ecosystems Flashcards
where does energy in ecosystems come from
the sun
why isn’t all the sunlight used in photosynthesis
isn’t absorbed by chlorophyll, wrong wavelength, reflected or transmitted
what are the trophic levels
producer (autotrophs)
primary, secondary, tertiary consumers (heterotrophs)
decomposers
why is not all light energy converted into glucose
inefficient photosynthetic reactions
limiting factors
how is energy lost between trophic levels
heat in respiration
excretion
undigested parts
what is gross primary production
total amount of energy that producers capture through photosynthesis
what is net primary production
amount of energy available for growth and reproduction after respiration
what is biomass
mass of organic material in an organism / ecosystem
how would you estimate biomass in a field of wheat
- collect wheat in one square metre
- dry them at 80 C, weigh and dry again ]
repeat until mass doesn’t change → full dehydrated, moisture completely removed
- multiply answer by area of field
what do farmers aim to do and how
increase energy efficiency by farming plants and animals in a controlled way to minimise energy losses
- restricting movement
- heated environments to maintain temperature
- simplify food webs to reduce energy loss between trophic levels ie pesticides
what is succession
the process by which ecosystems change over time
what happens in the process of succession
- hostile environment is colonised by a pioneer species → this changes the abiotic factors of the environment
- these changes make the environment suitable to support other organisms
- establishment of new plant and animal species increases species diversity → pioneer species replaced
- a climax community develops → less hostile environment, increased biodiversity
what a nutrient cycles
nutrients cycle between biotic and abiotic components of ecosystems within which the exist as organic and inorganic compounds
what is nitrogen fixing
nitrogen fixing bacteria in the soil / root nodules of legumes reduce nitrogn gas into ammonia / ammonium ions
what is nitrification
nitrifying bacteria oxidise ammonia into nitrites and then nitrates which can be absorbed via active transport in plant roots
what is ammonification
saprobionts secrete enzymes to extracellularly digest nitrogen containing compounds (urea, DNA, protein) -> product is ammonia
what is denitrification
denitrifying bacteria convert nitrates into nitrogen gas under anaerobic conditions
what happens in the phosphorus cycle
erosion of rocks → phosphorus in soil
absorbed by plants through roots → used to synthesise phosphorus containing compounds
animals eat plants → release phosphates in waste products
saprobionts decompose waste products and dead organisms via extracellular digestion
leaching → phosphate ions move from soil to rivers
sedimentation → phosphate in rocks
what is mycorrhizae
symbiotic association of fungus and roots of plants to improve uptake of water and ions
how does mycorrhizae benefit the plant
hyphae / large system of threads provides large surface area -> more absorption
how does mycorrhizae benefit the fungus
provides fungus with carbs like glucose and sucrose -> energy
what happens in eutrophication
algal bloom occurs
dense layer of algae forms on the surface of water → absorbs light, prevents from reaching deeper plants
plants below surface can’t photosynthesise → death
increases competition between algae → death
saprobiotic populations increase to decompose dead matter → aerobically respire, depleting oxygen
depletion of oxygen → fish and invertebrates die
