Solutions-Class-12-Biology-Chapter-14-Ecosystems and Energy Flow-Maharashtra Board

(a) Producers

(b) Zooplankton

(c) Carnivores

(b) 50 %

(c) Climax community

(a) Primary

(c) Phosphorus

Number of insects dependent on a single tree, is an example of ecosystem having inverted pyramid of numbers.

Oceanic ecosystem has inverted pyramid of biomass.

Phosphorus acts as limiting factor for productivity in an aquatic ecosystem.

Atmosphere is the reservoir of carbon cycle, while fossil fuels embedded in ocean and oceanic waters are the sink of carbon in carbon cycle.

Ecological Pyramids : Ecological Pyramids are the representation of relationships between different components of ecosystem at successive trophic levels.

Pyramid of numbers :

• The pyramid of numbers demonstrates the connection between producers, herbivores, and predators at each trophic level based on their numbers.
• As we move up the trophic levels, the number of dependent creatures decreases.
• For example, there are more grasses than animals who consume them. The amount of herbivores, such as rabbits, would be lower than grass but higher than predators, which rely on rabbit populations.
• Thus, the producers would be more than primary consumers and primary consumers would be more than secondary consumers.
• The top level consumers would be least in their numbers. This pyramid shows upright nature.

Pyramid of biomass :

• Pyramid of biomass are constructed by taking into consideration the different biomass in every successive trophic level.
• Pyramid of biomass in seas in inverted as the biomass of fishes is more than the biomass of phytoplankton.

Primary Productivity: Primary productivity refers to the rate of biomass generation in an ecosystem, measured in grams per square metre per day (g/m2/day), expressed in units of mass per unit surface per unit time.

• Primary productivity is described as gross primary productivity (GPP) and net primary productivity (NPP).
• The rate of production of organic matter during photosynthesis is called gross primary productivity of an ecosystem. Of this the amount of energy lost through respiration of plants is called respiratory losses.
• It is calculated by subtracting the energy lost through respiration, resulting in net primary productivity (NPP), which is the available biomass for heterotrophs (herbivores, carnivores, and decomposers).

Factors affecting primary productivity:

Gross primary productivity (GPP) depends on the following factors :

• Plant species inhabiting a particular area.
• Variety of environmental factors such as temperature, sunlight, salinity,
• oxygen and carbon dioxide content, etc.
• Availability of nutrients.
• Photosynthetic capacity of plants.

• Decomposition is a process carried out by decomposer organisms, including bacteria, actinomycetes, and fungi.
• Detritus food chain initiates decomposition, starting from dead organic matter.
• Detritivores break down detritus into smaller fragments, referred to as fragmentation.
• Water-soluble inorganic nutrients seep into the soil, precipitated as salts, known as leaching.
• Catabolism, a third step, involves enzymes degrading detritus into simple inorganic substances.
• Humus, a dark-colored amorphous substance, is formed from partially decomposed organic matter.
• Decomposition requires more oxygen and is influenced by temperature and humidity.

• Reservoir of sedimentary cycles is earth’s crust.
• The nutrients such as phosphorus which show sedimentary cycle, moves through hydrosphere, lithosphere and biosphere.
• There is no respiratory release of nutrients into the atmosphere which show sedimentary cycle.
• Natural reservoir of such nutrients are usually in the form of rocks. The rocks upon weathering release such nutrients into circulation.
• Sedimentary cycles are very slow in their reactions.

Carbon cycle :

• The carbon cycle involves several processes, including photosynthesis, respiration, decomposition, sedimentation, and combustion.
• Carbon, which makes up 49% of the dry weight of all organisms, is present in the oceans and fossil fuels, which serve as long-term storage places.
• Carbon dioxide is stored in the carbon-carbon bonds of carbohydrates during photosynthesis, while respiration releases the same energy. Carbon dioxide is primarily found in oceans and rocks, where it forms mild carbonic acid upon dissolution. Corals and algae help build coral reefs made of limestone.
• Carbon moves through food chains, with autotrophic green plants on land and in water taking up carbon dioxide and manufacturing carbohydrates through photosynthesis.
• Carbon stored in plants can be released into the atmosphere, consumed by animals upon feeding, or stored until the plant dies. Animals obtain their carbon through their food, and carbon in animals can be released back into the atmosphere through respiration, decomposition, or conversion into fossil fuels.
• Fossil fuels like coal, oil, and natural gas can be mined and burned for energy purposes, releasing carbon dioxide back into the atmosphere. Carbon from limestone can also be released if pushed to surfaces and slowly weathered away, and subducting and volcanic eruptions can release stored carbon from sediments.