Answer: (C)

Explanation: Ecotone is a zone of junction between two or more diverse ecosystems. For e.g. the mangrove forests represent an ecotone between marine and terrestrial ecosystem. Other examples are – grassland, estuary and river bank.
Characteristics of Ecotone:
1. It may be very narrow or quite wide.
2. It has the conditions intermediate to the adjacent ecosystems. Hence it is a zone of tension.
3. A well-developed ecotone contains some organisms which are entirely different from that of the adjoining communities.

4. Sometimes the number of species and the population density of some of the species is much greater in this zone than either community. This is called edge effect.
5. The organisms which occur primarily or most abundantly in this zone are known as edge species. In the terrestrial ecosystems edge effect is especially applicable to birds.
6. For example, the density of birds is greater in the mixed habitat of the ecotone between the forest and the desert.
Hence, all statements are correct.

Answer: (B)

Explanation: A sequence of organisms that feed on one another, form a food chain. In nature, two main types of food chains have been found: Grazing food chain and Detritus food chain. The grazing food chain starts with producers or autotrophs as base, which is consumed by heterotrophs. It is found in both Terrestrial and aquatic ecosystems. The Detritus food chain starts from dead organic ‘matter of decaying animals and plant bodies to the microorganisms and then to detritus feeding organism called detrivores or decomposer and to other predators. The two food chains are linked as the initial energy source for detritus food chain is the waste materials and dead organic matter from the grazing food chain. Hence, statement 3 is not correct.

Answer: (A)

Explanation: Biomass, a renewable organic resource, includes agriculture crop residues (such as corn stover or wheat straw), forest residues, special crops grown specifically for energy use (such as switchgrass or willow trees), organic municipal solid waste, and animal wastes. Biomass Gasification is a process that converts organic or fossil-based carbonaceous materials at high temperatures, without combustion, with a controlled amount of oxygen and/or steam into carbon monoxide, hydrogen, and carbon dioxide. The carbon monoxide then reacts with water to form carbon dioxide and more hydrogen. Hence, statement 3 is not correct.

Answer: (B)

Explanation: They have adapted to desert conditions by developing extremely long root systems to draw water from deep underground near the water table. The mesquite’s roots are considered the longest of any desert plant and have been recorded as long as 80 feet. Some have succulent leaves to store moisture. Some have thorny leaves to reduce water loss by transpiration. Waxy leaves protect soil moisture beneath the coating. Hence, statement 2 is correct.

Answer: (B)

Explanation: Light is a limiting factor for life in deep oceans. Not all the colour components of the visible spectrum are available for marine plants living at different depths of the ocean. Sunlight is broken into its seven component colours as it penetrates through the ocean water by dispersion. Longer wavelengths cannot penetrate deeper whereas shorter wavelengths do. Algae use photosynthesis to manufacture food. So, the ones utilizing the short wavelength for photosynthesis survive. Red algae have red pigment (phycoerythrin) which carries out photosynthesis using only short wavelength light found in greater depths. They can be found as deep as 200 m in ocean water. Hence, option (b) is correct.