b4
ecosystem
ecosystem : all the organisms living in an area as well as all the non living conditions eg soil quality, availability of water, temperature
materials are recycled through both the biotic and abiotic components of ecosystems
living things are made of elements they take from the environment, plants take in carbon, hydrogen, oxygen, nitrogen
turn elements into complex compounds, carbs, proteins and fats that make up living organisms, taken in by animals when they eat the plants
elements are recycled, return to environment eg soil or air through waste or death to be used by new plants and put into food chain again
dead organisms and waste products decay because they're broken down by decomposers and are put back into soil
carbon cycle
important element that living things are made from, but only a fixed amount so must be recycled
DOWN FROM AIR : powered by photosynthesis, green plants use carbon from CO2 in the air to make carbs, fats and proteins
PASS : eating passes carbon compounds in plant to animals in food chain or web
products are made from plants and animals
UP : plant and animal respiration while organisms are alive releases CO2 back into air
decomposers release CO2 back into air by respiration as they break down material
plant and animal products are burned/combusted, released CO2 back into air inc fossil fuels which are made of decayed plant and animal matter
DOWN : plants and animals die and decompose, creating waste
also excrete waste
decomposition of materials means that habitats can be maintained for organisisms that live there, nutrients returned to soil and waste doesn't pile up
nitrogen cycle
atmosphere is 78% nitrogen gas, very unreactive, can't be used directly by plants or animals
needed for protein growth, organisms need to get to it
plants get it from soil, nitrogen has to be turned into nitrates before plants can use it, nitrogen compounds then passed along food chains as animals each plants and each other
decomposers (bacteria and fungi in soil) break down proteins in rotting plants and animals and urea in animal waste into ammonia, forms ammonium ions, returns nitrogen compounds to soil, nitrogen in organisms recycled
nitrogen fixation : turning N2 from the air into nitrogen compounds in the soil which plants can use
happens in two ways, lightning, so much energy in a bolt that it's enough to make oxygen in the air to give nitrates, or by nitrogen fixing bacteria in roots and soil
4 types of bacteria
decomposers : decompose proteins and urea and turn them into ammonia, which forms ammonium ions
nitrifying bacteria : turn ammonium ions in decaying matter into nitrates
nitrogen fixing bacteria : turn atmospheric N2 into nitrogen compounds that plants can use
denitrifiying bacteria : turn nitrates back into N2 gas, no benefit to living organisms, often in waterlogged soil
some nitrogen fixing bacteria live in the soil, others in nodules on the roots of legume plants eg peas and beans
have a mutualistic relationship with the bacteria, bacteria get food from the plant, plant gets nitrogen compounds from the bactiera to make into protein
water cycle
sun makes water evaporate from the land and sea, turns into water vapour
warm water vapour is carried upwards, when it higher up it cools and condenses to form clouds
water falls from clouds and precipitation and is returned to land and sea
flow of fresh water through the water cycle allow nutrients to be transported to different ecosystems
rate of decomposition
oxygen availability : decomposers need oxygen for aerobic respiration so that rate increases where there is lots of oxygen, slower in low oxygen levels, some decomposers can respire anaerobically but transfers less energy, so decomposers work slower
temperature : most decomposers work best in warm conditions, rate is highest at around 50 degrees, decomposers contain enzymes, digest dead/waste material, rate of enzyme controlled reactions varies with temp, at lower and above certain temps enzymes are denatured and reaction stops
water content : decomposers need water to survive, rate of decomposition increases in moist conditions, waterlogged soils don't contain much oxygen so the rate decreases if there is too much water
ecosystem levels
individual : single organism
population : all the organisms of one species in a habitat
community : all the organisms of different species living in a habitat
ecosystem : a community of organisms along with all the abiodic conditions
species : group of similar organisms that reproduce to give fertile offspring
habitat : where an organisms lives
competition
organisms need things from their environment and from other organisms in order to survive and reproduce
plants need light, space, water and minerals from the soil
animals need territory, food, water and mates
organisms compete with other species and members of their own for the same resources
abiotic factors
temperature, moisture level, light intensity, pH of the soil
biotic factors
availability of food, number of predators, number of mates
populations of prey and predators
population of species is limited to amount of food available if population of prey increases, so does the population of predators, as predators increase, prey decreases
peak in rabbits followed by peak in foxes
predator prey cycles always out of phase with each other, takes a while for one population to respond to the other, shows interdependence
types of interdepence
parasites : live off a host, take what they need to survive, doesn't give anything back, often harms the host
mutualism : both organisms benefit
food chains
always start with a producer, eg a plant, make and produce their own food using energy from the sun, eaten by primary consumers, eaten by secondary consumers, tertiary consumers, all eventually die and get eaten by decomposers
each stage is a trophic level
pyramids of biomass and numbers
biomass : always pyramid shaped because biomass is lost at each stage in the food chain
numbers : shows number of organisms not mass
biomass transfer
energy from the sun is source of energy for nearly all life, green plants and algae use energy to make glucose from photosynthesis, some glucose used as soon as plant respires
rest of glucose used to make biological molecules like cellulose, makes up plant's biomass, energy stored as biomass is transferred through living organisms when their eaten, not much biomass is transferred from on trophic level to the next
animals use some biomass they consume for respiration to provide energy for movement, keeping warm, egestion is like faeces, excretion is like sweating, urinating, breathing out, so biomass pyramids are pyramids
efficiency = biomass available to next level/ previously available biomass x100