Biology – Module 1 – A Local Ecosystem The distribution, diversity and numbers of plants and animals found in ecosystems are determined by biotic and abiotic factors. Compare the abiotic characteristics of aquatic and terrestrial environments. An aquatic environment is one that consists in water.
The abiotic characteristics of an aquatic environment include: Buoyancy – This refers to the upward pressure (or thrust) that is applied on the organism by its medium. Buoyancy is determined by the density of the medium and determines the floating ability of an organism. Water provides sufficient buoyancy for many organisms, e.g., the jellyfish. If a jellyfish is taken out of water and placed on land it will disintegrate by spreading apart. Thus, the water provides enough buoyancy (pressure) in order to keep the shape of the jellyfish. Pressure – This is the downward force that is applied on an organism by its medium. In water, the pressure is dependent on the depth. Organisms that live at the bottom of the ocean experience the effects of extreme pressure and they must have specific adaptations that enable them to survive in such harsh environments. Temperature Variations – Usually in an aquatic environment there are minimal temperature variations to that compared with terrestrial environments. The temperature variations also depend on the size of the body of water; a large body of water will experience much less temperature variations than a smaller body of water. Also, as depth increases the temperature of the water decreases. Availability of gases – in water the availability of gases depends on factors such as temperature, depth and turbulence. Hot water holds much less oxygen than cold water. The availability of gases also depends on the rate of diffusion which is much slower in water than it is in air. Also, as the depth of the water decreases the availability of the gases decreases. Availability of water – In aquatic environments water availability can be a problem as osmosis occurs. Organisms are suited to a particular type of water – either fresh water or salt water. If the organism is placed in the wrong type of water they will die, thus water-availability is an issue. In this scenario, the salinity of the water is another factor.

Light penetration – Light is only able to penetrate about 100m in oceans and seas. Thus as the depth increases the light penetration decreases. Light is essential for all aquatic plants, thus the plants needed to have specific adaptations that allow them to retrieve enough sunlight to survive? The light penetration is also dependent upon water clarity. Exposures to natural forces – Different aquatic environments are exposed to different natural forces such as tides, currents, waves etc. Marine organisms must be adapted to survive in such conditions.
A terrestrial environment is one that consists on land.
The characteristics of a terrestrial environment include: Temperature – There are much larger temperature variations on land rather than in water. Land organisms must therefore have adaptations to cope with such large temperature changes. Landscape position – Slope and aspect may affect temperature, water and light availability as well as impact on soil quality. Run-off and erosion may also be prominent in particular landscapes. Rainfall and water availability – Water is not freely abundant in land. It must be sourced from the soil or consumed. Organisms must have adaptations that allow them to survive using the amount of water available to them Salinity – Different soils have different salinity levels and only particular organisms thrive in certain salinity levels. Plants must have adaptations that enable them to cope with the different levels of salinity. PH (acidity/alkalinity) – Soil pH can vary. Dissolved salts play an important role in determining the pH of the soil and some plants need to have a particular pH to survive. Plants need to have adaptations that allow them to cope with the pH of the soil in their environment. Buoyancy – Air provides minimal buoyancy and therefore land organisms need to have a skeletal and muscle structures that enable them to support them. Exposure to natural forces – Wind, rain, floods, droughts, monsoons, cyclones, storms etc. are all part of the terrestrial environment and organisms need to be able to adapt to most if not all of these forces.

Identify the factors determining the distribution and abundance of a species in each environment.
Distribution – refers to the region where an organism is found.
Abundance – refers to the number of individuals in the area and is usually described as a density.
