Class 7 Science

Chapter 11 – Transportation in Animals & Plants

Chapter Notes

 

The body of an organism requires nutrients and oxygen to carry out various life processes.

Waste products, produced due to the various functions inside the body also need to be transported and removed.

The term transport is defined as a life process in which a material is absorbed in one part or organ of an organism and is carried to other parts in its body.

In animal body, these functions are carried out by an internal transport system called as circulatory system.

Circulatory System

Circulatory system or blood circulatory system is the main transport system in human beings and animals.

It makes food, water and oxygen available to every parts of the body and helps in removing waste material (urea, CO₂, etc.).

The circulatory system consists of blood, blood vessels and heart.

Blood

It is a fluid tissue that flows in blood vessels. It is red in colour and it flows through a network of tubes in whole body called blood vessels. Blood is pumped to every part of the animal by heart.

Blood consists of four components, i.e.

Plasma

Red Blood Cells (RBCs)

White Blood Cells (WBCs)

Platelets

Plasma is a liquid while RBCs, WBCs and platelets float in it.

1. Plasma

It is the sticky liquid part of the blood which is pale yellow in colour. It is 90% water and 3.5% common salt.

It contains dissolved substance such as digested food and waste products and carry them from one part to another part in the body.

2. Red Blood Cells (RBCs)

RBCs are red in colour due to the presence of pigment called haemoglobin.

This pigment carries oxygen by binding with it.

Haemoglobin is a red protein that binds with oxygen and transports oxygen to all the parts of the body and ultimately to all the cells.

It is the presence of haemoglobin which makes the blood appear red.

When haemoglobin binds with oxygen, it forms oxyhaemoglobin which is transported to various body parts.

The carbon dioxide from the various body parts is transported back by binding again with haemoglobin. It forms carboxyhaemoglobin with CO₂.

3. White Blood Cells (WBCs)

The WBCs fight against infection and protect us from diseases. WBCs eats up the germs (like bacteria) that causes disease. WBC also makes antibodies that fight against infection.

The number of WBC is quite less than RBC.

WBC can change their shape and move on their own.

They can squeeze out of the blood vessels to reach any part of the body.

4. Platelets

Blood platelets are small, irregular, tiny fragments of special cells formed in the bone marrow. These are colourless and help in clotting of blood in a cut or wound.

If a cut or wound is made the blood starts flowing from it, after sometime the platelets plug the cut and the bleeding stops due to the formation of dark red clot.

If the platelets are not present in the blood, the blood flow from the cut or wound will not stop causing excess loss of blood which may be fatal to a person leading to death,

Functions of Blood

Various functions of blood are

(i) It transports substances like digested food from the small intestine to the other parts of the body.

(ii) It carries water to all the parts of the body.

(iii) It carries oxygen and CO₂ during circulation.

(iv) It carries waste products like urea from liver to kidney for excretion in urine.

(v) It protects the body from disease.

Blood Vessels

These are tubes or pipes that carry blood throughout the body. It runs between the heart and the rest of the body.

There are three major types of blood vessels in the body, i.e.

Arteries

Veins

Capillaries.

1. Arteries

These carry blood from the heart to all the parts of body. These lie quite deep under our skin and cannot be seen easily.

Arteries have thick elastic walls as the blood flows at high pressure due to pumping action from heart through arteries.

No valves are present in the arteries.

The main artery, i.e., aorta is connected to the left ventricle of the heart. It carries oxygenated blood from the left ventricle to all the parts of body except the lungs.

Another artery called pulmonary artery is connected to the right ventricle of the heart and carries deoxygenated blood from the right ventricle to the lungs.

The arteries normally carry oxygenated blood from the heart but one artery called pulmonary artery carries deoxygenated blood from heart to lungs.

2. Veins

These are the blood vessels that carry blood from all the parts of the body back to the heart.

These tube-like blood vessels are situated just under the skin and can easily be seen as greenish-blue tubes or lines below the skin.

These carry deoxygenated blood from the body parts to heart. Veins have thin walls and blood flows ate low pressure through the veins.

