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Success criteria I can define terms associated with ecosystems. I can construct and describe food chains/webs. I can describe pyramids of numbers. I can describe the two types of competition. Producer & Consumers All organisms in our world are connected to each other & termed 1. Producers 2. Consumers Producers Producers make their food by a process called photosynthesis. Food Chain • The way in which organisms interact can be shown by a food chain. Food Chains • The arrows show the direction of energy flow. (primary consumer) (secondary consumer) The 1st consumer is called the primary consumer The 2nd consumer is called the secondary consumer Energy loss in Food chains • Only 10% of energy is passed on to next level in a food chain. Energy loss in Food chains Most of the energy is lost as: A) Heat B) Movement C) Undigested material Calculation 1000 units of energy in grass – how much energy does the owl receive? Calculation 1000 units of energy in grass – how much energy does the owl receive? 1000 100 10 1 Key word Definition Consumer Omnivore Carnivore Herbivore Prey Predator Producer Eats another organism Eats animals and plants Only eats other animals Only eats plants Gets eaten by the predator Feeds on the prey Makes its own food by photosynthesis Food webs Animals usually eat many different things and are involved in lots of different food chains. These more complicated feeding relationships can be shown in a food web. How many simple food chains can you see in this food web? Analysing food webs What would happen to the _________ if the ________ died out? Increase or decrease – why? There is a lot of competition for resources among organisms in a food web. Interspecific vs. Intraspecific Between organisms of different species for similar resources. Between organisms of the same species for the same resources. There is a lot of competition for resources among organisms in a food web. Animals compete for... • Food • Mates • Habitats Plants compete for... • Nutrients • Water • Space 1. Pyramid of biomass BLACKBIRD LADYBIRD GREEN FLY ROSE BUSH Shows the total mass of organisms at each stage of a food chain 2. Pyramid of Energy BLACKBIRD LADYBIRD GREEN FLY ROSE BUSH Shows the total energy received by organisms at each stage of a food chain 3. Pyramid of Numbers Show the total number of organisms at each stage of a food chain 1 fox Small numbers of large organisms 30 Rabbits 100,000 blades of grass Large numbers of small organisms Problems with Pyramids of Numbers What if tree is the producer? Oak tree greenfly wasp blue tit What if insects are the top consumer? Grass zebra lion flea Oak tree Greenfly Finch Pyramid of numbers = not always a pyramid! L Success criteria I can define terms associated with ecosystems. I can construct and describe food chains/webs. I can describe the two types of competition. I can describe pyramids of numbers/energy/biomass. The Nitrogen Cycle About 78% of the air consists of nitrogen gas. All living things need nitrogen to make proteins (e.g. enzymes, hormones, antibodies, etc.). Plants and animals cannot use nitrogen gas directly. Plants absorb it in the soil in the form of nitrate. Animals then eat plants or other animals to get their supply of nitrogen. Excretion and death Nutrients in living organisms Absorption by living things Nutrients dead bodies and waste Nutrients in the environment available for use Decomposition by bacteria and fungi Nitrogen Cycle – 4 main stages 1. Decomposition – fungi break down dead organisms and waste, releasing ammonia into the soil. Nitrogen Cycle – 4 main stages 2. Nitrification - nitrifying bacteria convert ammonia to nitrites, and then nitrites into nitrates that can be used by a plant. Nitrogen Cycle – 4 main stages 3. Denitrification – denitrifying bacteria deprive the soil nitrates by breaking down the nitrates and releasing nitrogen gas into the air. Nitrogen Cycle – 4 main stages 4. Nitrogen fixation – nitrogen fixing bacteria absorb nitrogen gas and ‘fix’ it back into nitrate. Nitrogen fixing bacteria can either be found in the soil or in the root nodules of legume plants. 3 Main Bacteria Nitrifying Bacteria Ammonia Nitrite Nitrate Denitrifying Bacteria Nitrate Nitrogen gas Nitrogen Fixing bacteria Nitrogen gas nitrate/protein Which letter(s) shows; 1. The decay of dead material B 2. Nitrification C, D 3. Nitrogen fixation G Complete the table below by filling in a description of each stage. Stage Absorption Eating Decomposition Bacteria involved? None None Decomposing bacteria or fungi Nitrification Nitrifying bacteria Denitrification Denitrifying bacteria Nitrogen fixation Nitrogen fixing bacteria Description Success criteria I can describe what a biome is. I can name several types of biomes. I can state the effect of abiotic factors on the distribution of biomes. Biodiversity Variety and abundance of all living organisms. Importance of biodiversity; Variety of organisms is important so that they can adapt to changing environment conditions. Habitat Where the animals/plants live. Community All the organisms living together. Population The number of ONE species living in an area. Ecosystem An area made up of living & non living parts. What is a biome? Large ecosystem consisting of distinctive: a) Flora (plants) b) Fauna (animal) c) Climate Main factors affecting global distribution of biomes: Rainfall Temperature Success criteria I can describe the main factors affecting biodiversity. I can list several biotic and abiotic factors. I can describe the sampling techniques used to measure various biotic and abiotic factors. I can explain how to minimise possible sources of error when carrying out sampling techniques. Factors affecting biodiversity 1. Biotic (living) 2. Abiotic (non-living) 3. Human impact (what we do) Biotic factors Living factors affecting biodiversity; 1. 