PW UDAY 2026

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Important terms in Biology for NEET l

➖ DNA: Deoxyribonucleic acid, a molecule that carries genetic information.
➖ RNA: Ribonucleic acid, a molecule that plays a key role in protein synthesis.
➖ Protein: A macromolecule made up of amino acids that carries out a variety of functions in the cell.
➖ Enzyme: A type of protein that catalyzes chemical reactions in the cell.
➖ Cell membrane: The thin, flexible layer that surrounds all cells and regulates the movement of molecules in and out of the cell.
➖ Mitosis: The process by which a single cell divides into two identical daughter cells.
➖ Meiosis: The process by which cells divide to produce gametes (sperm and eggs), each with half the number of chromosomes as the parent cell.
➖ Gene: A segment of DNA that codes for a specific protein or trait.
➖ Allele: One of two or more alternative forms of a gene.
➖ Mutation: A change in the DNA sequence that can result in altered gene function or the creation of new alleles.
➖ Natural selection: The process by which individuals with advantageous traits are more likely to survive and reproduce, leading to the evolution of populations over time.
➖ Adaptation: A trait or characteristic that increases an organism's fitness in its environment.
➖ Photosynthesis: The process by which green plants convert sunlight into energy in the form of organic compounds.
➖ Cellular respiration: The process by which cells convert organic compounds into energy in the form of ATP.
➖ Ecosystem: A community of living and non-living things that interact with each other and their environment.
➖ Homeostasis: The ability of organisms to maintain a stable internal environment in the face of changing external conditions.
➖ Evolution: The process by which species change over time as a result of genetic variation and natural selection.
➖ Ecology: The study of the interactions between living organisms and their environment.
➖ Biotechnology: The use of living organisms or their products to develop new products or processes.
➖ Epidemiology: The study of the distribution and determinants of health and disease in populations.
➖ Chromosome: A structure made of DNA and protein that carries genetic information.
➖ Cytoplasm: The gel-like substance inside a cell that contains organelles and other cell components.
➖ Organelle: A specialized structure within a cell that performs a specific function.
➖ Nucleus: The control center of a cell that contains the cell's DNA.
➖ Ribosome: The site of protein synthesis in a cell.
➖ Mitochondria: The organelles responsible for producing ATP through cellular respiration.
➖ Chloroplast: The organelles in plant cells responsible for photosynthesis.
➖ Cytoskeleton: The network of protein filaments that give a cell its shape and allow for movement.
➖ Endoplasmic reticulum: A network of membranes in the cytoplasm that is involved in protein and lipid synthesis.
➖ Golgi apparatus: An organelle that modifies, sorts, and packages proteins for secretion or transport.
➖ Lysosome: An organelle that contains enzymes for breaking down and recycling cellular waste.
➖ Vacuole: A membrane-bound organelle that stores materials such as water, nutrients, and waste products.
➖ ATP: Adenosine triphosphate, the molecule that carries energy within cells.
➖ Aerobic respiration: The process of producing ATP in the presence of oxygen.
➖ Anaerobic respiration: The process of producing ATP in the absence of oxygen.

