NCERT PCMB OFFICIAL ™✅

2021-10-21 15:43:12 #mostimp
Properties of Cathode Rays

(i) Cathode rays are not electromagnetic rays.

(ii) Cathode rays are deflected by electric field and magnetic field.

(iii) Cathode rays produce heat in metals when they fall on them.

(iv) Cathode rays can pass through thin aluminium or gold foils without puncturing them.

(v) Cathode rays can produce physical and chemical change.

(vi) Cathode rays travel in straight line with high velocity
momentum and energy and cast shadow of objects placed in
their path.

(vii) On striking the target of high atomic weight and high melting point, they produce X-rays.

(viii) Cathode rays produce fluorescence and phosphorescence in
certain substance and hence affect photographic plate.

(ix) Specific charge of an electron was determined by JJ Thomson using perpendicular magnetic and electric field applied on a beam of electrons, at the same place.

(x) Specific charge of electron e/m = E^2/V^2B^2 where, E = electric field, B = magnetic field and V = potential difference applied across ends of tube.

(xi) The value of specific charge of an electron is1.7589 ×10^11 C/kg.



#important_Tricks :

Cell cycle - Go Sally Go! Make Children —- G1-S-G2-M-C ( growth-synthesis-growth-mitosis-cytokinesis)

Mitosis— “People Meet And Talk (PMAT)”——-Prophase,Metaphase,Anaphase,Telophase.

Prophase—-Little Zara! Please, Dance Daily.——-Leptotene,Zygotene,Pachytene,Diplotene,Diakinesis.

Meiosis— PMAT

Prophase,Metaphase, Anaphase,Telophase


Periodic Table Chemistry Tricks -

Group 1 - Lina Kare Rab Se Fariyad
Elements - Li, Na, K, Rb, Cs, Fr

Group 2 - Beta Mange Cars Saari Baap Roye
Elements - Be, Mg, Ca, Sr, Ba, Ra

Group 13 - Bengan, Aaloo, Gazar In Thella
Elements - B, Al, Ga, In, Tl

Group 14 - Chemistry Sir Gives Sanki Problems.
Elements - C, Si, Ge, Sn, Pb

Group 15 - Nepal Pakistan Australia Sab Bikhari (No offence!!)
Elements - N, P, As, Sb, Bi

Group 16 - Old Style Se Tepo
Elements - O, S, Se, Te, Po

Group 17 - Fir Call kar Bahaar AayI Aunty
Elements - F, Cl, Br, I, At

Group 18 - Heena Neena Aur Kareena Xenath Rangeen
Elements - He, Ne, Ar, Kr, Xe, Rn

D blocks elements -

Esi TV Corporation Mange Fir raha hein, Koi Ni Kuch nahi Janta
Elements - Sc, T, V, Cr, Mn, Fe, Co, Ni, Cu, Zn Open / Comment

2021-10-21 15:42:36 #imp #BIOLOGY #NCERT
There are four major groups of protozoans:-

1. Amoeboid Protozoans
These organisms live in freshwater, seawater or moist soil.

Examples Amoeba, Entamoeba, Radiolarians, Pelomyxa, Foraminiferans and Heliozoans.

General features of this group are following:-

(i) They move and capture their prey by putting out pseudopodia (false feet) as in Amoeba (as mouth is absent).

(ii) The body is without periplast. It may be naked or have a calcareous shell.

(iii) Flagella are present in some developmental stages. They also develop when food become scarce.

(iv) Nutrition is holozoic.
(v) Asexual reproduction occurs by binary fission, multiple fission, spores and budding and sexual reproduction occurs by syngamy.

2. Flagellated Protozoans
The members of this group are either free-living or parasitic. Examples Giardia, Trypanosoma, Leishmania, Trichonympha and Trichomonas.

General features of this group are following:-

(i) They have flagella for locomotion as their name suggests.

(ii) They may be aquatic, free-living, parasitic, commensals or symbiotic.

(iii) The body is enclosed by a firm pellicle.

(iv) Nutrition is holozoic, saprobic and parasitic.

(v) Asexual reproduction is by binary fission.

