: Wastes of most of the factories are acidic. If such acidic wastes areflushed into rivers, acid present in them kills the aquatic organisms and pollutes the

water. Thus, factory wastes are treated with basic substances to neutralize the acidpresent in them before being flushed in the river.

Important Points:

Acid is sour in taste. Acid turns blue litmus paper to red. Acid turns China rose solution to dark pink. Base is bitter in taste. Base turns red litmus paper to blue.


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Base turns turmeric paper or solution to red. Base turns China rose solution into green. Indicator is a special substance which shows the acidic or basic character of a

substance by change in colour. Litmus, turmeric and solution of China rose are natural indicators. Litmus is obtained from lichens. Solutions of acid and base neutralize each other when mixed in proper ratio. This

is called neutralization or neutralization reaction. In neutralization reaction between the solutions of acid and base, a new

substance called salt is formed. Salt formed because of neutralization reaction may be acidic or basic in nature.

The acidic or basic nature of salt depends upon the strength of acid and baseused for neutralization reaction.

Wastewater Wastewater: The water which gets contaminated after various works; like

washing, bathing, mopping, etc. is called wastewater. World Water Day: 22nd March International Decade for Action on Water for Life:2005 2015: It was declared

by the General Assembly of the United Nations. Its main goal was to reduce thenumber of people who do not have access to safe drinking water; by half.

Sewage Treatment:The process of removing impurities from waste water beforeit can be reused or sent to the water bodies is called sewage treatment orcleaning of water.

Sewage:The liquid waste which has water as its largest component; along withvarious types of impurities; is called sewage.

Sewers:The pipes which carry wastewater. Sewerage:The network of sewers. Manhole: These are the holes made in sewers at frequent intervals, so that

timely inspections and cleaning of sewers can be done through them. Themanhole is covered with a hard lid so that people and traffic can easily moveover it.

Review Questions: 1. What is sewer? Answer: The pipe which carries the wastewater is called sewer. 2. What is sewerage? Answer: The network of sewers is called sewerage. Wastewater Treatment Plant or Sewage Treatment Plant:


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These are large plants where wastewater is cleaned before being sent to thenearest water bodies or being reused. The sewage treatment involves physical,chemical and biological processes to remove impurities from the wastewater.

Physical Process: 1. Filtration: The wastewater is passed through bar screen. Large objects; like

rags, sticks, plastic bags, cans, etc. are removed in this process. 2. Grit and Sand Removal: The wastewater is slowly passed through the

sedimentation tank. Grit, sand and pebbles settle down at the bottom. 3. Sedimentation: Water is then sent to the sedimentation tank. Solids; like

faeces settle at the bottom. Floatable impurities; like oil and grease float on thesurface. A scraper removes the faeces from the water. The impurity thuscollected is called sludge; which is sent to the sludge tank. The sludge can beused to produce biogas or to produce manure. A skimmer removes the floatableimpurities. Now, the water is called clarified water.

Biological Process 4. Aeration: Air is pumped into clarified water so that bacteria can proliferate.

Bacteria consume the human waste. It leaves food waste, soap and otherunwanted materials in the water. The microbes settle down at the bottom afterseveral hours. Water is then removed from the top. This water is fit for irrigationand can be used for that purpose.

Chemical Process 5. Chlorination:Water purified through aeration is not fit for human consumption.

It needs to be treated with chlorine. For this, bleaching powder is added to thewater. The chlorine kills whatever germs may be left in the water. Afterchlorination, the water is fit for drinking.

Review Questions 1. Which process during the wastewater treatment results in proliferation of

bacteria? Answer: Aeration 2. Which process during the wastewater treatment kills the germs? Answer: Chlorination Better Housekeeping Practices to Maintain Sanitation: Do not throw cooking oil and fat in the drain. This can block the drain. The fat and

oil clogs the pores in the soil; in open drains. This reduces the filtering capacity ofsoil.

Do not throw chemicals; like paint, insecticides, medicines, etc. into the drain.

