Environment

• Natural component where biotic (living) and abiotic (non-living) factors interact.
• Shapes the habitat and ecosystem of organisms.
• Includes physical (nutrients, water, air), biological (organisms, biomolecules), and chemical interactions (carbon, nitrogen cycles).
• All organisms depend on the environment for food, energy, water, oxygen, and shelter.

Biosphere

• Biological component of Earth supporting life: lithosphere, hydrosphere, atmosphere.
• Includes all living organisms + dead organic matter produced by them.
• Absent at extreme poles, the highest mountains, deepest oceans.
• Spores may occur above 8,000 m but are dormant, not metabolically active.

Habitat

• Physical environment where an organism lives (address of an organism).
• Many habitats together form an environment.
• One habitat may support multiple species with similar requirements (e.g., an aquatic habitat).

Difference: Habitat vs Environment

• Habitat always has life; environment may or may not.
• All habitats ⟹ environments; all environments ⟹ not habitats.
• Habitat = preference of one species; environment = may suit many species.
• The environment influences habitat, not vice versa.

Ecosystem

• A functional unit of nature where producers, consumers, and decomposers interact with the physical environment.
• Specific and limited species (e.g., aquatic ecosystem).
• Linked by nutrient cycles and energy flow.
• If one part is damaged, the entire system is affected.

Classification

• Terrestrial: Forest, grassland, desert
• Aquatic: Pond, lake, wetland, river, estuary
• Man-made: Crop fields, aquarium

Difference: Ecology, Environment & Ecosystem

• Ecology: Study of interactions between organisms and the environment.
• Environment: A Group of ecosystems (can be a large/small region).
• Biosphere: A Region on Earth that supports life.
• Habitat: Place where a species lives.
• Ecosystem: Producers–consumers–decomposers and their relationships (functional unit).

Components of an Ecosystem

Two types: Abiotic & Biotic

Abiotic Components

Non-living inorganic parts act as limiting factors.

Limiting Factor

• A single major factor that restricts survival.
• Example:
  • Rainforest → soil heavily leached → poor soil = limiting factor → slow regeneration.
  • Dense canopy → less light → saplings die → light = limiting factor.

Major Abiotic Factors

Light

• High intensity → more root growth; small leaves.
• Low intensity → poor growth, flowering, fruiting.
• Below minimum → plant death due to CO₂ accumulation.
• Red & blue light are effective for photosynthesis.
• Blue light → small plants; red → elongated; UV → dwarf.

Frost

• Freezes soil moisture → plants die from transpiration stress.
• Freezing water increases salt concentration → cell dehydration.
• Causes canker.

Snow

• Acts as a thermal blanket.
• Can break branches.
• Shortens vegetative growth period.

Temperature

• High temp → protein coagulation → plant death.
• Disturbs the balance between respiration & photosynthesis.
• Causes tissue desiccation.
• Dieback: shoots die, roots survive (e.g., sal).

Additional Factors

• Atmosphere: O₂ = 21%, CO₂ = 0.038%
• Organic compounds: proteins, carbohydrates, lipids
• Inorganic compounds: carbon, water, nitrates, phosphates
• Altitude: vertical zonation due to temperature changes
• Buffering capacity: maintains neutral pH
• Salinity:
  • Euryhaline = wide tolerance
  • Stenohaline = narrow tolerance

Biotic Components

1. Producers (Autotrophs)

• Green plants, bacteria, and algae perform photosynthesis.
• Aquatic primary producers: phytoplankton.

2. Consumers (Heterotrophs)

Macro-consumers:

• Herbivores (primary): sheep, rabbit
• Secondary: wolves, dogs, snakes
• Tertiary: lions, snakes
• Omnivores: humans, bears, pigs

3. Decomposers (Saprotrophs / Osmotrophs)

• Bacteria & fungi feed on dead organic matter.
• Detritivores: earthworms, nematodes, arthropods (feed on detritus; aid decomposition).