B17 Flashcards
Organising an ecosystem
What is the original source of all biomass (and how is it transferred across organisms) ?
- light energy from sun
- photosynthetic plants (producers) use this energy to produce biomass which then gets eaten by herbivorous animals that then get eaten by other animals and so on, transferring biomass across trophic levels
What does the average food chain look like ?
producer -> primary consumer -> secondary consumer -> tertiary consumer
What are the limitations of food chains as a model for feeding relationships ?
does not accurately depict the complexity of feeding relationships; the majority of the time, animals eat many different species and varieties of other plants and animals, not just one
- in this sense, food webs are a much better depiction of feeding relationships
Describe how populations of predators and prey rise and fall in relation to one another
- when prey population is high, lots of food available for predators
[] predators catch and eat many prey, and so predator populations rise whilst prey populations fall due to the increased demand for food - less prey means less food for predators, so less predators are likely to catch enough food to survive
[] predator populations fall - less predators mean that the prey can breed and grow in population again
- cycle repeats
Which two types of organisms are responsible for the process of decay ?
- detritivores (maggots, worms, beetles)
[] often begin the process of decay - decomposers (microorganisms like bacteria and fungi)
[] digest waste and dead organisms, keeping some products for their own reproduction and respiration, and releasing the rest (nitrates, mineral ions, carbon dioxide) into the environment to be recycled
What is the purpose of decay ?
To return valuable resources from the corpses of plants and animals (like carbon, minerals etc.) to the earth to be used for new organisms like plants
Describe the decay cycle
- plant material eaten by consumers
- consumers eventually die and produce waste like faeces throughout their lives
- decomposers break down the corpses and waste
[] return mineral ions to soil and carbon dioxide to the atmosphere - producers take in mineral ions and carbon dioxide for photosynthesis and protein synthesis, helping them grow
- cycle repeats
Describe the water cycle
- water vapour is brought into the air via transpiration from plants and evaporation of water from oceans and bodies of water due to heat from the sun
- the water vapour condenses when it rises into cooler air and forms clouds
- clouds amass more and more droplets of water vapour, and when they get heavy enough, water is released as precipitation (rain, snow, hail, sleet etc.)
- water from precipitation either goes through percolation (sinks into the earth due to gaps between rocks and soil) or surface run-off (flows to plants and bodies of water simply by travelling along the earth’s surface)
- plants draw up water from the ground and surface run-off
- cycle restarts
Why must carbon be recycled ?
Is very scarce in the atmosphere (only makes up 0.04% of air) and yet every producer needs it for photosynthesis
How is carbon dioxide taken out of the atmosphere ?
photosynthesis -> biomass which is then passed up trophic levels
How is carbon dioxide returned to the environment ?
respiration, decay and combustion
What is the word equation for photosynthesis ?
carbon dioxide + water -> glucose + oxygen
What is the word equation for respiration ?
oxygen + glucose -> water + carbon dioxide
What is the word equation for combustion ?
fuel + oxygen -> carbon dioxide + water
Describe the carbon cycle
- consumers eat producers
- consumers respire and then eventually die (and their bodies decay)
[] releases carbon dioxide into the atmosphere - combustion (of fossil fuels) also releases carbon dioxide into the environment
- producers take in carbon dioxide for photosynthesis
[] producers also respire during hours of low light, again releasing some CO(2) - cycle repeats
Describe the future of the carbon cycle
- human activity on a large scale has upset the natural levels of carbon in the atmosphere, dysregulating the carbon cycle
- the carbon cycle most likely will not be able to regulate carbon dioxide levels in the atmosphere if they keep increasing
Describe the conditions for decay
- warm temperatures
[] can’t be too hot though, as digestive enzymes in the decomposers will then denature - moisture
[] makes food easier to digest
[] stops decomposers from drying out
[] allows decomposers to grow (in numbers) faster - oxygen
[] for respiration of decomposers
How can humans use the process of decay to recycle organic materials (to produce things like biogas and compost) ?
compost
- usually made by placing (farm) animal dung or waste plant material into a bin to rot/decay
[] useful as fertiliser for soil as returns many crucial mineral ions like nitrates to the soil for crops to take up via the roots
- can be made with or without oxygen
[] with oxygen, the process if quicker and causes a rise in temperature due to the aerobic respiration, killing off weed seeds
- is faster with moisture incorporated
biogas
- methane produced by decomposers when decaying waste under anaerobic conditions (usually in biogas generators)
- the process is faster under warmer conditions, and works best at 30 degrees celsius when economics of heating etc. are taken into account
Describe the method for a practical investigating the effect of temperature on the rate of decay of milk (pH method)
- gather equipment
[] 3 beakers of full fat milk in equal amounts - 300 ml should be good (from the same milk bottle)
[] pH probe
[] distilled water (to rinse the probe’s tip - measure and record the start pH of each beaker of milk using a calibrated pH probe, rinsing in distilled water between washes
[] take 3 measurements for each beaker then calculate a mean - place the 3 beakers in different locations with different temperatures
[] one in an incubator at 35 degrees
[] one at the back of a fridge (1-3 degrees)
[] one at room temperature (20 degrees) - wait 5 days
- measure the end pH of the milk in each beaker, using the same method as prior
- calculate the difference in pH between the mean start and end readings
[] fridge should be lowest value, incubator should be highest - calculate rate of decay by doing (change in pH)/(time in days)
Describe the method for a practical investigating the effect of temperature on the rate of decay of milk (mass method)
- gather equipment
[] 3 beakers of full fat milk in equal amounts - 300 ml should be good (from the same milk bottle)
[] mass balance
[] distilled water (to rinse the probe’s tip - measure and record the start mass of each beaker of milk using a mass balance
[] take 3 measurements for each beaker then calculate a mean - place the 3 beakers in different locations with different temperatures
[] one in an incubator at 35 degrees
[] one at the back of a fridge (1-3 degrees)
[] one at room temperature (20 degrees) - wait 5 days
- measure the end mass of the milk in each beaker, using the same method as prior
- calculate the difference in mass between the mean start and end readings
[] fridge should be lowest value, incubator should be highest - calculate rate of decay by doing (change in mass)/(time in days)
