The age of fossils can be determined using two methods namely, relative dating and absolute dating. Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age. Absolute dating is used to determine the precise age of a fossil by using radiometric dating to measure the decay of isotopes.

(a) Replication (b) Translation (c) Splicing

A primer is a short stretch of RNA. It initiates the formation of new strand. The primer produces 3' -OH end on the sequence of ribonucleotides, to which deoxyribonucleotides are added to form a new strand.

Some populations, as in a population of small mammals, increase slowly at first then more rapidly and gradually slow down as environmental resistance increases whereby equilibrium is reached and maintained. Their growth is represented by S-shaped growth curve.

There are three main types of sources: point sources, non-point sources, leaks and spills. Point sources: Discharge of pollutants at specific locations through pipelines or sewers into the water body. Factory effluents, sewage, underground mines, oil wells, oil tankers and agriculture are common point sources.
Non-point sources: Sources that cannot be traced to a single site of discharge like acid rain, dumping of the plastics in water bodies and agriculture chemical run off are common examples.
Leaks and Spills: This occurs mostly due to ship collision, off shore oil rigs, oil leakages and discharges into sea.

The use of naturally occurring or genetically engineered microorganisms to reduce or degrade pollutants is called bioremediation. Bioremediation is less expensive and more sustainable than other remediations available. It is grouped into in-situ bioremediation (treatment of contaminated soil or water in the site) and ex-situ bioremediation (treatment of contaminated soil or water that is removed from the site and treated).

Tobacco is smoked, chewed and used as snuff. It increases the carbon monoxide content of blood and reduces the concentration of haem bound oxygen, thus causing oxygen deficiency in the body. Tobacco contains nicotine, carbon monoxide, and tars, which cause problems in the heart, lung and nervous system. Adrenal glands are stimulated by nicotine to release adrenaline and noradrenaline which increases blood pressure and heartbeat

In shifting cultivation, plots of natural tree vegetation are burnt away and the cleared patches are farmed for 2-3 seasons, after which their fertility reduces to a point where crop production is no longer profitable. The farmer then abandons this patch and cuts down a new patch of forest trees elsewhere for crop production. This system is practiced in north-eastern regions of India. When vast areas are cleared and burnt, it results in loss of forest cover, pollution and discharge of CO₂ which in turn attributes to loss of habitat and climate change which has an impact on the faunal diversity of that regions.

The PCR technique can also be used for amplifications of RNA in which case it is referred to as reverse transcription PCR (RT-PCR). In this process the RNA molecules (mRNA) must be converted to complementary DNA by the enzyme reverse transcriptase. The cDNA then serves as the template for PCR.

Phenylketonuria is an inborn error of Phenylalanine metabolism caused due to a pair of autosomal recessive genes. It is caused due to mutation in the gene PAH (phenylalanine hydroxylase gene) located on chromosome 12 for the hepatic enzyme "phenylalanine hydroxylase".
This enzyme is essential for the conversion of phenylalanine to tyrosine. Affected individual lacks this enzyme, so phenylalanine accumulates and gets converted to phenylpyruvic acid and other derivatives. It is characterized by severe mental retardation, light pigmentation of skin and hair. Phenylpyruvic acid is excreted in the urine.
Phenylalanine \(\underrightarrow { phenylalanine \ hydroxylase } \) Tyrosine

Bacillus megaterium.
Corynebacterium glutamicum.
Alcaligenes eutrophus.

Secondary metabolites are those which are not required for the vital life process of microbes, but have value added nature, this includes antibiotics e.g. -Amphotericin-B (Streptomyces nodosus) and Penicillin (Penicillium chryosogenum).

The follicular cells of egg are held together by an adhesive cementing substance called hyaluronic acid. The acrosomal membrane disintegrates releasing the proteolytic enzyme, hyaluronidase during sperm entry through the corona radiata and zona pellucida. This is called acrosomal reaction

(i) Sertoli cells are elongated and pyramidal cells.
(ii) They provide nourishment to sperm till maturation.
(iii) They secrete a hormone called inhibin which is involved in negative feedback control of sperm production.

Amniocentesis is generally performed in a pregnant woman between the 15th and 20th weeks of pregnancy by inserting a long, thin needle through the abdomen into the amniotic sac to withdraw a small sample of amniotic fluid. The amniotic fluid contains cells shed from the foetus.

