Topic 19 Flashcards
Energy flow
- The sun is the principal source of energy input to biological systems -> light energy
- Plants make biomass (store of chemical energy) from some of the glucose made by photosynthesis -> this chemical energy gets transferred to other organisms in the food chain when animals eat the plants and eachother
- Biomass and energy are lost at each trophic level in the food chain
Biomass and energy are lost at each trophic level in the food chain
. Small amount of the total energy available to trophic level becomes biomass (eg energy is stored or used for growth
. Large amount of total eneegy available to trophic level is lost -> energy transfer between trophic levels is very inefficient
- Lost in parts of food which aren’t eaten by organisms
- Lost in some parts of food that are indigestible -> pass throughthe body and come out as waste
- Most of this energy is eventually transferred to the environment as heat
-> This explains why there’s nearly no food chains with more than 5 trophic levels so much energy lost at each stage doesn’t mean that there’s not enough left to support more organisms after 4 or 5 stages -> tend to get fewer organisms at each trophic level
Food chain
Shows transfer of energy from one organism to the next -> start always with a producer
Food chains and food webs: producers
Organismas that make their own organic nutrients -> usually using energy from the sun during photosynthesis
Food chains and food webs: consumers
Organisms that get energy by feeding on other organisms -> can be classified as primary, secondary, tertiary and quaternary according to their position in the food chain
Food chains and food webs: decomposers
Organsims that get their energy from dead or waste organic material
Food web
Network of interconnected food chains
Trophic level
Position of an organism on a food chain, food web or ecological pyramid
Ecological pyramids: pyramids of numbers
The bars show the number of organisms at a particular trophic level in the food chain
. Lowest bar: shows the producer -> trophic level 1
. Shape: upright pyramid
Ecological pyramids: pyramids of biomass
The bars show the relative mass of living material at a particular trophic level -> bars don’t always get progressively smaller from the bottom to the top
. Biomass: mass of living material in food chain -> store of energy
. Lowets bar: shows the producer -> trophic level 1
. Shape: upright pyramid, inverted pyramid or not quite a pyramid
Ecological pyramids: pyramids of energy
Show the rate of energy transfer between trophic levels -> the majority of energy present at one trophic level will not be available to the next
. Lowest bar: shows the producer -> trophic level 1
. Shape: upright pyramid
Ecological pyramids: Pyramids of numbers VS pyramids of biomass
Pyramids of biomass are more accurate and used more often -> pyramids of numbers don’t always show what’s happening in a food chain very well
Ecological pyramids: pyramids of energy VS pyramids of biomass/numbers
Pyramids of energy are more useful when showing the efficiency with which different food chains transfer energy and allow it to be directly compared -> pyramids of biomass/numbers might be misleading when doing this
Ecological pyramids: drawing ecological pyramids
- Use numbers, or figures for biomass or energy transfer given to draw bars of correct scale
- The pyramid must follow the order of the food chain -> starting with the producer
- Each bar must be labelled -> if you’re given units for biomass or the rate of energy transfer include them
Humans and food webs: factors affecting species in food web
. Overharvesting: people take so much or an organism that its population is unable to reproduce quickly enough to keep up, and the population size falls -> this can lead to an extinction and the other species connected to it in the food web are all affected
. Foreign species: doesn’t naturally occur in the area -> can be introduced intentionally or unitentionally
Humans and food webs: efficiency of plants and animals
As energy is lost at each trophic level in a food chain it is more efficient for humans to eat plants them to eat animals -> when eating animals you would be higher up the food chain as the animal has preciously eaten another animal or plant BUT plants can be producers (be on first trophic level)
. Farming crops to directly feed humans is more efficient than farming crops to feed livestock (farm animals) that are then used to feed humans
Population sizes: population
A group of organisms of one species living in the same place at the same time
Population sizes: comunity
Alk the populations of different species living in an ecosystem
Population sizes: ecosystem
A unit containing a community and its environment, interacting together
Population growth rate: food supply
More food available = population will likely grow
Population growth rate: disease
Presence of pathogens = affects a population’s growth rate -> most likely will decrease
Population growth rate: predation
- Predators: consumers that hunt and kill other animals -> prey are what they eat
. Population of predator increases = population of prey will probably decrease
. Population of prey increases = population of preadtors will probably grow
. Population of prey decreases = population of oredators will probably decrease
. Predator population removed = populations size of prey would increase until number of prey reached maximum envrionment could support -> prey population would then level off or start to decrease
-> It takes time for one population to respond to changes in other population SO predator-prey cycles are always out of phase with eachother
Population growth rate: competition
Presence of competitors affects population size -> most likey will decrease
. Plants: compete for light, space, water and mineral ions
. Animals: compete for space, food, water and mates
The nitrogen cycle
- Nitrogen in air has to be turned into mineral ions (eg nitrate ions) in soil before plants can use it -> this happens through nitrogen fixation
- Plants absorb these ions from the soil and use the nitrogen in them to produce amino acids which join to make proteins
- Nitrogen passes through food chains in form of proteins as animals eat plants and eachother -> when proteins digested they are converted back to amino acids
- Deamination: in animals excess amino acids are broken down in the liver and ammonia is a waste product from this process -> gets converted into urea and excreted and nitrigen ions eventually return to soil
- Denitrifying: bacteria in soil turn nitrates back to nitrogen gas
The nitrogen cycle: lightning
Energy in bolt of lightning makes nitrogen react with oxygen in air to give nitrates
The nitrogen cycle: nitrogen-fixing bacteria
Found in soil and the roots of some plants turn atmospheric nitrogen into nitrogen compounds that plants can use (eg ammonia which dissolved in water forms ammonium ions)
Roles of microorganisms in the nitrogen cycles: Decomposition (decomposers)
Break down proteins (in rotting plants and animals) and urea (in animal waste) and turn them into ammonia -> forms ammonium in soil
Roles of microorganisms in the nitrogen cycles: Nitrification (nitrifying bacteria)
Turn ammonium ions in decaying matter into nitrate ions and then nitrates
Roles of microorganisms in the nitrogen cycles: Denitrification (denitrifying bacteria)
Turns nitrate back into nitrigen gas -> no benefit for living organisms
The carbon cycle
Constant cycling of carbon -> from air through food chains (via plants, algae and animals, and decomposers) and eventually back out into air again
The carbon cycle: photosynthesis
CO2 is removed from the atmoshpere by green plants and algae during photosynthesis where it’s used to make glucose -> can be turned into carbohydrates, fats and proteins that make up the bodies of plants and algaes
The carbon cycle: respiration
plants and algae respire and some carbon is returned to atmosphere as CO2
The carbon cycle: feeding
Plants and algae are eaten by animals and some carbon becomes part of the fats and proteins in their bodies -> carbon moves through the food chain and when animals respire some carbon is returned to the atmosphere as CO2
The carbon cycle: decomposition
Decomposeres feed on the remains of plants, algae and animals when they die and break down waste produced by animals -> these can be types of animals (detritus feeders) or microorganisms and when these organisms respire CO2 is returned to the atmosphere
The carbon cycle: formation of fossil fuels
Some dead organisms have been compresses over millions of years forming fossil fuels -> coals, oil and natural gas
The carbon cycle: combustion
Combustion (burning) of wood and fossil fuels releases CO2 back into the air