Aquatic - There are several abiotic factors that affect abundance and distribution of organisms in aquatic environments including: Pressure Variations – ranging from low pressures in surface waters to extreme pressure in deep ocean trenches. Light penetration – plants need adequate light for photosynthesis. This is true in both environments (aquatic and terrestrial). In water the light is only able to penetrate to a certain depth. Water doesn’t absorb all light. About 30% is reflected off the surface. At certain depths water absorbs different wavelengths (what we see as colours). Water absorbs the wavelengths that a majority of plants use for photosynthesis extremely quickly. This means that as the depth increases not only does the light penetration decrease, the quality of the light decreases as well. The salt concentration of the water – Marine organisms are suited to a specific type of water (ranging from the extremely salty Dead Sea to freshwater which has almost no salt) and if they were to be placed outside this they would die (due to osmosis) Temperature – The range of temperature is important as well because organisms prefer to live in certain temperatures ranging from hot springs through warm tropical seas to freezing Antarctic oceans. Gas Availability – This ranges from small amounts of gas available in warmer waters to plentiful amounts of gas in turbulent waters of oceans and cold streams
Terrestrial – There are several abiotic factors that affect abundance and distribution of organisms in aquatic environments including: Temperature – Most organisms prefer to live between 0 – 45 degrees Soil composition – Many species only prefer specific soil types. Rainfall patterns – Many organisms will only live in areas where the rainfall is specific to their needs. If the organisms prefer high rainfall and humidity it will live in areas where these conditions are prominent. Altitude – increasing altitude results in colder temperatures, reduced rainfall and decreased pressure which are specific factors that affect the abundance and distribution of the organism. Availability of salts – in the soil there must be specific salts for the plants. Plants will only thrive if there are those specific salts available.
There are also other factors that affect distribution and abundance of both aquatic and terrestrial organisms including: Availability of resources and Limiting factors – A limiting factor is a single resource that determines the maximum population of a specific species in that area. In aquatic environments this could be factors such as food resources. The amount of food available will determine the abundance of the organism in that environment. Competition – Competition for resources from both the same species and other species for specific resources can alter the abundance and distribution of that aquatic organism in that particular environment. Predation – This is when one organism consumes another. If a species has numerous predators in its environment, its abundance and distribution will fluctuate. Ability to mate – This refers to the organisms ability to reproduce efficiently. If the organism reproduces extremely quickly its distribution and abundance are likely to rise dramatically whereas if it was the opposite the distribution and abundance will remain steady. Chemical Factors – such as pH of the soil Dynamic Factors – such as wind speed and patterns, wave action. These are natural factors that will affect the organism and its environment. Describe the roles of photosynthesis and respiration in ecosystems
Photosynthesis is the process by which plants take carbon dioxide and water and with the use of sunlight convert it into glucose and oxygen.
6H2O + 6CO2 Light C6H12O6 + 6O2
Photosynthesis is significant in any ecosystem because it produces the chemical energy needed for all ecosystems to survive. The ultimate source of all energy on Earth is the sun. Plants use chlorophyll to capture some of the suns energy in photosynthesis. This is vital because this energy is then able to flow through the ecosystem for survival. Thus the ecosystem depends on plants conducting photosynthesis.
The overall role of photosynthesis is to provide energy for all other organisms in the ecosystem. The plants conduct photosynthesis to store energy. The plant gets eaten by an animal and part of the stored energy (about 10%) is passed on to the animal and so on. In ecosystems there is no re-use of energy. It is either used by the living thing or lost as heat. Because of this, a continual input of energy is required to keep living systems functioning and that is the ultimate role of photosynthesis.
Respiration takes place in the mitochondria of all living cells and results in the release of energy for organisms to use. Glucose if broken down in the presence of oxygen to produce carbon dioxide and water and in doing so energy is released. Energy in the form of ATP (adenosine tri-phosphate) is released as heat from this process and is used for cell functions such as growth, repair and maintenance.
The role of respiration is to remove oxygen from the air, return carbon dioxide to the air and provide energy for the organism. Thus, organisms respire in order to carry out daily activities. The role of respiration is to use the stored energy within an organism to carry out its daily functions. Without respiration, an ecosystem wouldn’t function as none of the organisms would be able to use the energy they had stored which means they would die.
•identify uses of energy by organisms
Majority of the energy in an ecosystem is lost as heat which is beneficial to most organisms as the cells and enzymes thrive under warm conditions.
Organisms use energy for many purposes including: Synthesis of complex molecules such as proteins, lipids, carbohydrates and nucleic acids. Growth involving the division, elongation and differentiation of cells Repair and maintenance of damaged or old cells Active transport of materials across cell membranes Functioning of special cells that need extra energy, such as nerves, muscles, liver etc. Transport of materials within organisms such as in the circulatory systems of animals Other daily activities such as movement, making sound, producing heat and producing light (called bioluminescence). Each local aquatic or terrestrial ecosystem is unique. Examine trends in population estimates for some plant and animal species within an ecosystem.
Transects can be used to determine the distribution of an organism.
