Biodiversity

Earth is home to a vast array of different plants, animals, and microorganisms battling to survive in conditions ranging from the dense rainforests in the tropics to barren Sub-Saharan deserts. Biodiversity encompasses the multitude of ecosystems worldwide and the diversity within and between the different species that reside in them. Greater global biodiversity is beneficial to Earth's population as over a third of the world's population relies on marine or coastal biodiversity for their employment; it provides the world with sustained food security and also provides vital information for medical research - 25% of drugs used in modern medicine are derived from rainforest plants!

Biodiversity Biodiversity

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Table of contents
    • What is biodiversity?
      • Key terms in biodiversity
    • Importance of biodiversity
    • Loss of biodiversity
      • Habitat change
      • Invasive species
      • Nutrient loading
      • Pollution
      • Climate change
    • Conservation of biodiversity
    • Biodiversity net gain
    • Species diversity
    • Biodiversity examples
      • Rainforests
      • The Great Barrier Reef
      • Grasslands
      • Kelp Forests
    • Investigating biodiversity
      • Investigating biodiversity in DNA and RNA
      • Investigating the amino acid sequence
      • Quantitative investigation used in biodiversity
      • Qualitative research
      • Advantages of quantitative research over qualitative research

    What is biodiversity?

    Biodiversity is the measure of the variation in different species and genetics in a particular habitat or the whole world. Greater biodiversity (a wide range of different species, habitats and gene pools) results in thriving communities and ecosystems.

    Biodiversity has a beneficial impact on the health of the planet, as many species and habitats coexist in a fragile equilibrium and depend on other species to prosper. Diversity in the genetic composition of a habitat makes it more resilient to climate or human changes in or around it.

    A community is a group of organisms that live in the same habitat and interact.

    Communities are often mistaken for ecosystems. But remember, an ecosystem describes the community as well as the physical environment the organisms reside in.

    Key terms in biodiversity

    These are some key terms that are important when considering biodiversity. Let's go through some definitions.

    • Species diversity is the variety of species and abundance of each of these species in a particular community. This can be measured using a diversity index, which provides information about the distribution and rarity of a certain species in an area.
    • Genetic diversity refers to the variation and size of the gene pool in a community.
    • Ecosystem diversity is the variation in habitats offered to the species in a certain area.
    • Background extinction rate is the expected number of species that would go extinct over a certain period due to natural causes; human interaction has severely augmented this rate.
    • Mass extinction events are events in which a large number and variety of species become extinct because of a catastrophic occurrence.

    An example of an extinction event is the Cretaceous-Paleogene extinction when the entirety of earth's dinosaur population became extinct.

    • Keystone species are species that have a substantial effect on the rest of the community relative to their numbers.
    • Species richness refers to the number of different species in a particular area at any given time.
    • Endemic species refers to a certain species' population growing in geographical isolation, for example on an island.

    Importance of biodiversity

    Biodiversity is important because it allows the species and habitats on planet Earth to thrive as they depend on each other. Still, biodiversity affects the world in many other ways:

    • Plant-rich ecosystems are beneficial to the environment as plants absorb carbon dioxide from the atmosphere and provide humans with energy directly (fruit and vegetables) and indirectly (meat). Microorganisms feed on the abundance of waste produced by animals as well.

    • Morally humans have to protect the planet on which we live. Maintaining biodiversity also preserves the beauty of the world around us.

    • Economically, ecosystems can be beneficial to the world. Plants, fungi and bacteria have been the source of numerous scientific discoveries, and wildlife and national parks are tourist attractions in many countries.

    • Biodiversity is helpful in agriculture as most crops that grow on farms have very low genetic diversity and are susceptible to disease. The wild crops surrounding provide genetic diversity through disease-resistant alleles that are shared through breeding.

    Without biodiversity, plant, animal and human life would be impossible.

    Loss of biodiversity

    Loss of biodiversity refers to the reduction of species and genetic variability in the world as a whole, or in a particular habitat. As we saw in the previous section, biodiversity is crucial for the health of an ecosystem, so its decrease can have severe negative consequences on the health of the habitat, the remaining species, and even the whole world.

    For example, the decrease in biodiversity in tropical rainforests can dysregulate that habitat and reduce the habitat's trees and tree density. This affects the entire planet because rainforests are one of the world's hubs for carbon dioxide reabsorption. Changes in biodiversity or species present in the rainforests can also impact the local economies.

