CBSE Class 6-12 - Science - Fathers in Biology

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Fathers of Various Branches in Biology

Aristotle - Father of Biology
credits: wikipedia

Num.	Branch of Biology	Name
1	Father of Biology	Aristotle
2	Father of Zoology	Aristotle
3	Father of Botany	Theophrastus
4	Father of Taxonomy	Carl Linnaeus
5	Father of Plant Physiology	Stephen Hales
6	Father of Bacteriology	Louis Pastuer
7	Father of Microbiology	Leeuwenhoek
8	Father of Immunology	Edward Jenner
9	Father of Cytology	Robert Hooke
10	Father of Mycology	Micheli
11	Father of Genetics	G J Mendel
12	Father of Experimental Genetics	T. H. Morgan
13	Father of Bryology	Johann Hedwig
14	Father of Eugenics	Francis Galton
15	Father of Microscopy	Marcello Malphigi
16	Father of Bio-diversity	E.O. Wilson
17	Father of Medicine	Hippocrates
18	Father of modern Anatomy	Andreas Vesalius
19	Father of Radiation Genetics	H. J. Muller

CBSE Class 9 Science - Diversity in Living Organisms (Important Differences)

Diversity in Living Organisms

Evolutionary Tree
credits: wikipedia

Important Differences

Five classes of vertebrates are Pisces, Amphibia, Reptilia, Aves and Mammalia

	Pisces	Amphibia	Reptilia	Aves	Mammalia
Habitat	Aquatic	Both land and water	Some terrestrial, others aquatic	Terrestrial (aerial)	Usually terrestrial, few aquatic.
Skin	Covered with scales/plates	Smooth skin with mucus glands and lacking scales	Waterproof skin with scales	Mostly covered with feathers	Covered with hair and contains sweat and oil glands.
Body Temperature Control	Cold blooded	Cold blooded	Cold blooded	Warm blooded	Warm blooded
No. of heart chambers	2	3	3 (except crocodiles)	4	4
Respiration	Gills	Gills, lungs or skin	Lungs	Lungs	Lungs
Mode of Reproduction	Oviparous (egg laying)	Oviparous	Oviparous	Oviparous	Viviparous
Locomotion	Tail and fins	Limbs	Limbs	Wings	Limbs
Examples	Rohu, shark, sea-horse, sting ray	Frog, Toad salamander,	Crocodile, snake, turtle, lizard	Pigeon, ostrich, hen, duck	Human, whale, bat, lion

CBSE Class 9 - Science - Gist on Work, Energy and Power

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Study Points

1. Work is said to be done if a force is applied on the object and it is displaced from its original position.

2. Three things are necessary for the performance of work:

• There must be an applied force F.
• There must be a displacement x.
• The force must have a component along the displacement
  

3. The work done W by a force F on an object is
    W = Fd cos θ
    where d is the displacement of an object.
    θ is the angle between the force and the displacement.

4. If displacement is along the direction of work i.e. θ = 0°
    W = Fd


5. If displacement is opposite to the force i.e. θ = 180°
    W = -Fd

6. if the displacement is perpendicular to the force (i.e. θ = 90°), then work done is zero.

7. Work done on an object by a force would be zero if the displacement of the object is zero.

8. Work is a scalar quantity.

9. Unit of work is Joule (J).

10.  1 Joule = 1 newton × 1 metre = 1 Nm
11. One Joule of work is to be done on an object when a force of one newton displaces it by one metre along the time of action of the force.

CBSE Class 9: Science - CH3 - Gist on Atoms, Molecules and Ions

Atoms, Molecules and Ions

Study Points

1. The law of conservation of mass states that there is no detectable loss or gain in total mass of the substances in a chemical reaction.

2. Law of Conservation of mass was proposed by the French chemist Antoine Lavoisier (1774)

3. The Law of constant proportion or definite proportions states that all pure specimens of the same compound contain the same elements combined together in the same proportion by weight.

