1.7 Ecological Relationships Moodlebook PDF | CCEA GCSE Biology

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BetterOklahomaCity

Uploaded by BetterOklahomaCity

WHS Campus

2024

CCEA

Tilly Millsopp

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ecological relationships biology notes GCSE Biology ecology

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This document is a Moodlebook covering ecological relationships for CCEA GCSE Biology, Topic 7. It includes a table of contents, and various sections on biological terms, field work, competition, energy transfer, food chains, and more..

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1.7 Ecological Relationships Moodlebook Site: WHS Campus Printed by: Tilly Millsopp Course: 12A/Bi3 Date: Tuesday, 31 December 2024, 1:30 PM Book: 1.7 Ecological Relationships Moodlebook : ...

1.7 Ecological Relationships Moodlebook Site: WHS Campus Printed by: Tilly Millsopp Course: 12A/Bi3 Date: Tuesday, 31 December 2024, 1:30 PM Book: 1.7 Ecological Relationships Moodlebook : Description The course content for CCEA GCSE Biology Topic 7. : Table of contents Biological Terms Field Work Abiotic Factors Competition Transfer of Energy - An Introduction Food Chains and Webs Energy Losses and Trophic Levels Pyramids of Number and Biomass Decomposers The Carbon Cycle The Carbon Cycle and Global Warming The Nitrogen Cycle Root hair cells and active uptake Fertilisers, Nitrogen and Agriculture Water Pollution Human Activity and Biodiversity : Biological Terms In order to study the world around us, Biologists use a range of specialist terms to describe the relationships between living things. The following terms are commonly used and you should be familiar with them: Population: this is the number of organisms of a single species living in one area (e.g. the population of crows in a forest). Habitat: the term used to describe where an organism lives (e.g. a rock pool). Community: this includes all the living things in a specific habitat (e.g. the various types of insect living in or on a tree - the community includes all the insect species as well as the tree itself). Biodiversity: this term is used to describe the number of different species living in a given habitat or area (e.g. the biodiversity in a field of wheat is very low - there's only one species, but in a woodland there may be tens of different species. Environment: these are the surroundings in which an organism lives in and has both living and non living components Biotic: this is the term used to describe the living components of the environment (all the plants, animals and other species) Abiotic: the non living parts of the environment that might relate to the climatic factors like temperature, light intensity and humidity (a measure of moisture in the air) Ecosystem: a term that is used to describe the interactions of the living and non living parts of the ecosystem and how they are dependent upon each other. : Field Work Sampling In most cases, ecological studies are considering very large areas and it is impossible to count all the individual plant and animal species present. In order to make the process more efficient ecologists often sample the areas. Studying the world around us involves the use of a range of systematic sampling techniques. Collectively, these are known as field work. Often the techniques used will allow changes in the environment to be seen and this is reflected by trends in data that can be explained by considering changes in temperature and light intensity. A major aspect of sampling is ensuring that data is reliable. This is easily achieved through taking results from many different sampling points (i.e. using a large number of individual samples) and then calculating an average value. The more samples that are taken, the more the reliable the results. A further consideration when obtaining sampling data is to ensure that the data is representative - this simply means that what is recorded is a true reflection of what is actually in the environment. To ensure results are representative sampling points must be random. This ensures that bias (deliberate selection of sampling points based on, for example the presence of brightly coloured flowers) does not influence the results. Quadrats A quadrat is a simple frame (usually 0.5m x 0.5m) that can be placed on the ground in order to sample a specific area of ground cover. When using a quadrat the percentage cover is often estimated. It is not possible to record specific values of percentage cover so in most cases percentage cover values would be 1%, 10%, 20% and so on up to 100%. The number of quadrat sampling points used is dependent on the overall size of the area being sampled. It is important that enough data is generated (see notes on reliability above) so it is not sufficient just to record the values from a single position. More commonly 20 sampling points may be selected, the data collated in a spreadsheet or table and an average value for the percentage cover of each species given. : Could you estimate the % Cover of the different species in this