FORM 2

The world through our senses

1. Sensory organs

Sensory organs Type of senses Stimuli detected

Skin Touch Touch, temperature, pressure, pain

Nose Smell Chemical in air

Tongue Taste Chemical in food

Ear Hearing Sound

Eye Sight Light

2. Pathway from stimulus to response

Stimulus → receptors→ nerves → brain →nerves → effectors → response

3. Sense of touch is the sense that is sensitive towards the touch pain, pressure, cold and

heat.

4. The skin of human is divided into two layers, dermis and epidermis.

5. Types of receptors :

- Pain receptor

- Heat receptor

- Pressure receptor

- Cold receptor

- Touch receptor

6. Sensitivity of skin depends of two factors:

- Thickness of the epidermis

- Number of receptors

7. Sense of smell is the sense that can detect stimuli produced by chemicals.

8. The sensitivity of nose depends of two factors:

- The strength of the smell

- The presence of mucus

9. The sense of taste is the sense that can detect stimulus produced by flavoured

chemicals.

10. The tongue is the sensory organ for taste.

11. The tongue enables us to detect sweet, salty, sour, and bitter.

12. The surface has many taste buds.

13. The sense of hearing is the sense that can detect source of sound produced by vibrating

object.

14. The function of each part of the ear

a.) Pinna – collects and directs sound wave into ear canal

b.) Ear canal – directs sound waves to the eardrum

c.) Eardrum – vibrates and transfers sound waves to the ossicles

d.) Ossicle – intensify the vibration

e.) Eustachian tube – balances air pressure

f.) Oval window – transfer sound vibration from the middle ear to inner ear

g.) Cochlea – convert sound vibrations into nerve impulse

h.) Semicircular canals – detect position and movement of head to keep us stay balance

i.) Auditory nerves – transfer impulses from the cochlea to the brain

15. The sense of sight is the sense that can detect light stimulus

16. The function of each part of the eye

a.) Sclera – maintains the shape of eyeball , protects the eyeball

b.) Cornea – allow light to enter the eye , focuses light onto the retina

c.) Choroid – supplies oxygen and nutrients to the eye, absorbs and prevent internal

light reflection in the eye

d.) Conjunctiva – protects the cornea

e.) Iris – determines the colour of the eye, controls the size of the pupil

f.) Pupil – allows light to enter the eye and controls the size of the pupil

g.) Lens – refracts and focuses light onto the retina

h.) Ciliary muscle – changes the thickness of the lens

i.) Suspensory ligament – supports and holds the lens

j.) Vitreous homour – maintains the shape of the eyeball

k.) Aqueous humour – refracts and focuses light entering the eye

l.) Retina – detects light stimulus and changes it into impulse

m.) Optic nerves – transmit nerve impulses from the retina to the brain

Light and sight

1. Light is a form of energy that can be detected by our eyes.

2. Light travels in a straight line.

3. Light can be reflected, refracted, dispersed.

4. The rate of reflected light by a surface depends on the colour and nature of the surface.

5. When light travels at an angle through a medium of different density, the light will be

deflected. This deflection is known as refraction of light.

Defects of vision and corrections

1. Short-sightedness

- Near object are seen clearly

- Distant objects look blur

- Eyeball is too long or big

- Eye lens is too thick

- Image is formed in front of the retina

- Wear glasses with concave lens

2. Long-sightedness

- Distant objects are seen clearly

- Near objects look blur

- Eyeball too short or small

- Eye lens is too thin

- Image is formed behind the retina

- Wear glasses with convex lens

3. Defects of the eye include blindness, colour blindness, astigmatism and blurred vision.

4. Colour blindness is a hereditary defect.

5. Astigmatism is a problem of hazy vision caused by irregular surface of the cornea.

Astigmatism can be corrected with a cylindrical lens or through surgery.

