CBSE Questions for Class 12 Medical Biology Ecosystem Quiz 1 - MCQExams.com

• The rate of accumulation of biomass at the primary consumer level is termed productivity. 
• The rate at which these consumers convert the chemical energy of their food into their own biomass is called secondary productivity. Secondary productivity is the rate at which animals produce their organic matter by feeding on other organisms. 
• The efficiency at which energy is transferred from one trophic level to another is called ecological efficiency. On average it is estimated that there is only a 10 percent transfer of energy.

• Sedimentary cycles involve the cyclic exchange of minerals from the earth's crust or the lithosphere  with the biotic components of the ecosystem
• examples of cycles under the sedimentary category are sulfur and phosphorus cycles. 
• Gaseous cycles involve the cyclic exchange  of minerals between atmosphere and the biotic world.
• Common examples of gaseous cycles are carbon and nitrogen cycles.

• Time gradual and fairly predictable change in the species composition of a given area is called ecological succession.
• Ecological succession leads to a stable unchanging final state called climax community which is in equilibrium with the environment.
• During succession, some species colonize an area and their populations become more numerous, whereas populations of other species decline and even disappear.

Hence, during ecological succession, the gradual and predictable change in species composition occurs in a given area.

• Keystone species is an adhesive that reserves a habitat together and a large part of them is responsible for the support given to other species.

• Pioneer community is the first biotic community on a bare area. 
• Plants that are first to invade the bare area are called pioneer species.
• Usually, Lichens are the pioneers in lithosere and phytoplanktons are the pioneers in hydrosere.
• Seral community refers to an intermediate stage during ecological succession which leads to a climax community.
• Biotic community means the interaction of different species in an area. 

$$\textbf{Correct option: }$$ C

$$\textbf{Solution: }$$ 

$$\textbf{Option (C) }$$

$$\bullet$$The deep ocean is the largest reservoir of the Earth's carbon.

$$\bullet$$Carbon flows between each reservoir through the carbon cycle, which has slow and fast components.

$$\bullet$$The second most largest reservoir of carbon is geological reserves of fossil fuels which is followed by the terrestrial surface such as soil being the third reservoir. 

• Ecological succession is the process of change in the species structure of an ecological community over time. The time scale can be decades or even millions of years after a mass extinction.
• Evolution is the process of heritable change in populations of organisms over multiple generations.
  
• Selection is the preferential survival and reproduction or preferential elimination of individuals with certain genotypes (genetic compositions), by means of natural or artificial controlling factors.
• The specialization is the adaptation of an organism or organ to a special function or environment.

• A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem function. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Some keystone species, such as the wolf, are also apex predators.
•  EDGE species refers to animals that are Evolutionarily Distinct and Globally Endangered (hence EDGE). These species are considered to be one of a kind and, as its acronym suggests, are nearing extinction.
• Pioneer species are hardy species which are the first to colonize previously disrupted or damaged ecosystems, beginning a chain of ecological succession that ultimately leads to a more biodiverse steady-state ecosystem.
• Umbrella species are species selected for making conservation-related decisions, typically because protecting these species indirectly protects the many other species that make up the ecological community of its habitat.

•  It culminates in a stabilized ecosystem. By stabilized, it means the ecosystem has a single dominant species, maximum possible species diversity, high biomass, and low annual yield. (Fun fact: The low annual yield is because the community is in equilibrium with itself and with the environment. Therefore, the energy produced by the ecosystem is consumed within itself. Little is left as surplus).