NCERT PCMB OFFICIAL ™✅

2021-09-09 18:17:38 #mostimp POINTS #NCERT

Cleavage and Implantation

• The mitotic division starts as the zygote moves through the isthmus of the oviduct called cleavage towards the uterus and forms daughter cells called blastomeres.

• Morula: The embryo with 8 to 16 blastomeres.

• The blastomeres in the blastocyst are arranged into an outer layer called trophoblast and an inner group of cells attached to trophoblast called the inner cell mass.

• The trophoblast layer attached to the endometrium and the inner cell mass gets differentiated as the embryo.

• After attachment, the uterine cells divide rapidly and cover the blastocyst. As a result, the blastocyst becomes embedded in the endometrium of the uterus. This is called implantation.

• Implantation leads to pregnancy.

• Amnion is innermost embryonic membrane and never participates in placenta formation.

• Chorion is outermost embryonic membrane and always participates in placental formation. Open / Comment

2021-09-07 08:32:53 #mostImportant Points of #NCERT

All the unicellular eukaryotes are placed in Kingdom Protista.

Histone protein is absent in chromosome of dinoflagellates, due to this reason dinoflagellates are called mesokaryote.

Pigments present in dinoflagellates are Chl 'a' and Chl 'c'.

Stored food of dinoflagellates is starch.

Cell wall of diatoms is made up of cellulose + silica.

Pigments present in diatoms are Chl 'a' and Chl 'c
'.
Stored food of diatom is leucosin and fats.

Mixotrophic nutrition is present in Euglenoids.

Stored food of Euglenoids is paramylum and fat.

Slime moulds are also called fungus animal.

At the time of reproduction slime moulds have cell wall.

Mode of nutrition is absorptive in fungi

Cell wall of fungi is made up of chitin.

In fungi the stored food remains in the form of glycogen and oil.

Mycelium of class phycomycetes is coenocytic aseptate.

Phytophthora infestans causes late blight disease in potato. This disease is known as "Famine of Ireland".
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Mycelium of class - ascomycetes is uninucleate septate.
Class ascomycetes is known as "Sac fungi".
A. Flemming obtained the antibiotic penicillin from Penicillium notatum.

Fungus Neurospora is known as "Drosophila of Plant Kingdom".

Yeast is unicellular or non mycelial fungi.

Mycelium of class - basidiomycetes is septate and uni or binucleate.

Basidiomycetes is known as club fungi.

Special type of septa are found in mycelium of class basidiomycetes which are known as dolipore septum.

Clamp connection are formed during reproduction in basidiomycetes.

Puccinia is rust fungus, it causes rust disease in wheat.

Starting of rust disease (Primary infection) on wheat plants takes place through aeciospores.

Deuteromycetes is known as Fungi Imperfecti. Open / Comment

2021-09-07 08:32:45 #mostimpNotes on #Probability #NCERT

The sum of all the probabilities in the sample space is 1.

The probability of an event which cannot occur is 0.

The probability of any event which is not in the sample space is zero.

The probability of an event which must occur is 1.

The probability of the sample space is 1.

The probability of an event not occurring is one minus the probability of it occurring.

The complement of an event E is denoted as E' and is written as P (E') = 1 - P (E)

P (A∪B) is written as P (A + B) and P (A ∩ B) is written as P (AB).

If A and B are mutually exclusive events, P(A or B) = P (A) + P (B)

When two events A and B are independent i.e. when event A has no effect on the probability of event B, the conditional probability of event B given event A is simply the probability of event B, that is P(B).

If events A and B are not independent, then the probability of the intersection of A and B (the probability that both events occur) is defined by P (A and B) = P (A) P (B|A).

A and B are independent if P (B/A) = P(B) and P(A/B) = P(A).

If E1, E2, ......... En are n independent events then P (E1 ∩ E2 ∩ ... ∩ En) = P (E1) P (E2) P (E3)...P (En).

Events E1, E2, E3, ......... En will be pairwise independent if P(Ai ∩ Aj) = P(Ai) P(Aj) i ≠ j.

P(Hi | A) = P(A | Hi) P(Hi) / ∑i P(A | Hi) P(Hi).

If A1, A2, ……An are exhaustive events and S is the sample space, then A1 U A2 U A3 U ............... U An = S

If E1, E2,….., En are mutually exclusive events, then P(E1 U E2 U ...... U En) = ∑P(Ei)

If the events are not mutually exclusive then P (A or B) = P (A) +P (B) – P (A and B)

Three events A, B and C are said to be mutually independent if P(A∩B) = P(A).P(B), P(B∩C) = P(B).P(C), P(A∩C) = P(A).P(C), P(A∩B∩C) = P(A).P(B).P(C)

The concept of mutually exclusive events is set theoretic in nature while the concept of independent events is probabilistic in nature.

