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St Ninian’s High School Life on Earth National 5 Biology Learning Outcomes Food Chains Food chains show the direction of energy flow. Only 10% of energy is passed on at each stage of a food chain. Energy is lost as heat and movement. All food chains start with a plant (producer). Producers can make their own food from the sun (photosynthesis). Consumers (animals) need to eat other organisms to gain energy. Primary consumers eat producers and secondary consumers eat primary consumers. Herbivores eat plants, omnivores eat animals and plants and carnivores only eat animals. Predators and prey must be animals with the prey (primary consumer) being the animal hunted and the predator (secondary consumer) being the animal that hunts. As the prey increase the predators decrease and vice versa on graphs. Pyramids A pyramid of numbers is a diagram that represent the number of organisms at each stage of a food chain. A pyramid of biomass is a diagram that represents the mass of organisms at each stage of a food chain. A pyramid of energy is a diagram that represents the total energy in the bodies of organisms at each stage of a food chain. A pyramid of numbers is less reliable as its base can be shorter when the producer is a tree or the top consumer can appear larger than it should when it is an insect like a flea.. Pyramids of biomass and energy always retain their pyramid shape. A producer always the largest biomass and energy and usually has the largest number. Learning Outcomes Food Webs & Competition Interconnected food chains make up food webs. When one organism is removed this will affect ALL other organisms by increasing/decreasing their numbers. Competition is when organisms want the same/similar resource. Intraspecific competition is between organisms of the same species for the same resource. Interspecific competition is between organisms of different species for similar resources. Intraspecific competition is fiercer as the resources required are the exact same. Competition leads to natural selection (survival of the fittest) where one species increases and the other decreases. To reduce competition, members of a species occupy different niches. An organism’s niche is the role it plays in the community e.g. birds have different beaks to eat different food. Nitrogen Cycle This is a process where nitrogen is recycled between the air, plants & animals and the soil. Nitrogen is very important as it is needed to make protein. Proteins include enzymes, hormones, antibodies, receptors and structural proteins. Three bacteria control the nitrogen cycle. Nitrogen gas is converted into protein by nitrogen fixing bacteria. Legumes are plants (peas/clover) that have nitrogen fixing bacteria in their root nodules and naturally increase the nitrate content of the soil, making it more fertile (natural fertiliser). Lightening also allows nitrogen fixation to occur (nitrogen gas converted into nitrate in soil to make protein). Denitrifying bacteria remove the nitrate from the soil and recycle this back into the air. Animals eating plants (food chain) is the only step in the Nitrogen cycle that does not involve bacteria in the cycle. Some food chains involve decomposition where dead animals/plants are broken down into ammonia. Decomposers are involved in this process. Decomposers include bacteria and fungi. The third bacteria (nitrifying bacteria) convert ammonia into nitrite and then into nitrate. Nitrification is the only 2 step process in the nitrogen cycle. Plants then absorb/uptake the nitrate in the soil to make protein. Learning Outcomes Ecosystems & Biomes Habitat is where an organism lives. Community consists of all the animals/plants living in one area. Population is one particular species. Ecosystem is made up of living (community) and non living (habitat) parts. Biomes are large ecosystems. There are 9 biomes worldwide dependent on the climate (temperature and rainfall) e.g. Tundra, Sahara. Biomes have specific flora (plants), fauna (animals) and climate (rainfall and temperature). Biomes must be preserved to have a stable planet as they increase the biodiversity. Biodiversity is the variety and abundance of organisms present. Biomes are affected by biotic, abiotic and human factors. Human factors have the biggest impact on biome biodiversity. Biotic factors are living factors and include predators and grazing. Predator and prey numbers are the opposite of each other and can be shown as waves on a graph. Abiotic factors are non living factors and include moisture, light intensity pH and temperature. Human impact factors include exploitation (overfishing/hunting), deforestation, poaching and pollution. Pollution of the air resulting from burning fossil fuels, increasing the sulfur dioxide in the air. Lichens are an example of an indicator species as they only grow where there is little air pollution. Indicator species indicate the level of pollution by their presence/absence. Pollution of the water is caused by fertiliser dissolving in rain water and being