quadrat? Belt Transects A belt transect is a technique used when there is gradual change from one habitat to another (for example from the edge to the centre of a forest or from the land into the sea - the rocky shore). In a belt transect, quadrats are placed along a line end on end allowing a strip of the ground and the species growing on it to be sampled. As the transect progresses from one end to another the numbers of certain species will decrease whilst others will increase. For example, at the rocky shore lots of barnacles would be found on the mid / upper shore whilst seaweeds would only be found on the lower shore. These changes in the species present are a direct result of the adaptations they have. In our example, barnacles are better adapted to being exposed to the air for long periods when compared to seaweeds. Therefore it makes sense that barnacles are found in large numbers on the parts of the shore that are above water for longer periods, whilst seaweeds are only found on those parts of the shore that are exposed to the air for short periods during the day. : What Is Environmental Sampling? | Ecology & Environment | Biology | FuseSchool              0:00 / 4:45 : Abiotic Factors There are a wide variety of abiotic factors that can influence what types of organisms can survive in a habitat. Most ecological investigations will also include methods to record some as these: Wind speed can be recorded using an anemometer. This factor can influence the types of species present for example in sand dunes and also in mountain ranges. The values of wind speed can indicate how exposed a certain habitat is. Water content of soils: plants need a ready supply of water to survive. For this reason sandy soils that don’t retain much water tend only to support a small number of highly adapted plants. In ecological investigations soil samples can be collected and returned to the lab. Weighing the soil and then drying out (in an oven or a microwave) until the mass stays constant allows the percentage water content to be estimated. The pH of soils can affect what types of plants grow there - some plants prefer acidic soils, whilst others have a preference for alkaline conditions. The pH of a soil can be tested chemically using a soil sample and universal indicator or simply by inserting a pH probe into the ground. Light intensity can greatly affect the distribution of plants. If plants are shaded by taller trees they will probably have adaptations to allow them to absorb a greater amount of the available light. Light intensity is easily measured using a light meter. Temperature is a further factor that can influence distribution of organisms and is readily measured using a soil thermometer. : Competition A major way that organisms interact with each other is via competition. Competition in ecosystems refers to the need for organisms to obtain resources from the habitat in which they live. There are many examples of resources that organisms compete for including: PLANTS: water light space minerals ANIMALS: food territory a mate shelter As can be seen from this list, the resources are all required if the organism is going to survive and reproduce. Usually there is not enough of the given resource for both organisms and therefore the organism that is better suited (adapted) will obtain more of that resource and its chances of survival are greater. By considering the abiotic data as well as the types of organisms found in an area (biotic data), ecologists can draw conclusions about how well adapted certain species are to their environment. : Transfer of Energy - An Introduction All organisms require energy in order to survive. Plants obtain their energy from the sun during the process of photosynthesis - essentially photosynthesis converts light energy from the sun into chemical energy in the form of molecules like starch. In turn, animals eat these plants and the energy is passed along. This continues if those animals are eaten by other animals. Plants are known as producers as they make their own food and make energy available to the rest of the organisms in the food chain. All animals are consumers and they can be classified as herbivores (plant eaters), carnivores (meat eaters) and omnivores (eat plant and animal material). Animals that feed on plants are referred to as the primary consumers. Primary consumers may be eaten by another animal which would be known as a secondary consumers and (yes you guessed it) these can then be eaten by animals referred to as tertiary consumers. BBC teach video : Food Chains and Webs In order to represent the feeding relationships in an ecosystem a food chain can be used. The organisms involved are assigned to a stage in the chain based on how they obtain their food - these stages are referred to as trophic levels. Plants, as producers, are always at the first trophic level. Animals will be found at the higher trophic levels - the primary consumer at the 2nd trophic level, secondary consumers at the 3rd trophic level and tertiary consumers at the 4th trophic level. A food chain should always contain arrows. These