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Nutrition in Plants & Animals

BACKGROUND INFORMATION

In the topic Introduction to Biology you learnt that plants make their own food through the process of photosynthesis. This is one of the most important processes in nature. It ensures the survival of both plants and animals. In this lesson you are going to learn how this process takes place and the structures involved. You will also learn about the conditions that affect photosynthesis.

 


 

LESSON OBJECTIVES

By the end of this lesson you should be able to:

  • Define photosynthesis
  • State the importance of photosynthesis in nature
  • Describe the structure of the leaf
  • Describe structure and function of the chloroplast
  • Describe the process of photosynthesis
  • Explain at least three factors affecting photosynthesis
  • Explain at least five ways in which the leaf is adapted for photosynthesis.


 

Nutrition

In this topic you will learn about nutrition in plants and animals

 

 


 


 

Activity



Q2.  List the requirements for the process to take place .type and check the answer.
Answer-

  • Water
  • Carbon dioxide
  • Light

Photosynthesis

Plants are said to be autotrophic in nature. This means that they make their own food. They do not depend on other organisms for food. The process by which plants manufacture their own food is reffered to as photosynthesis. In the process Carbon (IV) Oxide and water react using sunlight.

The light energy from the sun is trapped by the green colouring matter in the plants called chlorophyll.

 

 

External Structure of the Leaf

Photosynthesis takes place mainly in the leaves. The figure shows external parts of a leaf.

ACTIVITY



In the illustration of the internal structure of the leaf, identify the three types of photosynthetic cells. Type your answers in the boxes.

 
 
 

Correct answers.

  • Palisade cell
  • Spongy mesophyll cell
  • Guard cells

Internal Structure of the Leaf

The leaf's internal structure is adapted to maximise efficiency for photosynthesis. Study the illustrated transverse section of the leaf.


A thin transverse-section of the leaf observed through the light microscope would appear as shown in the illustration below.

Transverse Section through a Leaf

 

 

 

 


The process of photosynthesis takes place in structures called chloroplasts. Chloroplasts are disc-like structures found in the cytoplasm of photosynthetic cells.

L.S of a chloroplast


Chloroplasts in a palisade cell

 

ACTIVITY


 

What makes the grana appear green?

 

Type your answer in the box  

Answer

Chlorophyll

The grana contain chlorophyll molecules which trap light energy from the sun.

Structure of a Chloroplast

The illustrations below outline the location and structure of chloroplasts.


 

The Grana


The grana are membraneous structures containing chlorophyll molecules on their surface. These trap light energy from the sun.

The Stroma

The stroma is the fluid matrix in which the grana are suspended.

Stages of Photosynthesis

The process of photosynthesis takes place in the chloroplast in two distinct stages: Light stage and Dark stage. In the Light stage light energy is used to break water in the leaves into Hydrogen ions and Oxygen as illustrated.




 

Formation of Hydrogen ions and Oxygen from water during the Light stage of photosynthesis


Light Stage

This is a light-dependent stage. It occurs in the granum of the chloroplast.
In this stage light energy from the sun is absorbed by chlorophyll molecules.
Light energy is used to split water molecules into Hydrogen atoms and Oxygen gas is produced. The process of splitting water molecules is called photolysis.

Some of the light energy absorbed by chlorophyll molecules is used to form an energy-rich compound called Adenosine Triphosphate (ATP). Oxygen is released into the atmosphere as a by-product.

Dark Stage

During the dark stage Hydrogen atoms and ATP from the light stage enter the stroma of the chloroplast. Hydrogen atoms reduce Carbon (IV) Oxide from the atmosphere to form glucose. Energy is from ATP.


This process is called Carbon dioxide fixation. Water is produced as a by-product.


.

Testing for Starch in a Leaf

The simple sugar formed during photosynthesis is converted into starch and stored in the leaves. The presence of starch in the leaf is evidence that photosynthesis has taken place. Test for starch in a leaf can be done through a simple procedure.Materials and Apparatus requred for this process include:


  • A leafy potted plant which has been kept in the dark for at least 5 hours
  • Droppers, Beakers, Source of heat, Boiling tubes, Forceps, a tripod stand,
    Methylated spirit
    ,
    Iodine solution
    ,
    White tile

  • Droppers

Beaker with water

Source of heat

Boiling tube

Forceps

Tripod stand

Products of Photosynthesis
Activity



Drag and drop each of the products of photosynthesis listed below into the correct stage of photosynthesis.


 
 

Answers.
Light stage

  •  Hydrogen atoms
  • Oxygen
  • ATP

Dark Stage

  • Simple sugar
  • Water

Procedure for Testing for Starch

  • Boil water in a beaker
  • Detach one leaf from the potted plant
  • Dip the leaf in the boiling water for three minutes. This stops chemical activity/photosynthesis in the leaf
  • Remove the leaf from the hot water using forceps
  • Put the leaf in the boiling tube containing methylated spirit and stand the tube in the beaker containing boiling water until all the green colour has been dissolved out of the leaf
  • Remove the leaf from the methylated spirit and dip it in warm water. This softens the leaf
  • Spread the leaf on the white tile
  • Add drops of iodine to cover the whole leaf. Record your observation

Activity

1. Match the procedure below to the reasons why they were carried out.

Procedure Reason

Use leaf that had been exposed to light. To soften leaf
Dropping the leaf into boiling water.       To remove chlorophyll
Boiling the leaf in methylated spirit           To kill the leaf

2. Why was it necessary to boil the leaf indirectly in the methylated spirit? Type and check for the answer.
Answer: Methylated spirit is highly inflammable.