washed into lochs This increases the nitrate causing an algae bloom. Decomposer bacteria then feed on the algae and reduce the oxygen leve the water (respiration) causing fish to die. Learning Outcomes Sampling Techniques Biotic and Abiotic Factors can be sampled. Biotic factors include sampling animals (pitfall trap & tree beating) and plants (quadrat). Pitfall trap are dug level with the soil and alcohol placed in the bottom and animals such as woodlice are sampled. Tree beating is where a tree is lightly tapped and organisms that fall off are caught in a bucket e.g. spider. Problems with pitfall traps include failure to check the trap regularly or place alcohol in the trap and therefore the insects eat each other. In tree beating organisms can fly away or not fall into the bucket (use a larger bucket). Quadrats allow the abundance of a certain plant to be measured by counting the number of squares that contain the plant NOT the number of plants e.g. 20/25 squares. Quadrats must be thrown randomly. All techniques can be made more reliable by repeating the technique. Abiotic factors to be sampled include light intensity, temperature, pH and moisture. Light intensity is measured by pointing a light meter at the maximum light and being careful not to cast a shadow. pH and moisture meters involve placing a probe in the soil and wiping the probe between measurements. Temperature can be measured with a thermometer with care taken to read the scale properly and to hold the thermometer at the top to prevent body temperature being measured by accidently holding the bulb. Line transects involve using a quadrat at REGULAR intervals e.g. every metre and looking at the effect of a plant’s distribution with a certain abiotic factor e.g. effect of light intensity on grass growth. The higher the light intensity, the greater the growth of grass (plants need light for photolysis in photosynthesis). Mutations & Adaptations Mutations are a random change to DNA/genetic information. Mutations are ROLF: randomly occurring and at low frequency. Mutations can be disadvantageous (genetic disease), advantageous or neither. Disadvantageous mutations include down syndrome where individuals have 3 copies of chromosome 21. Advantageous mutations create a new allele (form of a gene) increasing biodiversity. This is not very common (black squirrel) and leads to natural selection and formation of a new species (speciation). Adaptations are features that organisms have, occurring often after a mutation that increase their chance of survival. Adaptations can be structural (shell), physiological (rat does not sweat) or behavioural (nocturnal) Mutagenic agents increase the likelihood of a mutation occurring e.g. Radiation, mustard gas & high temperatures. Learning Outcomes Speciation Natural variation exists in any population due to different alleles which is caused by random mutations. Speciation is the formation of two or more species from 1 original species. Darwin’s Finches in the Galapagos Islands are one example of speciation—all the birds have different beaks to eat different food (niche). The definition of a species is that it can interbreed to produce fertile offspring. Speciation is a three step process: isolating mechanism, mutation, natural selection. Isolating mechanisms prevent gene flow between two sub populations. Examples of isolating mechanisms include geographical, ecological and reproductive. Mutations are random and therefore occur only on 1 side of the barrier OR different mutations occur either side of the barrier. Natural selection increases the selection pressure for those with a selective advantage and these successful organisms reproduce and pass on their successful alleles and the weaker organisms die out. Peppered moth is one example of natural selection where the peppered moth died out as the black moth had camouflage as a selective advantage. Resistant bacteria are another example of natural selection as is human skin colour with darker skin caused by melanin pigment offering a selective advantage in warmer climates . Learning Outcomes Intensive Food Production Solutions Increasing human population requires increased food yield. Three main solutions to the food crisis are intensive farming, biological control and Genetically Modified Crop. All of these have the advantage of increasing food production to cope with increasing demand but all have disadvantages also. Intensive farming involves fertilisers, pesticides, growth of 1 type of plant (monoculture), ploughing fields and battery farms. Fertilisers wash into rivers, increasing algae blooms which increases decomposer bacteria deoxygenating the water and killing fish Pesticides (DDT) cannot be broken down and accumulate in the bodies of organisms as you move up the food chain to lethal levels. Intensive farming also destroys habitats of animals/deforestation due to necessity of large fields and reduces biodiversity. Biological control is a natural alternative that does not involve chemicals. Viruses/Predators are deliberately spread to control pests and reduce