🌟 Important Points of NCERT 🌟

1. 1770 : Joseph Priestley - Essential role of air in growth of green plant.
2. 1774 : Joseph Priestley - Discovered O2
.
3. 1831 : Robert Brown - Ist discovered and described nucleus.
4. 1838 : Schleiden (German Botanist) - Work on plants.
5. 1839 : Schwann(British Zoologist) - Work on both plants & animals.
6. 1855 : Rudolf Virchow - Omnis cellula-e-cellula (cells arises from
pre-existing cells).
7. Life originate from pre-existing life : Pasteur (Yeast).
8. Life originate from non-living (decaying & rotting matter) : Spontaneous
generation.
9. Life originate from pre-existing non-living organic molecules (RNA,
Protein)- Oparin (Russia) & Haldane (England)- Chemical Evolution.
10. 1856 - 1863 : Mendal experiment on garden pea. (7 years)
11. 1860 : Julius von Sachs - Developed hydroponics.
12. 1865 : Mendal published his work.
13. 1866 : Langdon Down - Down’s syndrome.
14. 1869 : Friedrich Meischer - Ist identified DNA and named it nuclein.
15. 1891 : Henking - Discovered X-body.
16. 1891 : Fossil discovered in Java - Homo erectus.
17. 1892 : Ivanowsky - Discovered virus.
18. 1898 : Beijerinek - Contagium vivum fluidum (infectious living fluid).
19. 1898 : Camillo Golgi - Discovered (observed) G.B.
20. 1900 : de Vries, Corre ns and von Tsche rmak inde pende ntly
rediscovered Mendel’s results.
21. 1902 : Chromosome movement during meiosis has been worked out.
22. 1905 : Law of limiting factor (Blackmann).
23. 1928 : Fredrick Griffith - Transforming experiment with Streptococcus
pneumoniae (Diplococcus).
24. 1935 : Stanley - Crystallised viruses.
25. 1937 : Ramde o Misra obtained Ph.D. in Ecology from Lee ds
university (U.K.).
26. 1938 : Coelocanth fish caught in South Africa.
27. 1945 : Fleming, Chain & Florey - Awarded Nobel prize.
28. 1950 : Watson obtained Ph.D. on a study of the effect of hard X-rays
on bacteriophage multiplication.
29. 1951 : Family planning programme started in India.
30. 1952 : Hershey & Chase-experiment on bacteriophage or Bacterial virus
gives unequivocal proof that DNA is the genetic material.
31. 1953 : Miller experiment - Methane, ammonia, hydrogen & water
vapour.
32. 1953 : Watson & Crick - Double helical structure of B-DNA &
replication scheme.
33. 1953 : Palade : Discovered ribosome.
34. 1954 : Ramachandran - Triple helical model of collagen, published
in Nature.
35. 1954 : Crick complete d Ph.D. on a thesis “X-rays diffraction :
polypeptides and proteins.
36. 1958 : Meselson & Stahl - Work on E.coli proves semiconservative
replication of DNA in prokaryotes.
37. 1958 : Taylor - Work on Vicia faba proves semiconservative replication
of DNA in eukaryotes.
38. 1960 : Katherine Esau - Published “Anatomy of Seed Plants.”
39. 1961 : Melvin Calvin - Nobel Prize.
40. 1962 : Watson, Crick and Wilikins - Nobel Prize.
41. 1963 : Wheat varieties (Sonalika & Kalyan sona) introduced.
42. 1963 : Two enzyme responsible for restricting growth of bacteriophage
in E.coli were isolated.
43. 1966 : Derivative of IR-8 & Taichung native-I introduced.
44. 1969 : Whittaker - Five kingdom classification.
45. 1971 : Govt. of India legalized MTP.
46. 1971 : Diener- Discovered Viroid(free RNA without capsid).
47. 1972 : Singer & Nicolson - Fluid mosaic model.
48. 1972 : Stanley Cohen & Herbert Boyer - Formed Ist recombinant DNA.
49. 1972 : Establishme nt of NCEPC - National Committe e for
Environmental Planning & Coordination.
50. 1974 : Water act.
51. 1980 : Joint forest management, (JFM).
52. 1981 : AIDS was Ist reported.
53. 1981 : Air act.
54. 1983 : Eli Lily (An American company) produces insulin in E.coli by
recombinant DNA technology.
55. 1984 : Establishment of MOEF : Ministry of Environment & Forest.
56. 1986 : Environment Protection Act.
57. 1987 : Montreal protocol. Held in Montreal, Canada.

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🚨🚨🚨Types of Teeth and Their Functions

There are 4 types of teeth in the oral cavity:

✅✅Incisors –

The four front teeth in both the upper and lower jaws are called incisors.  Their primary function is to cut food.  The two incisors on either side of the midline are known as central incisors.  The two adjacent teeth to the central incisors are known as the lateral incisors.  Incisors have a single root and a sharp incisal edge.

