LWB: Lesson - Introduction to Biodiversity (Topic 2.1) ๐
โณ Estimated Reading Time: 6 - 8 minutes
Explain levels of biodiversity and their importance to ecosystems.
Biodiversity
Biodiversity is the variety of life on Earth at all levels, from genes to species to ecosystems. It is the result of evolution, which is the process of natural selection acting on genetic variation. Biodiversity is important for the health and functioning of ecosystems, as it provides resources, services, and resilience to environmental changes.
There are three types of biodiversity - genetic, species, and habitat diversity. Explore the tabs below to learn more about each type of biodiversity. Each type is critical to biodiversity.
Genetic diversity is when there are a variety of genes present in a reproducing population. Genes occur in different variants (alleles). The more alleles in the population, the more genetic diversity. Individuals carry two copies of every gene, one from each parent. Different populations have different alleles for the gene. Each species has its own set of alleles. Each ecosystem has its own set of genetic diversity. Migration between populations and ecosystems can change the genetic diversity of an area.
Genetic diversity is essential for the resilience and adaptability of ecosystems to environmental changes, enabling some individuals to better survive and reproduce in response to environmental pressures, such as climate fluctuations or new predators. In simpler terms, it's like having a toolbox with a wide range of tools โ the more diverse the tools, the better equipped you are to handle different challenges. Genetic diversity can be influenced by natural selection, mutation, gene flow, and genetic drift. Genetic diversity can be measured by the number of different alleles, genotypes, or phenotypes in a population.
There are several factors influence genetic diversity within populations. Let's take a look at the most common influences on genetic diversity:
Population Size ๐จโ๐ฉโ๐งโ๐ฆ(click to reveal)A population bottleneck is a sudden reduction in the size of a population due to a catastrophic event, such as a natural disaster, disease, or human activity.
One key factor is population size โ smaller populations are more susceptible to genetic drift, a random change in allele frequencies over time. Genetic drift can lead to a loss of diversity, especially in isolated or bottlenecked populations.
This can reduce the genetic diversity of the surviving population, as some alleles may be lost or become more common. Because the alleles that are lost in during the event are not necessarily those least suited to their environment, a bottleneck can reduce a species' survival.
With average global temperatures increasing, cold environments are warming, causing ice to melt. If there was a polar bear that had slightly thinner fur or slightly darker fur, it might be better adapted to a warming environment.
Polar bears are adapted to living in very cold, icy environments.
Because it would not get too hot in a warmer environment and would be better at blending into the new environment, making it easier for it to catch prey. This polar bear would be better adapted to the changing environmental conditions than a โregularโ polar bear, shifting the genetic diversity of the polar bear population. However, because polar bear populations are shrinking, the likelihood of these genes being in the polar bear population also shrinks.
Migration, or gene flow, can also impact population size. When individuals move between populations, they bring new genetic material, increasing diversity. Conversely, isolation can limit gene flow, potentially leading to increased genetic divergence between populations.
Mutations ๐งฌ(click to reveal)Long tails help primate escape predators and reproduce in forests.
Mutations, the random changes in DNA sequences, play a vital role in contributing to genetic diversity. While some mutations may seem unwelcome or harmful, others can actually introduce beneficial traits that enhance a population's ability to adapt to its environment.
It's like a genetic lottery - sometimes you get changes that help you survive and thrive!
The process of natural selection kicks in by favoring individuals with these advantageous traits, ensuring that they pass on their genes to the next generation.
This cycle not only influences the survival of a species but also helps in maintaining or altering genetic diversity based on the unique demands of the organism's surroundings.
For example, a primate born with an especially long tail might be able to escape predators more quickly, making it more likely to survive and reproduce, passing on its long tail gene. If this same long-tailed primate was born in a desert or an ecosystem where the long tail was a liability, not a benefit, the long-tailed primate would likely die early, without reproducing, reducing the likelihood that the long-tail gene would be passed on in the desert population.
Species Diversity
Diversity can be measured by two factors: species richness and species evenness.