represent the flow of energy and the consumption of substances containing carbon and nitrogen. Food chains are very simple and don't show the various interactions that could be happening in reality (most animals don't rely on 1 single food source - they have many sources of food). A food web is a collection of food chains. Food webs are a better representation of what interactions are occurring in the ecosystems. : : Energy Losses and Trophic Levels Most food chains are very short - they don't usually contain more than 3 or 4 trophic levels. This is because energy is lost at each stage in the food chain. At the start of food chains, plants absorb light for photosynthesis - however this process is very inefficient with only a small amount of light energy actually hitting the plants gets absorbed by chlorophyll (most is reflected or passes through the leaf). Consumers are also responsible for a great deal of energy losses. Most stages in a food chain are only around 10% efficient. This means that around 90% of the energy available is lost. There are a number of ways energy is lost: 1. Not all of the available material is eaten: the roots of plants are inaccessible and bones and fur are often not consumed by carnivores 2. Much of the food is not digested - e.g. humans cannot digest cellulose and so it is egested as faeces 3. The process of excretion also results in energy losses 4. All organisms respire and lose energy as heat. This is best exemplified by thinking about what mass of food you have eaten over the last week - you have not increased by the same mass as you have respired the energy to food contains. Due to the energy losses at each trophic level, the longer a food chain becomes the less energy there is available. For this reason, shorter food chains are more efficient. Consider famine stricken countries where populations face starvation - would it make more sense to send them livestock like cattle and pigs to feed in order to produce meat OR send them foods such as rice and other grains?? : Pyramids of Number and Biomass Due to the energy losses that take place, it is common that the numbers of organisms found within a given trophic level decrease as you move up the food chain. The numbers of organisms at each trophic level can be represented in a form of graph known as a pyramid of numbers. Pyramids of number are not always the best representation of feeding relationships in a given habitat as they do not consider the size of the organisms at each trophic level - essentially a single 20m tall tree is represented in exactly the same way at a 3 mm insect. For this reason pyramids of number can often be inverted - for example a single oak tree (the producer and therefore the bottom tier of the pyramid) may provide food to thousands of caterpillars and these caterpillars may be fed upon by 10 black birds and there may even be 1 buzzard (a bird of prey) feeding on the black birds. To solve this issue, it is often more accurate to represent the biomass in a pyramid. Biomass is the mass of living tissue found at each trophic level. If the above example is considered it is clear to see that an oak tree is going to have a very high biomass and also that the subsequent levels in the pyramid will have gradually lower masses until the buzzard is reached. Guidance for Pyramids : Decomposers Food chains and webs not only represent the flow of energy, but also the journey certain nutrients make as one organism is eaten by another. Unlike energy, these nutrients are not lost from the food chain - they are either passed onto the next consumer in the chain or released as part of waste materials (e.g faeces and urine). Even if an organism dies, the nutrients it contains will eventually be released back into the ecosystem in the form of various minerals and other nutrients found in the soil. For this reason it is important to remember that, whilst energy flows; nutrients cycle. The processes involved in nutrient cycling are decay and decomposition. Various small animals such as worms and insects break down dead organisms as they feed on them - this is the process of decay. The wastes from these smaller organisms are then further broken down into simple molecules that can be absorbed by plants (thereby completing the cycle). The organisms responsible for the final stages of this breakdown are called the decomposers and include the bacteria and fungi. The bacteria and fungi digest the materials by releasing (secreting) enzymes from their cells onto the decayed material. These enzymes break the molecules down into a more soluble form that the bacteria and fungi then absorb. This mode of digestion is sometimes referred to as extracellular digestion and when it is used to complete the breakdown of dead material it is known as saprophytic nutrition (bacteria and fungi are sometimes referred to as saprophytes). Episode 4: Decomposers A major product of the decay and decomposition process is called humus - this material forms a large amount of the soil in which plants grow. The conditions required for effective decay and decomposition include a warm temperature, moisture