They kill the bacteria which otherwise help in cleaning the water. Do not throw used tea leaves, solid food, soft toys or napkins in the drain. They

can clog the drain and do not allow oxygen to enter the sewage water. Oxygen isimportant for the natural process of decomposition.

Sanitation and Disease Maintaining overall cleanliness in the home and in surroundings is called

sanitation. Sanitation is important for the health of a person and that of thecommunity.

Many people have the habit of defecating in the open. Uncovered human excretaattract flies and other insects. These insects carry the germs of many dangerous


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diseases; like cholera, typhoid and jaundice. With constant public awarenesscampaign, the practice of open defecation can be stopped.

Poor sanitary condition also contaminated the groundwater becausecontaminants percolate down the ground.

Stagnant water is a perfect breeding ground for mosquitoes. Mosquitoes are thecarriers of several diseases; like malaria, dengue, chikungunya and filaria.

Alternative Arrangements for Sewage Disposal In the absence of a sewerage system, arrangements for onsite sewage disposal

can be made. For example; septic tanks are built in which human excreta arecollected. In due course of time, the human excreta get decomposed intocompost.

Composting pits can be made to dump waste and to make manure from them.Sewage can be collected into biogas plants to produce useful biogas.

Chemical toilets are new discoveries. They do not require much water for the

disposal of human excreta and are environment friendly. Such toilets are ideal forthe trains.

Sanitation at Public Places Maintaining sanitation at public places is also important. In a heavily populated

country; like India; any public place is always teeming with people. More footfallat public places results in more filth. Sanitation workers often work continuouslyto maintain cleanliness at public places. But it is our responsibility also tomaintain sanitation at public places. We should follow some simple rules to helpthe sanitation workers. For example; always throw the trash in a dustbin andavoid littering. Dont spit at public places and use the dustbin or special binsmarked for the purpose.

Weather, Climate and Adaptation of Animals to Climate

Weather:The day to day condition of atmosphere at a particular place is called weather.The weather can be comfortable, or can be too hot or cold.

Weather Report:The daily report about weather; usually released by the meteorologicaldepartment is called weather report. Weather report is often shown along with the newson television.

Elements of weather: The various elements of weather are: temperature, humidity,rainfall, wind-speed, etc.

Temperature:Temperature depends upon the duration of sunshine. During the summerseason, the duration of the sunshine is longer. Due to this, the temperature is high insummer. The day temperature is minimum in the morning and maximum at noon.

Humidity: Humidity is the amount of moisture present in air. Humidity is generallymeasured in percentage. Humidity is generally at the highest level; during the rainyseason.


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Rainfall:Amount of rainfall is measured in terms of mm. For this, an apparatus; calledrain gauge is used.

Wind-speed:Speed of wind also affects the condition of weather.

Department of Meteorology: This is a Government Department. The MeteorologicalDepartment measures the elements of weather and keeps their record. Meteorologistsuse data from satellites and analyse the data to forecast about the weather.

Climate: Climate is the average weather condition of at least 25 years; in a givengeographical part.

The climate of India is said to be hot and humid, because the temperature is usuallyhigh and so is the humidity for most parts of the year. The climate of Rajasthan is saidto be hot and dry because temperature is very high but humidity is very low. On theother hand, the climate of Kashmir is said to be cold because temperature is low.

Rainforest: Rainforest is found generally near the equator. Places near the equatorreceive more sunshine and hence more rainfall. This makes the place hot and humid.Temperatures vary from 15C to 40C generally near the equator. Rainforests are alsopresent in some tropical areas.

Desert:Temperature in desert is generally higher and it receives less or little rain fall.So deserts are hot and dry.

Polar Region: Polar Region is at high latitude and hence do not receive adequatesunshine. Due to this, temperature is very low in the Polar Regions. The Polar Region iscovered with snow, because of the low temperature.

Climate and Adaptation:

At several places, such as desert, polar region, etc. climate is very harsh. Manyorganisms live and thrive at these places, in spite of the harsh climate. Animals andplants; living in such places; develop certain features which help them survive the harshclimate. To develop certain features in order to survive the given climate is calledadaptation.

