The Diversity of Life on Earth

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Life on our planet displays a stunning array of diversity. This is termed biodiversity. This article will discuss this subject, exploring the variety of organisms and why this diversity is important for the continuation of life on Earth.

What is Biodiversity?

Biodiversity – An overview

Life is a complex web, with each species interacting with each other, from the simplest bacteria and viruses to humans and other complex multicellular organisms. Each organism has evolved to become uniquely adapted to its environment.

The term biodiversity is applied to life at every level, from its genetic makeup to the entire ecosystem in which individuals reside. Biodiversity encompasses evolutionary, ecological, behavioral, and cultural aspects. The study of biodiversity is interdisciplinary, having grown exponentially since the late 20th century when concerns about biodiversity and habitat destruction started to move into mainstream discourse.

Human culture and diversity can also be regarded as part of biodiversity because of the effects human society has on nature. We both affect and are affected by the species we share the planet with as well as the sea and landscapes around us and those in which we live.

We have altered the world in unique and sometimes damaging manners throughout human history, changing the makeup of species in entire ecosystems. In turn, lifeforms such as animals and plants have adapted to our influence.

The array of living species and importance of biodiversity

1.2 million species have been discovered by scientists. Insects constitute by far the largest proportion of all life on Earth identified. For every person on Earth, there are about 1.4 billion insects (about 10 quintillions in total.) Much mystery surrounds the species that have not been discovered.

Biodiversity is important because, aside from the interconnectedness of living species maintaining healthy ecosystems, human society takes advantage of them for numerous purposes. We use different species for food, medicine, research, nutritional supplements, clothing, and so forth.


Image Credit: VectorMine/

The kingdoms of life

It is generally agreed that there are five main groups of organisms on Earth, though there is some debate about this. The five main accepted kingdoms are:


All members of this major branch of life are eukaryotic, multicellular, and heterotrophic, having to consume other organisms to live.

Animals exist in nearly every ecosystem on Earth, from the highest mountain peaks to the abyssal depths of the ocean. The kingdom also contains the most species, due to the inclusion of insects (which represent over 90% of all life so far discovered.)

Animals are generally divided into two main groups: vertebrates and invertebrates. Some groups of animals include:

  • Mammalia
  • Birds
  • Reptilia
  • Amphibia
  • Agnatha (jaw-less animals that resemble fish, such as lampreys)
  • Osteichthyes (true fish)
  • Chondrichthyes (cartilaginous fish)
  • Insects

With some exceptions, animals are motile, and many have adapted to thrive in their own ecological niches. Some are more specialist than others, and many animals are used by humans for food and materials.


The kingdom Plantae contains all the species of plant. Multicellular eukaryotes are also found in a huge array of ecosystems. Able to make their own food via photosynthesis, they also differ from animals by having a cell wall that surrounds their cell membrane. Plants exhibit an array of features that make them adapted to their environments, like flowering structures, complex roots, shoots, and leaves.

The plant kingdom is divided into five subgroups. These are:

  • Thallophyta
  • Bryophyta
  • Pteridophyta
  • Gymnosperms
  • Angiosperms

Plants play a vital role in maintaining life on Earth by producing oxygen. They are used by humans for food, construction, medicine, and a plethora of other commercially important applications.


Fungi are a distinct kingdom of eukaryotic organisms that include yeasts, molds, and mushrooms. A defining feature of fungi is chitin-containing cell walls. Fungi also share characteristics of animals in that they are heterotrophic, having to digest external nutrients to live. They are the main decomposers within environments, and therefore play a key role in several nutrient cycles.

Fungi are ubiquitous to many ecosystems and have long been used in food production. Some are parasitic in nature, and many produce toxins that make them harmful to human health. Fungal species such as penicillium molds have been used to provide antibiotics to fight pathogens.

Fungi can produce sexually, asexually, via homothallism, genetic exchange via parasexual mechanisms, and by spores. In contrast to animals and plants, the fossil record for funguses is patchy: this is due to various factors including the lack of preservation of fruiting bodies and the microscopic nature of many fungal structures.

In 2019, scientists discovered a fossilized fungus, Ourasphaira giraldae, which may have existed on land around a billion years ago, making terrestrial fungi much older than their plant counterparts.


Protista are single-celled eukaryotic organisms. This kingdom includes amoebae, paramecium, euglena, and Trypanosoma. Many species in this kingdom are parasitic, and many possess animal-like behavior such as motility and predation. They also lack a cell wall, which distinguishes them from algae. They feed via heterotrophy. More than 50,000 species of protozoa have so far been identified.


Species belonging to the kingdom Monera are prokaryotic (single-celled) organisms that lack a true nuclear membrane within their cells. Bacteria and blue-green algae are members of this kingdom.

Many are pathogenic in nature, whilst some contribute to important processes such as the nitrogen cycle. Various species are also symbiotic and make possible several biological processes (such as gut bacteria in humans and mammals.) Several species in this kingdom have vital commercial applications.

Approximately 30,000 species of bacteria are known, and they make up the majority of biomass on Earth. There are estimated to be as many as 1 trillion species of microbes, which demonstrates how little we know about the true diversity of life on Earth.

Archaea, the oldest form of life on Earth, is now regarded to be a separate kingdom, and there is debate as to whether viruses are technically alive.

Biodiversity: A crucial element of life on Earth

The fact remains that human influence has had a hugely detrimental effect on the environment. Each day, more species become endangered or extinct. Several species that are yet to be discovered, that may provide us with industrially important products, may already be endangered. Several may already be extinct without us knowing about their fate. Therefore, protecting ecosystems and their biodiversity is of paramount concern to scientists and governments.


Further Reading

Last Updated: Nov 12, 2021

Reginald Davey

Written by

Reginald Davey

Reg Davey is a freelance copywriter and editor based in Nottingham in the United Kingdom. Writing for AZoNetwork represents the coming together of various interests and fields he has been interested and involved in over the years, including Microbiology, Biomedical Sciences, and Environmental Science.


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