General Science 8th Class Chapter 4 Biotechnology Solved Exercise

General Science

8th Class

Chapter 4

Biotechnology

Questions

1. Encircle the correct option.

(i) The additional circular pieces of DNA present in a bacterial cell are called:

a. RNA        b. nucleotides        c. chromatids        d. plasmids

(ii) What may be the objective of genetic modifications of plants?

a. Production of disease resistant plants

b. Improvement in nutritional quality of plants

c. Production of herbicide resistant plants

d. All of these

(iii) Plasmid and attached foreign gene with it are collectively called:

a. recombinant cell        b. recombinant DNA

c. recombinant plasmid        d. recombinant chromosome

(iv) The organisms whose cells and plasmids are usually used in genetic engineering are:

a. bacteria        b. fungi        c. algae        d. viruses

(v) Sections of DNA serving as codes for developing characters in an organism are called:

a. genes        b. nucleotides        c. plasmids        d. proteins

(vi) Which of the following is not a biotechnology product?

a. Insulin        b. Quinine        c. Beta-endorphin        d. Interferon

(vii) How do genetic engineers get insulin for diabetic patients?

a. Isolate from human pancreas

b. Isolate from pancreas of other animals

c. Insulin gene inserted in human pancreas

d. Insulin gene inserted in bacteria

(viii) Why do genetic engineers use bacteria in genetic engineering?

a. The chromosome of bacteria is made of DNA and proteins

b. Their nucleus is very big and easy to handle

c. They have many chromosomes

d. Bacteria divide very fast and make colonies

(ix) A gene is inserted into a bacterium by:

a. tissue culture        b. fermentation        c. biodegradation        d. genetic engineering

2 Write short answers.

(i) What is biotechnology?

Ans.

Biotechnology:

Biotechnology is the use of living cells and organisms in the products and processes that can improve the quality of life.

(ii) Name at least two life saving products of biotechnology.

Ans.

Two important life saving biotechnology products include insulin and vaccines.

(iii) Write the application of biotechnology in

(a) agriculture        (b) health        (c) food production

Ans.

(a) agriculture

Biotechnology has played a revolutionary role in improving our agriculture and production of high yields of crops. Using biotechnology scientists insert weed resistance and pest resistance genes into the plants. Such genetically modified plants prepare proteins which are harmful for weeds and pest / insects. The major crops that have been modified are maize (corn), wheat, rice, canola, potato, soybean, cotton, etc.

(b) health

Biotechnology techniques are used for curing diseases and improving health. The diseases for which previously no adequate treatment was available can now be treated using biotechnology techniques. Identification of root causes of diseases, production of medicines for fighting against diseases and curing and correction of genetic defects, etc., are the major roles of this technology in developing better health.

(c) food production

Use of better quality genes in the animals is producing high yields of milk and meat. Production of better quality fruits and vegetables and increasing their shelf lives are also due to using biotechnology logical techniques.

General Science 8th Class Chapter 3 Variations, Heredity and Cell Division Solved Exercise

General Science

8th Class

Chapter 3

Variations, Heredity and Cell Division

Questions

1. Encircle the correct option.

(i) Which of these is NOT a genetic variation?

a. Mark of a cut on skin        b. Eye colour        c. Attached earlobes        d. Blood group

(ii) You are different from your brother and sisters. This is called.

a. variation        b. adaptation        c. hereditary        d. mitosis

(iii) In humans, the eye colour is developed due to the effects of:

a. diet        b. environment        c. genes        d. both 'a' and 'b'

(iv) The section of DNA which has information for making a specific protein is called:

a. DNA strand        b. nucleotide        c. chromosome        d. gene

(v) Chromosomes are made of:

a. DNA only        b. protein only        c. DNA, proteins and fats        d. DNA and proteins

(vi) The characters which are passed from parents to offspring:

a. hereditary characters        b. non-inheritable characters

c. environmental characters        d. none of these

(vii) An event that occurs during interphase:

a. division of nucleus        b. division of cytoplasm

c. duplication of chromosomes        d. formation of cell wall

(viii) Reduction of chromosomes take place during:

a. mitosis        b. meiotic-I        c. meiotic-II        d. both mitosis and meiotic-II

(ix) In humans, a sperm has 23 chromosomes. Egg cell has:

a. 23 chromosomes        b. 46 chromosomes        c. no chromosomes        d. 69 chromosomes

(x) Zygote is formed by the fusion of:

a. two sperm cells        b. two egg cells        c. two somatic cells        d. sperm cell and egg cell

2 Write short answers.

(i) What is the primary source of genetic variation?

