44.2 Biogeography - Biology 2e _ OpenStax
Learning Objectives
Define biogeography.
List and describe abiotic factors that affect the global distribution of plant and animal species.
Compare the impact of abiotic forces on aquatic and terrestrial environments.
Summarize the effects of abiotic factors on net primary productivity.
The Biosphere
The biosphere encompasses all parts of Earth inhabited by life, extending into the atmosphere and ocean depths.
It occupies a minute space compared to the known universe.
Abiotic factors influence the distribution of biomes which are large land areas with similar climates, flora, and fauna.
Biogeography
Biogeography: The study of the geographic distribution of living organisms and the abiotic factors affecting that distribution.
Abiotic factors such as temperature and rainfall vary based on latitude and elevation.
Changes in abiotic factors lead to changes in plant and animal communities.
Example: Journey from the equator northward shows progression from tropical wet forests to tundra.
Tropical wet forests ➜ Seasonally dry forests ➜ Deserts ➜ Grasslands/Prairies ➜ Deciduous forests ➜ Boreal forests/Taiga ➜ Arctic tundra.
Ecosystem Variation
Different ecosystems can exist at the same latitude due to abiotic factors like jet streams and ocean currents.
Hiking up a mountain showcases changes in vegetation similar to moving towards higher latitudes.
Species Distribution
Patterns in species distribution are influenced by biotic and abiotic factors over long evolutionary periods.
Endemic species: Found only in specific geographic areas (e.g., Venus flytrap in North Carolina).
Generalists: Species that survive in a wide variety of areas (e.g., raccoons in North and Central America).
Unique Biogeographical Patterns
Distinctive assemblages of plants and animals persist in regions separated by geographic barriers.
Australia has 600,000 - 700,000 species, with approximately 3/4 being endemic due to isolation.
Hawaii exhibits unique patterns of species absence despite being tropical (no native reptiles or amphibians).
Endemic and Generalist Plants
Endemic plants are specific to regions (e.g., Hawaiian forest gardenia).
Isolated lands often host unique species.
Human activities threaten the existence of many endemic species.
Energy Sources
Green plants, algae, and other photosynthetic organisms capture solar energy, converting it into chemical energy.
Light availability influences adaptations in photosynthesizers.
Example: Understory plants in forests have adaptations for low light availability.
Light Availability in Aquatic Ecosystems
Aquatic ecosystems have limited light due to absorption by water and particles.
Photosynthesis is restricted to the surface level, leading to adaptations in aquatic plants.
Example: Hydrothermal vent bacteria utilize inorganic chemicals for energy in the absence of light.
Ocean Upwelling
Ocean upwelling brings nutrients from the ocean depths to the surface, vital for marine productivity.
Upwelling occurs when surface waters are displaced by wind, allowing nutrient recycling.
Freshwater Nutrient Recycling
Nutrients in freshwater systems are recycled during spring and fall turnover.
Thermocline formation influences nutrient movement; oxygen-rich water reaches the bottom during turnover.
Temperature Effects on Organisms
Temperature affects metabolism and the distribution of organisms.
Few organisms survive below 0 °C or above 45 °C.
Extremophiles exist in extreme temperatures (e.g., some Archaea in hot environments).
Migration is a common response to seasonal temperature changes (e.g., Arctic Tern's long migration).
Water Requirements
Water is essential for cellular processes; organisms have adapted to retain water.
Adaptations in terrestrial plants reduce water loss, such as leaf hairs and waxy surfaces.
Freshwater organisms regulate solute concentrations to maintain balance.
Nutrient Distribution in Ecosystems
Inorganic nutrients (e.g., nitrogen, phosphorus) influence living things' distributions and abundance.
Soil structure, pH, and nutrient content affect plant growth and distribution.
Animals follow food sources relative to nutrient availability.
Importance of Wind and Fire
Wind influences evaporation rates, nutrient recycling, and organism movement.
