Chapter 23 - Ecosystems Flashcards
Community
multiple populations of diff species living + interacting in the same area
ecosystems
communities interact with each other = environment they live in
biotic factors
living components
- anything that influences the populations within a community due to another organism’s activity
eg. predation, competition and disease
abiotic factors
non-living components
- physical or chemical factor that influences the populations within a community
eg. light, water availability, temp, humidity
Biomass
- mass of living material of the organism/tissue
- chemical energy stored within the organism/ tissue
Biomass measurements
- dry mass of an organism/tissue
- mass of carbon that an organism/tissue contains
- mass of carbon that a sample contains is approx. 50% of the dry mass of the sample
- chemical energy content of the organism when burned in pure oxygen
Dry mass
mass of the organism/ tissue after all the water has been removed
Calorimetry
- used to estimate chem energy stored in dry biomass
- inv. burning the sample of dry biomass in a calorimeter
- burning sample heats a known volume of water
- change in temp of the water provides an estimate of the chem energy the sample contains
Feeding relationships
- energy transfer = main goal
Efficiency of transfer
Efficiency of transfer = (biomass transferred/ biomass intake) x100
WHERE:
Biomass transferred = biomass that has passed to the higher trophic level
Biomass intake = biomass of the lower trophic level that has been consumed
Small % of plant biomass becomes biomass in the primary consumer (why)
- not all the plant’s biomass is eaten by the primary consumer
- not all the consumer’s biomass intake is digested
- primary consumer converts chem energy -> movement + heat, + only a small amount to new biomass
- efficiency of biomass transfer from one trophic level to the next is low, around 10%
efficiency of energy transfer between trophic levels
efficiency of energy transfer= net productivity of primary consumers/ net productivity of producers x100
efficiency of energy transfer= net productivity of secondary consumers/ net productivity of primary consumers x100
Net productivity of producers
NPP = GPP - R
GPP = gross primary productivity
R = respiratory losses
Net productivity of consumers
N = I - (F + R)
I = the chemical energy store in ingested food
F = the chemical energy lost to the environment in faeces and urine
R = the respiratory losses to the environment
How human activities can manipulate the transfer of biomass through ecosystems
- maximising agricultural productivity
producers:
use of fertilisers
selective breeding for fast growth
use of fungicides/pesticides
fencing to exclude grazers
ploughing + herbicides to kill weeds
livestock farmers can adopt these methods for primary consumers:
use of food supplements
use antibiotics + vaccines to reduce disease
control predation with fencing
reduce competition for grazing e.g. rabbits, deer
succession
- ecosystems are dynamic (constantly changing)
- change from being simple -> complex
- biotic + abiotic conditions change over time
Primary succession
- process that occurs when newly formed/ newly exposed land with no species present is gradually inhabited by an increasing number of species
Primary succession process
- seeds + spores carried by wind land on exposed rock + begin to grow
= pioneer species die + decompose, the dead organic matter forms a basic soil - seeds of plants + grasses land on soil + begin to grow
= small plants + shrubs die and decompose, the new soil becomes more nutrient-rich
roots form a network that helps hold soil in place and prevents it from being washed away - larger plants + shrubs that require more nutrient-rich soil can now grow
= require more water asw - soil is sufficiently deep + contains enough nutrients and can hold enough water to support the growth of large trees
= final species to colonise = dominant species
Climax community
- final community formed, cont. all the diff plant + animal species that have now colonised the new land
pioneer species
- first species to colonise the new land
Saprobionts
also known as saprotrophs
➜ mainly fungi or bacteria
➜ basically they eat dead stuff
➜ they eat dead stuff by secreting enzymes which break down (digest) dead stuff - extracellular digestion
➜ products formed by digestion of dead stuff is eaten
➜ this process = saprobiotic nutrition
➜ not all products formed is eaten, some remain in environment like soil
➜ so plants love saprobionts cuz plants eat the product they make
➜ without dead stuff eaters (saprobionts) dead stuff wouldn’t be broken down to more useful products so they are very important for food web
➜ some saprobionts even excrete important nutrient mineral ions as waste products from their own metabolism
Mycorrhizae
➜ it is the relationship between plant roots and fungi
➜ basically plants have evolved to have symbiotic relationships with fungi
➜ this way they both benefit from each other
➜ e.g
∘ fungi have thin filaments (hyphae) that ineract with roots of plant
∘ hyphae increase SA of root system so more water/ions can be absorbed
∘ in return fungi recieve organic compounds like glucose from plant
why is nitrogen required by all living organisms?
