Unit 4: Ecosystems

How can we conserve biodiversity and forests?

1. Controlled replanting schemes (reforestation or re-afforesation) can be carried out allowing for sustainable timber production. "Sustainable" as in the trees that are removed are replaced and there is no ecological damage done to the environment 2. Smaller farmers around the rainforest can be given some financial aid to establish farms in other areas. These farmers are mainly poor locals whose family depend on income from the farm. Larger farmers on the other hand have no excuse since they are simply either putting cattle on deforested land for the burger industry or supplying palm oil for cosmetics 3. Breeding programs can help preserve species 4. Replanting hedgerows is beneficial because it provides a higher opportunity for biodiversity than fields 5. Reducing the release of greenhouse gasses and recycling reducing deforestation and the release of greenhouse gases

What is the role of denitrifying bacteria in the nitrogen cycle?

1. Denitrifying bacteria These bacteria use nitrates as an energy source and convert them into nitrogen gas. Denitrification reduces the amount of nitrate in the soil.

How have humans reduced biodiversity?

1. Eutrophication As the human population increases, we need more food and therefore increase our use of fertilizers. This impacts the biodiversity of the aquatic environments by making them anoxic and therefore killing the organisms that live there 2. Fish farming Fish farming can reduce biodiversity because when fish are farmed in large nets or tanks within lakes, farm waste, chemicals, pathogens and parasites are released into surrounding water, harming other marine life Carnivorous fish like salmon are fed fish from the wild populations. Fish can escape and compete with indigenous wild species meaning they have to compete for resources. Predators of the fish can become trapped in the nets and die 3. Introduction of non-indigenous species An species can be introduced for removal of pests or for hunting. However, they can kill naturally occurring species For example, Cane toads were introduced to Australia to control pests that ate sugar cane. Instead, their population has spread and rapidly grown and they have reduced biodiversity since they are poisonous to animals that eat it which reduces the number of predators, eat insects and compete with native species of food

What are the different interactions in ecosystems?

1. Feeding amongst organisms- the plants, animals and decomposers are continually recycling the same nutrients through the ecosystem 2. Competition amongst organisms: a) Animals compete for food, shelter and mates b) Plants compete for carbon dioxide, mineral ions, light and water 3. Interaction between organisms and the environment: a) Plants absorb mineral ions, carbon dioxide and water from the environment b) Plants give off water vapor and oxygen to the environment c) Animals use materials from the environment to build shelters and the temperature of the environment can affect the processes occurring within organisms d) Processes ocurring in organisms can affect the temperature of the environment

What competition can their be between animals?

1. Food All animals require food to provide them with the energy and raw materials to complete life processes, without which they may die. Because of this, competition for food can be intense. Some organisms have evolved to eat certain species to reduce competition 2. Mates Animals within species compete for mates so they can pass on their genes to their offspring. Animals have evolved to have a natural drive to reproduce which can result in competitive fights. For example, large male deer fight each other by locking antlers and rutting (pushing against each other) which can result in serious injury or death. However, this benefits the population as only the strongest pass on their genes to the next generation 3. Territory The territories of animals contain all of the resources and conditions they need to survive including abiotic features such as light, temperature and water and biotic factors such as food and predators. Many animals will fight for territory Intraspecific competition (between the same species) over territory would be between lions in the grass plains of Africa whereas interspecific competition (between different species) would occur when another predators like leopards lived close to the lions

What is the role of free living nitrogen fixing bacteria in the nitrogen cycle?

1. Free living nitrogen-fixing bacteria These bacteria in soil convert nitrogen gas into ammonia. This is used by bacteria to make amino acids and proteins. When the bacteria die, their proteins decompose, releasing ammonia back into the soil

Give an example of a habitat with a low and high biodiversity?

1. High biodiversity - a rainforest contains thousands of different species of plants and animals in relatively even numbers 2. Low biodiversity - pine forest plantations of Northern Europe are dominated by one species of tree. The trees produce a very dense canopy which doesn't allow much sunlight to the ground an therefore, restricts the growth of other tree species or ground layer plants. It also provides a limited variety of habitats for animals

How do greenhouses and polytunnels provide controlled conditions for plants to grow?

1. Light The transparent walls of the glasshouse allow enough natural light for photosynthesis during the summer months, while additional lighting provides a "longer day" during winter 2. Heat Short wavelength infrared radiation entering the glasshouse is absorbed and re-radiated as longer wavelength infrared radiation. This longer wavelength cannot escape through the glass, so the glasshouse heats up The glass house also reduces convection currents that would cause cooling In addition, the glasshouse can be heated to raise the temperature inside if the temperature outside is too low potentially using fossil fuels A farmer should only heat his glasshouse to the optimum temperature for photosynthesis so he can maximize his yield. Any more is a waste of money as there is no further increase in yield after the optimum peak 3. Carbon dioxide and water vapor If the heaters use fossil fuels, this produces carbon dioxide and water vapor The carbon dioxide and water are reactants for photosynthesis The water vapor maintains a moist atmosphere and reduces water loss from the plant by transpiration 4. Nutrients If the plants are grown in a hydroponic culture this provide the right balance of mineral ions for a particular crop

How does lightning convert nitrogen gas into nitrates?

1. Lighting converts nitrogen gas in the air into oxides of nitrogen 2. These dissolve in rainwater and enter the soil 3. Then they are converted into nitrates by nitrifying bacteria

What is the role of nitrogen fixing bacteria in the root nodules in the nitrogen cycle?

1. Nitrogen-fixing bacteria in the root nodules These bacteria also make ammonia but this it is converted by the plant into amino acids and other organic nitrogen compounds. Death and decomposition of the plant returns the nitrogen to the soil as ammonia Some nitrogen fixing bacteria have associations with the roots of legumes and form little bumps or root nodules Instead of entering the soil, the ammonia that the bacteria make by fixing nitrogen is passed to the plant which uses it to make amino acids. In return, the plant provide the bacteria with organic nutrients. This is an example of mutualism, where they benefit from each other's relationship. This nitrogen fixation enriches the soil with nitrates when the plants die and are decomposers

What are the problems with pesticides?

1. Resistance a) Pests can become resistant to a certain chemical in a pesticide which is a form of natural selection 2. Environmental damage a) Pesticides may be slow to decompose so they are persistent in the environment b) This can cause them to bioaccumulate in the tissue of organisms which can risk poisoning them c) This can also cause biomagnification where the level of chemicals build up and become more concentrated along the food chain. This is due to the higher trophic levels eating organisms which have a bioaccumulation of toxic chemicals in them d) Pesticides can also kill non harmful insects as well as helpful species such as bees

Can our population keep growing?

1. Some scientists thing that the human population will continue to increase and humans will be able to solve problems that come their way 2. Others think that humans will run out of food, fresh water or other resources and the earth's population with stop increasing but remain high nevertheless 3. Other scientists think that at some point the human population will reduce significantly, which is called a crash. In the past, plagues have caused a rapid decline in the population and something similar could occur in the future

What assumptions are made when using the mark-capture-recapture method?