Therefore, veins have valves in them which allow the blood to flow in one direction and prevent the back flow of blood in veins.

Usually, veins carry deoxygenated blood but pulmonary vein that is connected to the left atrium of the heart, carries oxygenated blood from the lungs to the heart.

Differences between artery and vein

 

Pulse Rate

To know your pulse rate, place the middle and index finger of your right hand on the inner side of your left wrist.

You will feel the throbbing movement at this place. This throbbing is called the pulse. The pulse is produced due to the blood flowing in the arteries.

The number of beats per minute is called the pulse rate.

At resting phase, a normal person has a pulse rate between

72-80 beats per minutes.

3. Capillaries

These are extremely thin blood vessels that connect the arteries to veins.

These allow substances to pass from blood into the body cells and also from body cells into the blood.

The exchange of substances like food, O₂, CO₂, etc., between the blood and the body cells take place through the capillaries.

 

Overall Diagram

Blood Groups

The blood group of an individual human being always remains unchanged throughout their life. Karl Landsteiner described that human blood can be divided into four groups, i.e. A, B, AB and O.

These are named on the basis of substance present in the blood (RBC).

Every human being has one of these four groups of blood which is inherited from parents to offspring and is never changed.

If a person gets injured and heavy blood loss occurs, there is a need to give blood of another person to the patient.

The person who gives the blood is called donor while the person who receives the blood is called recipient.

The process of donation of blood from one person to another is called blood transfusion.

Before donation, the blood group must be matched because transfusion of different groups can be. dangerous.

The RBCs of the patient receiving blood will stick together and may cause death of the patient.

This matching of blood group is called blood group compatibility. It can be shown as follows :

 

Heart

Heart is located in the chest cavity slightly towards the left side.

It lies between the two lungs and above the diaphragm.

The heart is made up of special muscles called cardiac muscles that do not fatigue and are not the solid muscle.

The size of our heart is roughly equal to our closed fist and is enclosed in protective cover called pericardium.

The heart is hollow inside.

Structure of Heart

The heart has four compartment called as chambers.

The upper two chambers of heart are called atria (singular atrium).

The lower two chambers of heart are called ventricles.

On the left side of heart are left atrium and left ventricle and on the right side of the heart are right atrium and right ventricle.

The atria and ventricles are separated by valves.

These are the muscular flaps that allow the blood to flow in only one direction.

The right side of the heart carries deoxygenated blood while the left side of the heart carries oxygenated blood.

The left and right side of the heart act as two separate pumps.

The heart is separated by a partition called septum (from right side of the heart to the left side).

This prevents mixing of oxygenated and deoxygenated blood inside the heart.

Heartbeat

The rhythmic contraction and relaxation of heart muscles that produce a specific sound of lubb-dubb is called heartbeat.

The average heartbeat of an adult person is 72-80 beats per minute at resting but the number increases during and after a physical exercise or when a person is excited.

The heartbeat is equal to the number of pulse in a minute.

Stethoscope

The heartbeat can be heard by an instrument called as stethoscope.

It consists of

(i) a chest piece that carries a sensitive diaphragm

(ii) two ear pieces

(iii) a tube joining both the parts

Doctors get to know about the condition of heart by listening the sound through a stethoscope.

Mechanism of Circulation

The contraction of two atria is immediately followed by the contraction of two ventricles which leads to the continuous flow of blood in the human body.

(i) The blood passes through the capillaries of the lungs and is mix with oxygen.

This oxygenated blood is then carried from the lungs to the left auricle by four pulmonary veins.

(ii) The left atrium contracts and the oxygenated blood is pushed into left ventricles.

(iii) The left ventricle pumps the blood into the biggest blood vessels of the body called aorta. It distributes oxygen-rich blood to the different parts of the body.

(iv) The oxygenated blood is distributed to all the organs of the body through capillaries.

(v) The deoxygenated blood from various organs of the body enters from the capillaries to veins and then to the right atrium.

(vi) The right atrium contracts and pushes the deoxygenated blood into right ventricles through the opened valve.