Fire can act as a disturbance, enabling certain species to thrive post-fire.
Example: Jack pine requires fire to open its seed cones.
Abiotic Factors Influencing Primary Productivity
Temperature and moisture are crucial for net primary productivity (NPP).
NPP measures organic matter available as food, calculated via carbon fixation rates.
Productive biomes have optimal conditions for photosynthesis and plant growth.
Drier and colder biomes exhibit lower NPP, affecting animal populations.
Learning Objectives
Define biogeography and its significance in ecology.
List and thoroughly describe abiotic factors (such as temperature, light, water, nutrients, and wind) that affect the global distribution of both plant and animal species.
Compare the impact of abiotic forces on aquatic and terrestrial environments, noting specific examples and adaptations.
Summarize the effects of abiotic factors on net primary productivity (NPP) and discuss how it varies among different biomes.
The Biosphere
The biosphere encompasses all parts of Earth inhabited by life, extending from the highest peaks of the atmosphere to the depths of the oceans. It occupies a minute yet critical space compared to the vastness of the known universe.Abiotic factors, such as tectonic activity and climate, significantly influence the distribution of biomes—large areas characterized by similar climates, flora, and fauna, including forests, grasslands, deserts, and tundras.
Biogeography
Biogeography is the scientific study of the geographic distribution of living organisms, considering both the biotic and abiotic factors that influence that distribution.Abiotic factors like temperature, precipitation, and soil composition can vary widely based on geographic variables such as latitude, altitude, and proximity to oceans or mountains.Increases or decreases in these factors often lead to corresponding shifts in plant and animal communities, illustrating a transition. For example, a journey from the equator northward showcases a progression through various ecosystems: tropical wet forests → seasonally dry forests → deserts → grasslands/prairies → deciduous forests → boreal forests/taiga → arctic tundra.
Ecosystem Variation
Different ecosystems can exist at the same latitude due to the influence of abiotic factors like jet streams and ocean currents, which affect climate and weather patterns.For instance, hiking up a mountain reveals significant changes in vegetation and biological communities, mirroring what one might observe moving toward higher latitudes.
Species Distribution
Patterns in species distribution are shaped by both biotic (e.g., competition, predation) and abiotic (e.g., climate, topography) factors over long evolutionary periods.Endemic Species: Species that are found only in specific geographic areas (e.g., the Venus flytrap in North Carolina). Generalists: Species that are adaptable and can thrive in a wide variety of environments (e.g., raccoons found in various habitats across North and Central America).
Unique Biogeographical Patterns
Distinct assemblages of plants and animals persist in regions separated by geographic barriers.For instance, Australia is home to 600,000 - 700,000 species, with approximately three-fourths being endemic due to the continent's long isolation from other land masses.Hawaii also displays unique biogeographical patterns, exhibiting notable species absences (such as native reptiles or amphibians) even in a region that is tropical.
Endemic and Generalist Plants
Endemic plants are unique to specific regions, such as the Hawaiian forest gardenia.Isolated lands often host a variety of unique species, but human activities—such as habitat destruction and climate change—pose significant threats to the survival of many endemic species.
Energy Sources
Green plants, algae, and other photosynthetic organisms play a critical role in capturing solar energy and converting it into chemical energy through the process of photosynthesis.Light availability is a crucial factor that influences the adaptations seen in photosynthetic organisms.For example, understory plants in dense forests develop specific adaptations to thrive in low-light conditions.
Light Availability in Aquatic Ecosystems
Aquatic ecosystems face limitations in light availability due to absorption by water and suspended particles.Photosynthesis generally occurs at the surface level, leading to various adaptations among aquatic plants.For example, hydrothermal vent bacteria can utilize inorganic chemicals for energy, thriving in environments devoid of light.
Ocean Upwelling
Ocean upwelling is an important ecological process that brings nutrient-rich waters from the ocean depths to the surface. This nutrient influx is crucial for supporting marine productivity and sustaining food webs.Upwelling typically occurs when surface waters are displaced by wind, a process that facilitates the recycling of nutrients essential for marine life.
