The Lac (Lactose) operon: The metabolism of lactose in E-coli requires three enzymes - permease, β-galactosidase (β-gal) and transacetylase. The enzyme permease is needed for entry of lactose into the cell, β-galactosidase brings about hydrolysis of lactose to glucose and galactose, while transacetylase transfers acetyl group from acetyl Co A to β-galactosidase. The lac operon consists of one regulator gene ('i' gene refers to inhibitor) promoter sites (P), and operator site (o). Besides these, it has three structural genes namely lac z, y and lac a. The lac 'z' gene codes for β-galactosidase, lac 'y' gene codes for permease and 'a' gene codes for transacetylase.
Jacob and Monod proposed the classical model of Lac operon to explain gene expression and regulation in E-coli. In lac operon, a polycistronic structural gene is regulated by a common promoter and regulatory gene. When the cell is using its normal energy source as glucose; the 'i' gene transcribes a repressor mRNA and after its translation, a repressor protein is produced. It binds to the operator region of the operon and prevents translation, as a result, β-galactosidase is not produced. In the absence of preferred carbon source such as glucose, if lactose is available as an energy source for the bacteria then lactose enters the cell as a result of permease enzyme. Lactose acts as an inducer and interacts with the repressor to inactivate it. The repressor protein binds to the operator of the operon and prevents RNA polymerase from transcribing the operon. In the presence of inducer, such as lactose or allolactose, the repressor is inactivated by interaction with the inducer. This allows RNA polymerase to bind to the promotor site and transcribe the operon to produce lac mRNA which enables formation of all the required enzymes needed for lactose metabolism. This regulation of lac operon by the repressor is an example of negative control of transcription initiation.

The German Botanist Carl Correns's (1905) Experiment - In 4 0' clock plant, Mirabilis jalapa when the pure breeding homozygous red (R¹ R¹) parent is crossed with homozygous white (R ²R²), the phenotype of the F₁ hybrid is heterozygous pink (R¹R²). The F₁ heterozygous phenotype differs from both the parental homozygous phenotype. This cross did not exhibit the character of the dominant parent but an intermediate colour pink. When one allele is not completely dominant to another allele it shows incomplete dominance. Such allelic interaction is known as incomplete dominance. F₁ generation produces intermediate phenotype pink coloured flower.
When pink coloured plants of F ₁ generation were interbred in F₂ both phenotypic and genotypic ratios were found to be identical as 1 : 2 : 1(1 red: 2 pink: 1 white). Genotypic ratio is 1 R¹R¹ : 2 R¹R² : 1 R²R². From this we conclude that the alleles themselves remain discrete and unaltered proving the Mendel's Law of Segregation. The phenotypic and genotypic ratios are the same. There is no blending of genes. In the F₂ generation R¹ and R² genes segregate and recombine to produce red, pink and white in the ratio of 1 : 2 : 1. R ¹ allele codes for an enzyme responsible for the formation of red pigment. R² allele codes for defective enzyme. R¹ and R² genotypes produce only enough red pigments to make the flower pink. Two R¹R¹ are needed for producing red flowers. Two R²R² genes are needed for white flowers. If blending had taken place, the original pure traits would not have appeared and all F₂ plants would have pink flowers. It is very clear that Mendel's particulate inheritance takes place in this cross which is confirmed by the reappearance of original phenotype in F₂.

Morphological adaptations:
Root system is extensively developed. These roots may be of two types. They are Clinging roots and Aerial roots.
Clinging roots fix the epiphytes firmly on the surface of the supporting objects.
Aerial roots are green coloured roots which may hang downwardly and absorb moisture from the atmosphere with the help of a spongy tissue called velamen.
1. Stem of some epiphytes are succulent and develop pseudo bulb or tuber.
2. Generally the leaves are lesser in number and may be fleshy and leathery.
3. Myrmecophily is a common occurrence in the epiphytic vegetation to prevent the predators
4. The fruits and seeds are very small and usually dispersed by wind, insects and birds.