3. Observe the following illustration on photosynthesis before the setup. The plant had been kept in the dark for 24hrs.

Why was the plant kept in the dark for 24hrs?

Insert a potted leaf in which two leaves are treated as follows: one is put in a conical flask containing Sodium hydroxide pellets and another is covered with a strip of Aluminium foil.

This setup was exposed to light for five hours.

To absorb water

A     


To keep off carbon dioxide

B


To manufacture starch

C      


To remove starch

        
D
Answer D

  1. What role is played by the Aluminium foil?

 


To let light into leaf

         A

To prevent light reaching leaf

         B          

To absorb light

         C   

To warm the leaf

         D     
Answer B

  1. Why was sodium hydroxide included in the conical flask?

  


To absorb carbon dioxide

       A        

To absorb oxygen

  B        

To add nutrients

       C

To absorb water

      

4. Leaf A, B and C were tested for starch .Drag and drop the correct results to the matching leaf.

 

 
Leaf A    

 

Leaf B       

 

  
Leaf C 


No starch

a    

Starch present in the whole leaf

b       


Starch present in some parts of the leaf

  
        

 

Conclusion from starch test:
A leaf in which photosynthesis took place would turn blue black. This color indicates the presence of starch in the leaf. Starch would have been formed from the sugar produced during photosynthesis.


In the absence of starch there would be no color change.

a) Light Intensity

Activity



Drag the button along the horizontal axis in the illustration below. Note and record your observation in the box.

Insert a graph of rate of photosynthesis against light intensity.
Animate the curve so that as the button moves along the horizontal axis. it rises up to the optimum point when it levels off.

Correct Observation.
As the light intensity increases the rate of photosynthesis increases up to optimum

Why does the curve level off after the optimum point? Type your answer in the box and check for correct answer.

 

Correct answer.
Another factor such as CO2   concentration must be limiting the rate of photosynthesis.

 

Factors Influencing the Rate of Photosynthesis

The rate of photosynthesis is affected by Light intensity, Carbon dioxide concentration and temperature.

 

Effect of Carbon (IV) Oxide on the rate of Photosynthesis

The graph indicates how the rate of photosynthesis changes with increase in Carbon (IV) Oxide. Note that the rate increases until a maximum beyond which further increase has no effect. At this time other factors other than Carbon dioxide become limiting.

Effect of Carbon (IV) Oxide concentration on the rate of photosynthesis

Effect of Temperature on the Rate of Photosynthesis

The rate of photosynthesis increases with increase in temperature up to an optimum temperature of between 30 to 40 degrees centigrade. Any further increase in temperature leads to a slow down in the process. The process stops at 60 degrees. This is because photosynthesis s controlled by enzymes. At low temperatures enzymes are inactive. They are most active at between 35 and 38 degrees Centigrade but are denatured at temperatures above 40 degrees Centigrade.

Activity

b) Carbon Dioxide Concentration
Drag the button on the horizontal axis in the illustration below .note and record your observation in the box.

 

Insert a graph of rate of photosynthesis against carbon dioxide concentration. Animate the curve so that as the button moves along the horizontal axis, it rises until the optimum and then levels out .

Observation.
As the carbon dioxide concentration increases the rate of photosynthesis increases up to optimum

Why does the curve level off after the optimum point? Type and check for the answer.

 

Answer


Another factor such as temperature must be limiting the process.

c) Temperature

Activity

Drag the button along the horizontal axis in the illustration and record your observation in the text box.

 

Observation
As temperature increases the rate of photosynthesis increases up to optimum it slows down and then stops.

Why does the rate of photosynthesis slow down and finally drop as temperature is increased? Type your answer and check for the correct answer.

 

Answer.

It slows down as the enzymes are being denatured.


Drops when all enzymes have been denatured.

Adaptation of the Leaf to Photosynthesis

The leaf is adapted for photosynthesis. Adaptations of the leaf increase efficiency of this process.

Adaptive features of the leaf include:

Broad flat lamina to provide large surface area for absorption of carbon dioxide and sunlight.

Thin, to allow light to pass through a short distance to reach photosynthetic cells.

Has stomata, through which Carbon dioxide diffuses into the leaf.

Extensive veinsto conduct water and mineral salts to photosynthetic cells and carry manufactured food to other parts of the plant.

Large air spaces in the spongy mesophyll to allow gases to circulate easily.

Regular arrangement of leaves on the stem (leaf mosaic) minimizes overlapping and overshadowing. This allows maximum exposure of the leaf to light.

The palisade cells have more chloroplasts than the spongy mesophyll cells. They are located on the upper surface of the leaf to trap maximum light.

 

Leaf mosaic on a plant

 

 

TS of leaf showing chloroplasts in palisade and spongy mesophyll cells.

BACKGROUND INFORMATION

In Primary School, you learnt about digestion or breakdown of food into simple substances that can be absorbed into the body. The chemical compounds used to break down the food into simple substances are called enzymes. In this lesson you are going to learn about enzymes.