If two events A and B are mutually exclusive,

P (A ∩ B) = 0 but P(A) P(B) ≠ 0 (In general)

⇒ P(A ∩ B) ≠ P(A) P(B)

⇒ Mutually exclusive events will not be independent.

The probability distribution of a count variable X is said to be the binomial distribution with parameters n and abbreviated B (n,p) if it satisfies the following conditions:

The total number of observations is fixed

The observations are independent.

Each outcome represents either a success or a failure.

The probability of success i.e. p is same for every outcome.

Some important facts related to binomial distribution:

(p + q)n = C0Pn + C1Pn-1q +...... Crpn-rqr +...+ Cnqn

The probability of getting at least k successes out of n trials is

P(x > k) = Σnx = k nCxpxqn-x

Σnx = k nCxqn-xpx = (q + p)n = 1

Mean of binomial distribution is np

Variance is npq

Standard deviation is given by (npq)1/2, where n

Sum of binomials is also binomial i.e. if X ~ B(n, p) and Y ~ B(m, p) are independent binomial variables with the same probability p, then X + Y is again a binomial variable with distribution X + Y ~ B(n + m, p).

If X ~ B(n, p) and, conditional https://t.me/NCERT_PCMB_OFFICIAL on X, Y ~ B(X, q), then Y is a simple binomial variable with distributionY ~ B( n, pq).

The Bernoulli distribution is a special case of the binomial distribution, where n = 1. Symbolically, X ~ B (1, p) has the same meaning as X ~ Bern (p).

If an experiment has only two possible outcomes, then it is said to be a Bernoulli trial. The two outcomes are success and failure.

Any binomial distribution, B (n, p), is the distribution of the sum of n independent Bernoulli trials Bern (p), each with the same probability p.

The binomial distribution is a special case of the Poisson Binomial Distribution which is a sum of n independent non-identical Bernoulli trials Bern(pi). If X has the Poisson binomial distribution with p1 = … = pn = p then X ~ B(n, p).

A cumulative binomial probability refers to the probability that the binomial random variable falls within a specified range (e.g., is greater than or equal to a stated lower limit and less than or equal to a stated upper limit). Open / Comment

2021-09-07 08:31:51 #ONESHOT on #Wave Optics

Huygens Principle:- Wave-front of a wave, at any instant , is defined as the locus of all the particles in the medium which are being disturbed at the same instant of time and are in the same phase of vibration.

(a) Each point on a wave front acts as a source of new disturbance and emits its own set of spherical waves called secondary wavelets. The secondary wavelets travel in all directions with the velocity of light so long as they move in the same medium.

(b) The envelope or the locus of these wavelets in the forward direction gives the position of new wave front at any subsequent time.

Determination of Phase Difference:-
The phase difference between two waves at a point will depend upon

(a) The difference in path lengths of the two waves from their respective sources.

(b) The refractive index of the medium

(c) Initial phase difference between the source if any
.
(d) Reflections, if any, in the path followed by waves.

Reflection of plane wave at plane surface (Laws of reflection):-

a) The incident ray, the reflected ray and normal to the reflecting surface at the point of incidence, all lie in one plane and that plane is perpendicular to the reflecting surface.
b) The angle of incidence is equal to the angle of reflection.

So, ∠i = ∠r

This signifies angle of incidence is equal to the angle of reflection.

Refraction of light:-
Refraction is the phenomena by virtue of which a wave going from one medium to another undergoes a change in velocity.

(a) The sine of the angle between the incident ray and the normal bears a constant ratio to the sine of the angle between refracted ray and the normal.

sin i/sin r = v1/v2 = 1µ2 = constant

Here, v1 and v2 are the velocities of sound in first and second medium respectively.1µ2 is the refractive index of the second medium with respect to first.

(b) The incident ray, the refracted ray and the normal to the refracting surface lie in the same plane.

Interference:- The modification in the distribution of light energy obtained by the superposition of two or more waves is called interference.

Principle of superposition:- It states that a number of waves travelling, simultaneously, in a medium behave independent of each other and the net displacement of the particle, at any instant, is equal to the sum of the individual displacements due to all the waves.

Displacement equation:- y = R sin 2π/λ (vt+x/2)

Amplitude:- R = 2a cos πx/λ

Intensity:- I = K4a2 cos2 (πx/λ) [I = KR2]

Maxima:- A point having maximum intensity is called maxima.

x = 2n (λ/2)

A point will be a maxima if the two waves reaching there have a path difference of even multiple of λ/2.

Imax = 4Ka2 = 4i (Here, i = Ka2)

Minima:- A point having minimum intensity is called a minima.
x = (2n+1) (λ/2)

A point will be a minima if the two waves reaching there have a path difference of odd multiple of λ/2.

