Ecosystems and Food Chains

• The environment includes physical surroundings like air, water bodies, soil, plants, animals, humans, and microorganisms (bacteria and fungi, called decomposers).
• Waste materials from human and animal activities can be categorized into biodegradable and non-biodegradable wastes.

Biodegradable Wastes

• Biodegradable wastes break down naturally over time through the action of microorganisms, such as fungi and bacteria.
• Temperature and sunlight aid in the decomposition of these wastes.
• Examples include food waste, tea leaves, urine, fecal matter, sewage, agricultural residue, paper, wood, cloth and cow dung.

Non-Biodegradable Wastes

• Non-biodegradable wastes do not break down via natural biological processes.
• These wastes can be solid, liquid, or gas.
• They persist in the environment and can harm ecosystems.
• Examples include DDT, insecticides, pesticides, mercury, lead, arsenic, aluminum, plastics, polythene bags, glass, and radioactive wastes, major pollutants.

Ecosystems

• An ecosystem is a self-contained community of living organisms (plants, animals, and decomposers) interacting with their non-living environment (soil, air, and water).
• Ecosystems require sunlight for energy and involve continuous exchange of energy and matter.
• Ecosystems can be natural (grassland, forest, sea, river, desert, mountain, pond, lake) or man-made (garden, crop fields, park, aquarium).
• Man-made ecosystems include cropland or aquariums, aquatic ecosystems are marine or freshwater, and natural ecosystems are terrestrial.

Components of Ecosystems

• Ecosystems have two components: biotic and abiotic.

Biotic Components

• Includes three types of organisms: producers, consumers, and decomposers.

Producers

• Green plants and blue-green algae produce food via photosynthesis, are autotrophs.
• Microscopic organisms floating on the water surface are plankton (phytoplankton and zooplankton).
• Phytoplankton are microscopic aquatic plants whereas zooplankton are microscopic aquatic animals, like protozoa.

Consumers (Heterotrophs)

• Organisms consume other organisms or their products for food, relying on producers directly or indirectly, categorized as herbivores, carnivores, or omnivores.
• Herbivores eat producers (plants), called primary consumers (deer, rabbit, rat, squirrel, goat, cattle).
• Carnivores eat other animals; small carnivores that eat herbivores are called secondary consumers (snake, wild cat, jackal, frog, some birds, fishes).
• Large carnivores that eat small carnivores are tertiary consumers (birds of prey like hawk and eagle, tiger, lion).
• Omnivores eat both plants and animals (humans, dogs, crows, sparrows, bears, mynahs, ants).

Decomposers

• Fungi and bacteria break down complex organic compounds in dead organisms into simpler substances, recycling nutrients back to the soil, micro-consumers or saprotrophs.

Abiotic Components

• Non-living components of an ecosystem including physical environment.
• Edaphic factors include soil texture, topography, water, and air.
• Inorganic substances include carbon dioxide, nitrogen, oxygen, water, phosphorus, sodium, potassium, and calcium.
• Organic compounds include proteins, carbohydrates, and lipids.
• Climatic factors include sunlight, temperature, pressure, humidity, moisture, and rainfall, and affect organism distribution.

Functions of an Ecosystem

• Indicates available solar energy and ecosystem efficiency in trapping energy.
• Provides information on available essential minerals and recycling periods.
• Gives knowledge on interactions among populations and between populations and the abiotic environment.
• Helps in resource conservation, pollution protection, and maximizing productivity.
• Involves two processes: energy flow and biogeochemical cycles (nutrient movement); energy flow is unidirectional, while nutrient movement is cyclic.

Food Chain

• A food chain is a sequence of living organisms in a community, where each consumes the prior transferring food energy.
• A grassland food chain consists of grass (producer) to insect (herbivore) to frog (carnivore) to eagle (secondary carnivore).

Significance of Food Chains

• Helps understand food relationships and interactions in an ecosystem.
• Transfers energy and materials between living ecosystem components.
• Provides ecosystem dynamicity.
• Allows movement of toxic substances like pesticides and weedicides.