ACTIVITY

You have already learnt about carbohydrates, proteins and lipids.
State the building blocks of these compounds:

 

Carbohydrate 

 

Proteins

 

Lipids  

LESSON OBJECTIVES

By the end of this lesson you should be able to:

  • Define an enzyme
  • State at least four properties of enzymes
  • Explain at least four factors that affect enzyme-controlled reactions.

NUTRITION IN ANIMALS

Animals require food materials such as carbohydrates, proteins and fats. From these materials the organism extracts nutrients which are the building blocks of the food materials.

To obtain these building blocks from the large molecules, enzymes are required.
Enzymes are organic biological catalysts. A catalyst is a substance that speeds up the rate of chemical reactions. Enzymes are therefore necessary because in their absence chemical reactions in living organisms would be too slow to sustain life.



Insert an illustration of a reaction with enzyme and one without enzyme as shown below.
 

    

 
 

Large molecule       Small molecules

Animate such that the arrow moves slowly along with the small molecules.

 

    

 
 
 
 
 

Large molecule       Small molecules

Animate such that the movement of the arrow and the formation of small molecules is very fast.

PROPERTIES OF ENZYMES

1.Enzymes are protein in nature. Any factor that affects a protein will therefore affect an enzyme.

2.Enzymes are specific to the reactions they catalyse i.e. a given enzyme will only act on a particular type of substrate, for example, an enzyme that breaks down a protein cannot break down a carbohydrate.

Insert an illustration to show two different molecules in the presence of a particular enzyme.
Reaction 1.

Animate the reaction to show the enzyme breaking down the substrate and the formation of product. This illustration should be raised and indicate that enzyme is not used up in the reaction.
Reaction 2.

Animate to show enzyme knocking on the substrate molecule.

3. Enzymes are not used up in the reactions they catalyse. They remain unchanged and can be used repeatedly.

 

4.Many of the reactions they catalyse are
reversible.

 

Animate the illustration to show breakdown of substrate into products and enzyme recombining products back into substrate molecule.

 

Factors that Affect Enzyme-Controlled Reactions

Enzymes are protein in nature. They are therefore affected by various factors. Enzyme-controlled reactions are in turn influenced by factors that affect enzymes. Any factor that affects the enzyme affects the reaction as well. The following are factors that affect enzyme-controlled reactions:

  1. Temperature
  2. pH
  3. Substrate concentration
  4. Enzyme concentration
  5. Co-factors and Co-enzymes
  6. Enzyme inhibitors.

ACTIVITY

Effect of temperature on enzyme controlled reactions.

Drag the button along the horizontal axis in the illustration below. Record your observation in the box. Check for the answer

 

Answer
As the temp increases the rate of reaction increases up to 35oC then drops at 60oC.

From the graph, identify the temperature at which the rate of reaction is maximum. Type and check the answer.

Correct answer: 35oC

This is the optimum temperature for the enzyme i.e. the temperature at which the enzyme works best.
The optimum temperature varies for different enzymes.
 

Describe the shape of the graph between;
a) 0- 10*C.Type and check for the answer
 

Answer
Rate of reaction is slow.
This temperature is too low and the enzymes are therefore inactive.

b) 10-35*C. Type and check for the answer
 

Answer
Rate of reaction increases rapidly.
This is because the enzymes are activated as the temperature rises up to the optimum.

c) 35-60*C. Type and check for the answer
Answer
The rate of reaction decreases and stops altogether at 60*C .


This is because above the optimum temperature, enzymes get denatured and permanently destroyed at 60*C.

Temperature

Enzymes work best within a narrow range of temperature. Each enzyme has a specific optimum temperature at which it has maximum effect on the rate of reaction.

Carry out the activity provided to investigate the effect of temperature on an enzyme-controlled reactions.

 

ACTIVITY

Drag button A along the horizontal axis in the illustration below .Record the optimum pH.Check for the answer.
 

Answer:

Optimum pH is 2.0
 

Drag button B along the horizontal axis in the illustration below. Record the optimum pH.check for the answer.
 

Answer:

Optimum pH is 8.0


Insert two curves on the same axis such that when a student drags button A along the horizontal axis, it describes curve for enzyme A. when he drags button B it describes curve for enzyme B. Use different colours for curve A and B.

If the pH increases beyond the optimum for a particular enzyme, the enzyme becomes denatured.
For example, enzyme A which work best at pH 2 will get denatured at pH 6

pH

This is the degree of alkalinity or acidity of a solution. pH scale ranges from 0-14.

Enzymes are protein in nature hence they are sensitive to changes in pH. Some work best in acidic medium while others work best in alkaline medium.

ACTIVITY

Drag the button along the horizontal axis in the illustration below showing the rate of reaction against substrate concentration. Record your observation in the box. Check for the answer.
 


Answer
As the substrate concentration increases, the rate of reaction increases up to a certain point and then levels off.
 


Explanation (voiced together with text)
Increasing the substrate concentration increases the number of molecules being acted on by the enzymes present. The graph levels off because all the active sites of the enzyme are occupied. It is the enzymes concentration that is now limiting the rate of reaction.

Insert a curve of rate of reaction against substrate concentration. Animate button to dragged horizontally by learner.

Substrate concentration

Increasing substrate concentration increases the number of molecules being acted on by the enzyme. This therefore increases the rate of reaction up to a maximum level as illustrated in the activity provided. Carry out the activity.