Ans.

The primary source of genetic variation is mutation. Mutation is a change in the genetic material (gene).

(ii) Plants are adapted to their environment. Give examples.

Ans.

Plants are adapted to their environment in many ways. This is because they have special features that help them to survive.

Examples:

1. The best example is cactus plant to survive in the desert. Its stem can store water.

2. Trees in rainforests  grow very tall to get sunlight.

3. Floating plants like water hyacinth, duckweed and water lily have floating leaves and submerged roots.

(iii) What is difference between variations and adaptations?

Ans.

Variations:

The differences shown by the individuals of one kind of organisms (one species) are called variations.

Examples:

(i) Skin color, blood type, eye color, tongue rolling etc. are genetic variations.

(ii) Language, scar on skin etc. are environmental variations.

Adaptations:

The characteristics of an organism that help it to survive in a given environment are called adaptations.

Examples:

(i) Animals that live in cold areas have adaptations to keep them warm.

(ii) Plants that live in dry areas have adaptations to help them conserve water.

(iv) What is gene?

Ans.

The basic physical and functional unit of heredity is called gene.

(v) Define heredity and describe its importance in transferring of characteristics from parents to offspring.

Ans.

Heredity:

The transmission of characteristics from parents to offspring is called heredity.

Importance of Heredity:

Importance of heredity is stated as:

(i) During reproduction, living things pass on their characteristics to their offspring. This is the reason that babies look like their parents.

(ii) Plants grown from seeds resemble their parent plants.

(vi) Differentiate between mitosis and meiosis.

Ans.

Mitosis:

• During mitosis, two daughter cells are formed from parent cell.
• Mitosis occurs in somatic cells.
• The number of chromosomes in the daughter cells remain the same as in parent cell.

Meiosis:

• During meiosis, four daughter cells are formed from the parent cell.
• The number of chromosomes in the daughter cells is reduced to half as compared to that in the parent cell.
• Meiosis occurs to produce gametes in animals or spores in plants.

(vii) What is the structure of DNA?

Ans.

According to Watson and Crick's model, DNA consists of two strands of nucleotides. The two strands are held together by hydrogen bonds between nitrogenous basis of nucleotides of opposite strands. The nitrogenous base Adenine of one strand makes bonds with Thymine of the opposite strand. Similarly, Guanine of one strand makes bonds with Cytosine of the opposite strand.

General Science 8th Class Chapter 2 Human Nervous System Solved Exercise

General Science

8th Class

Chapter 2

Human Nervous System

Questions

1. Encircle the correct option.

(i) The neurons which decide about the action for a certain stimulus:

a. sensory neuron        b. motor neuron        c. inter-neuron        d. all of above

(ii) The parts of a neuron which receive messages are:

a. cell bodies        b. dendrites        c. axons        d. nuclei

(iii) Heartbeat is controlled by:

a. cerebrum        b. cerebellum        c. medulla oblongata        d. hypothalamus

(iv) Many axons present side by side and enclosed in a common sheath from:

a. nerve cell        b. nerve        c. dendrite        d. spinal cord

(v) Sensory neurons carry messages towards:

a. muscles        b. glands        c. sense organs        d. brain and spinal cord

(vi) Which part of brain is involved in precise and accurate body movements?

a. Cerebellum        b. Cerebrum        c. Thalamus        d. Midbrain

(vii) When you have a toothache, you feel pain because:

a. there is a cavity in your tooth

b. tiny bits of food are left between your teeth

c. bacteria digest the food left between your teeth and produce an acid

d. the cavity reaches the nerves and the nerves send a message to the brain

2 Write short answers.

(i) Write the functions of midbrain, hypothalamus and spinal cord.

Ans.

Midbrain:

Midbrain is a small part of the brain which is present below the cerebrum. It receives information from sense organs which is then passed to the appropriate part of the forebrain.

Hypothalamus:

Hypothalamus lies at the base of thalamus. It controls body temperature, hunger and thirst.

Spinal cord:

Spinal cord creates a link between brain and different body parts. It also controls some reflex actions (immediate and involuntary actions) and some other involuntary actions.

(ii) Differentiate between:

    (a) Receptors and effectors

    (b) Neuron and nerve

    (c) Sensory neuron and motor neuron

    (d) Cerebrum and cerebellum

Ans.

(a) Receptors and effectors

Receptors:

• Detect stimuli from the environment.
• Convert stimuli into electrical impulses.
• Send impulses to the brain and spinal cord.
• Examples include the eyes, ears, nose, tongue, and skin.

