Everything needed for the OCR gateway exam board

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- Kingdom, Phylum, Class, Order, Family, Genus, Species

- Natural classification - it is based on the evolutionary relationships and genetic similarities between organisms

- Artificial classification - it is based on appearance rather than genes and is used to identify organisms

- Genus is a group of closely related species that can be interbreed to produce fertile offspring

- Classification develops overtime - Newly discovered species might not fit into the categories - DNA sequencing allows us to see genetic differences between different groups as we may find that some species are not as closely related as first thought

- Advances in ICT have allowed us to draw evolutionary trees that show the relation of animals and ancestors

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- A species is a group of organisms which can interbreed to produce fertile offspring

- Asexual reproduction - some organisms such as bacteria reproduce asexually which is where an organism reproduces by making a copy of itself - there is no interbreeding with another organism so they do not fit the definition of the species

- Hybrids - If you mate a female from one species and a male from another species you get a hybrid that is unable to reproduce so they are not a new species therefore it is difficult to classify them

- Evolution is a continuous process - organisms evolve over time so the way they are classified may have to change

- Binomial system gives everything a two-part name - Humans are known as Homo sapiens where Homo is the genus and they belong to sapiens which are the species

- Closely related species have recent common ancestors e.g. Whales and dolphins

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Biomass and Numbers

- 100kg of pear tree --> 5kg of aphids --> 1.5kg of ladybirds --> 0.5kg of partridge

- Each bar on the pyramid of biomass shows the mass of living material so it is the weight of that organism if it was put all together

- The pear tree would go at the bottom because it is bottom of the food chain

- They are nearly always pyramid shaped because biomass is lost at each stage

- Pyramids of numbers show the number of organisms in the food chain

- Pyramids of numbers are not always a pyrimid shape

- There is only a thin bar at the bottom because only 1 pear tree feeds 3000 aphids

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Energy transfer and energy flow

- Energy from the sun is the source of energy for almost all life on earth

- The energy is lost at each stage and used for staying alive e.g. Respiration

- Energy is lost in the food chain through excrement, respiration and urine

- You hardly ever get food chains longer than 5 tropic levels because so much energy is lost at each stage so it cannot continue any longer than that

- Efficiency = energy available on the next level / energy that was available to the previous level X 100

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Organisms compete to survive

- In order to survive and reproduce organisms must compete for resources

- A species' ecological niche is how it fits into its ecosystem. It depends on things like where the individuals live and what they feed on

- There are two types of competition between organisms:

= Interspecific competition - is where organisms compete for resources against individuals of another species

= Intraspecific competition is where organisms compete for resources against individuals in the same species

- Intraspecific competition has a bigger impact on organisms than interspecific competition which is because they have exactly the same needs


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Populations of prey and predators

- The population of species depends on the amount of food available

- If the population of prey increases so will the population of predators but when the population of predators increase the population of prey decreases

- Predator-prey cycles are always out of phase and it takes a while for the populations to respond

- Parasites live off a host and take what they need to survive without giving anything back which often harms the host e.g. Tapeworms - they absorb lots of nutrients from the host causing them to suffer malnutrition and Fleas - are parasites that live off dogs

- Mutualism is a relationship where both organisms benefit e.g. Cleaner species - oxpeckers live off the backs of buffalo and eat pests but get the protection from the buffalo and insects pollinating plants allow reproducing and it gives the insects nectar

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- Adaptations mean that organisms are more likely to survive

- Specialists - they are organisms that are highly adapted to survive in a specific habitat e.g. Giant pandas are adapted to only eat bamboo

- Generalists - they are organisms that are adapted to survive in a variety of habitats e.g. The black rat can live in forests, cities and farmland

- Specialists are better suited to a stable environment but generalists are better suited to changing environments

- Biochemical adaptations to extreme conditions:

= Extremophile bacteria live in very hot environments so they have the ability to survive in hot conditions (65'C) without denaturing

= Organisms that live in cold places have antifreeze proteins that interfere with the growth of ice thus stopping damage

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Adaptations to cold environments

- They have a thick coat or a layer of blubber to insulate the body and trap it in

- They have a small surface area to volume ratio which reduces heat loss

- Counter current heat exchange systems:

= Penguins have to stand on ice - blood vessels going to and from the feet carry blood that flows in different directions - the vessels pass close to each other so that heat transfer can happen and the feet remain cold but the rest of the body stays warm

- Penguins have the behavioural adaptation that they huddle to stay warm

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Adaptations to hot and dry environments

- Behavioural adaptations can increase heat loss and reduce heat gain - they often stay underground or in shaded areas - they are active and night when it is much cooler - they bath in water and as it evaporates it transfers heat from the skin to the surroundings

- Anatomical adaptations can increase heat loss - animals are often small to increase the surface area to volume ratio - large thin ears allow blood to flow closer to the surface of the skin so the heat is radiated to the surroundings - some animals only store fat in one area of their body e.g. Camels

