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Transcript
FS O PR O E G PA D EC TE 3 U N C O R R Matter and energy in ecosystems The biosphere is made up of all the living things on the Earth. It depends on the hydrosphere (the Earth’s waters), atmosphere (the Earth’s air) and lithosphere (the Earth’s crust and upper mantle). Within it are regions called ecosystems, where living things strongly interact and are interdependent. Ecosystems have a fine balance between organisms and their environments. Human activities can greatly alter the biosphere, lithosphere, atmosphere and hydrosphere, and overmatter 03_CRA_IS9_77563_TXT_LAY.indd 82 28/08/13 2:34 PM Components of ecosystems 3.1 FS Ecosystems are not just made up of the plants and animals that live there, but also all the microorganisms too small to see and all the non-living factors that make the conditions of that environment. It is usually these abiotic factors that determine which organisms are able to live in that environment. All the different individuals and different species within an ecosystem interact with each other as well as with their environment. These interactions can cause ecosystems to change. O Students: E PR O »» recall that ecosystems consist of interdependent biotic communities and abiotic components of their environment »» outline how matter such as nitrogen, carbon and oxygen is cycled through ecosystems »» describe how energy flows through ecosystems via food webs PA G Changing populations 3.2 Students: EC TE D Ecosystems are not static. The conditions are continually changing. Some changes are regular, like night and day and the seasons, and some are extreme and unpredictable, like bushfires and droughts. Other changes are caused by human intervention. Any change to the conditions of an ecosystem will impact on the communities that live there. The study of population in an ecosystem is called population dynamics. U N C O R R »» analyse how changes in biotic and abiotic components of an ecosystem affect populations of organisms »» evaluate some examples of strategies used to balance human activities and needs in ecosystems Managing sustainable ecosystems 3.3 Human impact on ecosystems is necessary for us to obtain the resources we need to maintain our standard of living. However, these impacts can be minimised where possible, and managed to ensure ecosystems survive and flourish. Traditional land-management practises are being reintroduced, and new modern practices are being created to conserve and protect ecosystems. Students: »» research how Aboriginal and Torres Strait Islanders use their knowledge to conserve and manage their environment »» evaluate some examples of strategies used to balance human activities and needs in ecosystems with conserving, protecting and maintaining the quality and sustainability of the environment 03_CRA_IS9_77563_TXT_LAY.indd 83 83 28/08/13 2:34 PM An ecosystem is a community of organisms (living things) and the environment (surroundings). Rainforests, grasslands, freshwater lakes and streams are all examples of ecosystems. Ecosystems have biotic (living) parts – the organisms themselves and the relationships between them, and abiotic (non-living) components – conditions and factors of the habitat. Groups of organisms, often of many different species, live together in communities. They share the same environment because they all find food, shelter and other requirements there. Matter and energy are transferred as a result of the different relationships. PR O O FS 3.1 Components of ecosystems Cycles of matter E Each element takes part in natural cycles, in which it moves through the biosphere. The cycling of matter from the atmosphere or the Earth’s crust and back again is called a biogeochemical cycle (bio means living; geo means earth). These biogeochemical cycles break and make chemical bonds, shuffling the elements around without creating new atoms or destroying old ones. Cycles of matter are examples of how living and non-living things interact. The nitrogen cycle and the carbon–oxygen cycle are two important examples. R R EC TE D PA G All substances are made of matter. We often use the term ‘organic’ to describe the types of substances that make up the biosphere. Organic material usually contains the element carbon. Carbon dioxide is an exception. While this molecule clearly contains carbon, it is so small (only 3 atoms) that it does not behave chemically like other organic molecules, and is therefore considered to be inorganic. In natural ecosystems, matter is neither created nor destroyed. The amount of each chemical element on Earth doesn’t increase or decrease, but remains the same overall. U N C O Activity 3.1.1: Dynamic ecosystems Ecosystems are constantly changing. Things enter the ecosystem, interact within it, and move out again in a way that maintains a dynamic balance. 1 Working in a small group, identify some of the common resources all living things require in an ecosystem. Use Figure 3.1 as a starting point. 2 Categorise the items in your list as either biotic (living) or abiotic (non-living) resources. 3 Examine Figure 3.2. Identify as many processes as you can that naturally occur within ecosystems. Make a list of inputs these processes require. Are these items the same as the resources you listed in step 1? Why or why not? 4 Redraw Figure 3.2 using your examples of inputs and processes, then determine what outputs would be produced by the processes you are discussing to complete your flow chart. 84 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 84 28/08/13 2:34 PM Ecosystems Interactions between organisms: predation, symbiosis, competition, etc. PR O Temperature, soil, composition, light intensity, wind speed, etc. Figure 3.1 Components of ecosystems. Ecosystem processes Inputs FS Plant, animal and microorganism species Environment (abiotic) O Community (biotic) Outputs Nitrogen cycle Nitrogen in the atmosphere Nitrogen-fixing microbes (in the soil) D Nitrogen is found as a gas in the atmosphere (N2). It is an incredibly stable chemical, and comprises around 70% of our atmosphere. Very few living organisms can actually use the nitrogen found in the atmosphere, but all living things need nitrogen as it makes up substances such as proteins. Special microorganisms called nitrogen fixers change the nitrogen in the atmosphere into a form we can use. Lightning can also change some of the nitrogen in the atmosphere. Denitrifying bacteria return nitrogen to the atmosphere as nitrogen gas. Nitrogen is absorbed from the soil by plants, and then into animals that eat the plants. When living things die, decomposers break down the tissue of dead organisms and return the nitrogen back into the soil again. Nitrogen is often the substance that limits the growth of living organisms. When we farm, we tend to add extra nitrogen into the soil in a form that plants can use so they grow faster. For this reason, most fertilisers are nitrogen-based. Using too much nitrogen-containing fertiliser on plant crops can cause nitrate to run off from agricultural land into the waterways. PA G E Figure 3.2 The dynamic balance of ecosystems. TE Denitrifying bacteria EC Animals Decomposers Plants O Dead matter Nitrites in the soil Nitrifying bacteria Nitrifying bacteria Figure 3.3 The nitrogen cycle. U N C Ammonia in the soil Nitrates in the soil R R Lightning This excess of nutrients causes an effect known as eutrophication, which results in population explosions of microorganisms known as blue–green algae or cyanobacteria in the water – ‘algal blooms’. These blooms then deplete the ecosystem of nutrients required by different species, and also decrease the oxygen level in the ecosystem as the cyanobacteria decay. This often causes the community to crash. Figure 3.4 A ‘bloom’ of blue–green algae or cyanobacteria in water can be a sign of too much nitrogen in the ecosystem. 3.1 Components of ecosystems 85 03_CRA_IS9_77563_TXT_LAY.indd 85 28/08/13 2:34 PM FS O E Carbon is found in the atmosphere as carbon dioxide (CO2). Oxygen is present in carbon dioxide and as the oxygen gas we need to survive (O2). Carbon dioxide moves into the air during a process in cells called respiration, as well as through the decomposition of organic material. The only natural process that removes carbon dioxide from the atmosphere is the photosynthesis of plants. Scientists are now investigating the effect of the increasing levels of carbon dioxide in the atmosphere due to burning of fossil fuels. Burning of forests is a double threat to the amount of carbon dioxide in the atmosphere: carbon stored within plant tissues is released as carbon dioxide during burning, and the loss of trees means less photosynthesis to remove carbon dioxide from the atmosphere. Carbon and oxygen are found in places other than the atmosphere. Figure 3.5 shows the cycling of carbon and oxygen in the environment. They are changed and used in different ways in the different parts of the Earth. Table 3.1 shows how carbon and oxygen move through different spheres of the Earth: the atmosphere, biosphere, lithosphere and hydrosphere. As with nitrogen in the nitrogen cycle, carbon and oxygen can become part of different substances as they move through the environment. However, the overall net amount of each element does not change. PR O Carbon–oxygen cycle G Atmosphere CO2 Decomposition Respiration TE EC R Photosynthesis Photosynthesis Animals Plants Ocean Soil organic matter Marine deposits Coal, oil and gas Marble carbon sediments U N C O R Respiration D Fossil fuels PA Atmosphere O2 Earth’s crust Figure 3.5 The carbon–oxygen cycle. 86 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 86 28/08/13 2:34 PM Movement of carbon Movement of oxygen Found as carbon dioxide gas (0.03%) Released/produced by: • burning fossil fuels • respiration • decomposing organisms Used in: • photosynthesis Found as oxygen gas (21%) Produced by: • photosynthesis Used in: • respiration • some decomposition Also combines with carbon as carbon dioxide (see ‘Movement of carbon’) Biosphere (living world) Carbon dioxide used by plants in photosynthesis to form sugars and then other substances Produced by photosynthesis Used in respiration Lithosphere (the Earth’s rocks and soil) Found in variety of forms in fossil fuels, marine sediments, corals, limestone, marble Produced when living things decompose to become sediments that may change into fossil fuels or sedimentary rocks Released as compounds called oxides when minerals are mined Hydrosphere (the Earth’s waters) Carbon dioxide from air can dissolve in water to form weak acid Produced in photosynthesis, but is not very soluble and may move into atmosphere Used in some respiration U N C O R R EC PR O E G PA TE You have seen the importance of living things in the nitrogen and carbon– oxygen cycles. In the nitrogen cycle, microorganisms ‘fix’ nitrogen into a form our bodies can use. In the carbon–oxygen cycle, plants absorb simple substances, such as carbon dioxide and water, and convert them into sugars by photosynthesis. Plants make other compounds from the sugars using minerals, and store them for further use such as growth and reproduction. Animals eating the plants have access to the sugars and other compounds. When plants and animals die, decomposers (such as fungi and bacteria) break down the dead matter to obtain energy. Organisms do not absorb all the matter eaten. For example, cellulose in plant cell walls is not digested by some animals and is passed through the body unused. Decomposers act on this waste material. Decomposers break down organic chemicals into simple substances, which are released into the atmosphere, surrounding soil and water to be reused by plants, so continuing the cycle. Matter cycles can be easily disrupted by significant changes in the communities of living organisms that are a part of them. Eutrophication is the result of excess nitrogen in an ecosystem, leading to algal blooms. Although excess nitrogen seems like an advantage for the algae, the extreme population densities strip most of the other nutrients, specifically oxygen, from the water. Long term, all aquatic organisms are affected, as both the plants and animals that require oxygen for cellular respiration need to absorb it from the water. The clear-felling of forests and woodland to make way for grazing pastures has a double effect on the carbon–oxygen cycle. Less trees means less photosynthesis to remove carbon dioxide from the atmosphere and produce oxygen. High-density populations of stock like cows or sheep increase the amount of respiration, which increases carbon dioxide production and reduces the amount of available oxygen in the atmosphere. D Living things and the cycles of matter O Part of the Earth Atmosphere FS Table 3.1 Carbon and oxygen in the environment. 3.1 Components of ecosystems 87 03_CRA_IS9_77563_TXT_LAY.indd 87 28/08/13 2:34 PM Deeper u n d e r s ta n d i n g Termites recycle carbon PA G E PR O O FS Plant cell walls are made of cellulose, a complex carbohydrate that is insoluble in water and does not break down easily. Fungi break down cellulose and play a major role in the decomposition of wood, but fungi require a moist environment and cannot survive in the arid areas of Australia. In drier areas, such as the savannah grasslands of northern Australia, termites have a major role in decomposing and recycling carbon and other nutrients. Termites are social insects that live in nests. You may have seen the massive termite mounds in Kakadu National Park in the Northern Territory. Termites also have microorganisms that live in their gut, which break down the cellulose of plant material such as grasses, plants and wood. Scientists have estimated that termites recycle up to 20% of the carbon in ecosystems such as the savannah grasslands. Termites are not only responsible for the increased soil fertility around their mounds, but also provide food and even nesting sites for many animals. They are food for reduviid bugs (assassin bug), dunnarts, numbats, lizards, geckoes, skinks, bandicoots, echidnas and bilbies. They provide shelter for parrots, kingfishers, geckoes, pythons, beetles and mice. A species of monitor lizard even hijacks part of the mound to incubate its eggs. D Figure 3.6 (a) Termite mounds in Kakadu National Park and (b) the termites that build and live within them. EC Remember TE Questions 3.1.1: Cycles of matter 1 Recall the two ways nitrogen is converted into a form that can be used by living things. R 2 Identify the only natural process that removes carbon dioxide from the atmosphere. U N C O R 3 Identify the two main processes of the carbon–oxygen cycle and describe how they could be considered ‘opposites’. Apply 4 Describe some ways plants and bacteria contribute to the nitrogen and carbon– oxygen cycles of matter. 