1. There is no death, immigration or emigration 2. The sampling methods used are identical 3. The marking has no affected the survival rate of the animals

How these abiotic factors be measured

1. pH of soil- a pH meter uses a probe to get results 2. Light intensity - light intensity meters are pointed in the direction of maximum light intensity 3. Soil moisture- soil moisture meters 4. Water pollution Species can act as bioindicators of the oxygen levels (and as a result pollution) in water by their presence or absence Clean: stonefly nymph, mayfly larva Some pollution: freshwater shrimp, caddis fly larva Moderate: bloodworm, water louse High: sludge worm, red-tailed maggot Very high: no living insects 5. Air pollution Sulfur dioxide is released from burning coal. Lichens cannot survive if the concentration of sulfur dioxide is too high and so can be used as indicators for air pollution. For example, in the further away from the city, the greater the number of lichens

What is a biome

A large area of the earth dominated by a specific type of vegetation

What is the food chain within a farm?

A modern farm is a sort of managed ecosystem with many of the interactions between biotic and abiotic components remaining the same Crop plants depend on light and mineral ions from the soil as well as other environmental factors Stock animals depend on the crop plants for food 1. Grass and root crops are eaten by cattle and sheep which are then eaten by humans 2. Potatoes and vegetables are eaten directly by humans 3. Wheat, barley, sugar beet and oilseed rape are eaten by pigs and poultry, which are then eaten by humans, or are manufactured into products such as bread, cereals and margarine which are also eaten by humans

What is a pyramid of numbers?

A pyramid of numbers represents the numbers of organisms at each trophic level in the food chain, irrespective of mass. Pyramids of number don't necessarily decrease at every level like pyramids of biomass do. For example, two oak trees at the bottom of the pyramid could support thousands of aphids. If parasites are introduced, a large upper level can be added to the pyramid since many will live on each organism in the level below.

What are some of the effects of global warming

A rise in the earth's temperature of only a few degrees would have many effects: 1. Polar ice caps would melt and sea levels would rise which could threaten coastal cities 2. A change in the major ocean currents would result in warm water flowing into previously cooler areas 3. This could cause a change in global rainfall patterns. With a rise in temperature, there will be more evaporation from the surface of the sea, leading to more water vapor in the atmosphere and more rainfall in some areas. Other areas could experience a decrease in rainfall 4. The nature of many ecosystems could change. If species can't migrate quickly enough to find new, appropriate habitats, they could become extinct 5. Changes in farming practices would be necessary as some pests would become more abundant and distribute differently. High temperatures might allow pests to complete their life cycles more quickly. This could impact food scarcity 6. Tropical diseases may become more common in other regions

What is a transect?

A transect is a line across a habitat or a part of a habitat and can simply be a string or rope on the ground. The number of organisms of a species along a transect can be recorded at regular intervals using quadrats. Transects are useful for observing the distribution of organisms in a habitat. A kite diagram shows the number of animals (or percentage cover for plants) against distance along a transect. A gradual change in the distribution of species across a habitat is called zonation. It can happen because of a gradual change in an abiotic or biotic factor. Transects are usually used to investigate the distribution rather than counting the population size

Label all the biotic and abiotic components of a pond?

Abiotic components: 1. Sunlight 2. Air 3. Soil 4. Water Biotic components: 1. Floating plants in an open water habitat 2. Plankton in an open water habitat 3. Rooted plants in a partly water, partly soil, partly air habitat 4. Snails in a surface of soil and plant habitats grazing on small organisms

Practical investigating the effect of abiotic factors on organisms:

Abiotic factors are non-living and include light intensity, temperature and moisture levels. They affect the abundance and distribution of living organisms. For example, a shingle beach has small stones instead of fine sand. Plants seeds can lodge between the small stones and start to grow, particularly at the top of the shore away from the waves. 1. Set up a transect along the shingle beach 2. Every five meters, place a quadrat on the beach and measure the height of all the plants found 3. Present the results in a graph 4. You should find that the height of plants increases the closer they are to the top of the shore (the further they are from the waves). You should also find that the deeper the soil, the taller the plants

What should an ideal pesticide do?

An ideal pesticide should: 1. Control the pest effectively 2. Be biodegradable so that no toxic products are left in the soil or on crops 3. Be specific, so that only one pest is killed 4. Not accumulate in organisms 5. Be safe to transport, store and apply 6. Be easy to apply

How are materials recycled in our ecosystem?

Atoms exist in different forms of compounds at different times and cycle between them. Elements pass along food chains when animals eat plants and other animals. For example, when a human eats meat, they break down the protein into amino acids used for growth and repair. When they die, these are returned to the environment and used by other living organisms by decomposers who break down the dead organism and return minerals and nutrients to the environment. In addition, when they respire they release carbon dioxide into the environment, helping to recycle carbon Materials can cycle through being biotic and abiotic components

Why do we use quadrats?

Because it is impractical to count all the organisms in a population: 1. The organisms may move into or out of the area during counting 2. Some may die in the time it takes to complete counting 3. It may be difficult to find all the animals during counting

Why can't nitrogen be used directly by plants or animals?

Because nitrogen in the air is in the form N2 with a strong triple bond between the two nitrogen atoms. The plants cannot use this for two reasons: 1. A large amount of energy would be required to try and break the triple bond 2. Without breaking the bond the molecule is very unreactive and so will not combine with chemicals to make amino acids

Why isn't the sun at the bottom of the food chain?

Because the sun isn't living. Only about 1% of the Sun's energy reaches plant leaves to be used during photosynthesis. This sounds small but is enough to power almost all the food chains on the planet

What are pyramids of biomass?

Biomass is living in or recently dead tissues and is called "biomass" rather than mass because it is alive. Wood is considered biomass because it was recently a plant. Fossil fuels on the other hand are not considered biomass because they are remains of organisms that died millions of years ago and have been chemically changed from the original living tissue. Fresh biomass refers to living organisms and dry biomass describes the mass of the plant or animal material after water has been removed by drying in an oven. This is more reliable since the water content of organisms varies with environmental conditions. In pyramids of biomass, the total biomass of each trophic level is displayed as a modified bar chart irrespective of the number of animals

What are the components of an ecosystem?

Biotic Components- the living components of an ecosystem 1. Producers- make their own organic nutrients using energy from sunlight (photosynthesis) 2. Consumers- animals that get all their energy from consuming other organisms (like plants and animals) 3. Decomposers- organisms that break down dead material and help to recycle nutrients (this includes fungi and some bacteria) Abiotic components- all the non-biological components of the ecosystem such as water, soil and air Using a pond as an example: 1. Environment- the area surrounding a living organism 2. Habitat- the place where the organism lives ( eg. the open water, the mud at the bottom of the pond and surface water ) 3. Population- all the members of a single species that are found in an ecosystem at a particular time ( eg. all the tadpoles swimming in a pond are the population of tadpoles and all the waterlily plants growing in a pond are the population of water lilies) 4. Community- all the populations of different species 5. Ecosystem- a community and the habitat in which it lives

What are the biotic factors affecting the abundance and distribution of living organisms?

