Class 7 Science Transportation and Excretion Exam Notes

Class 7 Science Transportation and Excretion Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Covers following topics:

1.Transportation & Excretion

Class 7 Science: Transportation and Excretion Exam Notes

Covers the following topics:

1. Transportation & Excretion
2. Excretion in Plants
3. Transpiration
4. Transportation in Animals
5. Circulatory system
6. Constituents of blood
7. Removal of waste
8. Excretion in humans

TRANSPORTATION & EXCRETION

Plants and animals both require food, air and water for the maintenance and growth of a cell. Each has to be supplied to the cells of the body in the right quantity. The transport of material in plants is carried out by the vascular tissue.

Vascular Tissue

There are 2 types of vascular tissues found in plants:

1. Xylem: Xylem transports water and nutrients upwards from the roots to the leaves. Evaporation of water from the leaves during transpiration produces a pulling force causing water to move up.
2. Phloem: It carries the food prepared by the leaves during photosynthesis downward to all parts of the plant.

Transportation of water, minerals and food

The roots have root hairs, which increase the surface area of the root for absorption of water and minerals dissolved in water. The root hair comes in contact with water present between soil particles.

  

Transpiration pull

The water moves from the root hair to the xylem in the root. The absorbed water then moves up the stem through the xylem by the force developed in the leaves by transpiration, called transpiration pull.

Ascent of sap

The fluid containing water and dissolved nutrients is called sap. The movement of sap through the xylem is called ascent of sap.

Translocation

The food is transported from the leaves to other parts of the plant. This is called translocation.

EXCRETION IN PLANTS

1. Plants have no special organs for excretion. The excess amount of CO₂ and water is removed through stomata and also from the outer surface of stem, leaves, fruit, etc.
2. Some waste products are collected in vacuoles in the leaves and bark of trees and are excreted by shedding the leaves and bark.
3. Some waste products which are harmless are stored inside the plant body. Rubber and raphides are examples of such products.

TRANSPIRATION

The process of loss of water in the form of vapour through the aerial parts of the plant is called transpiration.

TRANSPORTATION IN ANIMALS

In higher animals, digested food, gases and waste material are carried by blood. Blood flows through a network of tubes, which are called blood vessels, and forms a system known as the circulatory system.

CIRCULATORY SYSTEM

It consists of the heart, blood vessels and the blood.

Heart

1. It is a muscular organ, which pumps blood around the blood vessels.
2. It has four chambers, viz. left auricle, left ventricle, right auricle and right ventricle.
3. Ventricles are the two lower chambers. The left ventricle receives blood from the left auricle and pumps it into the aorta. Aorta is the largest artery in the body.
4. The right ventricle receives blood from the right auricle and pumps it through the pulmonary trunk to the lungs.
5. The four chambers open and close about 100000 times a day.
6. The heartbeat that we can hear is due to contraction and relaxation of heart muscles or cardiac muscles. The heart in a healthy body beats around 72 times in a minute.
7. Contraction is held in auricles and relaxation is done in ventricles.
8. Contraction of cardiac muscles is called systole and relaxation of cardiac muscle is called diastole.
9. During diastole, the heart receives blood, and during systole, the ventricles contract to pump blood into blood vessels.
10. The sound of the heartbeat is called the ‘Lub-dub’ sound. ‘Lub’ is due to contraction of ventricles and ‘dub’ is due to closure of auricle valves.
11. The heartbeat is heard with an instrument called a ‘stethoscope’, a device that makes the sound of the heartbeat louder. Noting the pulse rate means noting the number of times the heart beats in a minute.

Blood vessels

These are blood-filled tubes. Arteries, veins and capillaries are called blood vessels.

Arteries

1. Arteries are thick-walled blood vessels, making up the arterial system and carrying blood away from the heart.
2. Smaller arteries are called arterioles.
3. Arterioles are branched off from arteries.
4. Except in the pulmonary arteries, the blood contains oxygen.
5. In all arteries, blood carries dissolved food and waste, brought into the heart by veins and then transferred to arteries.
6. Arteries carry the food to the cells and waste to the kidneys.

