Estrogen and progesterone are the female hormones produced by ovaries that ensure proper female development and fertility. Both these hormones have direct effects on the development of mammary glands. These are absolutely essential for the development of mammary gland.

Estrogen and progesterone are the female hormones produced by ovaries that ensure proper female development and fertility. Both these hormones have direct effects on the development of mammary glands. These are absolutely essential for the development of mammary gland.

Bacteria

They are very small,single-celled micro-organism which have cell wall but do not have an organises nucleus and other structures.

For Example:Lactobacillus,Rhizobium.

Some of the diseases cause by bacteria are cholera,typhoid,tuberculosis,diphtheria etc.

Viruses

They are the smallest micro-organism which can develop only inside the cells of the host organism .

Viruses can reproduce and multiply only inside the cells of other organism .They are the agents of diseases.

The diseases caused by virus are common cold, influenza,measles,polio,chicken pox,small pox etc.

For Example:HIV(Human Immuno deficiency) virus causes AIDS, Common cold virus, Corona (COVID-19)

Bacteria

They are very small,single-celled micro-organism which have cell wall but do not have an organises nucleus and other structures.

For Example:Lactobacillus,Rhizobium.

Some of the diseases cause by bacteria are cholera,typhoid,tuberculosis,diphtheria etc.

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Groups of Micro-organism

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Question 1 What is the name of micro-organism which reproduce only inside the living cells of other organism?

Question 2 What are the major groups of micro-organism?

Question 3 Name any 2 diseases caused by bacteria?

Question 4 Name any 2 diseases caused by virus?

Question 5 Name any 2 diseases caused by algae?

Question 6 Name any 2 diseases caused by fungi?

Question 7 Name any 2 diseases caused by protozoa?

Question 8 What is the full form of HIV?Name the disease caused by HIV?

Question 9 Name any 2 bacteria?

Question 10 Name any 2 virus?

Question 11 Name any 2 fungi?

Question 12 Name any 2 protozoa?

Question 13 Name any 2 algae?

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Contents [<a href="https://classnotes.org.in/class-8/micro-organismfriend-and-foe/groups-of-micro-organism/#">hide</a>]

• <a href="https://classnotes.org.in/class-8/micro-organismfriend-and-foe/groups-of-micro-organism/#Groups_of_micro-organism">1 Groups of micro-organism</a>
• <a href="https://classnotes.org.in/class-8/micro-organismfriend-and-foe/groups-of-micro-organism/#Bacteria">2 Bacteria</a>
• <a href="https://classnotes.org.in/class-8/micro-organismfriend-and-foe/groups-of-micro-organism/#Viruses">3 Viruses</a>
• <a href="https://classnotes.org.in/class-8/micro-organismfriend-and-foe/groups-of-micro-organism/#Protozoa">4 Protozoa</a>
• <a href="https://classnotes.org.in/class-8/micro-organismfriend-and-foe/groups-of-micro-organism/#Algae">5 Algae</a>
• <a href="https://classnotes.org.in/class-8/micro-organismfriend-and-foe/groups-of-micro-organism/#Fungi">6 Fungi</a>

Groups of micro-organism

Micro-organism are classified into 5 major groups:

1)Bacteria

2)Viruses

3)Protozoa

4)Algae

5)Fungi

Bacteria

They are very small,single-celled micro-organism which have cell wall but do not have an organises nucleus and other structures.

For Example:Lactobacillus,Rhizobium.

Some of the diseases cause by bacteria are cholera,typhoid,tuberculosis,diphtheria etc.

Viruses

They are the smallest micro-organism which can develop only inside the cells of the host organism .

Viruses can reproduce and multiply only inside the cells of other organism .They are the agents of diseases.

The diseases caused by virus are common cold, influenza,measles,polio,chicken pox,small pox etc.

For Example:HIV(Human Immuno deficiency) virus causes AIDS, Common cold virus, Corona (COVID-19)

1. The first method advocates the use of mosquito nets and mosquito repellent such as permethrin to prevent mosquitoes from biting.
2. The second form of treatment uses a chemical called Quinine present in the bark of a cinchona tree. A form of drug chloroquine has proven very effective against malaria even though it is not a vaccine.

