Ecology & Ecosystems — Set 3
Environment · पारिस्थितिकी और पारिस्थितिकी तंत्र · Questions 21–30 of 60
Organisms that feed on dead organic matter and contribute to the first stage of decomposition are?
Correct Answer: D. Detritivores
Detritivores like earthworms and woodlice consume decomposing plant and animal parts as well as feces. They physically break down the matter, increasing the surface area for microbial decomposers. This is an essential step in the global recycling of nutrients.
The total dry weight of all living organisms in a particular trophic level is called?
Correct Answer: C. Biomass
Biomass represents the total mass of biological material at a specific time and area. It can be measured in terms of fresh weight or dry weight. Pyramids of biomass provide a better representation of energy stored at each level than pyramids of numbers.
Which atmospheric gas is 'fixed' by specialized bacteria into a form that plants can absorb?
Correct Answer: C. Nitrogen
Nitrogen fixation converts atmospheric nitrogen ($N_2$) into ammonia or nitrates. This process is carried out by bacteria like Rhizobium living in root nodules or free-living Azotobacter. Nitrogen is a vital component of proteins and nucleic acids in all living things.
The maximum population size of a species that an environment can sustain indefinitely is called?
Correct Answer: D. Carrying Capacity
Carrying capacity is determined by available resources such as food, water, and space. When a population exceeds this capacity, resource depletion leads to a decline in population. It is a fundamental concept in population ecology and wildlife management.
In a marine ecosystem, an inverted pyramid of biomass is often observed because?
Correct Answer: D. Producers have a very high turnover rate
Phytoplankton are the tiny producers in oceans that reproduce and are consumed very rapidly. Although their standing biomass is small at any moment, they produce enough energy to support a larger mass of fish. This results in a pyramid where the consumer level appears larger than the producer level.
Which term describes the relationship where one species benefits and the other is neither harmed nor helped?
Correct Answer: C. Commensalism
Commensalism involves one organism using another for transport or housing without causing impact. An example is cattle egrets feeding on insects stirred up by grazing livestock. It is a common neutral-positive interaction in many terrestrial ecosystems.
The 'Gaia Hypothesis', proposing that Earth acts as a self-regulating complex system, was formulated by?
Correct Answer: A. James Lovelock
James Lovelock proposed the Gaia hypothesis in the late 1960s. It suggests that living organisms and their inorganic surroundings evolve as a single system to maintain conditions for life. The theory has significantly influenced modern systems thinking in environmental science.
What is the role of 'Nitrosomonas' bacteria in the nitrogen cycle?
Correct Answer: D. Converting ammonia to nitrite
Nitrosomonas is a genus of chemoautotrophic bacteria essential for the process of nitrification. They oxidize ammonia into nitrites as part of their energy metabolism. Another group, Nitrobacter, then converts nitrites into nitrates which are easily absorbed by plants.
Which of the following is considered the 'building block' of an ecosystem?
Correct Answer: A. Species
A species is a group of similar organisms capable of interbreeding to produce fertile offspring. Multiple populations of different species interacting in an area form a community. An ecosystem includes these biotic communities along with their abiotic environment.
Large regional units characterized by major vegetation types and associated fauna are called?
Correct Answer: D. Biomes
Biomes are defined by their climate, particularly temperature and rainfall patterns. Examples include deserts, grasslands, and temperate forests. They represent the largest geographical classification of the biosphere based on biological communities.