Terrestriality

Terrestriality is the state or condition of living on land, as distinct from aquatic or aerial habitats. In biology it denotes the set of adaptations that enable organisms to grow, reproduce, and maintain water balance on solid ground.

Plants that colonized land developed waxy cuticles, stomata, and vascular tissues to conserve water and move resources. Supportive tissues such as lignified xylem and phloem enabled upright growth. Reproduction also changed, with pollen and seeds providing protection from desiccation and greater opportunities for dispersal on land.

Animals that became terrestrial developed limbs for movement, lungs or efficient respiration, and skin or exoskeletons that reduce water loss. In amniotes (reptiles, birds, mammals), internal fertilization and amniotic eggs further lessened dependence on water for reproduction.

Evolutionary significance: The shift to land occurred at different times in plants and animals and drove major diversification, soil formation, and nutrient cycling. Terrestrial ecosystems now cover most of Earth's land area, but face threats from climate change, habitat loss, and desertification.