You notice that the rate of enzyme controlled reaction changes with variation in the substrate concentration. The reaction increases with increase in the amount of the substrate up to an optimum level when no further increase in reaction occurs. This is when all enzyme active sites have been occuppied by substrate molecules.

The graph shows how the rate of enzyme controlled reactions varies with substrate concentration.

Enzyme Concentration

The rate of reaction increases with increase in the enzyme concentration. This remains true as long as the substrate concentration is in the excess of the enzyme.

Enzyme Concentration


Increasing enzyme concentration increases the number of active sites available for substrate molecules. This therefore increases the rate of reaction until when all substrate molecules have reacted and the reaction stopped.

Enzyme Concentration

Co-factors and Coenzymes

Co-factors increase the rate of enzyme-controlled reactions. This is because co-factors make enzymes more active. Organic co-factors are known as co-enzymes while inorganic ones are mettalic ions such as Copper, Iron, Magnessium and Zinc.

Organic co-factors (coenzymes) include vitamins.
 


 

Inhibitors

An inhibitor is a chemical substance that blocks the activity of an enzyme, thereby reducing the rate of reaction.
The inhibitor competes with the normal substrate for the active site of the enzyme.

Some inhibitors temporarily occupy the enzyme active sites while others do so permanently.
Examples of inhibitors include poisons such as Cyanide, Mercury, Arsenic and compounds of Silver, which permanently occupy the active sites, rendering the enzyme unavailable for the reaction.
 

 

ACTIVITY
AIM:
To investigate the presence of enzyme catalase in a living tissue.
 

Requirements:

  • 3 pieces of 1cm3of fresh mammalian liver

  • 10ml hydrogen peroxide

  • Test tubes


  • Forceps

Forceps


  • Scalpel


  • Mortar and pestle


  • Fine sand


  • Source of heat

  • Wooden splints

  • Labels

Enzymes in Living Tissues

Catalase is an enzyme present in living tissues of plants and animals.
Its role in living tissues is to break down hydrogen peroxide (H2O2) produced during chemical reactions in cells.
Hydrogen peroxide is a highly toxic chemical substance which should not be allowed to accumulate in the tissues.  Enzyme catalase renders it harmless by breaking it down into water and oxygen.
 

The chemical equation below summarizes this process.



Enzyme Catalase

2H2O2.........................................................       2H2O+    O2

Procedure

  1. Label the three test tubes A, B and C.
  2. Measure 2cm3 of hydrogen peroxide and put in each of the test tubes.
  3. Pick one piece of liver and drop it into test tube A. Record your observation.

Observation:
Bubbles are formed

  1. Grind the second piece of liver in a mortar containing a little sand.
  2. Place the crushed piece of liver into test tube B. Immediately introduce a glowing splint into the mouth of the test tube.
  3. Record your observation.

GAME

Observation.
Vigorous reaction producing a lot of bubbles. Glowing splint relights. This shows that the gas produced is oxygen. The reaction is more vigorous because crushing released more enzymes from the liver tissue.
Boil the third piece of liver in a test tube for five minutes. Place it in test tube C. Record your observation.

Observation
No reaction occurs
Explanation: boiling denatured the enzyme catalase.

Animate the following processes for the respective reactions.

  1. Reaction A
  2. Reaction B
  3. Reaction C

BACKGROUND INFORMATION

In Primary school you learnt about the structure and functions of different types of teeth in human beings. In this lesson you will learn more about how these teeth are modified to carry out their functions efficiently. You will also learn about teeth of other mammals in relation to their different modes of feeding.

ACTIVITY

Name four types of heterotrophic nutrition. Type your answers in the text boxes and check for the correct answer.
 

LESSON OBJECTIVES

By the end of this lesson you should be able to:

  1. Describe the dentition of a named carnivorous, herbivorous, and omnivorous mammal.
  2. Relate various types of teeth in mammals to their feeding habits.
  3. Describe the internal structure of a mammalian tooth.
  4. Describe at least two dental diseases.

To insert Herbivore, Carnivore and Omnivore

Nutrition in Animals

In this section you are going to learn about feeding in animals.

A skull of a rhinocerus showing upper and lower jaws.

ACTIVITY

Name four types of mammalin teeth.

Type your answers in the text boxes and check for the answer.
 

        
Correct answers
Incisor
Canine
Pre-molar
Molar

(Accompany each tooth with its respective illustration (photo/ diagram)

Introduction to Nutrition in Animals

Animals carry out heterotrophic nutrition. These organisms have organs and structures which are specialised for breakdown of the complex food molecules taken in into simple absorbable and usable forms.

QUIZ

I. Identify the modes of feeding of the mammal whose dental formulae are shown below. Type the answer in the text box.

  1. i2/2 c1/1 pm2/2 m3/3= 32
  2. i3/3 c1/1 pm4/4 m2/3= 42
  3. i0/3 c0/1 pm3/3 m3/3 = 32

II. State the functions of the following
a) Carnassial teeth in a dog

b) Diastema in a sheep

III. Identify the type of mammalian tooth shown below

     

Name the parts labeled A, Band C

IV) The illustration below shows the internal structure of the above tooth.
       P
 



 

      Q

       R

      S
       

    1. Name the parts labeled P, Q, R and S
    2. Which of the labeled parts contains a higher content of calcium phosphate?

