BIODIVERSITY: CHARACTERISTICS, IMPORTANCE AND EXAMPLES - BIOLOGY - 2024

The biodiversity or biodiversity is the abbreviation of "biodiversity" and refers to the multiple elements of variability present organic beings. This concept can be understood from different levels, be it taxonomic, functional, phylogenetic, genetic or trophic.

A region inhabited by a single species of early age (from an evolutionary point of view), composed of genetically homogeneous individuals, which are distributed in discrete geographical areas and in a narrow range of habitats, will be an ecosystem with low biodiversity.

Biodiversity comprises the different species - and their biological variation - within a region.

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In contrast, a habitat with several species - some ancient, others whose speciation process occurred recently - whose genetic material is heterogeneous and widely distributed, would be a region with high diversity.

However, high and low are relative terms. Therefore, there are several indices and parameters that allow us to quantify the diversity of a region, such as the Shannon and Simpson index, among others. Based on them, we see that the distribution of living organisms is not homogeneous on the planet. More diversity is usually found as we get closer to the tropics.

Biodiversity can be studied using two complementary disciplines: ecology and evolutionary biology. Ecologists focus primarily on the factors that influence local diversity and that operate in short periods of time.

Evolutionary biologists, for their part, focus on higher time scales and focus on extinction events, generation of adaptations, and speciation, among others.

In the last 50 years, human presence, global warming, and other factors have altered the distribution and diversity of a significant number of species. Knowledge and quantification of biodiversity are essential elements for the formulation of solutions to this problem.

What is biological diversity?

The first person to use the term biodiversity in ecological literature was E. O Wilson in 1988. However, the concept of biological diversity has been in development since the 19th century, and is still widely used today.

Biodiversity refers to the diversity of life forms. This extends to all levels of organization and can be classified from an evolutionary or ecological (functional) point of view.

That is, diversity is not only understood in terms of the number of species. Variability at other taxonomic and environmental levels also has an influence, as we will see later.

Biodiversity has been studied since Aristotelian times. The intrinsic curiosity about life and the need to establish order led philosophers to study the different forms of life and to establish arbitrary classification systems. Thus were born the sciences of systematics and taxonomy, and therefore the study of diversity.

Biodiversity characteristics

Genetic diversity

Biological diversity can be studied at different scales, starting with genetics. An organism is made up of thousands of genes grouped together in its DNA, which is organized inside its cells.

The different forms that we find of a gene (known as alleles), and the variations in chromosomes between individuals constitute genetic diversity. A small population whose genome is homogeneous among its members is somewhat diverse.

The genetic variability that we find among individuals of the same species is the result of a series of processes such as: mutations, recombination, genetic polymorphisms, isolation of the gene pool, local selective pressures, and gradients, among others.

Variation is the basis for evolution and for the generation of adaptations. A variable population can respond to alterations in environmental conditions, while the little variation can translate into population decline, or in extreme cases could lead to the local extinction of the species.

Furthermore, knowledge of the degree of genetic variability of a population is essential if effective conservation plans are to be established, since this parameter affects the resilience and persistence of the species.

Individual diversity

At this level of organization we find variation in terms of anatomy, physiology, and behavior in individual organisms.

Population diversity

In biology we define populations as a set of individuals of the same species that coexist in time and space, and that can potentially reproduce.

At a population level, the genetic variation of the individuals that comprise it contributes to biodiversity and, again, is the basis for adaptive evolution to occur. A clear example of this is the human population, where all individuals present appreciable phenotypic variations.

Species that lack genetic variation and have uniform populations are more prone to extinction, both from environmental and human-induced causes.

Diversity at the species level

If we move up the organization level, we can analyze biodiversity in terms of species. Biodiversity is often studied by ecologists and conservation biologists at this level.

Diversity above the species level

We can continue to analyze biodiversity above the species level. That is, taking into account other levels of taxonomic classification such as genera, families, orders, etc. However, this is more common in studies related to paleontology.

Thus we can go upward in scale, until we find the comparisons made by biogeography, which is nothing more than the recognition of a differential richness of species in large geographic regions.

How is biodiversity measured?

For biologists it is important to have parameters that allow the quantification of biodiversity. To accomplish this task, there are different methodologies, which can be measured from a functional or theoretical perspective.

Functional measurement categories include genetic, species and ecosystem diversity. The theoretical perspective is based on alpha, beta and gamma diversity. Similarly, a community can be evaluated by describing its physical attributes.

The use of statistical indices that measure the diversity of species is common. These combine two important measures: the total number of species in the sample and their relative abundance. Next we will describe the measures and indices most used by ecologists.

Alpha, beta and gamma diversity

Alpha, beta and gamma diversity are the three levels of diversity recognized by the IUCN (International Union for Conservation of Nature). This approach was proposed by plant ecologist Robert Harding Whittaker in 1960 and is still in use today.