Transects - A transect is a narrow strip that crosses the entire area being studied, from one side to the other. Transects provide an accurate and easy method of representing an area. Plants are usually the subjects of transects, but the distribution of extremely slow or non-moving animals can still be calculated. There are two types of transects - plan sketch and profile sketch. A plan sketch is an aerial or surface view of a representative area within an ecosystem. A profile sketch is a side-on view of an area showing to scale the distribution of organisms along a line.
There are numerous ways of estimating populations through the use of sampling techniques. These techniques are used if it is too difficult to count the exact number of species or if only a round estimate is sufficient.
Quadrats - It is much easier to calculate the abundance or population of plant species because they the stay in the one place. Quadrats are squares (the size of which depends on the organism - the larger the organism the larger the quadrat) which are randomly placed in the area that is being studied. The number of organisms within the quadrat is counted and this can be used to determine the percentage cover of the organism within that area. For example, if the abundance of grass was calculated to 54% of the total area. And it was known that approximately 1000 blades of grass covered 1 square metre and the total area was 10 meters squared, the population of the grass could be estimated to be approximately 5400.
Capture-Mark-Recapture – This is a method which involves catching a certain number of individuals of a particular species, marking or tagging them in some way. They are then released into the wild and then at a later time a group of the same species is caught and the number that was already tagged is recorded. This is then repeated numerous times. This method is appropriate for mobile organism where it is virtually impossible to count all individuals at one time.

The formula used to estimate the population goes as follows:

Number Captured X Number Recaptured------------------------------------------------------
Number Marked in the recapture

Sampling Technique | Advantages | Disadvantages | Transects | - Provides a quick, easy and inexpensive method for measuring species occurrence. - Minimal Disturbance to the environment | - Only suitable for plants or slow moving animals - Species occurring in low numbers may be missed. | Quadrat | - Easy and inexpensive - Minimal disturbance to the environment - Can also be used to determine distribution | - Only suitable for plants or slow moving animals. | Capture-Mark- Recapture | - Simple method that provides an estimate of abundance for animals in large populations that is difficult to count. | - Only suitable for mobile animals - Time consuming - Can be disturbing to the environment |

Outline factors that affect numbers in predator and prey populations in the area studied.
A relationship in which one organism eats another is called predator/prey relationship, or predation. These types of relationships often have a major impact on the abundance of organisms. Populations of predator are dependent on the population of the prey and vice versa.
For example, if the population of the prey were to drop significantly then the same trend could be seen in the predator population. On the other hand, if the predator population were to drop significantly then a huge increase in prey may be observed.
Such obvious relationships are seldom observed under natural conditions because many variables interact to influence the abundance of both predators and prey. In particular, where predators have a variety of food sources, such simple patterns are not observed.
A number of other factors could influence predator/prey populations as well: Size of ecosystem – The larger the ecosystem; the more resources Diseases Availability of food – for both the predator and the prey. Migration – This could result in fluctuations in both populations Reproduction – for both the predator and the prey Competition for resources – for both the predator and the prey Human activity and intervention could have an effect on either or both of the populations. Identify examples of allelopathy, parasitism, mutualism and commensalism in an ecosystem and the role of organisms in each type of relationship.
Allelopathy – This is the process by which plants are able to produce allelochemicals (also called biomolecules) which they release into the environment. These allelochemicals inhibit the growth of other plants in the area surrounding the plant, thus reducing competition for the plant, which increases the chances for the plants survival. Not all plants have allopathic tendencies. Since space is crucial to the survival of plants, those that are able to produce effective allelochemicals are extremely advantaged. Since the fewer the plants around, the more water the plant can absorb from the soil, and more soil for stability and more sunlight to absorb.
Examples of allelopathy: Eucalyptus leaf litter – Eucalyptus trees’ foliage are able to produce effective allelochemicals. When the leaves of the eucalyptus tree fall onto the ground, they decompose. During the decomposition of the leaves, the allelochemicals (in the form of acid) are released into the soil and these inhibit the growth of other plants in that area. Sorghum species (cereal grass) release a chemical in the root exudates that disrupts mitochondrial functions and inhibits photosynthesis. Symbiosis: Term used for interactions in which two organisms live together in a close relationship that is beneficial to at least one of them.