 



 

V) Suggest two ways of preventing periodontal diseases.
 



 

   

Answers
1a) (i) Omnivore
(ii) Carnivore
(iii) Herbivore

(b) (i) Slicing off pieces of teeth
Crushing bones

(ii)  Provides space for the tongue to turn grass during chewing.

2. (a) (i) Canine
          (ii) A- Crown
     B- Neck
            C- Root
(b) (i) P- Enamel
     Q- Dentine
      R- Pulp cavity
      S- Root

    1. P

     3 Regular cleaning of gums
        Regular visits to the dentist

        
Eating foods rich in vitamins A, C and D

Holozoic Nutrition


In holozoic nutrition solid complex food substances are ingested, digested and assimilated in the bodies of animals.
The ingested food is broken down mechanically by teeth. The type, arrangement and number of teeth in a mammal is refered to as dentition.
The teeth are arranged in groups to occupy specific positions in the jaw.
The dentition determines the mode of feeding that is whether herbivorous, carnivorous or omnivorous.

ACTIVITY

Insert an animated illustration of the skull of a carnivore showing both upper and lower jaws with teeth intact. The illustration should have the teeth labeled. As it rotates the teeth should be seen from all angles.

Observe the illustration and describe the shape of the labeled teeth.

Answers

  • Incisors are chisel shaped, small. They are used for cutting, gripping and stripping flesh from the bones.
  • Canines are long, pointed and curved .They are used for holding, piercing and killing the prey and tearing flesh.
  • Carnassial teeth are large, with sharp cutting edges. They are the last upper pre molar and the first lower molar modified for slicing off pieces of flesh from bones and crushing bones.
  • The rest of the molars and premolars are small in size because there is little chewing of food.
        • Count the number of each type of teeth in the upper and lower jaws. Record and check for the answer.
        • What is the total number of teeth in jaws of the dog?
 

Incisors

canines

premolars

molars

Total

Upper jaw

         

Lower jaw

         

Total number of teeth

         
 

incisors

canines

premolars

molars

Total

Upper jaw

6

2

8

4

20

Lower jaw

6

2

8

6

22

Total number of teeth

12

4

16

10

42

Dentition of a Carnivore
Teeth of a carnivore are adapted for cutting, holding, tearing, biting and piercing.

Carnivores feed on flesh. Examples of carnivores are dog, cat, lion, cheetah and leopard.


A Lion


A Leopard

Dental Formula

The number, type and position of teeth in the jaw of a mammal are described by the dental formula. The dental formula of a carnivore is related to its mode of feeding. The number of teeth recorded represents half the total teeth in the upper and lower jaws. The names of types of teeth are abbreviated as follows; incisors as i, canines as c, premolars as pm, and molar as m.

For a dog, a carnivore the dental formula is i 3/3, c 1/1 pm 4/4 m 2/3=42 The total number of teeth is obtained by multiplying teeth in each half jaw by two.

ACTIVITY

Give three examples of
Grazers

Browsers



Correct answer
Grazers: cow, sheep, donkey, zebra
Browsers: goat, gazelle, antelopes, giraffe

Observe the illustration of the skull of a sheep.



Insert an animated skull of a herbivore (sheep) showing both lower and upper jaws with teeth intact. The following structures are to be labeled: incisor, canine, premolars, molars horny pad, and diastema. Let the illustration rotated to be seen from all angles.
 

Describe the shape of the labeled teeth. Type and check for the answer.
 

Incisor


Canine

 




Premolar


Molars

Answers
Incisors are flat chisel shaped with sharp edges for cutting and biting vegetation. They have one root.
NB: Put an illustration of a complete labeled incisor tooth.
 

Canines are sharp pointed and reduced in size. They also have one root.
NB: Insert an illustration of a complete labeled canine of a herbivore
Premolars and molars are large with broad surfaces. The surfaces have ridges and cusps for grinding vegetation.
Premolars have two roots; molars have three roots. The roots are open. The enamel in the crown is open to allow for continuous growth of tooth to replace that worn out by grinding.
NB: Insert an illustration of a labeled molar tooth of an herbivore.

Suggest the functions of the following structures

  1. Diastema
  2. Horny pad

Answers

  1. Diastema- provides space for the tongue to turn the grass. This facilitates effective chewing
  2. The horny pad serves as a surface against which vegetation is pressed and cut by the incisors in the lower jaw.

Count the total number of each type of teeth in each jaw. Record.

Answer.

 

Incisors

canines

premolars

molars

Total

Upper jaw

         

Lower jaw

         

Total number of teeth

         

Answers

 

incisor

canines

premolars

molars

Total

Upper jaw

0

0

6

6

12

Lower jaw

6

2

6

6

20

Total number of teeth

6

2

12

12

32

Work out the dental formula of a sheep. Type and check for the answer
Dental formula 

Answer


I0/3 c0/3 pm3/3 m3/3=32

Dentition of a Herbivore

Herbivore teeth are adapted for holding, cutting, crushing and grinding

Herbivores feed exclusively on vegetation. Their mode of feeding is referred to as herbivorous. Herbivores that feed on grass are called grazers. Those that feed on twigs, shrubs and herbs are called browsers.

 

 

 

ACTIVITY

Observe the illustration of a human skull

Insert an illustration of a man showing both upper and lower jaws.