Freshwater Nutrient Recycling
In freshwater ecosystems, nutrients are recycled during seasonal turnover events such as spring and fall. The formation of a thermocline, a layer that separates warmer water from cooler water, influences nutrient distribution. Oxygen-rich water reaches the bottom of lakes during turnover, benefiting many aquatic organisms.
Temperature Effects on Organisms
Temperature is a critical factor affecting both metabolism and the distribution of organisms across the globe.Most organisms cannot survive at temperatures below 0 °C or above 45 °C. However, extremophiles—such as certain Archaea—thrive in extreme temperatures.Migration is a common strategy employed by many species, like the Arctic Tern, which engages in long-distance seasonal migration to adapt to temperature variations.
Water Requirements
Water is vital for various cellular processes, and organisms have adapted various strategies to retain water.In terrestrial environments, plants exhibit adaptations such as leaf hairs and waxy surfaces to minimize water loss.Freshwater organisms, on the other hand, regulate solute concentrations to maintain an internal balance necessary for survival.
Nutrient Distribution in Ecosystems
The distribution and abundance of living organisms are heavily influenced by the availability of inorganic nutrients (like nitrogen and phosphorus).Soil composition, pH levels, and nutrient content play a significant role in determining plant growth and distribution patterns.Animals subsequently follow these food sources, dictated by the spatial availability of nutrients in their habitats.
Importance of Wind and Fire
Wind is another abiotic factor that influences various ecological processes including evaporation rates, nutrient recycling, and the movement of organisms.Fire can act as both a nutrient recycling agent and a natural disturbance, enabling certain species to thrive post-disturbance.For instance, Jack pine trees typically require fire to open their seed cones, facilitating regeneration.
Abiotic Factors Influencing Primary Productivity
Temperature and moisture are critical for determining net primary productivity (NPP)—a measure of the organic matter available as food for other organisms, calculated through carbon fixation rates.Biomes like rainforests and wetlands, which have optimal conditions for photosynthesis and plant growth, demonstrate high NPP. On the contrary, drier and colder biomes tend to exhibit lower NPP, which directly affects the populations of animal species that depend on these plants for food.
Key Terms and Definitions
Biogeography
The scientific study of the geographic distribution of living organisms, including the biotic and abiotic factors affecting that distribution.
Abiotic Factors
Non-living components of the environment that influence the distribution and behavior of living organisms, such as temperature, light, water, nutrients, and wind.
Ecosystem
A community of living organisms interacting with one another and their physical environment.
Endemic Species
Species that are found only in specific geographic areas.
Generalists
Species that are capable of thriving in a wide variety of environments and conditions.
Light Availability
The amount of sunlight that reaches a particular area, influencing photosynthesis in plants.
Ocean Upwelling
An ecological process that brings nutrient-rich waters from the ocean depths to the surface, supporting marine life.
Freshwater Nutrient Recycling
The process through which nutrients are recycled during seasonal changes in freshwater ecosystems, benefiting aquatic organisms.
Temperature Effects
The influence of temperature on the metabolic rates and distribution of organisms, with many unable to survive outside specific temperature ranges.
Water Requirements
The necessity of water for cellular processes, with various adaptations in organisms to retain or utilize water effectively.
Nutrient Distribution
The availability and distribution of inorganic nutrients (like nitrogen and phosphorus) in ecosystems, affecting plant and animal populations.
Importance of Wind
The role of wind in influencing ecological processes, including evaporation rates and the movement of organisms.
Fire as a Disturbance
The role of fire in ecosystems to recycle nutrients and facilitate the growth of specific species that require fire for reproduction.
Net Primary Productivity (NPP)
A measure of the organic matter available as food for organisms in an ecosystem, calculated from carbon fixation rates, influenced by temperature and moisture.