Ecology- rules for living on Earth
TEACHER RESOURCES:
INTERACTIVE QUIZ: This link is useful for consolidating the concepts of ecology.
INTERACTIVE QUIZ: This link is useful for consolidating the concepts of ecosystems.
In this exercise, you will utilise an online calculator to examine your ecological footprint, compare it to the average footprint in your country and other countries, and critically examine ways to reduce it.
Video that examines the types of interactions that exist among organisms in a community, from competition between consumers for specific resources to the relationship between predators and prey.
In this Interactive Exercise, you will use a marine ecosystem to investigate the dynamic nature of ecosystems. You will explore the various regions of the bay, and then investigate some of the natural and human-imposed changes to which the bay responds.
The study of the interaction between organisms and their environment
An ecosystem is a complex system that consists of all the living organisms in a particular area, as well as the environment with which the organisms interact. The living organisms and non-living components of the ecosystem interact in such a way as to maintain balance. Ecosystems are divided into biotic (living) and abiotic (non-living) components respectively. Each component is discussed in detail below.
Biotic components are living things that shape the ecosystem. Each biotic factor needs energy to do work and for proper growth. To get this energy, organisms either need to produce their own energy using abiotic factors, or interact with other organisms by consuming them. Biotic components typically include:
Abiotic components are the non-living chemical and physical factors in the environment that affect ecosystems. Abiotic components play a crucial role in all of biology. Abiotic factors are broadly grouped into physiographic, edaphic and climactic factors and atmospheric gases.
1. Physiographic factors
Physiographic factors are those associated with the physical nature of the area. The main physiographic factors we will look at are slopes, aspect and altitude.
2. Edaphic factors
Edaphic factors are those factors related to the soil. The qualities that may characterise the soil include drainage, texture, or chemical properties such as pH. Edaphic factors affect the organisms (bacteria, plant life etc.) that define certain types of ecosystems. There are certain plant and animal types that are specific to areas of a particular soil type. The particular factors we will consider include the pH of the soil and soil structure.
pH of soil is a measure of how acid or alkaline soil is and can be measured by using the pH scale. The pH scale ranges from 0 to 14. Neutral solutions have a pH value of 7. Acid solutions have a pH value of less than 7 and alkaline solutions have a pH value greater than 7. Litmus paper or universal indicator can be used to determine whether a solution is acid or alkaline.
Figure 8.16: pH scale for soil.
Did you know that some species of Hydrangea flowers are natural pH indicators? The flowers of the Hydrangea macrophylla and Hydrangea serrata cultivars, can changes colour depending on the relative acidity of the soil in which they are planted. In an acidic soil with a pH below 7, the flowers will usually be blue. However in an alkaline soil with a pH above 7, the flowers will be more pink. Moving the plant from one soil to another results in a change in flower colour if the pH of the soil is different (see Figure 8.17).
Soil Structure: the decomposed organic matter, called humus gives topsoil its dark colour. It supplies plants with nutrients and helps the soil retain water. Soils rich in humus are fertile soils. The specific soil type is determined by the size of particles e.g sand has very large sized particles, clay has very small sized particles and loam has a mixture of particle sizes. If you roll moist soil between your fingers, clay soil feels sticky, sandy soil feels gritty and loam soil feels soapy. The water retention capacity of soils is the ability of soil to retain different amounts of water. Clay soil retains a large amount of water. Sandy soil retains very little water. Loam soil retains a moderate amount of water.
To investigate the water retaining properties of three soil types.
loam, sand and clay soil samples
filter funnels and filter paper
measuring cylinders
water
stop watches
Write down your results in a table:
Which sample of water retained the most water?
Which sample of water retained the least water?
Explain your observations. Try to describe three properties that result in the different water-retaining capacities of different soil types. Use your experimental results to recommend which soil would you use for your pot plants.
Investigation: to investigate the water retaining properties of three soil types
This activity may be counted towards one of the investigations in the term project. Learners should bring soil samples from their chosen ecosystem to test in addition to the sand, loam and clay samples provided.
Results
This is easily shown as a table. Learners can copy this table before they start the investigation:
Table showing drainage and water retention of three different soil types:
Soil type | Volume water poured into soil sample (ml) | Volume of water that ran into cylinder (ml) | Volume of water retained by soil (ml) | Time for complete drainage of water (sec) |
Sand | ||||
Loam | ||||
Clay |
Bar Graph comparing the water retention capacities of of three soil types:
Learners should draw a bar graph to show the amount of water retained by the three types of soil. They may also choose to draw a second bar graph showing how quickly each soil-type drained. One would expect clay to retain the most water, and sand to retain the least.
