Humans and the environment
Introduction
Ecology is the study of how organisms interact with each other and their physical environment. The community of organisms and their environment make up an ecosystem. This chapter looks at the interaction between human beings and their environment.
Ecosystem
The community of the ecosystem includes all its living organisms. In ecosystems, each organism is present only in certain numbers. The number of organisms living in the ecosystem is called a population. Planet Earth, leaves, the ocean or a beach pebble are all different parts of an ecosystem. The part of the Earth where living organisms can be found is called the biosphere. Earth's biosphere is divided into biogeographical regions. Each region can be characterised by its own unique flora and fauna. Areas with similar climatic conditions are called biomes. More specific areas of biomes are called habitats.
Food chains
All living things need energy. Organisms that can make their own food are called autotrophs or producers. Organisms that use other organisms as a food source are called heterotrophs or consumers. Autotrophic organisms, like plants, are essential for all ecosystems because they produce oxygen and they also make food for other organisms by turning inorganic compounds into organic ones.
The nutritional sequence of the ecosystem is called the food chain. 'Nutritional sequence' is a scientific term describing who eats whom and/or what. All organisms are connected to each other, playing the role of links in a chain. The links of the food chain are called the trophic levels. See image 1.
All living organisms of ecosystems are either prey or predator, or both. Most prey are consumed by more than one predator, and most predators have more than one prey. Their relationships are also influenced by other environmental factors. Biodiversity is a major contributor to the stability of ecosystems. Biodiversity is the number and variety of organisms within one region.
Each ecosystem usually has a few different communities of organisms that interact with each other. These interactions make up a food web. The food web of an ecosystem consists of a few different food chains. Organisms that consume plants for food are called herbivores. Organisms that consume other organisms for food are called carnivores. Organisms that can eat both are called omnivores. Decomposer, or detrital, consumers are organisms that consume dead plant or animal matter and turn it into smaller particles. Bacteria and fungi are decomposers.
See animation 1.
At each level of the food chain energy is lost. That is why the ecological pyramid looks like a pyramid, wide at the base and narrow at the top.
A human's place in the ecological pyramid
As the human population increases, the demands to produce food also increase, resulting in a decrease of natural habitats. In ecological food chains, humans play the role of consumers. Most humans are omnivores, which mean they consume both animals and plants.
In earlier periods, humans were living just like other animals in the ecosystem. They gathered food and other basic needs from nature. Their impact on the ecosystem was not felt. Ancient humans lived in perfect harmony with their environment. When humans learnt how to use fire and make tools, their influence on their ecosystems became more and more noticeable.
The most important cause of imbalance in the ecosystem is the increase in human population. Population is an important resource for development, yet it is a major source of environment degradation. When agriculture became a common practice, humans started replacing the natural ecosystem with the artificially-cultivated ones called crops.
Crops affect the natural recycling of nutrients. The soil becomes toxic. Without the addition of chemical fertilisers, the desired amounts of crops cannot be produced. The removal of original flora, and its replacement by cultivated crop, reduces the biological diversity and simplifies the natural ecosystem. As a result, it becomes vulnerable to pests and disease-causing microorganisms.
Modern humans came to be at the top of the ecological pyramid due to an increase in their population. As the human population keeps increasing, the top of the ecological pyramid is becoming broader. The base of the pyramid, on the other hand, is not increasing in keeping with its top. When consumers outnumber producers, the ecological pyramid becomes unstable. See image 2.
Conservation
Conservation is management of the human use of the biosphere. Conservation involves planned action or inaction to preserve or protect living and non-living resources. Long- or short-term conservation actions are often required to maintain the natural biodiversity of ecosystems which are out of balance.
Every one of us is part of this world, so what we do or do not do has an impact on the world around us. Small things that we do today might have a big impact in the future. See image 3.