➜ amino acids
➜ proteins
➜ enzymes
➜ hormones
➜ antibodies (animals)
➜ receptors
➜ organelles
➜ DNA
➜ RNA
Summary of Nitrogen cycle
-
Nitrogen fixation
∘ Fixing is a way to turn the unreactive N in the air into a more useful form of N
∘ Lightning strikes forms nitrogen oxides
∘ Fertiliser made from haber process
∘ bacteria (nitrogen fixing bacteria) -
Nitrification
∘ First arrow = Nitrosomonas
∘ Second arrow = Nitrobacter
∘ NH₄⁺ 🠮 NO₂⁻ 🠮 NO₃⁻ -
Denitrification
∘ Need to have a way of putting N back ito atmosphere
∘ NO₃⁻ 🠮 N₂
look at the cycle cuz memorising isnt enough u need to be able to visualise it
bacteria involved in N cycle
Rhizobium
Nitrogen-fixing bacteria
➜ found in root nodules of legume plants
➜ Reactants: N2 and H⁺
➜ Product: NH₃ becomes NH₄⁺ so u can say either
➜ Reduction
anaerobic conditions
bacteria involved in N cycle
Azotobacter
Nitrogen-fixing bacteria
➜ found in the soil
➜ Reactants: N2
➜ Product: NH₄⁺
➜ Reduction
anaerobic conditions
bacteria involved in N cycle
Nitrosomonas
nitrification done by chemoautotrophic bacteria
➜ found in the soil
➜ Reactants: NH₃ or NH₄⁺
➜ Product: NO₂⁻ (nitrite)
➜ Oxidation
arobic conditions
bacteria involved in N cycle
Nitrobacter
nitrification done by chemoautotrophic bacteria
➜ Found in the soil
➜ Reactant: NO₂⁻ (nitrite)
➜ Product: NO₃⁻ (nitrate)
➜ Oxidation
aerobic conditions
bacteria involved in N cycle
Denitrifying bacteria
Denitrification to put N2 back into air
found in the soil
➜ Reactants: NO₃⁻
➜ Product: N₂ gas
➜ Reduction
anaerobic conditions
e.g of how C is stored
➜ atomsphere as CO₂
➜ in sedimentary rocks
➜ in fossil duels
➜ in soil and other organic matter
➜ in vegetation
➜ dissolved in oceans
Carbon cycle
Photosynthesis
➜ autotrophs use sunlight to fix CO2 (e.g calvin cycle)
➜ this removes CO2 from atmosphere
➜ terrestrial plants use gaseous CO2 directly from the air
➜ aquatic organisms use CO2 dissolved in water
Carbon cycle
Respiration
➜ all life respire which puts CO2 in air
➜ Heterotrophs rely on respiration for all their energy needs
➜ CO2 released in link reaction and krebs cycle
➜ anaerobic resp also releases CO2 via fermetation of yeast, mould and bacteria
Carbon cycle
Combustion
➜ the burning of fossil fuels release CO2 in air
➜ warmer temps mean less CO2 is dissolved in oceans and so its released into air
➜ causes climate change
Carbon cycle
Sedimentation
➜ plants die and not fully decomposed by saprobionts (rememeber they eat dead stuff)
➜ instead their bodies form layers of sediment that accumulate over millions of years, locking carbon into the ground
➜ sediment is a store of energy and can form peat and coal
➜ Aquatic organisms that die also form sediments on the sea bed (can form oil and gas)
➜ Shells and other calcium-containing body parts can form sedimentary rocks such as limestone
Carbon cycle
Feeding
➜ Carbon is passed from autotroph to heterotroph during feeding
➜ also passed from primary consumer to secondary
➜ biomass transfer always includes transfer of carbon
Carbon cycle
Decay & Decomposition
➜ Dead plants and animals are fed upon by detritivores and decayed by saprophytes which releases C into atmosphere
➜ Waste matter such as faeces and urine is used by decaying saprobionts