Observations
Questions
Which sample of water retained the most water?
Which sample of water retained the least water?
Answers
Clay retained the most water.
Sand retained the least water.
Conclusions
Three reasons for the difference in the water retention capacities of the soil types include:
Clay soil has small particles and tiny air spaces, so it easily becomes waterlogged (muddy) and holds very little air for plant growth.
Loam is the best soil for plant growth because it retains a fair amount of water but doesn't become water logged.
ALTERNATIVE METHOD:
Place 30 g of each soil type in a filter funnel which is lined with filter paper.
Place each funnel on top of a 100 ml measuring cylinder.
Pour 50 ml of water into each funnel (slowly until all the water has been added to the soil).
Leave to stand for 2 minutes - record how much water is in the measuring cylinder.
After a further 2 minutes record any change to the amount of water in the cylinder.
After a further 2 minutes record any changes to the amount of water in the cylinder.
Record your results in a table. Add an extra column in which you calculate the amount of water retained.
Variable | How controlled |
Amount of water Amount of soil Time of experiment | 50ml with measuring cylinder 30g with electronic scale 2 minute intervals with watch/clock |
3. Climatic factors
Sunlight: is essential for the process of photosynthesis. Producers, such as plants, rely directly on the sun. Heterotrophs, such as animals, use light from the sun indirectly by consuming plants or other heterotrophs. All organisms receive the energy required for survival through the break down of sugars and other molecular components that are produced by the autotrophs. These sugars are then broken to release the energy stored in them, by the process of cellular respiration.
Temperature: varies greatly across different parts of the Earth and throughout the year. Temperature affects the rate of evaporation and transpiration and causes seasonal changes in weather. Seasonal variation in vegetation also occurs as the germination of seeds requires warm temperatures. Plants and animals have special adaptations that make them suited to the temperature of their specific environment. Temperature affects the rate at which photosynthesis, cellular respiration and decomposition take place. As you learnt in the earlier section on enzymes, this is linked to the optimal temperature profile for enzymes. The rate of reaction increases with increasing temperature and decreases at lower temperatures.
Water: is one of the most important factors in the ecosystem. It is the main component of living cells and is essential for all living organisms. About of the human body and of the plant body consists of water. Water is not evenly distributed over the Earth. It is abundant in aquatic ecosystems and least abundant in deserts. Plants are adapted to the available amount of water in the following ways:
Mesophytes are plants that need an average, regular supply of water.
4. Air/gases
Wind: speeds up evaporation and assists in pollination of plants and the dispersal of their seeds.
Air: is composed of nitrogen, oxygen, carbon dioxide and water vapour. Look ahead to the section on nutrient cycles to read more detail. Oxygen is used in cellular respiration and combustion and is returned to the environment by the process of photosynthesis. Carbon dioxide is a product of cellular respiration and decayed organic matter. It is removed from the atmosphere by plants during the process of photosynthesis. Nitrogen is needed by all living organisms for the synthesis of proteins. The amount of water vapour found in the air remains constant on average, however, it can vary greatly from one place to another. Some parts of the earth are prone to high humidity levels, while other locations have very dry air. Much of what we consider weather is caused by water vapour. The clouds in the sky are largely made up of it, and it is the condensation of this vapour into droplets that creates rain and snow.
Endothermic animals are able to regulate their body temperature so they are not affected by extreme temperatures, and are able to live in habitats over a wide range of temperatures. In cold regions, animals have developed a layer of insulating fat, or hibernate during the colder months. In very hot regions, animals have adapted by becoming nocturnal in their habitats. Ectothermic animals are unable to regulate their body temperature, and therefore the change in environmental temperature will affect their distribution and activities.
In Northern Hemisphere countries where the day length is substantially longer in the summer, the rate of growth of plants is very high.
Identify abiotic, biotic and cultural characteristics of a natural environment near you.
Select an area that is undeveloped (e.g. no buildings, no pavement, no bulldozing, no spraying of pesticides, no farming, no grazing, etc.). Your area must be at least the size of a soccer field. Make a map of your province and show, approximately, where your area is located.
Identify at least 10 abiotic features of your area. Consider factors such as:
Identify at least 15 biotic features of the area. Consider things such as:
Identify at least 3 cultural components. Look for evidence of human influence. Consider things such as:
Examine the data you collected when making your profile of your area. Use your collected data to answer the following questions. Discuss your answers afterwards in your group/with your partner.
