The human immunodeficiency virus belongs to the genus Lentivirus. When observed under the electron microscope, HIV is seen as a spherical virus, 100-120 nm in diameter, containing a dense core surrounded by a lipoprotein envelope. The envelope has .glycoprotein (GP) spikes termed GP 41 and GP 120. At the core, there are two large single-stranded RNA. Attached to the RNA are molecules of reverse transcripte. It also contains enzymes like protease and ribonuclease. The core is covered by a capsid made of proteins. This is followed by another layer of matrix proteins as shown above.

German Naturalist and Geographer Alexander von Humboldt explored the wilderness of south American jungles and found that within a region the species richness increased with increasing area but upto a certain limit. The relationship between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats and freshwater fishes) turned out to be the rectangular hyperbola. On a logarithmic scale, the relationship is a straight line described by the equation.
where
log S = log C + Z log A
S = Species richness
A = Area
Z = Slope of the line
(regression coefficient)
C = Y-intercept
Regression coefficient Z generally has a value of 0.1-0.2 regardless of taxonomic group or region. However, in case of the species - area relationship in very large areas like entire continents; the slope of the line appears to be much steeper (Z-value in the range of 0.6-1.2). For example, in case of the fruit eating (frugivorous) birds and mammals in the tropical forests of different continents, the slope is found to be a steeper line.

1. Transgenesis is a powerful tool to study gene expression and developmental processes in higher organisms.
2. Transgenesis helps in the improvement of genetic characters in animals. Transgenic animals serve as good models for understanding human diseases which help in the investigation of new treatments for diseases. Transgenic models exist for many human diseases such as cancer, Alzheimer's, cystic fibrosis, rheumatoid arthritis and sickle cell anemia.
3. Transgenic animals are used to produce proteins which are important for medical and pharmaceutical applications.
4. Transgenic mice are used for testing the safety of vaccines.
5. Transgenic animals are used for testing toxicity in animals that carry genes which make them sensitive to toxic substances than non-transgenic animals exposed to toxic substances and their effects are studied.
6. Transgenesis is important for improving the quality and quantity of milk, meat, eggs and wool production in addition to testing drug resistance.

(i) Urey and Miller (1953), paved way for understanding the possible synthesis of organic compounds that led to the appearance of living organisms.

(ii) In their experiment, a mixture of gases was allowed to circulate over electric discharge from a tungsten electrode.
(iii) A small flask was kept boiling and the steam emanating from it was made to mix with the mixture of gases (ammonia, methane, and hydrogen) in the large chamber that was connected to the boiling water. The steam condensed to form water which ran down the 'U' tube.
(iv) The experiment was conducted continuously for a week and the liquid was analyzed. Glycine, alanine, beta-alanine, and aspartic A acid were identified. Thus Miller's experiments highlighted the possibility of abiogenetic synthesis of a large amount of variety of organic compounds in nature from a mixture of sample gases in which the only source of carbon was methane. Later in similar experiments, formation of all types of amino acids, and nitrogen bases were noticed.

cervial cancer: Cervical cancer is caused by a sexually transmitted virus called Human Papilloma virus (HPV). HPV may cause abnormal growth of cervical cells or cervical dysplasia.
The most common symptoms and signs of cervical cancer are pelvic pain, increased vaginal discharge and abnormal vaginal bleeding. The risk factors for cervical cancer include
(i) Having multiple sexual partners
(ii) Prolonged use of contraceptive pills
Cervical cancer can be diagnosed by a Papanicolaou smear (PAP smear) combined With an HPV test. X-Ray, CT scan, MRI and a PET scan may also be used to determine the stage of cancer. The treatment options for cervical. cancer include radiation therapy, surgery and chemotherapy.
Modern screening techniques can detect precancerous changes in the cervix. Therefore screening is recommended for women above 30 years once in a year. Cervical cancer can be prevented with vaccination. Primary prevention begins with HPV vaccination of girls aged 9 - 13 years, before they become sexually active. Modification in lifestyle can also help in preventing cervical cancer. Healthy diet, avoiding tobacco usage, preventing early marriages, practicing monogamy and regular exercise minimize the risk of cervical cancer.