Biotic factors are living: 1. Availability of food All animals require good and its availability is a major factor in how animals live in an ecosystem. Areas like rainforests with rich food supplies have more species of life than other areas like deserts where there is less food 2. New predators The arrival of predators in an ecosystem can have a drastic effect. In balanced ecosystems, predators and prey have evolved to together. Therefore, the predators that have been in the ecosystem for a long time are able to catch enough food to survive but not enough to drastically affect the population size. This is why a new predator can upset the balance and rapidly decline the numbers of prey which then reduces the food supply for existing predators 3. New pathogens When organisms inhibit new ecosystems they bring new pathogens with them. For example, Europeans introduced the influenza to North America and many native Americans didn't have immunity to the disease and so were killed. Pathogens can also be introduced on purpose. Myxomatosis is a virus that affects rabbits by causing them to develop skin tumors and go blind. In the 1950s it was released to reduce the UK's rabbit population. However, they developed immunity and numbers eventually grew back to normal 4. Competition The introduction of new species into an ecosystem can result in competition that drives out the native species. for example, grey squirrels were brought over from North America by wealthy people and let free in their grounds. Smaller native red squirrels couldn't compete with the larger grey squirrels since they can store more fat and survive harsher winders. Therefore, the number of grey squirrels decreased dramatically.

What is the carbon cycle

Carbon is a component of all major biological molecules such as carbohydrates, lipids, proteins, DNA, vitamins and many other molecules. 1. Photosynthesis fixes carbon atoms from carbon dioxide (inorganic) into organic compounds such as proteins, fats and carbohydrates. 2. Feeding and assimilation pass carbon atoms already in organic compounds along the food chain 3. Respiration produces inorganic carbon dioxide from organic compounds (mainly carbohydrates) as they are broken down to release energy 4. When living things don't decay fully when they die due to conditions in the soil (for example the soil is too acidic) they become fossil fuels (coal, oil, natural gas and peat) 5. Combustion from burning the fossil fuels releases carbon dioxide into the atmosphere In summary: 1. Plants Contribute to carbon atoms in inorganic compounds in the atmosphere and oceans -Photosynthesize and take in carbon dioxide -Respire and release carbon dioxide Contribute to carbon atoms in organic compounds -Dead remains 2. Consumers Carbon atoms in carbohydrate, lipids and proteins are passed on by feeding assimilation Contribute to carbon atoms in inorganic compounds in the atmosphere and oceans -Respire and release carbon dioxide Contribute to carbon atoms in organic compounds -Dead remains -Excretory products 3. Decomposers Contribute to carbon atoms in inorganic compounds in the atmosphere and oceans -Respire and release carbon dioxide Contribute to carbon atoms in organic compounds -Decay and absorb carbon atoms from dead remains and excretory products 4. Fossil fuels Contribute to carbon atoms in inorganic compounds in the atmosphere and oceans -Release carbon dioxide in combustion Contribute to carbon atoms in organic compounds -Take in carbon atoms in fossilization from dead remains and excretory products

What are CFCs?

Complex organic molecules containing carbon, chlorine and fluorine which were once widely used fridges, spray cans and solvents as well as in making materials such as foam packaging. Their use has been banned in many countries since they were found to be damaging the ozone layer in the upper atmosphere (the layer protecting living organisms from absorbing UV radiation from the Sun)

What encourages pests?

Cultivating large areas of land with a single crop (a monoculture) encourages pests. Monocultures make harvesting crop easier but if a pest arrives it can easily spread through the crop. During winter the pest can lie dormant in the soil ready to attack next year's crop. Crop rotation breaks the pest cycle which is where different crops are grown each year. When over-wintering pests emerge, their preferred crop is no longer there

Explain the case of DDT?

DDT was used in world war two to kill malaria carrying mosquitos and the lice that carried typhus. It was banned completely in 2004. Limited use of the pesticide is still allowed for controlling disease-transmitting insects. DDT is a very effective pesticide, so why has it been banned? 1. It is very persistent and remains active for many years. If it is sprayed on a field, it takes ten years to biodegrade into DDE which is also a potent pesticide, and some will have spread to other habitats by wind. In fact, it has been identified in the polar ice caps, thousands of kilometers away from where it was applied 2. Many types of insects began to appear as resistant to DDT in the fifties. They had developed a genetic mutation that prevented them from being killed by the insecticide and grew rapidly in numbers. They reproduced and passed on the resistant genes to their offspring which is a form of natural selection 3. DDT kills any type of insect, including butterflies and bees. It also kills predators such as wasps which might have been able to kill the pest insects. This disrupts several food chains 4. DDT is very soluble in fats. When a herbivore feeds on a plant that is contaminated with DDT, the insecticide is not broken down or excreted but becomes concentrated in the fatty tissue of the animal which is called bioaccumulation 5. When a carnivore eats the herbivore, this process is repeated so that the insecticide concentration builds up along the food chain. This is known as biomagnification. the levels at the top of the food chain can be toxic, leading to the death of carnivores and disrupting the food webs of an ecosystem

How can we produce potable water?

Drinking water is usually provided by precipitation which can be a problem if there is drought. Seawater is na abundant source of water but has high salt content. Therefore, distillation can be used to produce pure water from seawater. This is also known as thermal desalination. During distillation, the seawater is boiled and the water vapor is cooled and condensed to form pure water, leaving salt behind This can be expensive since large amounts of thermal energy are needed and it increases the use of fossil fuels. Carbon dioxide emissions from burning fossil fuels contribute to global warming. Wealthy middle eastern countries tend to use this since they have minimal access to rain. Water can also be desalinated through reverse osmosis. Salt water is forced at a high pressure into a vessel with a partially permeable membrane and the pressure causes water molecules to move in the opposite direction to osmosis from a concentrated salt solution to a lower salt solution. Water molecules pass across the membrane, leaving the salt behind, so pure water is available for drinking

Why is biodiversity good?

Ecosystems with high biodiversity are more stable than ecosystems with low biodiversity This is because an ecosystem dominated by one (or a few) species is likely to be severely affected by ecological disaster For example: 1. Disease could wipe out an entire dominant species of trees, which would impact other species that relied on them for food and shelter. However, in a more biologically diverse ecosystem, other tree species might be able to supply the shelter and food instead and keep the populations of other species alive 2. If the numbers of one species is affected, it can cause consequences for other species. A simple food chain is: algae → zooplankton → sand eel → puffin → arctic skua If the size of zooplankton are reduced by pollution, then more algae will grow and prevent light from entering the aquatic environment, meaning that the population of other consumers will fall 3. Ecosystems with higher biodiversity have fewer species that depend on just one another for food, shelter and maintaining the environment. Using the example above, puffins could also eat mollusks and worms and therefore can adjust if the sand eel population decreases 4. Maintaining important biological resources such as food and medicines is easier with high biodiversity. This is important on a global scale. 5. Recreation and tourism benefits the local people since areas with high biodiversity are more attractive places to visit. This provides them with both recreation and income. This is important on a local scale

What is eutrophication?

