It is a type of aneuploidy where only one chromosome of a pair is present in the cells.

1. Gamete intrafallopian transfer (GIFT) can be carried out.
2. In this method, an ovum collected from a healthy donor is transferred into the fallopian tube of another woman, who cannot produce viable ova, but can provide suitable conditions for fertilisation and further development of the foetus.

The starter added in the milk is the small amount of curd. This contains a large number Lactobacilli (LAB) which convert milk into curd. They grow and multiply. During their growth they produce enzymes which convert milk sugar lactose into lactic acid which coagulate and partially digest milk protein casein to form the curd.

1. The introduction of Nile perch into Lake Victoria led to the extinction of more than 200 species of cichlid fish in that lake.
2. Introduction of African catfish Clarias qariepinus for aquaculture poses a threat to the indigenous catfishes in Indian rivers.
3. Carrot grass (Parthenium) and Lantana introduced into our country have become invasive and caused environmental damage; they pose a threat to the native species of plants in our forests.

A monohybrid cross is as follows:

\(F_{ 2 }\)

The phenotypic ratio of smooth-seeded to wrinkled-seeded plants, is 3 : 1.
From the Punnett square, it can be seen that one of the smooth-seeded plants is homozygous (55), while the other two are heterozygous (Ss): hence the genotypic ratio is 1 : 2 : 1.

(i) The two types of desirable approaches to conserve biodiversity are in-situ and ex-situ conservation.
(ii) Commensalism because Ophrys employs sexual deceit to get pollinated by species of bee as petal of its flower bears resemblance to female of the bee in size, colour and marking and so male bee is attracted to what it perceives as female; pseudocopulates with the flower and thus pollinates it. If the female bee's colour patterns change even slightly due to any reason during evolution, pollination success will be reduced unless the orchid flowers co-evolves to maintain the resemblance of its petal to the female bee.

1. MECHANICAL METHOD
a) intra uterine devices (IUD ) = they are inserted inside the uterus and supress sperm motility and inhibit fertilisation. example = cu- t
2. CHEMICAL CONTRACEPTION= they are the hormonal contraceptives and are available in the form of oral pills . example = sahelli.
3. BARRIER METHOD = condoms is the most widely used method by males which prevents deposition of semen into the vagina of the females . it also protects the males and females from sexually transmitted disease.
4. PERMANENT METHODS = they r irreversible methods.
a) VASECTOMY = it occurs in males in which the vasa deference is cutted and tied at the ends . it inhibits the transport of sperm due to which fertilisation cannot occur.
b) TUBECTOMY= it occurs in females during which the fallopian tube is cutted and tied at the ends due to which the ovum is not transported nd fertilisation does not occur.

(i) Biogas is a mixture of gases produced from degradable organic matter by activity of microorganisms.
(ii) It is used as a fuel for heating, cooking. lighting, power for irrigation, etc.
(iii) Microorganisms involved are methanogens such as methanobacterium.
(iv) Anukool is helpful, intelligent, has human values and care for people. 

(a)Genotype of an unknown pea plant with dominant phenotype may be tested with the help of a test cross A tall pea plant with TT YY or Tt Yy.

(b) a= The progeny resembled both parents, b=Dominance, c= The progency was in-between

This is may be due to any following reasons:
(i) Fast growing species may compete with less vigorous local species.
(ii) Alien species will proliferate in that area if their natural pests and predators are not present.
(iii) by amensalism i.e. it may vigorously and may form conditions unfavorable for growth of local native species like Eichhornia.

Symptoms of Haemophilia:
1.Since a protein necessary for blood clotting is not formed, the blood does not clot and there is non-stop bleeding in case of an injury in the afflicted individual. Symptoms of sickle-cell anaemia.
2. The RBCs become sickle-shaped.
3. The oxygen transport to the tissues is impaired.
Differences

(i) Cu-T, Cu-7 and Multiload-375.
(ii) IUDs function by either of the following mechanisms
(a) Suppress sperm motility or fertilising capacity of sperms.
(b) Increase phagocytosis of sperms within the uterus.
(c) They suppress sperm motility.

(a) 1. To continue to get the products of human consumption.
2. Plays a major role in many ecosystem services that nature provides and that is invaluable.
3. Moral duty to pass on biological legacy in good order to future generations.
(b) 1. Habitat loss and fragmentation: large habitats when broken lead to loss of habitat for animals needing large territories (are badly affected) - population decline.
2. Over exploitation: leading to extinction of many, especially commercially important species.
3. Alien species invasion: alien species when introduced may turn invasive causing decline and extinction of indigenous species II explain with an example.
4. Coextinction: when one species become extinct, any other organism intimately associated also becomes extinct.

(a) One gene I has three alleles I^A, I^B and i hence multiple allelism.
We inherit any two of them. When the genotype is I^AI^B,the individual has AB blood group since both I^A and I^B equally influence the formation of Antigen A and B- Co-dominance.
(b)(i) I^A i -A blood group
(ii)ii-0 blood group

A flow chart showing eutrophication
stinking eutrophic lake with colored and turbid water
             ↑
loss of species diversity
             ↑
Death of aquatic animals including fish 
              ↑
Reduced contents of dissolved oxygen
              ↑
Increase in organic loading of lake
              ↑
Death of submerged plants due to reduced light
              ↑
Biological enrichment of water
(algal bloom, planktonic algae, and higher plants)
             ↑
Nutrient enrichment of water

(i)(a) Short stature individuals with round head and
furrowed longue.
(b) Slow mental development.
(ii) Both
(ii) Klinefeller's syndrome
(iv) Male
(v) (a) Rudimentary ovaries
(b) Lack of sccondary sexual characters
(vi) Females.

Biogas plant is installed basically to get the biogas which is used as fuel for heating and cooking, lighting, etc.It also yields nitrogen rich slurry that is an excellent source of manure.

Test Cross. When an individual crossed to recessive parent is called test cross.

The results can be easily analysed. If you follow the monohybrid cross where the F1 is test crossed, a ratio of 1:1 will be obtained. On the same basis you can work out that in a dihybrid case, the test cross ratio will be 1:1:1:1. Test cross can also be used for another purpose. The homo and heterozygous genotypes for dominant trait cannot be differentiated because they show the same phenotype. If put them  through a test cross, it is observed that all homozygous dominant combinations will breed true but heterozygous gentypes will follow the segregation.

1.B) 1 : 1
2.C) 50 % hybrid tall and 50 % dwarf
3.B) Tt ×tt
4.B) F1 tall plant and F1 recessive parent
5.B) Genotype of a tall Pea plant

(i) (b) : Evil quartet, i.e., four major causes of biodiversity loss are habitat loss and fragmentation, over exploitation, alien species invasion and co-extinction.
(ii) (a)
(iii) (b) : Population traits which make species susceptible to extinction are: small population, higher status of trophic level and inability to switch over to alternate foods.
(iv) (a)
(v) (c)

(d) If A is false, but R is true

(d) If A is false, but R is true