Biodiversity, A Three-Part Concept

Source: Food and Agriculture Organization of the United Nations, 2013, Christine Gibb, CBD and FAO, "The Youth Guide to Biodiversity" 1st Edition (Chapter 1) Youth and United Nations global Alliance. Reproduced with permission.

Chapter 1. by Christine Gibb, CBD and FAO. Verbatim.

Biodiversity consists of all the many species of animals, plants, fungi, micro-organismsand other life forms and the variety that exists within each species. It also includes the diversity present in ecosystems – or explained another way – the variation we see in the environment including landscapes, the vegetation and animals present in it, and the various ways in which these components interact with each other. Biodiversity is very complex and is often explained as the variety and variability of genes,species and ecosystems.

Genes are the units of heredity found in all cells. They contain special codes or instructions that give individuals different characteristics. Let’s compare, for example, the genes coding for the necks of two different species: giraffes and humans. Even though both species have the same number of neck vertebrae (seven), the neck lengths of the two species are very different – approximately 2.4 metres for giraffes versus 13 centimetres for humans. This is because a giraffe’s genes instruct each vertebra to grow up to 25 centimetres in length, whereas a human’s instruct each vertebra to grow to less than two centimetres. Genetic diversity occurs within a species and even within a variety of a given species. For instance, in a single variety of tomato, the genes of one individual may cause it to flower earlier than others, while the genes of another individual may cause it to produce redder tomatoes than other plants. Genetic diversity makes every individual unique. So in fact no two living things in nature are exactly the same. Chapter 3 delves into genetic diversity in greater detail.

Species - In our world you can find a dazzling array of animals, plants, fungi and micro-organisms. The different kinds of these are called ‘species’. A species is a group of similar organisms (individual living creatures such as spiders, walnut trees or humans) that can breed together and produce healthy, fertile offspring. Although we may not think about it, we see various species as we go about our daily lives, such as humans, goats, trees and mosquitoes. Species diversity is the most obvious type of biodiversity. 

Our planet supports millions of species, many of which are not yet identified! At present, there are 310 129 known species of plants and 5 487 known species of mammals. There are perhaps millions of tiny organisms or micro-organisms that scientists have yet to identify. Chapter 4 explores species diversity, and answers species‑related questions such as: why are species important?

Ecosystems - In the same way that humans live in communities, so too do animals, plants and even micro-organisms. Where communities of plants and animals live together, and share their space, their land and their climate, they form an ecosystem. Ecosystems are what many people call “the environment” or “nature”. Chapter 5 provides an overview of ecosystems, and Chapters 6, 7, 8 and 9 take a closer look at biodiversity in several ecosystems. There are many kinds of ecosystems on Earth. Ecosystems can be small like puddles, or large like deserts, forests, wetlands, mountains, oceans, lakes and rivers.