Methods of preventing malaria are:
(i) Use of insect repellants to prevent mosquito bite.
(ii) Wire-gauzing of "doors, windows and ventilators to check the entry of mosquitoes into the houses.
(iii) Periodic spray of insecticides (e.g.,  D.D.T. and B.H.C) to kill adult mosquitoes as well as spray of kerosene oil or insecticides on ponds, ditches etc. to kill the larvae.
(iv) Introducing larvivorous fishes (e.g., Gambusia, minnows, trouts) in water bodies. These fishes feed on mosquito larvae.

Preparation of soil: Soil is prepared before sowing the seeds. The soil is loosened to increase the absorption of water and manures. Loosening of soil particles adds humus and nutrients in the soil that increases crop yields. Tilling or loosening the soil is done by ploughs which are pulled by a pair of bulls.

Sound needs a material medium like solid ,liquid or gas to travel and be heard because the molecules of solid, liquid and gases carry sound waves from one place to another. Sound cannot travel through vacuum or empty space because vacuum has no molecules which can vibrate and carry sound waves.

The sound is produced by vibrating objects. They travel from one place to another in the form of waves. Hence, the name sound waves.

In string instruments like veena, sitar or violin, sound is produced because of vibration. Vibration of the strings in string instruments produce sound

Whereas

Wind instruments like flute produce sound by the help of air blown into them, in other words sound is produced by vibration occuring in air.

Slow combustion is a form of combustion which consumes time and takes place slowly. Cellular respiration is an example of slow combustion. In respiration, glucose is oxidised and carbon dioxide and energy are released in the process. This is a very similar reaction to combustion. When a hydrocarbon burns, such a natural gas or methane (CH₄), it combines with oxygen, producing CO₂ and water and large amount of energy.

However, the energy released in combustion and respiration are very different. 

It consist of Ovaries,oviduct,fallopian tubes,uterus,******.

1)Ovaries:They are oval shaped organ, inside abdominal cavity.There are 2 ovaries, makes egg or ova and *** hormones, composed of thousand of follicles.At puberty these follicles mature to form ripe egg.

2)Oviducts:Above the ovaries,not connected directly to ovaries but have funnel shaped opening which almost cover ovaries.

The egg released by an ovary goes into oviduct through funnel shaped opening.Fertilisation take place in oviduct.

3)Uterus:The two oviducts connect to a bag like organ called uterus.the growth and development of fertilised egg take place in uterus.

4)Cervix:Uterus is connected through a narrow opening called cervix to another tube called ******.

Tadpoles are frog firstly from their adult

Like the adult man is known as baby in small age

At the age of adolescence a human body undergoes several changes that marks the onset of puberty. At this age they become capable of reproduction.

During adolescence a human body undergoes following changes:

Increase in height

• There is a sudden increase in height. Some of the children may grow at the age of puberty and then slow down but some of them may grow gradually. Genes inherited from parents, fooding habits influence the growth in children to a great extent.

Change in shape of body

• During puberty the body of children undergoes several changes. In boys the shoulders grow broad, muscles grow more prominently.  In girls the region below the waist becomes wide.
• Both boys and girls reach their maximum height at the age of 18 years.

Change in voice

• Voice box grows as soon as the children reach the age of adolescence. Boys grow a larger voice box that appears as a bulging part of the throat. This is called Adam’s apple. As they reach adolescent their voice becomes hoarse.

The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. The period of adolescence is normally 11 years to 19 years

Mercury is used in extracting gold from ore in artisanal mining. The mercury amalgam is usually vaporised to leave the pure gold behind. Highly toxic process.

Pure substances are substances that are made up of only one kind of particles and has a fixed or constant structure. Pure substances are further classified as elements and compounds. An element is a substance that consists of only one type or kind of atom.

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

Two advantages of sowing by transplantation are:-
i) It allows us to plant the seedlings at the right spacing and select only healthy seedlings for the plants.
ii) It promotes better development of shoot system of plants and penetration of roots in the soil.

The sound which is unpleasant for our ears is called noise while music is the sound which is pleasant for our ears. Music becomes noise sometimes when it crosses the bearable range of sound for our ears.