Species diversity is when there is a large variety of species present in an ecosystem. An ecosystem is considered healthier and more robust if it has a high species diversity and the species in that ecosystem have a high genetic diversity. Species diversity is important for the health and functioning of ecosystems, as it provides resources, services, and resilience to environmental changes.
Species richness is the number of different species in an ecosystem, while species evenness is the relative abundance of each species. An ecosystem with high species diversity will have high species richness AND species evenness, usually demonstrating increased productivity, resilience to disturbances, and a greater capacity to provide ecosystem services, such as pollination, water purification, and climate regulation.
The video below (without sound) displays the species richness of 1066 marine species that are also important fisheries. You can see that the most species richness is in the shallow areas near the coast, and an especially species rich area, known as the coral triangle, is shown on the map. Unfortunately, many nations in the region around the coral triangle depend heavily on fisheries for their livelihood and economy, with fisheries accounting for over 90% of protein source in some of these countries (Changing Ocean Research Unit, University of British Colombia, Cheung et al. 2009). It can be difficult to balance the need for sustenance in these regions with the need to preserve biodiversity.
Take a look at the video below, can you see where in the world there is the most biodiversity?
There are several factors that influence species diversity within populations. Let's take a look at the two most common influences on species diversity.
Location ๐บ(click to reveal)
The location of the ecosystem can affect the biodiversity of an ecosystem. Let's look at a few ways the location of an ecosystem affects biodiversity. Just tap on the white dots at the bottom to uncover all the details!
Disturbance ๐ฅ (click to reveal)
Disturbance is an interesting factor because intermediate levels of disturbance tend to increase species diversity because they prevent the dominance of a few species and create opportunities for colonization and succession.
This idea is called the intermediate disturbance hypothesis. However, too much or too little disturbance can reduce species diversity, because they can cause extinction (too much disturbance) or stagnation of species (too little disturbance).
Fire is critical to grassland ecosystems. It helps the cycling of nutrients by breaking down dead plant material into ash, which also reduces plant litter.
Fire also controls invasive species because they are not usually adapted to fire. Some species of plants in grasslands have seeds that can only germinate in high heat. It can also create a mosaic pattern in the landscape, with areas of burned and unburned vegetation. This diversity of habitat provides more habitats for animals. Finally, fires prevent the encroachment of woody plants and trees in the grassland. So, the disturbance of a fire is important to this habitat. Without this disturbance, the grassland could evolve into more of a forest landscape. And with too much disturbance, such as human buildings, habitat is lost, reducing the necessary space needed to support a variety of organisms in the area.
Habitat Diversity
Habitat diversity refers to the variety of different ecosystems or habitats that exist within a specific geographic area. Habitat diversity provides a range of resources and conditions to cater to the unique needs and niches of plants, animals, fungi, and other organisms.
Remember our grassland fire ecosystem example?
The fire created a variety of habitats within the ecosystem, allowing for more plant and animal diversity within the grassland. Let's look at some other ecosystems with high habitat diversity, just tap on the white dots at the bottom to uncover all the details!
Habitat diversity is important for maintaining the health and functioning of ecosystems, as it supports a higher level of species diversity and ecosystem services. Loss of habitat leads to a loss of specialist species, followed by a loss of generalist species. It also leads to reduced numbers of species that have large territorial requirements, as smaller habitats cannot support animals that require large ranges, such as lions and tigers. Habitat loss can be caused by natural or human-induced factors, such as natural disasters, climate change, deforestation, urbanization, agriculture, mining, etc.
Biodiversity in an ecosystem includes genetic, species, and habitat diversity.
The more genetically diverse a population is, the better it can respond to environmental stressors.
A population bottleneck can lead to a loss of genetic diversity.
Species richness refers to the number of different species found in an ecosystem.
Ecosystems that have a larger number of species are more likely to recover from disruptions.
Loss of habitat leads to a loss of specialist species, followed by a loss of generalist species. It also leads to reduced numbers of species that have large territorial requirements.
As we study how humans affect the environment during this course, you should always think back to how that disruption can affect the biodiversity of the area.
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