Effectors:

• Respond to stimuli by carrying out instructions from the brain and spinal cord.
• Examples include muscles and glands.

 (b) Neuron and nerve

Neuron:

Neuron or nerve cell is the basic structural and functional unit of the nervous system. All parts of the neuron system, i.e., brain, spinal cord and nerves are made up of neurons. Neurons transmit messages in the form of electrochemical waves.

Nerve:

A nerve is cable-like bundle of axons enclosed in a common sheath. Nerve transmits messages from one part of body to another.

 (c) Sensory neuron and motor neuron

Sensory neuron:

Sensory neurons carry nerve impulses from sense organs (ears, eyes, skin, tongue, nose, etc.) to the central nervous system.

Motor neuron:

Motor neurons carry nerve impulses from central nervous system to effectors (muscles and glands),i.e., the parts which respond.

 (d) Cerebrum and cerebellum

Cerebrum:

Cerebrum is the topmost and the largest part of the brain. It is divided into right and left cerebral hemisphere. Each hemisphere controls the opposite side of the body. In general, the left hemisphere controls speech, comprehension, arithmetic, and writing. The right hemisphere controls creativity, spatial ability, artistic, and musical skills. Inside cerebrum there is a small structure called thalamus. It controls many sensory functions.

Cerebellum:

Cerebellum lies under the back part of the cerebrum. It acts as a controller for maintaining the body balance and making precise and accurate movements.

(iii) Write a note on the central nervous system.

Ans.

Central nervous system acts as a control centre of the whole nervous system. It comprises brain and spinal cord.

Brain:

Human brain is enclosed in a body skull called cranium, and consists of billions of inter-neurons. It is divided into the following parts.

1. Forebrain:

Forebrain is the largest part of the brain. It consists of three main parts, i.e., cerebrum, thalamus and hypothalamus. Cerebrum is the topmost and the largest part of the brain. It is divided into right and left cerebral hemisphere. Each hemisphere controls the opposite side of the body. In general, the left hemisphere controls speech, comprehension, arithmetic, and writing. The right hemisphere controls creativity, spatial ability, artistic, and musical skills. Inside cerebrum there is a small structure called thalamus. It controls many sensory functions. Hypothalamus lies at the base of thalamus. It controls body temperature, hunger and thirst.

2. Midbrain:

Midbrain is a small part of the brain which is present below the cerebrum. It receives information from sense organs which is then passed to the appropriate part of the forebrain.

3. Hindbrain:

Hindbrain consists of three parts, i.e., cerebellum, pons and medulla oblongata.

Cerebellum lies under the back part of the cerebrum. It acts as a controller for maintaining the body balance and making precise and accurate movements. Pons is an oval structure present beneath midbrain. It controls many functions like sleep, swallowing, equilibrium and taste, etc. Medulla oblongata forms the posterior part of the brain where it is connected with the spinal cord. Medulla oblongata controls heartbeat, breathing and digestion, etc. Medulla oblongata keeps on working when rest of the brain goes to sleep.

Spinal Cord:

Spinal cord is an extension of medulla oblongata. It runs backwards inside the backbone up to its lower end. It is also made up of inter neurons.

Spinal cord creates a link between brain and different body parts. It also controls some reflex actions (immediate and involuntary actions) and some other involuntary actions.

(iv) Identify and label the following diagram.

Ans.

General Science 8th Class Chapter 1 Ecology Solved Exercise

 General Science

8th Class

Chapter 1

Ecology

Questions

1. Encircle the correct option.

(i) The phenomenon which does not lead to global warming:

a. greenhouse effect        b. ozone depletion        c. deforestation        d. photosynthesis

(ii) The feeding level of an organism in an ecosystem is called ________ .

a. tropic level        b. secession level        c. food chain        d. food web

(iii) The graphical representation of trophic relationship of organisms in an ecosystem is called ________ .

a. food chain        b. tropic level        c. ecological pyramid        d. predation

(iv) All the food chains are joined together to form _________ .

a. ecological pyramid        b. food web        c. tropic level        d. none of these

(v) The energy of the Sun is trapped as chemical energy by ________ .

a. producers        b. primary consumers        c. secondary consumers        d. tertiary consumers

(vi) Consumers that actively hunt other organisms are called ________ .

a. prey        b. predator        c. symbiont        d. competitor

(vii) A relationship where two species live together closely is called _________ .

a. predation        b. symbiosis        c. competition        d. none of these

(viii) We can solve environmental problems by:

a. reducing pollution        b. plantation        c. protection of endangered species        d. all of these

(ix) Ecological imbalance is caused by:

a. migration        b. overhunting        c. over population        d. all of these

2 Write short answers.

(i) What are ecological pyramids?