✅✅Canines –

There are four canines in the oral cavity. Two in the maxillary arch and two in the mandibular area.  They are behind and adjacent to the lateral incisors.  Their main function is to tear food.  They have a single, pointed cusp and a single root.  They have the longest root of any tooth.  They also serve to form the corners of the mouth.

✅✅Premolars (Bicuspids) –

These teeth are located behind and adjacent to the canines and are designed to crush food.  There are eight premolars in the oral cavity.  There are two in each quadrant of the mouth.  The one closest to the midline is the first premolar and the one farthest from the midline is the second premolar.  These teeth can have 3-4 cusps.  The maxillary first premolar has two roots, and the remaining premolars have a single root.  There are no premolars in the primary dentition.

✅✅Molars –

The most posterior teeth in the mouth are the molars.  They have broader and flatter surfaces with 4-5 cusps.  They are designed to grind food.  Mandibular molars typically have 2 roots.  Maxillary molars, which are located behind the second premolars, typically have 3 roots.  There are 12 molars in the permanent dentition with three in each quadrant of the mouth.  They are named starting with closest to the midline as first molars, second molars and third molars.  Although, some people do not fully develop the third molars.  Third molars are often referred to as wisdom teeth.  The primary dentition only contains eight molars.

✅ Characteristics of Fungi

➖ Fungi are eukaryotic, non-vascular, non-motile and heterotrophic organisms.
➖ They may be unicellular or filamentous.
➖ They reproduce by means of spores.
➖ Fungi exhibit the phenomenon of alternation of generation.
➖ Fungi lack chlorophyll and hence cannot perform photosynthesis.
➖ Fungi store their food in the form of starch.
➖ Biosynthesis of chitin occurs in fungi.
➖ The nuclei of the fungi are very small.
➖ The fungi have no embryonic stage. They develop from the spores.
➖ The mode of reproduction is sexual or asexual.
➖ Some fungi are parasitic and can infect the host.
➖ Fungi produce a chemical called pheromone which leads to sexual reproduction in fungi.
➖ Examples include mushrooms, moulds and yeast.

ANATOMY LENGTHS

4cm long structures in the body
👉Inguinal canal
👉Anal canal
👉Female urethra
👉Auditory tube
👉Cystic duct
👉Optic nerve
👉Prostatic urethra
👉Left principle bronchus

5cm long structures in the body
👉Male larynx
👉Left primary bronchus
👉Parotid duct
👉Submandibular duct
👉Lateral lobe of thyroid gland
👉Testis
👉First part of duodenum
👉Neck of femur
👉Lateral wall of bony orbit
👉Medial wall of bony orbit

7.5cm long structures in the body
👉Anterior wall of vagina
👉Virgin uterus
👉Second part of duodenum
👉Bile duct

9cm long structures in the body
👉Appendix
👉Multiparous uterus
👉Posterior wall of vagina

11cm long structures in the body
👉Trachea
👉Kidney
👉Uterine tube
👉Third part of duodenum

12cm long structures in the body
👉Rectum
👉Spleen
👉Pharynx

15cm long structures in the body
👉Adductor canal
👉Ascending colon
👉Pancreas
👉Root of mesentery

25cm long structures in the body
👉Oesophagus
👉Descending colon
👉Ureter
👉Duodenum

45cm long structures in the body
👉Spinal cord
👉Thoracic duct
👉Transverse colon
👉Femur
👉Sartorius
👉Vas deferens

🌺Revision Notes on Sexual Reproduction in Flowering Plants🌺

(3) Entry of pollen tube into embryo sac:

The pollen tube enters the embryo sac only from the micropylar end irrespective of its mode of entry into the ovule. The pollen tube either passes between a synergid and the egg cell or enters into one of the synergids through filiform apparatus. The synergids direct the growth of pollen tube by secreting some chemical substances (chemotropic secretion). The tip of pollen tube enters into one synergid. The penetrated synergid starts degenerating. After penetration, the tip of pollen tube enlarges and ruptures releasing most of its contents including the two male gametes and the vegetative nucleus into the synergid.

