Environmental Science course

1. 1.Ecosystems and Energy Flow

   An ecosystem is a community of living things together with its physical environment, linked by flows of energy and cycles of matter. Energy enters mostly as sunlight captured by producers, passes to consumers through food chains and food webs, and leaves as heat. Matter, such as carbon and nitrogen, cycles and is reused.

   • Trophic levels: producers, primary consumers (herbivores), secondary and tertiary consumers.
   • Decomposers return nutrients from dead matter to the soil.
   • The 10% rule explains energy pyramids.
   Quick check: With the 10% rule, energy reaching herbivores from 8000 kcal of plants?

   $800$ kcal

   Includes a worked example, 3 common mistakes and 3 practice questions with answers. Study ecosystems and energy flow

2. 2.Human Population

   Population ecology studies how the number of individuals of a species changes over time. With unlimited resources a population grows exponentially, $\frac{dN}{dt} = rN$, doubling in a fixed time. Real environments run short of food, space and other resources, so growth slows as the population approaches the carrying capacity $K$.

   • Exponential growth: $N = N_0 e^{rt}$; doubling time $\approx \frac{0.693}{r}$.
   • Density-dependent factors (competition, disease) strengthen as the population grows.
   • Density-independent factors (storms, fires) act regardless of population size.
   Quick check: Doubling time when $r = 0.05$ per year, to one decimal.

   $13.9$ years

   Includes a worked example, 3 common mistakes and 3 practice questions with answers. Study human population

These topics belong to the course outline. Full explainers for them have not been written yet, so they are summarised here rather than given pages of their own.

Energy Resources

Renewable and non-renewable energy and efficiency.

Pollution and Climate Change

Greenhouse gases and air and water quality.

• Environmental Science overview
• All subjects