Biogeography: Videos & Practice Problems

Biogeography studies the geographical distribution of organisms, influenced by dispersal, which is the movement of individuals or gametes from their birthplace. Species unable to disperse can become endemic, like polar bears in the Arctic. Ecosystems affect species distribution through biotic factors (e.g., predators, vegetation) and abiotic factors (e.g., temperature, water). Net primary productivity (NPP) indicates ecosystem health, with high NPP supporting diverse life, as seen in the Amazon rainforest compared to the Sahara Desert.

Biogeography

Biogeography is a crucial field that examines the distribution of living organisms across different geographical areas over time. It is closely intertwined with ecology, as the location of species significantly influences ecological interactions and processes. A key concept in biogeography is dispersal, which refers to the movement of individuals or their reproductive cells (gametes) from their birthplace to new locations where they can establish populations. This movement can occur through various means, such as wind or pollinators, especially in species like plants that cannot move on their own.

When a species is unable to disperse, it may become an endemic species, meaning it is naturally found in only one specific area of the world. For instance, polar bears are endemic to the Arctic regions and cannot migrate to the South Pole due to the absence of a land connection, despite similar environmental conditions. In contrast, species like the Arctic Tern, which can fly, are capable of migrating between the North and South Poles, allowing them to inhabit a wide range of locations globally.

This understanding of biogeography highlights the importance of dispersal mechanisms in shaping the distribution of species and their ecological roles. As we continue to explore this topic, we will uncover more about the intricate relationships between organisms and their environments.

Biogeography Example 1

Dispersal is a crucial ecological concept that refers to the movement of individuals or their gametes from their birthplace to new locations, where they can potentially establish new populations and expand the species' range. Understanding the factors that influence dispersal is essential for studying species distribution and ecological dynamics.

When considering factors that impact a species' ability to expand its range during dispersal, several elements come into play. For instance, competition for resources with other species can hinder a species' establishment in a new area, making it a significant factor affecting dispersal. Similarly, the availability of suitable environmental conditions is vital; if conditions are unfavorable, a species will struggle to disperse successfully.

Geographic barriers, such as mountains or oceans, also play a critical role in dispersal. These physical obstacles can prevent species from moving into new areas, thereby limiting their range expansion. In contrast, genetic diversity within a population does not directly impact dispersal capabilities. While genetic diversity is important for the overall health and adaptability of a population, it does not inherently prevent dispersal. Every population exhibits some level of genetic diversity, which is a natural characteristic rather than a limiting factor for dispersal.

In summary, while competition, environmental conditions, and geographic barriers significantly influence a species' dispersal, genetic diversity within a population does not impede this process. Understanding these dynamics is essential for conservation efforts and predicting how species may respond to environmental changes.

How Ecosystems Impact Species Distribution

Ecosystems play a crucial role in influencing species distribution through various biotic and abiotic factors. Biotic factors refer to living components within an ecosystem, such as predators, herbivores, vegetation, competing organisms, pollinators, parasites, and pathogens. The presence, absence, or abundance of these organisms can significantly affect where a species can thrive. For instance, an increase in predators may reduce the population of prey species, thereby altering their distribution.

On the other hand, abiotic factors encompass non-living elements that also impact species distribution. Key abiotic factors include temperature, water availability, sunlight, oxygen levels, salinity, and the composition of rocks and soil. Changes in any of these factors—whether through natural processes or human intervention—can lead to shifts in where species are found. For example, a change in water availability can determine whether a species can survive in a particular habitat.

Understanding the interplay between these biotic and abiotic factors is essential for comprehending how ecosystems function and how species adapt to their environments. This knowledge is foundational for studying ecology and conservation efforts aimed at preserving biodiversity.

Biogeography Example 2

Understanding the distribution of species is crucial in ecology, as no species can thrive in every environment on Earth. The flowchart begins by addressing the question: what limits the distribution of a species? The first consideration is whether the species can disperse, meaning it can move individuals or gametes from their birthplace to new locations. If the species can disperse, there are still factors—either biotic or abiotic—that may restrict its distribution in those new areas.

If the species cannot disperse, then dispersal itself is a limiting factor, indicating that the new area is inaccessible. However, even if dispersal is a limitation, other factors may still affect the species' distribution.