Project: Biotic, abiotic and cultural characteristics of a natural environment
NOTES TO TEACHERS:
It is suggested that this is done as group work, not individually.
It may be very valuable to just examine an area near the school as a class group and answer the questions verbally in a class discussion.
It is not necessary to asses this project formally if done as a class exercise.
GUIDELINES:
The map can be hand drawn and can be relatively simple. Should include an arrow to indicate North and should preferably have a scale or indication of size. It is probably better to have a map of the local AREA, as part of the province.
ABIOTIC factors: Should include Edaphic factors, Physiographic factors and Physical factors.
BIOTIC factors: Any animals and plants that are found in the area. They may not be able to find FIFTEEN. This should not be penalised – teachers just need evidence that they have tried to find different animals and plants. It may be useful to ask them to take photos of the organisms they find. This helps with later identification.
CULTURAL components: Learner-dependent answers. Encourage them to find DIFFERENT cultural components, not just litter, for example.
ANALYSIS section: it is clear enough what is expected. Learners may not be able to give detailed answers here.
Aim and background information
You are required to choose one ecosystem within a local biome for special study. The study will be conducted over two terms and will involve a number of investigations. You may work in groups. Each group will have to plan, collect, record, present, analyse and evaluate the data.
1. Soil
The type of soil found in your ecosystem will have an influence on the types of plant that will grow in that ecosystem. It is important to identify the types of soil found in your ecosystem by doing the following soil tests.
1.1 How to identify soil texture
How to interpret your observations:
1.2 How to measure pH
You will need the following materials:
How to interpret litmus paper observations:
1.3 Measure the water-holding capacity of your soil sample/samples
You will need the following apparatus:
2. Temperature
You will need the following apparatus:
Date | Time | Daily Temperature |
3. Light
You will need the following apparatus:
Date | Time Flower Opens | Time Flower Closes |
4. Physiographic Factors
You will need:
5. Studying biotic factors
If the ecosystem you are studying covers a large area, it may be difficult to observe all the living organisms. If this is the case, you can get some idea of the plant and animal diversity in the ecosystem you are studying by choosing a smaller sample area to study.
You will need:
6. The effect of humans on the ecosystem
Determine if humans have had any effect on the ecosystem. These effects may be positive, negative, or a combination of both.
Write a scientific report on the ecosystem you have studied.
Your report should include the following:
Project: To study a terrestrial ecosystem
NOTES TO TEACHERS:
In this investigation learners are to choose a terrestrial ecosystem either at school or close to where they live.
Educators to note that this investigation can be given to learners at the beginning of a term and then allow the learners to hand in their completed written report towards the end of the term.
Alternatively if this investigation is done on the school property various deadline dates can be set for each section to be investigated.
Learners to comment on their own findings and their work to be marked accordingly.
INSTRUCTIONS:
Soil texture: Note that some soils are so sandy, that they cannot even be rolled into a sausage – the ball breaks if one even tries to roll or squeeze it into a sausage shape.
Measuring pH: It is acceptable to just dip the litmus or universal indicator into the water once it has settled – one does not have to remove water with a spoon. It is vital that the jar must be clean before the soil is added, as food remains etc inside the jar will affect the pH reading. It may yield surprising results to check the soil pH of different parts of the same general area – it is not necessarily the same across the entire area.
Water holding capacity: The basic procedure is the same as that described in the previous investigation on the water-holding capacity of soil. Learners should use three dry soil samples – the same amount of soil and water is used in each case. If using 100 ml of water, the percentage water retained and drained can be calculated easily for comparison.
Temperature: Ensure that the thermometers are placed in the same place at different times, not sometimes in the sun and at other times elsewhere in the shade. This is a better indication of the range of temperatures in the area at different times.
Photoperiod: The Time flowers open / close goes on the vertical axis, and Day 1 / 2 / 3 goes onto the horizontal axis. Two separate graph lines will show Opening and Closing times – include a key. It is not strictly necessary to graph this – if they just record sunrise / sunset times, valid conclusions can be drawn.
Slope: This should be noted in terms of direction, e.g. the area slopes down towards the east, etc.
Grid marked out: This can be done in groups over different parts of the area. They are likely to find only small animals like insects. The groups can combine to draw a composite map of the area as a class.
Report: The class as a whole can do a single report or separate groups can do their reports on their own if the teacher requires this.