5 Discuss ways in which humans have changed biogeochemical cycles. 6 Compare the ways that nitrogen and carbon enter the biosphere. 7 Explain the role of termites as decomposers in the savannah grasslands of northern Australia. Why are they necessary? 88 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 88 28/08/13 2:34 PM Energy in ecosystems G E PR O O FS Not all the energy UNIVERSE in ecosystems is passed on. Some of Solar energy Biological systems the energy is used by living things (to do work), and much of the energy is lost to Chemical energy the atmosphere as heat. Only 10% of Heat energy Matter is the available energy recycled at each food chain level is passed on to the next level. Energy cannot be created or destroyed (we say it is Figure 3.7 Energy flow conserved and transformed), but energy in a through ecosystems and the recycling of matter. useable form is often lost. Energy moves and changes in ecosystems, but unlike matter, it is not recycled. Living systems must continuously take in the Sun’s energy. PA All ecosystems rely on movement of energy from one part to another. The first source of energy in most ecosystems is the Sun. However, only plants and other photosynthetic organisms can use solar energy directly. These types of organisms are called autotrophs or producers. All animals and some microorganisms cannot use the Sun’s energy and must obtain their energy through food they eat. Organisms that require a source of food for their energy are called heterotrophs or consumers. Energy is passed through ecosystems via food chains and food webs. Plants and other photosynthetic organisms originally harness solar energy. This energy is then passed to the herbivores that eat the plants. Carnivores obtain their energy from the herbivores they eat, and so on. Activity 3.1.2: Modelling energy transfers in the environment EC TE D Energy can be difficult to imagine because it comes in so many different forms. Energy can be transferred and transformed, but it cannot be created or destroyed. However, many of the different forms of energy cannot be passed on through an ecosystem. This activity demonstrates the proportions of energy that are used up by each step in the food chain, that can be passed along or that are ‘lost’ in the form of heat. What you need: 2 L bottle of coloured water, 10 mL and 100 mL measuring cylinders, 4 plastic cups for each organism, dropper R R 1 Work in groups of four to represent four different parts of the food chain: the Sun, a native grass (producer), a cricket (herbivore) and a wedge-tailed eagle (top consumer). C O 2 Use the bottle of coloured water to represent the Sun’s energy. The total energy available from the Sun is equal to the volume in the bottle (2000 mL). N 3 Give a cup to each person representing a part of the food chain. U 4 The plant receives, through photosynthesis, 3% of the solar energy available to it: 3% of 2000 mL = 60 mL. Measure and pour 60 mL of coloured water into the plant’s cup. 5 The herbivore receives 10% of the energy: 10% of 60 mL = 6 mL. Measure out 6 mL from the plant’s cup and pour this into the herbivore’s cup. 6 The top consumer receives 10% of this energy: 10% of 6 mL = 0.6 mL. Use the dropper to take out about 0.6 mL from the herbivore’s cup and pour this into the top consumer’s cup. • Explain why are there fewer top consumers in an ecosystem than herbivores. • Explain what has happened to the 1940 mL of ‘energy’ from the Sun that did not pass into the plant. overmatter 3.1 Components of ecosystems 89 03_CRA_IS9_77563_TXT_LAY.indd 89 28/08/13 2:34 PM Energy for work When we need a quick boost of energy, we often choose sugary foods to eat. Although sugars contain energy locked in the bonds of their molecules, this energy cannot be used directly by organisms. They must first convert it into other forms. Many energy transformations keep a living organism alive, functioning and carrying out chemical reactions that keep cells working. We can describe these processes as the work of living organisms. Some of the types of ‘work’ performed by living organisms are shown in Table 3.2. Table 3.2 The ‘work’ of living organisms. Examples Building compounds All organisms use energy to build and replicate molecules, such as lipids (fats), DNA (deoxyribonucleic acid), RNA (ribonucleic acid) and proteins, so they can manage metabolic processes, grow and pass information on to offspring. Communication inside an organism Energy is needed for communication within and between cells. Electrical energy and chemical energy are used when nerves transmit information throughout the body, or when hormones are produced Physical movement Energy is supplied for voluntary movement, such as movement of leg or arm muscles, or for involuntary movement, such as contraction of the heart or movement of plants towards sunlight. Transport Energy is required to move substances, such as nutrients and wastes, throughout an organism’s body. G E PR O O FS Type of work Photosynthesis PA 2.0 1.8 1.4 D 1.2 1.0 TE Photosynthesis rate 1.6 0.8 0.6 EC 0.4 0.0 0 1 2 3 R 0.2 4 5 6 U N C O Figure 3.9 The rate of oxygen produced during photosynthesis is affected by the intensity of light. R Light intensity All living things need energy to grow, reproduce and repair, defend themselves and to move. Plants, some algae and some bacteria are able to gain this energy during photosynthesis. In this process, glucose is synthesised (made) from water and carbon dioxide. This requires light energy and the presence of an organic catalyst called chlorophyll, which is found in cellular organelles called chloroplasts. Chloroplasts are concentrated in the cells of plant leaves. Stomata in the leaves are tiny pores through which the carbon dioxide needed for photosynthesis enters and the oxygen exits (see Figure 3.8). The solar energy is converted into chemical energy in the bonds of glucose. The overall equation for photosynthesis is: carbon dioxide + water → glucose + oxygen 6CO2 + 6H2O → C6H12O6 + 6O2 Figure 3.8 The stomata of a plant (seen here under a microscope) are opened and closed by guard cells to allow the gas exchange of oxygen and carbon dioxide. Photosynthesis produces oxygen and removes carbon dioxide from the atmosphere. The glucose product is soluble and readily transported around the plant. Any extra glucose can be converted into 90 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 90 overmatter 28/08/13 2:34 PM Experiment 3.1.1: Starch production and light Aim To find out whether light is necessary for the production of starch in leaves. Hypothesis Construct an ‘If … then …’ statement that predicts the effect of light on the production of starch in leaves. Materials O FS 4 Petri dishes Methylated spirits Iodine solution Aluminium foil Paper towel PR O • • • • • >> Methylated spirits is highly flammable and must not be heated using a naked flame. E WARNING • 4 soft-leaved plants (such as geraniums) of the same size, shape and colour, in seedling pots • Hotplate and water bath • Beakers (250 mL) • Tongs G Method PA 1 Label two plants A and two plants B. Place them in a dark cupboard for two days. (This is to ensure that no starch is present in the leaves. You should be able to verify this at step 6 – there should be no change in the colour of iodine.) D 2 Break off one leaf from each plant. Place leaves from the A plants in one beaker, add water and boil for several minutes (leaves should become soft). Repeat with the leaves from the B plants. EC TE 3 Place the A leaves in a new labelled beaker containing methylated spirits, and place the beaker carefully in a water bath. Leave them for 5 minutes or until the chlorophyll has been removed from the leaf. 4 Remove the leaves with tongs, rinse with water and pat dry with paper towel. R 5 Place the leaves in a Petri dish and add 2–5 drops of iodine solution, just enough to cover the leaf. R 6 Observe any colour change and record your observations. O 7 Repeat steps 3–6 with the B leaves. C 8 Repeat step 1, then place aluminium foil over the leaves of the two A plants and place all plants in sunlight for several days. N 9 Complete steps 2–7, ensuring you test the foil-covered A plant leaves. U Results Include your observations in a table. Discussion 1 Which plants, A or B, were the control group? 2 Identify the dependent variable. 3 Identify some controlled variables. 4 Explain why a positive test for starch is considered an indication that photosynthesis has occurred. 5 Is this experiment quantitative or qualitative? Explain your answer. 6 Suggest a change to improve the method if you were to repeat this experiment. overmatter 3.1 Components of ecosystems 91 03_CRA_IS9_77563_TXT_LAY.indd 91 28/08/13 2:34 PM Student Design Task Understanding photosynthesis Choose one of the following questions and then design and conduct your own experiment. 1 Is chlorophyll necessary for photosynthesis? 2 Do increased levels of carbon dioxide increase the rate of photosynthesis? Questioning and predicting FS Consider the question you have chosen to investigate. Write some ‘what if’ questions related to your topic. Make a prediction about each of your questions. Convert your questions and predictions into ‘If … then …’ hypotheses. O Planning investigations PR O Identify the experimental variable for your experiment. Consider all other variables that may affect your results and how you will control these. Write a clear, step-by-step method for your experimental procedure. EC TE D PA G E Here are some ideas to help you: • Variegated leaves with green and cream patches contain areas where chlorophyll is present and patches where it is absent. • You may need to grow plants in a sealed, controlled atmosphere. One way is to grow the aquatic plant Elodea in a beaker of water. Place the Elodea under an inverted filter funnel that has been sealed from the air (by inverting a test tube full of water over the top). The bubbles of oxygen released by the plant will rise up through the funnel into the top of the test tube, displacing water and indicating the rate of oxygen production. • Plants release oxygen as a result of photosynthesis, and this can be seen as bubbles around the leaves of aquatic plants. • Carbon dioxide is released in some chemical reactions or is released by respiring animals. Some antacid tablets, such as Alka-Seltzer, release carbon dioxide when added to water. Conducting investigations R R Discuss your method with your teacher and get their approval. Revise your method if required. Then, carry out your experiment according to your method. Processing and analysing data and information U N C O Record all observations and determine if there are any trends (patterns) or cause-andeffect relationships. Is your data qualitative or quantitative? Problem solving What problems did you encounter during your experiment? Was there a problem with your method? Did something unexpected happen? Suggest ways to improve or extend your experiment with further testing. Communicating Present your findings as a formal scientific report. 92 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 92 28/08/13 2:34 PM O C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP FS glucose + oxygen → carbon dioxide + water + energy Stored chemical energy (ATP) is released as required for cellular work, but the release is much slower and more controlled than burning fuels such as wood. N C O R R EC TE D PA G E Whenever we burn a fuel, such as wood or oil, we release energy that has been chemically stored in the molecules. Burning requires oxygen and is a very rapid process, producing a lot of heat energy, carbon dioxide and water. In living organisms, sugars such as glucose contain energy, but it is not directly useable. If all the energy stored in the bonds of glucose were released at once, the rapidly produced heat would be more than enough to cook the cells of living thing. Energy from the breakdown of glucose must first be transferred to a molecule called adenosine triphosphate (ATP) before it can be used in cells. This occurs in organelles called mitochondria in a process called cellular respiration. ATP contains energy that is directly useable by cells. Oxygen is used when it combines with glucose during cellular respiration. As well as glucose, fats and proteins can be used to produce ATP. The energy stored in the chemical bonds of glucose (C6H12O6) is transferred slowly into ATP. Carbon dioxide and water are waste products. The overall equation for cellular respiration is: PR O Cellular respiration U Figure 3.10 ATP (adenosine triphosphate) molecules are the energy currency of organisms. 3.1 Components of ecosystems 93 03_CRA_IS9_77563_TXT_LAY.indd 93 28/08/13 2:34 PM Photosynthesis and respiration: ‘opposite’ reactions Sun ECOSYSTEM PR O O Light energy Glucose Respiration Energy for plant cells Energy for animal cells R stored or changed into other useful Figure 3.11 Energy is transferred from (a) light to plant cells and (b) from organic substances Heat energy Figure 3.12 Energy flows into an ecosystem as sunlight. Plants trap this energy in the chemical bonds of matter such as glucose. The glucose, produced during photosynthesis, is used in respiration. U N C O R plants to animals. Glucose and oxygen is the energy source for most cellular activities TE Respiration Glucose EC Digestion Cellular respiration in mitochondria ATP D stored or changed into other useful organic substances Plant Photosynthesis in chloroplasts PA Photosynthesis G E CO2 + H2O Chlorophyll in plants FS Photosynthesis and respiration are effectively the opposite of each other. Photosynthesis traps energy from the Sun into chemical bonds, such as those of glucose. Respiration moves the energy out of glucose, where it can be accessed directly by cells. However, the chemical equations listed here are only summaries of the processes. Both photosynthesis and respiration are actually a series of smaller reactions that involve many more compounds than those in the summary equations. These processes are not reversible because respiration and photosynthesis require their own specific enzymes to catalyse the reaction in one direction. But the net result of this pair of processes is to undo the other. Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 94 28/08/13 2:34 PM Deeper u n d e r s ta n d i n g diversity are also shown. All ecosystems were originally natural ecosystems, and some of them have been changed into agricultural and urban ecosystems. Comparing ecosystems Table 3.3 shows the energy and matter inputs and outputs of three types of ecosystems. Their complexity, stability and Table 3.3 Comparison of urban, agricultural and natural ecosystems. Complexity and stability Mainly fossil fuels, nuclear, hydroelectric Excessive burning Little with rapid heat output Little; humans dominate Simple; unstable: imbalance of animals over plants Agricultural Mainly light and fossil fuels Mainly photosynthesis and respiration with gradual heat output Some Little; single crop species or animals dominate (monoculture) Simple; unstable Natural Light Mainly photosynthesis and respiration with gradual heat output Nearly all High Complex; relatively stable PA Questions 3.1.2: Energy in ecosystems FS Diversity O Urban Matter recycling PR O Energy use E Energy input G Ecosystem Remember 1 Outline the difference between energy and matter. D 2 Outline the differences between a flow of energy and a cycle of matter in an ecosystem. TE 3 Identify some uses of energy in the bodies of living organisms. 4 Identify the source of energy for cellular respiration. EC 5 Write a general equation for cellular respiration. R Apply 6 Explain why cellular respiration constantly occurs in cells. R 7 Identify the raw materials needed for photosynthesis. Explain how they enter a plant. C O 8 Explain why it is fair to say that photosynthesis is essential to the functioning of almost all ecosystems. U N 9 Outline how cellular respiration and photosynthesis are related. 3.1 Components of ecosystems 95 03_CRA_IS9_77563_TXT_LAY.indd 95 28/08/13 2:34 PM Relationships in ecosystems Collaboration FS Collaboration occurs when organisms cooperate with each other to ensure their survival. This usually occurs in species that exist in large populations. Examples include: • ants – leaving a scent trail when they search for food so other ants can find the food too O • wolves – hunting in packs PR O • sea lions – leaving pups in crèches to be looked after while they go hunting E • flowering plants – growing close together to increase the chances of crosspollination • fish – swimming in large schools help confuse predators and avoid being eaten. PA G A community and the relationships between individuals in the community make up the biotic part of an ecosystem. In every community you will find producers, herbivores, carnivores and decomposers. Complex interactions happen between these living things. Predators hunt for their food, herbivores keep an eye out for carnivores to avoid being eaten, and decomposers slowly break down dead plants and animals. Organisms compete within their own species and with other species in the community for food and other resources. Although some organisms do not have any direct effect on each other in an ecosystem, most organisms have some kind of relationship. These relationships may be beneficial, neutral or detrimental (harmful), and they may be ongoing or short-lived. Relationships may be between organisms of the same or different species. TE D Relationships within a species R R EC Mating between same-species partners produces viable offspring, thus ensuring the survival of the species. All sexually reproducing species must come together at U N C O Figure 3.13 The fish in this school swim together to make it harder for the shark to single out individuals to eat. Intraspecific (intra meaning within; specific meaning species) relationships exist between individuals of the same species, usually of the same population. There are three main types of intraspecific relationships. Mating Figure 3.14 The female seahorse lays her eggs inside the male’s pouch where he fertilises them and carries them until they are ready to hatch. 96 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 96 28/08/13 2:34 PM some stage in their life cycle. Some species may live in large groups of males and females, like antelope. In other species, like orang-utans, the genders live separately until breeding season. The young usually stay with their mother until they are old enough to fend for themselves. Many plants sexually reproduce, but often need the help of the wind or a pollinator to bring the pollen (sperm) to the ovum (egg). • predators like lions compete over food U N C O R R EC • birds compete over nest sites. FS O PR O E Figure 3.17 Symbiosis: A lichen is an alga and a fungus, although you cannot see the two organisms separately (except under a microscope). The alga photosynthesises and the fungus supports the alga and provides it with other nutrients. Beneficial or neutral relationships Mutualism, symbiosis and commensalism are examples of relationships between different species. Mutualism is a relationship between two organisms in which both organisms benefit. A relationship between two species that are so interdependent that neither can survive without the other is called symbiotic. Lichen is an example of a symbiotic relationship, whereas the anemone and anemone fish is an example of only mutualism. Mutualistic and symbiotic relationships tend to last a long time, often a lifetime. These relationships have driven adaptation to better suit the other species. For example, flowers have evolved to take on particular colours and shapes, and to produce specific scents and nectars, to better attract specific pollinators. Commensalism is a relationship in which one organism benefits and the other organism is not affected. Commensalism is relatively rare in the natural world – it is unlikely an organism that has a relationship with another will not be affected in some way. TE • males compete for the right to mate with females Interspecific (inter meaning between) relationships exist between individuals or populations of different species. These relationships can be beneficial or detrimental to one or both species involved. G Examples include: • seedlings from the same plant species compete with each other for light and space as they grow Relationships between different species PA Competition occurs when organisms use the same limited resource. Organisms will compete for all possible resources if there is not enough for everyone. Individuals that are good competitors will get more of the resource than weaker competitors. Those that do not gain enough of that resource may die. D Competition Figure 3.16 Mutualism: The anemone fish hides within the tentacles of the sea anemone, where it is camouflaged from its predators. The sea anemone is cleaned of algae and parasites by the fish. Figure 3.15 The two male bison are competing to mate with females. Figure 3.18 Commensalism: Sometimes herbivorous animals, such as cattle and water buffalo, flush insects out of the grass as they wander through. Birds, such as cattle egrets, feast on the insects and therefore benefit. However, the cattle are unaffected by this relationship. Figure 3.19 Commensalism: Certain plants rely on passing animals to disperse their seeds. The seeds have tiny hooks to attach to overmatter 3.1 Components of ecosystems 97 03_CRA_IS9_77563_TXT_LAY.indd 97 28/08/13 2:34 PM Detrimental relationships FS O Number of prey Number of predators Prey PR O Figure 3.22 Parasitism: Ticks attach to the skin of animals and slowly drink their blood. Bacteria from the digestive system of the tick can infect the animals. Predator–prey, parasitism and competition are relationships in which at least one of the species has the potential to be greatly harmed. In a predator–prey relationship, the predator organism eats the prey organism. Therefore the predator benefits and the prey is harmed. The predator–prey relationship is not long-term and only happens when a predator has the opportunity. Predators and their prey have a balanced relationship with each other. If all the prey is eaten then the predator is disadvantaged. Figure 3.20 shows a typical graph of predator–prey population fluctuations. Predator G Figure 3.21 The eagle is the predator and the fish has definitely been harmed! PA EC TE D Parasitism is a relationship in which one organism (the parasite) lives in or on the body of another (the host). The parasite benefits and the host is harmed to varying degrees. A good parasite can survive and reproduce inside its host for close to the normal life span of the host. However, if the parasite takes too many nutrients from the host, the host may get sick or even die. If the parasite cannot leave the host in time, they too will die. Competition may exist between members of different species that share a resource such as food or nesting sites. Many different animals nest in tree hollows. The removal of dead trees reduces the number of nesting sites and increases the competition for them. Without adequate shelter, many animals cannot reproduce or survive. Inhibition, or allelopathy, is a particular type of competition that occurs when one organism produces a chemical that directly inhibits or hinders the growth and development of another. This is commonly seen in plants and microorganisms. N C O R R Figure 3.23 Parasitism: Hookworms attach themselves to the inner lining of the human intestine, feeding on nutrients as they pass by. The host will often lose weight from lack of food. If the host doesn’t eat enough, the worm has been known to burrow out of the intestines and travel to other organs, where real damage can be done. Figure 3.20 A predator–prey graph. The scales aren’t shown but the prey numbers are mostly greater than those of the predators. Notice the increase and decrease in prey numbers usually comes before the increase and decrease in predator numbers. E Time U Figure 3.24 Competition: A black periwinkle (Nerita) competes for food with the limpet (Cellana) on a rock platform – both feed on algae growing on the rocks. The periwinkle moves faster but feeds less efficiently than the limpet, so both can survive as the periwinkles usually leave behind some algae for the limpets. However, when the periwinkles are removed, the limpet population increases. Figure 3.25 Inhibition: Penicillium is a fungus that produces penicillin, an antibiotic that inhibits the growth of many species of bacteria. Figure 3.26 Inhibition: The Lantana plant, an introduced species in Australia, releases a chemical in the soil that inhibits the growth of native plant species. 98 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 98 28/08/13 2:35 PM Experiment 3.1.2: Observing competition Aim To identify some factors that affect competition in germinating seeds. Materials Packets of seeds (a variety of vegetables or flowers is needed) Small plot (20 × 20 cm) in a garden, divided into thirds (alternatively, 3 mediumsized pots containing good-quality potting mix) Measuring cylinder or graduated jug for watering O Method FS Hypothesis Use your knowledge of the resources required by plants to write an ‘If … then …’ statement to predict the outcome of this experiment. PR O 1 Prepare the plots so the soil is moderately deep and smooth. Label them A, B and C. 2 In A, densely scatter the seeds of one type (for example, only radish seeds). 3 In B, plant six seeds of the same type as for step 2, but spread evenly apart. 4 In C, densely scatter a variety of seeds. E 5 Water the soil each day as evenly as possible with the same amount of water. PA G 6 Record the growth of the seeds. If possible, take photographs each week or every few days when the seeds begin to germinate. If the seeds become seedlings (small plants), their heights may be measured and recorded in a table. TE D Results Record all results. You could take photos showing the progress of growth and/or record the average heights of plants of different species and record them in a table. Discussion EC 1 What assumptions did you make when drawing a conclusion? 2 How could you have improved the validity and reliability of this experiment? R 3 What would be your advice to another student who wants to perform the experiment? R 4 Was there evidence of competition between the seeds as they germinated? Explain using your results. O 5 Are there other factors that might affect the growth of seeds? C 6 If you were to complete this experiment again, how would you improve or extend it? N 7 Have you previously observed competition between organisms in the natural environment? If so, describe it. U Conclusion Write a conclusion regarding the factors that affect competition between germinating seeds. 3.1 Components of ecosystems 99 03_CRA_IS9_77563_TXT_LAY.indd 99 28/08/13 2:35 PM Activity 3.1.3: Pollination – the benefits are mutual The pollination of flowering plants by animals and other agents has contributed to the great success of these plants and their dominance in many parts of the Earth. In return, a diverse range of insects, mammals and birds benefit from ‘rewards’ offered by flowering plants. What you need: computer with access to the Internet, printer, paper, pens and pencils Perform this exercise as a small-group activity and produce a single report as a group. • the grouping of pollinators into different types O • advantages of pollination to the pollinator and to the plant FS 1 Research examples of the pollination of flowering plants on the Internet. A good place to start is the Plant2pollinator resource in the Australian Museum website’s ‘Bugwise for Schools’ section. Items to consider include: PR O • patterns in pollination, for example, grasses and cereal crops of the world (they are flowering plants – how are they pollinated?) 