6. Optical illusion occurs when the brain cannot interpret nerve impulses received properly.

7. The blind spot is the place where the optic nerves leave the eyeball.

8. The stereoscopic vision is a vision using both eyes at the front of the head.

9. Advantages of the stereoscopic vision :

- Sees three-dimensional pictures of object

- Enables more accurate estimation of distance and position

10. Monocular vision is a vision by animals with eyes at the side of the head

11. Advantages of the monocular vision :

- Have a wide vision field

- Cannot estimate distance accurately

Sound and Hearing

1. Sound is produced by the vibrations of objects and is a form of energy carried in the

form of waves.

2. Sound can be transferred through solids, liquids, gases.

3. Sound cannot be transferred trough a vacuum.

4. Sound can be reflected or absorbed by the surface of an abject.

5. Surface that are smooth, even and hard are good sound absorbers and produce weak

echo.

Stimuli and responses in plants

Tropism

1. Plants cannot move from one place to another but can move towards a stimulus.

2. The movements of plants are influenced by stimuli such as light, gravity, water, chemical

substances and contact with external objects.

3. Tropism is the growth in parts of a plant in response towards or away from an external

stimulus.

4. Growth of a part of a plant towards an external stimulus is known as positive tropism

while growth away from an external stimulus is known as negative tropism.

5. Tropism involves tips of shoots and roots of plants.

6. Types of tropism :

a.) Phototropism

b.) Geotropism

c.) Hydrotropism

d.) Thigmotropism

7. Phototropism is the response of a plant towards light stimulus.

8. Geotropism is the response of plants toward gravitational pull.

9. Hydrotropism is the response of plants toward water.

10. Thigmotropism is the response of plants towards touch.

11. Shoots of plants show :

- Positive phototropism

- Negative phototropism

12. Roots of plants show :

- Positive phototropism

- Positive geotropism

13. Tendrils of plants show :

- Positive thigmotropism

- Negative hydrotropism

Nutrition

1. Classes of food

- Carbohydrates

- Proteins

- Fats

- Vitamins

- Water

- Fibre

- Minerals

2. Carbohydrates are compounds made up of carbon, hydrogen and oxygen.

3. Ration of hydrogen to oxygen is 2 : 1

4. Carbohydrates are formed from simple molecules known as simple sugars.

5. Carbohydrates can be divided into three types based on the number of simple sugars in

the molecules:

a.) Monosaccharide [ made up of one unit of simple sugar ]

Example – glucose, fructose, galactose

b.) Disaccharide [ made up of two units of simple sugars ]

Example – lactose, maltose, sucrose

c.) Polysaccharide [ made up of many units of simple sugars ]

Example – starch, glycogen, cellulose (fibre)

6. Starch food such as bread, rice, potatoes.

7. Sugary food such as honey, fruits, sugar cane, milk.

8. Cellulose such as those found in the plant cell walls.

9. Function of carbohydrates :

a.) To supply energy

b.) As stored food in animal and plant cells

10. Food test for carbohydrates :

a.) The presence of starch can be tested by iodine solution. When the iodine is dripped

onto a starch solution, the solution changes to dark blue or blue-black.

b.) The presence of glucose, galactose, lactose and maltose can be tested with

Benedict’s solution or Fehling’s. When Benedict’s solution is heated gently in a

water bath, glocuse solution for two minutes, the solution changes colour gradually

from light blue to green, yellow, orange, and finally a brick-red precipitate is formed.

11. Proteins are nutrients containing carbon, hydrogen, oxygen and nitrogen. Some proteins

also contain sulphur and phosphorus.

12. The basic unit of proteins is amino acid.

13. Function of protein:

a.) For the growth of the body

b.) For formation of new cells

c.) To synthesise other protein compounds

d.) To provide energy

14. Test for proteins:

a.) The test for the presence of proteins in food samples is known as Million’s test.

b.) A red coagulation is formed when food containing proteins is heated together with

Million’s reagent.

