Science - e- · PDF fileThe heart is a muscular organ with walls made of cardiac ... Frog...

iv Science Mathayom 2

Chapter 1 Food and Addictive 11.1 Classes of Food 21.2 Importance of Balanced Diet 91.3 Drugs 131.4 Alcoholic Drinks 161.5 Smoking 19Mastery Practice 22

Chapter 2 Systems in Humans and Animals 252.1 Digestive System in Humans 262.2 Digestive Systems in Animals 322.3 Circulatory System in Humans 342.4 Circulatory Systems in Animals 402.5 Respiratory System in Humans 412.6 Respiratory Systems in Animals 472.7 Excretory System in Humans 492.8 Excretory Systems in Animals 50Mastery Practice 53

Chapter 3 Reproduction 583.1 Sexual and Asexual Reproduction 593.2 Male Reproductive System 643.3 Female Reproductive System 673.4 Menstrual Cycle 693.5 Fertilization and Pregnancy 723.6 Importance of Pre-Natal Care 753.7 Importance of Research in Human Reproduction 763.8 Biotechnology in Reproduction of Animals 81Mastery Practice 84

Chapter 4 Coordination and Responses 874.1 Stimuli and Responses in Humans and Animals 884.2 Human Nervous System 93Mastery Practice 104

2.2 Digestive Systems in Animals 322.3 Circulatory System in Humans 342.4 Circulatory Systems in Animals 402.5 Respiratory System in Humans 412.6 Respiratory Systems in Animals 472.7 Excretory System in Humans 492.8 Excretory Systems in Animals 50Mastery Practice 53

2.2 Digestive Systems in Animals 322.3 Circulatory System in Humans 342.3 Circulatory System in Humans 342.3 Circulatory System in Humans 34

Mastery Practice 53Mastery Practice 53

Content Focus Sci M2.indd 4 12/5/12 9:29 AM

Contents v

Chapter 5 Elements, Compounds and Mixtures 1075.1 Elements 1085.2 Compounds 1125.3 Mixtures 1125.4 Separation Techniques 1155.5 Radioactive Elements 120Mastery Practice 122

Chapter 6 Energy and Chemical Changes 1266.1 Physical and Chemical Changes 1276.2 Chemical Equations 1316.3 Energy and Chemical Reactions 1356.4 Factors A� encting the Rate of a Reaction 1386.5 Chemical Reactions and Chemical Substances in Everyday Life 141Mastery Practice 146

Chapter 7 Forces and Motion 1507.1 Understanding Force 1517.2 Resultant Forces on a Same Plane (Net Force) 1527.3 Resultant Forces on Static Objects and Moving

Objects with Constant Velocity 156Mastery Practice 160

Chapter 8 Light 1638.1 Properties of Light 1648.2 Re� ection of Light 1658.3 Refraction of Light 1688.4 Light and Colors 1718.5 Uses of Light 174Mastery Practice 177

Chapter 9 Soil 1819.1 Soil 1829.2 Soil Formation 1879.3 Soil Uses and Soil Improvement 188Mastery Practice 193

Chapter 10 The Earth 19510.1 Layers of the Earth 19610.2 Rocks 19710.3 Minerals 20210.4 Fossil Fuels 20510.5 Natural Water 207Mastery Practice 210

10.2 Rocks 19710.3 Minerals 20210.4 Fossil Fuels 20510.5 Natural Water 207Mastery Practice 210

10.2 Rocks 197

10.5 Natural Water 207Mastery Practice 210

What are the structure and components of our Earth?

Content Focus Sci M2.indd 5 12/5/12 9:29 AM

By the end of this chapter, you should be able to

•explainthestructuresandfunctionsofdigestivesystems,circulatory

systems,respiratorysystemsandexcretorysystemsofhumansandanimals.

•explaintherelationshipofvarioussystemsofhumansandapplyacquiredknowledgeforusefulpurposes.

Systems in Humans and Animals

2

Do you recognize these systems in our body?

02 Focus TB SC M2.indd 25 12/11/12 3:48 PM

26 Science Mathayom 2 Chapter 2 Systems in Humans and Animals 27

2.1 Digestive System in Humans

Digestion is the process of breaking down large food molecules into smaller soluble molecules that can be readily absorbed by the body.

The human digestive system includes the alimentary canal and organs such as the salivary glands, stomach, liver, gall bladder and pancreas.

Digestion occurs in an eight-meter long tube called the gut or alimentary canal.