    There are many threats to biodiversity; these include habitat change, pollution, natural disasters and others. Let's have a look at each of them in more detail

    Habitat change and biodiversity

    The habitats that species rely on can change suddenly or gradually, by natural causes or human impacts. Habitat change is a natural process, but it can be accelerated by humans. Seasonal changes often affect the habitat due to changes in rainfall, causing flooding, droughts, and migration of prey or species with mutually beneficial relationships. However, human intervention or natural disasters can make a habitat change in ways to which species are not adapted.

    One interesting example of a mutually beneficial relationship between organisms in an ecosystem is the symbiotic relationship between the coral polyps which build up the calcareous exoskeleton of the coral reef and the zooxanthellae (dinoflagellate algae) which are attached to them. The zooxanthellae contain a coloured pigment while also providing the coral polyps with essential nutrients to build up the structure of the reef. Overheating of the coral from sweltering warm seasons causes the coral polyps to expel the zooxanthellae because of this thermal stress, decolouring the coral and causing the exoskeleton to be more fragile. This phenomenon is referred to as coral bleaching.

    Biodiversity, a coral reef some parts show bleaching zooxanthellae expulsion, symbiotic relationship example, StudySmarter

    Fig. 1. A coral reef. Some parts show bleaching

    Natural disasters and biodiversity

    A natural disaster is a catastrophic event that occurs naturally. Natural disasters like earthquakes, hurricanes, forest fires or tornados can occur in many parts of the world. Habitats can also be altered by human development around these areas.

    Deforestation, mining and agricultural processes all heavily impact ecosystems worldwide by destroying their habitats.

    Invasive species are foreign species introduced into a community that can have detrimental effects on other, native species of that environment. This could be because of new competition for food, the introduction of a new predator or of a species carrying a disease.

    An example of this is the European rabbit introduced in 1800 into Australia. This species quickly went through a population explosion. They lacked predators, which allowed this prey species to thrive. There was even a disease, called myxoma, which was released to control the population.

    Nutrient loading is the excessive addition of nutrients like phosphorus or nitrogen, to a body of water. Even though adding more nutrients might sound beneficial, the excess of them allows for the exceeding growth of algae that end up stealing the light and oxygen of other plants and animals in the water.

    A common way of nutrient loading happens through the runoff of fertilisers from farmlands. The fertilisers get rinsed from the agricultural plots and into nearby rivers, lakes, etc. Thus, the increased use of fertiliser by farmlands can reduce biodiversity in the surrounding fields.

    Eutrophication is the excessive increase in the nutrient content of bodies of water. This increase results in the surging of aquatic plant populations, which use up the dissolved oxygen in the water.

    Algal bloom, eutrophication, loss of biodiversity, StudySmarter

    Fig. 2. Algal bloom. Source: Unsplash.

    Atmospheric nitrogen can also damage rivers and lakes through eutrophication, sulphur can lead to excessive acid in lakes, ozone damages plant leaves, and heavy metal compounds emitted from cars can accumulate in both plants and animals.

    Apex predators are some of the fiercest animals at the top of the food chain but can be seriously affected by microplastics! Because they are at the top of the food chain, they acquire microplastics from all trophic levels through direct ingestion and trophic transfer. These microplastics can potentially impact animals' behaviour and hormones. Erratic behaviour is not helpful when trying to survive in the wild; predators must be efficient when hunting prey and expending energy.

    Climate change has a negative impact on temperature, and weather patterns; therefore, it can potentially decrease diversity through droughts, forest fires, melting of icy habitats, and may even cause some animals to migrate away from their historical habitats in search of cooler areas.

    Biodiversity, climate change effects on earth, StudySmarter

    Fig. 3. Representation of climate change effects on our Earth

    Conservation of biodiversity

    The conservation of biodiversity is crucial for the health of planet Earth. Without biodiversity, ecosystems would become very unstable and would not be able to support plant, animal or human life. On top of that, biodiversity is helpful for human economic activity too.


    Because of the threats to biodiversity that were discussed earlier, biodiversity is decreasing in communities worldwide. Humans can help to rectify this in various ways:


    • Captivity - some species are under such threat and are now at such low numbers that the only way to save them is to breed them in captivity until there is a strong enough cohort to be released into the wild. Botanic gardens are the equivalent as they keep plants in captivity and are invaluable to scientific research.

    • Conserved areas- national parks and marine sites are protected from human interference by law.