Alpha diversity is the number of species at the local level, that is, within a habitat or ecological community. Beta is the difference in species composition between communities. Finally, the gamma shows the number of species at the regional level.

However, this division faces a drawback when we are going to define the local area and how we can objectively delineate a region - beyond mere political boundaries that are biologically meaningless.

Boundary setting is affected by the study question and the group involved, so the questions above have no obvious answer.

In most ecological studies related to biodiversity, the emphasis is usually on alpha diversity.

Alpha diversity

Alpha diversity is generally expressed in terms of species richness and species equity. During the sampling carried out, the place or area that the researcher chooses represents the entire community. Thus, making a list of the number and name of the species that live there is the first step in measuring the biodiversity of an area.

The number of species within a community or area is the species richness. Knowing this parameter, we proceed to analyze other criteria, namely: taxonomic uniqueness, taxonomic divergence, ecological significance, and interactions between species, among others.

Generally, species richness - and biodiversity in general - increase when we expand the area we are analyzing or when we move from a greater to a lesser longitude and latitude (to the equator).

We must take into account that not all species contribute in the same way to the diversity of the area. From an ecological point of view, the different dimensions of biodiversity are represented by a number of trophic levels and a variety of life cycles that contribute differently.

The presence of certain species in the area has the capacity to increase the diversity of an ecological community, while that of others does not.

Beta diversity

Beta diversity is a measure of diversity between communities. It is a measure of the rate and degree of change in species over a gradient or from one habitat to another.

For example, this measure would study the comparison of diversity along the slope of a mountain. Beta diversity also emphasizes the temporal change in species composition.

Gamma diversity

Gamma diversity quantifies diversity from a higher spatial level. This is in charge of explaining the diversity of species within a wide geographic range. Basically, it is the product of alpha diversity and the degree of differentiation (beta) between them.

Thus, gamma diversity is the rate at which additional species are found and studies their geographic replacement.

Species diversity indices

In ecology, diversity indices are widely used, with the aim of quantifying it using mathematical variables.

A diversity index is defined as a statistical summary that measures the total number of local species that exist in different habitats. The index can be either dominance or equity (the term evenness is used in English).

Shannon diversity index

The Shannon index, or Shannon-Weaver index, is popularly used for the measurement of specific biodiversity. It is represented using an H ', and the index values ​​fluctuate only between positive numbers. In most ecosystems the values ​​are from 2 to 4.

Values ​​below 2 are considered relatively not very diverse, for example in a desert. While values ​​greater than 3 are indicative of high diversity, such as a neotropical forest or a reef.

To calculate the value of the index, the number of species (richness) and their relative number (abundance) are taken into account. The maximum value of the index is usually close to 5 and the minimum value is 0, where there is only one species - that is, there is no diversity. An ecosystem with a Shannon index 0 can be a monoculture.

Simpson diversity index

The Simpson index is represented by the letter D, and measures the probability that two randomly selected individuals from a sample belong to the same species - or to another taxonomic category.

In the same way, Simpson's diversity index is expressed as 1 - D (the index explained in the previous paragraph). The value is between 0 and 1 and, contrary to the previous case, it represents the probability that two individuals taken at random belong to different species.

Another way to express it in using the reciprocal index: 1 / D. In this way, the value of 1 translates into a community with only one species. As the value increases, it is indicative of greater diversity.

Although the Shannon index and the Simpson index are the most popular in ecological literature, there are others such as the Margalef, McIntosh, and Pielou index, among others.

Why should we quantify biodiversity?

In the previous section we described in great detail the different mathematical tools that ecologists have for the quantification of biological diversity. However, what are these values ​​useful for?

Biodiversity measurements are essential if you want to monitor how diversity fluctuates, as a function of environmental changes that degrade ecosystems, both naturally produced and man-made.

Biodiversity as a result of evolution: how is biological diversity generated?

Life on Earth began at least 3.5 billion years ago. During this period of time, organic beings have radiated in the various forms that we observe on the planet today.

Different evolutionary processes are responsible for this enormous diversity. Among the most important we have the following: liberation from competition, ecological divergence and coevolution.

Liberation from competition

Various studies, focused on both current and extinct species, have shown that lineages of organisms tend to diversify rapidly if there are ecological opportunities - that is, “vacant” niches.

When a group of organisms colonizes a region free of predators and with little competition (an uninhabited island, for example) it tends to diversify, occupying the available ecological niches. This phenomenon is called adaptive radiation.

For example, after the extinction of the dinosaurs, multiple free niches remained that were later occupied by radiation from mammals.

Ecological divergence

There are key adaptations that allow organisms to occupy a number of ecological niches. These organisms occupy the same adaptive zone, so they occupy similar “ecological spaces”. When two species share very similar ecological niches, competition increases between them.