15. Fats are compounds that contain carbon, hydrogen and oxygen.

16. The ration of hydrogen to oxygen is more than 2 : 1.

17. The basic unit of fats is fatty acids combined with glycerol.

18. Function of fats:

a.) As a rich source of energy

b.) As a heat insulator

c.) As a solvent for vitamin A, D, E, and K.

d.) Prevent the loss of water.

19. Test for fats:

a.) The test for the presence of fats in food samples is known as the alcohol – emulsion

test.

b.) A few drops of ethanol are added to a very small amount of fats and mixture is

shaken vigorously to dissolve fats. An equal amount of distilled water is added. A

cloudy white (milk-like) emulsion indicates the presence of fats or oils.

20. Vitamins are organic compounds that contain carbon and hydrogen. Some vitamins also

contain oxygen, nitrogen, cobalt, and zinc.

21. Minerals are inorganic substances present in the form of ions.

22. Fibre is the part of food that cannot be digested by our body.

23. Fibre is made up of cellulose that exists as the main building material in the plant cell

walls.

24. Fibre is important to encourage peristalsis in intestines and ensure the smooth

movement of food substances as well as facilitate defecation.

25. The lack of fibre can cause faeces to store in the large intestines for a long period time.

It is difficult to get rid of faeces that have turned dry and hard in the large intestines,

this condition is called constipation.

26. Water makes up about three quarters or 70% of our body weight.

27. Function of water:

a.) As a solvent for chemicals

b.) As a transport medium

c.) To regulate and maintain body temperature

d.) To regulate pressure of body fluids

e.) As lubricant to reduce friction between joints of bones

f.) To assist smooth peristalsis.

g.) As moist substance in cells, tissues and internal organs.

28. Water is expelled from the body through physiological processes such as perspiration,

respiration, urination and defecation.

29. Factors that determine a person’s balanced diet:

a.) Age

b.) Body size

c.) Sex

d.) Occupation

e.) Climate

f.) State of health

30. The amount of energy in food is known as calorie.

31. Calorie is defined as the amount of heat needed to increase 1g of water by 1°C at 1

atmospheric pressure.

32. The SI unit to measure the amount of energy in food is joule (J).

33. A balanced diet is important to:

a.) Maintain optimum health of the body

b.) Ensure body growth

c.) Repair and replace old or damaged tissues

d.) Ensure sufficient energy for the body according to its needs

34. Diet imbalance in the long run causes a person to contract deficiency disease. This

condition is known as malnutrition.

35. Digestion is a process of breaking down large or complex food molecules into simpler

and smaller soluble molecules that are readily absorb by the body.

36. Digestion in the body is carried out by specific system known as the digestion system.

37. The digestive system breaks down carbohydrates into glucose, proteins into amino acids

and fats into fatty acids and glycerol.

38. Digestion is said to take place if food is found in the alimentary canal. The passage of

food in the alimentary canal is as follows:

Mouth → oesophagus → stomach → small intestine → large intestine → rectum → anus

39. Physical digestion involves the break down of large pieces of food into smaller pieces by

physical action of chewing and grinding by the teeth.

40. Saliva softens the food particles and shapes them into a lump called bolus.

41. Chemical digestion is the process of breaking down complex food into simpler form by

chemical means.

42. Chemical digestion in the alimentary canal occurs in the mouth, stomach and small

intestine

43. There are three types of digestive enzymes:

a.) Amylase to break down starch.

b.) Protease to break down proteins.

c.) Lipase to break down fat.

44. When the food enters the stomach, the stomach wall will secrete gastric juice that

contains hydrochloric acid, proteases and water.

45. The small intestine secretes enzymes to complete the digestion of food and absorption

of digestive products.

46. The small intestine is made up three parts. They are duodenum, jejunum and ileum.

47. In the duodenum, chime is mixed with two types of secretions, bile from the gall bladder

and pancreatic juice from the pancreas.