Mouth

Salivary gland

Liver

Gall bladderPancreas

Small intestine

Rectum

Esophagus

Stomach

Large intestine

Anus

Human digestive system

Below is the flow of food particles in the alimentary canal.

Mouth Esophagus Stomach

DuodenumSmallintestine

LargeintestineAnus

Enzymes are protein substances which act as catalysts and generally speed up the chemical reactions in our body. Enzymes that break down food substances in the gut are called digestive enzymes.

There are three main types of digestive enzymes:(a) Carbohydrases break down carbohydrates(b) Proteases break down proteins(c) Lipases break down fats and oils

http://health.howstuffworks.com/adam-200142.htmYou can view the animation of our digestive system here.


30 Science Mathayom 2 Chapter 2 Systems in Humans and Animals PB

Absorption of digested food

Showing the action of salivary amylase on starch

Materials/apparatus: Distilled water, 1% starch solution, saliva solution, Benedict’s solution, iodine solution, test tubes, glass rod, stopwatch, beakers, wire gauze, Bunsen burner and tripod stand

Procedure: 1. The mouth is rinsed once with distilled water to cleanse it. It is rinsed again for a

second time to collect the saliva solution. 2. 5 cm3 of starch solution and 5 cm3 saliva solution are poured into a test tube. 3. The mixture is stirred with a glass rod and the stopwatch is started. 4. 2 cm3 of the mixture from test tube is immediately poured into two separate test tubes.

The Benedict’s test and iodine test are carried out on them respectively. 5. Step 4 is repeated after 20 minutes. 6. The results of the experiment are recorded in a table.

Results:

Food testAt the beginning of the activity At the end of the activity

Observation Inference Observation InferenceBenedict’s test Blue solution Glucose

absentBrick-red precipitate

Glucose present

Iodine test Blue-black solution Starch present Brown solution Starch absent

Conclusion: Starch is converted by salivary amylase to sugar.

http://resources.schoolscience.co.uk/ABPI/digestion/digest6.htmlMore information on the absorption of digested food can be found here.

Digested food is absorbed through the walls of the small intestines into the blood capillaries due to diffusion.

The internal wall of the small intestine is covered with tiny finger-like projections called villi. The villi increase the surface contact with the digested food. The food can be absorbed at a higher rate.



Structure of the human heart

An adult human’s heart is about the size of a clenched fist. The heart lies in the chest between the two lungs. The heart is a muscular organ with walls made of cardiac muscles. The coronary arteries supply nutrients and oxygen to the muscles while the coronary veins remove wastes from the muscles.

The heart is divided into four chambers. The two upper chambers are called auricles or atria (singular: atrium) and the two lower chambers are called ventricles. The septum divides the heart into the right and left halves.

To lungsAorta

To head and body

From head and body

From trunkand legs

From lungs

Superiorvena cava

Semilunarvalves Pulmonary veins

Bicuspid valveTricuspid valve

Septum

Pulmonary artery

Interiorvena cava

Oxygenated bloodDeoxygenated blood

Key :

Left auricle

Left ventricle

Right auricle

Right ventricle

The structure of the human heart

The auricles have thinner walls than the ventricles. When the auricles contract, blood is pushed into the ventricles below. The left ventricle has a much thicker muscular wall than the right ventricle.

Our heart


44 Science Mathayom 2 Chapter 2 Systems in Humans and Animals PB

The table below shows the comparison of the mechanisms of inhalation and exhalation.Inhalation Exhalation

• Diaphragm muscles contract.• Diaphragm flattens out.

• Diaphragm muscles relax.• Diaphragm arches upwards.

• Intercostal muscles contract. • Intercostal muscles relax.• Ribcage moves upwards and outwards. • Ribcage moves downwards and inwards.• Volume of thoracic cavity increases. • Volume of thoracic cavity decreases.• Air pressure in the lungs decreases. • Air pressure in the lungs increases.• Air flows into the lungs. • Air is forced out of the lungs.

Comparison of the mechanisms of inhalation and exhalation

Investigating the relationship between the air pressure in the thoracic cavity and the process of inhalation and exhalation

Materials/apparatus: Elastic sheet, balloons, glass jar, Y-tube and cork

Procedure: 1. A model is set up as shown in the figure on the right. 2. The elastic sheet is pulled down. Are there any changes

to the size of the balloons? 3. The elastic sheet is pushed up. Are there any changes

to the size of the balloons? 4. All observations are recorded.

Observation: 1. The balloons inflated when the rubber sheet is

pulled down. 2. The balloons deflated when the rubber sheet is pushed up.

