CHAPTER 52 An Introduction to Ecology and the Biosphere

Vocabulary flashcards defining key terms related to factors limiting species distributions, dispersal, and examples from the lecture notes.

Dispersal

Movement of individuals or gametes away from their origin or from centers of high population density; a key factor shaping geographic distribution and enabling range expansion and adaptive radiation.

Range expansion

Expansion of a species’ geographic range into areas where it did not previously exist.

Adaptive radiation

Rapid evolution of an ancestral species into many new species that fill diverse ecological niches, often after dispersal to a new area.

Biotic factors

Interactions with other living organisms (predation, parasitism, competition, disease, pollination, herbivory) that can limit a species’ distribution.

Abiotic factors

Nonliving physical factors (temperature, water, oxygen, salinity, light, soil, moisture) that can limit distribution.

Species transplant

Experimentally moving a species to a new area to test whether dispersal limits its distribution; if successful, the species could live beyond its current range.

Natural range expansions

Real-world dispersal events that extend a species’ range, such as cattle egrets dispersing from Africa to the Americas.

Saguaro cactus (Carnegiea gigantea)

Cactus of the Sonoran Desert; distribution limited by freezing temperatures (tolerates briefly below about -4°C) and water availability; seedling survival requires consecutive moist years; pollinated by bats; susceptible to bacterial disease.

Temperature

Abiotic factor that limits distribution by constraining biological processes; organisms have optimal ranges; climate change can shift distributions; some organisms (thermophiles) tolerate extreme temperatures.

Water availability

Amount and reliability of water accessible to an organism; critically limits survival and distribution (e.g., seedling survival requires consecutive moist years).

Oxygen availability

Concentration of oxygen in the environment; can limit respiration in waterlogged or deeper aquatic settings; some plants have specialized oxygen-delivery roots (e.g., mangroves).

Salinity

Salt concentration in water; affects osmoregulation; most aquatic organisms are restricted to either freshwater or saltwater habitats; migratory species like salmon osmoregulate across salinity gradients.

Sunlight

Energy source for ecosystems; too little limits photosynthesis; shading affects competition for light; high light can cause temperature stress; UV radiation at high elevations can damage DNA and proteins.

Rocks and soil

Soil pH, mineral composition, and physical structure limit plant distribution and thus herbivores; soil phosphorus solubility affects nutrient availability.

Alpine tree line

Upper elevation boundary where trees cannot survive due to a combination of UV exposure, freezing temperatures, moisture deficits, and strong winds.

Cattle egret range expansion

Bird native to Africa that expanded to the Americas in the 19th century via long-distance dispersal; now established across the Americas.

Hawaiian silverswords

Diversity of Hawaiian plants derived from a tarweed ancestor through adaptive radiation after long-distance dispersal.