Ans.

The different feeding levels of organisms in an ecosystem are called trophic levels e.g., producers, herbivores, primary carnivores etc. Biologists express the trophic relationships by the diagram that take the shape of pyramids. This diagram is thus called ecological (or biological) pyramid. Diagram shows that at the base of the pyramid are producers or green plants. The upper levels are occupied by primary, secondary and tertiary consumers in according order. Usually primary consumers are herbivores and the rest are carnivores (or omnivores).

(ii) What is predation?

Ans.

Consumers that actively hurt other organisms are called predators. The organism upon which a predator feeds is called prey. This process is called predation. For example a frog that eats an insect is a predator. The insect is the prey. The frog itself is prey to other organisms such as snakes and storks.

(iii) Differentiate between:

(a) oxygen and carbon cycle            (b) food chain and food web

Ans.

(a) oxygen and carbon cycle

The carbon dioxide and oxygen gases circulate between the constantly between the environment and living organisms in a cyclic way. When plants prepare food in photosynthesis, they take in carbon from the atmosphere in the form of carbon dioxide. In this process, they also release oxygen gas to the atmosphere.

All animals and plants respire to get energy. During respiration they take in oxygen from the atmosphere and release carbon dioxide to atmosphere.

Similarly, during decomposition and combustion of biomass (matter of dead bodies), the oxygen gas present in atmosphere is used and the carbon of biomass is released into the atmosphere in the form of carbon dioxide.

(b) food chain and food web

Production of food and the feeding relationship among organisms at different levels form a chain called food chain. whereas when all animals feed in more than one food chain, these food chains are joined together to make a food web.

(iv) Write any of the solution of environmental problems.

Ans.

Plantation:

There are many benefits of plants. Planting more trees can reduce the level of air pollution as plants absorb pollutants. It also maintains the temperature of an area at a lower level than an area that does not have trees. They are also the habitat for birds and birds and many other animals. Trees are also a source of fruits and flowers. Each and everyone of us have to plant trees and enhance the quality of life.

(v) Name some of the factors which can cause ecological imbalance.

Ans.

Introduction of new species in an ecosystem, overhunting, migration, etc. are the factors which can cause ecological imbalance.

General Science 7th Class Chapter 12 Earth and Space Solved Exercise

 

General Science

7th Class

Chapter 12

Earth and Space

Questions

12.1 Encircle the correct option.

1. An object is attracted towards the Earth due to:

a. pull        b. push        c. gravity        d. friction

2. Which of the following is the major cause of tides?

a. heating oceans by the Sun

b. gravitational pull of the Moon

c. earthquakes on the surface of the ocean floor

d. change in  the wind direction

3. Seasons on the Earth's surface are caused by:

a. spin motion of the Earth about its own axis

b. orbital motion of the Earth around the Sun

c. tilt of Earth on its axis

d. the tilt of Earth and orbital motion of the Earth around the Sun

4. What is the season on 22nd June in the southern hemisphere?

a. spring        b. autumn        c. summer        d. winter

5. The weight of an object on Earth's surface is 600 N. What will be its weight on the Moon's surface?

a. 600 N        b. 300 N        c. 200 N        d. 100 N

6. The tides are highest during:

a. day        b. night        c. half Moon        d. full Moon

12.2 Write short answers.

1. An athlete can jump 5 metre up on the Earth, how high he can jump on the Moon?

Ans.

The force of gravity on Moon surface is 1/6 of that on Earth. If an athlete jumps 5 metre high on Earth, he can jump 30 metres on the Moon.

2. A person can throw a shot put 2 meters away. How long will be his throw on the Moon's surface?

Ans.

If a person can throw a shot 2 metres away at the earth surface, his throw on the moon surface will be 12 metres.

3. Which of the Sun or Moon has a greater pull on the ocean's water? Give reason of your answer.

Ans.

Moon has greater pull on oceans water than that of sun. The reason is that moon is nearer to earth surface than sun.

4. Differentiate force exerted by the Moon on the waters at the near surface and that exerted on the water of far surface.

Ans.

On the near side of Earth, (the side facing moon) the gravitational force of the moon pulls the ocean's water towards it, creating on bulge. On the far side of the Earth, inertia dominates, creating a second bulge. In this way, two bulges of water are formed.

5. What will be the season in Australia when there is summer in Pakistan?

Ans.