Eutrophication comes from the greek word "well-fed" and refers to a situation where large amounts of nutrients enter a body of water, such as a river, lake or sea. The nutrients in question are inorganic mineral ions such as nitrates or phosphates. Pollution by these minerals can have a harmful effect on an aquatic ecosystem. The two main sources of excess minerals are: 1. Untreated or treated sewage 2. Artificial nitrate or phosphate fertilizers Eutrophication is often caused by the use of artificial fertilizer. Streams and rivers that run through agricultural land that that have been treated with fertilizer can contain high concentrations of nitrate and phosphate. This is because nitrate is very soluble in water and easily washed out of the soil by rain, which is known as leeching. This is less of a problem with phosphate fertilizer which is washed into waterways by surface run-off of water 1. Algal Bloom - The excess mineral ions stimulate the growth of plants in the body of water which is usually first seen as a rapid growth of algae. This is called an algal bloom and can increase in numbers to rapidly that it forms a thick scum on the surface of the water 2. Depleting oxygen and light - The algae soon start to die and are decomposed by aerobic bacteria in the water Because bacteria respire aerobically, they use up the oxygen in the water In addition, the algae block the light from reaching other rooted plants, further decreasing the oxygen produced by photosynthesis The low oxygen levels can result in fish and other aerobic animals dying In severe cases, the water becomes anoxic (containing very little oxygen) and smelly from gases like hydrogen sulfide and methane from the bacteria By this stage, only anaerobic bacteria can survive.

What is the problem with food chains?

Food chains are a convenient way of showing feeding relationships but are oversimplified. They suggest that each organism only feeds on another particular organism. Food webs demonstrate how all the different food chains in an ecosystem relate to each other and give a clearer picture of the feeding relationships involved. Even though some feeding relationships still aren't shown in the food web, it gives a better indication of the interrelationships that exist between the food chains.

What factors are affecting food security?

Food security is a measure of how much food there is, whether it is of a suitable quality and whether people can access it Food security is reduced by: 1. An increase in the human population due to better health care 2. Changing diets in newly developed countries such as China mean that food resources are transported from areas that need them 3. New pests and pathogens attack crops and farm animals 4. Environmental changes 5. Increased farming costs 6. Armed conflicts

Can you predict how changes in numbers of an organism in one food chain in the food web can affect those in another food chain?

For example, in a food web leeches are eaten by the mature salmon and feed on midge larvae. Therefore, if the population of leeches decreased due to disease, the stonefly nymph population could increase since they would have more midge larvae to feed on However, the mature salmon would also eat more stonefly nymphs since there is a lower population of leeches meaning their numbers would decrease The population of stonefly leeches could remain the same due to a combination of the above

How can we estimate the population size of an animal species?

If an animal species consists of large organisms that move at a pace too quick to count them or who live in an aquatic environment, the capture-mark-recapture method can be used to estimate the population size 1. Animals are trapped, marked in a harmless way and released 2. The traps are used again a few days later and the number of marked and unmarked animals caught in the traps is recorded 3. The population size can be estimated with the following equation: The number of animals in the first sample x the number of animals in the second sample / the number of previously marked animals in the second sample

What is the effect of sewage in waterways?

If sewage is discharged untreated into waterways, it produces two major problems: 1. Aerobic bacteria in the water polluted by the sewage use up the dissolved oxygen in the water as they break down the organic minerals. This reduction in the level of oxygen kills larger animals such as freshwater insects and fish 2. Untreated sewage contains pathogenic bacteria which can pose a threat to human health Only species that are adapted to low oxygen conditions such as anaerobic bacteria can survive. As the water moves away from the outlet, it becomes oxygenated again as it mixes with clean water and absorbs more oxygen from the air. This increase in dissolved oxygen levels allows more clean-water species to survive In summary: When the water is sewage effluent, oxygen levels and clean water animals decrease and the population of bloodworms increase. As the water moves downstream, the bloodworm population decreases and oxygen/clean water animals increase The aim of sewage treatment is to remove solid and suspended organic matter as well as pathogenic microorganisms so that cleaner waste can be discharged into the waterways. The level of pollution by organic material can be monitored by the presence/absence of indicator species.

How can a quadrats be used to compare the size of a plant population in two areas of a field?

Imagine that there are two areas of a school field (A and B) that seem to contain different numbers of dandelion plants. Area A is more trampled that area B and looks like it contains fewer dandelions. The proposed hypothesis for this could be: "The dandelion population in area A is smaller than the dandelion population in area B" 1. Following the random sampling method, put to 10m tape measures in area A to form the sides of a square and randomly generate coordinates for the quadrats to be placed on. 2. Count the number of dandelions in the quadrat and repeat until you have ten sets of results for area A 3. Move the tape measures to area B and repeat the process 4. Once you have the results in a table, calculate the mean number of dandelions per meter squared and compare the population numbers in the two areas to see if your hypothesis was correct 5. Make sure to wash your hand after this experiment since you may have come into contact with animal faeces

How can we use quadrats to compare the biodiversity of plants in two habitats?

Imagine that there are two other areas of the field (C and D) that seem to contain different numbers of various plant species. A hypothesis about this observation might be: "the diversity of plants in area C is higher than in area D" Ten 1 meter squared samples are taken in each area. The numbers of plant species present in each quadrat are counted. The results from this can be plotted as two bar charts with the total numbers of each species against the species name and compared

What is a food chain?

In any food chain, the arrow means "is eaten by" and shows a transfer of biomass as well as the direction of energy flow from one trophic level to another The first trophic level at the bottom of the food chain is the producer. This is usually a plant or alga that can photosynthesize to convert carbon dioxide and water into glucose which provides all the biomass for the food chain The second trophic level in all food chains is the primary consumer which is a herbivore or an omnivore The third level is a secondary consumer and is a carnivore who eats the primary consumer There can be additional consumers above this which are tertiary and quaternary consumers. The final level is perch, which is a carnivore and often called the top apex predators. Organisms at the top of the food chain have no predators Decomposers are bacteria and fungi which breakdown dead plant and animal matter. They secrete enzymes on the surface of dead organisms to break down and absorb the digested, smaller food molecules. Plants can also absorb the broken down nutrients from their roots

What do we use to sample the number of organisms in a population?

Instead of counting all the organisms in a population, an ecologist counts a smaller representative part of it called a sample To sample plants or animals that don't move much (such as snails) quadrats can be used Quadrats are grids made from metal, wood or plastic that are available in different sizes depending on the size of the organisms you want to sample

How does biological control work?

Instead of using a toxic chemical, biological control uses another organism to reduce the numbers of a pest. For example, if there are too many whiteflies in a tomato glasshouse, then a parasite called encarsia parasitises can be used to kill their larvae, reducing the numbers of adult whitefly. Examples of biological control are: 1. Introducing a natural predator 2. Introducing a herbivore to eat weeds 3. Introducing a parasite 4. Introducing a pathogenic microorganism 5. Introducing sterile males to reduce reproduction rates 6. Using pheromones which are natural chemicals produced by insects to attract a mater. They are used to attract pests (either male or female) into traps which are then destroyed, reducing the reproductive potential of the population

Which factor is the most important?