After tetrad formation, crossing over occurs in pachytene stage. The non-sister chromatids of homologous pair make a contact at one or more points. These points of contact between non-sister chromatids of homologous chromosomes are called Chiasmata (singular-Chiasma). At chiasma, cross-shaped or X-shaped structures are formed, where breaking and rejoining of two chromatids occur. This results in reciprocal exchange of equal and corresponding segments between them.

Isogamy. Eg: Monocystis

(a) Arrhenotoky: In this type, only males are produced by parthenogenesis. eg: 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.

Autogamy is certain in cleistogamous flowers since they never open and expose the reproductive organs.

Male sterility found in pearl maize (Sorgum vulgare) is the best example for mitochondrial cytoplasmic inheritance. So it is called cytoplasmic male sterility. In this, male sterility is inherited maternally. The gene for cytoplasmic male sterility is found in the mitochondrial DNA.

(i) Bee pollen is a natural substance with high proteins, carbohydrate, and a trace amount of vitamins and minerals.
(ii) It is used as a dietary supplement as tablets.
(iii) It increases the performance of athletes, racehorses and also heals burn wounds.

The movement of decomposed, water soluble organic and inorganic compounds from the surface to the lower layer of soil or the carrying away of the same by water is called eluviation.

The interaction between organisms, when continues for generations, involves reciprocal changes in genetic and morphological characters of both organisms. This type of evolution is called Co-evolution. It is a kind of co-adaptation and mutual change among interactive species.
Examples:
1. Corolla length and proboscis length of butterflies and moths (Habenaria and Moth).
2. Bird's beak shape and flower shape and size.

Somaclonal variations: Somatic variations found in plants regenerated in vitro (i.e. variations found in leaf, stem, root, tuber or propagule).
Gametoclonal variations: Gametophytic variations found in plants regenerated in vitro gametic origin (i.e. variations found in gametes and gametophytes)

Green manuring helps to increase the content of nitrogen soil and also improves the structure and physical property of soil

(i) Water Packets
(ii) Plastic straws
(iii) Plastic carry bags
(iv) Thermocol cups
(v) Plastic coated paper plates
(vi) Plastic flags.

Cotton is one of the oldest cultivated crops of the world. It has been cultivated for about 8000 years both in new world and in old world. Commercial cotton comes from four cotton species: two from the new world and two from the old world.
(1) Gossypium hirsutum
(2) G.barbadense are the New world species and
(3) G. arboretum
(4) G. herbaceum are the old world species.
In India, cotton is cultivated in Gujarat, Maharashtra, Andhra Pradesh and Tamil Nadu.

In this type, hybrids are formed due to interspecific crosses but they are sterile due to the failure of the chromosomes to segregate normally during meiosis, example Mule (interspecific cross between a horse and donkey). It is a post zygotic isolation mechanism.

Genetic variation is the ALXl gene in the DNA of Darwin's finches is associated with variation in the beak shape. Mild mutation is the ALXl genes leads to phenotypic changes in the shape of the beak as in Darwin finches.

Acid rain is a form of precipitation that contains acidic components, such as sulfuric acid or nitric acid. It damages trees, crops and harms marine animals (coral reefs) and induces corrosion.

Inability to conceive or produce children even after unprotected sexual cohabitation is called infertility.
Causes of infertility:
(i) Pelvic inflammatory disease (PID), uterine fibroids and endometriosis are the most common causes of infertility in women.
(ii) Low body fat or anorexia in women. i.e. a psychiatric eating disorder characterised by the fear of gaining weight.
(iii) Under developed ovaries or testes.

The most serious aspect of the loss of biodiversity is the extinction of species. The unique information contained in its genetic material (DNA), and the niche it possesses are lost forever.

Streptomycin is a broad spectrum antibiotic isolated from the actinomycetes, Streptomyces griseus. It is bactericidal against both gram positive and gram negative bacteria, especially against Mycobacterium tuberculosis.