Discussion:The table below shows the parts of the human respiratory system which are represented by the material/apparatus in the model.Material/apparatus Glass jar Y-tube Balloons Elastic sheetRespiratory system Thoracic cavity Respiratory tract Lungs Diaphragm

Conclusion: 1. When the elastic sheet is pulled down, the pressure inside the glass jar decreases. Air

from outside enters the balloons. 2. When the elastic sheet is pushed up, the pressure inside the glass jar increases. Air is

forced out of the balloons.

Balloon

Glass jar

Elastic sheet

Y-tube

Cork



2.7 Excretory System in Humans

Metabolism refers to all the chemical processes that take place in the body. Metabolism may result in the production of waste products which are often toxic.

The elimination of the metabolic waste products from the body is called excretion. This is done by the excretory organs.

Defecation is not excretion because feces contain undigested food which has not been absorbed into the cells or taken part in metabolism.

Skin(a) The skin not only protects our body, but is also an

excretory organ.(b) The skin has many sweat glands which produce sweat

when the body is hot.(c) Each sweat gland is a long coiled tube. The sweat

gland leads to a sweat duct which opens on the skin surface as a sweat pore.

(d) Sweat is extracted from the blood capillaries surrounding the sweat glands.

(e) Sweat contains water, mineral salts and urea.

Layer of dead skin

Sweat pore

Sweet gland

Blood vessels

Epidermis

Dermis

Fatty layer

Hair

Structure of human skin

Secretion is a form of excretion.

Secretion is not a form of excretion because secretion produces useful substances from cells. The addition of digestive juices to food materials is an example of secretion.

The skin helps to remove excess water from the body.

Sweat from the skin not only removes excess water but also cools the body. The kidneys remove excess water.

Not all mammals sweat. Dogs, for example, have sweat glands only on the pads of their paws and they cool themselves mainly by panting. When a dog pants, water evaporates from the mouth and tongue.

http://qldscienceteachers.tripod.com/junior/biology/excretory.html



Different animals use different organs to excrete carbon dioxide. The table below shows a summary of the excretory organs used.

Animal Excretory organs to remove carbon dioxide

Fish Gills

Cow Lungs

Bird Lungs

Frog Lungs and skin

Crocodile Lungs

2.8Q1. What excretory organs do birds and frogs use to remove the waste

products from their blood?

In animals

Inhalation

In animals

In animals

In humans

Circulatory system

Respiratory system

Digestive system

Excretory system

In humans

Exhalation

HeartOrgans

Excretory organs

Absorption

Excretory products

Blood vesselsDefecationEnd products

Structure Breathing mechanism

Transportation of oxygen

Systems

In humans In humans In animals



Fill in the blanks with the given words.

abomasum crops ventricles lungs frogs artery digestionheart atria increases upwards gills lungs wasteduodenum higher vein capillary downwards decreases tracheaalveolus pushes kidneys enzymes gas exchange excretion diffuses

1. is the breakdown of large food molecules into smaller soluble molecules that can be absorbed by the body.

2. This is the pathway for the food that enters our mouth:

Mouth → Esophagus → Stomach

↓

Anus ← Largeintestine

← Smallintestine

←

3. Digestive are protein substances that act as catalysts to speed up the digestion process.

4. A cow has four chambers – rumen, reticulum, omasum and

, in the stomach.

5. Birds have to store their food and gizzards to grind hard food.

6. Human’s circulatory system is made up of the , blood and network of blood vessels.

7. Our heart has four chambers, namely (at the upper part) and (at the lower part).

8. There are three types of blood vessels, namely• – carries blood

away from the heart to other parts of the body and has no valve.

• – carries blood to the heart from other parts of the body and contains valves.

• – the finest blood vessel that connects the artery and vein

9. The pathway for air entering our lungs:

Nose → → Bronchus

→ Bronchiole → Alveolus

10. has a large surface area, very thin wall and moist surface to assist in the exchange of gases.

11. During inhalation, air enters the lungs.• Theribcagemoves

and outwards and the diaphragm flattens.

• The volume of the thorax and its pressure

decreases.• The higher external atmospheric

pressure air into the lungs.

12. During exhalation, air leaves the lungs.• Theribcagemoves

and inwards and the diaphragm arches upwards.

• The volume of the thorax and its pressure

increases.• The pressure in the

lungs pushes air out of the lungs.

13. Oxygen in the alveolus into the blood capillaries surrounding the alveolus. Carbon dioxide from the blood capillaries diffuses into the alveolus.


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