It is difficult to generalize about which factor is most important. In a heavily polluted river organisms could be killed, while in a clean river depth and flow ate might have a greater effect on the animals that live there. The factors also affect each other; a faster flow rate could mix the water with air, increasing the amount of dissolved oxygen . The main biotic factor however is probably food supply whilst the main abiotic factor is probably climate.

What is important when using quadrats?

It is important that sampling in an area is carried out at random to avoid bias. For example, if you were counting the dandelions on a school field and you chose to place the quadrats next to a path for convenience, this would be a biased sample since there is more foot traffic and the population wouldn't be representative of the whole field A misconception is that you should throw quadrats over your shoulder. This isn't random through since the place where the quadrat falls will depend on where you stand and how strong you throw it Therefore, quadrats could be placed at coordinates on a numbered grid: 1. Use two 10m tape measures arranged to form the axis of a graph 2. Use a random number function on a calculator to generate the number that will be the coordinates of the quadrat 3. Use these coordinates and a another tape measure to position the quadrat on the axis at the random coordinates Another thing to note is that the validity and reproducibility of your results will increase the more quadrats are analyzed

What is the problem with biological control?

It never fully gets rid of a pest. if the control organism killed all the pests, then it would also die out since it would have no food supply. Biological control aims. to reduce pest numbers to a level where they no longer cause economic damage

How is methane produced?

Methane is an organic gas and is produced when microorganisms ferment larger organic molecules to release energy: 1. Decomposition of waste buried in the ground by microorganisms (landfill sites) 2. Fermentation by microorganisms in the rumen of the cattle and other ruminants 3. Fermentation by bacteria in rice fields Methane is a greenhouse gas and has similar effects to carbon dioxide. Although there is less of it in the atmosphere, each molecule has a much bigger greenhouse effect

How can organisms be collected for counting?

Methods include: 1. Sweep nets- useful for collecting insects and small animals from bushes, long grass and ponds 2. Pooters- a small jar used for collecting insects that has two tubes: one goes into your mouth so you can apply suction, and the other goes over the insect so it can be sucked into the jar. A fine mesh prevents you from swallowing the insect 3. Pitfall traps- often used to get a sample of small invertebrates living on the ground such as beetles, spiders and slugs. It consists of a container buried in the ground and the top of the container being covered by a piece of wood with a slight gap to allow insect to climb in. It is important to check the trap regularly so that he animals don't escape or get eaten before they're counted

What is mutualism?

Mutualism is a relationship which both species are benefiting from. For example, bees and flowering plants have a mutualistic relationship and obtain nectar for food whilst spreading the flower's pollen from one plant to another. This helps the reproduction of plants. Fish can also display mutualism. Cleaner fish are small fish that swim near larger species and eat the parasites around their gills. In this way, the cleaner fish derive nutrition and protection from the larger fish and the larger fish have their gill parasites removed Lichens are another example of mutualism since they are formed by algae and fungi living together. Algae can photosynthesize and make food which is shared by the fungus. the fungus shelters the algae from a harsh climate in turn

What is the nitrogen cycle?

Nitrogen is an element that is present in proteins, amino acids, vitamins, DNA and ATP 1. Plants can absorb and assimilate nitrogen in two ways: a) If they are a legume, nitrogen gas in the soil can be made into ammonia by nitrogen fixing bacteria in their root nodules. The plant will then convert ammonia into amino acids used to make proteins b) If they don't have root nodules, they can absorb nitrates nitrified from ammonia by nitrifying bacteria. They combine these nitrates with carbohydrates from photosynthesis (e.g. glucose) to form amino acids and other nitrogen containing compounds 2. Feeding and assimilation by animals of the plant passes the nitrogen part of the proteins, vitamins and DNA of the plant along the food chain 3. When the plant and animal die, the nitrogen in compounds such as proteins, vitamins and DNA are broken down by decomposers (bacteria and fungi) into ammonia 4. The ammonia goes through nitrification. Firstly, the nitrifying bacteria oxidise it to form nitrite (NO2-) and then to nitrate (NO3-) 5. Aside from being absorbed by plants, the nitrates can be occasionally converted by denitrifying bacteria into nitrogen gas. Denitrifying bacteria use nitrates as an energy source and reduce the amount in the soil. Denitrification is unfavorable for plant grow and occurs in water logged soil so farmers try to avoid this in an effort to minimize the need for fertilizers 6. The nitrogen gas produced during denitrification is then either fixed by the nitrogen-fixing bacteria in the root nodules of legumes or converted by free-living nitrogen-fixing bacteria in the soil into ammonia. The bacteria then use the ammonia to make amino acids and proteins 7. When these free-living nitrogen-fixing bacteria die, their nitrogen containing compounds are decomposed into ammonium by bacteria and fungi

Why do pyramids of biomass and pyramids of energy decrease with each level?

Not all of the biomass and energy ingested by members of a trophic level is passed onto the next trophic level. The decrease in energy and biomass are interlinked. Some biomass and energy , including undigested materials or bones are either not eaten or egested by the consumer. As a result, biomass as well as energy is lost. Some biomass and energy is lost in excretion. When an animal eats more protein than it needs, it is broken down into urea and passed out the body with water. This decreases biomass as well as being a loss of energy. This goes for respiration as well, the usage of glucose and the exhalation of carbon dioxide decreases biomass as well as energy Finally, the breakdown of biomass during respiration is partially used to keep the body at a constant temperature as well as some thermal energy being transferred to the surroundings during the process This is why not all the biomass ingested becomes part of the organisms in the next trophic level and only 10% of energy is passed on. Usually there are only four trophic levels since there isn't enough energy to support any more For example, if a rabbit eats grass, not all of the material in the grass plant ends up as rabbit: 1. Some parts of the grass aren't eaten 2. Some parts are not digested and so are not absorbed 3. Some of the absorbed materials form excretory products 4. Many of the materials are retired to release energy, with the lose of carbon dioxide and water Therefore, only a small fraction of the materials in the grass end up as new cells in the rabbit.

Does deforestation affect oxygen levels?

Not really; deforestation doesn't particularly affect oxygen levels because, in the rainforest, oxygen produced by the living plants is roughly balanced by the oxygen consumed by decomposers feeding on dead plant material

How are nutrients cycled on a farm?