Jute
Botanical name : Corchorus spp.
Family: Malvaceae
Origin and Area of cultivation: Jute is derived from the two cultivated species (1) Core horns capsularis and (2) Colittorius is of African origin whereas C. Capsularis, is believed to Indo Burmaese origin. It is an important cultivated commercial crop in Gangetic plains of India and Bangladesh.
Uses: It is one of the largest exported fibre material of India. The jute industry occupies an important place in the national economy Of India. Jute is used for 'safe' packaging in view of being natural, renewable, bio-degradable and eco-friendly product. It is used in bagging and wrapping textile. About 75% of the jute produced is used for manufacturing sacks and bags. It is also used in manufacture of blankets, rags, curtains etc. It is also being used as a textile fibre in recent years.

Rain Water Harvesting - RWH (Solution to water crisis - A ecological problem)
Rainwater harvesting is the accumulation and storage of rainwater for reuse in-site rather than allowing it to run off.
Rainwater can be collected from rivers, rooftops and the water collected is directed to a deep pit.
The water percolates and gets stored in the pit.
RWH is a sustainable water management practice implemented not only in the urban area but also in agricultural fields, which is an important economic cost-effective method for the future.


Environmental benefits of Rain Water Harvesting:
(i) Promotes adequacy of underground water and water conservation.
(ii) Mitigates the effect of drought.
(iii) Reduces soil erosion as surface run-off is reduced.
(iv) Reduces flood hazards.
(v) Improves groundwater quality and water table / decreases salinity.
(vi) No land is wasted for storage purpose and no population displacement is involved.
(vii) Storing water underground is an eco- friendly measure and a part of sustainable water storage strategy for local communities.

Grassland ecosystem : There is a gradual decrease in the number of organisms in each trophic level from producers to primary consumers and then to secondary consumers, and finally to tertiary consumers. Therefore pyramids of number in grassland ecosystem are always upright.

Sexually transmitted diseases (STD) or veneral diseases(VD) or Reproductive tract infections (RTI) are called as Sexually transmitted infections (STI).
Transmissions:
1. Normally STI are transmitted from person to person during intimate sexual contact with an infected partner.
2. Infections like Hepatitis-B and HIV are transmitted sexually as well as by sharing of infusion needles, surgical instruments, etc with infected people, blood transfusion (or) from infected mother to baby.
3. People in the age of 15 to 24years are prone to these infections.
4. The bacterial STI are gonorrhoea syphilis, chancroid, chlamydiasis and lymphogranuloma venereum.
5. The viral STI are genital herpes, genital warts Hepatitis-B and AIDS.
6. Trichomoniasis is a protozoan STI, and candidiasis is a fungal STI.

(i) The primary endosperm nucleus divides immediately after fertilization and develops into an endosperm.
(ii) It is a nutritive tissue, and regulatory structure by undergoing repeated mitosis to form triploid (3n) endosperm that nourishes the developing embryo. Depending upon the mode of development three types of endosperm are recognized.
1) Nuclear endosperm:
(i) Primary endosperm, (PEN) nucleus undergoes several mitotic divisions. There is no cell wall formation So free nuclear condition exists in the endosperm.
Example:
Coccinia, Capsella, Arachis
2) Cellular endosperm:
(i) Primary endosperm nucleus divides into two nuclei There is cell wall formation.
(ii) Subsequent division also follows cell wall formation. It is said to be cellular endosperm
Example:
Adoxa, Helianthus, Scoparia.
3) Helobial endosperm:
(i) Primary Endosperm Nucleus moves towards the base of embryo sac.
(ii) Divides into two nuclei cell wall formation occurs forming a large micropylar chamber and a small chalazal chamber.
(iii) The nucleus of micropylar chamber further undergoes several free nuclear divisions. The nucleus of the chalazal chamber may or may not divide.
Example:
Hydrilla, Vallisneria.

(i) AUG codes for Methionine
UUU codes for Phenylalanine
UGC codes for Cysteine
(ii) TAC sequence of DNA is transcribed to AUG
AAA sequence of DNA is transcribed to UUU
ACG sequence of DNA is transcribed to UGC

A sacred grove or sacred woods are any grove of trees that are of special religious importance to a particular culture. Sacred groves feature in various cultures throughout the world.

S. No.	Mendelian factors	Chromosomes behaviour
1.	Alleles of a factor occur in pair.	Chromosomes occur in pairs
2.	Similar or dissimilar alleles of a factor separate during the gamete formation.	The homologous chromosomes separate during meiosis.
3.	Mendelian factors can assort independently.	The paired chromosomes can separate independently during meiosis but the linked genes in the same chromosome normally do not assort independently.

