Arrange the steps of xerarch succession in a proper sequence.
A. Appearance of bryophytes
B. Forest community
C. Invasion of lichen on a bare area
D. Appearance of shrubs
Choose the correct answer from the options given below:

Which of the following pairs is not an example of homology?

Select the factor which does not affect Hardy-Weinberg Equilibrium?

Which of the following free living soil microorganisms are used as biofertilisers?
(A) Anabaena
(B) Azospirillum
(C) Rhizobium
(D) Azotobacter
Choose the correct answer from the options given below:

Arrange the following features related to decomposition cycle in a terrestrial ecosystem in correct sequence?
(A) Fallen leaves eaten by insects and animals
(B) Trees grow in the soil
(C) Some nutrients leach into the soil
(D) Decomposition by earthworm and bacteria etc.
Choose the correct answer from the options given below:

Match List-l with List-II

List-l (Term)	List-II (Characteristics)
(A) Bt toxin	(I) ADA deficiency
(B) RNAi	(II) Increased food supply
(C) Green revolution	(III) crylAc gene
(D) Gene Therapy	(IV) mRNA silencing

Choose the correct answer from the options given below:

Read the following passage carefully and answer the given questions.
Biofertilisers
Biofertilisers are organisms that enrich the nutrient quality of the soil and their main sources are bacteria, fungi and cyanobacteria. You have studied about the nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria can fix atmospheric nitrogen into organic forms. Other bacteria can also fix atmospheric nitrogen while free-living in the soil (examples Azospirillum and Azotobacter). Fungi are also known to form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development. Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter in to the soil and increase its fertility. Currently, in our country, a number of biofertilisers are available commercially in the market and farmers use these regularly in their fields to replenish soil nutrients and to reduce dependence on chemical fertilisers.
Choose the free living, nitrogen-fixing bacteria from the following.

Arrange the evolutionary human species in their occurrence from recent to the oldest order.
(A) Australopithecus
(B) Homo erectus
(C) Homo sapiens
(D) Neanderthal man
Choose the correct answer from the options given below:

Arrange the steps for transformation of recombinant DNA in sequence -
(A). For heat shock, bacterial cells are placed at 42°C; and then they are placed on ice.
(B). The bacterial cells must be made 'competent' to take up DNA by treating them with a specific concentration of divalent cation such as calcium.
(C). The bacteria are now able to take up the recombinant DNA.
(D). Recombinant DNA can then be forced into those cells by incubating the cells with recombinant DNA on ice.
Choose the correct answer from the options given below:(C)
(C), (B), (D), (A)

Match List - I with List - II

List - I	List - II
(A) Impurity defect	(I) NaCl with anionic sites called F centres
(B) Metal excess defect	(II) FeO with Fe3+
(C) Metal deficiency defect	(III) Non ionic solids and density of solid decreases
(D) Simple vacancy defect	(IV) NaCl with Sr2+ and cationic sites vacant

Choose the correct answer from the options given below:

A battery of emf 3 V and internal resistance \( r \) is connected in series with a resistance of \( R = 55 \text{ } \Omega \) through an ammeter of resistance \( R_A = 1 \text{ } \Omega \). The ammeter reads a current \( I = 50 \text{ mA} \). Find the internal resistance \( r \) of the battery.

A resistor connected to a battery is heated due to the current. The quantity which does not change is

Which one of the following has the lowest melting point ?