(vi) Sexual reproduction is observed in some forms only.
(vii) Various species of these protozoans causes diseases in humans. For examples,
* Trypanosoma (sleeping sickness)
* Leishmania (kala-azar, dum-dum fever)
* Giardia (giardiasis)
* Trichomonas (leucorrhoea).

3. Ciliated Protozoans
These are aquatic, actively moving organisms because of the presence of thousands of cilia.

Examples Paramecium, Opalina, Vorticella, Podophyra, Balantidium, etc.

Generalfeatures of this group are following :-

(i) Many ciliates live as free-living individual in fresh % and marine water (Paramecium).

(ii) A large number of cilia present on whole body surface.Cilia are used to capture food and for locomotion.

(iii) Nutrition is holozoic except in some parasitic forms.

(iv) The body is covered with flexible pellicle.

(v) There are definite regions for ingestion and egestion.

(vi) Ciliates have a larger macronucleus and smaller micronudeus.

(vii) They have small ejectable trichocysts for defense.

(viii) Osmoregulation occurs by contractile vacuoles.

(ix) Asexual reproduction occurs by transverse binary fission or budding. Cyst formation also occurs during unfavourable condition.

(x) Sexual reproduction by means of conjugation . Open / Comment

2021-10-17 17:37:35 #SHORT_Notes on Cell Cycle and Cell Division #BIOLOGY #NCERT

Types of Mitosis

Anastral mitosis: It is found in plants in which spindle has no aster.

Amphiastral mitosis: It is found in animals in which spindle has two asters, one at each pole of the spindle. Spindle is barrel-like.

Intranuclear or Promitosis: In this nuclear membrane is not lost and spindle is formed inside the nuclear membrane e.g. Protozoans (Amoeba) and yeast. It is so as centriole is present within the nucleus.

Extranuclear or Eumitosis: In this nuclear membrane is lost and spindle is formed outside nuclear membrane e.g. in plants and animals.

Endomitosis: Chromosomes and their DNA duplicate but fail to separate which lead to polyploidy e.g. in liver of man, both diploid (2N) and polyploid cells (4N) have been reported. It is also called endoduplication and endopolyploidy.

Dinomitosis: In which nuclear envelope persists and microtubular spindle is not formed. During movement the chromosomes are attached with nuclear membrane.

Types of meiosis: On the basis of time and place, meiosis is of three types

Gametic/Terminal meiosis: In many protozoans, all animals and some lower plants; meiosis takes place before fertilization during the formation of gametes. Such meiosis is described as gametic or terminal.

Zygotic or Initial Meiosis: In fungi, certain protozoan groups, and some algae fertilization is immediately followed by meiosis in the zygote, and the resulting adult organisms are haploid. Such a meiosis is said to be zygotic or initial. This type of life cycle with haploid adult and zygotic meiosis is termed the haplontic cycle.

Sporogenetic Meiosis

(a) Diploid sporocytes or spore mother cells of sporophytic plant, undergo meiosis to form the haploid spores in the sporangia.

(b) Haploid spore germinates to form haploid gametophyte which produces the haploid gametes by mitosis.

(c) Haploid gametes fuse to form diploid zygote which develops into diploid sporophyte by mitotic divisions. e.g. in higher plants like pteridophytes, gymnosperms and angiosperms. Open / Comment

2021-10-17 17:36:34 SOME TERMS RELATED TO EVOLUTION
#BIOLOGY #NCERT

Adaptation:

Changing to fit a niche or survive in an environment

Anatomy:

Study of the structures of organisms

Artificial Selection:

Characteristics selected by humans

Biogeography:

Study of how species are distributed across the Earth

Biological Species:

Individuals that can interbreed and produce viable offspring

Catastrophism:

Changes in species that happen because of quick and often violent natural phenomena

Cladistics:

Method of classifying species in groups based on ancestral relationships

Cladogram:

Diagram of how species are related

Coevolution:

One species changing in response to changes in another species that it interacts with, particularly predator/prey relationships

Creationism:

Belief that a higher power created all life

Darwinism:

Term commonly used as a synonym for evolution

Descent With Modification:

Passing down traits that might change over time

Directional Selection:

Type of natural selection in which an extreme characteristic is favored


Disruptive Selection:

Type of natural selection that favors both extremes and selects against the average characteristics