(vii) Right ventricles pump the impure blood into pulmonary arteries that carry it to the right and left lungs for purification.

(viii) The CO₂ is released as waste product from the lungs and again the blood absorbs oxygen and becomes oxygenated.

The valves present on both sides of heart regulate the blood flow from one chamber to another.

Circulation in Sponges and Hydra

Sponges and Hydra are the simple animals that do not possess any circulatory system.

They live in water and therefore, the food and oxygen enter into their body along with water.

The water also carries the CO₂ and other waste material away from the body as it moves out of their bodies.

Excretion

The process of removal of waste materials produced in the cells of the living organism is called excretion.

When our body uses food, water and air, it produces some by products or unwanted substances. These are called waste materials.

These waste material are toxic or poisonous and causes harm to the body.

These poisonous substances if get mixed with blood may become fatal and may cause death of an organisms.

Therefore, the waste material must be removed from the body so that a person may stay healthy.

These waste material produced after the various functions of body cells include CO₂, urea, sweat, etc.

These waste materials are removed from the body different organs of the body like lungs (CO₂), kidney (urea) and sweat glands (sweat).

These parts or organs of the body that are involved in the process of excretion are called excretory system.

Excretory System in Humans

Urea is the major waste product released in our body.

It is produced as a waste product of the decomposition of unused food proteins in the liver.

It is a poisonous substance which must be removed from the body.

Urea from blood is removed by the kidney.

Therefore, kidney is the main excretory organ in our body.

The urea and other unwanted salts when dissolve in water form a yellowish liquid waste called urine.

It consists of 2.5% urea, 2.5% other waste salts and 95% water.

An adult human being normally passes out 1-1.8 L of urine per day.

The excretory system collects the urine and remove it.

The excretory system of human being consists of two kidneys, two ureters, a bladder and a urethra.

Kidneys

These are called the magic filters.

Kidney are bean-shaped organs present at the back of our body, just above the waist. It is brick red coloured about 4 inches long.

It is richly supplied with blood vessels.

Kidney can filter the unwanted substances from the blood.

Each kidney consists of thousands of tiny filters called nephrons.

When the blood containing urea and other waste salts pass through these nephrons, it filters the blood and removes urea and salts and urine are left in the kidney.

The urine thus formed by each of the kidney is then passed through the ureter (a tube-like structure which connects the kidney to the bladder) to urinary bladder.

The urine is stored in the urinary bladder for some times and at regular intervals it, is removed through the opening at the end of the tube called urethra.

The process of ejection of urine is called micturition.

Dialysis

The normal functioning of kidney is necessary for good health of a person. But sometimes the kidney may stop working due to infection or injury.

This condition of kidney is called kidney failure which may lead to the accumulation of urea in the blood of a person.

Since, urea is a toxic substance which must be removed from the blood.

Such person having kidney failure cannot survive unless his blood is filtered periodically through the artificial kidney machine to remove urea.

The process used for cleaning the blood of a person by separating the waste product urea from it is called dialysis.

This machine removes urea and other waste the product periodically.

The long term solution for the patient suffering from kidney failure is kidney transplantation. In this method, the diseased or damaged kidney is removed and matching kidney is donated by a healthy person.

The donated kidney is transplanted in its place by performing surgery.

The opening of urinary bladder is controlled by the ring of muscle called as bladder sphincter.

When the bladder becomes full with urine this bladder sphincter opens and allows the urine to flow out.

Production of Carbon Dioxide

It is produced as a waste product in our body cells during the process of respiration.

The food is broken down during respiration to release energy and releases CO₂ as a byproduct.

This CO₂ is removed from our body by the lungs during exhalation.

Therefore, lungs also act as the excretory organs for removing the waste product, CO₂ from the body.

Sweat

Sweat is the liquid waste of the body that is produced by the sweat glands present in our skin.

Sweat contains water, some unwanted salts and urea in a very small amount.

The two major functions of sweat are as follows :

(i) It helps to remove excess water, salt and urea from the body.