    European Marine Sites (EMS) are areas at sea situated to protect important habitats and ecosystems. They form a chain of protected areas around Europe that protect many marine species.

    • Reducing invasive species by human causes - invasive species can be brought into an area where they do not belong by vehicles like planes and boats. These species can then out-compete and sometimes even prey on other species.

    • Sustainable living - we can help reduce climate change by living more sustainably, minimising driving, and being more energy efficient in the house. Increasing our carbon footprint also helps to prevent global warming.

    Biodiversity net gain (BNG) is an initiative carried out by the UK government to offset and counterbalance any biodiversity loss derived from development activities. The BNG establishes that all new development and land use must ensure a 10% net gain of biodiversity compared to the initial situation. BNG will be mandatory for any development or land use permissions starting in November 2023.

    BNG initiatives include creating or restoring habitats, or improving the quality of existing habitats. The BNG underlines a change in mindset: instead of aiming to reduce the negative impacts of human activity on biodiversity, the BNG asks that biodiversity loss is completely avoided or counteracted.

    Species diversity

    Species diversity considers the number of different species in a community, as well as the concentration and spread of these species. Having a greater species diversity helps ecosystems survive unexpected environmental changes and be more equipped to deal with the introduction of a new species of predators or disease-carrying parasites.

    Species richness is one method of measuring species diversity, but this only tells us the number of different species in a particular area. The population density and spread of each species would also have to be measured to give us an idea of the relationships between different species and how the ecosystem functions.

    Rising sea levels and increased water salinity resulting from global warming damage habitats used to breed and nurture offspring, so these species have to migrate.

    Simpson's Diversity Index

    Simpson's Diversity Index or a species index of diversity measures the number of different species in a community, their relative abundance and how they contribute to the survival of the other species that live with them in that community through various mutually beneficial and harmful relationships.

    The formula for measuring the index of diversity is as follows:

    \[D = 1 - (\frac {n(n-1)} {\sum{N(N-1)}})\]


    Where:

    D= index of diversity

    N= total number of organisms of all species

    n= total number of organisms of each species

    Σ= sum of

    Biodiversity examples

    There are many examples of biodiverse ecosystems on planet Earth. Let's have a look at some of them to be inspired by their beauty!

    Rainforests - A Treasure Trove of Life

    Rainforests are an example of the incredible biodiversity on our planet. These lush, tropical forests are home to an incredible variety of plant and animal species, many of which are found nowhere else on Earth. Rainforests are also important sources of food, medicine, and other resources for local communities.

    rainforest, studysmarterFig. 4. Luscious plants in a rainforest. Source: Unsplash

    However, rainforests are under threat from human activities such as deforestation, mining, and agriculture. Many species are endangered or at risk of extinction due to habitat loss and fragmentation. Protecting rainforests is essential for preserving the incredible biodiversity they contain and ensuring that future generations can benefit from their many resources.

    The Great Barrier Reef - A Natural Wonder of the World

    The Great Barrier Reef is one of the most famous and awe-inspiring examples of biodiversity on our planet. This enormous coral reef system stretches over 2,300 km along the coast of Australia and is home to an incredible array of marine species. The reef is made up of over 2,900 individual coral reefs and 900 islands. It is also home to more than 1,500 species of fish, 400 species of coral, and countless other marine organisms.

    Corals, Great barrier reef, studysmarterFig. 5. Examples of coral types. Source: Unsplash.

    The Great Barrier Reef is not only an important ecosystem but also a popular tourist destination, generating millions of dollars for the Australian economy each year. However, like many other coral reefs around the world, the Great Barrier Reef is under threat from human activities such as climate change, pollution, and overfishing.

    Grasslands - A Diverse Home for Grazing Animals

    Grasslands are vast areas of open, grassy plains that cover about a quarter of the Earth's land surface. In other words, they are ecosystems where grass is the main type of vegetation. They are found on every continent except Antarctica and are home to a wide range of grazing animals such as bison, antelope, gazelles, and zebras. Grasslands are also home to many species of birds, insects, and small mammals. They are adapted to fire and drought, and have evolved complex root systems to capture nutrients and moisture from the soil.

    Grasslands, StudySmarterFig. 6. Example of a grassland. Source: Unsplash.

    Unfortunately, grasslands are under threat from human activities such as agriculture, urbanization, and grazing. Conservation efforts are important for preserving the biodiversity of grasslands and the important ecosystem services they provide, such as carbon sequestration and soil stabilization.