numbers e.g. Virus Myoxma or ladybirds to kill greenfly. Advantages of biological control include that the predator is specific to the pest, no resistance builds up, no chemicals enter rivers or accumulate in animals and it is cheap to run after initial set up. Disadvantages include lack of success on a large scale, predators can increase to a level that they become the pest, initial set up costs are high and it is not possible to eliminate all pests meaning some crops will still be lost. Genetically modified crops involves genetic engineering where a foreign gene is transferred into a plant to confer an advantage. Examples include blight resistant potatoes, golden rice and GM fruits e.g. tomatoes to prevent spoilage. GM food surrounded in controversy due to health concerns. 1.1 Food Chains Terms Producer – makes their own food (by photosynthesis). Consumers – needs to eat other organism to obtain food. Food Chains All food chains start with a producer (green plant). The arrows show the direction of energy flow. Food Chain Terms Primary consumer first consumer. Secondary consumer second consumer. Tertiary consumer third consumer. Predators animals who hunt other animals for food. Prey animals who are hunted by other animals. ***(note prey cannot be PLANTS)*** Carnivores eat animals only Herbivores eat plants only Omnivores eat animals & plants 1.2 Energy transfer in Food Chains All energy comes from the sun. Plants absorb a small percent of this energy and use this to make food (photosynthesis) Likely Percentage Calculation 1 4% of the light energy reaching the sun is converted into new plant material. How much energy did the Oak tree Receive? (4%) = 4/100 x 4,000,000 = 160,000 units of energy Likely Calculation 2 Only 10% of energy is passed on at each stage of a food How is the energy lost from the food web? 1. Heat 2. Movement 3. Undigested material (faeces) 1.3 Pyramids & Food Chains Three types of Pyramids *** learn definitions *** 1. Pyramids of Numbers Show the number of organisms at each stage of a food chain. 2. Smallest amount of energy/biomass/ numbers Pyramid of Biomass Shows the mass of organisms at each stage of a food chain. Largest amount of energy/biomass/numbers 3. Pyramids of Energy Shows the energy received by organisms at each stage of a food chain. Problem with pyramids of numbers Pyramid does not resemble a true pyramid shape when a tree is a consumer (smaller at bottom) OR insect at the top! ****Pyramids of biomass & energy always remain true pyramid **** 1.4 Food Webs All organisms are connected in a food web. Removing one organism from the food web destroys the delicate balance. When an organism is removed it will ALWAYS affect other organisms in a good or bad way, dependent on the circumstances. Common Exam Question What would happen to the phytoplankton and fish if the krill were removed? A) Phytoplankton —increase Why—Less krill eating the phytoplankton therefore can grow more. B) Fish—decrease Why—Less krill to eat. 1.5 Competition & Niche When animals/plants want same/similar resources Examples of Resources 1. Space 2. Food 3. Light (plants only) 4. Mates (animals only) Inter specific Competition Intra specific Competition Between different species Within the same species who want the who want similar resources. same resources. e.g. grey & red squirrels Much fiercer competition E.g. red squirrels Competition Graphs Results in the survival of the fittest (Natural Selection) 1 species increases 1 species decreases Niche The role an organism plays in its community Example; Different beak SHAPE for different food. Having different niches reduces competition. 2.0 Nitrogen Cycle Decomposers Decomposers are bacteria & fungus that feed on dead animals/plants and return nutrients (nitrogen) to the soil. Shown in food chains as a backwards loop on the food chain. Grass Bird Cat Fox Decomposers Decomposition Living material broken down by bacteria/fungi (decomposers) Useful material returned to soil (recycling) Why Recycle Nitrogen by decomposers? To make proteins in plants. Nitrogen Cycle 2.0 Bacteria 3 Bacteria control the recycling of nitrogen in a cycle. 1. Nitrogen fixing bacteria Nitrogen gas (air) Protein (plants/animals) Two Natural examples of Nitrogen Fixing A) Lightning 2. B) Legumes (peas/clover) Denitrifying bacteria Nitrate (soil) Nitrogen Gas (air) 3. Nitrifying Bacteria (two steps) Ammonia (dead bodies) Nitrite Nitrate 2.0 Nitrogen Cycle Other Steps to the Nitrogen Cycle: Death & Decomposition Death & Decomposition may appear as separate steps in an exam question or may appear as the same step. Death—when animals/plant die. Dec—when dead bodies then turn into ammonia. Uptake by roots/absorption Plants convert nitrate (soil) plant protein (growth) Nitrate = fertiliser for plants to make protein. Eating Food chain where animals eat plants. Plant Animals Eating is the only step in the cycle which does not involve bacteria. 