SB9: ecosystems and material cycles Flashcards
ecosystem
two or more populations of organisms in their environment
environment
all the conditions that surround any living organism
population
all the organisms of the same species in an area
species
a group of similar organisms that can breed with one another to produce fertile offspring
habitat
the place where an organism lives
community
two or more populations of organisms
producers
plants and algae, which photosynthesise & produce biomass
primary consumers
herbivores, which eat producers
secondary consumers
carnivores, which eat primary consumers
tertiary consumers
carnivores, which eat secondary consumers
apex predator
the top predator in an ecosystem
decomposers
-bacteria and fungi which break down dead organisms (decomposition)
-require oxygen and work best in warm temperatures
-release enzymes onto the dead matter and afterwards, consume the broken down substances
-when organisms die and decompose plants absorb the broken down nutrients through their roots
what is abundance?
the number of organisms in an ecosystem
what is the distribution of organisms affected by?
abiotic factors
what are abiotic factors?
non living factors
light intensity as an abiotic factor
-some plants have evolved for optimum growth in bright sunlight, others have evolved to grow in shade
-putting plants in light intensity’s they aren’t accustomed to, will negatively affect growth
temperature as an abiotic factor
-animals and plants have evolved to grow healthily at their optimum temperatures
-plants and animals placed in temperatures other than the ones they have evolved to live in won’t be able to survive
moisture levels as an abiotic factor
-some plants can’t survive in waterlogged soils:
their roots can’t respire, they rot and the plant dies
-other plants grow best where the moisture levels are high
-soil moisture meters can measure how wet an area is
soil pH content as an abiotic factor
-some plants, grow best in acidic soils and will quickly die if planted in alkaline soils
-others, prefer alkaline soils
-some, can grow in both; these plants are unusual, their flower colour changes in different soils
-the pH of water can also affect the aquatic organisms found there
-different species have evolved to survive at different pH levels found within water
soil mineral content as an abiotic factor
-many plants need high levels of soil minerals to grow well
-carnivorous plants, have evolved to catch insects to supplement the low levels of minerals found in the soils in which they grow
how is magnesium used as a mineral for plants?
-required to produce chlorophyll
-plants with unnaturally yellow leaves may have a magnesium deficiency
wind intensity & direction as an abiotic factor
-many organisms prefer more sheltered locations, plant seeds are more likely to settle and germinate there
-herbivores which depend on these plants are more likely to live close to where they grow
carbon dioxide levels as an abiotic factor for plants
-carbon dioxide is a reactant in photosynthesis, which means plants need it to survive
-areas with higher levels of carbon dioxide are more likely to have healthy plants growing
-farmers often release carbon dioxide within their greenhouses to maximise their crop yield -woodlands often have higher carbon dioxide levels than open grassland, so many plants living in open areas have evolved mechanisms to overcome a shortage of carbon dioxide
oxygen levels as an abiotic factor for aquatic animals
-oxygen from the air and oxygen produced by aquatic plants dissolves in water, without this, aquatic animals would suffocate and die
-healthy lakes & rivers have high levels of oxygen & polluted waters often have low levels of oxygen
-this pollution means that only certain species can survive
-these are bioindicator species because their presence or absence informs Us about the condition of the habitat
bioindicators of oxygen levels within water:
water with no pollution has:
-mayfly larva
water with some pollution has:
-freshwater shrimp
water with moderate pollution has:
-bloodworm
water with high pollution has:
-sludgeworm
water with very high pollution has:
-no living insects
levels of pollutants and lichens
-air pollutants such as sulfur dioxide are released from the burning of coals
-lichens cannot survive if the concentration of sulfur dioxide is too high, so lichens are considered to be indicator species for air pollution
-if the air is clean there will be lots of lichens
what are biotic factors?
