Biology XI: Environmental Biology

❦

Ecosystems

Components: biotic (producers, consumers, decomposers) and abiotic factors.
Energy flow is one-way: about 10 percent of energy is transferred between trophic levels, so food chains are short. Show energy flow with pyramids of numbers, biomass, and energy. Primary productivity: gross and net.
Nutrient cycles: carbon, nitrogen (fixation, nitrification, assimilation, ammonification, denitrification), phosphorus, and water cycles. Human activities disturb them.
Succession: primary and secondary; the climax community.

Populations and Communities

Population growth: exponential, dN/dt = rN; logistic, dN/dt = rN(K − N)/K, where K is the carrying capacity. r-selected species (many small offspring) and K-selected species (few, large offspring).
Interactions: competition, predation, herbivory, mutualism, commensalism, parasitism.
Sampling methods: quadrats, transects, mark-release-recapture (Lincoln index: N = (M × n) / m), and diversity indices such as Simpson's index D = 1 − Σ(n/N)².

Biodiversity and Conservation

Levels of biodiversity: genetic, species, and ecosystem diversity. Values: ecological, economic, cultural, and aesthetic.
Threats: habitat loss and fragmentation, overexploitation, invasive species, pollution, and climate change. Extinction and the IUCN Red List categories.
Conservation: in situ (national parks and sanctuaries such as Yala, Wilpattu, Horton Plains, and Sinharaja; marine reserves) and ex situ (botanical gardens, zoos, seed banks, gene banks). Community involvement and legal protection (Chapter 6 for hotspots).
Human-elephant conflict is a major conservation and livelihood issue in Sri Lanka, particularly in dry zone areas, and requires balanced solutions.

Pollution and Climate

Air pollution: particulates, SO₂, NOₓ, ground-level ozone; acid rain; the greenhouse effect and global warming (CO₂, CH₄, N₂O); effects on sea level, weather, agriculture, and health.
Water pollution: sewage, fertilizers, industrial waste; eutrophication; BOD as a measure of organic pollution; bioaccumulation and biomagnification (for example DDT).
Soil pollution and waste: plastics, e-waste, heavy metals.
Solutions: waste reduction and recycling, wastewater treatment, bioremediation, renewable energy, environmental impact assessment (EIA), and international agreements.

Sustainable Development

Meeting present needs without compromising future generations: integrating environmental protection, economic development, and social equity. Understand the Sustainable Development Goals and the role of individuals, communities, and governments.

Common Mistakes

Treating energy as recycled (it flows and is lost as heat).
Confusing bioaccumulation with biomagnification.
Describing conservation without examples.

CHAPTER 14