The next step in the flowchart examines biotic factors, which include interactions with other living organisms. If biotic factors are limiting, it is essential to identify which specific factors are at play. These could include predators, parasites, competition, disease, or the type and amount of vegetation present.

If biotic factors are not limiting, then abiotic factors must be considered. Abiotic factors can be further divided into chemical and physical categories. Chemical abiotic factors pertain to the chemical composition of the environment, such as the availability of water, oxygen, salinity, pH, and soil nutrients. In contrast, physical abiotic factors relate to the physical characteristics of the environment, including temperature, light availability, altitude, and climate.

This analysis highlights the complexity of species distribution, emphasizing that both biotic and abiotic factors play significant roles in determining where a species can survive and reproduce. Understanding these factors is essential for ecological studies and conservation efforts.

Which of the following statements about dispersal is correct?

• A. Dispersal can establish new populations and expand the range of the species.
• B. Dispersal only occurs for organisms that can fly, such as birds.
• C. Humans cannot be the cause of dispersal of an animal species.
• D. Animals never play a significant role in plant dispersal.

Answer: (A)

NPP is a Key Factor in Species Distribution

Net Primary Productivity (NPP) is a crucial concept in understanding species distribution and assessing ecosystem health. NPP, often simply referred to as productivity, quantifies the total organic matter available as food within a specific area. A higher NPP value indicates a greater availability of food resources, which in turn enhances an ecosystem's capacity to support diverse life forms and increases overall biomass.

For instance, the Amazon rainforest in northern South America exhibits a very high NPP, signifying abundant organic matter and a rich capacity to sustain various life forms. In contrast, the Sahara Desert in northern Africa has a significantly low NPP, reflecting minimal organic matter and a limited ability to support life. This comparison highlights the stark differences in ecosystem productivity and biodiversity potential across different regions.

Which of the following is the best indicator of net primary productivity (NPP)?

• A. Weather (temperature & precipitation).
• B. Wind speed & direction.
• C. Biodiversity.
• D. Biomass.

Answer: (D)

Here’s what students ask on this topic:

What is biogeography and why is it important in ecology?

Biogeography is the study of the geographical distribution of organisms across space and time. It is important in ecology because it helps us understand how and why species are distributed in certain areas and not others. Factors such as dispersal, which is the movement of individuals or their gametes from their birthplace to new locations, play a crucial role. Understanding biogeography can help in conservation efforts, predicting the impacts of climate change, and managing ecosystems effectively.

How do biotic and abiotic factors influence species distribution?

Biotic factors, which are living components like predators, herbivores, vegetation, competing organisms, pollinators, parasites, and pathogens, can significantly impact species distribution. Changes in these factors can alter the presence, absence, or abundance of species in an area. Abiotic factors, which are non-living components such as temperature, water availability, sunlight, oxygen availability, salinity, and soil composition, also play a crucial role. Variations in these factors can create suitable or unsuitable conditions for species, thus influencing their distribution.

What is net primary productivity (NPP) and how does it relate to ecosystem health?

Net primary productivity (NPP) is an estimate of the amount of organic matter available as food in a specific region. It is a key indicator of ecosystem health because higher NPP values indicate a greater availability of food, which supports more life and biomass. For example, the Amazon rainforest has a high NPP, supporting diverse life forms, while the Sahara Desert has a low NPP, supporting much less life. Thus, NPP helps in assessing the capacity of ecosystems to sustain life.

What are endemic species and what causes them to be endemic?

Endemic species are those that are naturally found in only one specific area on Earth and nowhere else. The primary cause of endemism is the inability of a species to disperse to other locations. For example, polar bears are endemic to the Arctic region because they cannot disperse to the South Pole due to the lack of a land connection. Endemism can also result from unique environmental conditions or evolutionary history that restrict a species to a particular area.

How does dispersal affect the biogeography of a species?

Dispersal refers to the movement of individuals or their gametes from their birthplace to new locations where they can establish new populations. It significantly affects the biogeography of a species by determining where they can live and reproduce. Species with high dispersal capabilities, like birds that can fly long distances, can have widespread distributions. In contrast, species with limited dispersal abilities may become endemic to specific regions. Dispersal influences genetic diversity, population dynamics, and the ability of species to adapt to changing environments.