(4) Double fertilization:

The nuclei of both the male gametes are released in the embryo sac. One male gamete fuses with the egg to form the diploid zygote. The process is called syngamy or generative fertilization. This syngamy was discovered by Strasburger (1884). The diploid zygote finally develops into embryo. The other male gamete fuses with the two polar nuclei (or secondary nucleus) to form the triploid primary endosperm nucleus. The process is called triple fusion or vegetative fertilization. These two acts of fertilizations constitute the process of double fertilization. The process was discovered by S.G. Nawaschin (1898) and Guignard in Lilium and Frittillaria. Double fertilization occurs in angiosperms only.

🌺Revision Notes on Sexual Reproduction in Flowering Plants🌺

(5) Post-pollination development:

(a) The liberated pollen grains are transferred to the receptive surface of the carpel (i.e., stigma) by the process called pollination.

(b) On the stigma, the pollen grain absorbs water and swells within a few minutes.

(c) The vegetative (or tube) cell enlarges and comes out through one of the apertures in the form of a pollen tube.

(d) The wall of pollen tube is the extension of intine. The tube secretes exogenous pectinases and other hydrolytic enzymes to create a passage for its entry.

(e) The vegetative and generative nuclei are carried by the pollen tube, the farmer lying at its tip.

(f) The generative cell divides to form two non-motile male gametes.

(g) The tube nucleus has no important function and may disintegrate.

Megasporogenesis
The process of formation of megaspore from megaspore mother cell by meiotic division is known as megasporogenesis. This process takes place in ovule.

Structure and Functions of Parts of An Ovule(1) Structure of ovule:

Ovule is considered to be an integumented megasporangium. The ovule consists of the stalk and the body. The stalk is called funicle. One end of the funicle is attached to placenta and the other end to the body of the ovule. The point of attachment of funicle with the body is called hilum. Sometimes funicle gets fused with the body of the ovule one side and forms a ridge known as raphe. The body of the ovule shows two ends: the basal end, often called the chalazal end and the upper end is called micropylar end. The main body of the ovule is covered with one or two envelopes called integuments. These leave an opening at the top of the ovule called micropyle. The integuments enclose a large parenchymatous tissue known as nucellus.

(2) Development of female gametophyte (Megagametogenesis):

The process of development of female gametophyte or embryo sac from megaspore is called megagametogenesis.

(i) Monosporic type (Polygonum): In this type, only one megaspore situated towards chalazal end takes part in the development of embryo sac.

(ii) Bisporic type: In this type two megaspore nuclei take part in embryo sac formation.

(iii) Tetrasporic type: This type of embryo sac develops from four megaspore nuclei.

Pollination
(1) The process of transfer of pollen grains from an anther to the stigma of the same flower or of different flower.

(2) It is of two types:

(i) Self pollination: This process involves the transfer of pollen grains from the anthers to the stigma of the same flower or of another flower borne by the same plant.

(ii) Cross pollination: Cross pollination involves the transfer of pollen grains from the flower of one plant to the stigma of the flower of another plant. It is also called xenogamy.

Fertilization
The fusion of two dissimilar sexual reproductive units (gametes) is called fertilization. This process was discovered by Strasburger (1884).

(1) Germination of pollen grain on stigma and growth of pollen tube:

Pollen grains reach the receptive stigma of the carpel by the act of pollination. Pollen grains, after getting attached to the stigma, absorb water and swell. Subsequent to mutual recognition and acceptance of pollen grains, the pollen grain germinates (in vivo) to produce a pollen tube which grows into stigma towards the ovarian cavity.

(2) Entry of pollen tube into ovule:

After reaching ovary, the pollen tube enters the ovule. Pollen tube may enter the ovule by any one of the following routes:

(i) Porogamy: When the pollen tube enters the ovule through micropyle, it is called porogamy. It is the most common type. e.g. Lily.