2. 3. 4. 5. Predation Grazing Disease Competition Food availability Predator/Prey Graphs Abiotic factors Non-living factors affecting biodiversity; 1. 2. 3. 4. Temperature Light intensity pH Moisture Human Impact Biggest factor in reducing biodiversity and distribution of biomes. e.g. • • • • • • Over hunting Over fishing Habitat destruction (deforestation) Poaching endangered species Air pollution (from burning fossil fuels) Water pollution Sampling Techniques Techniques used to measure various biotic and abiotic factors in the environment. Animals 1. Pitfall traps 2. Tree beating Plants 1. Quadrats Quadrats Thrown at random (not placed down). Don’t count number of flowers, count number of squares the flower is in. Repeat for increased reliability. Errors with quadrats Not thrown randomly (throw randomly) Organisms wrongly identified (use key) Pitfall Trap (e.g. woodlouse) Hole dug level with ground. Covered with stones, leaves. Checked regularly. Errors with pitfall traps Hole not level with ground – insects won’t fall in. Trap not hidden – insects will avoid the trap. Not checked regularly – insects could eat each other. Tree Beating (e.g. spiders) Branch given few sharp taps at specific height. Small animals drop onto tray with raised edges below to stop insects crawling out. Repeat for more reliability. Errors with tree beating Insects fly out of bucket. (could use a bucket with rimmed edge) Insects do not fall into bucket. (use larger bucket) Abiotic sampling techniques 1. Light intensity 2. Moisture 3. pH 4. Temperature Light intensity Measured with a light meter. Hold the light meter arms distance away so that you don’t cast a shadow over it. Point at maximum light. Errors with light intensity Accidentally shading the light meter. Moisture or pH Measured with a moisture meter/pH meter. Push the probe into the soil and read the meter. Errors with moisture or pH Not wiping pH meter/moisture meter probes between readings. General rule; Results are made more reliable by taking many samples (REPEATING experiment). Line Transects Looking at the effect of an abiotic factor on the distribution of plant growth. Example; light intensity on plant growth Quadrat placed every meter – NOT THROWN RANDOMLY!!! Success criteria I can describe the purpose of a paired statement key. I can use a paired statement key to identify organisms. I can construct a paired statement key to allow others to identify unknown organisms. Identifying Organisms It’s all very well counting/collecting organisms, but not all of them will be familiar to us. To identify unfamiliar organisms, we would use a key. There are different kinds of key. Branching Key Animals No legs Legs 8 legs Spider More than 8 legs Centipede Shell Snail No shell Earthworm Paired Statement Keys Paired statement keys work in the same way as branching keys. At each stage you are given a choice. Make the appropriate choice and go to where you are asked to go. Again, if the organism is present, you should end up with a name for it. Success criteria I can describe a what a mutation is, and how they occur. I can give examples of advantageous, disadvantageous and neutral mutations. I can state the importance of variation. I can define and give examples of mutagenic agents. Mutation Random Change to DNA bases. Mutations are: Randomly Occurring Low frequency (ROLF) Mutation Types 1. Disadvantage (genetic disease) 2. Advantage (new variety of species) 3. Neutral Genetic Disease: Down Syndrome 3 copies of chromosome 21 (instead of just 2). Occurs in 1 in every 1,000 children born each year. Advantageous Mutations Mutations create variety (new alleles). Variation helps animals or plants cope with environmental change. Example: Peppered moth Neutral Mutations Changes in DNA bases that are neither beneficial nor detrimental to the ability of an organism to survive and reproduce. E.g. different coloured eyes Mutagenic Agents Increase the frequency of a mutation occurring. Examples include; 1. X-rays 2. UV radiation 3. Mustard gas 4. High temperatures 1. X-rays 2. UV radiation 3. Mustard gas Success criteria I can describe the 2 main types of adaptations, and give examples of each. I can describe Darwin’s Theory of Evolution. I can explain the term ‘survival of the fittest’. Adaptations Mutations (increased variety) allows organisms to adapt to be better suited to their environment/cope with environmental change. Most adaptations are either: Structural Involve specialized structures possessed by the organism. Behavioural Depends on the way the organism behaves. Adaptations of the desert rat Burrowing into sand when temperature is too high. Behavioural Large back feet help them to jump away from predators. Structural Adaptations of the cactus The leaves are reduced to spines in order to decrease the surface area for water loss. Vast root system to maximise water uptake. Structural Adaptations of the camel Rest during the day when the temperatures in the desert are very high. Behavioural Humps store fat which produces water when metabolised. Structural The