On a farm, carbon and nitrogen are circulated differently than in the natural ecosystem 1. Nitrates from the soil supply nitrogen that is needed to make proteins in plants 2. Some of these plants are sold to the public and the rest will be fed as fodder to the stock animals 3. When the crops are sold to humans, the nitrogen in the proteins goes with them and they are lost from the farm ecosystem 4. Similarly, when livestock is sold the nitrogen in their proteins (gained from the fodder) is also lost from the farm ecosystem 5. To replace the lost nitrogen, the right amount of fertilizer is added to increase crop yields (but not so much so that it is a waste of money) In summary: e = extra nitrogen to replace the losses l = losses of nitrogen from farm ecosystem n = natural circulation of nitrogen Nitrogen gas (e) 1. Legumes (such as clover) decomposers decay them when they are ploughed in (e) 2. Ammonia nitrifying bacteria (n) 3. Nitrite nitrifying bacteria (n) inorganic fertilizers (e) 4. Nitrate absorption and assimilation (n) 5a. Crops sold (l) 5b. Fodder a) feeding (n) b) straw for farmyard manure (an organic fertilizer) 6. Feeding faeces and urine for farmyard manure (an organic fertilizer 7. Manure decomposers and nitrifying bacteria 8. Ammonia

What is parasitism?

Organisms depend on other species for resources such as nutrients. Parasites live in or on another organism (called the host) Parasites often take what they need from the host and give nothing in return, causing the host to suffer For example, fleas feed on dog's blood and live on them but the dog receives no benefits in return Tapeworms are parasites that live inside the small intestines of their hosts. These worms have no digestive system and absorb the products of digestion from their hosts. They release eggs in the faeces which can infect other hosts. The host loses nutrition and can suffer from diarrhea, vomiting and weight loss. Parasites are adapted to receive the maximum benefit from their host without killing them. For example, tapeworms have strong suckers so they can attach to the lining of the small intestine. They are thin and flattened and so have a large area for absorption of nutrients. They have a huge reproduction potential and release lots of eggs because the chance of the parasite finding another host is very small so most of the eggs will die

How are pests controlled on a farm?

Pests are organisms that reduce the yield of crop plants or stock animals. A pest can cause harm in two ways: 1. Lowering the amount by reducing growth - by damaging the leaves and reducing photosynthesis 2. Affecting the appearance or quality of a crop - making it unsuitable for sale Any type of organism can be a pest - plants, animals, bacteria, fungi or protoctists as well as viruses Pests can be controlled chemically by killing them using pesticides: 1. Herbicides kill plants such as weeds 2. Insecticides kill insects 3. Fungicides kill fungi 4. Molluscicides kill snails and slugs Pests are only a problem when presented in a big number so the farmer needs to decide whether the increase in income due to higher yield after using pesticide will be higher than the cost of the pesticides

Find the population size using this capture-mark-recapture example: Ten animals were trapped, marked and released. Two days later, 20 animals were trapped. Five of these were found to be marked.

Population size = (10 × 20) ÷ 5 = 200 ÷ 5 = 40

How to draw pyramids of biomass

Pyramids of biomass must be drawn with: 1. Bars equally spaced around the midpoints 2. Bars touching 3. Bar for the producer at the bottom 4. Length of each bar proportional to the amount of biomass available

How can rapid eutrophication be made less likely?

Rapid eutrophication is less likely when farmer use organic fertilizer (manure) since the organic nitrogen containing compounds are less soluble and so are leached less quickly from the soil

What is fish farming and what are the pros and cons?

Recently, the demand for fish has increased and the earth's stock of various fish species has gone down The farming of fish and shellfish (aquaculture) is the fastest growing area of animal food production Not all of the farmed fish is for humans; about one quarter is for making animal feed The fish are kept in densely stocked tanks or enclosures in rivers and lakes or in sea cages. Water is pumped through filtration units to remove waste products of the fish. PROS: 1. The water quality can be monitored. For example, the temperature, oxygen levels, water clarity and amount of chlorophyll in the water are measured. Chlorophyll - a high concentration of chlorophyll often reflects a high concentration of other nutrients such as nitrogen and phosphorous (usually as a consequence of run-off fertilizer). These conditions are ideal for the growth of algal blooms which then die and deplete the oxygen supply in the water, killing fish. Therefore, the chlorophyll levels in the water can be monitored to warn about algal blooms Air can be pumped into the enclosures to increase the amount of dissolved oxygen, increasing the fish's respiration and therefore the amount of energy they can use to create new cells and increase their biomass 2. The diet of the fish can be controlled in both its quality and frequency 3. Enclosing fish protects them against predators and parasites (pesticides can be used) 4. Small fish can be eaten by larger fish so the fish are regularly sorted by size and placed into different cages or tanks 5. Selective breeding can be used to improve the quality of the fish.for example, they are bred to produce faster growth and to be more "placid" (less aggressive) than wild fish CONS: 1. The potential for the spread of disease is greater than normal because the animals live so close together and antibiotics are therefore used to treat the fish. However, the antibiotics may not have degraded by the time the fish are eaten by humans, adding to the problem of antibiotic resistance in bacteria 2. Fish farms can also cause pollution problems since the organic material from animals' faeces and from food pellets can contaminate the waters outside the fish farm and cause eutrophication in the water 3. The pesticides used to kill fish parasites may be highly toxic to other non-harmful species of invertebrates 4. There is strong evidence that fish farming has a negative effect on wild fish stocks since carnivorous species like salmon and sea bass are made with pellets made from other fish. This means that less marketable wild fish species such as herring and sardines are used as fodder

What is sewage?

Sewage is wet waste from houses, factories and farms In developed countries, where large-scale sewage treatment takes place, industrial and agricultural sewage is usually dealt with separately from household sewage. Household sewage consists of: 1. Wastewater from kitchens containing dissolved organic and inorganic chemicals such as soaps and detergents 2. Wastewater from bathrooms containing urine and faeces It is carrie data in pipes called sewers to be treated before it enters waterways such as rivers or the sea

Why has the human population increased?

Since humans have first appeared on Earth, our numbers have grown dramatically. This is because, unlike other species, we have not adapted to one specific environment but have changed many environments in order to suit our needs. Each year, we have a net increase of about 75 million people and graphs showing the increase in population are exponential. Many organisms develop in this way when they have sufficient resources. Population has increased due to: 1. Better health care- people live longer 2. New medicines- people don't die of previously fatal diseases 3. Farmers can produce more food using new breeds and equipment

How is sulfur dioxide produced?

Sulfur dioxide is formed when fossil fuels are burned, and combines with water droplets in the air. it can be carried for hundreds of miles in the atmosphere before falling as acid rain. Rain normally has a pH of about 5.5 because of the carbon dioxide dissolved in it. Both sulfur dioxide and nitrogen oxides dissolve in rainwater to form a mixture of acids, including sulfuric acid and nitric acid. As a result, the rainwater is more abiding than normal rain: 1. Natural causes such as volcanic eruptions and lightning as well as human causes such as burning fossil fuels contribute to the levels of sulfur dioxide and nitrogen oxides 2. Water vapor from clouds combines with these gases to make sulfuric and nitric acids 3. This results in acid rainfall which causes: a) Acidification of soil - leaching or percolating of some ions into lakes kills fish and root hair cells are less effective at absorbing minerals so tree growth is slowed b) Acidification of lakes - death of bacteria/algae and death of fish/amphibian eggs which causes changes in the ecosystem c) Death of conifers Lichens are small moss-like organisms and have varying levels of tolerance to sulfur dioxide. In some countries, patterns of lichen growth can be used to monitor the level of pollution by sulfur dioxide. The different lichens are called indicator species as they indicate the different levels of sulfur dioxide pollution: Zone 1 - the orange crusty lichen (Xanthoria) indicate high levels of sulfur dioxide Zone 2 - leafy lichens on stone but not on trees indicate moderate levels of sulfur dioxide Zone 3 - shrubby lichens on trees indicate very low levels of sulfur dioxide Zone 4 - Usnea (feathery) lichens on trees indicate clean air

What is biodiversity?