(i) DNA acts as a genetic material. However, in some viruses like Tobacco mosaic virus (TMV), bacteriophage θB, RNA acts as the genetic material. A molecule that can act as a genetic material should have the following properties:
(ii) Self Replication: It should be able to replicate. According to the rule of base pairing and complementarity, both nucleic acids (DNA and RNA) have the ability to direct duplications. Proteins fail to fulfill this criteria.
(iii) It should be stable structurally and chemically. The genetic material should be stable enough not to change with different stages of life cycle, age or with change in physiology of the organism.
(iv) Griffith's transforming principle, Heat which killed the bacteria did not destroy some of the properties of genetic material. In DNA the two strands being complementary, if separated (denatured) by heating can come together (renaturation) when appropriate condition is provided.
(v) Further 2' OH group present at every nucleotide in RNA is a reactive group that makes RNA liable and easily degradable. RNA is also known to be catalytic and reactive.
(vi) Hence DNA is chemically more stable and chemically less reactive when compared to RNA.
(vii) Presence of thymine instead of uracil in DNA confers additional stability to DNA.
(viii) It should be able to express itself in the form of Mendelian characters ', RNA can directly code for protein synthesis DNA, however depends on RNA for synthesis of proteins.
(ix) Both DNA and RNA can act as a genetic material, but DNA- being more stable stores the genetic information and RNA transfers the genetic information
(x) Variation through mutation: It should be able to mutate. Both DNA and RNA are able to mutate. RNA being unstable, mutates at a faster rate.

(i) Development of an egg into a complete individual without fertilization is known as parthenogenesis.
(ii) It was first discovered by Charles Bonnet in 1745. Parthenogenesis is of two main types namely, natural Parthenogenesis and artificial Parthenogenesis.
(iii) In certain animals, parthenogenesis occurs regularly, constantly and naturally in their life cycle and is known as natural parthenogenesis.
Natural parthenogenesis are of different types:
a) Arrhenotoky: In this type only males are produced by parthenogenesis. E.g: honey bees
b) Thelytoky: In this type of parthenogenesis only females are produced by parthenogenesis E.g. Solenobia
c) Amphitoky: In this type parthenogenetic egg may develop into individuals of any sex. E.g: Aphis.
(iv) Natural parthenogenesis may be of two types, viz., complete and incomplete. Complete parthenogenesis is the only form of reproduction in certain animals and there is no biparental sexual reproduction. These are no male organisms and so, such individuals are represented by females only.
(v) Incomplete parthenogenesis is found in some animals in which both sexual reproduction and parthenogenesis occurs.
E.g. In honeybees; fertilized eggs (zygotes) develop into queen and workers, whereas unfertilized eggs develop into drones (male).
(vi) In paedogenetic parthenogenesis (paedogenesis) the larvae produce a new generation of larvae by parthenogenesis.
(vii) It occurs in the sporocysts and Redia larvae of liver fluke. It is also seen in the larvae of some insects. E.g. Gall fly.
(viii) In artifical parthenogenesis, the unfertilized egg (ovum) is induced to develop into a complete individual by physical or chemical stimuli. E.g. Annelid and seaurchin eggs.

The plants which are living in dry or xeric condition are known as Xerophytes.
Xerophytic habitat can be of two different types They are:
(a) physical dryness: In these habitats, soil has a little amount of water due to the inability of the soil to hold water because of low rainfall.
(b) physiological dryness: In these habitats, water is sufficiently present but plants are unable to absorb it because of the absence of capillary spaces. Example: Plants in salty and acidic soil.
Based on adaptive characters xerophytes are classified into three categories. They are Ephemerals, Succulents and Non - succulent plants.