(ii) Chalazogamy: The entry of pollen tube into the ovule from chalazal region is known as chalazogamy. Chalazogamy is less common. e.g. Casuarina, Juglans, Betula, etc. It was first observed by Treub (1981) in Casuarina.

(iii) Mesogamy: The pollen tube enters the ovule through its middle part i.e. through integument (e.g. Cucurbita, Populus) or through funicle (e.g. Pistacia).

🌺Revision Notes on Sexual Reproduction in Flowering Plants🌺

Microsporogenesis
The process of the formation and differentiation of microspores (pollen grains) from microspore mother cells (MMC) by reductional division is called microsporogenesis.

Microsporogenesis is well studied under following heads:

T.S. of a Mature Anther- Structure of anther:

The fertile portion of stamens is called anther. Each anther is usually made up of two lobes connected by a connective. In turn each anther lobe contains two pollen chambers placed longitudinally. Each pollen chamber represents a microsporangium and is filled with a large number of pollen grains or microspores.

The pollen sacs are surrounded by following 4 layers :

(i) Epidermis: This is the outermost single layered and protective. In Arceuthobium, cells of epidermis develop a fibrous thickening and the epidermis is designated as exothecium.

(ii) Endothecium: Inner to epidermis, there is a single layer of radially elongated cells. Cells of endothecium develop fibrous thickening (made up of cellulose with a little pectin and lignin) which help in the dehiscence of anther. In between these cells, a few cells without thickening are also present. These thick walled cells collectively form the stomium.

(iii) Middle layer: Three to four layers of thin walled cells situated just below the endothecium are known as middle layers. Cells of this layer are ephemeral and degenerate to provide nourishment to growing microspore mother cells.

(iv) Tarentum: This is the innermost layer of the wall. The cells are multinucleate (undergo endopolyploidy) and polyploid. Tapetal cells are nutritive.

(2) Development of anther and formation of microspores (Pollen grains):

(a) The young anther consists of homogenous mass of paranchymatous cells surrounded by epidermis. It soon becomes four lobed.

(b) In each of the four lobes, some of the hypodermal cells begin to act as archesporial initials.

(c) Each archesporial initial divides into an outer primary parietal cell and an inner primary sporogenous cell.

(d) The primary parietal cell divides to form 3-5 wall layers, i.e., endothecium, middle layers and tapetum.

(e) The primary sporogenous cells divide to produce a mass of sporogenous cells or microsporocytes.

(f) Each microspore mother cell divides meiotically to form four haploid microspores or pollen grains and remains arranged in tetrads.

(3) Development of male gametophyte (Microgametogenesis):

(a) Microspore or pollen grain is the first cell of male gametophyte (partially developed).

(b) The wall of the pollen grain is made of two layers.The outer layer is called exine. It is made up of sporopollenin (derived from carotenoid). The inner intine is thin, delicate and is made of cellulose and pectose.

(4) Pre-pollination development:

(a) Microspores start germinating in situ (i.e. while enclosed inside the microsporangium or pollen sac) and are called precocious.

(b) Microspore nucleus divides mitotically to form a smaller generative cell lying next to spore wall and a much larger vegetative cell (or tube cell).

(c) A callose layer is deposited around the generative cell. The generative cell loses its contact with the wall of microspore and becomes free in the cytoplasm.

(d) The callose layer then dissolves. The pollen grains are shed from the anther at this bicelled stage (rarely three celled).

🌺Revision Notes on Sexual Reproduction in Flowering Plants🌺


🌺Flower
Flower is a modified stem which functions as a reproductive organ and produces ova and/or pollen

(1) Structure of the flower:

The flower is commonly borne on short or long stalk called the pedicel. It has an upper swollen region known as receptacle (thalamus or torus).

Structure and Functions of parts of a flower Parts of a flower:

A typical angiospermic flower consists of four whorls of floral appendages attached on the receptacle: calyx, corolla, androecium and gynoecium.

(i) Calyx: It is the outermost whorl of the flower. It is composed of leaf like green sepals. The sepals are essentially green in colour but in some cases they are coloured like petals. Such a condition of calyx is called petaloid.