Embryology:

Study of the earliest stages of development of an organism

Endosymbiotic Theory:

Currently accepted theory as to how cells evolved

Eukaryote:

Organism made of cells that have membrane-bound organelles

Evolution:

Change in populations over time

Fossil Record:

All known traces of past life ever found

Fundamental Niche:

All available roles an individual can play in an ecosystem

Genetics:

Study of traits and how they are passed down from generation to generation

Gradualism:

Changes in species that happen over long periods of time

Habitat:

Area in which an organism lives

Homologous Structures:

Body parts on different species that are similar and most likely evolved from a common ancestor

Hydrothermal Vents:

Very hot areas in the ocean where primitive life might have begun

Intelligent Design:

Belief that a higher power created life and its changes

Macroevolution:

Changes in populations at the species level, including ancestral relationships

Mass Extinction:

Event in which large numbers of species died out completely

Microevolution:

Changes in species at a molecular or gene level.....

SHARE AND SUPPORT Open / Comment

2021-10-17 17:35:57 SOME #IMPORTANT POINTS #BIOLOGY


1. Bacteria & Fungi
Actinomycetes

2. Reptiles & Birds
Archaeopteryx

3. Chordates & Non-chordates
Balanoglossus

4. Cartilaginous & Bony fishes
Chimera (Rabbit fish/Ratfish)

5. Bryophytes & Pteridophytes
Club moss

6. Coelenterates & Platyhelminthes
Ctenophora

7. Pteridophytes & Gymnosperms
Cycas

8. Reptiles & Mammals
Echidna (Spiny ant eater)

9. Animals & Plants
Euglena

10. Gymnosperms & Angiosperms
Gnetum

11. Protista & Bryophytes
Hornworts

12. Pisces & Amphibia
Latimeria

13. Protista & Fungi
Myxomycetes

14. Annelida & Mollusca
Neopilina

15. Reptiles & Mammals
Ornithorhynchus (Duck billed platypus)

16. Annelida & Arthropoda
Peripatus (walking worm)

17. Protozoa & Porifera
Proterospongia

18. Bony fishes & Amphibia
Protopterus (Lung fishes)

19. Virus & Bacteria
Rickettsia

20. Amphibia & Reptiles
Seymouria

21. Amphibia & Reptilia
Sphenodon (Living fossil lizard)

22. Echinodermata & Chordata
Tornaria larva

23. Annelida & Mollusca
Trochophore larva

24. Living & non-living
Virus

25. Protozoa & Metazoa
Xenoturbella Open / Comment

2021-10-11 18:05:24 #ALL_Tissues #NCERT #BIOLOGY

Tissues are categorized as −
Plant Tissue
Animal Tissue

Plant Tissue

Following are the major types of plant tissue −

Meristematic Tissues
Permanent Tissues

Simple Permanent Tissues
Parenchyma
Collenchyma
Sclerenchyma
Epidermis

Complex Permanent Tissue
Xylem
Phloem

Meristematic Tissue
Meristematic tissue mainly consists of actively dividing cells, and helps in increasing the length and thickening the stems of the plant.

Meristematic tissue, commonly, present in the primary growth regions of a plant, for example, in the tips of stems or roots.

Depending on the region (where the meristematic tissues are found); meristematic tissues are classified as apical, lateral, and intercalary (see the image given below).

Apical meristem (as shown in the above image) is present at the growing tips of stems and roots and helps in their growth.

Lateral Meristem is found in stem or root region and helps in their growth.

Intercalary meristem is found at the base of the leaves or internodes (on twigs) and helps in growth.


Permanent Tissue
Cells of meristematic tissue later differentiate to form different types of permanent tissue.

Permanent Tissue is further categorized as −
Simple Permanent Tissue and
Complex Permanent Tissue

Simple Permanent Tissue
Simple Permanent Tissue further categorized as −
Parenchyma

Collenchyma

Sclerenchyma

Epidermis

Parenchyma tissue provides support to plants and also stores food.
Sometimes, parenchyma tissue contains chlorophyll and performs photosynthesis, in such a condition, it is known as collenchyma.

The collenchyma tissue provides flexibility to plant and also provides mechanical support (to plant).

