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• The smallest indivisible particle of an element is called an atom. 
• A molecule is an aggregate of two or more atoms of definite composition which are held together by chemical bonds. 
• Every atom of an element has definite mass. The order of magnitude of mass of one atom is 10^-27kg. 
• Isotopes are the atoms of the same element having same atomic number but different mass number. 

i. One dozen means 12 items. 

ii. One gross means 144 items.

Formula mass of CaSO₄

= Average atomic mass of Ca + Average atomic mass of S + Average atomic mass of four O

= (40.1) + 32.1 + (4 × 16.0) 

= 136.2 u

∴ Formula mass of CaSO₄ = 136.2 u

(a). 0.4 mole of nitrogen (N)

Number of atoms of N = Number of moles × Avogadro’s constant

= 0.4 mol × 6.022 × 10²³ atoms/mol

= 2.4088 × 10²³ atoms of N

(b). 1.6 g of Sulphur (S) 

Molar mass of sulphur = 32 g mol^-1

Number of moles = \(\frac{Mass\,of\,a\,substance}{Molar\,mass\,of\,a\,substance}\)

= \(\frac{1.6\,g}{32\,g\,mol^{-1}}\)

= 0.05 mol

Number of atoms of S = Number of moles × Avogadro’s constant

= 0.05 mol × 6.022 × 10²³ atoms/mol 

= 0.3011 × 10²³ atoms

= 3.011 × 10²² atoms of S

∴ (a) Number of nitrogen atoms in 0.4 mole = 2.4088 × 10²³ atoms of N

(b) Number of sulphur atoms in 1.6 g = 3.011 × 10²² atoms of S

Molecular formula of acetaldehyde : C₂H₄O 

Moles of acetaldehyde = 2 mol

a. Number of moles of carbon atoms = Moles of acetaldehyde × Number of carbon atoms 

= 2 × 2 

= 4 moles of carbon atoms

b. Number of moles of hydrogen atoms = Moles of acetaldehyde × Number of hydrogen atoms

= 2 × 4 

= 8 moles of hydrogen atoms

c. Number of moles of oxygen atoms = Moles of acetaldehyde × Number of oxygen atoms 

= 2 × 1 

= 2 moles of oxygen atoms

d. Number of molecules of acetaldehyde = Moles of acetaldehyde × Avogadro number = 2 mol × 6.022 × 10²³ molecules/mol = 12.044 × 10²³ molecules of acetaldehyde

∴ i. Number of moles of carbon, hydrogen and oxygen are 4, 8, 2 respectively.

ii. Number of molecules of acetaldehyde = 12.044 × 10²³

Correct answer is 0.22 N

Correct option is c. 20 mL

Correct option is a. 6.022 x 10²⁰

(a) When the object is placed anywhere between optical centre and infinity, the image is formed between optical centre and focus. It is diminished, virtual and erect.

(b) When the object is placed at infinity, the image is formed at focus. It is highly diminished, virtual and erect.

Correct answer = (c) 0

∵ 2^x+y = 2^x−y = √8 

∴ x + y = x – y 

⇒ y = 0

Correct answer = (a) x = 1, y = 2

The given system of equations is 

29x + 37y = 103 ……..(i) 

37x + 29y = 95 ……..(ii) 

Adding (i) and (ii), we get 

66x + 66y = 198 

⇒ x + y = 3 ………(iii) 

Subtracting (i) from (ii), we get 

8x – 8y = –8 

⇒ x – y = –1 

Adding (iii) and (iv), we get 

2x = 2 ⇒ x = 1 

Substituting x = 1 in (iii), we have 

1 + y = 3 ⇒ y = 2 

Thus, x = 1 and y = 2.

The codon which do not code for any amino acid and leads to termination of translation process is called nonsense codon.

VNTR stands for Variable Number Tandem Repeat.

VNTR is a small fragment of DNA containing tandemly repeated sequence, whose number and length vary among chromosome and individuals. VNTR shows a high level of polymorphism and is specific for different individual, whereas Probe is a small fragment of DNA or RNA used for identification of genes in biological system. These fragments are prepared for commercial and hybridization technology either for finding complementary sequence or in the diagnosis of some diseases. 

Full form of VNTR is Variable Number of Tandem Repeats

The correct answer is (D) hydration

Amino acids are activated in the presence of ATP and linked to (cognate) t-RNA.

Carries amino acid to the site synthesis / reaches amino acids to the respective codon.

Detailed answer:

Aminoacylation is the process of adding an activated amino acid to the acceptor arm of a transfer RNA. It is an essential step for the synthesis of protein, as it activated the amino acids (amino acid + ATP) and helps in linking them to their cognate tRNA in the presence of an enzyme aminoacyl tRNA synthetase.

a → Fishes; b → Amphibians.

According to the hypothesis proposed by Paul Ehrlich, the “Rivet popper hypothesis”, each species is essential in the balance of nature. If one is lost that much imbalance is caused in the ecosystem.

Inbreeding increases homozygosity and exposes harmful recessive genes.