Adaptation in Polar Region:

In Polar Regions, the sun does not set for about six months and it does not appear foranother six months of the year. These regions are covered with snow for most part ofthe years. In winter, temperature may down to -37C. Hence, the climate of PolarRegions becomes extreme and harsh. In spite of such condition, many animals live atthose places, for example: Polar Bear, Penguin, Snow Leopard, etc. These animalsshow various adaptations which help them in surviving in the harsh climate of the PolarRegion.


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Polar Bear:Polar bear has two thick layers of fur over its body. In addition to this, theyhave thick layer of fat under the skin; called blubber. These layers act as insulator andprevent the bear from extreme cold. Because of the white fur, the Polar Bear can easilymix with its snowy background and can hide from its prey and predator. Getting hidewith surrounding because of special colour and pattern is known as camouflage.

Polar bears have wide paws with long curved nails, called claws. This helps them tomove on the snow. r swimming to keep them cool. Wide paws work as a rudder, whileswimming. They are very good swimmers.

Polar bear has a highly developed sense of smell. It helps the Polar bear in finding afish even from under a thick layer of snow.

These adaptations help Polar RThese adaptations help Polar Region to survive in theextreme condition of the Polar Region.


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Penguin:Penguins also live in the Polar Region. Penguins are of white colour with blackback. They have thick layer of fat under their skin. This protects them from extremecold.

They usually remain huddled together. This helps in keeping them warm. nd curvedclaws which help them to walk in snow and to swim in water.

These adaptations help the penguin to survive in the extreme condition of the PolarRegion.

Birds: There are many types of birds found in Polar Regions. They fly to the warmregions during winter to survive. Long distance travel; in search of favourable climate; iscalled migration.

Some migratory birds are known to travel as long as 15000 km to keep them survive inopposite climatic conditions. Arctic tern is known to be the longest traveler among themigratory birds.

Apart from birds, many fish and mammals also migrate to other places in such oppositeclimatic conditions.

Tropical Rain Forest:

In India, Tropical Rainforests are found in the Western Ghats and in Assam. Rainforestsare also found in Southeast Asia, Central America and Central Africa.

Rainforests have plenty of food which supports variety of life. Many animals are found inthe rainforests, e.g. leopard, elephant, snakes, tigers, monkey, buffaloes, frogs, apes,lizards, many types of birds, insects, etc.

In spite of plenty of food, there is a high level of competition for survival among animalsin the rainforest.

Adaptive features of animals found in rain forest:

Lion: The colour of lion helps it in blending in its background. Lion has a highlydeveloped sense of smell and night vision. All of these help a lion in catching the prey.

Elephant:Elephants have well developed sense of smell. It helps the elephant in findingthe food. The trunk has powerful muscles which help the elephant in uprooting even abig tree. Elephants have good sense of hearing which help the elephant in sensingdanger way in advance. An elephant uses its trunk to sprinkle water all over its body sothat it can cool down its body temperature.

Monkeys:Monkeys are highly adapted to live in the rainforests. Monkey uses its palmsand soles to grip a branch and thus can hang and swing from a branch. It can also use


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its tail to hold a branch. Monkeys can climb to the topmost branch of a tree and thus cansee very far in the jungle. This helps them in sensing the danger and also in finding thefood.

Frogs:Frogs are adapted to live both on land and in water. The greenish colour of thefrog helps it in mixing with the green foliage. Frog has a long and sticky tongue withwhich it catches its prey. The tree-frog has developed sticky pads in its claws. Thishelps the tree-frog in climbing a tree and in holding on to a branch.

Important Points:

Weather: Day to day atmospheric condition. Climate: Average atmospheric condition for at least 25 years. Elements of weather: Temperature, Humidity, Rainfall, Wind-speed, etc. Rainforest: Dense forest near equator and tropical regions. Desert: A region with little rainfall, high temperature and full of sand. Polar Regions: Regions near poles, having very low temperature, area is covered

with snow most of the parts of year. Adaptation: Special habits of animals which enable them to survive in particular

climatic conditions. Camouflage: Special colour of animals because of which they can resemble with

background of surrounding which hide themselves from predators.

