Community Level Systems 25/02/2019 25/02/2019 Community Level Systems OCR Gateway 2016 Biology topic 4 W Richards The Weald School

B4.1 Ecosystems 25/02/2019

Ecosystems 25/02/2019 Definition: An “ecosystem” is the total interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment. Many different materials can cycle through ecosystems. For example, consider carbon, nitrogen and water:

The Carbon Cycle CO2 in air 25/02/2019 2. Plants and algae release CO2 through respiration Burning fossil fuels also releases CO2 CO2 in air 1. CO2 is taken in by plants and algae for photosynthesis and turned into carbohydrates, fats and proteins 6. These microbes also release CO2 through respiration 4. Animals release CO2 through respiration 5. Animals (and plants) die and their remains are fed on by microbes and detritus feeders 3. The carbon taken in by plants is then eaten by animals and the animals that eat them

The Nitrogen Cycle N2 in air 25/02/2019 4. Denitrifying bacteria convert nitrates and ammonium compounds into atmospheric nitrogen N2 in air 1. Nitrogen-fixing bacteria convert N2 in the air into nitrates Denitrifying bacteria Lightning Waste and dead animals 5. Nitrifying bacteria convert ammonium compounds into nitrates 6. Nitrates taken in by plants Nitrates in the soil 3. Decomposers break down waste products and dead animals and plants to form AMMONIUM COMPOUNDS 2. Plants are then eaten by animals – the nitrogen becomes PROTEIN

The Water Cycle 1. Condensation 3. Precipitation 25/02/2019 1. Condensation 3. Precipitation Why is the water cycle important to living organisms? Maintaining habitats Flow of nutrients Drinking! 4. Flow 2. Evaporation 6. Excretion 5. Transpiration

Can you explain why these conditions help? Decomposition 25/02/2019 Waste Eating Death Absorption Broken down Microorganisms are the key to this – they break down waste and dead bodies so that the products can be used by plants for growth. Microbes work best in conditions that are: Warm Moist High in oxygen Can you explain why these conditions help?

More about Decay 25/02/2019 Decay is the process of breaking down complex structures into ______ ones. This is done be micro organisms. The rate of decay is affected by the _______ of these microorganisms: Temperature – the micro organisms’ rates of growth and respiration are quickest at around 40OC. They become “_________” at temperatures higher than this. Oxygen – more oxygen means _____ micro organisms and more aerobic ________. Some decomposers still work even in low-oxygen conditions by respiring _________. Water – micro organisms grow quickest in ______ conditions. Words – respiration, more, moist, simpler, growth, denatured, anaerobically

Compost bins 25/02/2019 That’s a nice compost bin. What’s the point in having one? Compost bins provide optimum conditions for rapid decay of waste biological material. The compost produced is used for fertiliser.

Organisation in an Ecosystem 25/02/2019 Individual – a single organism Population – all of the organisms of one species in a habitat Community – all of the organisms of different species living in a habitat Ecosystem – the whole community AND the non-living (abiotic) conditions

Abiotic Factors Scientists measure lots of abiotic factors, such as: 25/02/2019 Scientists measure lots of abiotic factors, such as: Recording temperature changes Recording oxygen levels Measuring rainfall Other examples: Light intensity Soil pH and mineral content Wind strength and direction Carbon dioxide levels Oxygen levels in water

Effect of changing Abiotic Factors 25/02/2019 Here are some abiotic factors again: Temperature Moisture levels Light intensity Soil pH and mineral content Wind strength and direction Oxygen levels in water Carbon dioxide levels Q. How would an increase in any of these factors affect these organisms?

Biotic Factors Biotic factors affecting an ecosystem can include: 25/02/2019 Biotic factors affecting an ecosystem can include: Availability of food Arrival of new predators New pathogens/diseases One species being outcompeted Yum! Yum Harsh

Using Quadrats Lay down a transect line 25/02/2019 That’s a nice ecosystem. I think I’ll sample it using my quadrat. How do I do it? Lay down a transect line Mark off regular intervals, e.g. 1m Use the quadrat every metre to sample the population size of different organisms

Interdependence Consider oxpeckers and buffalo: 25/02/2019 Consider oxpeckers and buffalo: What patterns would you expect to see in the distribution of these two organisms?

Interdependent Relationships 1 25/02/2019 1) Parasitic relationships Parasites take food from another living host _______. For example, if a human eats pork infected with bladderworm the worms attach themselves to the ___ wall and a young tapeworm grows, which _______ food from the gut. Mutualistic relationships are when two organisms benefit from each other. For example, pea plants have nitrogen-fixing ______ which convert nitrogen into nitrates for plant _____. The bacteria benefit by taking sugars from the plant for ___________. Words – growth, respiration, organism, gut, bacteria, absorbs 2) Mutualistic Relationships

Interdependent Relationships 2 25/02/2019 Predation is another example of an interdependent relationship. Consider rabbits and foxes: Hey! I ordered a steak Prey Predator Consider the populations of these two animals over time: Population of animal Time Rabbit Fox

Trophic Levels Here’s a simple food chain: 25/02/2019 Here’s a simple food chain: Herbivore (primary consumer) Top carnivore (tertiary consumer) Secondary consumer Producer Rabbit Cabbage Fox Stoat Level 2 – Herbivores that eat producers Level 4 – Carnivores that eat other carnivores Level 3 – Carnivores that eat herbivores Level 1 - Producers

Level 1 - Mass of cabbages Pyramids of biomass 25/02/2019 25/02/2019 In this food chain we can see that the mass of organisms in each stage is less than in the previous stage: Cabbage Rabbit Stoat Fox We can draw a “Pyramid of Biomass” to show this pattern: Level 4 - Mass of foxes Level 3 - Mass of stoats Level 2 - Mass of rabbits Level 1 - Mass of cabbages

Energy flow in a food chain 25/02/2019 25/02/2019 Consider the energy flow in this food chain: 100% 10% 1% 0.1% Cabbage Rabbit Stoat Fox Clearly, not all of the ___’s energy that becomes stored in the _______ will end up in the fox. Only around ______ is passed on to the next stage in each food chain. Producers only transfer ___ of light energy. Energy is lost to the surroundings at each stage because of a number of reasons: Each organism has to use glucose in respiration to ____, keep warm etc Energy is lost through faeces (______) or through CO2 and water loss Words – 10%, move, sun, waste, cabbage, 1%

An example calculation 25/02/2019 25/02/2019 What is the efficiency at each stage of this food chain? 37kg 3.2kg 0.45kg 0.04kg Cabbage Rabbit Stoat Fox Efficiency = Biomass transferred to the next level Biomass available at the previous level Clearly, a fox doesn’t have a mass of 0.04kg. This number represents the amount of biomass available to it. How does this affect the numbers of organisms as you go up the levels in a food chain?