There are three types of symbiotic relationships:
Parasitism – This is where one species benefits whereas the other is harmed. A parasite obtains food and shelter from the host organism. They feed on the tissues or fluid of the host but do not usually kill it, as this would destroy the parasites food supply. Ectoparasites are those that live outside the body of the host, whereas endoparasites live internally.
Examples of Parasitism: Tapeworms live attached to the lining of the digestive system of their host animal and absorb digested food without causing any serious harm; however, the animal does become weaker and slightly sick. Ticks and fleas feed off the blood of dogs. They are benefiting whereas the dog is being harmed and it tries to scratch them to get rid of them. Fleas/ticks may result in the dog becoming extremely ill and even death.
Mutualism – this is where both the organisms in the relationship benefit.
Examples of Mutualism: The relationship between the anemone and the clown fish (also known as the anemone fish). The clown fish attracts prey to the anemone and as the prey approaches they are stung by the tentacles of the anemone. This thus provided food for the anemone. The clown fish feeds on the remains of the prey and it receives protection from predators and also food. The anemone is able to obtain its feed this way as well as be cleaned by the clown fish. Thus it is mutualistic. Note: the clown fish becomes immune to anemone’s sting by brushing itself on the tentacles. The ‘ant plant’ has a mutualistic relationship with a species of ant. The plant has a swollen bas in which the ants are able to build their colony. The ants carry corpses and excreta to parts of the chambers within the plant. This allows the plant to absorb the waste nutrients. Commensalism – This is where one species benefits and the other are unaffected.
Examples of Commensalism: The relationship between the remora fish and the shark. The remora fish attaches itself to the shark and thus is able to get a free ride and feed from scraps from the shark’s food but appears not to benefit the shark.

Barnacles and whales. Barnacles attach themselves to the surface of the whale. They are able to be transported to diverse areas rich in food. The whale however is unaffected. Describe the role of decomposers in ecosystems.
Decomposers, or SAPROPHYTES, are organisms that obtain energy by breaking down the dead bodies of other organisms or their wastes (e.g. faeces). Decomposers return nutrients into the soil so that they can be re-used. Their role is to recycle matter within an ecosystem. Decomposers include organisms such as fungi and bacteria.
Decomposers are vital to the functioning of an ecosystem. They play a crucial role in recycling materials. Since to amount of matter on Earth is finite, the materials in dead bodies need to be released so that new organisms can use these materials for growth, repair and maintenance. Decomposers are consumers and are mainly bacteria or fungi. Explain trophic interactions between organisms in an ecosystem using food chains, food webs and pyramids of biomass and energy.
A trophic interaction is one where one organism is consumed by another.
A Producer is also known as an autotroph.
A consumer is also known as a heterotroph.
Food Chain – Is a single chain of feeding patterns. It shows a liner process in which organism is consequently consumed by another in increasing trophic order.
Food Web – This is the combination and interaction of numerous food chains and shows the interactions and feeding patterns of numerous organisms. It is non-linear and one organism can be in many different trophic levels depending on the chain/web. A food web and a food chain also show the flow of energy and matter in an ecosystem.
Biomass pyramid – A biomass pyramid indicates the relative amount of matter in the organisms of a community. The total amount of mass in a community is called its biomass. In a self-sustaining ecosystem, the biomass significantly decreases at each trophic level. The normal pattern of a biomass pyramid has a huge percentage of producers, a limited percentage of herbivores and a small percentage of carnivores. Biomass pyramids show the amount of matter at each trophic level. These when used with food webs are best used to describe the energy and matter transfer through a community.
Energy pyramid – Energy pyramids show the amount of energy at each trophic level in a community. The lower the organism on a food chain the more energy it has available to it. Energy pyramids indicate the relative amount of energy transferred from one trophic level to another. In a stable community, biomass and energy pyramids decrease rapidly as the trophic level increases. Biomass and energy pyramids can be used to predict and explain changes in a community. Define the term adaptation and discuss the problems associated with inferring characteristics of organisms as adaptations for living in a particular habitat.
Adaptations are inherited characteristics of organisms that increase the chance of survival of the species. Adaptations are also often described as characteristics of organisms that are suited to the organisms’ habitats.
Adaptations can either be structural, behavioural or physiological. Structural adaptations are the physical characteristics (anatomy) of the organism to help it survive (e.g. for a spider, its eight legs is an adaptation because it allows for agile, nimble movement). Behavioural adaptation is the way an organism will act that increases its chance of survival. (E.g. when you wear a jumper because it is cold outside).

