Ecology And Environment

Step 1: Understanding the Concept:
According to the laws of thermodynamics, energy transfer is never 100% efficient; some energy is always lost as heat.

Step 2: Detailed Explanation:
Energy enters an ecosystem as sunlight and is converted into chemical energy by autotrophs (producers).
When herbivores consume producers, only a fraction (roughly 10%) of the energy is stored in their biomass; the rest is lost via respiration and metabolic heat.
Because the energy lost as heat cannot be recaptured by plants for photosynthesis, the flow of energy must be strictly one-way (unidirectional) from producers to consumers to decomposers.

Step 3: Final Answer:
Energy flow is unidirectional because energy lost as heat at each trophic level is irretrievably lost to the environment and cannot be reused by the previous level.

Step 1: Understanding the Concept:
Certain toxic chemicals, like DDT or heavy metals, are non-biodegradable and tend to accumulate in living tissues.

Step 2: Detailed Explanation:
When these toxins enter an ecosystem, they are taken up by producers.
Because they are not easily metabolized or excreted, they remain in the organism's body.
As organisms are consumed by predators at higher trophic levels, the toxins are concentrated further.
This phenomenon, where the concentration of a toxin multiplies at each successive trophic level, reaching its maximum in apex predators, is known as biological magnification or biomagnification.

Step 3: Final Answer:
The phenomenon is called biomagnification.

Step 1: Understanding the Concept:
Environmental conservation and policy are often coordinated on a global scale by international organizations.

Step 2: Detailed Explanation:
UNEP stands for the United Nations Environment Programme.
It is responsible for coordinating the UN's environmental activities and assisting developing countries in implementing environmentally sound policies and practices.

Step 3: Final Answer:
United Nations Environment Programme.

Step 1: Understanding the Concept:
Energy from the sun is captured by plants and transferred through the ecosystem via consumption.

Step 2: Detailed Explanation:
A food chain is a linear, sequential pathway in an ecosystem depicting how energy and nutrients flow from one organism to another.
It typically starts with a producer (like a green plant) that makes its own food, followed by a primary consumer (herbivore), secondary consumer (carnivore), and so forth.

Step 3: Final Answer:
It is a linear network showing the flow of energy from producers to apex predators.

Step 1: Understanding the Concept:
The ozone layer in the stratosphere protects the Earth from harmful ultraviolet (UV) radiation from the sun.
Certain man-made chemicals can break down ozone molecules, leading to the thinning of this protective layer.

Step 2: Detailed Explanation:
Chlorofluorocarbons (CFCs) are highly stable compounds formerly used in refrigerants and aerosols.
When they reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms.
A single chlorine atom can destroy thousands of ozone (O ) molecules through a catalytic cycle.
While CO is a greenhouse gas, DDT is a pesticide, and SO causes acid rain, CFCs are the primary culprits for ozone depletion.

Step 3: Final Answer:
The correct option is (A).