2 Takes notes about the information you think is important. Remember to write the full reference for each of your sources of information, and to summarise and paraphrase. E 3 Analyse the information and process it into a short report on pollination with examples, photographs and diagrams. PA G 4 Share your group’s report with another group or discuss as a class. A dynamic balance O R R EC TE D All organisms live in a complex web of interrelationships – with each other and with their environment. Many of these relationships are between living things, as you have seen. Non-living (abiotic) factors play a critical role in determining what type of community survives at a particular place. Abiotic factors include the physical and chemical parts of the environment. Abiotic factors in terrestrial (land-based) ecosystems are different from those factors in aquatic (water-based) ecosystems. Sunlight, temperature, rainfall and soil type are all examples of physical factors. Chemical factors include availability of minerals, oxygen and carbon dioxide, and soil or water pH and salinity. Ecosystems in New South Wales include arid grasslands, rainforests, rock platforms, mangroves, salt marshes, sand dunes, freshwater lakes, mallees and alpine herbfields. Some people distinguish natural ecosystems from agricultural and urban ecosystems, which are dominated by people. A group of organisms of the same species U N C Figure 3.27 Pollination involves the transfer of pollen from the male parts of flowers to the female parts of other flowers of the same species. Animal pollinators, such as bees, small mammals or birds, visit the flowers for food such as nectar. The pollinators then transfer the pollen when they visit other flowers. Pollen may also be carried by wind or water. living in the same ecosystem is called a population. An ecosystem needs to be able to maintain a balance so all species can exist at their optimum population size. Gains due to reproduction and immigration (moving in) must balance the losses due to death and emigration (moving out). Changes in one species’ population can dramatically affect the population of a different species. Consider the food web for the ecosystem shown in Figure 3.28. Frog numbers have decreased in parts of Australia for reasons still being researched. If frogs decreased in this particular ecosystem, consequences could include: • an increase in grasshoppers and thus a loss of grass • an increase in praying mantises • a decrease in lizards • a diversion of birds towards a diet of praying mantises rather than frogs and lizards • a consequent decrease in praying mantises • a further increase in grasshoppers and 100 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 100 28/08/13 2:35 PM more loss of grass – if this was severe enough the ecosystem would be at risk as it depends on a good supply of grass. Praying mantis Grasshopper Frog Figure 3.28 Changes to the frog population will affect all other species in the food web. O naturally but they may be intensified by factors such as floods and bushfires. Reproduction, death, migration, natural Lizard FS Grass Bird overmatter PR O The most likely outcome is that the bird population would decrease so all species would return to balance with reduced population sizes. A positive effect is that it might enable the frog population to recover. Ecosystem balance is a type of dynamic equilibrium (dynamic means changing; equilibrium means balance). Changes may upset the equilibrium but another equilibrium becomes established. Often, it is not greatly different from the original. Gains and losses in ecosystems occur Relationships in ecosystems Remember G E 1 Identify one similarity and one difference between a predator–prey relationship and parasitism. 2 Define ‘intraspecific competition’. Benefitted Species B Commensalism Benefitted Predator–Prey Parasitism Predator: Host: Prey: Parasite: Competition EC Benefitted TE Species A Symbiosis D Mutualism PA 3 Complete the following table about interspecific relationships by indicating which species is harmed, benefitted or unaffected: O R R Apply 4 In some eucalypt trees, leaves similar in appearance to the eucalypt leaves hang down from the branches. These are leaves of the mistletoe plant. They can make their own food but their stems send suckers into the eucalypt to obtain water and minerals. If too much water and minerals are removed, the eucalypt can die. Identify this type of relationship and the roles the eucalypt and mistletoe plants play. Justify your decision. U N C 5 Epiphytes are plants that grow up high in the branches of other trees, especially rainforest trees. Examples are some orchids and ferns. The epiphytes obtain enough light to make their own food, they collect water from the moist air, and they obtain minerals from the decaying leaf litter they catch at their leaf bases. These plants do not affect the tree. Identify this this type of relationship. Justify your decision. Analyse and evaluate 6 Outline why it is important to have a variety of producers, consumers and decomposers in an ecosystem. 7 Propose some ways that organisms could become extinct in an ecosystem. 8 Explain how predator–prey populations are interdependent. Are there any benefits of this relationship for the prey? 9 Ecosystems are said to be in a state of equilibrium or balance. Give an example of how a change in the environment may lead to changes in the living community and overmatter 3.1 Components of ecosystems 101 03_CRA_IS9_77563_TXT_LAY.indd 101 28/08/13 2:35 PM 3.1 Components of ecosystems Remember and understand 8 If only 10% of the energy is transferred along a food chain (Figure 3.29), explain what happens to the rest of the energy. [2 marks] 1 Define abiotic and biotic components of ecosystems. [1 mark] 5 Identify the products of photosynthesis essential for cellular respiration. [1 mark] Apply 11Some succulent plants that grow in very hot and dry conditions have reversed the opening and closing rhythms of the stomata in the leaves that allow gases to exchange. They open during the night and close during the day. Suggest a disadvantage for the plants that do this. [1 mark] PA G 6 Describe how the flow of energy differs from the flow of matter through an ecosystem. [2 marks] FS 4 Describe how plants obtain the raw materials needed for photosynthesis. [1 mark] 10Respiration in your cells provides the energy for all your metabolic processes. Identify six different cellular processes that require energy from respiration. [3 marks] O 3 Outline the process of photosynthesis. [2 marks] 9 Explain the difference between respiration and photosynthesis. [2 marks] PR O 2 Explain what mutualism, parasitism and commensalism have in common. How are they different? [3 marks] E Checkpoint EC TE D 7 Can competition occur between members of the same species and members of different species? Explain with examples. [2 marks] R 1 unit of energy Top consumer Heat Heat 10 units of energy Primary consumers N C O R Secondary consumers U Decomposers 100 units of energy Heat Producers 1000 units of energy Heat Figure 3.29 Energy transfer is diminished along a food chain. 33 300 energy units 12Draw a concept map showing how photosynthesis and respiration are connected using the following terms, plus any others you think are appropriate: glucose, energy, oxygen, carbon dioxide, ATP, water. [6 marks] 13Observe your school ground or your home garden for about a week. Keep a journal listing any examples of interrelationships between organisms. [2 marks] Analyse and evaluate 14Is it more beneficial for a flowering plant to be pollinated by only one species of pollinator or a variety of species? Explain. [2 marks] 15Analyse the marine Antarctic food web in Figure 3.30. Sun a Identify the relationship between humpback whales and lobsters. [1 mark] 102 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 102 28/08/13 2:35 PM b Identify the relationship between emperor penguins and fur seals. [1 mark] c If overfishing rapidly decreases deep-sea fish numbers, what pressures could this place on the seal population? [1 marks] Deep-sea fish d What pressures would overfishing have on the humpback whale population? [1 marks] Squid Phytoplankton FS Lobster PR O O Figure 3.30 A simplified marine Antarctic food web. Rock platform Acmea PA G Lottia E 16 Explain how the carbon–oxygen transfer between animals and plants is like a battery that powers the biosphere. Think about how we use batteries and how this can be similar to what happens in photosynthesis. [2 marks] D Ocean TE 17Our understanding of how plants work has changed over time. Research some of the important scientists in this field and how they have contributed to our understanding of plants. For instance, who came up with the name ‘photosynthesis’ and why? Who discovered that plants release oxygen during the day? You might like to produce a timeline from Aristotle to the 21st century. [5 marks] Orca whale Fur seal Emperor penguin Humpback whale R R EC 18Limpets graze on algae on a rock platform. The large limpet, Lottia, is found in a territory containing microalgae, and the smaller species, Acmaea, is found on the edge of this territory (Figure 3.31). C O a Propose one possible reason (hypothesis) for this situation. [1 mark] U N b Describe an experiment you might set up to test if your hypothesis is correct. Identify the experimental variable, the dependent variable and the variables you would need to control. [4 marks] Critical and creative thinking 19Imagine it is your job to find out if soil is ‘consumed’ as plants grow. Design an investigation to test this idea. How will you tell if the plant(s) have actually Figure 3.31 Lottia and Acmaea on a rock platform. consumed the soil? What evidence do you need to collect? What variables do you need to control? How will you set up a control? What is the purpose of the control? What is your hypothesis? [5 marks] Making connections 20Scientific understanding of the relationship between plants and animals in an ecosystem is an important area of scientific research. Ecologists are scientists who specialise in this area of research. Examine what an ecologist does. Write a paragraph that describes the highlights of working as an ecologist plus some of the disadvantages. [4 marks] TOTAL MARKS [ /55] 3.1 Components of ecosystems 103 03_CRA_IS9_77563_TXT_LAY.indd 103 28/08/13 2:35 PM 3.2 Changing populations The population size of some species remains constant over time. Other populations change in numbers. Population size is determined by natural factors such as births, deaths, immigration and emigration, climatic change, natural disasters and introduced species. Human impact may also have a major influence on populations of our own and other species. E PR O O ecosystem may be to monitor the population size of a particular species, or to measure the biodiversity of the area. Scientists can make predictions and take certain precautions to conserve species if they know approximately how many of each species are in a certain location. Regular sampling provides information about increases and decreases in population numbers, and causes of the changes can be identified. D PA G A common indicator of the health of a natural ecosystem is its biodiversity. Biodiversity is a measure of the number of different species in an ecosystem (bio meaning life; diversity meaning different). A rainforest with thousands of different species has very high biodiversity, but potentially a low population of each species. A field of wheat might have millions of individual plants in the population, but very low biodiversity due to the vast majority of individuals in the community being the same species. In any one ecosystem you must consider all the different kingdoms represented. Microorganisms are important to the health and functioning of an ecosystem, as are all the plants and animals. Significant changes to any of the populations within the community can seriously affect the others. Ecosystems that have high biodiversity tend to be more resilient to environmental change. An individual species might die out in that ecosystem, but due to the different characteristics and adaptations in the different species, some will survive the change. For example, if a fungus infects a field of wheat, it could potentially kill every plant in the field. If one individual is susceptible to that disease, it is likely that every individual of the same species will also be susceptible. However, if the same fungal disease infected the rainforest ecosystem, only some plants will be affected while different species will have a natural resistance and survive. Population dynamics is the study of the fluctuations (changes) in population numbers within ecosystems. Surveys of an FS Population dynamics Births R EC TE Immigration U N C O R Population size Emigration when food scarce Deaths Figure 3.32 A galah population in a particular area depends on the food available and the number of births and deaths. 104 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 104 28/08/13 2:35 PM Activity 3.2.1: Human population Consider the human population. The number of people in a population increases and decreases in different parts of the world for a wide variety of reasons. 1 List as many reasons as you can for population change, then share your list with a partner. 2 Contribute your reasons to a comprehensive class list. Identify the factors that: • would cause increase or decrease in numbers • are related to human actions. 3 Discuss whether or not these factors can or should be controlled. E G PA Figure 3.33 Quadrat sampling counts every organism within the quadrat frame. U N C O R R EC TE D There are a number of ways to determine the size of a population. Counting every individual organism in a population is the most accurate way, but in practice this is rarely possible and very time-consuming. Estimates are more easily achieved by surveying from helicopters or using quadrats, transects or capture–recapture methods. For human populations, a census is the usual method. A census actually takes information about every individual in a population. For plants and stationary animals, quadrats (square plots) are most commonly used for population estimates. The quadrat frames are either randomly placed (tossed over the shoulder) or sequentially marked out in a designated area within the ecosystem. Every individual is counted in each plot and its species noted. An average number of each species is calculated for each quadrat and then used to estimate the total number of organisms in the ecosystem (by using the known total area of the ecosystem). This method works well if a large number of quadrats are used and the organisms are small and relatively evenly spread or dispersed throughout the ecosystem. A line transect is an excellent method of examining the diversity of an ecosystem and the distribution of a particular species over a varied ecosystem. A straight line, often a measuring tape, is placed through an ecosystem. Any organism that touches the line (including directly under or over it) is counted and its species noted. This PR O O Counting organisms FS • would cause significant or minor changes in numbers Figure 3.34 Line transect sampling counts organisms that touch or cross the tape. 3.2 Changing populations 105 03_CRA_IS9_77563_TXT_LAY.indd 105 28/08/13 2:35 PM An estimate of the population is then obtained using the formula: Estimated total number of animals N ×N E PR O O FS 1 2 = ______ M2 It is assumed that the probability of capturing animals on both occasions is the same, but this is not always the case. The animals may not like the traps and may avoid them on the second occasion, or they may love the bait (often muesli, honey, peanut butter or oats for small mammals) and deliberately come back for more! The marking can be temporary, like food dye, and wear off within a few days, or it can be more permanent like leg rings, ear tags or GPS inserts. These more permanent tags enable ecologists to follow individual animals over long periods of time and can be used to gather data on distribution, migration and long-term changes to populations. But it is also important to ensure the tagging does not affect the normal lifestyle of the organism so it does not affect its survival. For example, tagging a possum pink would cause it to be more visible to predators and less appealing to potential mates. Capture–recapture is a very suitable technique for estimating the population size of small Australian mammals such as the marsupial Antechinus – the common bush rat. Because most native Australian mammals are nocturnal (awake at night), the traps may be set at night and checked the next morning. U N C O R R EC TE D PA G may be done along the whole length of a short transect, or at regular intervals (every metre) along a long transect. A number of parallel transects can be used to calculate an average of each species at each distance along the line. Transects are also only used for plants or stationary (sessile) animals. They are particularly useful in an ecosystem where the conditions change significantly in predictable bands, like intertidal zones. For most mobile animals, capture– recapture is a popular method for population estimation. Animals are captured in traps then marked with tags or other marks such as food dye or permanent marker on their tails, feet or other easily seen body parts. The number counted on the first capture is N1. The animals are then released and it is assumed they disperse evenly throughout the population. They are then recaptured one or two days (or nights) later and the total number of animals in the second capture is N2. Not every animal that was captured in the first trapping session will necessarily be caught the second time, and new individuals may be captured in the second trapping session. The number of marked animals in the recapture, those that have been captured twice, is M2. Figure 3.35 Once captured, many measurements are taken and recorded for each individual before they are marked and released. 