Veins

1. Veins are wide, thick-walled blood vessels.
2. Veins make the venous system and carry blood back to the heart.
3. Small veins are called venules.
4. Veins contain valves to stop blood flowing backwards due to gravity and are formed of merging venules.
5. The blood in the veins leading from the digestive system and liver also carries dissolved food. This is transferred to the arteries in the heart.

Capillaries

1. Narrow, thin-walled blood vessels branching off arterioles to form a complex network are called capillaries.
2. Dissolved food and oxygen pass out through the walls of capillaries to the body cells, and carbon dioxide and waste pass in.
3. The capillaries of the digestive organs and liver also pick up food.
4. Finally, capillaries join up to form small veins called venules.

Blood

1. It is a connective tissue in fluid form.
2. An adult human has around 5.5 litres of blood.
3. It is a red fluid that flows in the body.
4. It supplies food and oxygen to every body cell.
5. It removes wastes from the cells.
6. It regulates body temperature.
7. It protects against infection.

CONSTITUENTS OF BLOOD

RBC (Red Blood Corpuscles)

1. This is also called erythrocytes.
2. RBC are red, disc-shaped cells with no nuclei.
3. They are made in the bone marrow and contain haemoglobin (an iron compound that gives blood a dark red colour).
4. RBC combine with oxygen to form oxy-haemoglobin and the blood becomes bright red.
5. The red cells pass the oxygen to the body cells by the process of diffusion and then return to the lungs with haemoglobin.

WBC (White Blood Corpuscles)

1. This is also called leucocytes.
2. WBC are large, opaque blood cells, which help in body defence.
3. WBC make antibodies. Antibodies are proteins that combat antigens, i.e. foreign substances such as bacteria or viruses, and so fight infection.

Plasma

1. It is a pale liquid with 90% water in it.
2. Plasma contains the blood cells.
3. Plasma carries dissolved food for the body cells, waste matter, and carbon dioxide secreted by them.

Platelets

1. These are also called thrombocytes.
2. They are very small, disc-shaped bodies with no nuclei.
3. They are made in the bone marrow.
4. They gather particularly in an injured area, where they are important in clotting the blood.

REMOVAL OF WASTE

The process of removing waste from the body is called excretion. Several organs of the body are involved in the process of excretion:

1. The waste generated in the process of digestion is expelled from the large intestine through the anus.
2. Carbon dioxide produced in the process of respiration is expelled from the lungs through the nostrils.

EXCRETION IN HUMANS

Chemical waste like urea is excreted by the urinary system and skin. The excretory system in human beings consists of the following organs:

1. A pair of kidneys
2. A pair of ureters
3. The urinary bladder
4. Urethra

Urinary system or Excretory system

Kidneys: In our body there is a pair of kidneys located in the abdomen, one on either side of the vertebral column. Each kidney is brick red in colour and bean-shaped. It weighs about 150 g and is about 12 cm in length, 6 cm in width and 3 cm in thickness.Ureters: The ureters are two thin-walled, urine-carrying ducts. A ureter originates from each kidney and is about 30 cm in length. The ureters run downward and open into the urinary bladder.Urinary Bladder: It is a bag-like structure in which urine is stored. Its size and position vary with the amount of urine it contains.Urethra: The urethra is the duct which finally discharges urine from the body.

Function of Kidney

1. They filter wastes from the blood.
2. They help in the formation of urine.
3. They help in eliminating harmful substances from the body.
4. They maintain the water and mineral balance in the body.

Skin

Skin is the outer body covering of the human body. It is made up of several tissue layers cushioned by fats underneath. Skin has many functions. Skin provides stimulation, protects against infection, prevents drying out, regulates body temperature, stores fat, makes vitamin D, and above all excretes waste such as sweat.

3.Transpiration

4.Transpiration in Animals

5.Circulatory system

6.Constituent of blood.

>TRANSPORTATION IN ANIMALS

 It consist of heart, blood vessels & the blood.

Arteries :

• WBC makes antibodies. Antibodies produce antigens, which combat against any bacterial or viral infection.

Antigens are mostly protein.

• Kidneys :