(ii) Corolla: This is the second whorl of the flower and consists of a number of petals. Petals are generally brightly coloured and sometimes fragrant which make the flower to become attractive.

(iii) Androecium: It is the third whorl of flower and is the male reproductive organ consisting of stamens. Each stamen is made of filament and anther. The filament supports anther at its tip.

(iv) Gynoecium: This is the last and the fourth whorl of flower and is the female reproductive organ of the flower. It occupies the central position on the receptacle and composed of ovary, style and stigma and the component parts are called carpels.

(3) Functions of a flower

(i) Flowers are modifications of shoot to perform the function of sexual reproduction.

(ii) Flowers of most of the angiosperms are shaped variously to help diverse modes of pollination.

(iii) Flowers provide seat for germination of pollen, development of pollen tube, formation of gametes and fertilization.

(iv) The ovary part of the carpel gets transformed into fruit and the ovules are transformed into seeds after fertilization.

(v) Some floral parts like calyx and various modifications in ovaries help in the dispersal of fruits and seeds.

❇️ Circulatory system ❇️

(a) Open type – In which the blood is pumped out of heart and the cells & tissues are directly bathed in it.
e.g. Arthropods, Molluscs, Echinoderms, Hemichordates and some lower Chordates like tunicates

(b) Closed type – In which the blood is circulated through a series of vessels of varying diameters i.e. arteries, veins and blood capillaries
e.g. Annelids, Cephalopod molluscs, Vertebrates etc

❇️Notochord ❇️
It is a mesodermally derived rod-like structure formed on the dorsal side during embryonic
development in some animals

(a) Non-chordates – Animals without notochord e.g. Porifera to Echinodermata

(b) Chordates – Animals with notochord e.g. Chordata

❇️Body Cavity or Coelom ❇️

Presence or absence of a cavity between the body wall and gut wall is very important in classification.

(a) Acoelomates – Animals in which the body cavity is absent
e.g. Porifera, Coelenterata, Ctennophora, Platyhelminthes

(b) Pseudocoelomates – In same animals body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Such a body cavity is called pseudocoelom.
e.g. Aschelminthes.

(c) Coelomates – Animals possessing coelom i.e. the body cavity which is lined by mesoderm on all sides

❇️Symmetry ❇️

(a) Asymmetry :- When any plane that passes through the centre does not divide the body of animals into two equal halves.
e.g : most of the sponges are asymmetrical.

(b) Radial symmetry : When any plane passing through the central axis of the body divide the animal into two identical halves.
e.g : Coelenterates, Ctenophores and Echinoderms(adult)

(c) Bilateral symmetry : When the body can be divided into identical left & right halves in only one plane.
e.g : Platyhelminthes to Chordates.

❇️ Germinal layers ❇️

(a) Diploblastic – Animals in which the cells are arragned in two embryonic layers ectoderm and endoderm with an interveining undifferentiated mesoglea e.g. Coelenterates and Ctenophores.

(b) Triploblastic – Those animals in which the developing embryo has a third germinal layer–Mesoderm in between the ectoderm and endoderm e.g. Platyhelminthes to Chordates

Blood Groups: ABO

✅ABO grouping is based on the presence or absence of two surface antigens (chemicals that can induce immune response) on the RBCs namely A and B.

✅Similarly, the plasma of different individuals contain two natural antibodies (proteins produced in response to antigens).

✅ABO blood groups are controlled by the gene I. The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by the gene. The gene (I) has three alleles IA, IB and i.

✅The alleles IA and IB produce a slightly different form of the sugar while allele i does not produce any sugar.

✅Because humans are diploid organisms, each person possesses any two of the three I gene alleles.

✅IA and IB are completely dominant over i, in other words when IA and i are present only IA expresses (because i does not produce any sugar), and when IB and i are present IB expresses.

✅But when IA and IB are present together they both express their own types of sugars: this is because of co-dominance. Hence red blood cells have both A and B types of sugars.