106 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 106 28/08/13 2:35 PM caught (N2), of which 12 were tagged (M2), the estimate of the population would be 275 fish. Capture–recapture population estimates Capture–recapture is a common technique for estimating animal populations. To obtain accurate estimates, the process may be repeated over a number of weeks and the estimates averaged. Estimated total number of animals N ×N 1 2 = _____ M 2 55×60 = _____ 12 Estimated total number of animals FS 3300 = ____ 12 N1×N2 = _____ M2 =275 where: N1 = the total number of individuals captured and marked in the first session O Your turn A team of ecologists was hired to investigate the population of ring-tailed possums in Katoomba, NSW. On the first night they captured 48 possums, marked their tails with blue food dye and released them. Two nights later they trapped 42 possums, only 8 of which had blue dye on their tails. Estimate the population of ringtailed possums. PR O N2 = the total number of individuals captured in the second session. If 55 fish were initially captured and tagged (N1) and then one day later 60 fish were D PA Example G E M2 = the number of individuals already marked in the second capture. Student Design Task N u m e r ac y bu i l d e r EC TE Estimating populations Work in small groups of about three students. Tasks should be allocated to each member of the group. Challenge R Estimate the size of a plant population in a local ecosystem. R Questioning and predicting N C O • Choose a suitable ecosystem in which to work. • Discuss any potential difficulties, for example, how to find (or estimate) the total area of the ecosystem. • Choose a suitable organism to survey – it could be an animal or a plant species. • Predict the approximate size of the population, if this is feasible. U Planning and conducting • Determine the equipment required and write a proposed method for the activity. Check this with your teacher. • Conduct the investigation, recording all results neatly and clearly. Processing, analysing and evaluating 1 Perform all necessary calculations and record them in an appropriate format. 2 Evaluate how your result agrees with the prediction you made before you conducted the investigation. Problem solving 3 Analyse your method. Is there anything you would change if performing this investigation again? 3.2 Changing populations 107 03_CRA_IS9_77563_TXT_LAY.indd 107 28/08/13 2:35 PM Communicating Write a full report of your investigation. Include the following: your initial questions, predictions and plans for the experiment; the method used to conduct the experiment; how the results were recorded and processed; the analysis and evaluation; and any references used. Each section should be clearly identified. Questions 3.2.1: Population dynamics Remember FS 1 Suggest a reason why populations are estimated rather than just counted. 2 Recall the name of a population survey that counts every individual. O 3 Identify the most suitable method for estimating the size of populations of: PR O a spinifex grass b periwinkles c blue-tongue lizards U N C O R R EC TE D PA G E 4 Justify your reasons for selecting the sampling techniques for each part question 3. Figure 3.36 How would you estimate the population of (a) spinifex (b) periwinkles (c) blue tongue lizards? Apply 5 Students on a field trip with a national park ranger set traps for a small nocturnal marsupial, Antechinus stuartii, in a heathland ecosystem. They capture 8 animals on the first night and mark them with white dots on their tails. Then they release them. On the second night they capture 10 animals, of which 4 are marked. a Calculate the estimation of the population size of Antechinus stuartii in this ecosystem. b Explain how the students could increase the accuracy of this investigation. Analyse and evaluate 6 Is a growth in population size always desirable? Discuss. 7 Suggest some factors that may affect the population growth of A. stuartii. 8 Outline the advantages and disadvantages of quadrat sampling. 108 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 108 28/08/13 2:35 PM Natural factors affecting populations EC R R O C N U Figure 3.37 Rabbit populations grow rapidly when conditions are right. FS Figure 3.38 Short-tailed shearwaters leave their burrows on Montague Island on the southern coast of New South Wales and fly to feeding grounds in the area of the Bering Sea during the northern summer. They return for breeding in late September. O G E PR O When the weather becomes colder, many birds and other animals migrate to areas with warmer temperatures, resulting in their population significantly decreasing in one environment and increasing in another. During the breeding season, usually spring, numbers of animals will increase as the next generation is born. Flowering plants are pollinated and form seeds that disperse (spread out) in the environment and later germinate. Presence or absence of organisms of other species TE All populations are limited in size by their carrying capacity. This is the maximum number of species members that the environment is able to support in terms of resources. As a population increases and gets close to its carrying capacity, some of the environmental resources will be significantly depleted. Competition for the resources will increase, because there simply isn’t enough food, water or shelter to go around if for so many individuals. Some organisms will either die or leave the area. Hence, the Seasonal changes PA Limiting resources population will stabilise (reach its maximum size). Only one resource needs to be limiting to restrict the size of a population. That resource may be nesting sites, a food or water source, physical space or light availability for plants, or many other examples. D What causes the changes to the births, deaths, emigration or immigration that may change a population size? The dynamic equilibrium of a population means there are continual small changes to the population size, but overall the total number of individuals remains roughly the same. New births and immigration into the area cause the population to increase, while deaths and emigration cause it to decrease. Significant or relatively long-term changes to population size are usually due to specific events. Many of these changes are natural, but others are caused by human intervention. Natural impacts on populations may include any of several different factors. Predators and competitors may decrease population numbers. Some organisms will be familiar with these species and have ways to avoid predation or increase their own ability to compete for resources. Introduced predators and competitors can have devastating effects on resident species. Organisms will need to adapt quickly to avoid predation (being preyed upon) and will have to ‘fight’ for resources. Disease The introduction of a disease into a population may have a major or minor impact on a species. The impact will be determined by the cause of the disease and the species’ ability to fight it. Like humans, prior exposure to a disease can enable organisms to launch a successful immune Figure 3.39 Small birds are vulnerable to the predatory activities of larger birds. The pied currawong preys on the nests of smaller birds along the eastern coast of Australia. Currawongs have a varied diet that includes berries, insects and small vertebrates (including small birds). Figure 3.40 The Tasmanian devil has become a victim of facial tumour disease, a very unusual type of cancer because it can be transferred from one animal to another. There has been an average 40% decrease in devil sightings across Tasmania, and a 90% decrease in the overmatter 3.2 Changing populations 109 03_CRA_IS9_77563_TXT_LAY.indd 109 28/08/13 2:35 PM FS O However, evidence of warming in the Arctic is mounting year on year – with serious consequences for biodiversity. One well-publicised impact of warming is the loss of habitat for species dependent on sea ice, such as polar bears. But this is only one change. Across the Arctic, many habitats that are considered critical for biodiversity, such as the tundra, have been disappearing over the last few decades. Launched to coincide with the 10th Meeting of the Parties to the Convention on Biological Diversity in Nagoya, Japan, the report, entitled Protecting Arctic Biodiversity: Strengths and limitations of environmental agreements, was researched by UNEP’s Polar Centre GRID-Arendal in Norway. The report underlines that although tried and tested solutions to the current biodiversity crisis in the Arctic exist in the region itself, important conservation gains will only be won if root causes originating outside the Arctic region are addressed. Achim Steiner, UN Under-Secretary General and UNEP Executive Director, said: ‘We are currently witnessing unprecedented change in the Arctic, which will have important and far-reaching PA Global action needed to conserve Arctic biodiversity PR O Extreme natural changes have varying population effects. For example, bushfires can produce ash containing minerals suitable for seed germination, and many E Literacy builder Extreme natural changes native Australian plant species need fire to release their seeds from the woody fruits. In both these cases, bushfire results in a population increase. If the fires occur too frequently, young plants can be destroyed before they can produce their own seeds. Animal populations can be severely reduced because they may be killed in bushfires or they may flee to other ecosystems. Drought affects all organisms, as water is a vital resource for life. Plant and animal populations will suffer as the availability of water reduces and competition for it significantly increases. Floods, earthquakes and all other natural disasters affect population sizes, usually reducing them significantly as individuals are killed outright, or the resulting loss of resources increases competition. G Figure 3.41 Banksia plants need fires with a frequency of about seven years to enable seeds to be released, germinate and produce small trees or bushes that can produce their own seeds. response. Completely new diseases are likely to have more of an effect on a population. Populations with little genetic variation (populations that are small or heavily interbred) tend to have similar resistance to disease. One new disease may have the ability to wipe out the entire population. The cheetahs in Africa are very vulnerable due to their small numbers and low genetic variation. This effect is also seen more locally with the Tasmanian devil and their low resistance to facial tumours. United Nations Environment Programme D Nagoya, Japan, 27 October 2010 U N C O R R Figure 3.42 Polar bears depend on sea ice for survival. EC TE The Arctic is experiencing some of the most rapid environmental changes on the planet. Whilst this presents enormous challenges for conserving biodiversity, it also offers opportunities for enhancing cooperation between nations and reforming environmental governance to meet the challenges of the 21st century, according to a report by the UN Environment Programme (UNEP). The Arctic contribution to global biodiversity is significant. Hundreds of migrating species (including 279 species of bird and the grey and humpback whales) travel long distances each year in order to take advantage of productive Arctic summers. 110 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 110 28/08/13 2:35 PM contaminants and habitat fragmentation, are essentially global in nature. Tackling these threats will require identifying international agreements that are relevant to biodiversity, but in new, unconventional ways. Questions FS 1 Discuss why changes in the Arctic region will have ‘far-reaching consequences … for the rest of the world’. PR O O 2 List the factors described in the article that affect population sizes in the Arctic. 3 Why is an international approach to the problem of biodiversity in the Arctic essential? E consequences not only for the region itself, but for the rest of the world.’ The rapid changes in the Arctic are perhaps the most striking example of how interconnected our world is, and how policies in one part of the world can severely affect the environment, biodiversity and livelihoods in another. The report finds that existing multilateral environmental agreements that include the Arctic region … might be effective against threats caused by local, national, or regional activities (mining and oil and gas exploitation, for example) if adequately implemented. This is because the fundamental threats to Arctic biodiversity, such as climate change, transboundary G Questions 3.2.2: Natural factors affecting populations 6 Explain why a population with low genetic diversity is more susceptible to disease than one with high diversity. EC TE 2 Identify a limiting resource for plants, other than water. Explain why this resource would limit the size of populations. PA 1 In relation to resources, explain what ‘limiting’ means. How does this differ from ‘limited’? numbers of Tasmanian devils. You may want to consider some interactions the Tasmanian devils have with predators and prey, as well as the environment. D Remember R 3 Identify at least two animals you know of (other than birds) that migrate due to seasons. O R 4 Using a specific example, recall how a bushfire might increase the size of a population. 8 Disease is a big threat to human populations. Can you identify any recent diseases that have had serious consequences? U N C Apply 5 Construct a flow diagram showing some of the consequences of reduced 7 Explain how seasonal changes and migration could be linked to changes in limiting resources. 3.2 Changing populations 111 03_CRA_IS9_77563_TXT_LAY.indd 111 28/08/13 2:35 PM Human factors affecting populations likely to result in significant changes to populations within ecosystems. Animals that previously lived in the habitat will migrate or die. Plant removal may reduce pollination of similar species in the area as well as reduce nesting sites for many animals. Pollution O O R R EC TE D PA G E At present, the human population is about seven billion and is predicted to rise to about nine billion by 2050. Humans have developed technologies that efficiently remove resources from the environment. Human activity has introduced many chemicals into ecosystems. Some chemicals can cause mutation and/or death of certain species and, in some cases, can result in the collapse of entire food webs. A common pollutant into waterways is fertiliser runoff. The excess nutrients in the water cause blue–green algal blooms – eutrophication. Although these microorganisms photosynthesise, once the bloom is over they die and decay, which removes dissolved oxygen from the water, starving all other aquatic organisms of oxygen. The microorganisms also grow across the surface of the water blocking sunlight from reaching photosynthetic organisms lower down in the water, preventing them from replenishing the oxygen in the water. Irrigation increases fertiliser runoff. On the east coast of Queensland, this runoff PR O Competition for resources FS While there are plenty of natural impacts on populations, the effect of human intervention is felt in many ecosystems to varying degrees. Humans can have a significant short-term or long-term impact on ecosystems and the wellbeing and survival of other species. Demand for food is increasing with the human population, which means more pressure on the natural resources of the land and sea. These resources may be needed by other species. For example, humans use a lot of water from the Murray–Darling Basin for agriculture, which seriously affects other species that depend on the river system. The river red gum forests that surround the Murray River have been placed under extreme stress during droughts. Permanent removal of habitats by humans to use the land for building or agriculture, or the trees for wood, is very U N C Figure 3.43 Numbers of Murray cod, and other native fish, have decreased significantly due to irrigation, overfishing and competition with introduced species. Some have been declared rare or endangered. Figure 3.44 Some substances in detergents and fertilisers on agricultural land have washed into oceans, lakes, river and other water bodies. This can lead to eutrophication – an increase in organisms that reduce oxygen levels in the water, harming other organisms. 112 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 112 28/08/13 2:35 PM FS also carries topsoil and silt into the ocean. Once in the ocean, the silt settles on top of the coral reef as ‘marine snow’, suffocating the coral polyps and blocking out the sun for their photosynthetic symbiotic algae. Coral growth is extremely slow, so the death of sections of the reef is devastating to the reef ecosystem. Many industries now have much more restrictive rules about the chemicals they can release into the environment. Figure 3.45 Botany Bay, near Sydney, was a natural ecosystem when James Cook first sailed into it in 1770. Today, it is an urban ecosystem because of many humaninduced changes. PR O E G PA D R R EC TE Increasing numbers of humans, increasing wealth and more sophisticated technology have resulted in large amounts of fossil fuels being used for transport, industry, agriculture and electricity. Burning of these fuels is contributing to the amount of carbon dioxide in the atmosphere and to the enhanced greenhouse effect. More carbon dioxide means more trapped heat, causing an overall average increase in the global temperature. But while some areas are getting hotter, others are getting colder. In some ecosystems, regular seasonal changes are becoming less predictable, and extreme weather events are occurring more often. Organisms that cannot adapt to these changes in their ecosystems will either emigrate or die. and camels are hardy animals well adapted to our arid climates, flourishing in the bush and outcompeting native grazers. However, not all effects of introduced species are negative. The increased pastureland for cattle and sheep has also increased grass for kangaroos and wallabies to eat, enabling native populations to increase in some ecosystems. Human homes and tips provide ample food and shelter for many bird species. The introduction of the cactus moth, Cactoblastis cactorum, was a successful application of biological control for the prickly pear cactus. Huge areas of pastureland were overgrown with the introduced cactus and nothing seemed to eat it. The prickly pear continued to reproduce and spread without a natural grazer until its natural predator, the cactus moth, was introduced. This moth lays its eggs on the cactus and the grubs that hatch eat it. The grubs don’t eat any native Australian plants and therefore do not harm any other plants. When the number of cactus plants reduced, the moths had nowhere to reproduce and so died off, causing no lasting negative impact on the ecosystem. Biological control is the carefully considered and planned introduction of species to an area to control the populations of a pest species. The pest species may be a native species with uncontrolled population growth, or it may be an introduced species like the prickly pear or cane toad. The introduced species does not need to be a nonnative – they may be native to the country, O Enhanced greenhouse effect O Introduced species U N C Humans have introduced many plant and animal species to Australia as a whole, but also to specific ecosystems. Foxes, rabbits, cat and dogs, cattle and other livestock, crop plants and decorative plants were all introduced for food, sport, familiarity or companionship. All of these new species compete with native species. New predators have devastated native populations that have not adapted to avoid them. The introduced cane toad is still spreading south, outcompeting many other toad and frog species, and poisoning potential native predators like quolls and owls. Feral goats overmatter 3.2 Changing populations 113 03_CRA_IS9_77563_TXT_LAY.indd 113 28/08/13 2:35 PM O PR O Figure 3.46 Davies waxflower is a critically endangered Australian plant. To protect the species, some of the areas where it is found have been fenced. One of the properties with the species even has a conservation covenant in place – an agreement between the landowner and the state government that permanently protects the nature conservation values of the property. Source: Australian Government, Department of Sustainability, Environment, Water, Population and Communities EC TE D PA G More than 60 Australian plant species are now thought to be extinct, and over 1180 are threatened. One of these is Davies’ waxflower. Davies’ waxflower (Phebalium daviesii) is a shrub or small tree that grows to about five metres. It is endemic to Tasmania – that is, it is found nowhere else in the world. It is known from only three sites along the George River near St Helens, on Tasmania’s east coast. The species was thought to be extinct until it was rediscovered in 1990. It grows in the flood zone close to the river in eucalypt woodland. Most specimens of Davies’ waxflower are on private land, next to pasture, and cleared land where cattle feed. Cattle cause problems of trampling, high nutrient levels and compacted soil. The species is also susceptible to root rot fungi, and any activities that involve movement of soil will increase the risk of infection. As part of the conservation strategy, and to promote community awareness, the Davies’ waxflower has been planted in St Helens and even in private gardens. FS Threatened Australian plants E Deeper u n d e r s ta n d i n g Questions 3.2.3: Human factors affecting populations R Remember R 1 Define the term ‘biological control’. U N C O 2 Describe an example of humans competing for resources with a native species. Apply 3 The greenhouse effect is the natural trapping of heat against the surface of the Earth by the atmosphere. Suggest what the enhanced greenhouse effect might be. 4 Currawongs are said to be opportunistic feeders, and tend to have large populations near where humans live. Currawongs also tend to compete with small birds for nesting sites and resources. Could it be said that the impact of currawongs on the populations of small birds is a human impact? Discuss your answer. 5 The fox is an introduced species in Australia. Outline what impact this animal has on native species. 6 Of the resources used by humans, which would you classify as ‘needs’ and which would you classify as ‘wants’? Explain your reasoning. 114 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 114 28/08/13 2:35 PM 7 Changing populations Ethical understanding 1 Identify some examples of how humans, especially since European settlement, have changed Australian ecosystems because of introduced species. [2 marks] 8 Do you consider your personal use of resources to be excessive? Do you try to reduce your use of resources? Do you think you should? Discuss. [3 marks] 5 Recall the term used to describe oxygen depletion in aquatic ecosystems due to algal blooms in response to excess nutrients. [1 mark] O PR O E TE Apply 10On a global scale, the main energy sources are oil (~35%), coal (~23%), natural gas (~21%), biomass and waste (~10%), nuclear (~6%) and hydro (~2%). Wind, solar and geothermal power together account for only 2%. Of all the sources, over 80% are based on fossil fuels. What do you think should be the focus of energy providers for the future? Should the people of Australia be involved in these decisions? Explain your answers. [5 marks] G 4 Suggest the characteristics of the organisms for which you would use quadrat sampling to estimate the population. [2 marks] Critical and creative thinking PA 3 Use a specific example to describe how seasonal changes cause changes in the size of populations in an ecosystem. [2 marks] 9 Many would argue, with respect to resource use, that one person cannot make a difference. Do you agree? Discuss. [3 marks] Checkpoint D 2 Describe some other significant ways in which humans have affected natural populations in ecosystems. [2 marks] 3.2 FS Remember and understand Making connections 11Select an environmental impact to investigate that is either natural or caused by humans. Imagine you are an environmental scientist. Design an experiment to test the level of impact and the timeframe in which it would occur. You do not need to be able to conduct this experiment. [5 marks] N C O R R EC 6 The glaciers on Mt Kilimanjaro are melting, as are many other glaciers. Less water in the nearby lake system affects the water cycle, causing less cloud coverage. This allows more sunlight to reach the glaciers. The increase in sunlight provides more energy for melting of the glaciers. Explain how cloud cover can affect the atmospheric temperature and hence the melting of glaciers. [3 marks] U Analyse and evaluate 7 The human population was fairly stable until about 1 ad. In the past century it has almost quadrupled. Evaluate the likely effects of population increase on world ecosystems. [2 marks] TOTAL MARKS [ /30] Changing populations 115 03_CRA_IS9_77563_TXT_LAY.indd 115 28/08/13 2:35 PM Evidence suggests that humans have lived in Australia for 60 000 years. Fossils and rock art have shown that natural and human-induced changes have occurred to natural ecosystems over that period. In contrast with the early European settlers, the Australian Aboriginals and Torres Strait Islanders understood the constraints of the environment, yet their understanding was not respected. Today, our way of life makes many competing demands on the natural environment. Indigenous knowledge as well as scientific understanding and technology are being used to try to appropriately manage sustainable ecosystems. O FS 3.3 Managing sustainable ecosystems PR O Aboriginal land management U N C O R R EC TE D PA G It is believed the name ‘Kakadu’ is derived from the local Aboriginal language Gagadju. The Gagadju-speaking Aborigines were believed to be that region’s original inhabitants about 50 000 years ago. Kakadu wetlands faced a problem after the removal of all feral Asian water buffalo in the 1980s. The buffalo kept the native grass mudja (Hymenachne acutigluma) in check, but after their removal it spread, choking out wetland plants, restricting the feeding of water birds, reducing the variety of habitats and limiting access for hunting and food gathering by Aboriginal people. The solution involved a return to traditional fire management practices. Mudja had not been a problem before the buffalo introduction because regular burning by Aboriginals had maintained biodiversity and supported their ability to hunt and gather food throughout the year. E Kakadu: burning for biodiversity Figure 3.47 The wetlands of Kakadu National Park in the Northern Territory are an ecosystem with very high biodiversity. 