(ii) It helps to keep our body cool during hot summer days by evaporation of sweat from the skin.

Excretion in Animals

Like humans, animals also excrete waste products from their body.

The way in which waste materials are removed from the body of the animal depends upon the availability of water.

Fishes are the aquatic animals that excrete ammonia as their waste product.

This ammonia is excreted in the gaseous form which directly gets dissolved in water.

The land animals like lizards, birds, shakes, etc., have less water availability.

These animals excrete this waste material in the form of uric acid pellets.

These are white coloured semi-solid excretory products of several land animals.

Urea is the excretory product of animals like human, cow, goat, etc. and is eliminated as urine.

Amoeba, Paramecium, etc., are the unicellular organisms and their excretory products are removed by diffusion from the body of the organism into the surrounding water.

Transport of Water and Minerals in Plants

Plant root absorbs the water and mineral from the soil.

The roots possess root hair which increase the surface area of the root for absorption of water and minerals nutrient that is dissolved in the water.

It is moved from roots up to the stem and leaves through the tube-like tissue called as xylem.

Absorption and flow of water is a continuous process through the xylem tissue.

Xylem tissues are the continuous network of channels which connect roots to the leaves through the stem and branches.

It thus transports water and minerals to the leaves of the entire plant.

Transport of Food Material in Plants

The food manufactured in the leaf is transported to different parts of plants.

This transportation of food material from leaves to the other parts of plants is carried out by the tissue called phloem and the process of transport of food material is called translocation.

The phloem consists of vessels that are known as sieve tubes.

The xylem and phloem tissues together form the vascular bundles or conducting tissues.

Activity to show that water is transported through xylem (I)

Take a potato and peel off its outer skin. Cut one end and make it base flat.

Now, make a deep and hollow cavity on the opposite side.

Fill this hollow cavity with sugar solution and mark the level of sugar by inserting pin in the wall of the potato.

Place the potato into a dish containing small amount of water.

Be sure that the level of water is below the level of the pin.

Let the apparatus to stand for few hours.

We will observe that after sometime the level of sugar increases inside the potato cavity and reaches above the level of pin mark.

It means that there is an increase in the level of sugar solution inside the potato cavity which is due to the transport of some water from Petri dish through the wall of potato.

This activity clearly shows that for short distance water can move from one cell to another.

In the similar way, water from soil reaches to the xylem vessels of roots and then to the other parts of the plants.

Activity to show that water is transported through xylem (II)

We take a glass tumbler, some water, red ink, a tender herb (e.g., Balsam), and a blade for this activity.

First, we pour water to fill one-third of the tumbler.

Now we add a few drops of red ink to the water.

And then cut the base of the stem of the herb and place it in the glass as shown in the figure.

Next day, we take the stem out of the tumbler and cut the top portion with the help of a blade.

We observe red coloured dots on the cut part of the stem.

It shows that the coloured water has moved from the base of the stem to its tips.

In other words, stem conducts water.

Just like the red ink, minerals dissolved in water also move up the stem, along with water.

Transpiration

The process of evaporation of water through the stomata present on the surface of leaves is called transpiration.

The continuous evaporation of water from the leaves produces an upward pull, called as suction force.

This force pulls the water from roots upward through the stem, branches and finally to the leaves.

Transpiration is a necessary process for plants due to the following reasons:

(i) Suction pull caused due to the evaporation of water helps to draw water to a great height in tall trees.

(ii) It produces cooling effect on the plant and therefore, prevents the plants from the damage caused by heat of sunlight.

(iii) It also helps in the transport of water and minerals to the leaves for performing photosynthesis in them.

The rate of transpiration increases in a hot sunny day or in moving air.

This happens because the heat from sun or moving air causes evaporation of water at faster rate from the stomata.

Increase in the rate of transpiration causes increased rate of absorption of water through the roots.

Therefore, when a potted plant is kept under the running fan, the absorption of water through root will be increased along with the increased rate of evaporation.

 

 

Online Tuitions & Self-Study Courses for Grade 6 to 12 & JEE / NEET