Introduction to Environmental Biology
Senior 2 · Biology
Introduction to Environmental Biology
Lesson 1 of 4
16 min
Let's begin
Rwanda protects its three biggest national parks for very different reasons. Nyungwe is a cool, wet mountain rainforest; Akagera is a hot, dry savanna of grass, acacia trees, lakes and swamps; and the Volcanoes National Park is bamboo and misty forest on the slopes of the Virunga volcanoes. The animals and plants in each are different because the conditions are different.
Ecology is the study of how living things interact with each other and with their non-living surroundings. To protect a park, grow food without harming the land, or manage the fish of Lake Kivu, you need the words in this lesson.
Ecologists study life at several levels. Each level contains the one before it.
| Level | Meaning | Example |
|---|---|---|
| Organism | one individual living thing | one chimpanzee in Nyungwe |
| Population | all the members of one species living in one area at the same time | all the chimpanzees in Nyungwe |
| Community | all the populations of different species living and interacting in one area | the chimpanzees, monkeys, birds, trees, insects and fungi of Nyungwe |
| Ecosystem | a community together with its non-living surroundings (soil, water, air, light, temperature), all interacting | Nyungwe forest; Lake Kivu |
| Biome | a large region of the world with a similar climate and similar kinds of vegetation, made of many ecosystems | tropical rainforest; savanna; desert |
| Biosphere | all the parts of Earth where life exists: land, water and the lower atmosphere | the whole living Earth |
A habitat is the place where an organism lives and finds its food, water and shelter. It is the organism's "address". The habitat of a hippopotamus in Akagera is the lakes and the grassland beside them.
A niche (say "neesh") is the role of a species in its ecosystem: what it eats, when and where it feeds, what eats it, and how it changes its surroundings. It is the organism's "job". The niche of the hippo is to rest in the water by day, graze grass on land at night, and fertilise the lake with its dung, which feeds the algae and fish.
Question: Two birds share the same patch of wetland in Rugezi marsh. Species A wades and eats frogs by day; species B eats seeds from grass heads. Do they share a habitat, a niche, both or neither?
Solution: They live in the same place, so they share a habitat. They eat different food, so their niches are different, and they do not compete for food. Two species cannot share exactly the same niche for long: the better competitor would push the other out. This is why species living together usually differ in food, feeding time or feeding place.
Question: Name the level described: (a) all the isambaza in Lake Kivu; (b) all the fish, plankton, water plants and bacteria in Lake Kivu; (c) Lake Kivu with its water, dissolved gases, sunlight and all its organisms.
Solution: (a) one species, so a population; (b) many species, living parts only, so a community; (c) living and non-living parts together, so an ecosystem.
Tip
Memory hook: habitat = address, niche = job.
Exam technique: a population is ONE species; a community is MANY species; an ecosystem adds the NON-LIVING surroundings. Most marks are lost by mixing these three up.
Arrange these levels from the smallest to the largest: community, organism, biosphere, population, ecosystem, biome.
Solution: organism → population → community → ecosystem → biome → biosphere.
Explain the difference between a population and a community, using Akagera as your example.
Solution: A population is all the members of one species, such as all the zebras in Akagera. A community is all the populations of different species living there together: the zebras, lions, impalas, grasses, acacia trees, birds and so on.
Describe the niche of an earthworm in a farmer's field.
Solution: It lives in the soil and feeds on dead leaves and humus. It is eaten by birds, moles and some snakes. Its burrows let air and water into the soil, and its droppings return minerals, so it improves soil fertility.
Which level includes the air and rainfall of Nyungwe: the community or the ecosystem? Explain.
Solution: The ecosystem. A community contains only the living things, and an ecosystem includes the non-living surroundings as well.
Summary
Sources and credits
The definitions of the ecological levels, habitat and niche, the Rwandan examples, the worked examples and the practice questions are written by Ganzaa.