and the a large surface area. : The Carbon Cycle The carbon cycle is a nutrient cycle that shows how carbon is passed from the atmosphere (where it is in the form of carbon dioxide) into plants (during photosynthesis) and on to animals as they feed on plants. The cycle also includes the processes of decomposition, combustion and fossilisation. If you like biology songs... you'll love this one.... Carbon Cycle Video - Lesson Starter The overall cycle is shown in the diagram below: An outline of each of the processes in the cycle is given below: : photosynthesis: plants absorb carbon, in the form of carbon dioxide, from the atmosphere during photosynthesis. Plants then use this carbon dioxide (combined with water) to form carbohydrates like starch feeding: as described on our work on food chains, plants are producers which are then consumed by animals. When this occurs the carbon in the biomolecules in the plants are passed into the animals respiration: all organisms respire. This process uses the carbohydrates (such as glucose) and produces carbon dioxide. This carbon dioxide is released back into the atmosphere. Remember that plants, animals and the decomposers all respire. combustion: this is burning, when any fuel (coal, oil, gas, wood) is burnt it releases carbon in the form of carbon dioxide back into the atmosphere. decomposition: this process breaks down any dead or decaying matter ensuring that the carbon contained within these molecules is released back into the atmosphere as carbon dioxide or released as minerals into the soil. fossilisation: under certain circumstances (e.g. when it is very cold or there's a lack of oxygen) dead organisms do not become fully decomposed. Over millions of years these partially decomposed materials are converted into fossil fuels such as coal, oil and gas. : The Carbon Cycle and Global Warming The levels of carbon dioxide in the atmosphere are gradually rising and this has been linked to a number of human activities. Humans rely heavily on the combustion of fossil fuels in order to generate electricity, heat our homes and for transport. This results in a greater amount of carbon dioxide being released into the air. The release of this carbon (in the form of carbon dioxide) from stores of carbon that are millions of years old, cannot all be absorbed by the plants on the surface of the earth during photosynthesis. Humans have cleared a great deal of forested areas in order to provide wood for building materials, clear land for housing, industry and roads. This is known as deforestation. As a result, there are fewer plants to absorb carbon dioxide during photosynthesis. As a result of these two activities there is an imbalance in the carbon cycle - there's a greater amount of carbon dioxide in the atmosphere than can be absorbed by the process of photosynthesis. Carbon dioxide is also linked to global warming. Carbon dioxide is an example of a greenhouse gas. These gases act as a blanket in the atmosphere that traps radiation (in the form of heat) that would otherwise escape back into space. Whilst some greenhouse gases are important to keep the earth warm enough for life to exist; it is clear that increasing temperatures can result in global problems such as: melting ice caps leading to increased sea levels climate change loss of habitats Global Warming 101 | National Geogra… In order to reverse these problems actions have been taken to reduce carbon dioxide emissions from combustion of fossil fuels (use of renewable energy sources like wind power), planting of more trees, conserving existing forest to reduce deforestation. : There is a great deal of evidence that links increased levels of greenhouse gases to global climate change. : The Nitrogen Cycle The second major nutrient cycle required for GCSE is the nitrogen cycle. Similarly to the carbon cycle, the nitrogen cycle shows how nitrogen gas is converted into nitrogen containing compounds in plants and animals (e.g. amino acids and proteins) and then how the nitrogen these compounds contain is recycled either back into the air or made available to other organisms. It is important as it shows how organisms obtain their amino acids and proteins which are required for growth. The following video explains the major processes involved. The Nitrogen Cycle GCSE Science Revi… As you have seen in the video there are a number of bacteria involved in the process. The attached table summarises the roles of each: Bacteria in the Nitrogen Cycle Nitrogen fixing bacteria can be found living in the soil as well as in the root nodules of a specific group of plants called leguminous plants. Leguminous plants include the bean and pea species as well as clover. The nitrogen fixing bacteria in the root nodules provide the plant with all the nitrates required for making amino acids and proteins. In return the plant provides the bacteria with a ready source of carbohydrates - these are required to allow the bacteria to respire. : Nitrification is a process that converts ammonia and other nitrogen containing ions in the soil into nitrates that can be readily absorbed