Soil

Soil Mixture of rocks particles, sand and humus is known as soil. Soil supports the

growth of plants by holding their roots and supplying water to them.

Formation of soil Soil is formed by weathering. Weathering is the process of breaking

down of rocks by the action of wind, water and climate. Formation of even one inch of

soil takes many years.

Composition of Soil:Soil contains humus, water, clay, sand and gravel.

Humus:The decaying dead matters in soil are called humus. Humus makes the soil fertile

and provides nutrients to the plants.

Soil Profile:Different vertical layers of soil are known as soil profile. The feel (texture),

colour and chemical compositions of soil are different in each layer.


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Properties of Soil:

Percolation Rate of Water:Amount of water drained through water in unit time is known

as percolation rate of water in soil. Percolation rate of water can be calculated using the

formula given here.

The percolation rate of water in sandy soil is fastest and in clayey soil is slowest.

Moisture present in soil: Amount of water present in soil is called moisture present in

soil. The amount of moisture present in clayey soil is highest and that in sandy soil is

lowest.

Absorption of water:Different soil absorbs different amount of water. Clayey soil

absorbs the highest amount of water because of its higher water retention capacity. On

the other hand, sandy soil absorbs the least amount of water because of its lower water

retention capacity. Soil and Crop:Different types of soil are found are found at different places. A particular

soil type may not be suitable for certain types of crop. Thats why different types of crop

are grown in different parts of the world.

Sandy soil:Sandy soil is not fit for any crop as it does not retain water. However, some

thorns and bushes do grow on sandy soil. Millets can be grown on sandy soil.

Clayey Soil:Clayey soil is best suited for paddy, as it can retain water for a longer time.

This is also suitable for wheat and grams.

Loamy Soil:Loamy soil is considered the best for almost all types of crops. It is suitable

for lentils and other pulses.

Sandy Loam:Sandy loam soil is suitable for the growth of cotton plants as it can easily

drain water and is well aerated. Soil Erosion:Removal of topsoil by weathering agents; such as wind, water and ice is

known as soil erosion. Soil erosion affects the fertility of soil, as humus present in the soil

is eroded along with soil. It is important to prevent the soil erosion.

Preventive measures for soil erosion:

Deforestation should be prevented at all cost to prevent soil erosion.

Shelter belt plantation of trees is good for preventing soil erosion.

Terrace farming in hilly areas is effective in preventing soil erosion.

Transportation in Animals and Plants

Transportation in Unicellular Organisms: In unicellular organisms, transportation ofsubstances happens through diffusion and osmosis. Gases move in and out of the cellby diffusion. Other substances move by osmosis.

DIFFUSION:Random motion of particles in order to attain equilibrium of concentrationis called diffusion. Diffusion can be observed in many aspects of day to day life. Thearoma of food comes from the kitchen because of diffusion. A pleasant smell of flowerscomes because of diffusion. Bad odour of garbage comes because of diffusion.

OSMOSIS:Movement of water through a semi-permeable membrane from high waterconcentration to low water concentration is called osmosis. Osmosis is a type of


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diffusion. Cell membrane is a semi-permeable membrane. Substances move across thecell membrane because of osmosis. Seeds swell up; when soaked in water; because ofosmosis.

Review Questions

1. What is diffusion?Answer: Random movement of particles in order to attain equilibrium ofconcentration is called diffusion.

2. What is osmosis?Answer: Movement of water through semi-permeable membrane from high waterconcentration to low water concentration is called osmosis.

CIRCULATORY SYSTEM IN HUMANS

Diffusion and osmosis can result in transportation of substances to short distances only.For bigger and complex organisms, there is a need of a more complex system fortransportation of substances.

The circulatory system in humans is composed of three main components, viz. heart,blood vessels and blood.

BLOOD

Blood is a type of tissue which is responsible for transportation of substances. Bloodworks as the carrier of various substances. Following are the main components ofblood.