(a) Protandry: The stamens mature earlier than stigma. 

E.g: Helianthus 

(b) Protogyny: The stigma mature earlier than stamens. 

E.g: Aristolochia bracteata

The inability of homologous chromosomes to separate out during meiosis in an individual is called non-disjunction. As a result of this, some gametes get both chromosomes, while others receive neither.

In Abutilon, the self-pollination is avoided by self sterility or self-incompatibility, in which if the pollen grain reaches the stigma of the same flower, it will be prevented from germination. It is a genetic mechanism.

Heterostyly: Some plants produce two or three different forms of flowers that are different in their length of stamens and style. Pollination will take place only between organs of the same length. 

E.g: Primula.

(b) they allow exsitu conservation of germplasm

(c) gamma diversity

(a) Area a = 0.1 

(b) 

(i) Habitat loss and fragmentation

(ii) Over-exploitation

(iii) Alien species invasions

(iv) Co-extinctions

1. The distribution of diversity of plants and animals decreases as we move away from equator towards the poles.

2. biological diversity

• Tropical latitudes have remained relatively undisturbed for millions of years, thus had a long evolutionary time for species diversification. 
• Tropical environments are less seasonal, relatively more constant and predictable.
• More solar energy is available which contributes to high productivity and greater diversity.

3. Amazonian rain forest in South America.

(c) Eastern Himalaya and Western Ghats

(b) species richness

(a) Amazonian forest

They make a statistical comparison of the species richness of exhaustively studied groups of insects of the temperate and tropical regions and extrapolate this ratio to other groups of animals and plants to calculate gross estimate of the total number of species present on the earth.

Method by Gopalan

Biodiversity depends on variety of species. Extinction of species is due to

1. Over exploitation 

2. Habitat loss and fragmentation 

3. Co-extinction

Compared to plants, animals have increased size and genetic variation. Also, the animals possess complex nervous system to control and coordinate various body activities.

Animals possess receptor organs for receiving various environmental stimuli and able to respond against them. The ability of locomotion is also a factor for greater diversification of animals.

Method by Gopalan

Biodiversity depends on variety of species.  Extinction of species is due to 

1. Over exploitation 

2. Habitat loss and fragmentation 

3. Co-extinction

The species diversity of plants on earth will be 22%

(a) Western Ghats

1. Hot spots: are the regions with high levels of species richness and high degree of endemism.

2. Endemism: is the number of species conned to a particular region and not found anywhere else. High degree of endemism means species richness is more and are not found anywhere else and should be protected to prevent extinction.

A hot spot is an area having endangered endemic species with very high levels of species richness. 

Criteria used for determining a hot spot:

i. Number of endemic species, i.e., species which are not found anywhere else. 

ii. Degree of threat which is measured in terms of habitat loss.

Western Ghats and Eastern Himalayas are two hot spots in India.

1.

• True
• False 

2. Alien species are foreign species, when introduced, some of them turn invasive and cause decline or extinction of indigenous species.

1. The evil quartet which cause extinction

• Habitat loss
• Overexploitation
• Alein species invasion
• Coextinction

2. Two ex situ method to conserve diversity

• Zoo
• Botanical garden

It would affect the ecosystem because insect pollinators form a part of food web. It may lead to co-extinction of species in the case of a co-evolved plant. It is a case of mutualism where extinction of one invariably leads to the extinction of the other.

The strategy is called Ex-situ conservation. In this technique, seeds are preserved in viable and fertile condition for long periods using cryopresrvation techniques.

Edward Wilson

These are examples of Alien species invasions. They threaten the indigenous species and lead to their extinction.

The collection of seeds of many different genetic strains of commercially important plants, that are kept viable for longer periods in place are called seed banks.

Habitat loss and fragmentation

• Destruction of habitat is the primary cause of extinction of species. 

• The tropical rainforests initially covered 14 per cent of the land surface of earth, but now cover only 6 per cent of land area.

Over-exploitation

• When biological system is over-exploited by man for the natural resources, it results in degradation and extinction of the resources. 

• For example, Stellar’s sea cow, passenger pigeon and many marine fishes.

a. The Amazon rainforest (called the “lungs of the planet”) is being cut and cleared for cultivation of soya beans and for conversion into grasslands for raising beef cattle. 

b. When large-sized habitats are broken or fragmented due to human settlements, building of roads, digging of canals, etc., the population of animals requiring large territories and some animals with migratory habitats declines.

i. Alien (exotic) species invasions 

• Some alien (exotic) species when introduced unintentionally or deliberately, become invasive and cause harmful impact, resulting in extinction of the indigenous species. 

• Nile perch, a large predator fish when introduced in Lake Victoria (East Africa) caused the extinction of an ecologically unique species of Cichlid fish in the lake.

ii. Co-extinctions 

• When a species becomes extinct, the plant and animal species associated with it in an obligatory manner, also become extinct. 

• For example, if the host fish species becomes extinct, all those parasites exclusively dependent on it, will also become extinct; in plant–pollinator mutualism also, extinction of one results in the extinction of the other.

Gel electrophoresis.