116 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 116 28/08/13 2:35 PM FS O season in December, the mudja is burnt. The result has been an outstanding success. Populations of turtles, magpie geese, other wetland birds and water lilies have increased. Plant variety such as wild rice and spike rushes and a greater variety of habitats, including more open water, now can be seen. Care is being taken to ensure the traditional knowledge is recognised, remembered and passed to the next generation. Figure 3.48 Carefully controlled burning of some ecosystems can prevent the over dominance of particular plant species to maintain high biodiversity and reduce the impact of natural bushfires. PA fills with water during high-rainfall years, due to excessive flow of fresh water from rivers in outback Queensland, it is virtually a freshwater lake. Native freshwater fish such as bream and golden perch can live in it until it becomes too salty due to evaporation. • Identify the abiotic factors in components of the ecosystem at Lake Eyre that affect populations. • Explain the word ‘sustainable’. • Could the lake ecosystem be described as a sustainable ecosystem? Discuss. b U N a C O R R EC TE D Lake Eyre is a massive lake that lies in a remote area of inland Australia. Most of the time, the lake is completely dry. Without water, a salt crust of nearly half a metre covers a quarter of the surface. Several major rivers empty into Lake Eyre but carry water only about once every ten years. When water does reach Lake Eyre, as occurred in late 2010, early 2011 and early 2012, large numbers of birds return to breed. The explosion in the populations of ibis, pelicans and other bird species in Lake Eyre in 2010–2012 has been striking. During droughts, Lake Eyre is a salt flat with few animals visible. When it G Activity 3.3.1: The extremes of Lake Eyre E PR O Traditional ecological knowledge has been combined with modern science to develop and monitor the solution. CSIRO and the Bushfire Cooperative Research Centre worked with a family of traditional owners in Kakadu as part of a northern Australian ‘Burning for Biodiversity’ project. The project applies Aboriginal fire management in the Boggy Plain floodplains of the South Alligator River and now also the well-known Yellow Water wetlands. Woodlands and paperbark forests that surround the grasslands are burnt progressively between May and August, early in the dry season. This ensures there is little fuel beyond the grasslands so later grass fires remain contained. From September to the beginning of the downpours of the wet Figure 3.49 Lake Eyre in (a) drought and (b) flood. 3.3 Managing sustainable ecosystems 117 03_CRA_IS9_77563_TXT_LAY.indd 117 28/08/13 2:35 PM FS PA G A series of rock wall constructions in the river at Brewarrina are part of Australia’s National Heritage and evidence of how the local Ngemba people understood their local environment including the water flows, fish migrations and movements. O Reliability of secondary source information is important. One way of ensuring reliability is to use a number of different information sources and check for consistency. It is also important to check the source of the information because not all Internet sources are accurate. Read the following information about fish traps and conduct your own research to validate it. Write a bibliography of the sources you use. You could present your findings as a table of facts identifying them as accurate, partially correct or incorrect, listing the sources you used to validate each one. Brewarrina Aboriginal fish traps They built stone walls, called Ngunnhu, in the shallows of the Barwon River in a complex arrangement. Some claim the walls that served to trap fish are 40 000 years old and, as such, would be the oldest remaining human-built structure. This area was, and remains, a significant Aboriginal meeting place. The use of the fish traps was managed to ensure responsibility for each trap and that overfishing did not occur. Other local tribes also benefited from the fish traps. Indigenous fish traps are also found in estuaries and along the coast. One of the most extensive systems is the collection of eel traps in the Mount William swamp and Lake Bolac of Victoria. The local Aboriginal tribes built an extensive network of channels, weirs and eel traps. Combined with their knowledge of eel migration, this allowed a ready supply of food sufficient to allow bartering, and semi-permanent settlement. PR O Research E Sc i e n c e skills TE D Uluru and Kata Tjuta: Reducing human impact U N C O R R EC Have you ever visited Uluru or Kata Tjuta (the Olgas)? This area contains one of the most significant arid land ecosystems in the world. It receives less than 250 millimetres of rainfall per year. Despite the harsh Figure 3.50 Puli habitat. climate, this area is home to hundreds of different organisms. When early European explorers first visited this region in the 1870s they were confronted by a harsh landscape. Their initial aim was to find a route for the overland telegraph line from Adelaide to the Top End, and to set up pastures for sheep and cattle grazing. They soon decided the region was unsuitable, and left. However, the traditional owners of the land, a group of Anangu Aboriginal people, had lived on this land for thousands of years and understood it well. They lived a nomadic life, travelling in small family groups and surviving by hunting wildlife and gathering food from the land. In this way they did not over-harvest the land and gave it plenty of time to recover between visits, ensuring there would always be enough resources for when they returned. These sustainable hunting and gathering practices meant people could successfully live in a very fragile and harsh ecosystem. The Anangu knew where to find food to survive and, more importantly, which 118 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 118 28/08/13 2:35 PM FS O PR O PA G E Figure 3.51 Puti habitat. U N C O R R EC TE D areas were best for hunting and gathering at different times of the year. The Anangu classified their environment to help them locate the precious food. They used these names: Puli: rocky areas, gorges, stony slopes. Animals come to this area to find shelter and water. Euros, fat-tailed antechinus, echidna and black-footed rock wallaby can be found here. Puti: open woodland. After the rains, this area has an abundance of grass, which the kangaroos eat. Honey ants build their nests in this area. Trees include mulga (a wattle), desert oak, desert poplar, desert bloodwood, river red gum and blue mallee. Wattle seed is an important food. Witchetty grubs live on the roots of the witchetty bush. Red kangaroo, euros and the spinifex hopping mouse are found here. Pila: spinifex plains, low areas between dunes. This is the best place to gather seeds to eat. There are over 50 species of desert grass. Many types produce seeds that are gathered and ground to make flat breads and damper. Resin is gathered from gummy or soft spinifex, and used for making and repairing hunting and working implements. Other habitats include the creek lines (karu) and sand dunes (tali). These become nyaru after fires. The Anangu also distinguished five seasons: Piriyakutu or piriya piriya (usually August–September) – A warm steady wind from the north and west (piriya) predominates. Animals, and plants such as the honey grevillea, reproduce. Reptiles become more active. Food is available and it is a good time for hunting kangaroos. Mai wiyaringkupai or kuli (around December) – This is the hottest season, when food is scarce. Storm clouds (ngankali or marutjara) build up, producing lightning but little rain. Bushfires started by lightning strikes occur. Itjanu or inuntji (January–March) – Overcast clouds (utawari) bring sporadic storms and food plants flower. Wanitjunkupayi (usually April–May) – The weather starts to turn cold and the Figure 3.52 Pila habitat. reptiles become less active. Tjuntalpa clouds start to occur around April but sit low over the hills until evening. They do not usually bring rain. Wari (June–July) – The cold season bringing morning frosts (nyinnga), and mist or dew (kulyar-kulyarpa) most mornings but little rain. The frosts dry and preserve the grasses as fuel for the fires ignited in the hot season. Introduced species have affected the Uluru–Kata Tjuta communities. Buffel grass was used to reduce erosion in some areas, but has spread and is now having a major effect on the diversity and distribution of overmatter 3.3 Managing sustainable ecosystems 119 03_CRA_IS9_77563_TXT_LAY.indd 119 28/08/13 2:35 PM Questions 3.3.1: Aboriginal land management Remember 1 Explain how traditional burning techniques were used in Kakadu. What benefit did it bring to the environment? 2 The early European explorers abandoned the arid ecosystem around Uluru and Kata Tjuta because they couldn’t survive. Explain why they struggled to find food there. Apply 4 Discuss Aboriginal land management in terms of: O a a nomadic existence FS 3 Recall the reason why mudja grass needed to be managed with fire. b use of fire PR O 5 In a group of four, create a list of the biotic factors and another list of the abiotic factors important to the ecosystems in Uluru–Kata Tjuta National Park. One pair can create the ‘biotic’ list and the other pair creates the ‘abiotic’ list. E 6 Suggest a reason why the Anangu people devised a system of classification for the natural habitats around them and the seasons they experienced. PA G Research 7 Follow the obook link to find out about the kind of environment the Anangu live in and foods they traditionally ate to survive. List at least five animals and five plants food sources. D 8 Research one example of how Aboriginal people have used their knowledge to conserve and manage their environment. U N C O R R EC TE 9 Research the general differences between Aboriginal land management systems and those of Europeans. Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 120 28/08/13 2:35 PM People in Australia expect a lifestyle that provides essential food, clothing and shelter, but also many additional comforts. Meeting these demands can damage natural ecosystems. Environmental sustainability is about balancing the way we live with its impact on ecosystems. For sustainable practices to begin and to continue, individuals, communities and governments need to work together. Table 3.5 includes the benefits and problems of some local strategies used to balance human activities and needs with conserving, protecting and maintaining the quality and sustainability of the environment. Table 3.5 Some local environment strategies. FS Sustainability and ecosystems Benefits Problems Recycling Materials such as aluminium can be recycled indefinitely with a fraction of the energy required to extract it from the ore. Some materials, such as paper, cannot be recycled indefinitely because of loss of quality. Recycling requires money, time and effort for collection, sorting and processing. ‘Organic’ agriculture Less fertiliser run-off and fewer beneficial insects killed by pesticides. Pesticides do not enter the food web and become more concentrated at the top consumers. Less productive and profitable for farmers. Higher prices for customers. Promoting alternatives to car transport Reduces the pollution from cars. Reduces use of fossil fuels. May require more infrastructure such as cycleways and train lines. Changing behaviour is not easy when alternatives to cars may be less convenient. Public cleanup activities such as Clean-up Australia Day Removes plastics and nonbiodegradable rubbish from ecosystems. Raises awareness. Requires energy and effort to coordinate and collect waste. Not as effective as producing less waste to begin with. Bush regeneration Allows native flora and fauna to reestablish in disturbed ecosystems. TE D PA G E PR O O Strategy EC Requires energy and effort to coordinate. R Activity 3.3.2: Science and sustainability U N C O R Choose one activity in your local area that aims to help maintain or create a sustainable environment. Assess the benefits and problems associated with the activity. Identify whether science or technology is playing a part in the activity. If so, explain how. Identify whether you as an individual can participate in the activity in some way. Present your findings in a format of your choice, but use one digital technology in your presentation. 3.3 Managing sustainable ecosystems 121 03_CRA_IS9_77563_TXT_LAY.indd 121 28/08/13 2:35 PM U N C O R R EC TE D FS PA G Around 100 Indigenous Working on Country rangers from across southern Australia have come together for the first time this week to share knowledge and experience in protecting our environment and conserving biodiversity. Rangers have had the opportunity to showcase their work, strengthen their skills in land and sea management, celebrate their achievements and help build sustainable communities. There are now almost 700 rangers supported under Working on Country around Australia and over 20 Working on Country ranger teams operating across southern Australia. This was the first regional gathering for Working on Country rangers and for most of them it will be the first time they have met. The conference, from 16 to 20 April 2012 at Calperum Station near Renmark in South Australia, is funded by Working on Country as part of the Caring for our Country initiative. The Australian Landscape Trust, which manages O 20 April 2012 Calperum and Taylorville Stations and supports the Working on Country Riverland Indigenous ranger team, is hosting the event. Workshops include Aboriginal site recording, media skills, fire management, quad bike safety, water quality monitoring and using new technology in landscape management. The Working on Country Indigenous ranger program is achieving environmental outcomes in the national interest and supporting the Australian Government’s commitment to Closing the Gap. Working on Country recognises Indigenous people’s strong relationship and obligations to country and their desire to have their land and sea management work recognised as paid employment. Vast areas of Australia are cared for by Indigenous people who deliver environmental services of benefit to the nation, including the management of cultural sites, heritage values, fire regimes, biodiversity, feral animals, weeds, land disturbance, pollution and climate change impacts. In this way, Working on Country brings together Indigenous caring for country, environmental and employment outcomes. PR O Working on Country Southern Ranger Conference E Literacy builder Source: Department of Sustainability, Environment, Water, Population and Communities Questions 1 How do you think sustainable communities of Indigenous ranger teams contribute to sustainable ecosystems in Australia? 2 Why are collaboration and communication important to ecosystem management? 3 What special skills would Indigenous rangers bring by caring for cultural and heritage values? Figure 3.53 Working on Country integrates Indigenous knowledge and practice with nationally accredited qualifications to deliver positive environmental outcomes. 