Energy and Ecosystems Flashcards
What are the 3 groups organisms can be divided into depending on how they get their food?
producers, heterotrophs, saprobionts
What are producers?
photosynthetic organisms that manufacture organic substances using light energy, water, and CO2 by photosynthesis
What are heterotrophs?
obtain their energy by consuming other organisms- (producers)<primary consumers<secondary consumers<tertiary consumers
What are saprobionts?
break down dead organic matter to obtain the energy that is trapped inside them, the majority of them are plants/fungi
What are food chains?
show the transfer of energy between producers and consumers, describes the feeding relationship between organisms in a habitat and energy transfers
What is a trophic level?
the position of an organism in a food chain/stage in a food chain
What do the arrows in a food chain represent?
direction of energy flow
Why is most of the energy from the sun not converted by plants?
-some of the suns light is reflected back into the atmosphere by clouds
-not all wavelengths of light can be absorbed by chlorophyll
-a limiting factor may stop the rate of photosynthesis
What is the equation for net production?
net production = gross production - respiratory loss
Why is there a low % of energy transferred at each stage of the food chain?
MEEDT
-Movement during hunting
-some of organism not Eaten
-some parts cannot be Digested so lost in faeces
- lost in Excretory materials (urine)
-lost as heat/ maintaining body Temperature
Why don’t most food chains have more than 4/5 trophic levels?
due to so much energy lost over the increasing trophic levels, there is insufficient energy to support more
How do you calculate the energy transfer % between each trophic level?
energy transfer = energy available after transfer / energy available before transfer x100
What is an autotroph?
an organism that can make it’s own food
What is biomass?
total mass of living material in a specific area at a given time
What are carnivores?
animals that eat other animals
What are consumers?
organisms that obtain their energy by feeding on other organisms
What is a food web?
shows how different food chains within a habitat interact with each other
What is (primary) gross productivity?
chemical energy store in (plant) biomass in a given area or volume at a given time
What is a herbivore?
an animal that eats producers
What is (primary) net productivity?
chemical energy store in (plant) biomass after respiratory losses to the environment have been taken into account
What is a photoautotroph?
make their own food using light energy
What is a producer?
photosynthetic organisms that manufacture synthetic substances
How can you quantify how much chemical energy dry biomass has?
burn a sample in a calorimeter and measuring the energy released as heat
What is the advantage of burning the sample in oxygen and not in air?
ensures more complete combustion will take place as air does not have such a high % of oxygen
What is the function of the copper spiral in the calorimeter?
to transfer heat energy to the water (has a large SA)
Why might the number for chemical energy be an underestimate when doing calorimetry?
might not have burnt it all, the chemical energy in ash is unreleased, not likely that the heat from combustion is transferred to water
What is biomass?
the mass of living tissue in an organism, made by producers during photosynthesis
How can biomass be measured?
in terms of the mass of carbon, or DRY mass of tissue per given area per given time
Why does the biomass have to be dry?
as the water content changes in different tissues
What is the problem with biomass having to be dry?
have to dry it at high temperatures and hence you have to kill organisms to do so
What are the units for biomass?
gm^-2 / gm^-3 / kgm^-2 y^-1
How do you dry biomass?
heat at a low temperature ( <100°C) to ensure it doesn’t catch fire, and then reweigh at intervals until no further mass decrease
Why doesn’t all the energy absorbed by chlorophyll go into the GPP?
some energy is lost during photosynthetic reactions
How is energy transferred through one level to the next?
through feeding- all energy eventually escapes as heat
How can efficiency of food production be improved?
-simplify the food webs to reduce energy losses
-reduce respiratory losses by using intensive rearing
How can you maximise secondary productivity?
-often culled when they’re young, in the past antibiotics have been used to avoid unnecessary energy loss to pathogens
What does selective breeding do?
allows farmers to produce livestock with faster growing rates and increased production of products
What is the equation for net primary production?
NPP = GPP- R
What is productivity?
amount of energy input to the trophic level that is converted into biomass
What is the net production of consumers?