Imin = K. 4a2×0 = 0

Condition for constructive interference:-
Path difference = (2n)λ/2

Phase difference = (2n)π

Condition for destructive interference:-
Path difference = (2n+1)λ/2

Phase difference = (2n+1)π

Coherent Sources:- Coherent sources are the sources which either have no phase difference or have a constant difference of phase between them.
Conditions for interference:-
(a) The two sources should emit, continuously, waves of same wavelength or frequency.

(b) The amplitudes of the two waves should be either or nearly equal

(c) The two sources should be narrow.

(d) The sources should be close to each other.

(e) The two sources should be coherent one.

Young’s double slit experiment:-
Path difference, x = yd/D

Maxima, y = nλD/d

Here, n = 0,1,2,3….

Minima, y = (2n+1) λD/d

Here, n = 0,1,2,3….

Fringe Width:- It is the distance between two consecutive bright and dark fringes.
β = λD/d

Displacement of fringes due to the introduction of a thin transparent medium:-
(a) Shift for a particular order of fringes:-

?y = (β/λ) (µ-1)t

(b) Shift across a particular point of observation:-

µ = (mλ/t) +1

Lloyd’s single mirror:-
?λ = β .2a/D

Power of lens:- P = 100/f Open / Comment

2021-09-07 08:29:18 #imp #NCERT
Relationship between Induced Emf and Flux
In this experiment Faraday took a magnet and a coil and connected a galvanometer across the coil. In the beginning the magnet is https://t.me/NCERT_PCMB_OFFICIAL at rest so there is no deflection in the galvanometer and hence the needle of galvanometer is at center or zero position. When the magnet is moved toward the coil, the needle of galvanometer deflects in one direction. When the magnet is held stationary at that position, the needle of galvanometer returns back to zero position. Now when the magnet is moved away from the coil , there is some deflection in the needle but in opposite direction and again when the magnet becomes stationary at that point with respect to coil , the needle of galvanometer return back to zero position.

Also if the magnet is held stationary and the coil is moved away and towards the magnet, the galvanometer shows deflection https://t.me/NCERT_PCMB_OFFICIAL in a similar manner. It is also observed that faster the change in the magnetic field, the greater will be the induced emf or voltage in the coil.

The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic https://t.me/NCERT_PCMB_OFFICIAL flux through the circuit. This version of the Faraday’s law is valid only when the closed circuit is a loop of indefinitely thin wire. Open / Comment

2021-09-06 15:21:49 #imp #NCERT
1] Artificial system of classification :
→ Carlous linnaeus.....

(Drawbacks) - No natural affinities or similarities between two plants are studied
- He gives equal weightage to vegetative and sexual character

2] Natural system of classification :
→ George Bentham & Josheph
Dalton Hooker .....

(Drawbacks) - No evolutionary characters are studied

3] Phylogenetic system of classification :
→ Engler and prantl ; Ernst Haekle ....... Open / Comment

2021-09-06 15:21:28 #MOSTIMP POINTS OF MALE REPRODUCTIVE STRUCTURE

Testis→Mesodermal in origin
→Oval in shape 4-5 cm long , 2-3 cm wide and 3 cm thick

• Stages of spermatogenesis
Spermatogonial cell (2n) → Primary spermatocyte (2n) →
Spermatids (n) →Sperms (n)

× Interstitial/Leydig's cell secretes male hormone androgen

• Accessory ducts ||
Rete testis → vasa efferentia→epididymis →vasa deferens →ejaculatory duct →Urethta

Upper caput
• Epididymis Middle corpus
Lower coda

• Sperms undergoes maturation in epididymis

• Glands ||
1) seminal vesicle - secretes alkaline seminal fluid contains fructose , fibrinogen , prostaglandins
2) Prostate glands - secrets milky white & slightly acidic prostatic fluid into urethra
3) Bulbourethral gland - Secrets alkaline , viscous , mucus like secretion which help in lubrication

• Semen ||
pH - 7.2 to 7.7 [ 2.5 to 4.0 mL per ejaculation ] →approx 400 million sperms Open / Comment

2021-09-02 18:33:46 #Very Important Points, Must read once #NCERT

Evidences from comparative morphology and anatomy :-

Examples of homologous organs:

(i) Forelimbs of mammals

(ii) Thorn of Bougainvillea and tendril of Cucurbita both are modification of axillary bud.

(iii)Vertebrate hearts or brains

(iv)Mouth parts of insects :
Cockroach Honey bee Mosquito
(Biting & chewing) (Chewing & lapping) (Piercing & Sucking)

(v) Testes in male and ovaries in female

(vi) Potato and Ginger - both are modified shoot

(vii) Radish and Carrot - both are modified roots

Examples of Analogous organs :

(i) Wings of butterfly and birds

(ii) Eye of the octopus and of mammals

(iii) Flippers of Penguins and Dolphins

(iv) Sweet potato (root modification) and potato (stem modification)

(v) Sting of bee and scorpion

(vi) Chloragogen cells of earthworm and liver of vertebrates.