Food Web

• Interconnected food chains form a food web, creating relationships between various species.
• Organisms occupy multiple positions in the food web, obtaining food from different sources and being consumed by different organisms.

Trophic Levels

• Trophic levels are steps in a food chain where food or energy transfer occurs.
• Gradual decrease in energy transfer from one trophic level to the next in a food chain.
• 10% of energy is transferred to the next trophic level, while 90% is used by the present trophic level.
• Plants/producers form the first trophic level, herbivores/primary consumers the second, carnivores/secondary consumers the third, and large carnivores/tertiary consumers the fourth.

Flow of Energy

• Green plants capture about 1% of solar energy through photosynthesis.
• Plants use some energy for metabolic activities, releasing some as heat, and store the rest as chemical energy (carbohydrates).
• Herbivores eat plants, transferring the chemical energy.
• Herbivores use some energy, release some as heat, and store the rest.

Ten Percent Law

• Only 10% of energy is available for transfer to the next higher trophic level.
• Example: Solar energy (1000 Joule) -> Plant (100 J) -> Deer (1 Joule) -> Lion (0.1 Joule).

Environmental Problems

• Environmental changes and human activities lead to slow environmental degradation causing problems like depletion of the ozone layer and waste disposal.

Depletion of Ozone Layer

• The ozone (O3) layer, in the stratosphere (12-50 km above sea level known as the ozonosphere), protects from harmful UV radiation.
• A decline in ozone layer thickness in Antarctica was discovered in 1985, termed the ozone hole.
• Excessive use of CFCs (Chloro Flouro Carbons), like Freon, in refrigerants and fire extinguishers causes ozone depletion.
• A single chlorine atom can destroy 100,000 ozone molecules; halons, carbon tetrachloride, methyl chloroform, and nitrous oxide also deplete ozone.
• Chlorine from CFC decay converts to a reactive gas by clouds in the cold stratosphere, leading to ozone depletion in spring.
• With warmer spring temperatures, clouds evaporate, reactive chlorine ceases, and destruction of ozone stops, being replenished by ozone from middle and lower latitudes.
• Chemical equation for ozone hole due to CFCs: CFCI3+ UV Light ==> CFCI2+ CI, CI + O3 ==> CIO + O2 and CIO + O ==> CI + O2

Effects of Ozone Layer Depletion

• Increases risks of eye diseases, skin cancer, and infectious diseases in humans and animals.
• Can alter species composition and biodiversity in forests and grasslands.
• May affect phytoplankton distribution, impacting aquatic food webs, and damage early development stages of aquatic animals, decreasing reproductive capacity and larval development.
• Has effect on Bio-geo-chemical Cycles and air quality.
• UNEP forged an agreement to freeze CFC production, promotes ozone-friendly substitutes like HCFC, recycling CFCs/halons, and afforestation.

Eutrophication

• A water body becomes overly enriched with nutrients, causing simple plant life to proliferate, leading to excessive algae/plankton growth (algal bloom).
• Results in water quality deterioration and depletion of dissolved oxygen; eutrophic waters potentially becoming "dead zones."
• Contributors are agriculture/industrial wastes rich with excess fertilizers/phosphorus leading to algal blooms.
• Bacteria decomposes dead algae, consuming oxygen and hypoxia leading to suffocation in water bodies.

Biological Magnification

• The concentration of harmful chemicals increases at each trophic level in a food chain
• Example: Grass (10 ppm DDT) -> Deer (200 ppm DDT) -> Lion (5000 ppm DDT).

Managing Garbage

• Industrialization and consumerism lead to increased waste accumulation and disposal issues.
• Waste disposal in a scientific way depends on waste type.
• Recycling solid waste to create new items: reduce, reuse and recycle.
• Burning waste at high temperature to form ash destroys household, chemical and biological wastes through incineration.
• Dumping and compacting wastes in low lying areas via landfills can be used to dispose of waste for a considerable time.
• Filling organic wastes into a compost pit, covers with soil for around three months, changes the garbage into organic manure for composting.
• Sewage treatment disposes sewage by treating the water at a sewage treatment plant and then releases into water bodies
• Organic matter is then 'digested' to produce 'sewage gas' (biogas) and 'manure'.