by plant roots. Much of this ammonia is released by animals in their urine, whilst other ions containing nitrogen are produced as a result of decomposition following death and decay of plants and animals. Denitrification is the process that converts nitrates back into nitrogen gas. This is an undesirable process as it results in less nitrate being available in the soil and therefore reduced plant growth. The process is favoured by anaerobic conditions in waterlogged soils. : Root hair cells and active uptake In order to absorb minerals and water from the soil (such as nitrates) a plant's root are covered in specialised cells called root hair cells. These cells are adapted by having an increased surface area - due to the presence of an extension of their cell walls. In order to absorb minerals a process called active uptake is required. This is a process that moves materials from a region of low concentration to a region of higher concentration - against the concentration gradient. Active uptake requires energy released from respiration and therefore can only happen at a sufficient rate when oxygen is available - another reason why waterlogged soils (that are anaerobic) result in poor plant growth. : Fertilisers, Nitrogen and Agriculture As we have seen in our work on decomposers and nutrient cycles, nature relies on the death and decay of living material in order to recycle minerals so that new plants can grow. In farming however, plants that are harvested for food are not going to be present in the field to decompose. As a result of this, after every harvest there would be lower and lower amounts of minerals available in the soil. In order to ensure plants grow to their optimum, farmers will add fertiliser to their fields to replace the minerals used by the growth of the previous season's crops. Fertilisers can be natural - such as slurry, manure or compost or artificial. Most fertilisers will contain a combination of minerals such as nitrates, calcium and magnesium. Nitrates are required for the production of amino acids and porteins Calcium is needed for the production of new cell walls Magnesium is needed to make chlorophyll : Water Pollution Water pollution can happen for numerous reasons but a common cause in Northern Ireland is due to agricultural pollution related to "fertiliser run off". Often such occurrences are in the news as the results can be catastrophic, killing large numbers of fish. In May 2018 a slurry store wall ruptured releasing thousands of litres of slurry into a neighbouring river. Read about it here, or watch a news report here. This type of water pollution is known as "eutrophication" and it follows a very well established pattern that you should learn: 1. Fertiliser, slurry or sewage run off enters a water way such as a lake 2. The minerals contained in the run off result in an increase in the mineral content of the water (especially nitrates) 3. These mineral lead to increased growth of the aquatic plants (such as algae) 4. This leads to the surface of the water being covered in an algal bloom 5. This surface covering of plants blocks light from reaching the plants below 6. The plants in the water die 7. The dead plants are decomposed by aerobic bacteria that use up all the oxygen in the water 8. Fish and other animals in the water die as they have no available oxygen : As this type of water pollution has become more common strategies have been developed to make farmers more aware of how to use fertilisers more responsibly - e.g. no spreading slurry too close to the edge of fields where there's ditches or streams, not spreading slurry or applying fertiliser when heavy rains are forecast and encouraging the use of less soluble natural fertiliser over the more soluble artificial kind. : Drag to arrange the images in the correct sequence Bacterial respiration Oxygen depletion Light blocked and nut… Fertiliser run off and … Death of aquatic life -… Bacterial decompositi… Time spent 0:00 Total Moves 0  Check ShowSolution : Human Activity and Biodiversity Although much human activity is having negative effects on biodiversity (deforestation removing tress and habitats for animals; eutrophication of waterways and global warming leading to climate change), there are now many steps being taken to protect and enhance the existing biodiversity. Examples of this include sustainable woodlands - strategies taken to reduce the number of hard wood tress in rain-forest that are cut down. The trees in sustainable woodlands are only cut down in small areas at a time and are then replaced with new trees (reforestation) and trees are only cut down when they reach a large enough size. As much of human activity is affecting global biodiversity there are are regular international political meetings in order to develop policies to protect biodiversity. Examples of this include the Paris accord in 2015 and the Kyoto Treaty signed in 1997. The Paris accord involved 195 different countries signing up to a legally binding climate change deal in order to try and slow global warming. :

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