Exam 4 part 4 Biomes

Practice vocabulary flashcards covering habitat classification, biogeographic realms, the Holdridge life zone system, island geology, island biogeography theory, and insular evolutionary processes.

Biome

large-scale ecological region defined by its climate, dominant vegetation, and adapted animal communities.

Biogeographic Realm

A large continental or sub-continental area containing multiple biomes where plants and animals share an evolutionary history and long-term genetic lineages.

Antarctic (smallest)

lichens, mosses, hair grass, penguins, whales, squid, and seals.

Shaped by: isolation, extreme cold

Oceanian Realm

the smallest land area of all realms

home to the Great Barrier Reef

shaped by isolation

Indo-Malayan Realm

home to large mammals and numerous endemic species

Australasian Realm

most environmentally diverse

shaped by long geographic isolation and high endemism

diverse bird species, few placental mammals

Neotropical Realm

contains more tropical rainforests

shaped by a long period of isolation and the eventual formation of the Isthmus of Panama.

Afrotropical Realm

Over $200$ endemic fish species, gorillas, chimpanzees

Shaped by Madagascar driven by isolation, high endemism

Nearctic Realm

characterized by canines, equines, and antelopes

shaped historically by repeated glaciations and connections to Eurasia via Beringia.

Palearctic Realm (largest)

Mediterranean climates, coastal deserts, and red pandas, hamsters, and hedgehogs

shaped by climatic gradients and continuous connectivity across Eurasia.

Holdridge Life Zone System

A climate-driven classification of vegetation into $31$ types using bio-temperature, annual precipitation, and evapotranspiration

predicts the vegetation an area can support

doesn’t consider soil or disturbance.

Biotemperature

average temperature relevant to plant growth utilized as a primary climatic axis in the Holdridge Life Zone System.

Potential Evapotranspiration Ratio (PET)

A Holdridge climate variable defined as $\text{PET} = \frac{\text{Potential Evapotranspiration}}{\text{Precipitation}}$, representing the amount of water lost via evaporation and transpiration divided by the total water entering the system as precipitation.

Ecoregion

A large, distinct geographic area defined by integrating recurring patterns of climate, vegetation, soil, and evolutionary history, organized into a hierarchical framework from biomes down to local ecosystems.

Volcanic Island

An island formed from volcanic activity situated over oceanic hotspots or near tectonic plate boundaries (such as Hawaii); initially devoid of terrestrial life.

Continental Island

An island formed from continental crust that became separated from a mainland landmass through geological processes or sea-level rise (such as Madagascar); often harbors ancient lineages that evolve independently from mainland relatives.

Coral Island

A low-lying island formed primarily from calcium carbonate or skeletal debris produced by coral reefs and marine organisms (such as Bikini Atoll); typically characterized by limited freshwater reserves and extreme vulnerability to storm surges and sea-level rise.

Theory of Island Biogeography

An ecological framework stating that island species richness reaches an equilibrium determined by a dynamic balance between immigration (colonization) and extinction (or emigration).

Founder Effect

The loss of genetic diversity and alteration of allele frequencies that occurs when an island is colonized by a small subset of individuals from a mainland population, initiating immediate divergence and accelerated speciation.

Adaptive Radiation

The rapid evolutionary divergence of a single ancestral colonizing lineage into multiple specialized descendant species occupying diverse, vacant ecological niches (e.g., Darwin's finches, Hawaiian honeycreepers, and New Zealand flightless birds).

Island Dwarfism (Miniaturization)

The evolutionary reduction in body size of large mainland animals following island colonization, favored by restricted food resources, an absence of large predators, and the advantage of earlier sexual maturation.

Island Gigantism

The evolutionary increase in body size of small animals following island colonization, driven by the absence of mainland competitors, open ecological niches, and the advantages of larger body size for resource exploitation and territorial defense.

Island Extinction Vulnerability

The disproportionate susceptibility of island biota to extinction—accounting for $60\%$ of all recorded historical extinctions—caused by small population sizes, lack of evolutionary defenses against introduced predators and pathogens, and inbreeding depression.

Island Biosecurity

Targeted conservation and management procedures designed to prevent the accidental introduction or reintroduction of invasive predators and pathogens to island ecosystems.