Living World

Living World Definition

First, let's explore the living world definition.

We share this planet with almost nine million other living species. These species make up the living world.

But when is something considered living?

Humans have been struggling with that question for thousands of years. Currently, something is considered alive if it meets the following seven criteria:

• Capable of ingesting nutrition

• Capable of growing

• Breathes

• Has senses and reacts to stimuli

• Capable of some kind of movement

• Capable of reproduction

• Excretes waste

Using these criteria, we can see that rocks are not alive, but coral, elephants, hawks, pine trees, phytoplankton, and alpacas are all considered living.

Living World Geography

Geography is the study of place. Geographers divide geography into two broad categories: human geography and physical geography. Human geography is concerned with the political borders and social systems developed by humans, whereas physical geography is concerned with natural landscapes and processes.

Biogeography is a subset of physical geography. Biogeography is the study of the geographic distribution of living organisms. What migrations, adaptations, environmental pressures, and evolutionary processes affect where plants and animals come to live? What sort of plants and animals would you find in a desert? Why do lions live in sub-Saharan Africa, but not in the United Kingdom? Biogeographers seek to answer these questions.

Fig. 1 - You won't find a lion in the UK unless it has escaped from the zoo!

Biogeography is related to several scientific fields outside of geography, such as ecology (the study of organism interactions) and biology (the study of life). These fields are collectively referred to as the life sciences.

In order to make sense of the living world, the life sciences have developed categories to make things more comprehensible. You may have seen, for example, a Latin name assigned to an animal. This is an animal's universal scientific name, which is used to identify the animal across cultures and languages. This Latin name uses a binomial nomenclature system; the first word identifies the genus, or group, that an animal belongs to, while the second word is a description of the species. 'Lion' translates to 'asad' in Arabic, 'simba' in Swahili, and 'aslan' in Azerbaijani; but in any language, scientists can quickly and easily identify lions as 'Panthera leo.'

Living World Ecosystems

Geographers have attempted to categorise and label different types of living environments to explain why certain animals live where they do.

One of the smallest biogeographical categories is a habitat. A habitat usually describes just one species and its potential living conditions within an environment. For example, a garden habitat is suitable for a hare or hedgehog.

An ecosystem describes a living community. It is a category that takes into account all of the living organisms in an area and their interactions with each other and their physical environment. The moorlands throughout the United Kingdom each have a grassland ecosystem. There's a lot that goes into an ecosystem: the grasses taking nourishment from the soil and sun; animals eating the grasses; animals eating other animals; decomposition and scavenging.

Ecosystems are important because all life depends on them, even us humans. We don't live in a vacuum! The food we eat, the resources we use, and the air we breath are all components of various ecosystems. For more information, be sure to check out our explanation on Ecosystems!

The world can be divided into groups of different major ecosystems. A world ecosystem or global ecosystem is the largest biogeographical unit. World ecosystems are called biomes.

Biomes include the tropical rainforest biome; the temperate rainforest biome; the temperate grassland biome; the savanna grassland biome; the desert biome; the polar biome; and the coral reef biome.

Fig. 2 - The temperate grassland biome includes all of the different temperate grasslands in the world

Not all geographers agree on the number of biomes. Some divide the world into only five broad biomes, while others may divide the world into 30 or more different biomes! You can learn more by reading our explanation on Biomes.

Some biogeographers use different sets of units for categorising different parts of the world. For example, instead of using global ecosystems/biomes as the biggest biogeographical unit, some biogeographers use biogeographic realms. The scale goes something like this:

• Ecosystem

• Ecoregion: A geographic region with multiple similar ecosystems.

• Bioregion: A group of ecoregions, whose borders are defined by major topographical boundaries.

• Biogeographic realm/Ecozone: the division of broad types of bioregions, based mainly on evolutionary history and topographic boundaries.

Although biomes and biogeographic realms are similar, biogeographic realms take more physical geography into account, rather than plants' and animals' habitats, communities, and living conditions.

Components of the Living World

The two broad types of components in any ecosystem are abiotic and biotic. Abiotic components are non-living. Dirt, solar energy, rocky outcrops, and weather patterns are all abiotic components.

But here, we're concerned with the biotic, or living, components. Biotic components are anything that is alive. Traditionally, living organisms are grouped into five different communities called kingdoms. Take a look at the table below.

Living components interact with each other. For example, some animals eat plants, while some animals eat other animals. Additionally, animal or plant remains may be decomposed by fungi or bacteria.

Living World of Animals

The most relatable element of an ecosystem is the animals. In fact, we humans are animals in ecosystems!

Within an ecosystem, plants are usually considered producers, which means that they can serve as an initial source of energy. Animals are considered consumers: they gain energy from producers and from each other.

Because most animals are mobile consumers, animals help shape landscapes. When animals consume fruit, they can spread the seeds to other locations. When animals eat grasses, trees, and shrubs, they can increase or decrease various types of plant life. When animals prey on each other, the 'leftovers' provide meals for scavengers and fungi, and the decomposition helps fill the soil with nutrients.

Some ecosystems have keystone species, an animal so important to an ecosystem that the entire ecosystem revolves around it. On the Great Plains of the United States, a temperate grassland ecosystem, bison were a keystone species. Every other animal living on the Great Plains was in some way, directly or indirectly, affected by bison activity. Bison rolling, grazing, and foraging spread seeds across the grasslands and carved out habitats for ground-dwelling birds. Bison were the primary food source for Great Plains predators, like wolves and even humans, and bison faeces acted as fertilizer for the grasses.

Fig. 3 - Bison were a keystone species of the American Great Plains

When keystone species are removed from an ecosystem, that ecosystem becomes degraded. In the late nineteenth and early twentieth centuries, the bison were deliberately overhunted to make way for cattle grazing; railroad expansion; and to undermine the nomadic hunter-gatherer lifestyles of the native tribes on the Great Plains. When bison were all but eliminated, the Great Plains lost a major source of nutrients in the form of fertilizer and meat. The living world can be a very fragile system!