factors that are livinv
availability of food as a biotic factor
-all animals need food to live
-the availability of food is affects how many animals live in an ecosystem
-areas with rich food supplies (eg:
rainforests) have more species of life than other areas like deserts
new predators as a biotic factor
-in balanced ecosystems, predators & prey have evolved together, predators can catch enough prey to survive, but not so many that they kill all prey
-the arrival of a new predator can upset this balance
-introducing new predators can cause a decline in the numbers of prey, which then reduces the food supply for existing predators
new pathogens as a biotic factor
-when organisms inhabit new ecosystems, they often bring new pathogens
-these can diminish organisms which aren’t immune to them
-pathogens have also been introduced on purpose
-diseases that affect certain organisms can be released so that the population is reduced
competition as a biotic factor
if two species compete for the same resources and one is better adapted to take advantage of these resources; then that species will outcompete the other
-this may continue until there are too few members of the lesser adapted species to breed successfully
food competition in animals
-all animals require food which provides them with energy and raw materials to complete life processes, without which they may die
-some birds have evolved to only eat certain types of insect to reduce competition from other species
-others birds compete with other members of their own species
mate competition in animals
-animals within a species compete for mates so they can pass on their genes to their offspring
-competition often results in fights
-fights competing for mates can result in serious injury or death, but benefits the population as only the strongest pass on their genes to the next generation
territory competition in animals
-the territories of animals contain all of the resources
-many animals, will fight for territory
intraspecific competition
competition between organisms within the same species
interspecific competition
occUrs between organisms of different species for a common resource
interdependence
all organisms that live in an ecosystem depend upon each other, for food, protection, shelter, etc, in order to survive
stable community
-the size of the populations of all species remain relatively constant over time
-the different populations are living in a healthy balance with their environment
parasite
an organism that lives in/on a host and benefits from it while causing damage to it
tapeworms
-parasites that live inside the small intestine of their hosts
-have no digestive system, absorb the digested products of digestion from their hosts
-release eggs in the faeces which can infect other hosts
-the host loses nutrition, and may develop weight loss, diarrhea and vomiting
tapeworm adaptations
-strong suckers and hooks for attachment to the lining of the small intestine
-thin and flattened and have a very large surface area for absorption of nutrients.
-release lots of eggs because the chances of the parasite finding another host is very small and many eggs will die.
why do parasites usually not kill the host?
this would cut off their food supply
mutualism
is a relationship between two organisms of different species in which each individual benefits from the activity of the other
mutualism between bees and flowering plants
bees obtain nectar for food and spread the flower pollen from one flower to another, which helps reproduction in plants
lichens & mutualism
-lichens are formed by algae and fungi living together
-algae can photosynthesise and make food, which is shared with the fungus
-the shelters the algae from a harsh climate
mutualism between cleaner fish and larger fish
-cleaner fish swim near the gills of larger species and eat the parasites
-the smaller cleaner fish get nutrition & protection, the larger fish have the gill parasites removed
quadrants
-square frames of wire usually
0.25 m²
-placed on the ground to look at the plants or slow-moving animals within them
3 things that can be found out by quadrants
- number of individuals of one species is recorded
- species richness: the number of different plant or animal species is recorded (not individuals in a species)
- percentage cover: the percentage of the quadrat area that is covered by one species (eg grass), used to identify plant frequencies
random sampling
-placing of quadrats at random coordinates
-can be used for all investigations
systematic sampling
-the quadrants are spaced regularly throughout the area along a transect
-can be used if there is a trend or pattern across the habitat
sampling with traps
-small animals (like insects) need to be trapped so they can be counted and then released afterwards
-pitfall traps are small traps dug into the ground, often with food inside to attract small mammals
-the sides of these traps are smooth to stop the mammals escaping
sweep netting
collecting insects and other organisms by sweeping a net through vegetation
kick sampling
-disturb mud and vegetation near a river bank
bed
-hold nets downstream of an area of river
-the small animals float into the net
pooters
small devices used when sampling to suck up small insects safely without them going into your mouth
why do we sample?