48. Bile is a yellow-greenish liquid produced by the liver and stored in the gall bladder.

49. Bile is directed into the duodenum from the gall bladder via the bile duct.

50. Bile does not contain enzyme. It is alkaline because it contains sodium hydrogen

carbonate salt. Bile neutralizes acids in the stomach and provides an alkaline medium

for the action of enzymes from the pancreatic juice and small intestine.

51. Bile also emulsifies fats that are it breaks up fats into smaller droplets by reducing the

surface tension of fat droplets. This process is known as breakdown of fats or emulsion.

This aims to increase the surface area of fats for the action of enzymes as well as

accelerate the digestion of fats.

52. Function of enzymes in the pancreatic juice:

a.) Pancreatic amylase breaks down starch into maltose.

Starch maltose

Pancreatic amylase

b.) Lipase breaks down fats into fatty acids and glycerol.

Fat Fatty acids + Glycerol

c.) Protease breaks down proteins into polypeptides.

Proteins polypeptides

53. Function of enzymes in intestinal juice:

a.) Protease breaks down polypeptides into amino acids.

b.) Lipase breaks down fats into fatty acids and glycerol.

c.) Maltase breaks down maltose into glucose.

d.) Sucrose breaks down sucrose into fructose and glucose.

e.) Lactose breaks down lactose into galactose and glucose.

54. Vitamins and minerals are not digested in the alimentary canal as they exist in their

simple original forms.

55. Products of digestion, vitamins and minerals will be absorbed into the bloodstream

through the walls of the small intestine by diffusion. This process is known as absorption.

56. The small intestine has special adaptability characteristics to increases its efficiency in

the process of absorption.

57. Villi increase the surface area to speech up the absorption process. The surface area for

absorption is about 40m².

58. Villi also contain many blood capillaries and lacteals to increase the absorption of

products of digestion.

59. Undigested substances such as fibre will be converted into faeces before being expelled

from the anus by defecation.

60. Food must be handled with care to prevent food poisoning and to retain nutrients.

Biodiversity

1. A classification system is required to group living things methodically because of their

large number and types.

2. Animals can be divided into vertebrates and invertebrates.

3. Vertebrates :

- With backbones

- Main support is endoskeleton which consists of bones.

4. Invertebrates :

- Without backbones

- Main support is exoskeleton and fluid pressure

5. Vertebrate can be divided into five groups, namely fish, amphibians, reptiles, birds and

mammals.

Lipase

Protease

6. The characteristics of vertebrates are as follows :

Classes of vertebrates Characteristics

Fish (Pisces) - Live in fresh water or sea water - Body is covered with slimy scales - Fins and tails are used to swim and balance the

body - Breathe through gills - Cold-blooded - Lay eggs

Amphibians - Can live on land and in the water - Have moist and exposed skin - Cold-blooded - Lay eggs - Have webs - Do not have external ears

Reptiles - Have dry and scaly skin - Most lay eggs

- Cold-blooded - Breathe through lungs - Have one type of teeth - Teeth are sharp and cone-shaped

Birds - Live on land - Covered with feather - Feathers are waterproof and can trap heat to keep

the body warm - Can swim - Can fly - Lay eggs

- Warm-blooded - Breathe through lungs - Do not have teeth but use beak to peck - Hard scaly legs and sharp claws

Mammals - Most live on land - Cover with hair or fur - Skin has sweat glands - Warm blooded - Breathe through lungs