(i) Ephemerals: These are also called drought escapers or drought evaders. These plants complete their life cycle within a short period (single season). These are not true xerophytes. Examples: Argemone, Mollugo, Tribulus and Tephrosia.
(ii) Succulents: These are also called drought enduring plants. These plants store water in their plant parts during the dry period. These plants develop certain adaptive characters to resist extreme ,drought conditions. Examples: Opuntia, Aloe, Bryophyllum and Begonia.
(iii) Non succulents: These are also called drought resistant plants ( true xerophytes). They face both external and internal dryness. They have many adaptations to resist dry conditions. Examples: Casuarina, Nerium, Zizyphus and Acacia.

Soil is commonly stratified into horizons at different depth. These layers differ in their physical, chemical and biological properties. This succession of super-imposed horizons is called soil profile.
Horizon Description O-Horizon (Organic horizon) Humus It consists of fresh or partially decomposed organic matter.
01 - Freshly fallen leaves, twigs, flowers and fruits.
02 - Dead plants, animals and their excreta decomposed by micro-organisms.
Usually absent in agricultural and deserts. A-Horizon
(Leached horizon)
Topsoil - Often rich in humus and minerals. It consists of top soil with humus, living creatures and in-organic minerals.
A1 - Dark and rich in organic matter because of mixture of organic and mineral matters.
A2 - Light coloured layer with large sized mineral particles. B-Horizon (Accumulation horizon) (Subsoil - Poor in humus, rich in minerals) It consists of iron, aluminium and silica rich clay organic compounds. C - Horizon (partially weathered horizon) Weathered rock Fragments - Little or no plant or animal life. It consists of parent materials of soil, composed of little amount of organic matters without life forms. R-Horizon (Parent material) Bedrock It is a parent bed rock upon which underground water is found.

1. In 1997, Rosie, the first transgenic cow produced human protein enriched milk, which contained the human alpha lactalbumin.
2. Alpha lactalbumin is a protein composed of 123 amino acidic and 4 disulphide bridges, with a molecular weight of 14178 Da.
3. In human milk, & lactalbumin is the most abundant protein comprising 25% of total protein found in human milk.
4. It is synthesized by the mammary glands & lactalbumin binds calcium and zinc ions and possesses bactericidal antitumor activities.

Advantages of Herbicide Tolerant Crops:
1. Weed control improves higher crop yields;
2. Reduces spray of herbicide;
3. Reduces competition between crop plant and weed;
4. Use of low toxicity compounds which do not remain active in the soil; and
5. The ability to conserve soil structure and microbes.

The diagrammatic representation of position of genes and related distances between the adjacent genes is called gene mapping. 
Uses 
(i) Used to determine gene order.
(i) Identify the locus of a gene.
(i) Calculate the distance between genes.
(i) Useful in predicting results of dihybrid and trihybrid crosses.
(i) Allows the geneticists to understand the overall genetic complexity of particular organism.

(i) Complete Linkage
(ii)
 
(iii) Observed ratio 1:1 

The fusion of male and female gamete is called fertilization. Fertilization in angiosperms is double fertilization type.
Pollen germinates on the stigma. Pollen tube produced grows through the style towards the micropyle of the ovule pollen tubes enter into one of the synergids of the embryo sac.
Discharge of male gametes occur syngamy - one gamete and an egg cell fuses to form diploid zygote Triple fusion - The other male gamete fuses with the two haploid female polar nuclei. A triploid primary endosperm nucleus results.

(i) Flower size Generally large
(ii) It small - aggregated to dense in florescence (eg) Asteraceae flower
(iii) Flower colour - brightly coloured
(iv) The adjacent parts of flower may also be brightly coloured (eg) Coloured bracts of Poinsettia, Bougainvillea
(v) Secretions - Scent, nectar
(vi) Flowers - if no secretion of nectar
(vii) Pollen - Consumed as food or used up to build hives
(viii) Production of foul odour - attracts flies and Beetles
(ix) Presence of juicy cells - juice sucked by insects.
(x) The above characteristic features of entomophilous flowers bring about successful pollination by insects.

