2: Biodiversity
Biodiversity is a broad term that encompasses any type of variation that exists in biological systems (Figure 2.1). Though we most commonly discussion biological diversity as variation in the species that occupy the same habitat at the same time, variation exists at all levels of biological organization. A genus that contains many species would have higher diversity than a genus that contains only a few species. The same is true for a family that includes many genera, an order that includes many families, a class that includes many orders, a phylum that includes that many classes, and a kingdom that includes many phyla. Similarly, a species that exhibits a variety of genotypes would be said to have higher genetic diversity than a species with limited variation in genotypes. Also, a single genotype that exhibits a variety of phenotypes (termed plasticity ) would have higher diversity than a genotype that results in only a single phenotype.
Figure \(\PageIndex{1}\):
Schematic of the magnitude and type of diversity exhibited at different scales.
This section focuses on species diversity. Figure by L Gerhart-Barley
Title Image Credit: https://commons.wikimedia.org/wiki/F...coral_reef.jpg
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- 2.1: Species Concepts
- Quantifying species diversity requires developing a definition of a species. We would not expect all members of a species to be identical, so we must consider what magnitude and types of differences between individuals would lead us to consider them members of different species. A species concept is, therefore, a working definition of a species and/or a methodology for determining whether or not two organisms are members of the same species. In this section, we will consider three species concep
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- 2.2: Measuring Species Diversity
- How do we measure species diversity within a habitat? How do we compare diversity across different types of habitats containing very different numbers and types of organisms? There are many mathematical models that have been developed to quantify species diversity in different habitats. While these models differ in the exact method of diversity estimation, they all include two important components: species richness and species evenness.
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- 2.3: Patterns of Global Biodiversity
- Biological diversity is not evenly distributed across the Earth; certain latitudes, ecosystems, and regions contain more diversity than others. There are several factors that influence how many species a given ecosystem supports and these factors lead to predictable patterns of diversity across the globe.
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- 2.4: Global Climate and Biodiversity
- The climate of a region describes the average atmospheric conditions (temperature and precipitation) that region experiences and how much those conditions vary across seasons and years. Climate differs from weather in that weather is the atmospheric conditions at any given moment while climate is the long-term averages, patterns, or trends. This distinction is discussed in more detail in the chapter on climate change.
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- 2.5: Earth's Geologic History and Biodiversity
- Another global influence on biodiversity relates to patterns of geographic connectivity and isolation between regions throughout Earth’s history. Recall that the Earth’s crust is not one uniform piece, but instead split into several pieces, called tectonic plates (Fig 2.3.10). These plates are in motion (represented by the arrows on the map) and so have not always been located in the same place they are today.