7. Invertebrates are animals without backbones.

8. Plants can be classified according to their common characteristic.

9. Classification of plants by common characteristics:

a.) Grow on land

b.) Grow in water

c.) Woody stem

d.) Shrub

e.) Flowering

f.) Non-flowering

g.) Have seeds

h.) Have spores

i.) Net-veined leaves

j.) Parallel-veined leaves

10. Plants can be divide into flowering and non-flowering

11. Flowering can be divided into two groups, the monocotyledons and the dicotyledons.

12. Cotyledon is the main seed leaf for the germination of new seedlings.

13. Cotyledon contain starch as food for the seeds that are unable to make their own food

14. Monocotyledons

- Seed has one cotyledon

- Fibrous root system, which consists of many roots of equal size

- Leaves have parallel veins

- Stem is non-woody and soft

- Example : wild grass, orchid, maize, sugarcane, palm trees, paddy

15. Dicotyledons

- Seed has two cotyledons

- Tap root system, which consists of small roots that branch out of one main root

- Leaves have net veins

- Stem is woody and hard

- Examples: rose tree, bougainvillea, angsana tree, balsam plant, guava tree

16. Non – flowering need to reproduce through spores.

Interdependence among living organisms and the environment

1. Ecology is the study of relationship between living things as well as the relationship

between living things and the environment.

2. Species is a group of organisms that have common characteristics that can breed among

themselves to produce fertile offspring.

3. Population is a group of organisms of the same species living in the same habitat.

4. A community consists of several types of interdependent populations of organisms living

together in one habitat.

5. Habitat is the natural are where an organism lives and reproduces.

6. Organism obtains food and protection from their habitats.

7. All organisms living in a habitat interact to maintain the balance in the habitat.

8. Ecosystem is made up of organisms that interact with one another as well as with non-

living things in their surroundings.

9. Living organisms are interdependent. Examples of interdependence between living

things are:

a.) Supply of gases

b.) Sources of food

c.) Shelter

10. Living things and non-living things interact with one another to maintain a balanced

ecosystem.

11. Interaction is important for the survival of living things.

12. There are different types of interactions, such as prey-predator, symbiosis and

competition.

13. Predators are organisms that hunt and eat other organisms for food.

14. Preys are organisms hunted by the predators for food.

15. Symbiosis is any close relationship or interaction between two organisms of different

species.

16. Examples of symbiosis are:

- Commensalism

→A relationship in which one organism [the commensal] benefits and the other [the

host] is not affected.

- Mutualism

→A relationship in which both organisms benefit.

- Parasitism

→A relationship in which one organism benefits but the organism that is harmed is the

host.

→The organism that benefits is the parasite and the organism that is harmed is the host.

→The parasite lives on or inside its host body and obtains nutrients from the host.

17. Competition takes place when organisms living in the same area compete to obtain

common needs such as shelter, water, mate, minerals, food, or light.

18. Competition occurs when the common needs in an ecosystem are limited.

19. The stronger organism will dominate an area and the smaller or weaker one will be

eliminated or die.

20. Biological control is a method to control the number of a pest organism [prey] by using

its predator.

21. Biological control is better compared to chemical control [use of pesticides] because it is

non-toxic and does not harm other organism which is not pests.

22. Organisms can be classified as producers, consumers and decomposer according to their

relationships in term of sources of food.

23. Producers are organisms that can manufacture their own food

24. Green plants are known as producers because they can make their own food by using

carbon dioxide, water and energy from sunlight.

25. Consumers are organism that obtain food from other organisms

26. Consumers are usually animals cannot make their own food.

27. Consumers can be divided into three types:

a.) Primary consumers

b.) Secondary consumers

c.) Tertiary consumers

28. Primary consumers are consumers that feed directly on plants and are normally

herbivorous animals or omnivorous animals.

29. Secondary consumers are consumers that feed on primary consumers.

30. Tertiary consumers are consumers that feed on secondary consumers.

31. Decomposers are microorganisms that break down tissues of dead organisms into

simpler substances.

32. Scavengers feed on dead plants and animals and break them down into smaller parts.

33. A food chain shows the relationship between food and organisms in an ecosystem.

34. A pyramid of numbers shows the number of organisms at each stage of a food chain.

35. Photosynthesis is a process in which green plants manufactures food from carbon

dioxide and water in the presence of sunlight and chlorophyll.