    Kelp Forests - A Diverse Underwater Habitat

    Kelp forests are underwater ecosystems dominated by large, brown seaweeds called kelp. They are found in cold, nutrient-rich waters around the world, including the west coast of North America, southern South America, southern Africa, and Australia.

    Kelp forest, StudySmarterFig. 7. Kelp forest. Source: Unsplash.

    Kelp forests provide a diverse habitat for many marine species, including fish, invertebrates, and mammals such as sea otters. They also provide important ecosystem services such as carbon sequestration and wave attenuation. Like coral reefs and other marine ecosystems, kelp forests are under threat from human activities such as pollution, overfishing, and climate change.

    As you can see, many of the incredible ecosystems we have on Earth are currently under threat due to human activity and climate change. It is essential for the plant and ourselves as a species that we counterbalance the damage done and reduce or avoid it altogether in our future development strategies. Without a healthy planet, human life is also at risk.

    Investigating biodiversity

    Investigating biodiversity includes collecting and analysing data on the variety of species present in a specific habitat, and understanding the relationships between species. This might include collecting and cataloguing specimens, measuring population sizes and changes in them, and observing the behaviour of animals in their natural habitat.

    Another strategy to investigate biodiversity is the analysis of the species' DNA. The DNA of various species can be extracted and then subsequently analysed by computers to determine the precise sequence of nucleotides.

    Investigating biodiversity in DNA and RNA

    DNA sequencing consists in reading the nucleotide sequence of a strand of DNA. The nucleotide sequence determines the genes expressed by an organism, and thus also determines what an organism looks like. By sequencing the DNA of multiple organisms if a species, we can better understand what the genetic variability within an ecosystem is, and what are the fundamental units that are preserved within all organisms of the same species.

    If you want to know more about DNA sequencing, check out our article on DNA Cloning.

    DNA sequences also serve to compare the genetic sequences of different animals and see how closely related they are:

    • Similar sets of gene sequences tell us that the animals are closely related.

    • A higher percentage of similarity between DNA sequences corresponds to a closer relationship between organisms.

    • This is because animals with the same evolutionary ancestors would have had the same genetic sequence, but mutations over time would change this sequence little by little.

    • Two organisms with similar genetic sequences must have evolved fairly recently to form new species.

    • Evolutionary family trees can easily be produced from this information, so DNA analysis is extremely useful in finding out about the evolutionary history of organisms and the relationships between them.

    • Studying mitochondrial DNA is very beneficial to scientists due to the minimal crossing over in mitochindrial DNA, so the evolutionary patterns are much clearer.

    • Mitochondrial RNA is often used in DNA analysis because it is so easy to extract and can be used to produce a complementary DNA (cDNA) strand, the same as the original template strand of the DNA. This cDNA can then be used to make another complementary strand that is identical to the coding strand of the original DNA.

    The role of observable characteristics on biodiversity investigation

    The original method of comparing species is to observe their characteristics. This is quite unreliable as genetic differences between species can only be assumed using this technique, as we now know that animals exhibit specific characteristics thanks to several different genes and alleles situated. Even the environment they live in can impact these characteristics over time. The main problem is that many species have similar characteristics, so more research needs to be conducted to differentiate between them.

    Examples of these characteristics include:


    • Number and type of limbs

    • Number of petals, leaves, seeds and branches

    • Fur/fins/wings/antennae

    • Patterns on body/stem/petals/leaves

    • Colour

    • The habitat they reside in

    • Emigrational patterns

    • Eating habits

    Investigating the amino acid sequence

    Analysing the amino acid sequences for the same protein in different animals can show us how closely related they are. These differences in amino acid sequence will cause the protein to function differently, which could be vital in helping the species survive.

    Mutations can lead to the species being better adapted to its environment (survival of the fittest). Therefore, the more similar two amino acid sequences between two animals are, the more closely related they are.

    Results collected from amino acid extraction are much more useful than DNA extraction as there are 20 different amino acids compared to only four different bases, and non-coding sections of the DNA can lead to insignificant results. In addition to this, the sequence of amino acids evolves at a much slower rate than that of DNA: in closely related species, the protein will continue to function in the same way; therefore, the sequence will not change.

    Quantitative investigation used in biodiversity

    Quantitative investigation gathers and analyses numerical data, displayed in graphs and tables, and subsequently observed or put through various statistical tests to test relationships, draw hypotheses, and make predictions for larger populations.