-to see if the number of species or percentage cover changes within an area (usually due to a change in an abiotic factor)
transect
a line created along which sampling
occurs
zonation
growing of plants in distinction regions due to changes
quadrat practical aim
to measure the species richness on the school field in areas in which the grass is regularly and irregularly cut
method of quadrat practical
- choose an area on the school field where the grass is often cut, lay a numbered grid over the map
2 use random numbers where to place your first quadrat, you can use a computer generated random number table to do this - count the number of different plant species within this quadrat (the species richness)
- return to your starting position & repeat steps two and three a further 14 times using different random numbers
- repeat steps one to four for a part of the school field which the grass is infrequently cut
- compare your results by calculating a mean for each location
tropic level
the position of an organism in a food chain, food web or pyramid
biomass
living or recently dead tissues
pyramids of biomass
the total biomass of each trophic level represented as a modified bar chart
how does biomass change in a food chain?
in a food chain from a healthy ecosystem, the biomass at each trophic level must reduce
eg: clover -> snail -> thrush -> sparrowhawk
-the clover has the most biomass
what happens if pyramids of biomass aren’t perfectly shaped?
the ecosystem is likely to be unhealthy and in danger
how must pyramids of biomass be drawn?
-bars equally spaced around the midpoint
-bars touching
-bar for the producer at the bottom
-length/width of each bar is proportional to the amount of biomass available at each trophic level
what do the arrows in a food chain show?
the transfer of biomass from one organism to another
how much biomass is transferred from one trophic level to the next?
-around 10%
-the 90% is used by the organism to complete life processes
-biomass can be lost between stages because not all of the matter eaten by an organism is digested: some of it is excreted as waste
why do food chains rarely go past 6 trophic levels?
-because only around 10% of the biomass at each trophic level is passed to the next, the total amount becomes very small after only a few levels
how much energy from the sun is used by plants in photosynthesis?
-about 1% of the energy from the sun is used by the plant during photosynthesis
-this sounds small but is still enough to power almost all food chains on the planet
percentage efficiency transfer
biomass in higher trophic level / biomass in lower trophic level × 100
biodiversity
the number of different species in an area
an area with large populations of few species is…
not biodiverse
effects of the numbers of a species reducing for the rest of a food chain (algae - zooplankton
- sand eel - puffin - arctic skua)
if the numbers of zooplankton are reduced, then more algae will grow and the population of other consumers will fall
why are ecosystems with higher biodiversity more stable?
-they have fewer species that depend on just one other for food
-ecosystems with higher biodiversity are more stable as they can easily adjust to changes
why does the future of the earth depend on maintaining biodiversity?
-maintaining biological resources like food and medicines: we rely on many different species as food or sources of medicine
-for recreation and tourism: for example, forests with a high biodiversity are attractive places to visit, they benefit local people who use the ecosystem for recreation & provides income by attracting other people to the area
how are we combatting the reduction of biodiversity due to activities that create air & water pollution?
conservation of species and habitats helps to maintain the range of biodiversity
population in 2012
7 bittion
net increase of humans
75 million
why does our population increase?
-better health care -> people are living longer
-new medicines are being developed -> people don’t die of previously fatal diseases
-farmers can make more food using new breeds and equipment
what do scientists think will happen to the rate of population increase?
-some think that the human population will continue to increase and humans will be able to solve any problems that come their way
-others think that humans will run out of resources & the earth’s population will stop increasing, but remain high
-other scientists think that the population will reduce significantly (crash)
as the human population increases, the volume of ____ that is produced also increases
waste and pollution
what does modern society being more consumable mean?