CSS - Carbon Capture and Storage.

There is a gradual decrease in energy transfer at successive tropic levels from producers to higher levels, hence the pyramid of energy is always upright.

A desert has little or no plant life without plants, there is no organic horizon in the soil leading to a low level of water retention that is unsuitable for plant growth.

Green House Effect and Global warming:
Natural environment and climate are dynamic and keep changing over course of time. Reasons for climate change
a) Human population growth
b) Industrialization
c) Associated anthropological activities the changes.
Impact on Global Warming:
(i) Large-scale changes of global environment can lead to hazards, which may include climate change, stratospheric ozone depletion, changes in ecosystems due to loss of biodiversity, changes in hydrological systems and the supplies of freshwater, land degradation, urbanization, and stress on food-producing systems.
(ii) Greenhouse gases (GHG) water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs) causes greenhouse effect. The absorbed energy warms the atmosphere and the surface of the Earth
(iii) Global warming will have a significant impact on people and nature. As global average temperatures rise, precipitation patterns could be affected. Extreme wet and dry conditions can be expected (flooding and desertification). Coastal areas shall become more vulnerable to storm surges as sea level rises. Plant and animal species will migrate or disappear in response to climate change.
(iv) Global warming can directly affect the flora and fauna. This could also result in shortage of food and even lead to a food crisis and affect the health of the people and organisms.
Control Measures:
The UNO has several measures to control or reduce pollution. Through various conventions organized by UNO, the countries assured to take steps to control or reduce emissions by factories and automobiles.

Name of the process-Plant tissue culture Types:
(a) Organ culture
(b) Meristem culture
(c) Protoplast culture
(d) Cell culture

Methane, carbondioxide, ammonia and water vapour.

Parthenogenesis is the phenomenon in which female gamete directly develops into a new organism. (e,g:) Honeybee (male or drone).

A true breeding lines means it has undergone continuous self pollination having stable trait inheritance from parent to off spring. 

(a) A and R are true, R is the correct explanation of A

D. If both A and R are false.

(i) Placenta is a temporary endocrine formed during pregnancy
(ii) It connects the foetus to the uterine through the umbilical cord.
(ii) It is the organ by which the nutri respiratory and excretory functions fulfilled.

Initiation of translation in E. coli begins with the formation of an initiation complex, consisting of the 30S subunits of the ribosome, a messenger RNA and the charged N-formyl methionine tRNA (f^met - t RNA f^met), three proteinaceous initiation factors (IF 1, IF2, IF3), GTP (Guanine Tri Phosphate) and Mg²⁺.

If the mother is Rh negative and foetus is Rh positive, anti D antibodies should be administered to the mother at 28th and 34th week of gestation as a prophylactic measure. If the Rh negative mother delivers Rh positive child then anti D antibodies should be administered to the mother soon after delivery. This develops passive immunity and prevents the formation of anti D antibodies in the mother's blood by destroying the Rh foetal RBC before the mother's immune system is sensitized. This has to be done whenever the woman attains pregnancy.

After ovulation, the Graafian follicle turns into corpus luteum (a transitory endocrine gland) which secrets progesterone. Progesterone maintains endometrium for implantation of a fertilized ovum. the endometrium of uterus also secretes nutritious fluid for the foetus. Hence this phase is also referred to as secretory phase

(i) Interstitial cells of Leydig are seen embedded in the soft connective tissue surrounding the seminiferous tubules.
(ii) These cells are endocrine natured and produce testosterone (androgen).
(iii) These cells are characteristic to mammalian testes.

A - Neisseria Gonorrhoea
B - AIDS
C - Jaundice

Isogamy. Eg: Monocystis

The transfer of an embryo with more than 8 blastomeres stage into uterus is called embryo transfer technique.