Blood Cells, Platelets and Plasma

PLASMA:Plasma makes the liquid part of the blood. It makes the largest part of theblood. Plasma is pale in colour.

BLOOD CELLS:There are two main kinds of blood cells in the human blood, viz. RedBlood Cells and White Blood Cells.

a. Red Blood Cells or Red Blood Corpuscles (RBC): These are in the shape ofdiscs. They contain a pigment; called haemoglobin. Haemobglobin binds withoxygen and thus is mainly responsible for transportation of oxygen in the body.Haemoglobin also transports some amount of carbon dioxide.

b. White Blood Cells or White Blood Corpuscles (WBC): These are present invarious shapes. WBCs engulf foreign particles and harmful microbes. Thus,WBCs help in fighting the diseases. WBCs make the immune system of thebody.


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PLATELETS:Platelets are responsible for clotting or coagulation of blood. In case of aninjury, the blood clots after some time. This prevents excess loss of blood. Clotting ofblood is a defense mechanism in the body.

BLOOD VESSELS:

Blood vessels are of three main types, viz. arteries, veins and capillaries.

ARTERIES:Arteries are made of thicker walls. Arteries carry oxygenated blood from theheart to different organs. Pulmonary artery is an exception, because it carriesdeoxygenated blood from the heart to the lungs.

VEINS:Veins are made of thinner walls. Veins carry deoxygenated blood from differentorgans to the heart. Pulmonary vein is an exception, because it carries oxygenatedblood from the lungs to the heart.

CAPILLARIES:These fine branches of arteries and veins.

Review Questions

1. What is blood?Answer: Blood is a type of tissue which is responsible for transportation ofsubstances.

2. What is the role of RBCs?

Answer: Transportation of oxygen.

HEART

:


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The heart is a small muscular organ which is responsible for pumping the blood. Thehuman heart has four chambers, viz. the right auricle, the right ventricle, the left auricleand the left ventricle. The upper chambers are called auricle or atrium. The lowerchambers are called ventricle. The following flow chart shows the movement of bloodthrough the heart (the blue colour shows deoxygenated blood and the red colour showsoxygenated blood):

From the body Right Auricle Right Ventricle Pulmonary Artery Lungs Pulmonary VeinLeft AuricleLeft VentricleTo the body

HEART BEAT:While pumping the blood, different chambers of the heart contract andrelax in turns. The contraction and relaxation of different chambers produces athumping sound. This sound can be heard as heart beat. One heart beat indicates onecycle of pumping action by all the four chambers. The heart of a normal human beats

for 72 times in a minute. The heart pumps about 70 mL blood in one beat. This meansthat heart pumps a whopping 5 liter blood in a minute.

PULSE:A certain locations in the body, a pulse; similar to heart beat; can be felt. Thishappens because of blood rushing in with every heart beat. The pulse rate is same asthe heart rate. Pulse can be felt near the wrist, neck, ankle, etc.

STETHOSCOPE:This is a device which is used by doctors to listen to the heart beatand pulse. Stethoscope is composed of a long rubber tube, two ear pieces and adiaphragm.

Review Questions

1. Which organ in the human body is responsible for pumping of blood?Answer: heart

2. Which type of blood is carried by arteries?Answer: Oxygenated Blood

EXCRETION

Various activities always go on inside the body of a living being. These activities are

collectively called metabolism. Many harmful substances are created during metabolicactivities. These substances can prove lethal if not removed from the body in time.Removal of waste from the body is called excretion.

Excretory System


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The human excretory system is composed of a pair of kidneys, two tubes; called ureterand a urinary bladder.

KIDNEY: Kidneys are bean-shaped. They work like filters. Blood; laden with wastematerials enters the kidney. The waste is filtered from the blood and the purified blood issent to the normal circulation. The waste; along with water; is transferred to the urinarybladder through the ureters. The content of the ureter is called urine. Urine contains95% water, 2.5% urea and 2.5% other wastes. Urine is expelled out from time to time.