1. Temperature affects the enzymatic action of all the bio-chemical reactions in a plant body.
2. Low temperature with high humidity can spread diseases to plants.
3. The varying temperature with moisture determines the distribution of the vegetation types.

China, India, South America, Mediterranean, Mesoamerica and South East Asia.

(i) Aurelia
(ii) The Significance is that Aurelia reproduces asexually by a special type of transverse fission called strobilation.

S. No. Natality Mortality 1. It refers to the number of births per unit
population per unit time. e.g., per thousand
individuals per year in humans. It refers to the number of deaths per unit population per unit time. e.g., per thousand individuals per year in humans. 2. It adds new members to the population It removes members from the population 3. It increases the size of population. It decreases the size of population 4 Natality adds to population density Mortality reduces density of population 5 It maintains continuity of population It maintains health of population 6 It is high when population size is small and low when population size is large. Mortality is low when population
size is small and high when population size is large

Aerosols with small particles is reflecting the solar radiation entering the atmosphere. This is known as Albedo effect.
Effects:
1. It reduces the temperature limits, photosynthesis & respiration.
2. The sulphur compounds are responsible for acid rain due to acidification of rain water and destroy the ozone.

(i) Protecting soil quality using organic materials and encouraging biological activity.
(ii) Indirect provision of crop nutrients using soil microorganisms.
(iii) Nitrogen fixation in soils using legumes.
(iv) Weed and pest control based on methods like crop rotation, biological diversity, natural predators, organic manures and suitable chemical, thermal and biological interventions.

Cryopreservation (- 195.C)
1. Cryopreservation, also known as Cryo conservation.
2. A process by which protoplasts, cells, tissues, organelles, organs, extracellular matrix, enzymes or any other biological materials are subjected to preservation by cooling to very low temperature of -196^oC using liquid nitrogen.
3. At this extreme low temperature any enzymatic or chemical activity of the biological material will be totally stopped and this leads to preservation of material in dormant status.
4. Later these materials can be activated by bringing to room temperature slowly for any experimental work.
5. Protective agents like dimethyl sulphoxide, glycerol or sucrose are added before cryopreservation Process.
6. These protective agents are called cryoprotectants, since they protect the cells, or tissues from the stress of freezing temperature.

Human Ovum
a - Vitelline membrane
b - Nucleus
c - Zona Pellucida
d - Corona radiata

Colostrum is the yellowish fluid produced from the mother's mammary glands during initial few days of location, after parturition.
Significance:
1. It has less lactose than milk and almost no fat, but it contains more proteins, vitamin A and minerals.
2. Colostrum is also rich in IgA antibodies.
3. This helps to protect the infant's digestive tract against bacterial infection.
4. Breast milk is the ideal food for infants as it contains all the constituents in suitable concentration and is easily digestable.
5. It is fully sufficient till about 6 months of age and all infants must be breast fed by the mother to ensure the growth of a healthy baby.

The phosphate functional group (PO₄) gives DNA and RNA the property of an- acid at physiological pH, hence the name nucleic acid.

Bursa of Fabricius is a primary lymphoid organ of birds. It is attached to the dorsal side of the cloaca. B lymphocytes mature in the bursa and bring about humoral immunity.

(a) A = Phenylalanine hydroxylase
(b) B = Tyrosinase

The Narcotics Control Bureau (NCB) is the nodal drug law enforcement and intelligence agency of India and is responsible for fighting drug trafficking and the abuse of illegal substances.

The different modes of asexual reproduction seen in animals are fission, sporulation, budding, gemmule formation, fragmentation and regeneration.

Interferons are a group of signalling proteins produced by virus infected cells. They interfere with viral replication and hence named interferons. A virus infected cell releases interferons which induce antiviral state in the uninfected cells. They are chemical mediators under physiological barriers offering Innate immunity.

(a) Trees provide micro climate for crops and maintain O₂ - CO₂ balance atmospheric temperature & relative humidity
(b) Suitable for dry land where rainfall is minimum hence it is a good system for alternate land use pattern

If all producers are removed from ecosystem We tend to face the following hurdles.
(i) The Ecosystem cannot be balanced
(ii) The interlocking pattern of food chain is broken
(iii) The movement of energy transfer among the food chain cannot be established
(iv) As the green plants occupying the first trophic level (T₁) are producers - it affects majority of the food chain