N = I (F + R)
N= net production
I= energy input
F= energy lost through faeces and urine
R= energy lost through respiration
What is intensive rearing?
keeping animals in a small enclosure, reducing energy lost as heat from the body- more energy incorporated into new tissue, and controlling feeding to prevent wastage/ optimum amount of nutrients received
Negative effects of intensive rearing
-vulnerable to rapid spread of disease
-restricted movement could cause joint issues
-use of antibiotics- antibiotic resistance
-unnatural
Positive effects of intensive rearing
-efficient energy conversion
-produces low cost food
-easier to isolate animals
What is a scavenger?
the first animals to feed on dead animals
What is a detrivore?
invertebrate which feed on partly broken down dead matter- most cannot digest cellulose
What are decomposers?
secrete enzymes outside of their bodies then absorb the products of digestion
What is decomposition?
the breakdown of dead organic material into simpler compounds by saprobiotic microorganisms
How do saprobionts break down dead organic matter?
they detect the composition of the dead organic matter and activate the genes that make the correct digestive enzyme, then they release the hydrolytic enzymes that which break down complex organic molecules. the digested products can then be absorbed and used for respiration
What are mycorrhizae?
they are mutualistic threads that grow in and around the roots. they increase surface area and may be more efficient at absorbing minerals due to different membrane proteins and absorption mechanisms
Why is the mycorrhizae relationship mutualistic?
fungus gets sugars from plant, plant benefits from enhanced absorption of water and minerals
What is nitrogen fixation?
when nitrogen gas is converted to ammonium ions
How can nitrogen fixation take place?
-lightning
-free-living nitrogen fixing bacteria in the soil or water
-mutualistic nitrogen fixing bacteria in the nodules on roots of legumes
What is nitrification?
nitrifying bacteria oxidises ammonia to nitrate in 2 stages:
ammonia - nitrite - nitrate
How do bacteria get energy?
from nitrification
What is denitrification?
denitrifying bacteria use nitrate as electron acceptors during respiration, converting nitrates to nitrogen in the absence of oxygen (WATERLOGGED SOIL)
What is ammonification?
saprobionts in the soil break down proteins in dead organic matter to form ammonia in two stages:
-proteins to amino acids using extracellular protease enzymes
-removal of the amino group from the amino acid using the deaminase enzyme
What is assimilation?
uptake of ammonium ions and nitrates by plant roots and their incorporation into plant protein
How are the nitrogen cycle and the carbon cycle similar?
fixation of gas from the atmosphere, element being passed between trophic levels, involve decomposition
How is the phosphorous cycle different?
does not involve a gas in the atmosphere
What biological molecules incorporate phosphorous?
ATP, phospholipids
What is sedimentation?
dissolved phosphate ions in oceans/lakes forming rocks under high pressure
How does the phosphorous in rocks return to the ocean?
erosion + use of fertilisers
How do phosphate ions in waste/remains end up in rocks?
decomposition
How do phosphate ions in plants end up in animals?
feeding + digestion
How do phosphate ions from animals end up in waste?
excretion + decomposition
Why are fertilisers needed?
-as specific areas of land are used repeatedly, minerals are continually taken up by the crops then the crops are removed instead of being broken down by saprobionts
-this means that we need fertilisers to replenish the nutrients or plant growth will be limited
Name and explain the two types of fertilisers
natural- dead and decaying remains of plant and animal waste like manure
artificial- mined from rocks and blended to give the right balance of minerals like NPK fertilisers
What is leaching?
where artificial excess soluble nutrients are dissolved in rainwater, seeping deep into the soil where plant roots can’t reach
What are some advantages and disadvantages of natural fertilisers?
+
useful means of disposing waste
structure to soil in form of humus
steady supply of nutrients
-
offensive smells
slow mineral release
difficult to spread/store
What are some advantages and disadvantages of artificial fertilisers?
+
easy to apply
concentrated nutrients
rapid release of nutrients
-
expensive to manufacture/buy
readily leached from soil
risk of eutrophication
What are the consequences of fertiliser use?
reduced species diversity, leaching, eutrophication
What do NPK fertilisers favour?
faster growing species ie nettles/grass
Explain eutrophication
-excess fertiliser is leached from the soil causing an algal bloom
-light is blocked from bottom dwelling plants, so they die
-less photosynthesis so less oxygen is released into the water
-increased dead organic matter causes decomposer population to increase
-more aerobic respiration and so increased/higher BOD- less oxygen
-death of aerobic animals like fish
What is BOD?
-biological oxygen demand
-measures the rate of oxygen consumed by a sample of water hence a good indicator of eutrophication
-high BOD = lots of organic material = bad
What is an indicator species?
species that is adapted to live in specific conditions
Name 3 species that have adapted to live in a high BOD environment
rat tailed maggot- hollow tail for oxygen from surface
blood worm- haemoglobin type substance inside
tubifex worms- move slowly wafting water, maintains oxygen concentration gradient
What is succession?
the gradual change in an ecosystem over time in a given area due to interactions between species and the environment
How can population size be measured?
-frequency (how many individuals)
-density (individuals per unit area)
-% cover (how many quadrats have at least 1 of the species in)
Name 2 ways of catching moving species?
-pitfall traps
-sweep nets