- Dry environments - some desert plants = small rounded shape giving small surface area to volume ratio to minimise water loss, a thick waxy layer and spines instead of leaves to reduce water loss, they store water in the stems to allow water when there is a drought, they have shallow yet extensive roots to ensure water is absorbed quickly over a large area - some desert animals = specialised kidneys that allow them to very concentrated urine with a low water content, no sweat glands preventing water to be lost through sweat and they spend lots of time underground where the air contains more moisture

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Evolution and Charles Darwin

- Charles Darwin came up with the theory of evolution:

= He knew that in a species there is a wide variation so they have to compete for limited resources

= He concluded that the best adapted organisms would be more successful (survival of the fittest)

= The better adapted organisms are more likely to reproduce and pass on the successful genes to the offspring

= Less well adapted organisms are less likely to survive and reproduce so they are less likely to pass on their genes onto the next generation

= When successful adaptations become more common and the species changes thus it evolves

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Natural selection and speciation

- Darwin could not give a good explanation because DNA was not discovered until 50 years after his theory was published however we now know that adaptations are controlled by genes

- When species adapt so much they become a new species and the process is called speciation

- They change so much that they cannot produce fertile offspring

- Reproductive isolation can be caused by geographical isolation: - a physical barrier divides a population of a species so the two new populations are unable to mix, different mutations create new features in the two groups of organisms, if the natural selection is benefitual it spreads through the population, because the conditions are different for the two populations so the benefitual features will be different for each population, eventually the two populations will be so different that they will no longer be able to breed together to produce fertile offspring therefore a new species will have been created

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Theories of evolution

- Not everyone agreed with Darwin: - it went against religious beliefs, he couldn't explain it and there wasn't enough evidence to convince many scientists

- Lamarck had a conflicting theory of evolution: - he argued that is a characteristic was used a lot by an animal it would become more developed and he thought if Giraffes kept eating of tall trees their necks would get longer and the offspring would have this characteristic as well

- His theory was rejected because acquired characteristics don't have a genetic basis so they are unable to be passed onto the next generation

- Darwin's theory is now accepted: - the theory has been debated and tested independently by a wide range of scientists and no one was able to prove the theory wrong - the theory offers a plausible explanation for many observations of plants and animals e.g. Their physical characteristics and behavioural patterns

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The carbon cycle

- The whole carbon cycle is powered by photosynthesis

- In photosynthesis plants convert the CO2 in the air into sugars. plants can then incorporate this carbon into other carbohydrates as well as fats and proteins

- Eating passes the carbon compounds in the plant along to animals in a food chain or web

- Both plant and animal respiration while the organisms are still alive releases CO2, back into the air

- Plants and animals die and decay. They are broken down by bacteria and fungi in the soil. The composers release CO2 by respiration as they break down the material

- Over millions of years the dead plants and animals form fossil fuels like coal and oil. When they are burnt it is then put back into the air

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- Decomposition is slower in waterlogged and acidic soils and takes longer to break down nutrients

- The bacteria and fungi that decompose the material need oxygen in order to respire and produce energy. Water logged soils don't have very much oxygen so the decomposers have less energy and work more slowly

- It takes longer in acidic soil than in neutral soil because the extreme of the PH slows down the reproduction of decomposers or kill them

- Carbon is recycled in the sea: - millions of species of marine organisms make shells made of carbonates, when the organisms die the shells fall to the ocean floor and eventually form limestone rock, the carbon in the rocks returns to the atmosphere as CO2 during volcanic eruptions or when the rocks are weathered down, the oceans can absorb large amounts of CO2 acting as huge stores of carbon called carbon sinks

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The Nitrogen cycle

- The atmosphere is 78% nitrogen and is very unreactive so it can't be used directly by plants and animals

- Nitrogen is needed for making proteins for growth

- Plants get their nitrogen from the soil so the nitrogen in the air is turned into nitrates before plants can use it. Nitrogen compounds are then passed along food chains and webs as animals eat plants

- Decomposers - they are bacteria and fungi in the soil and they break down proteins in rotting plants and animals and urea in animal waste into ammonia. This returns the nitrogen compounds to the soil so the nitrogen in these organisms is recycled

- Nitrogen fixation is the process of turning nitrogen into nitrogen compounds in the soil which plants can use. There are two main ways that this happens: - Lightening = there is so much energy in lightening that's enough to make nitrogen react with oxygen in the air to give nitrates - nitrogen fixing bacteria = in roots and soil

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The nitrogen cycle continued

- There are 4 different types of bacteria involved in the nitrogen cycle:

= Decomposers - decompose proteins and urea and turn them into ammonia

= Nitrifying bacteria - turn ammonia in decaying matter into nitrates

= Nitrogen fixing bacteria - turn atmospheric N2 into nitrogen compounds that plants can use

= Denitrifying bacteria - turn nitrates back into N2 gas and has no benefit to living organisms

- Some nitrifying bacteria live in the soil whereas others live in nodules on the roots of legume plants. This is why legume plants are good at putting nitrogen back into the soil. The plants have a mutualistic relationship with the bacteria - the bacteria get food from the plant, and the plant gets nitrogen compounds from the bacteria to make into proteins

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Human impact on the environment

- The human population is increasing so it is putting pressure on the environment

- Global warming = Fossil fuels are coal, oil and natural gases. When they are burnt they release lots of carbon dioxide. The greenhouse gas traps heat in the atmosphere so the temperature increases. If it continues the sea levels will rise, weather systems will be less predictable and agricultural output. Companies are now measuring the amount of greenhouse gases so they can release their emissions.