36. Oxygen cycle is the continuous process of taking and returning oxygen into the

atmosphere.

5

eagles

150 snakes

3000 mouse

3000000 blades of grass

Water +

Carbon

Dioxide Glucose + Oxygen

Light

Chlorophyll

37. Carbon cycle is the continuous cycle of taking and returning carbon in the form of

carbon dioxide to the atmosphere.

Water and solution

1. Kinetic theory is an explanation of how particles in matter behave.

2. Water can exist in three states, solid, liquid and gas.

3. Water changes blue cobalt chloride paper to pink.

4. Water changes white anhydrous copper sulphate to blue.

5. Water is a compound. Therefore, the components of water can only be broken down

chemically.

6. The way of breaking water using electrical energy is known as electrolysis.

7. Electrolyte is added into the water to increase the conductivity of water and to speed up

the process of electrolysis.

8. Electrode is an electric conductor in the form of a plate or a rod immersed into water.

9. There are two types of electrodes:

a.) Anode [positive electrode]

b.) Cathode [negative electrode]

10. Water is formed from two elements: hydrogen and oxygen

11. Oxygen is released at the anode.

12. Hydrogen is released at the cathode.

13. The volume of hydrogen is twice the volume of oxygen. So, the ratio of the volume of

hydrogen to oxygen in one water molecule is 2 : 1

14. A water molecule consists of two atoms of hydrogen and one atom of oxygen. Therefore,

the formula for water is written as H, O.

15. Evaporation is the process of liquid changing into water vapor at any temperature lower

than the boiling temperature of the liquid.

16. Factors affecting the rate of evaporation:

a.) Humidity of air decreases

b.) Surrounding temperature rises

c.) Surface area of water

d.) Air movement

17. Solute is a substance that can dissolve in a liquid.

18. Solvent is a liquid that dissolves a substance.

19. Solution is a product of mixture formed when a solute dissolves in a solvent.

20. There are three types if solutions:

a.) Dilute solution

b.) Concentration solution

c.) Saturated solution

21. Dilute solution is produced when a little solute is dissolved in a solvent

22. A concentrated solution is produced when a lot of solute is dissolved in a solvent.

23. A saturated solution is produced when the maximum amount of solute is dissolved in a

solvent until no more solute can be dissolved.

24. Liquid mixtures can be classified into solutions and suspensions, depending on the

nature of the solute and its liquid solvent.

25. A solution is the mixture obtained when a substance dissolves in a liquid.

26. A suspension is the mixture obtained when a substance is suspended in a liquid and

does not dissolve in it.

27. Solubility is defined as the maximum amount of solute that can dissolve in a given

amount of solvent at a particular temperature to produce a saturated solution.

Solubility =

28. Rate of dissolving

a.) Size of solute particles

b.) Rate of stirring

c.) Temperature of solvent

d.) Volume of solvent

e.) Water is known as the universal solvent because it can dissolve most substance.

29. The properties of acids:

a.) Have a sour taste

b.) Have a corrosive nature

c.) Have pH values less than 7

d.) Reacts with metals

e.) Changes a moist litmus paper from blue to red

Acid = metal → hydrogen = salt

f.) Reacts with carbonates to produce carbon dioxide, water and other salts.

g.) Turns lime water cloudy

30. The properties of alkalis:

a.) Taste bitter and smooth like soap

b.) Have a corrosive nature

c.) Have pH values of more than 7

d.) Changes moist litmus paper from red to blue.

e.) Reacts with ammonium salts to produce ammonia gas, water, and other salt

31. The greater the pH value, the fewer the hydrogen ions in the solution, so the acidity of

the acid also decrease.

32. The greater the pH value, the more hydroxide ions in the solution, the greater the

alkalinity of the alkali.

33. Acid base indicators are chemical substances that show colour changes in acidic and

alkaline solutions.

Mass of solute (G)

Volume of solvent (100ml)