The amount of variation shown by species in an ecosystem is called its biodiversity and can be measured by: 1. The species richness - the number of different species present 2. The relative abundance - how much there is of each species in comparison to each other For example if two communities contain the same number of species but one community is dominated by a certain species, the one with the most even number will have a higher biodiversity

What is the yield of a crop or stock animal?

The amount produced for sale

What abiotic factors affect organisms in an ecosystem?

The distribution and abundance of organisms in an ecosystem is affected by abiotic factors (non living): 1. Light intensity Some plants have evolved for optimum growth in bright sunlight (such as cacti which have evolved to the light intensity in the desert) whilst others have evolved to grow in the shade (such as orchids which grow on trees in the rainforest and have evolved for optimal growth in darker conditions). Therefore, if you put the plant in an area with the wrong light intensity it will not grow well 2. Temperature Both animals and plants have evolved to grow healthily at their optimum temperatures. For example, a polar bear couldn't survive in warmer conditions and cacti/orchids couldn't survive in colder conditions 3. Moisture levels Different organisms thrive in different moisture levels depending on where they originated. Succulents, which originated in the desert, cannot survive in water-logged soils. Their roots are unable to respire, they rot and the plant dies. On the other hand, pitcher plants originated in bogs and grow best when moisture levels are high 4. Soil pH content The pH of soils can have a big impact on the plants that are able to grow in them . For example, azaleas grow best in acidic soils and die quickly if planted in alkaline soils. On the other hand, clematis prefer alkaline soils. Hydrangea can grow in both. Hydrangeas are unusual because their flower color changes in different soils; in alkaline soil they are blue, in acidic soil they are pink 5. Soil mineral content Many plants require high levels of minerals to grow well; magnesium for example is used to produce chlorophyll. Plants with unnaturally yellow leaves may have a magnesium deficiency. Carnivorous plants, such as pitcher plants, have evolved to catch insects to supplement the low levels of minerals found in the soils in which they grow 6. Wind intensity and direction The strength of the wind and its direction has a big impact on where organisms are found within ecosystems. Many organisms prefer sheltered locations. Plant seeds are more likely to settle and germinate in these areas, and animals which depend upon the plants will most likely live close to where they grow. The strength of wind can also affect the growth of individual organisms 7. Carbon dioxide levels for plants Carbon dioxide is a reactant in photosynthesis which means that is is essential for plants to survive. Farmers can release carbon dioxide within their greenhouses for a higher crop yield. Woodlands often have higher carbon dioxide levels than grasslands so many plants living in open areas have evolved to overcome the shortage of carbon dioxide 7. Oxygen levels in aquatic environments Oxygen from the air and oxygen produced by aquatic plants dissolves in water. Without this, aquatic animals would suffocate which is a problem since polluted rivers have low levels of oxygen. This means that only certain species can survive there 8. Air pollutants Some species cannot survive if there are certain concentrations of air pollutants 9. Salt content Salinity affects whether certain creatures are able to survive. Freshwater creatures cannot live in saline conditions because it affects how fluid passes in and out of their body 10. Flow rate

How has the growth of the human population changed our demands on the environment?

The large size of our population todays means that we affect the environment much more significantly and make increasing demands for: 1. Food to sustain 2. Materials to build 3. Fuel to heat and power 4. Space to build 5. Space to dump As our numbers have grown, our sophistication of technology has grown too. Whereas early humans made tools from materials readily at hand, today's technology involves much more complex processes meaning that we produce increasing amount of pollutants.

How do carbon dioxide as well as other gases impact global warming?

The levels of carbon dioxide have been increasingly rising, particularly over the last 100 years due to the use of fossil fuels. It has been made even worse due to deforestation since rainforests absorb vast quantities of carbon dioxide and produce equally large amounts of oxygen. Therefore, extensive deforestation means that less carbon dioxide is being absorbed. In any one year, there is a peak and a trough in the levels of carbon dioxide in the atmosphere. In the autumn and winter, trees lose their leaves. Without their leaves, they cannot photosynthesize and so don't absorb carbon dioxide but still respire and so produce carbon dioxide. In the spring and summer, new leaves and brighter sunlight lead to trees photosynthesizing faster than they respire. As a result, they absorb more carbon dioxide from the atmosphere than they produce, so the level decreases. however, because there are fewer trees overall due to deforestation, it doesn't quite return to the low level of the previous summer. The increased levels of carbon dioxide and other gases contribute to global warming, or the enhanced greenhouse effect. Although the greenhouse effect occurs naturally, and the temperature on Earth would be unsustainable without it, it has been increased to a dangerous level. Carbon dioxide, water vapor, methane, nitrous oxide and chlorofluorocarbons are all greenhouse gases. Most greenhouse gases occur naturally whilst others like CFCs are man-made 1. Short wavelength infrared radiation from the Sun reaches the Earth 2. Some is absorbed by the Earth's surface and emitted again as longer-wavelength radiation 3. The greenhouse gases then absorb and re-emit some of this long-wavelength radiation which would otherwise escape into space. This then heats up the surface of the Earth The problem is that human activities are polluting the atmosphere with extra greenhouse gases such as carbon dioxide. therefore, the Earth's surface temperature is rising due to an increased greenhouse effect

How can fertilizers replace lost nitrogen?

There are organic and inorganic fertilizers: Organic fertilizers such as farmyard manure are made from the faeces of farm animals mixed with straw. The nitrogen compounds are decomposed to become ammonia. Then the ammonia is converted into nitrates by nitrifying bacteria Inorganic fertilizers are simply inorganic compounds such as potassium nitrate or ammonium nitrate which are formulated to provide a specific amount of nitrate (or another ion) when used Evaluation: Farmyard manure adds some nitrogen to the soil but since it is made from livestock faeces and indigestible fodder, it can only replace a portion of the lost nitrogen Therefore, most farmers apply inorganic fertilizers to replace the nitrates and other mineral ions lost. However, this can also lead to pollution problems and doesn't improve the soil structure in the way that organic fertilizers can, because it doesn't contain any decaying matter Another way to replace lost nitrates is to grow a legume crop in a field one year in four: These have nitrogen fixing bacteria in the nodules on their roots These bacteria convert nitrogen gas in the soil and air into ammonium ions Some of this is passed to the plant, which it uses to make proteins At the end of the season, the crop is ploughed back into the soil Decomposers convert the nitrogen in the proteins to ammonia This is then oxidized to nitrate by nitrifying bacteria and made available for next year's crop

What is deforestation

Tropical rainforests form a belt around areas of the Earth near the equator in South America, Africa and Indonesia. They have very high biodiversity but are rapidly being destroyed by humans. Deforestation is a consequence of the enormous growth of the human population and every year thousands of hectares are cut down to provide wood for building and other purposes, or to clear the land for farming which is often done using the slash and burn method (where trees are cut down and burned)

How does energy flow through an ecosystem?