Pakistan is in northern hemisphere, and Australia is in Sothern hemisphere. If there is Summer in Pakistan, there will be winter in Australia.

General Science 7th Class Chapter 11 Technology in Everyday Life Solved Exercise

General Science

7th Class

Chapter 11

Technology in Everyday Life

Questions

11.1 Encircle the correct option.

1. Conservation of water means

a.  a using water        b. save water        c. avoiding water        d. wasting water

2. While preparing pickles, which is not used as preserving agent:

a. honey        b. salt        c. vinegar        d. pepper

3. Which is not used in making mango pickle?

a. mango slices        b. honey        c. table salt        d. turmeric powder

4. Which is not used in the preparation of lemon prickle?

a. lemon        b. sugar        c. acetic acid        d. tea leaves

5. Which is not used in the preparation of orange juice?

a. garlic        b. orange        c. sugar        d. water

11.2 Write short answers.

1. What type of irrigation is more beneficial either drip or sprinkler?

Ans.

  Drip irrigation is more beneficial than other types.

2. List the ingredients required for preparation of mango pickle.

Ans.

Unripened mangoes, pickle jar, salt vinegar (preservative agent) mustard seeds etc.

3. What are the ingredients required for preparation of onion pickle.

Ans.

2 cinnamon sticks, 6 whole cloves, pinch crushed red pepper flakes. Freshly squeezed lime juice.

4. Name the ingredients required for preparation of lemon pickle.

Ans.

Lemon cut into circular slices, 1/2 kg sugar 1/2 cup, Acetic acid 1 cup.

5. State the ingredients required for preparation of orange juice.

Ans.

Orange slice, salt, juicer blender, knife, strainer, bowl.

General Science 7th Class Chapter 10 Heat and Temperature Solved Exercise

General Science

7th Class

Chapter 10

Heat and Temperature

Questions

10.1 Encircle the correct option.

1. The degree of hotness or coldness is called:

a. thermal contraction        b. thermal expansion        c. temperature        d. heat

2. The bulb of the thermometer is filled with:

a. oil        b. alcohol        c. water        d. salt

3. Centigrade scale is also called:

a. Fahrenheit scale        b. Kelvin scale        c. Absolute scale        d. Celsius scale

4. The temperature of boiling water in centigrade scale is:

a. 0˚ C       b. 32˚ C        c. 37˚ C        d. 100˚ C

5. The temperature of melting ice in Fahrenheit scale is

a. 0˚ F       b. 32˚ F        c. 100˚ F        d. 212˚ F

6. When a 10 cm iron rod is heated to high temperature:

a. its volume decreases        b. its volume increases

c. its density remains the same        d. none of these

7. The average energy due to movement of molecules in a substance is called:

a. potential energy        b. electric energy        c. kinetic energy        d. chemical energy

8. The energy that transfers from one object to another due to the temperature difference is called:

a. atomic energy        b. heat energy        c. light energy        d. sound energy

9. The gaps are left after every few minutes in the railway tracks, so that:

a. they cannot be de-tracked in summer due to expansion

b. they cannot be de-tracked in winter due to expansion

c. they cannot be de-tracked in summer due to contraction

d. they cannot be de-tracked at night due to contraction

10. The rise of liquid in the thermometer is due to:

a. evaporation        b. contraction        c. expansion        d. sublimation

11. The contraction of the objects on cooling is due to:

a. reduction in size of the particles        b. increase in size of the particles

c. increase in inter particle distances        d. decrease in inter particle distances

12. An empty steel container is sealed and heated, which of the following properties of the gas is likely to increase?

a. mass        b. pressure        c. volume        d. density

10.2 Give short answers.

1. Define heat.

2. Name three modes of heat transfer.

3. Which two temperatures are the base of Celsius and Fahrenheit temperature scales?

4. Give five examples of good conductors of heat.

5. Give five examples of bad conductors of heat.

1. Define heat.

Ans.

Heat is the measure of thermal energy of a substance. It is the total kinetic energy of all the particles of a substance.

2. Name three modes of heat transfer.

Ans.

Three modes of heat transfer are the following:

1. Conduction        2. Convection        3. Radiation

3. Which two temperatures are the base of Celsius and Fahrenheit temperature scales?

Ans.

Melting point and boiling point of water are two temperatures which are base of temperature scales.

4. Give five examples of good conductors of heat.

Ans.

Five good conductors of heat are Iron, Copper, Silver, Aluminum and Gold.

5. Give five examples of bad conductors of heat.

Ans.

Five bad conductors are wood, rubber, glass, mica and cotton.