A physiological adaptation is one that is related to the internal functioning of the organism (e.g. a kangaroo will be able to produce two types of milk for its joeys which are of different ages).
It is sometimes difficult to infer that the characteristic of an organism is an adaptation to its particular habitat because: The organism may be observed outside the habitat in which it evolved, for example, in a suburban garden. The characteristic may provide no particular advantage in a particular habitat but has been inherited from ancestral organisms that inhabited different habitats. It may simply be difficult to be certain how a particular characteristic helps a species to survive. Identify some adaptations of living things to factors in their environment.
Animal adaptations – Spider: 8 legs (structural adaptation). Ability to produce web (physiological adaptation). Crawl away from any points of bright light (behavioural adaptation).
Plant adaptations – Old man Banksias: Huge Flower, thick bark, extremely fine intricate roots (structural). Seeds falling to the ground after a fire (physiological).
Note: An ideal environment for a plant is usually the environment to which an organism is adapted even when the environment might seem harsh to us. Describe and explain the short-term and long-term consequences on the ecosystem of species competing for resources.
When in competition two organisms use one or more resources in common, such as food, shelter and mates. The competition is so the organism can acquire a limited factor in the environment. Organisms may compete with members of their own species or members of other species. Competition between members of the same species is known as intraspecific competition. Competition between members of different species is called interspecific competition. Usually interspecific competition is less intense than intraspecific.
There are two types of competition: Resource competition – where the organisms utilize a resource that is in
Short supply Interference competition – where the organisms harm each other while obtaining a resource, even if that is not in limited supply.
Short-term consequences of competition: If the competition is intraspecific then it will result in the reduction in abundance of that organism. If the competition is interspecific it will result in the reduction of abundance for at least one of the organisms Also, if the competition is interspecific it will alter the distribution patterns of the organism which can result in a chain of consequences especially if the organism disappears from some areas where they are essential. This could greatly alter the natural chain and cause problems.
Long-term consequences of competition: If the competition is intraspecific it could result in some organisms in the species starting to act in ways that are different to the normal. E.g. find a different source of food. This could eventually lead to the creation of a new species that is unable to reproduce with their ancestral species. If the competition is interspecific it could result in the extinction of one species from that area which could alter food chains especially if the extinct organism was the only food supply of other organisms. It could lead to a chain of terrible consequences. On the other hand, other species might flourish due to this and this may improve the ecosystem. Identify the impact of humans in the ecosystem studied.
Humans impact ecosystems in many ways. Human activities can change the biotic and abiotic features of the environment. They alter the factors which determine the abundance and distribution of species. They change the cycle of materials. They interrupt the flow of matter and energy in ecosystems.
Humans have changed nearly half the world’s land surface and over half the accessible fresh water is used by humans.
Aboriginal Australians arrived many years ago and they had a drastic impact on the local Australian environment. For example – the use of controlled burning as hunting and land management technique influenced the abundance and distribution of native plants with more fire-resistant varieties surviving and becoming more prolific. Also the introduction of the dingo between 6000 and 3000 years ago was the next major change. The dingo appears to have no natural predators and therefore became the most dominant species.
Then European settlers arrived. They started clearing the land for buildings and agriculture. Clearing the land caused several disturbances such as removing habitat of many species. Many organisms either migrated or became extinct. Also clearing the land caused soil erosion which resulted in the removal of topsoil (which had the most nutrients) which affected plant growth. Also erosion caused siltation of rivers.
Also foreign species were introduced (either accidentally or intentionally). Many of these species became feral and feral animals often have more favourable features for survival than the native species and are better at competing for resources. For example the rabbit was introduced and this competes with the bilby for burrow space and the rabbit always wins.
Also the introduction of the prickly pear was disastrous as it caused widespread havoc across native ecosystems as well as agricultural systems.
The altering of waterways. Building dams not only floods areas that were once terrestrial but also changes the flow patterns and temperatures in the river. For example 99% of the water from the Snowy River was diverted due to the introduction of the Snowy Mountains Hydro-Electric Scheme. Changing water ways can result in rising salt levels in certain areas. Often the changes occur cause species to leave the area or to become extinct.
Furthermore the introduction of monocultures impacted on the distribution and abundance of species. A monoculture restricts the number of species that can live in that area.