2.0 Nitrogen Cycle Name of Step Process Nitrogen fixing bacteria (legumes in root nodules) Nitrogen gas to protein in plants (sometimes via nitrate) Denitrifying bacteria Nitrate (soil) to nitrogen gas in air Nitrifying bacteria Ammonia to nitrite to nitrate Decomposing bacteria/fungi Organic remains forming ammonia Absorption/uptake by roots Nitrate in soil to plant protein Biodiversity 3.1 Variety and relative abundance (amount) of living organisms. Importance of Biodiversity Variety of organisms needed for a stable planet as all food webs are linked together. If one type of organism dies out, others will be affected. Ecosystem Terms Term Definition Example Habitat Where an organism lives. Pride Rock/Caves Population One type of species. Lions Community All the different species living together . Ecosystem Made up of living (community) and non living (habitat) parts. Lions, hyenas, monkeys Desert 3.2 Biomes & Biodiversity Biomes Biomes are very large ecosystems— 9 worldwide Depend on flora (plants), fauna (animals ) & climate (rainfall & temperature) Examples: Tundra Rainforest Sahara Desert Factors Affecting Biomes Having a variety of Biomes is very important to ensure biodiversity and a stable planet. 3 Factors affect the Distribution of Biomes. Factor affecting Biome Definition Examples 1. Biotic Factors Living factors Predators, & Grazing, 2. Abiotic Factors 3. Human Influences Non Living factors Man made influences Rainfall and Temperature Overfishing/hunting Poaching (biggest Deforestation/Desertification influence) Pollution A) fossil fuels release SO2 (air) B) fertiliser produce algae bloom— (water) 3.3 Biotic Factors Predation/Prey Graphs Explaining the Graph Prey are high when predators are low Why—less predators to eat prey Prey are low when predators are high Grazing & Biodiversity Graph Why—prey eaten by predators Explaining the Graph Low Grazing/Low biodiversity Dominant species are not kept in check (survival of the fittest). Medium Grazing/high biodiversity Dominant species eaten, allowing other weaker plants to grow. High Grazing Only dominant plants can handle very high levels of grazing. 3.4 Human Impact on Biodiversity Air Pollution When fossil fuels are burned, sulphur dioxide (SO2) is released , polluting the air. Water pollution Fertiliser (nitrate) washes into water Increased algae bloom (plants grow) Algae rotted by decomposer bacteria Water deoxygenated Fish/Other species die Indicator Species Presence or absence determines the level of pollution. Two Examples 1. Lichen (air pollution) 2. Stone fly nymph (water pollution) Lichen Only grow where air is clean Nymphs only live where water is (lacks sulfur dioxide) Oxygenated (lacks bacteria) 3.5 Biotic Sampling Techniques Sampling Animals Pitfall Trap Hole dug level with ground to ensure insects fall in. Covered in stones to ensure nothing eats the insects. Alcohol placed at bottom to stop insects eating each other E.g. woodlice Tree Beating Branch given few sharp taps at specific height. Insects fall into bucket/sheet below. Use a large bucket/rimmed edges to be to observe as many insects as possible E.g. spider Errors associated with Techniques 1. Repeat for more reliable results (both) 2. Trap not level with ground (pitfall trap) 3. Alcohol not placed in trap (pitfall trap) 4. Insects fly out of bucket (tree beating) 3.5 Sampling Plants: Biotic Sampling Techniques Quadrats Error— quadrat not thrown randomly or mistake in classification when counting. Thrown at random and number of squares that have plants in the square counted (abundance score). Example Dandelion 12/25 *** Handy Hint *** To increase Reliability Repeat the experiment 3.5 Sampling Plants: Biotic Sampling Techniques Quadrats Line transect. Quadrat NOT THROWN RANDOMLY but placed every metre to determine the effect. To determine the effect of an abiotic factor e.g. (light intensity) on the growth of a plant i.e. plants need light to photosynthesise. 3.6 Abiotic Sampling Techniques Light Intensity Measured with a light meter. Meter held at maximum light intensity & care taken not to cast a shadow over meter pH/Moisture Measured with a pH/moisture meter Simply place probe into soil and take reading. Care taken to wipe probe between readings. Temperature Measured with a thermometer. Measure air, soil or water temperature by holding thermometer at top, avoiding the bulb at the bottom to prevent you measuring body temperature Care taken to read scale properly. Errors 1. Repeat for more reliable results (all). 2. Cast shadow over meter (light meter) 3. Failure to wipe between readings (moisture/pH meter) 4. Holding thermometer at bulb/not reading scale correctly (temperature) 4.1 Mutations Change to DNA base sequence (A, G, C, T) Remember Change to DNA base sequence Changes the Amino Acid sequence at the ribosome Changing the protein produced (non functional) E.g. enzyme, hormone, antibody etc Mutations are ROLF!!! Randomly Occurring (unpredictable) Low frequency (do not occur often) Mutagenic Agents •Environmental factors that increase the frequency of a mutation occurring. 