4. Law of definite proportion was proposed by Louis Proust (1799).

5. An atom is the smallest particle of the element which can take part in chemical change and it can exist independently and retain all its chemical properties.

6. The smallest particle of matter made up of two or more atoms, which can exist in free state, is called a molecule.

7. Law of definite proportion does not hold good when the compound is obtained by using different isotopes of the combining elements .

8. Each atom of an element shows all the properties of the element.

CBSE Class 9/10 - PSA Quiz (English)

 PSA Quiz

Q1: In the following there are six sentences marked as A, B, P, Q, R, S. Positions of A and B are fixed. You are requested to choose one of the four alternatives which would be the most logical sequence of sentences in the passage.

A) The similarity between the human body and a machine is rather superficial.
B) The points of difference far outweigh the points of resemblance.
P) Beyond that comparison fails.
Q) No machine grows in size; no machine sees , hears  or feels.
R) It can be summed up in the statement  that both require  fuel and oxygen  and obtain energy.
S) No machine thinks.

(a) SQPR
(b) RPQS
(c) RPSQ
(d) QSPR

Directions: (Q2 - Q6): Identify the word whose spelling is correct.

Q2:
(a) Profesional
(b) Proffessional
(c) Proffesional
(d) Professional


Q3:
(a) Schdule
(b) Shidule
(c) Schdulle
(d) Schdule

Q4:
(a) Intelligence
(b) Intilligence
(c) Intalligence
(d) Intelligance

Q5:
(a) asshaimed
(b) ashamid
(c) ashimed
(d) ashamed

CBSE Class 9 - Maths - Quadrilaterals (NCERT Ex 8.2)

Quadrilaterals

NCERT Ex 8.2


Q1: ABCD is a quadrilateral in which P, Q, R and S are mid-points of the sides AB, BC, CD and DA (see the given figure). AC is a diagonal. Show that:



(i) SR || AC and SR = AC

(ii)PQ = SR

(iii)PQRS is a parallelogram.

Answer:

(i) In ▲ADC, S and R are the mid-points of sides AD and CD respectively.

In a triangle, the line segment joining the mid-points of any two sides of the triangle is parallel to the third side and is half of it.

∴ SR || AC and SR = AC ... (1)

(ii) In ▲ABC, P and Q are mid-points of sides AB and BC respectively. Therefore, by using mid-point theorem,

PQ || AC and PQ = AC ... (2)

Using equations (1) and (2), we obtain

PQ || SR and PQ = SR ... (3)

⇒ PQ = SR

(iii) From equation (3), we obtained

PQ || SR and PQ = SR

Clearly, one pair of opposite sides of quadrilateral PQRS is parallel and equal.

Hence, PQRS is a parallelogram.


Q2: ABCD is a rhombus and P, Q, R and S are the mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral PQRS is a rectangle.

Answer:

In ▲ABC, P and Q are the mid-points of sides AB and BC respectively.

∴ PQ || AC and PQ = AC (Using mid-point theorem) ... (1)

CBSE Class 9 - Science - CH4 - Gist on Structure of The Atom

Structure of The Atom

Study Points

1. Democritus, Greek Philosopher in 400 BC named the smallest piece of matter “ATOMOS ,” meaning “not to be cut.”
2. Dalton's theory (1803) was based on the premise that the atoms of different elements could be distinguished by differences in their weights.
3. WIth the invention of Scanning Tunneling Microscope we can see atoms.
4. Electrons, protons and neutrons are the fundamental particles of an atom.
5. Electrons were discovered by JJ Thomson in discharge tube experiments as cathode rays.
6. Cathode rays are streams of negatively charged particles.
7. They are deflected by electric and magnetic fields.
8. The specific charge of electron was determined by J. J. Thomson
9. The charge of the electron is 1.602 x 10-19 coulombs.
10. The absolute mass of electron is 9.108 x 10-28 g or 9.108 x 10-31kg
11. Protons are positive rays that were discovered by Goldstein in the discharge tube experiments when perforated metal cathode was used.