    Hypotheses in quantitative investigation

    A hypothesis is a proposed explanation for a phenomenon or a set of observations. There are three types of hypotheses: null, one-tailed and two-tailed.

    The null hypothesis predicts that there will be no difference between specific populations. Any differences are due to experimental or sampling error.

    The one-tailed hypothesis predicts the results going in one direction, the result is either greater or lower.

    The two-tailed hypothesis: predict that there will be an impact of a variable; however, it does not specify if the effect is, for example, greater or lower.

    Let's use a hypothetical example of moss beds. The research question for this is as follows: the study aims to investigate if the moss beds in Lithuanian forests are declining or expanding over time.

    So what are the hypotheses?

    • Null hypothesis: There is no change in the area of the moss beds (meaning no expansion or decline).
    • One-tailed: Moss beds are expanding over time.
    • Two-tailed: The area of moss beds will change.

    Pearson's chi-squared test is used to deduce a significant difference between the expected values and observed values from a categorical data set.

    Types of quantitative research

    • Correlational research is the comparison of the variables that you study to discern any relationship between them.

    Biodiversity, investigating biodiversity correlation, StudySmarter

    Fig. 8. Close correlation between y and x; 2: Loose correlation between y and x; 3: No correlation between y and x.
    • Descriptive research produces an overall summary of the variables studied rather than an in-depth analysis.
    • In experimental research, hypotheses and cause-and-effect relationships between variables are tested systematically.

    • Causal-comparative research is used to see if any causal relationship exists between two variables.

    Qualitative research

    Qualitative research concerns non-numerical data, such as interviews, documents and observations. Qualitative research results are used to better understand peoples' opinions, relationships, behaviours, and psychological states.

    Advantages of quantitative research over qualitative research

    • Comparison - studies can be conducted on various samples, and then the results can be compared to test relationships between different groups.

    • Exact replication - identical experiments can be carried out thanks to the regimented nature of quantitative research, increasing the reliability of results.

    • Large samples - data can be collected from large samples in quantitative research. In contrast, collecting large samples in qualitative research is more difficult as the results are more subjective and long-winded.

    • Statistical analysis - the use of established hypothesis testing procedures and various statistical analysis formulae, we can better understand the relationship between variables.



    Biodiversity - Key takeaways

    • Biodiversity is the measure of the abundance and spread of different species, as well as the size of their gene pool and the habitats available to them.

    • Greater biodiversity is important in maintaining ecosystems worldwide and positively impacts the environment and the human population.

    • The diversity between species can be investigated through the index of diversity calculations, the study of observable characteristics, DNA sequence and amino acid sequences.

    • Quantitative research is the gathering of numerical data which is then analysed and inputted into tables and graphs to deduce if any relationship exists between variables.


    Frequently Asked Questions about Biodiversity

    What is biodiversity?

    Biodiversity is a culmination of species, genetic and ecosystem diversity to give an idea of the abundance, variance and gene pool of species in a certain area.


    What is genetic diversity?


    Genetic diversity is the size of the gene pool in a population, and the amount of different alleles within this gene pool.

    What are things you can compare to investigate genetic diversity?

    You can compare various observable characteristics, but also if you have the correct technology you can compare the DNA, RNA and amino acids of different organisms.

    How does deforestation affect biodiversity?

    Deforestation has a detrimental effect on biodiversity because it kills the habitats of various species which live in the trees, as well as killing some of the organisms in the process.

    How is biodiversity measured?

    There are many ways to measure biodiversity, such as measuring species richness, inputting data into the index of diversity formula or using quadrats and transects.

    How are human activities affecting aquatic biodiversity?

    Overfishing has a huge impact on global aquatic biodiversity and climate change resulting from human development leads to the degradation of aquatic habitats such as coral reefs.

    Why is species diversity important?

    Species diversity is important in maintaining mutualistic relationships and even competitive relationships between species in order to maintain a stable ecosystem.

    How are species diversity and genetic diversity different?

    Species diversity concerns the number and spread of different species within a community, whereas genetic diversity concerns the gene pool of a community.

    What is the difference between quantitative and qualitative investigation?

    Quantitative research concerns numerical, objective data, whereas qualitative research entails more subjective data such as opinions, behaviours and beliefs.

    What is the index of diversity?

    Index of diversity is the measure of the number of different species in a community and how they affect other species in the community.

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