(i) Monozygotic twins - single fertilized egg splits into two embryos. The individuals are of the same sex, look alike and share the same genes.
(ii) Dizygotic twins - Two eggs are fertilized by two sperms. The two individuals may or may not be of same sex and are nonidentical.
(iii) Siamese twins - conjoined twins joined during birth.

(i) It is a temporary endocrine gland formed from the ruptured Graafian follicle.
(ii) It secretes a large amount of progesterone which is essential for maintenance of the endometrium of the uterus. If fertilization does not occur it degenerates.

Termination is the third phase of translation Termination of protein synthesis occurs when one of the three stop codons appears in the 'A' site of the ribosome. (UAA, UAG, UGA)

A sequence of there mRNA bases represents a triplet codon. It is the sequence relationship between nucleotide in genes (mRNA) and the amino acids in the proteins they encode. There are 64 possible triplets.

(i) A gene, sex-lethal (SxL) located on the X chromosome, in Drosophila directs female development.
(ii) This gene has two states of activity. When it is 'on' it directs female development and when it is 'off maleness ensures.
(iii) Other genes located on the X chromosome and autosomes regulates sex switch gene.
(Iv) However, the Ychromosome of Drosophila is required for male fertility.

(i) A dominant X - linked gene is necessary for the formation of colour sensitive cells, the cones. which helps to distinguish colours.
(ii) A recessive form of the gene is incapable of producing the cones. Hence the affected person is unable to distinguish red and green colour.

(i) SRY stands for sex determining region Y.
(ii) It is a gene found in the euchromatin regions of the Non-combining region of Y chromosome.
(iii) It codes for testes determining factor (TDF) present in testes of Males. This gene does not occur in X chromosome.

(i) The proportion of the age groups in a population is its age distribution attribute.
(ii) This determines the reproductive status of the population at the given time and is an indicator of the future population size.
(iii) Usually a rapidly growing population will have larger proportion of young individuals.
(iv) A stable population will have an even distribution of various age classes.
(v) A declining population tends to have a larger proportion of older individuals

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.

1. Farmers need to be made aware about organic farming which does not require any kind of fertilizers and pesticides usage.
2. Crop rotation can be practiced by farmers which reduces the need for fertilizers and improves the fertility of the soil.
3. Ships and tankers that carry oil can be supervised earlier and ensured that they are not damaged in any way and through this oil will not be split in the ocean water.

(a) Transfer of an ovum collected from donor into the fallopian tube is called GIFT (Gamete Intra-fallopian transfer)
(b) Transferring of an embryo with more than 8 blastomeres into uterus is called IUT (Intra uterine transfer)
(c) Multi load 375 is a copper releasing IUD

During DNA replication, One acts as the leading strand and the other is the lagging strand.

Leading Strand	Lagging Strand
lt is continuously formed as replicated strand of DNA without any gap	It is replicated strand of DNA which is formed by the joining of short segments called okazaki segment
The growth of leading strand is in 5' → 3'direction	Each okazaki segment grows in 5' → 3'direction but the growth of the lagging strand is in 5' → 3'direction.
lt does not require DNA ligase for its growth and used in PCR	DNA ligase is required for the formation of lagging strand from okazaki segments

(i) The types of barriers which involve macrophages are phagocytic barriers
(ii) It is also known as cellular barriers.
(iii) Certain types of leucocytes (WBCs), such as polymerase nuclear leukocytes (PMNL) : neutrophils, monocytes and natural killer cells (a type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes.

1. Sexual reproduction is considered to be a better mode of reproduction because it creates a hybrid that has more vigor than the parents.
2. It also creates the variation in off springs making its survival better.
3. The fact that most of the eukaryotes reproduce sexually in evidence of its evolutionary success.
4. In many animals, it is actually the only mode of reproduction.