Unlike food chains, energy transfer diagrams focus less on the individual organisms and more on the energy passed between trophic levels in the whole ecosystem: 1. Light energy from the sun is fixed into chemicals such as glucose and starch in plants during photosynthesis 2. Respiration releases energy from organic compounds such as glucose which is used in almost all other biological processes (reproduction, excretion etc.) 3. If the energy released in respiration is used to produce new cells, then it remains fixed in the molecules of that organism and can be passed onto the next trophic level through feeding 4. If the energy released in respiration is used for metabolic processes then it will, once used, escape as heat from the organism In a typical energy flow diagram: Radiant energy = light Fixed energy = stored chemical energy 1. Light energy enters from the sun and some is reflected. This is known as radiant energy. 2. Producers use this light energy in photosynthesize to produce glucose. This glucose is then used to release energy in respiration; some of which is used to make new cells (in which case the energy is fixed as chemical energy in the carbohydrate, fat and protein molecules of that organism and can be passed onto the next level through feeding) and some of which is lost as heat from metabolic processes. When the plant dies, any energy remaining in it will be passed to decomposers. 3. Primary consumers will break down the carbohydrate, fat molecules of the plants to respire and release energy. They will in turn store the energy when making new cells or lose it as heat during metabolic processes. They will also lose some of the energy in excreted waste products and digested faeces. When the primary consumer dies, any remaining energy will be passed to the decomposers. 4. Secondary consumers will use energy fixed in the molecules of the primary consumer to respire and release energy. They will in turn store the energy when making new cells or lose it as heat during metabolic processes. They will also lose some of the energy in excreted waste products and digested faeces. When the secondary consumer dies, any remaining energy will be passed to the decomposers. 5. Finally, decomposers take in energy from all the excreted products and dead organisms. Detritus from the organisms is ingested by decomposers which then digest them partially and after extracted some of the energy in the food to run their metabolism, excrete the remainder in the form of simple organic molecules. The reason that energy flow through decomposers is a straight passage is that partially digested waste from one decomposer can be continued to be broken down by another, leaving simple compounds such as water, carbon dioxide and humus which is organic material incorporated into soil. Most of the energy is lost as heat during the decomposer's metabolic processes. By the last trophic level, there isn't enough energy to support any more organisms. However, in some marine food chains, there are six trophic levels due to the huge amount of light energy reaching the surface waters

How can we measure biodiversity?

Using Simpson's index: Diversity index = 1 - (the total number of individuals of a particular species / the total number of individuals of all species)² or more simply D = 1 - (n/N)² 1. You calculate n/N for each species, square each of these numbers and then sun all the squares. Subtracting this value from one fives you D 2. Values of D range from 0 - 1 where 0 represents a low diversity and 1 represents a high diversity

What is the water cycle?

Water is a key compound for life on earth and all living organisms need it. Some can survive for long periods without it but will eventually die. 1. Evaporation - water turns from a liquid into a glass due to energy from the sun 2. Condensation - after evaporation, water can cool and convert from gas to liquid, often forming clouds 3. Transport - water within clouds can be blown many miles by strong winds and transported to other areas 4. Precipitation - rain, snow, hail and sleet fall from the sky 5. Surface runoff - much water is absorbed into the ground after precipitation but if a large volume falls or the ground is already wet some water can run along the ground. 6. Percolation- the water flows through soil and porous rocks due to gravity and makes its way to water bodies and plants 7. Infiltration - water is absorbed into the ground and can be stored within underground rocks called aquifers 8. Transpiration - plants need to maintain a constant stream of water to their leaves for transport and support. They allow some water to evaporate as water vapor from their leaves so it is continually pulled from the soil (high to

What are the problems with deforestation?

What are the problems of deforestation? 1. Slash and burn adds to the carbon dioxide in the atmosphere and contributes to global warming as wall as removing trees which would have otherwise absorbed carbon dioxide for photosynthesis 2. Destruction of habitats and reduced biodiversity 3. Reduced soil quality since there are no trees and other plants to return minerals to the soil when they die and no tree roots to hold the soil together. Therefore, crops planted in forested areas rapidly use up minerals from the soil and rain easily washes the minerals out 4. The soil is exposed due to lack of tree cover (canopy) and is blown or washed away. Soil may be washed into rivers, causing rising water levels and flooding of lowland areas 5. Deforestation can produce climate change since trees are an important part of the earth's water cycle and return water vapor from the soil into the air through transpiration. Cutting down forests will upset the water cycle 6. In the past rainforests have been a valuable source of medicines as well as species of plants that have been cultivated as crops. There are probably many undiscovered drugs are crop plants that will be lost through deforestation

How is carbon monoxide produced?

When substances containing carbon are burned in a limited supply of oxygen, carbon monoxide is formed This happens when petrol and diesel are burnt in vehicle engines. Exhaust gases contain significant amounts of carbon monoxide It is a dangerous pollutant because it is colorless, odorless and tasteless. It can be fatal since hemoglobin binds to it more strongly than oxygen. therefore, if a person inhales carbon monoxide for a period of tie, more and more hemoglobin becomes bound to carbon monoxide so it cannot bind with oxygen. the person may lose consciousness and eventually die as a result of a lack of oxygen reaching the cells (meaning that organs can't respire and so stop working)

How can farmers improve yields from crop plants?

a) = how it is controlled b) = reason for controlling it 1. Soil ions (e.g. nitrates) a) adding fertilizers to the soil or growing in a hydroponic culture (growing plants in nutrient solutions) b) extra mineral ions can be taken up and used to make proteins and other compounds for growth 2. Soil structure a) ploughing through fields to break up compacted soil; passing manure to improve drainage and aeration of heavy, clay soils b) good aeration and drainage allow better uptake of mineral ions by active transport and water 3. Soil pH a) Adding lime to acidic soils; few soils are too alkaline b) Soil pH can affect crop growth as unsuitable pH reduces uptake of mineral ions 4. Carbon dioxide, light and heat a) these can't be controlled for field crops but in a glasshouse or polytunnel they can be altered to maximize yield of crops. Burning fuels produces heat and carbon dioxide. b) all of these can limited the rate of photosynthesis and the production of the organic substances needed for growth if there isn't enough

How can we calculate the efficiency of an energy transfer?

energy transferred to next trophic level ÷ total energy in the previous trophic level × 100 For example, if the energy in the producer is stated as 4500 kcal and the rabbit, who is the primary consumer, receives 500 kcal during the energy transfer: (500/4500) x 100 = 11%

How can we calculate the efficiency of a biomass transfer?

percentage energy transfer = biomass in higher trophic level/biomass in lower trophic level