The teeth should be labeled. The skull should be animated and slowly rotate to be viewed from all directions.

Describe the shape of the labeled teeth. Type and check for the answer.
Incisor

Canine

Premolar

Molar

Answers
Incisors are flat, chisel shaped with sharp edges for cutting and biting. They have one root.
NB: Insert an illustration of a human tooth. Rotate to be seen from all angles.


Canines are conical with sharp pointed edges for tearing. They have one root.
NB: Insert a labeled illustration of a canine tooth. Animate to rotate.
 

Premolars are large with broad surfaces. The surfaces have cusps and ridges for grinding food. They have two roots.
NB: Insert a labeled illustration of a human premolar. Rotate.

Molars are large with broad surfaces. They have more cusps and ridges for grinding food. Molars have three roots.
 

NB: Insert a labeled illustration of a human molar tooth. Rotate.
Count the total number of each type of teeth in each jaw. Record and check the answer.

 

incisor

canines

premolars

molars

Total

Upper jaw

         

Lower jaw

         

Total number of teeth

         
 

incisor

canines

premolars

molars

Total

Upper jaw

4

2

4

6

16

Lower jaw

4

2

4

6

16

Total number of teeth

8

4

8

12

32

Work out the dental formula of a human being. Type and check for the answer.

Answer


I2/2 c1/1 pm2/2 m3/3 =32

Dentition of an Omnivore

Omnivores feed on both flesh and vegetable matter. Their teeth are adapted for this type of food. Examples of omnivores are human being, gorilla and pig.

Human jaws

 

Human jaws 2

Human Jaw

 

 

Gorrilla jaws

Gorrilla jaws 2

Gorrilla Jaw

 

 

 

ACTIVITY

Count the total number of each type of teeth in each jaw. Record and check the answer.

 

incisor

canines

premolars

molars

Total

Upper jaw

         

Lower jaw

         

Total number of teeth

         
 

incisor

canines

premolars

molars

Total

Upper jaw

4

2

4

6

16

Lower jaw

4

2

4

6

16

Total number of teeth

8

4

8

12

32

Work out the dental formula of a human being. Type and check for the answer.

Correct answer
i2/2 c1/1 pm2/2 m3/3 =32

Dental Formula of an omnivore

Dental formula of an omnivore is related to mode of feeding as well as the species under consideration.

Omnivores feed on both flesh and vegetation. The mode of feeding is called omnivorous. These have all their incisors, canines, premolars and molars well developed.

Structure of Teeth

These animations show the external structure of the four types of teeth in man, that is, incisors, canines, premolars and molars.

 

 

 


This illustration shows the Internal Structure of a Molar Tooth


 

Enamel: Outermost non living material covering the crown. It is made up of calcium and calcium phosphate. It is hard, and protects the inner delicate parts of the tooth and to provide a surface suitable for cutting and chewing food.

Dentine: It is found under the enamel. It is a living part, containing cytoplasmic strands. It is hard and bone-like but softer than the enamel. It gives rise to the enamel.

Pulp cavity: Contains blood vessels and nerve endings. The blood vessels provide nutrients to the living tissues and remove waste products. The nerves detect heat and pain sensations or stimuli.

Cement: It is spongy material made of calcium. It fixes the tooth to the socket in the jaw bone.

ACTIVITY

Q. Suggest four ways of preventing dental diseases
 

Answers

  • Regular cleaning and brushing of teeth
  • Avoid too much sugary foods
  • Eating hard foods such as raw carrots, cassava, yams, sugarcane
  • Eating foods rich in calcium phosphates and vitamins A,C, and D
  • Using teeth for their proper purpose. Do not use to open bottles
  • Regular visits to the dentist.

Dental Diseases
The two common dental disorders in humans are dental carries and periodontal disease:

Dental carries

This is an infection of the tooth itself. It results into tooth decay seen as cavities in the tooth. The photos show teeth with this kind of problem.

Periodontal Diseases: This is inflamation of the gums due to bacterial infection.The gums become soft and swollen. e.g.Gingivitis.

Healthy Gums

Infected gums

Moderate Gingivitis

Advanced Gingivitis

Causes of Dental Carries

Dental carries are cavities in teeth and are brought about by destruction of the hard tissue of the tooth. They may be due to eating too many sugary foods, not eating relatively hard foods and not cleaning teeth well

Too many sugary foods.

 

Accumulation of sugary food on the tooth surface

 

Progression of Dental Carries in a molar tooth due to accumulation of sugary foods.

Not eating hard foods such as sugarcane.

Lack of calcium in the diet.

Insufficient vitamin D.

Poor cleaning of teeth.

Treatment and Control of Dental Carries

Dental carries can be controlled by:

  • Proper cleaning (brushing), especially before going to bed.

  • Filling in cavities that have developed.

  • Removing plaque from the enamel.

  • Root canal treatment.

  • Visiting the dentist at least once a year.


Avoiding too many sugary foods

Feeding on a balanced diet rich in all types of nutrients.

Eggs

Milk

 

Bananas

Periodontal Diseases

Periodontal diseases attack the gums and walls of the mouth cavity. The gums become soft and flabby, such that they are unable to support the teeth. The disease is characterized by the reddening of gums and, in severe cases, the presence of pus. The presence of pus in the gums is a condition called pyorrhea while bleeding of the gum is a condition called gingivitis.