Trick and Mnemonics Open / Comment

2021-09-02 18:32:57 #MOSTImportant for #neet_2021 #NCERT

Special Points:

Atomic radius of Al > Ga : Due to poor sheilding of 3d subshell electron

Atomic radius of 4d » 5d series element due to lan-thanide constriction

Lanthanide Contraction - decrease in atomic/ionic radius with increase in atomic number of lanthanide.

Actinide Contraction - decrease in atomic/ionic radius
with increase in atomic number of actinide
°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° Open / Comment

2021-09-02 18:32:23 #MOSTimp #Chemical Properties of Alkali Earth Metals: #NCERT



1. Reaction with water :

Mg + H2O → MgO + H2

or, Mg + 2H2O → Mg (OH)2 + H2o

Ca + 2H2O → Ca(OH)2 + H2

2. Formation of oxides and nitrides

Be + O2 (air) +Δ→ 2BeO

3Be + N2 (air) +Δ → Be3N2

Mg + air + Δ → MgO + Ng3N2

3. Formation of Nitrides

3M + N2 + Δ → M3N2

Be3N2 + Δ → 3Be + N2

Ba3N2 + 6H2O + Δ → 3Ba (OH)2 + 2NH3

Ca3N2 + 6H2O + Δ → 3Ca (OH)2 + 2NH3

4. Reaction with hydrogen:

M + H2 + Δ → MH2

Both BeH2 and MgH2 are covalent compounds having polymeric structures in which H – atoms between beryllium atoms are held together by three
centre – two electron (3C - 2e) bonds as shown below:

5. Reaction with carbon – (Formation of carbides)

When BeO is heated with carbon at 2175 – 2275 K a brick red coloured carbide of the formula Be2C is formed

2BeO +2C \xrightarrow[]{2175 - 2275 K}Be_2C +2CO

It is a covalent compound and react water forming methane.

Be2C + 4H2O → 2Be (OH)2 + CH4

6. Reaction with Ammonia:

Like alkali metal, the alkaline earth metals dissolve in liquid ammonia to give deep blue black solution from which ammoniates [ M (NH3)6 ]2+ can be recovered.

Anamolous Behaviour of Beryllium:
Be is harder than other members of its group.

Be is lighter than Mg.

Its melting and boiling points are higher than those of Mg & other members.

Be does not react with water while Mg reacts with boiling water.

BeO is amphoteric while MgO is weakly basic.

Be forms covalent compounds whereas other members form ionic compounds.

Beryllium carbide reacts with water to give methane whereas carbides of other alkaline earth metals gives acetylene gas.

Be2C + 4H2O → 2Be (OH)2 + CH4

Mg2C2 + 2H2O → Mg (OH)2 + C2H2

CaC2 + 2H2O → Ca (OH)2 + C2H2

Beryllium does not exhibit coordination number more than four as it has four orbitals in the valence shell. The other members of this group has coordination number

Diagonal relationship of Be with Al:
Unlike groups – 2 elements but like aluminium, beryllium forms covalent compounds.

The hydroxides of Be, [Be(OH)2] and aluminium [Al(OH)3] are amphoteric in nature, whereas those of other elements of group – 2 are basic in nature.

The oxides of both Be and Al i.e. BeO and Al2O3 are high melting insoluble solids.

BeCl2 and AlCl3 have bridged chloride polymeric structure.

The salts of beryllium as well as aluminium are extensively hydrolysed.

Carbides of both the metal reacts with water liberating methane gas.

Be2C + 4H2O → 2Be (OH)2 + CH4

AI4C3 + 12H2O → 4Al (OH)3 + 3CH4

The oxides and hydroxides of both Be and Al are amphoteric and dissolve in sodium hydroxide as well as in hydrochloric acid.
BeO + 2HCI → BeCI2 + H2O

BeO + 2NaOH → Na2BeO2 + H2O

Al2O3 + 6HCI → 2AICI3 + H2O

AI2O3 + 2NaOH → 2NaAIO2 + H2O

Like Al, Be is not readily attacked by acids because of the presence of an oxide film.
Calcium Carbonate (CaCO3):
It occurs in nature as marble, limestone, chalk, coral, calcite, etc. It is prepared as a white powder, known as precipitated chalk, by dissolving marble or limestone in hydrochloric acid and removing iron and aluminium present by precipitating with NH3, and then adding ammonium carbonate to the solution; the precipitate is filtered, washed and dried.

CaCl2 + (NH4)2CO3 →CaCO3 + 2NH4Cl
It dissolves in water containing CO2, forming Ca(HCO3)2 but is precipitated from solution by boiling.

CaCO3 + H2O + CO2 Ca(HCO3)2 Open / Comment