- Acid rain = When fossil fuels are burnt they release sulphur dioxide. The sulphur dioxide reacts with the water in the atmosphere to form sulphuric acid which falls as acid rain and kills soils and trees. Acid rain can cause lakes to become more acidic which has a severe effect on the lakes ecosystem. Many organisms are sensitive to changes in PH and cannot survive in more acidic conditions so many plants and animals will die. Acid rain also damages limestone.

- Ozone depletion = CFC's used to be in aerosols and fridges. They break down ozone in the upper atmosphere which allows harmful UV rays to reach the earth’s surface. Being exposed to Uv rays will increase the chance of skin cancer. It also kills plankton in the sea which could have a massive effect on the ecosystem because plankton are at the bottom of the food chain. Scientists predict that fish levels will drop meaning among other things, less food for us to eat.

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Human impact on the environment 2

- Indicator species tell you if an area is polluted or not. Lichens are used to monitor air quality - they're damaged by pollution. The cleaner the air, the greater the diversity of lichens that survive. Mayfly larvae are used to monitor water quality - they can't survive in polluted water. The cleaner the water the more may fly larvae that survive. Other species have adapted to live in pollutes areas such as water lice, rat tailed maggots and sludge worms all indicate polluted water. However rat tailed maggots and sludge worms indicate a very high level of pollution.

- There are a couple of ways that indicator species can be used to measure pollution: =simple survey to see if the species is present or absent from an area - quick to measure but not good for telling you how polluted the area is

= Counting the number of times the indicator species occurs in the area will give you a numerical value allowing measurements from different areas to be compared so you can see how polluted the area is


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Human impact on the environment 3

- You can measure pollution exactly:

= Sensitive instruments can measure the concentration of chemical pollution

= Satellite data can be used to indicate pollutant levels

- Indicator species - advantages = quick, cheap, easy and now expensive equipment is needed. Disadvantage = factors other than pollution can effect it so it is not always reliable

- Non living methods - advantages = reliable, numerical data that is easy to compare and the exact pollutants can be identified. disadvantages = it requires more expensive equipment and trained workers

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Species becoming extinct

- Species are at risk of being extinct when:

= The number of habitats - it's hard for organisms to find resources like food and shelter

= The number of individuals - if there is only a few of the species left it will be difficult to find mates so there will not be very much genetic variation in the species

= Genetic variation - This is the number of different alleles in a population. If genetic variation is low then a species is less likely to be able to adapt to challenges in the environment or survive the appearance of a new disease


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Conservation programmes

- Conservation programmes:.

= Genetic variation - the species needs enough genetic variation so that they can survive the arrival of a new disease and to cope with environmental change

= Viability of populations - the population should be able to reproduce so they must contain both males and females of reproductive females

= Available habitats - there should be plenty of available habitat to live in. It is especially important when the organisms are specialists

= Interaction between species - It is important that the react with other species as they would in the wild eg. they should be able to hunt prey

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Conservation programmes benefiting wildlife and hu

- Protecting the human food supply - over fishing has reduced fish stocks in the worlds oceans. We need to conserve them to ensure the next generation will have fish to eat

- Ensuring minimal damage to food chains - if one species becomes extinct it will effect the rest of the food chain so conserving one species may save an entire food chain

- Providing future medicines - many medicines that we use today come from plants so if we let deforestation happen we may miss out on benefitual medicine

- Cultural aspects - individual species may be important in a countries heritage e.g. The bald eagle in the USA

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Sustainable development

- As the human population increases: we need more food, we use more energy and produce more waste

- Sustainable development = providing for the needs of today’s increasing population without harming the environment

- What is being done to promote sustainable development = fishing quotas to prevent some types of fish becoming extinct in certain areas = to make the production of wood and paper sustainable there are laws insisting that logging companies plant new trees to replace those that they have felled

- Case study - Whales - They have commercial use when they are both alive and dead. They are a tourist attraction, whale meat and oil can be used in cosmetics however some species of whales are now endangered. The IWC has restricted whaling whilst a few whales can be killed for scientific research. It is hard to check that countries are keeping to this agreement. Some whales are kept in captivity and there are different views - whales don't have enough space as they are used to entertain people. Captive breeding programmes allow whales to be bred in numbers and released into the wild. Research of captive whales allows us to understand their needs between however we still don't fully understand them e.g. their migration patterns and how they survive in very deep water

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