Ecology and Biodiversity

Like all green plants, algae produce oxygen during the daylight hours as a by-product of photosynthesis. This is usually a major source of oxygen in fish ponds. In darkness, however, all plants consume oxygen, including algae. Algae blooms in natural water bodies or fish ponds normally produce much more oxygen in the daylight than they consume during the night, but some situations reduce the amount of oxygen a bloom produces without reducing its nighttime oxygen consumption. Trace minerals or nutrients needed by the algae are occasionally used up, causing some or even all, of the bloom to die back temporarily. The resulting bacterial decomposition and loss of normal oxygen production can lead to oxygen depletions and fish kills. Pond water generally changes from a deep green to black, gray, brown or clear after a phytoplankton die-off. 

Stimuli can be of any type whether physical or mechanical, biological as in response to another organic thing or chemical including chemical compounds or environment.

Living organisms must maintain a constant internal environment while living in a constantly changing external environment. Maintaining the internal environment is important because the processes that keep the cell alive can only take place under certain conditions. There are different processes that occur in the body to maintain the constant internal environment such as diffusion, osmosis, homeostasis, active transport, passive transport, endocytosis, exocytosis, etc. Homeostasis helps to maintain an equilibrium of an internal environment. 

Based on the object possessing life or not, the objects are classified as biotic and abiotic.

Abiotic: these are the objects that do not possess life. Among the given options only plants are included under biotic category and rest which includes air, water and soil belong to abiotic objects.

Based on the object possessing life or not, the objects are classified as biotic and abiotic.

Biotic: These are living organisms that possess life and carry on metabolism accordingly. Biotic environment includes:

• Producers prepare food by themselves like plants.
  
• Consumers feed on plants and other organisms like herbivores, carnivores etc.
  
• Decomposers convert dead and decayed matter into simpler organic matter. Examples are microorganisms.
  

The biosphere includes all living organisms (plants, animals, humans) and the environments they inhabit. Mountains are geological features and are part of the lithosphere, not the biosphere.

The biosphere is the global sum of all ecosystems, representing the zone of life on Earth. It exists due to the complex interaction between the lithosphere (land), atmosphere (air), and hydrosphere (water).

Ecosystem dynamics are primarily driven by the continuous flow of energy through trophic levels and the cycling of essential chemical nutrients through the biotic and abiotic components.

The flow of energy in the ecosystem is unidirectional. The energy enters the plants (from the sun) through photosynthesis during the making of food. This energy is then passed on to the successive trophic levels in a food chain is only 10% and rest energy get lost as heat during transfer and life process. 

Flow of energy in different trophic levels of an ecosystem is called as bioenergetics. It is also called as energy flow. In this, there is flow of energy through the food chain. Solar energy is converted to chemical energy by photosynthetic plants. From plants, the energy is transferred to primary consumers and secondary consumers in a food chain. Decomposers release energy back to the environment by decomposing organic waste matter.

An ecosystem is normally an open system because there are a continuous and variable entry and loss of energy and material. The ecosystem is the basic fundamental unit of ecology which includes both the organism and the non-living environment is influencing the property of each other and is necessary for the maintenance of life. The whole Earth can be known as biosphere or ecosphere.

• The pyramid of energy shows the relationship between the flow of energy and different trophic level.
• The pyramid of energy depicts the flow of energy in the ecosystem.
• The source of energy in an ecosystem is the sun, the producers trap the solar energy and use it for photosynthesis which is in turn eaten by organisms of the higher trophic level such as primary consumers, secondary consumers.
• So, the correct answer is 'The rate of flow of energy through the food chain'.

An ecosystem comprises of biotic and abiotic components which interact with each other to maintain an equilibrium. A major focus of ecosystem ecology is on functional processes, ecological mechanisms, that maintain the structure and services produced by ecosystems. These include primary productivity (production of biomass), decomposition, and trophic interactions. The various trophic levels of an ecosystem interact with each other by  a flow of energy and cycling of materials from one trophic level to the other.

Bioenergetics is a field in biochemistry, that concerns energy flow through living systems. This includes the study of different cellular processes, such as cellular respiration and the many other metabolic processes, that can lead to production and utilization of energy in forms such as ATP molecules.