humans manufacture more products and replace them more often, this consumption is not sustainable
water pollution
-open sewers can lead into water courses, such as streams and rivers, which can cause illness in humans that may drink the contaminated water
-some water pollution comes from toxic chemicals released illegally by factories
eutrophication
- excessive nutrients from fertilisers are from the land into rivers or lakes by rainwater
- these pollutants cause growth of algae (algal bloom)
- the algae blocks the sun causing plants to die, then they cannot give off oxygen for the fish to breathe
- dead plants are broken down by bacteria decomposers, using up even more oxygen in the water
- oxygen levels reach a point where no life is possible, all organisms die
air pollution
-combustion of fuels releases carbon dioxide, this contributes to the greenhouse effect and leads to global warming
-combustion of fuels releases sulfur dioxide and nitrogen oxides which can cause acid rain
-tiny particles from smoke can cause smog
land pollution
-rubbish we throw out goes to land fill (huge holes in the ground that our rubbish is dumped into)
land use
-the larger the human population gets, the more land we require
-more houses must be built, more food must be grown and more waste is produced
-this means less space & fewer resources for other animals and plants
-biodiversity is reduced when land is cleared for human uses
problems with deforestation
-destroys the habitats of the organisms that live there
-causes extinctions
-reduces biodiversity
-releases carbon dioxide
how much of the amazon rainforest has been cut down in the last 50 years?
nearly 20%
how many hectares of rainforest are destroyed each day?
32,000 hectares
negative human impacts on biodiversity
-eutrophication
-fish farming
-introduction of non-indigenous species
fish farming
-fish are farmed in large nets or tanks within lakes or the sea
-farm waste, chemicals, pathogens and parasites are released into the surrounding water, harming other marine life
-carnivorous species of farmed fish, need high amounts of protein in their diet, they are often fed on wild fish, reducing their populations
-sometimes fish can escape and compete with indigenous wild species and compete for resources, resulting in reduced biodiversity
-predators of the fish can become trapped in the nets and die
introduction of a non-indigenous species
-a non-indigenous species may be introduced by humans for removal of pest species or for hunting
-however, the new species may outcompete or kill indigenous species
-these may be reduced in number, resulting in reduced biodiversity/ extinction
positive human impacts on biodiversity
-breeding programs to help preserve endangered species, like the panda
-protection and development of new endangered habitats eg: national parks
-reducing deforestation
-reforestation
-recycling rather than dumping waste in landfill sites
food security
a measure of the availability of food required to support people of a household, region, country or any specified area
how is food security reduced?
-the increase in human population
-changing diets (eg: people starting to eat more meat in newly developed countries)
-new pests and pathogens that attack crops and farm animals
-the effects of climate change, which is making farming more difficult in many
areas
-increased costs of farming
how is ‘the state of food insecurity in the world’ produced?
-the united nations food and agriculture organisation (FAO) records the mean prices of five key products: cereals, vegetable oils, dairy, meat and sugar
-they compare this with different factors and produce an annual report
intensive farming of crops
-uses machines, fertilisers, man-power and high-yield crops to maximise the amount of food produce
-farmers often grow only one crop to maximise their profits (monoculture)
-hedgerows have been removed from many fields to make them bigger and easier to tend to by big machines
-reduces biodiversity
intensive farming of animals
-keep livestock in smaller pens with regulated temperatures, reduces the energy they need for movement and temperature regulation and so maximises their size and yield
-some animals are fed high protein foods to increase their growth
-they are often fed antibiotics in their food to prevent diseases
disadvantages of intensive farming of animals
-animal farming wastes more energy because the food chain is longer
-animals are often fed crops which could be consumed by humans
advantages of intensive farming
-higher yields
-cheaper food for the consumer
-more efficient use of food
-easier quality control
disadvantages of intensive farming
animals:
-risk of antibiotic resistance
-heating buildings costs money and requires energy
-lowers biodiversity
plants:
-quickly reduces nutrients in soil
-machines create pollution
-excessive fertilisation causes eutrophication
organic farming
-does not use machines to the same extent as intensive farming
-no pesticides
-natural fertilisers: compost and manure
-crop rotation
advantages of organic farming
-minimal pollution from machines
-no pesticides
-natural fertilisers are used