Infected gums

 

 

 

Causes of Periodontal Diseases

Periodontal diseases may be caused by :

  • Lack of vitamins A and C in the diet
  • Not cleaning gums properly

 

 

 

Treatment and Control of Periodontal Diseases.

  • Eating a balanced diet

  • Proper cleaning of teeth.

    Brushing Teeth

    • Visiting a dentist at least once a year.

    BACKGROUND INFORMATION

    In primary school you learnt about the parts of the human digestive system (alimentary canal).

     

    Human Digestive System

    ACTIVITY

    Complete the table below by filling in the blank spaces



    Part of the alimentary canal

    Juice secreted

    Gland where made

    Enzyme in juice

    Substance acted upon by juice

    Products

    Mouth

    saliva

    a

    b

    Cooked starch

    c

    Stomach

    d

    Gastric gland

    e
    f

    Proteins
    caseinogens

    g

    Duodenum

    h

    Pancreases

    Typsin
    lipase

    Starch
    j
    k

    i
    Peptides
    m

    bile

    n

    o

    lipids

    Tiny fat droplets

    Ileum

    p

    Wall of the ileum

    Maltase
    q
    r

    s
    Sucrose
    lactose

    t
    Glucose + u
    Glucose +v

    Peptidase
    w

    x
    Emulsified fats

    y
    z

    2. The figure below is a part of the alimentary canal

    (a)
    (i) Which part of the alimentary canal is represented by the portion above?
    (ii) Give one reason for your answer in (a) (i) above
    (b) State two functions of the part of alimentary canal represented above

    3. Explain why enzymes pepsin and typsin are secreted as inactive pepsinogen and typsinogen respectively.
    4. Name the blood vessel that transport digested food from the ileum to the liver.
    5. What happens to absorbed glucose in the body?

    Answers
    1. a- salivary glands       b- salivary amylase
    c- Maltose   d- gastric juice
    e- Pepsin     f- rennin
    g- Peptides h- pancreatic juice
    i- Protein     k- lipids
    l-maltose     m- fatty acids and glycerol
    n- Liver        o- bile salts
    p- Intestinal juice           q- sucrase
    r- Lactase    s- maltose
    t- Glucose   u fructose
    v- Galactose       w lactase
    x- Peptides  y- amino acids
    z- Fatty acids and glycerol.

    2 (a) (i) ileum
    ii) Presence of villi
    (b) Digestion
         Absorption
    3. To prevent them from digesting the wall of the alimentary canal
    4. Hepatic portal vein
    5. Used to release energy
      Excess is converted into glycogen and stores in the liver.

    LESSON OBJECTIVES

    By the end of this lesson you should be able to:

    • Relate the structures of the human alimentary canal to their functions.
    • Describe the process of digestion.
    • Describe the process of absorption.

    Digestive System and Digestion in Humans

    Digestive system of humans


     


     

    ACTIVITY

    Label the parts of the human digestive system in the human digestive system in the illustration below by dragging and dropping at the respective labels.

    Insert an illustration of human digestive system

    Pancreas      Anus
    Small intestine     Mouth
    Oesophagus Liver
    Rectum        Large intestine
    Stomach       Salivary glands


    Gall bladder

    ACTIVITY

    Observe the illustration below and describe the movement of food along the esophagus. Type and check for the answer
     



     

    Observation


    Food moves in a wave like motion. This is due to rhythmic contraction and relaxation of muscles of the oesophagus. This movement is called peristalsis.

    Digestion

    Breakdown of large complex molecules of food materials into simple usable forms is known as digestion. Physical breakdown is done by teeth while enzymes chemically breakdown the food. You have learnt about the functions of enzymes and teeth respectively. You learned that enzymes speed up the rate of chemical reactions in the body, for example, break down of large complex molecules into simple, usable molecules. Much of the food a human being takes in (ingests) is made up of large complex molecules. It is first broken down physically by the teeth and then chemically by enzymes into simple and soluble molecules before it can be absorbed. Along the alimentary canal, enzymes chemically digest carbohydrates, proteins and lipids.

    ACTIVITY
     

    Mammalin Ileum

    From the illustration given above, suggest how the ileum is adapted for absorption of food.
    Type and check for the answer

    TEXT BOX

    Correct answers

    • Long, to provide large surface area for absorption.
    • Coiled, to slow down movement of food allowing more time for digestion to be complete and absorption to take place.
    • Inner surface has numerous villi and microvillus which increase surface area for absorption .
    • Thin epithelium (thin layer of cells), to allow rapid diffusion of digested food.
    • Dense network of blood capillaries, to facilitate absorption and transport of food.
    • Presence of lacteals in the villi for absorption of fatty acids and glycerol.

    Digestion in the Mouth

    Mastication is carried out in the mouth whereby food is physically broken in to small pieces using teeth.These small pieces can then be chemically digested by the help of enzymes in the mouth and along the digestive canal.


     

    Salivary glands secrete saliva which contains the following:

    • Enzyme salivary amylase (ptyalin). This enzyme breaks down cooked starch into maltose in a slightly alkaline pH.
    • Mucus which lubricates the food.
    • Water which is a medium for the enzyme to act in and to soften the food

    The tongue rolls the food into a bolus which can easily be swallowed.