Type of waste and mode of excretion: Protein is made up of nitrogen. Metabolism ofprotein creates nitrogenous wastes in the body. The nitrogenous waste is the mainwaste in animals. The nitrogenous waste takes different forms in different animals.These are; ammonia, urea and uric acid. Based on the type of nitrogenous waste,animals can be divided into following categories:

AMMONOTELIC: Ammonia is the main nitrogenous waste in these animals. Lot of

water is required for removal of ammonia. Ammonotelism is present in aquatic animals,e.g. fish, frogs, etc.

UREOTELISM: Urea is the main nitrogenous waste in these animals. Less water isrequired for removal of urea. Ureotelism is present in mammals.

URECOTELISM:Uric acid is the main nitrogenous waste in these animals. Removal ofuric acid requires negligible amount of water. Urecotelism is present in reptiles andaves.


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Note: Some of the wastes are removed along with sweat. Carbon dioxide is animportant waste which is removed through the lungs.

Review Questions

1. Which is the main excretory organ in humans?Answer: Kidneys

2. Which is the main excretory product in humans?Answer: Urea

TRANSPORTATION IN PLANTS:

For transportation in plants, there are two main tissues, viz. xylem and phloem. These

are composed of narrow tube-like structures. Xylem is responsible for transport ofwater, while phloem is responsible for transport of food.

Transport of Water: Plants take water from soil. Following are the main steps intransport of water in plants.

In Roots:From soil, the water enters the root hairs because of osmosis. From root hairswater enters further because of root pressure.

IN STEM: Various factors are at play during transportation of water through xylem instems. The transport of water through xylem is also called Ascent of Sap.

a. Root pressure is responsible for the rise of water to some height.


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b. Capillary action pushes the water further up. The rise of liquid in a very narrowtube is called capillary action. Capillary action happens because of very smalldiameter of the tube.

c. Adhesion Cohesion: Water molecules stick to each other and make a continuouscolumn inside the xylem tubes.

d. Transpiration pull: There are numerous small pores on the surface of leaves.These pores are called stomata. Water vapour is continuously removed throughstomata during daytime. Removal of water vapour in plants is calledtranspiration. This creates a pull in the underlying xylem tissues. The pull iscalled transpiration pull. Transpiration pull creates a suction effect on the watercolumn inside the xylem.

TRANSPORT OF FOOD: Food is prepared in leaves and needs to be transported todifferent plant parts for use and for storage. The transport of food takes place throughphloem. Some biological force is used in transport of food in plants.

Review Questions

1. Transport of water and minerals in plants happens through which tissues?Answer: Xylem

2. Transport of food in plants happens through which tissues?Answer: Phloem

3. Reproduction In Plants4. Reproduction: The process by which a living being produces its offspring is called

reproduction.5. Types of Reproduction:6. 1 - Asexual Reproduction:When a single parent is involved in the process, it is

called asexual reproduction. Following means of asexual reproduction are usedby plants:

7. (a) Budding: This method is used by unicellular plants; like yeast. Yeast is afungus and fungi are also known as non-green plants. The yeast cell produces abud which gets its own nucleus. The bud develops to certain size and detachesfrom the mother cell to produce the new yeast.

8.9. (b)Fragmentation: In some simple plants, the plant body is divided into smaller

fragments. Each fragment then develops into a new plant. Example: Spirogyra.


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10.11. (c) Spore Formation:Special spore-bearing organs are present in some plants;

especially in fungi and algae. These are called sporangiophores. Thesporangiophore bears spores. The spores germinate to develop a new plant.

12.13. (d) Vegetative Propagation:When a new plant is developed by a vegetative part;

such as root, stem or leaf; it is known as vegetative propagation. For example:when the tuber of potato is cut into several pieces and each piece bears an eye;each piece produces a new plant. The stems of moneyplant, rose, mango, etc.can produce new plants when they are inserted in soil. The leaf of bryophyllumproduces new plants through its notches.