The large air cavities, which are present in parenchyma of aquatic plants, give buoyancy to the plants and also help them float, are known as aerenchyma.

The Sclerenchyma tissue makes the plant hard and stiff. For example, the husk of a coconut is made up of sclerenchymatous tissue.

The cells of Sclerenchyma tissue normally are dead.

The outermost layer of cells is known as epidermis.

The epidermis is usually made up of a single layer of cells.

The entire surface of a plant has the outer covering of epidermis, which protects all the parts of the plant.


Complex Permanent Tissue
The complex tissue, normally, consists of more than one type of cells which work together as a unit.

Complex tissues help in the transportation by carrying organic material, water, and minerals up and down in the plants.

Complex Permanent Tissue is categorized as;
Xylem

Phloem

Xylem, normally, consists of tracheid, vessels, xylem parenchyma, and xylem fibers.

Xylem is accountable for the conduction of water and mineral ions/salt.

Phloem, normally, is made up of four types of elements namely −
Sieve tubes

Companion cells

Phloem fibers and

Phloem parenchyma

Phloem tissue transports food from leaves to other parts of the plant. Open / Comment

2021-10-11 18:04:38 #Happy International #Girl's day. Open / Comment

2021-10-11 18:03:36 #Genetic Code #NCERT #BIOLOGY

(1) Term genetic code was given by George Gamow (1954). He was the first to propose the triplet code (one codon consists of three nitrogen bases).
(2) The relationship between the sequence of amino acids in a polypeptide chain and nucleotide sequence of DNA or mRNA is called genetic code.
(3) There occur 20 types of amino acids which participate in protein synthesis. DNA contains information for the synthesis of any types of polypeptide chain. In the process of transcription, information transfers from DNA to m-RNA in the form of complementary N2-base sequence.
(4) A codon is the nucleotide sequence in m-RNA which codes for particular amino acid; whereas the genetic code is the sequence of nucleotides in m-RNA molecule, which contains information for the synthesis of polypeptide chain.
(5) 61 out of 64 codons code for only 20 amino acids.
(6) The main problem of genetic code was to determine the exact number of nucleotide in a codon which codes for one amino acid.

Characteristics of genetic code

(1) Triplet in nature
(a) A codon is composed of three adjacent nitrogen bases which specify one amino acid in polypeptide chain.
(b) For example- In m-RNA if there are total 90 N2 – bases. Then this m-RNA determines 30 amino acids in polypeptide chain.

(2) Univerality
(a) The genetic code is applicable universally.
(b) The same genetic code is present in all kinds of living organism including viruses, bacteria, unicellular and multicellular organisms. In all these organisms, triplet code for specific amino acid.

(3) Non-ambiguous
(a) Genetic code is non ambiguous i.e. one codon specifies only one amino acid and not any other.
(b) In this case one codon never code two different amino acids. Exception GUG codon which code both valine and methionine amino acid.

(4) Non-overlapping
(a) A nitrogen base is a constituent of only one codon.

(5) Comma less
(a) There is no punctuation (comma) between the adjacent codon i.e. each codon is immediately followed by the next codon.
(b) If a nucleotide is deleted or added, the whole genetic code read differently.
(c) A polynucleotide chain having 50 amino acids shall be specialized by a linear sequence of 150 nucleotides. If a nucleotide is added in the middle of this sequence, the first 25 amino acids of polypeptide will be same but next 25 amino acids will be different.

(6) Degeneracy of genetic code
(a) Only two amino acids – tryptophan and methionine are specified by single codon.
UGG for tryptophan
AUG for methionine

(b) All the other amino acids are specified or coded by 2 to 6 codons.
(c) Leucine, serine and arginine are coded or specified by 6-codons.
(d) Degeneracy of genetic code is related to third position (3’-end of triplet codon) of codon. The third base is described as ‘Wobble base’. Open / Comment

2021-10-07 18:54:30 ╭───────•𐂡•───────╮
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╰───────•𐂡•───────╯ Open / Comment

2021-10-07 18:54:17 ╭───────•𐂡•───────╮
ıllı @NCERT_PCMB_OFFICIAL ıllı
╰───────•𐂡•───────╯ Open / Comment