    Swallowing

    During swallowing the epiglottis closes over the glottis thereby covering the air passage. The tongue then forces the bolus into the oesophagus.

    Peristalsis during swallowing of food

     

     

     

     

     

     

    Digestion in the Stomach

    The bolus of food enters the stomach through a muscular valve called cardiac sphincter. The arrival of food into the stomach stimulates the stomach wall to secrete the hormone gastrin.Gastrin stimulates gastric glands to secrete gastric juice. Gastric juice contains:


    Enzyme pepsin which is produced in an inactive form pepsinogen. Pepsin breaks down proteins into peptides.


    Enzyme rennin which converts soluble milk caseinogen into insoluble casein. This process is called coagulation. Casein is acted upon by pepsin to produce peptides


    Hydrochloric acid which (1)activates the inactive enzyme pepsinogen to active enzyme pepsin, (2)creates a suitable (acidic) pH for the action of the enzyme pepsin, (3)kills bacteria present in the food and (4)emulsifies fats into droplets.

    Mucus which forms a protective barrier to the stomach wall, against corrosion by hydrochloric acid and digestion by pepsin.

    Formation of Chyme in the Stomach

    Rhythmical contractions of the stomach churn the food into a semi- fluid state called chyme.

    Churning of Food in the Stomach

    Digestion in the Duodenum

    Chyme enters the duodenum and stimulates secretion of the hormone cholecystokinnin. This hormone in turn stimulates the pancreas to secret enzymes lipase, amylase and trypsin contained in pancreatic juice. The hormone also stimulates production of bile.

    The duodenum is the first part of the small intestine. Chyme is let into the duodenum in small amounts through the pyloric sphincter.

    The figure shows chyme entering the duodenum

    Arrival of food in the duodenum stimulates the secretion of the hormones secretin and cholecystokynin (CCK) from the wall of the duodenum.
    Secretin stimulates pancreas to release pancreatic juice into the duodenum.
    Cholecystokynin stimulates the gall bladder to release bile.

    Pancreatic juice contains three enzymes:

    • Pancreatic lipase which breaks down lipids into fatty acids and glycerol.
    • Pancreatic amylase which breaks down remaining undigested starch to maltose.
    • Typsin which breaks down proteins into peptides. This enzyme is secreted in an inactive form,trypsinogen. Enzyme enterokinase stimulates production of trypsinogen.

    Pancreatic juice also contains Sodium hydrogen carbonate which (i) neutralizes the acidic chyme and (ii) provides an alkaline medium for pancreatic enzymes.

    Bile contains bile salts which include sodium glycocholate and sodium trycocholate. The salts break down fats into tiny fat droplets to increase surface area for digestion. This process is called emulsification.

    Bile also provides an alkaline medium for the enzymes and neutralizes the acidic chyme.

     

    Digestion in the Ileum

    Entry of food in the ileum stimulates production of succus entericus, a juice which contains enzymes that complete digestion. The enzymes include Maltase which breaks down maltose to glucose. Sucrase which breaks down sucrose into glucose and fructose. Peptidase breaks down lipids into fatty acids and glycerol. Lactase which breaks down lactose to glucose and galactose. The completion of digestion results into a watery emulsion (mixture) called chyle from which the products of digestion are absorbed.

     

     

     

    Summary of Digestion in the Small Intestine


     

    Absorption of Digested Food

    Absorption is the process by which the soluble products of digestion pass through the wall of the ileum into the blood stream. This occurs mainly in the ileum.

    Coiled Human Ileum (Small Intestine)

    Section of Ileum Showing Villi

    Microscopic Section of Ileum Showing Villi

    Epithelial Cell Showing Microvilli

     

     

     

    Absorption and Transport of Digested Food at a villus

    The absorbed products of digestion are carried to the liver by hepatic portal vein.



     

    Assimilation

    Assimilation is the process by which the body uses up the absorbed products of digestion. From the liver the products of digestion are transported in the blood stream to the rest of the body. The different food substances are assimilated as follows: Glucose is oxidized to release energy. Excess glucose is converted into glycogen and stored in the liver.Fatty acids and glycerol are oxidized to release energy. Excess is converted into fats and stored under the skin. Amino acids are used in the synthesis of proteins for growth and repair of worn-out tissues. Excess amino acids are converted to urea and excreted in urine. These processes are illustrated next



    Assimilation of Glucose

    Assimilation of amino acids: Most amino acids are used to make proteins for the body in a process called protein synthesis

     

     

    Assimilation of Lipids

    Egestion


    Undigested materials are the materials that missed to be digested because they were not in the alimentay canal long enough. Indigestible food materials are those materials that can not be digested. Both the undigested and the indigestible materials are removed from the alimentary canal through the anus at intervals as faeces.


    Egestion is the terminology that refers to this removal of undigested and indigestible food materials from the body through the anus in form of feaces.
    As the undigested and indigestible materials pass through the colon, water is exclusively absorbed. This leaves faeces to come out as a semi-solid waste material.

    Egestion of undigested and indigestible materials as feaces


     

    The figure bellow illustrastes the summary of digestion. It also marks the end of our Form One lessons in Biology. Move the cursor along the alimentary canal to activate the processes in key sections.

    The End

    This is the end of our Form One Lessons.

    Test yourself using the exercises and quizzes provided at the start of each of the topics in these lessons to gauge your progress.

     

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