1. Radiation (UV, X-ray etc) 2. Chemical agents e.g. mustard gas 3. High Temperatures Types of Mutations 1. Disadvantageous—cause genetic disease 2. Advantageous—help to increase variety & biodiversity (cause natural selection & formation of new species) 3. Neither—no effect 4.1 Types of Mutations 1. Disadvantageous Mutations—genetic disease Down Syndrome 3 copies of chromosome 21 Symptoms Causes physical & mental development problems. 2. Advantageous Mutations (not often) Create new alleles (versions of a gene). Increases variety & biodiversity. Leads to Survival of the Fittest (natural selection) & formation of a new species (speciation). Example 1—black & grey squirrel Black more aggressive Example 2—black & peppered moth black camouflaged against polluted lichen 4.2 Adaptations A characteristic which an organism has which makes it well suited to survive in its environment (survival of fittest) Often result of a favourable mutation leading to Natural selection and often formation of a new species who have a selective advantage. Adaptations increase biodiversity. Types of Adaptations 1. Structural Shell, horns 2. Physiological (desert rat) dry nose & mouth does not sweat Very efficient large intestine 3. Behavioural (desert rat) nocturnal as too hot during day 4.3 Natural Selection Also called ―survival of the fittest‖ as proposed by Darwin for how species evolve. Process 1. Variation occurs naturally due to different alleles (mutations) 2. Fierce competition for resources (inter/intra). 3. Increased selection pressure for those with a selective advantage. 4. Those individuals with a selective advantage reproduce and pass on the successful alleles. 5.. Weaker individuals die out Example of Natural Selection Alleles Selective Advantage Peppered Moth Dark & Peppered moth Black moth—camouflaged against polluted lichen. Antibiotic Resistance Human Skin Colour Sensitive & Resistant Only resistant bacteria can bacteria survive antibiotics leading to Light & Darker Skin Darker skin advantage where weather is warmer as melanin 4.4 Speciation Species Definition Can interbreed to produce fertile offspring. Speciation: formation of a new species 1. Isolating Mechanisms 2. Mutations 3. Natural Selection Isolating Mechanisms (barrier) Importance: Prevent gene flow between sub populations. 2 sub populations form Type of Isolating mechanisms: (learn these) 1. Reproductive 2. Geographical 3. Ecological Exam Tip Write Geographical NOT river in exam! 4.4 2. Speciation Mutations As mutations are RANDOM—mutations occur on only 1 side of the barrier. 3. Natural Selection Increased selection pressure for those with a selective advantage. These individuals survive and reproduce & pass on successful alleles. Weaker individuals die out. Isolating Mechanism Diagram 1 species split into 2 sub –populations by isolating mechanism (no gene flow) Mutations Mutation occurs on 1 side of barrier and not other OR Different mutations occur either side. Natural Selection Increased selection pressure for those with a selective advantage. Successful individuals reproduce & pass on their alleles. Two species formed. They cannot Interbreed to produce fertile Offspring. 5.1 Problems of Food Production World Food Problem Population rising sharply, hence not enough food. Need to increase food yield. 3 solutions 1. Intensive farming 2. Biological Control 3. Genetic Modification of crops 1. Intensive Farming Two chemicals are used in intensive farming Features Description Problem Alternative Fertiliser Nitrates which Algae bloom GM crops Pesticide builds Biological control increase the growth Pesticide Kill insects which eat crops, up as you move up food chain & kills 5.2 Intensive Farming Problem with fertilisers (learn this process) Fertiliser washes into water Increased algae bloom due to fertilizers This reduces light levels killing aquatic plants. Increased bacteria as they feed on dead algae/plants Water deoxygenated Fish Die (reduces biodiversity) Problems with Pesticides Pesticides can accumulate in the bodies of organisms over time. As they are passed along food chains, toxicity increases and can reach lethal levels. (lethal levels) 5.3 Alternative to Intensive Farming 3. Biological Control Control achieved via natural methods (no chemicals) 1. Introducing disease 2. Introducing predator Virus Myxoma & Rabbits Virus introduced to limit rabbit population. Ladybirds & greenfly Ladybirds (predator) of greenfly, reduce their numbers. Advantages 1. Predators specific to prey, does not reduce biodiversity. 2. No chemicals to accumulate up food chains. Disadvantages 1. Not very successful on a large scale. 2. Predators can become the pests if their numbers rise. 5.2 3. Intensive Farming GM Crops (genetic engineering of plants) When a foreign gene in inserted into a plant to produce a desirable characteristic. Desirable characteristics of GM crops: a) Plants that are now Drought resistant b) Plants that are now Disease resistant Indicator species Presence or absence determines the level of pollution. Two Examples 1. Lichen (air pollution) 2. Stone fly nymph (water pollution) Lichen only grow where air is clean Nymphs only live where water is (lacks sulfur dioxide) Oxygenated (lacks bacteria)