Ecosystems, Evolution, and Adaptation

The direction energy flows — from the organism eaten to the eater.

Only about 10% of energy passes from one trophic level to the next; ~90% is lost as heat from respiration, in movement, and in undigested waste.

Because so much energy is lost at each level, there isn't enough left to support more trophic levels.

Energy flows one way and is lost as heat; matter (carbon, nitrogen) is recycled in cycles.

Bacteria and fungi break down dead material, recycling nutrients back into the soil and releasing CO₂.

1) Variation from mutation/sexual reproduction, 2) selection pressure/competition, 3) differential survival and reproduction, 4) inheritance of advantageous alleles, increasing allele frequency over generations.

A random mutation makes some bacteria resistant; antibiotics kill the non-resistant ones; resistant bacteria survive and reproduce, passing on the resistance gene. The antibiotic selects for — it does not create — the mutation.

Never say organisms 'wanted' to change or that stretched/acquired traits are inherited — say individuals with the naturally advantageous variation survived and passed on the alleles.

Fossil records, homologous structures (human arm, bat wing, whale flipper), DNA similarities between species, and observed cases like the peppered moth.

Two populations become separated, face different selection pressures, and eventually can no longer interbreed to produce fertile offspring.