-promote biodiversity
-keep soils healthy
disadvantages of organic farming
-less uniform
-products are more expensive
effects of pathogens on farming
-new pathogens may reduce yields dramatically as the crops or animals may not be resistant
-crop failure
-kill animals
sustainability
maintaining the needs of the human population into the future
bioethanol/biofuel
-bioethanol is made by fermenting sugar
-biofuel crops provide a renewable fuel
-biofuels have a negative impact, as they are often grown on land which could be used for growing crops
sustainable fisheries
-number of fish that are caught and killed does not ever exceed the birth of new fish
-to address overfishing, many countries are adopting a more sustainable strategy for fishing
-fishing quotas limit the amount of fish that can be caught and killed from specific species
-the size of the gaps in fishing nets has been increased so juvenile fish can reach reproductive maturity and have offspring before being caught
-these practices have meant that many fish populations are now recovering
overfishing
capturing fish faster than they can reproduce
greenhouse effect
-when energy from the sun hits the surface of earth, some of it is absorbed and some of it is reflected back
-some of this reflected energy passes through the atmosphere into space, but some of it is reflected back again to earth
-heat is retained in earth’s atmosphere by greenhouse gases
climate change
a shift in the average weather in a place
effects of climate change
-disruption to the growth of crops
-drought in some areas
-an increased average temperature
-increased severity of wildfires
-increased extinctions
global warming
an increase in the average temperature of the earth’s atmosphere
consequences of global warming
-melting of the polar ice caps
-rise in sea level
-change in weather patterns
-animals will migrate towards the poles to find habitats with suitable temperatures
-tropical diseases may become more common in other regions
-many species will become extinct
ways to reduce the rate of global warming
-using energy resources more efficiently
-using renewable sources of energy instead of fossil fuels
-reducing deforestation
-developing techniques to capture and store the carbon dioxide released from power stations
removing carbon dioxide from the atmosphere
-green plants remove carbon dioxide from the atmosphere by photosynthesis
-carbon becomes part of complex molecules in the plants
returning carbon dioxide to the atmosphere
-organisms return carbon dioxide to the atmosphere by respiration
-carbon dioxide is also released in large amounts by combustion
carbon cycle
- carbon enters the atmosphere as carbon dioxide from respiration and combustion
- carbon dioxide is absorbed by green plants for photosynthesis, carbon becomes part of complex molecules in the plants
- animals feed on plants, passing the carbon compounds along the food chain. most carbon they consume is exhaled as carbon dioxide during respiration. the animals and plants eventually die
- dead organisms are eaten by decomposers & carbon in their bodies is returned to the atmosphere as carbon dioxide
how photosynthesis converts carbon dioxide
carbon dioxide -> glucose
how respiration converts carbon dioxide
glucose -> carbon dioxite
how combustion converts carbon dioxide
fuel -> carbon dioxide
the water cycle
- evaporation: water from the land and sea evaporates due to energy from the sun
- condensation: water from evaporation can condense, this happens as air rises and cools, often forming clouds
- transport: water in clouds can be blown many miles by strong winds and is transported to other areas
- precipitation: rain, snow, hail and sleet fall from the sky
- surface runoff: water will be absorbed into the ground after precipitation but if a large volume falls or the ground is already wet some water can run along the surface of the ground
- infiltration: water that has fallen as precipitation is absorbed into the ground, this can be stored within underground rocks
- transpiration: plants need to maintain a constant stream of water to their leaves for transport and support. they allow some water to evaporate as water vapour from their leaves so it is continually ‘pulled’ to their leaves from the soil
potable water sources
-precipitation
-seawater
producing potable water from seawater (high salt content)
distillation:
-the seawater is boiled, the water vapour is then cooled and condensed to form pure water, the salt is left behind
disadvantages of producing drinking water with distillation
-expensive: large amounts of thermal energy are needed to heat the seawater
-carbon dioxide emissions from burning fossil fuels contribute to global warming
reverse osmosis
-water is forced at high pressure into a vessel with a partially permeable membrane
-the pressure causes water molecules to move in the opposite direction to osmosis from a concentrated salt solution (low water concentration) to a lower salt concentration (higher water concentration)
-water molecules pass across the membrane leaving the salt behind, so pure water is available for drinking
why is nitrogen important?
