Ecology, the Biosphere and Human Influence on Nature
Ecology studies relationships of organisms with each other and with the environment. Key concepts: ecosystem (biogeocoenosis) - a community plus its abiotic environment; biocenosis - living components; biotope - physical environment. Organisms interact as producers (autotrophs), consumers (herbivores, carnivores) and decomposers (bacteria, fungi). Food chains transfer energy; only about 10% passes to the next trophic level, so chains are short and top predators are few.
Environmental factors are abiotic (light, temperature, water, soil), biotic (predation, competition, symbiosis) and anthropogenic (human impact). Populations are described by size, density, age and sex structure. The biosphere is the global living shell, and the biogeochemical cycles of carbon, nitrogen, oxygen and water link organisms and environment.
Human influence includes pollution, deforestation, habitat destruction, overhunting and introduction of invasive species; conservation includes protected areas, recycling, sustainable resource use and species protection. Sustainability means using resources so they remain available for future generations.
Traps
Confusing a food web with a food chain; placing decomposers at the start of a chain; ignoring that energy flows one way while matter cycles. Also, "anthropogenic" means human-caused, not biotic.
Worked example
"Grass → rabbit → fox. If grass stores 10 000 kJ, how much energy reaches the fox?" Each step passes ~10%: rabbit gets 1 000 kJ, fox gets 100 kJ.
Evolutionary Doctrine, Patterns of Evolution and Biogeocoenology
Evolution is the historical development of life. Darwin's theory rests on hereditary variability, the struggle for existence and natural selection, which preserves favourable traits. Evidence comes from palaeontology (fossils), comparative anatomy (homologous and analogous organs, rudiments, atavisms), embryology and molecular biology. Microevolution acts within populations (changes in allele frequencies); macroevolution produces new species and larger groups. A population is the elementary unit of evolution; mutation, migration, genetic drift and selection change gene frequencies. Speciation occurs when populations become reproductively isolated.
Patterns of evolution: divergence (common ancestor → different forms), convergence (similar traits in unrelated groups), parallel evolution, and directions such as aromorphosis (major advance), idioadaptation (fine adaptation) and degeneration (loss of structures in parasites). Biogeocoenology studies ecosystems as self-regulating systems: stability depends on species diversity, food-web complexity and self-regulation; ecosystems pass through succession toward a climax community.
Traps
Confusing homologous (common origin, different function) with analogous (different origin, similar function) organs; calling individual variation "evolution"; and confusing aromorphosis with idioadaptation. Also, natural selection acts on phenotypes, not directly on genes.
Worked example
"Wings of a bird and wings of a butterfly." Different origin, same function → analogous organs, evidence of convergence, not of close kinship. Bird and bat forelimbs, by contrast, are homologous.