theory of evolution states that evolution happens by natural selection. Key points: Individuals in a species show a wide range of variation. Individuals with characteristics most suited to the environment are more likely to survive and reproduce. The genes that allowed the individuals to be successful are passed to the offspring in the next generation. Darwin’s Theory of Evolution “Survival of the fittest” Natural Selection The organism best suited to the environment survive. Natural Selection There is natural variation in the population. Natural Selection Those with the selective advantage for survival increase in population. Natural Selection These organisms are able to breed and pass on their desirable genes. Natural Selection Organisms without the selective advantage die out. Likely exam question! Q. Explain the concept of “survival of the fittest”. (2) Natural Selection chooses organisms that have a SELECTIVE ADVANTAGE for survival who then reproduce & pass on successful alleles. Success criteria I can define the term ‘species’. I can describe the different stages involved in the process of speciation. I can state the importance of isolating mechanisms, and give some examples of different types. What is a species? A group of related organisms that interbreed & produce fertile offspring. Horses and donkeys are closely related, and look very similar, but they are members of different species. Horses mate with each other to produce young horses, which themselves will be able to mate (fertile). Donkeys can mate with each other to produce young donkeys, which themselves will be able to mate (fertile). If a donkey mates with a horse, they produce a mule, which is infertile and cannot mate to produce offspring. Fertile Fertile Infertile Speciation Creating a new species. Speciation – 3 stages 1. Isolating Mechanism 2. Mutations 3. Natural Selection New species formed! One species of organism. The species is split into 2 subpopulations, separated by an isolating mechanism. The isolating mechanism prevents gene flow across sub-populations. A random mutation (low frequency) occurs on one side of the barrier. Natural Selection chooses organisms that have a selective advantage for survival, who then reproduce & pass on successful alleles. A new species is formed. This new species cannot interbreed with the original species to produce fertile offspring (even if the barrier is removed). Types of Isolating Mechanisms 1. Geographical 2. Ecological 3. Reproductive Importance of isolating mechanisms Prevents gene flow (exchange of genes) between sub-populations. Free flow of genes between all population 4 Population 3 becomes extinct 1 Flow of genes only 1 to 2 3 2 1 2 4 Population 4 becomes isolated How many species? How many species? Isolating mechanism Common error in ‘isolating mechanism’ answer “the barrier separates different species”. Barriers separate groups of the same species, which then undergo mutation and natural selection until they become separate species. Past paper question A. B. C. D. Quick recap… 1. Isolation 2. Mutation 3. Natural selection Speciation! Just remember…… I’m a new species. Success criteria I can describe the advantages and disadvantages of intensive farming. I can explain the problems caused by pesticides and fertilisers. I can describe the role of indicator species in an environment. I can describe biological control and genetic modification. What’s the problem? Not enough food to feed everyone. Food Science Challenge Need to increase yield of crops grown. Solution? 1. Intensive Farming 2. Biological Control 3. Genetically Modified (GM) Crops Advantages of Intensive Farming Increased yield making food more affordable/available. Features of Intensive Farming Fertilisers Nutrients to help crops grow (nitrates). Pesticides To kill pests that eat crops. Problems with pesticides Pesticides aren’t broken down, so they build up at each stage of the food chain. This can be toxic for the predators at the top of the food chain. Problems with fertilisers Creates algae bloom in water. Disadvantage of fertilisers 1. Fertiliser washes into rivers from fields. 2. Increased algae bloom. 3. Increased bacteria as they feed on algae. 4. Decreased oxygen levels (all the bacteria use the oxygen for respiration). 5. Decreased biodiversity. Intensive Farming Summary 1. Algae bloom Deoxygenates water as bacteria that feed on algae use up oxygen and reduce biodiversity. 2. Pesticide build up (DDT) DDT builds up to toxic levels in food chains. Pesticide resistance. Indicator Species A species whose presence/absence indicates level of pollution in environment. Lichen only grows where there is little air pollution (little SO2). Indicator Species Example Stone fly nymph Only present in high oxygen levels in water (no algae bloom). Biological Control Natural method of control (no chemicals). a) Using predator b) Deliberately introducing a disease Ladybirds and greenfly Myxoma virus and myxomatosis in Australian rabbits Advantages 1. No chemicals so no algae bloom/pesticides building up. 2. Cheap after initial set up costs. Disadvantages 1. Can’t guarantee that all pests will be killed. 2. Predator or disease could become the problem in place of the pest. Genetic Modification Genetic Engineering (Cell Biology unit) A useful gene from another species is inserted into the plant to produce a GM crop. GM cauliflowers grown with scorpion genes that kill pests that try to eat the cauliflower. Golden Rice