122 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 122 28/08/13 2:36 PM Rio+20: UN Conference on Sustainable Development PR O O FS The United Nations Conference on Sustainable Development, known as Rio+20, was held in Rio de Janeiro, Brazil, in June 2012. It followed on from the Earth Summit held 20 years earlier in Rio. Governments and organisations from many countries met to discuss ways to reduce poverty while at the same time using resources in a fair and sustainable way. Some of the priorities for the conference were energy, water and sustainable cities and agriculture. The conference participants recognised that ending poverty, changing the amount we produce and consume, and protecting the natural environment are all essential for sustainability. Developing countries need support to find a ‘green’ path for development, and cooperation and organisation between countries are very important for sustainable development. There is concern among environmental groups that the outcomes of the conference will not be committed to and may not happen soon enough. Questions 3.3.2: Sustainability and ecosystems Remember 1 Define ‘environmental sustainability’. PA 4 Identify the purpose of the Rio+20 conference. G 3 Recall an advantage of bush regeneration. E 2 Recall why paper cannot be indefinitely recycled. D Apply 5 Describe two ways in which human activities conflict with sustainability and ecosystems. Which is more important? TE 6 Outline some examples of ways that you personally can help maintain a sustainable environment. 7 Are sustainability and modern life compatible? Discuss. EC 8 Describe how local and global activities both contribute to sustainability. R R Research 9 Research permaculture and compare it to the large-scale growing of single crops (monoculture). O 10Investigate one recommendation of the Rio+20: UN Conference on Sustainable Development. U N C 11 Managing sustainable ecosystems 123 03_CRA_IS9_77563_TXT_LAY.indd 123 28/08/13 2:36 PM 12 2 Explain why biodiversity is important to the traditional landowners of Kakadu. [2 marks] 3 Recall the main characteristic the Anangu people used to distinguished the different habitats in their ecosystem. [1 mark] Apply Ethical understanding 11Imagine you are part of an Aboriginal group that has developed a system of fish traps on an inland waterway. Describe the rules you would need to establish to ensure the benefits of the traps were fair. [2 marks] 12Explain why it is important to manage ecosystems sustainably. [2 marks] PA G 4 Imagine you are lost in the arid Australian outback. Identify the main abiotic factors that would make your survival difficult. [2 marks] FS 1 Identify one benefit that water buffalo had on the Kakadu wetlands. [1 mark] 10To determine the size of your ecological footprint, you need to consider how much meat is included in your diet. Explain how the amount of meat you consume is related to your ecological footprint. [2 marks] O Remember and understand PR O Checkpoint E 3.3 Managing sustainable ecosystems TE D 5 Outline three changes you could make to your lifestyle to minimise your impact on Australian ecosystems. [3 marks] EC 6 Compare the abiotic components of the Kakadu wetlands with the ecosystems around Uluru. [3 marks] R Analyse and evaluate U N C O R 7 You read a report on the Internet that claims regular burning of the alpine herbfields increases the biodiversity in these ecosystems. Describe the evidence you would need to validate these claims. [2 marks] 8 Outline what you think is the worst mistake for Australian ecosystems in the past 200 years. Justify your choice. [2 marks] 9 Evaluate the benefits of using fire management over reintroducing water buffalo to Kakadu wetlands. [3 marks] Critical and creative thinking 13Create a poster that describes the components of an ecosystem that would provide adequate food for a large population of humans throughout the year. [5 marks] 14You are to develop a new event to promote awareness of the need to live more sustainably. Name the event and develop a slogan to attract interest and highlight the key message. [2 marks] Making connections 15Seed banks are an important way of preserving plant species at risk of decreasing populations or of extinction. Research the setting up and maintenance of seed banks. How might seed banks contribute to sustainable ecosystems and to biodiversity? [3 marks] TOTAL MARKS [ /35] 124 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 124 28/08/13 2:36 PM 1 Fill in the gaps using the words in the Word Bank below: Ecosystems are made up of __________ abiotic factors, __________ biotic factors and the interactions between them. __________ factors, like wind speed or water temperature, determine which __________ can survive in that ecosystem. All the different species living in the ecosystem make up the __________. 3 FS Some critical abiotic factors of most ecosystems include the availability of ____________, oxygen and nitrogen. These elements are maintained in an ecosystem through the cycling of ____________. Carbon and ____________ are moved through the cycle by two main opposing processes; ____________ and photosynthesis. Bacteria in the soil ‘fixes’ ____________ into a usable compound, while the decay of organic matter releases it back into the atmosphere. PR O O ____________ cannot be recycled through an ecosystem, but is passed from organism to organisms, usually through food webs, with the majority being lost to the ecosystem in the form of heat. ____________ is vital for converting solar energy into the chemical energy stored in ____________ molecules, which can then be used by most organisms. review G Carbon Community Living Management Matter Organisms Oxygen Photosynthesis D Sustainable Energy Glucose Nitrogen Non-living Population Respiration PA Abiotic TE Word bank E Changes to abiotic or biotic factors can affect a ____________. Human intervention can have positive or negative effects on ecosystems. Indigenous land ____________ practices, such as regular burning, are being reintroduced to successfully manage ____________ ecosystems. Chapter R EC Recall that ecosystems consist of interdependent biotic communities and abiotic components of their environment C O R 2 Identify three abiotic features of a terrestrial ecosystem and three abiotic features of an aquatic ecosystem. [3 marks] U N 3 Identify a way in which living things change the abiotic factors in their environment. [1 mark] 4 Outline the major biotic and abiotic factors that influence the size of the human population. [2 marks] 5 Evaluate the ways in which an ecosystem is similar to a school. [2 marks] Outline how matter such as nitrogen, carbon and oxygen, is cycled through ecosystems 6 Explain the role of decomposers in ecosystems. [1 mark] 7 Explain why the cycling of oxygen and carbon are so closely linked. [1 mark] 8 Compare and contrast the cycle of matter with the flow of energy through an ecosystem. [2 marks] Describe how energy flows through ecosystems via food webs 9 Identify and explain the main process that results in energy being available to communities. [3 marks] 10Outline how food webs are linked to the flow of energy through ecosystems. [2 marks] 2 Managing sustainable ecosystems chapter review 125 03_CRA_IS9_77563_TXT_LAY.indd 125 28/08/13 2:36 PM 3 REVIEW CHAPTER 11A bushfire burns most of the grass away, but the gum and wattle trees survive and quickly sprout new leaves. Use the food web in Figure 3.54 to answer the following questions: c Identify the type of competition experienced by kangaroos, wombats and crickets. [1 mark] d Evaluate whether the loss of grass will affect the gum and wattle trees. Explain your decision. [2 marks] a Predict the initial change to the cricket population. How will this impact the kookaburra population? [2 marks] PR O O FS b Evaluate whether the loss of grass will affect the dingo population. Explain your decision. [2 marks] Dingos E Echidnas G Termites PA Frill–necked lizards Wombats D Kangaroos Wattle trees Grasses EC Figure 3.54 An Australian food web. O R R Analyse how changes in biotic and abiotic components of an ecosystem affect populations of organisms 12Compare the population changes likely to occur because of an introduced herbivore (such as a rabbit) with an introduced carnivore (such as a fox). [2 marks] 13Describe the method of an investigation that could determine whether the spread of cane toads through the Kakadu wetlands is affecting biodiversity. [5 marks] C N U Crickets TE Eucalyptus tree Kookaburras 14Using a specific example, explain how a change in an abiotic factor can affect the population size of a particular species. [2 marks] 15Investigate how models can be used to predict changes in populations due to environmental changes like natural disasters or the introduction of disease. [5 marks] Research how Aboriginal and Torres Strait Islanders use their knowledge to conserve and manage their environment 16Identify one land use practice of Australian Aboriginal or Torres Strait Islanders that has helped manage local ecosystems yet meet human needs. [1 mark] 126 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 126 28/08/13 2:36 PM Biological control Ecological footprint G Scientists use modelling to calculate the area of land needed to produce all the resources you use and dispose of all your wastes. What lifestyle factors do they consider when constructing these models? What things can you do to reduce your carbon footprint? R R EC TE D Australian native plants and animals adapted to life on an isolated continent over millions of years. Since European settlement, native animals had to compete with a range of introduced animals for food, habitat and shelter. Some native species also had to face new predators. Rapid changes in land use, such as increased crop growing areas, affected soils and waterways. Research the meaning of the term ‘biological control’. Find some more Australian examples of successful and not-sosuccessful examples of biological control. E PR O by building an ark. The Frozen Ark Project is a modern-day project named after this story. What is the Frozen Ark Project? What are its goals? How is it working towards achieving them? PA Research Choose one of the following topics for a research project. Some questions have been included to help you begin your research. Present your report in a format of your own choosing. O Frozen Ark Project Wildlife crossings A variety of strategies have been implemented around Australia to reduce wildlife road deaths and assist animals to cross safely. What are overpasses? What are underpasses? What types of animals would use each? How effective are they at reducing road deaths? Have other strategies been implemented? Which is the most effective? U Reflect N C In the story of the floods in the Bible, Noah protected and conserved animals Key words adaptation adenosine triphosphate (ATP) autotrophs balance biodiversity biogeochemical cycle capture–recapture cellular respiration chloroplasts commensalism competition denitrifying bacteria decomposers dynamic equilibrium ecosystem enhanced greenhouse effect eutrophication heterotrophs intraspecific interdependence interspecific line transect mutualism nitrogen fixers parasitism photosynthesis population population dynamics predator–prey quadrats starch sustainability symbiosis respiration work O 21Do you think modern technology has made it easier or harder to live sustainably? Explain. [3 marks] TOTAL MARKS [ /50] FS 19Explain why it is far more difficult to maintain a sustainable lifestyle over a longer period of time than for a short interval. [2 marks] 20Explain how you think a belief system contributes to the way people manage their ecosystems. [2 marks] Evaluate some examples of strategies used to balance human activities and needs in ecosystems with conserving, protecting and 3 REVIEW CHAPTER maintaining the quality and sustainability of the environment 17Indigenous people in Kakadu and around Uluru use burning to manage their ecosystems. Analyse the benefits and risks of using deliberately lit fires in ecosystem management. [2 marks] 18Evaluate the benefits of the Working on Country program. [2 marks] Me My world 1 What new science skills have you learned or improved on in this chapter? 2 What was the most surprising thing that you found about the flow of energy and matter in ecosystems? 4 Why is it important to understand the role of energy in ecosystems? 5 Why is it important to appreciate the interdependence of organisms in an ecosystem? 3 What were the most difficult aspects of this topic? My future 6 Why is the way humans interact with overmatter 3 chapter review 127 03_CRA_IS9_77563_TXT_LAY.indd 127 28/08/13 2:36 PM O FS 3 PR O MAKING C O NNE C T I O NS PA Field trip G E Figure 3.55 C O R R EC TE D The abiotic features of the environment determine the vegetation in an ecosystem. The vegetation, as the basis of most food webs, then determines which other species can survive there. Choose an ecosystem such as a woodland, grassland or rainforest. After a short study of the vegetation, measure the abiotic factors and make a conclusion about how they determine the type and height of the vegetation. You will need the following materials and equipment: U N • thermometer (for temperature) • wet/dry thermometer (for humidity) • anemometer (for wind speed) • light meter (for light) • rod (for measuring soil depth) • cobalt chloride paper (for soil moisture) • pH paper (for soil pH) 1 Observe the plants around you. Describe what you see. You could take photos, draw diagrams or write descriptions. 2 Examine the leaves of the plants. List three of their characteristics and give a reason why the leaves possess this feature. 3 Choose one species of plant. Record its common name, its scientific name and if possible the family of plants to which it belongs. Sketch a leaf of this plant or take detailed photographs. 4 Describe how your chosen plant is adapted to the conditions in the ecosystem. 5 Measure the abiotic factors shown in Table 3.6 for your chosen ecosystem. 128 Oxford Insight SCIENCE 9 Australian Curriculum for NSW Stage 4 03_CRA_IS9_77563_TXT_LAY.indd 128 28/08/13 2:36 PM 6 For each observation and measurement you made, analyse and evaluate its significance. It might be appropriate to research and analyse the history of the area you are studying. Table 3.6 Abiotic factors in an ecosystem. Abiotic factor Reading Temperature Wind speed Humidity Light intensity 7 What conclusion can you make about the effects of the abiotic factors that you have measured on the vegetation in this ecosystem? Soil depth Soil colour Soil moisture TE D PA G E PR O O FS Soil pH U N C O R R EC Figure 3.56 Figure 3.57 3 making connections 129 03_CRA_IS9_77563_TXT_LAY.indd 129 28/08/13 2:36 PM