it’s essential for the formation of amino acids which form proteins
nitrogen cycle
- nitrogen gas from the air is converted to nitrate compounds by nitrogen-fixing bacteria in soil or root nodules. lightning also converts nitrogen gas to nitrate compounds. the haber process is a man-made process where nitrogen gas is converted into ammonia & used to make fertilisers
- ammonia is converted to nitrates by nitrifying bacteria in the soil
- plants absorb nitrates from the soil and use these to build up proteins. the plant may be eaten by an animal, and its biomass used to produce animal protein
- decomposers break down the bodies of dead organisms, urine and faces resulting in nitrogen being returned to the soil as ammonia. this ammonia is converted to nitrates by nitrifying bacteria
- in some conditions, denitrifying bacteria in the soil break down nitrates and return nitrogen gas back to the air. this is usually in waterlogged soil. improving drainage reduces this effect, making the soil more fertile by retaining more nitrates
how can farmers increase nitrate content in soil?
-crop rotation
-fertilisers
crop rotation to increase nitrate content
-farmers often grow crops such as peas, beans or clover as these crops can form nitrates (they have nitrogen-fixing bacteria in their roots)
-this will increase the nitrate content and fertility of the soil
-crop plants will take in the nitrate and use it to make proteins for growth
indicator species
the presence, abundance or absence of these organisms provides information about the level of pollution in the environment
how lichens indicate air pollution
-bushy lichens need really clean air
-leafy lichens can survive a small amount of air pollution
-crusty lichens can survive in more polluted air
decomposition
the breakdown of dead matter
how temperature affects the rate of decay
-at colder temperatures decomposing organisms will be less active, therefore the rate of decomposition remains low
-as the temperature increases,
decomposers become more active and the rate of decay increases
-at extremely high temperatures decomposers will be killed and decomposition will stop
how water affects the rate of decay
-with little or no water there is less decomposition because decomposers can’t survive
-as the volume of available water increases, the rate of decomposition also increases
-many decomposers secrete enzymes onto decaying matter and then absorb any dissolved molecules, without water these reactions can’t happen
how oxygen affects the rate of decay
-decomposers need oxygen to survive and without it there is little or no decomposition
-oxygen is needed for many decomposers to respire, to enable them to grow and multiply
-as the volume of available oxygen increases, the rate of decomposition also increases
-some decomposers can survive without oxygen
rate of decomposition
mass lost/days
how are decomposers helpful?
-decomposing bacteria and fungi break down dead organisms
-they help recycle minerals and nutrients to the environment, which can then be used by other organisms
-as they decompose dead matter, the decomposers also respire and so release carbon dioxide to the environment, contributing to the carbon cycle
milk decay practical (equipment)
-syringe
-two test tubes
-beaker
-water bath
-full fat milk (5ml)
-sodium carbonate (7ml)
-lipase (5ml)
-phenolphthalein
milk decay practical (method)
- use a syringe to put 5ml of full fat milk into a test tube
- add 7ml of sodium carbonate to the test tube of milk so that it is alkaline
- add a few drops of phenolphthalein to the test tube of milk, it should be pink
- put 5ml of lipase into a separate test tube
- place the test tubes into a water bath that is 60 degrees and put a thermometer into the test tube of milk
- once the temperature is 60 degrees, take 1ml of lipase and put it into the test tube of milk, start your timer
- continuously mix the mixture and stop your timer once the mixture has gone white
- record the time taken in a table and repeat the experiment for different temperatures
milk decay practical (aim)
to investigate the effect of temperature on decay
examples of decomposers
fungi, bacteria, detritivores, earthworms
compost
-compost can be used as a natural fertiliser
-once the compost (excretement & food waste) is spread onto the soil, it is broken down further by decomposing microorganisms
-ensures the recycling of minerals that can then be absorbed by plants to be used for growth
why must compost be turned over?
turning the composting material adds air, which is necessary for the composting process