Sensitivity test is important before administering penicillin to a person.
(i) Hypersensitivity reaction is a major problem with the use of penicillin, resulting in nausea; vomiting, wheezing and ultimately cardiovascular collapse.
(ii) This can be prevented by checking the sensitivity reaction of the patient before administering the antibiotic

(i) Eurythermy can be an evolutionary advantage: adaptations to cold temperatures (cold-eurythemy) are seen as essential for the survival of species during ice ages.
(ii) The ability to survive in a wide range of temperatures increases a species ability to inhabit other areas, an advantage for natural selection.
(iii) Eurythermy is an aspect of thermoregulation in organisms.

(a) Human foetus within the uterus
(b) 1 - Umbilical cord
2 - Fallopian tube
3 - Amniotic fluid

(i) Menopause is the phase in a women's life when ovulation and menstruation stops.
(ii) The average age of menopause is 45-50 years. It indicates the permanent cessation of the primary functions of the ovaries.

(i) FSH stimulates testicular growth and enhances the production of Androgen Binding protein (ABP) by the sertoli cells and helps in the process of spermiogenesis.
(ii) LH acts on the Leydig cells and stimulates the synthesis of testosterone which in turn stimulates the process of spermatogenesis.

(i) Gene augmentation therpy :Insertion of DNA into the genome to replace the missing gene product
(ii) Gene inhibition therpy : Insertion of the anti sense gene which inhibits the expression of the dominant gene.

Several people complain of stomach discomfort or pain and trouble with bowel movements, causing diarrhoea. This is called irritable bowel syndrome and caused by stress or other illnesses

In some retroviruses that contain RNA as the genetic material (e.g. HIV), the flow of information is reversed. RNA synthesizes DNA by reverse transcription, then transcribed into mRNA by transcription and then into proteins by translation. This is called reverse transcription.

(i) During unfavorable conditions Amoeba withdraws its pseudopodia and secretes a three-layered, protective, chitinous cyst wall around it and becomes inactive. This phenomenon is called encystment.
(ii) When conditions become favourable, the encysted Amoeba divides by multiple fission and produces many minute amoebae called pseudopodiospore or amoebulae.
(iii) The cyst wall breaks off liberating the young pseudopodiospores.

(i) Rh incompatability has great significance' in child birth. If a woman is Rh negative and the man is Rh positive, the foetus may be Rh positive having inherited the factor from its father.
(ii) The Rh negative mother becomes sensitized by carrying Rh positive foetus within her body.
(iii) Due to damage of blood vessels, during child birth, the mother's immune system recognizes the Rh antigens and gets sensitized. The sensitized mother produces Rh antibodies.
(iv ) The antibodies are IgG type which are small and can cross placenta and enter the foetal circulation. By the time the mother gets sensitized and produce anti 'D' antibodies, the child is delivered.
(v) Usually no effects are associated with exposure of the mother to Rh positive antigen during the first child birth, subsequent Rh positive children carried by the same mother, may be exposed to antibodies produced by the mother against Rh antigen, which are carried across the placenta into the foetal blood circulation.
(vi) This causes haemolysis of foetal RBCs resulting in haemolytic jaundice and anaemia. This condition is known as Erythoblastosis foetalis or Haemolytic disease of the new born (HDN).

i) The genes present in the non-homologous region of the Y chromosome are called Y - linked genes or holandric genes.
ii) The Y-linked genes have no corresponding allele in X - chromosome.
iii) These genes are transmitted directly from father to son, because males inherit the Y chromosome from the father.
Iv) Eg. Gene for Hypertrichosis (excessive development of hairs on pinna of the ear).

In ABO blood group, each allele (I^A and I^B) produces a transferase enzyme. I^A allele produces N-acetyl galactose transferase and can add N-acetyl galactosamine (NAG) and Ballele encodes for the enzyme galactose transferase that adds galactose to the precursor (i.e. H substances) In the case of I^o/I^o allele no terminal transferase enzyme is produced and therefore called "null" allele arid hence cannot add NAG or galactose to the precursor.

Yes. Government of India legalized MTP in 1971 for medical necessity and social consequences with certain restrictions like sex discrimination and illegal female foeticides to avoid its misuse. MTP performed illegally by unqualified quacks is unsafe and could be fatal. MTP of the first conception may have serious psychological consequences

The tumor cells spread to other parts of the body from the tumour and give rise to secondary tumour. This is known as metastasis.