BIOLOGY

Ecosystems

Ecosystems

Consider a moose in the woods, moving through the spaces between trees. The moose feeds on shrubs, trees, and aquatic plants around a small pond. A beaver dam has formed the small pond. The animals, plants, and pond water are all part of a complex system of living and non-living things.

This complex system, made up ofgroups of living organisms andtheir non-living physical andchemical environment, is calledan ecosystem. The componentsof an ecosystem are interrelated,which means that changes in onecomponent can affect othercomponents.

ECOSYSTEM• all the living organisms in an area and their

non-living environment• interrelated – changes in one affects the

others

For example, when a forest is cut down, the trees that were once home to insects, birds, and squirrels are no longer there. The animals will need to find a newplace to live. Ecology is thestudy of how organisms interact with each other as well as with their environment.

ECOLOGY• the study of how organisms interact with each

other and their environment

PRACTICE1. Which of the following are considered to be an ecosystem? Explain your reasoning.(a) Pond yes(b) Schoolyard no(c) all the cats in your neighbourhood no(d) Tree yes(e) vase of cut flowers no

Living & Non-Living Factors

Living organisms in an ecosystem are bioticfactors. Biotic factors include organisms, their waste, their homes, and their remains. Insects, fungi, beavers, moose droppings, and shrubs are all biotic factors.BIOTIC FACTORS• all living things and their

remains• insects, feces, nests, milk, ...

The non-living features of an ecosystem are abiotic factors. This not only includes physical things, such as rocks, air, and waterbut also things that are measured such as air temperature, hours of daylight, and saltwater concentrations.ABIOTIC FACTORS• the non-living chemical and

physical characteristics of an ecosystem

• temperature, wind, water, minerals, ...

NOTE!It is the interactions of the biotic and abiotic elements that help keep ecosystems healthy and sustainable.

PRACTICE2. Classify each of the following as either a biotic or abiotic feature:(a) Temperature abiotic(b) Wind abiotic(c) Sunlight abiotic(d) dead leaves biotic(e) Spiders biotic(f) Sand abiotic(g) Milk biotic(h) Hair biotic(i) Ice abiotic(j) Plastic abiotic

PRACTICE3. “Human activities change only the biotic features of an ecosystem.” Is this statement true or false? Explain why or why not.false – we change both our abiotic environment (buildings, mining, …) and biotic environment (hunting, fishing, …) – both of which affect theecosystem

PRACTICE4. People living in northern environments are more likely to suffer seasonal affective disorder (SAD), which is a form of depression associated with low winter light levels. How is SAD an example of the relationship between the biotic and abiotic parts of an ecosystem?SAD is a form of depression (a biotic factor) associated with low light levels (an abiotic factor)

Populations & Communities

In most ecosystems, there are many different species. A species is a group of similar organisms in an ecosystem. Members of the same species that live in the same ecosystem are a population. All the populations of different organisms in an area form a community.NOTE!Biodiversity is a term used to express the number of different types of organisms in an area. Typically, the more organisms there are the healthier the environment.

For example, the diagram below shows how ecosystems are composed of individual organisms, populations, communities, and the physical surroundings in which communities of organisms live.

SPECIES• group of similar organismsPOPULATION• members of the same species that live in the same

ecosystemCOMMUNITY• all living organisms, from all populations, that live in the

same ecosystemBIODIVERSITY• number of different types of organisms in area

PRACTICE5. Does a population include abiotic features, biotic features, or both?Explain your choice.biotic (living) features only – species that live in the same ecosystem

PRACTICE6. Would you consider a large city to be a population or a community? Explain your choice.community – all living organisms that live in the same ecosystem (i.e. humans, cats, dogs, rats, ...)

Differences in EcosystemsEcosystems are highly variable.They can differ dramatically insize and in their biotic and abioticfeatures. We generally think ofan ecosystem as a fairly largearea, such as a forest or a lake.On a much smaller scale, thecommunity of bacteria and fungiliving in a rotting log is anecosystem. In this way, largeecosystems may include manymuch smaller ecosystems.

Whatever the size, everyecosystem is characterized bya distinctive set of features.For example, you coulddescribe a beaver pondecosystem by its organisms orby its physical characteristics,such as the temperaturerange, or water depth.

Check Your Learning

1. What abiotic factors may affect the growth of an oak tree in an Ontario forest?

water, sunlight, temperature, pollution, ... (i.e. non-living factors)

2. A stream is an aquatic ecosystem, but it can also be part of a forest ecosystem at the same time. Explain how this is possible.it contains all the living organisms in the stream (fish, frogs, ...) and their non-living environment (rocks, water, ...) but the stream itself ispart of a much larger forest ecosystem (deer, trees, mountains, ...)

Our planet has been referred to as Spaceship Earth. Explain how this might be an effective way to describe our planet.the spaceship (Earth) is flying through space – it has numerous inhabitants/passengers and has all the features necessary to support life