14. Review Questions:15. (A) Give an example of an organism which reproduces by budding.16. Answer: Yeast17. (B)How many parents are involved in asexual reproduction?18. Answer: Only one19.2 - Sexual Reproduction: When two parents are involved in the process, it is

called sexual reproduction. Two gametes, viz. male and female gametes, areformed. The fusion of male and female gametes is called fertilization. Zygote isformed after fertilization. The zygote develops into an embryo and finally into anew individual.


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20.21.Flower:Flower is a special organ of flowering plants (angiosperms) which works

as the reproductive system. A flower is composed of four distinct whorls.22. (1) The outermost whorl is called calyx. It is composed of green leaf-like

structures; called sepals.23. (2) The second whorl is called corolla. It is composed of colourful structures;

called petals. Petals are colourful so that insects and other animals can beattracted towards them. This is necessary for pollination.

24. (3) Androecium:The third whorl is called androecium. It is composed of stamens.Stamen has two main parts. The tube-like portion is called filament. The capsulelike structure at the top is called anther. The anther produces pollen grains; whichare the male gametes.

25. (4) Gynoecium: The whorl at the center is called gynoecium. It has a swollen

base; called ovary and a tube-like structure; called style. The top of the tube issomewhat flattened and is called stigma. Ovary produces the eggs or femalegametes.

26. Review Questions27. A -What is the benefit of colourful petals for plants?28. Answer: Colourful petals attract insects, birds and other animals. It helps in cross

pollination.29. B - What is the name of the male gamete in a flowering plant?30. Answer: Pollen grain31.Pollination: The transfer of pollen grains from anthers to stigma is called

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

32.Self Pollination:When anthers of the same flower are transferred to the stigma; itis called self pollination.33.Cross Pollination: When anthers from a different flower are transferred to the

stigma; it is called cross pollination. The flowers can be on the same plant or ondifferent plants. Cross pollination is the norm in most of the plants. Plants needhelp from various agents of pollination to carry out cross pollination. Wind,insects, birds and other animals play the role of agent of pollination.


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34.35.Fertilization: The fusion of the male gamete and the female gamete is called

fertilization. When pollen settles on top of the stigma, it germinates to produce apollen tube. The pollen tube enters the ovary through the style. Male nuclei aretransferred to the ovary, through the pollen tube. The cell formed, just afterfertilization, is called zygote. Zygote develops into embryo. Each embryodevelops into a seed. The seed is an embryo which is enclosed in a protectivecoat. The ovary gets transformed into fruit.

36.Dispersal of Seeds:If all the seeds were to germinate near the mother plant, thenew plants shall not get adequate resources; like sunlight, air and nutrients. Forproper growth of the new plants, it is necessary that they develop away from themother plant. For this, it is necessary that seeds are spread far and wide. The

process of spreading seeds to different places is called dispersal of seeds. Manyagents of seed dispersal assist the plants in this process.

37.Dispersal by Wind:Seeds of some plants are light-weight and some hair-like orwing-like structures are present on them. Such seeds float on air and are thusdispersed by wind. Example: Dandelion, maple, drumstick, etc.

38.Dispersal by Water:Dispersal by water takes place in some aquatic plants and insome which grow near a water body. Seeds of water lily float and thus dispersedby water. The coconut seed has a tough fibrous covering which has plenty of airinside. This helps the coconut seeds in floating on water.

39.Dispersal by Animals:Some seeds have spine like structures on them. They getstuck to the fur of animals and thus get spread to different places. Examples;

Beggar tick, Xanthium, Urena, etc. Some seeds are swallowed by birds andanimals along with fruits. These seeds get dispersed with bird or animaldroppings.

40.Dispersal by Bursting: Some fruits burst open when they mature. The force ofbursting is enough to spread the seeds. Examples; Ladyfinger, castor, balsam,etc.

41.Dispersal by Humans:Human beings also help in dispersal of seeds, especiallyduring farming.

42. Review Questions:43. 1- What is pollination?44. Answer: Transfer of pollen grains from anther to stigma is called pollination.


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45. 2 - Give two examples of seeds which are dispersed by wind.46. Answer: Dandelion, maple

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