According to ecological theories, two species cannot compete indefinitely because one species will end up displacing the other. Another possible scenario is that one of the species is capable of exploiting another resource, with the aim of reducing competition with its partner.

In this way, the ability of species to exploit new resources and use new habitats has contributed to the increase in biological diversity over time.

Coevolution

The different interactions that can exist between organisms of different species have evolutionary consequences and are responsible for part of the biodiversity. Some species provide resources for their mates. Thus, the diversification of one of these translates into the diversification of the other species.

The coevolution between predators and their prey is also considered as a source of diversity. If the predator generates a novel adaptation, this is (in some cases) accompanied by an adaptation in the prey.

A very illustrative example of coevolution and biodiversity is the high number of angiosperms, related to the diversity of their invertebrate pollinators.

Importance

Human society depends on biodiversity in several ways. Generally, the value of biodiversity can be a subjective concept and depends on each person, so this value is classified as an intrinsic or inherent value and an instrumental or extrinsic value.

Intrinsic and extrinsic value

An extrinsic value is determined by the use or application that it may have in human society - such as the production of food, medicine, among others. Similarly, extrinsic value could apply for benefits to other living things, but humans are often taken into account.

For example, various insects, birds, and mammals play pollinator roles in ecosystems, mediating the reproduction of a significant number of economically important plants. Examples of this are bees and bats.

In contrast, the intrinsic value of biodiversity is alien to the ecosystem services that living beings can provide to the environments. It starts from the premise that every organism has the right to life, just as humans have it.

This value is not related to the appearance or aesthetics of the organism, since this parameter is part of the extrinsic values. Since the concept has a strong philosophical component, it is characterized by being difficult to understand. Some economists, for example, believe that their definition is incomplete.

Other classifications

There are other ways of classifying the importance of biodiversity, distinguishing between organisms with some economic value for the market and those that lack such value.

Other classifications are more complex and include more categories. For example, the classification proposed by Kellert (1996) includes nine categories: utilitarian, naturalistic, ecological-scientific, aesthetic, symbolic, humanistic-moralizing, dominionist, and oppositional.

Biodiversity in Latin America

In Latin America we find an extensive biological diversity. Currently, a large number of the ecosystems of these regions are threatened, mainly by anthropogenic factors.

For this reason, in most countries there are protected areas such as parks, reserves, sanctuaries and natural monuments that seek to protect the species of the region.

Below we will describe the biodiversity of the most relevant Latin American countries, with the greatest global diversity.

Biodiversity in Mexico

Mexico, in terms of the number of species, is an extremely diverse country that reaches almost 70,000 species of animals and plants, of which more than 900 are endemic to the region. It occupies one of the first positions in terms of its diversity worldwide.

This vast biodiversity is attributed to several factors, mainly the country's complex position and topography, and climatic diversity. At the ecosystem level, Mexico is equally diverse, presenting all kinds of natural environments and ecoregions.

Biodiversity in Colombia

This megadiverse country has more than 62,000 species, several of them endemic to Colombia. It houses the largest number of species of birds and orchids in the world.

With regard to ecosystems, we find a wide diversity of regions. Colombian diversity is usually grouped into the so-called "diversity hot spots", which correspond to the Andean and Tumbes-Chocó-Magdalena regions.

Biodiversity in Peru

Thanks to its relief and geographical location, Peru is a country of great biodiversity. In fact, it is also within the megadiverse countries. Many of its species are endemic to the region.

It is varied in terms of the ecosystems it presents, with typical ocean species (influenced by the Niño and Humboldt currents), coastal deserts, different types of forests, puna, mangroves, prairies, paramo, Amazon, and savannas, among others..

Biodiversity in Argentina

Argentina is a country characterized by a high biodiversity that makes life in its immense geographical territory. With mountain environments, savannas, and subtropical climates, Argentina is home to a large number of plants and animals, highlighting the presence of big cats and aquatic mammals.

Biodiversity in Venezuela

Venezuela is a megadiverse country with more than 20,000 species of animals and plants distributed throughout the territory. As in the aforementioned countries, diversity is often attributed to climatic and topographic heterogeneity.

In terms of ecosystems, Venezuela exhibits all kinds of regions, including forests, plains, páramos, savannas, mountains, deserts, etc., each with its typical group of species. As in the previous countries, a large number of the species are endemic to the region.

Biodiversity in Europe

Biodiversity in Spain

Spain stands out for having one of the largest biodiversity in all of Europe, highlighting the presence of mammals and reptiles.

Its condition of peninsula gives it a wide variability in terms of climate, this being a decisive factor in the number of species and differentiating it from the rest of Europe. The mountainous relief is also an important variable.

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