Human Body Systems & Ecology

Cells → tissues → organs → organ systems → organism.

Maintaining a stable internal environment (like ~37 °C body temp or ~90 mg/dL blood glucose) despite changes outside the body.

A receptor detects change, a control center compares it to a set point, and an effector pushes back in the opposite direction.

Receptors signal the hypothalamus → sweat glands release sweat and skin blood vessels dilate → heat leaves → temperature falls.

After a meal the pancreas releases insulin so cells take up glucose and the liver stores glycogen; if glucose falls too low it releases glucagon to raise it.

Digestive breaks starch into glucose, circulatory transports it, respiratory supplies O₂ for cellular respiration, excretory removes waste, endocrine/nervous regulate.

A loop that amplifies a change until an endpoint is reached — childbirth contractions and blood clotting.

Organism → population → community → ecosystem → biome → biosphere.

Abiotic are nonliving parts (temperature, rainfall, pH, light); biotic are the living parts of an ecosystem.

Organisms that capture sunlight energy through photosynthesis, bringing energy into nearly every ecosystem.