The Concept of Ecosystem
An ecosystem consists of;
From: Nature of Biology page 411
- a living community,
- its physical surroundings and
- the interactions both within the community and between the community and the physical surroundings.
From: Nature of Biology page 411
Abiotic Factors of an Ecosystem
Label the diagram below with some examples and units of measuremen of abiotic factors.
Friday 12 February
Practise using the equipment for Task 2
Background information to Task 2 Abiotic Factors
The abiotic or non-living factors in an ecosystem include: temperature, turbidity, pH, dissolved oxygen, nitrate levels and phosphate levels. These non-living factors can have considerable impact on freshwater ecosystems, particularly if they impact on autotrophic organisms (also known as producers).
A summary of some abiotic factors is found below.
1. Temperature
Organisms have an upper and a lower temperature limit beyond which growth and reproduction will stop. There is an optimum temperature range within which maximum growth occurs. Soil temperature decreases as the depth of the profile increases. Temperature can also affect other abiotic factors, such as the conentration of dissolved gases that can be held within the soil body.
Temperature is measured with a thermometer.
2. Water repellent sands and soils
Non-wetting soils or soil water repellence is caused by a waxy coating on soil particles. It primarily occurs in the topsoil with low clay content. The coatings are made up of water repelling substances, primarily plant leaf waxes and their biodegradation products. See more at:
http://www.grdc.com.au/Research-and-Development/Major-Initiatives/Non-wetting-soils#sthash.r8cvsZmI.dpuf
Devise a test for measuring the relative soil water repellence by using the following equipment in the science laboratory; filter paper, filter funnel, measuring cylinder, distilled water, beakers.
3. pH
pH is the measure of how acidic or basic a solution is. The normal range of pH in a freshwater system is between 6.0 and 9.0. A change in pH can have serious effects on the life in an aquatic ecosystem. It can cause the death of fish, larvae and eggs and it may also reduce the productivity of organisms. Higher levels of carbon dioxide in the water will lower the pH of the water, making it more acidic. The ideal range for freshwater aquatic organisms is between 6.5 and 8.
pH may be measured with universal indicator and a pH chart, or electronicpH probes.
4. Organic material
Organic matter in soils is made of the remains of dead organisms, or organic wastes from organisms. Minerals contained within the organic matter are released by the decomposition of the material. Bacteria and fungi are majors decomposers of organic matter in ecosystems.
Devise a test for measuring the mass of organic matter in the soil by using the following equipment in the science laboratory; Bunsen burner, crucible, tongs, electronic balance.
5. Chlorides
Chloride in plants comes mostly from sea spray, dust and air pollution. Fertilisation and irrigation also contribute to chloride on garden soil.
Chloride is easily dissolved in water and enters the plant through soil and air. It is essential to the chemical reaction that allows the opening and closing of the plant’s stomata, tiny pores that allow gas and water to be exchanged between the plant and the air around it. Without this exchange, photosynthesis can’t occur. Sufficient chloride on garden plants may inhibit fungal infections.
To test for the presence of chlorides first leach the soil sample with hot water. Filter off the solids and collect the filtrate in a test tube. Test the filtrate using a few drops of dilute silver nitrate solution. If enough chlorides are present a white precipitate will form in the sample.
6. Presence of carbonate minerals
Describe how you will test for carbonate minerals in the soils of the ecosystem.
Task 2 Investigation – Measuring and comparing the abiotic factors of two terrestrial ecosystems
You will conduct an investigation, measuring six abiotic factors in the Bushy Hill ecosystem on the College grounds. Click on the green writing to visit the Task 2 Assessment Page.