Ecological Energetics Flashcards
What are producers?
Organisms that manufacture organic substances from inorganic substances; typically they are plants using light energy to produce carbohydrates during photosynthesis
What are consumers?
Organisms that obtain their energy by feeding on other organisms; typically they are animals
-primary consumers feed on producers and are herbivores
-secondary consumers feed on primary consumers and are carnivores
-tertiary consumers feed on secondary consumers and are carnivores
What are decomposes and detritivores?
Carry out decay and decomposition. Decomposers are the bacteria and fungi, detritivores are the larger earthworms, millipedes, wood lice
What is a food chain?
Represents the feeding relationship between organisms, from producer to primary, secondary, tertiary consumer and so on. Each stage is called a TROPHIC LEVEL
Why are feeding relationships better represented in food webs.
Most animals do not rely on a single food source, so in an ecosystem food chains actually involve many different species interrelating in complex ways
What is a pyramid of numbers?
A pyramid of numbers represents the total number of organisms at each trophic level in a food chain or web; each bar is proportional to the number at each level
What disadvantages are there of using a pyramid of numbers?
-They do not take size into account (so can be inverted)
-When very large numbers are involved at a level, it is very difficult to scale the bars accurately
What is a pyramid of biomass?
Represents the biomass (fresh or dry mass) of organisms at each trophic level
What disadvantages are associated with producing a pyramid of biomass?
-if using dry mass, the process of drying takes time
-dry mass results in organisms having to be killed
-obtaining fresh mass of large organisms is very difficult
-can give false picture of amount of energy available to be consumed
-on,y represents the standing crop (organisms present at any one time)
What specific problems arise when using a pyramid of biomass in marine or aquatic environments?
An inverted period may arise because
-pyramid only represents a moment in time rather than taking the whole year of biomass into account
-seen in early spring when biomass of zooplankton exceeds phytoplankton for a short while
-productivity isn’t taken into account. Phytoplankton have a high rate of reproduction, so they are actually replenishing their numbers rapidly
What is a pyramid of energy/productivity?
Reflects new material produced or productivity per unit of time in Kj/m^2/yr
Does the pyramid of energy have any advantages/disadvantages?
Advantage- accurate way of representing energy at each trophic level
Disadvantage- difficult to obtain data for the long time period needed
Why does so much of the suns energy (99%) not even reach the leaves of photosynthesising plants?
-it is reflected back into space by dust particles or clouds
-it is absorbed by atmospheric water vapour and dust and re-radiated
-some of the energy reaching earths surface misses the leaves
Most of the very small amounts of the suns energy that actually reaches the leaves is lost. How?
-it is reflected off a thick waxy cuticle
-it evaporates water sitting on the leaf
-it misses the chloroplasts
-it is reflected off of the leaf as it is the wrong wavelength
-it is lost as heat due to inefficiencies of photosynthetic reactions
What is the gross primary production or GPP?
GPP is the energy contained within the organic compounds produced in photosynthesis
What is net primary production (NPP)
The amount of energy available for plant growth or for passing onto the next trophic level after respiration has taken place
How are GPP, NPP and respiration,R, related to one another?
GPP= NPP + R
Energy transfers from producers (NPP) to consumers is low, at around 5%-10%, why is this?
-some plant material, like roots, may be inaccessible
-the plant material is often difficult to digest
-excretory losses (like urea) from the primary consumer
-much energy is used by the consumer in respiration to produce ATP, and is lost as heat energy during the process (especially with endotherms)
-some plant material is lost to decomposed food chains
Energy transfer between consumers is between 10%-20%.What causes theses energy losses.
-excretory losses
-uneaten structures (hooves, shells, hair)
-losses due to respiratory processes
-losses due to death and decomposition and entry into decomposer pathways
Why is it rare to have as many as 4 or 5 trophic levels in a food chain?
-energy transfer between trophic levels is inefficient
-there are huge losses at each step of energy transfer due to respiration and heat loss and excretion, death and decomposition
In NI agriculture, how do we aim to increase efficiency of energy transfer and therefore productivity in crop plants?
-in glasshouse crops, increase light intensity, temperature and carbon dioxide levels
-for crops grown outside in a field, fertilisers and pesticides are used
-space crops appropriately by sowing at optimum density (reducing competition but maximising land coverage)
How do we maximise productivity of domestic livestock?
-animals are confined to specific areas to reduce energy loss through movement, utilise less land and ensure even spreading of animal manure
-keep animals warm in sheds to reduce energy needed to produce heat and maintain body temperature
-feed livestock high energy and high protein foods (silage and soya meal)
Do the intensive farming methods pose any ethical issues?
Yes, the animals can suffer from high stress and bone/joint damage
What sort of management issues arise with intensive farming methods?
-close proximity means diseases spread easily
-overuse of antibiotics leads to antibiotic resistance
-reduced genetic diversity results from selective breeding
-increased pollution can arise due to the fossil fuels used or farmland waste
In terms of energy, why might it be beneficial for humans to have a plant-based diet, rather than a meat based diet especially in densely populated areas
-due to the inefficiency of energy transfer through food chains, more energy is available through eating plant products
-requires less land per human to provide energy required when fed in a plant based diet
What are primary productivity and secondary productivity?
-primary productivity is the productivity of plants (new plant tissue formed through growth)
-secondary productivity is the productivity of animals (new animal tissue formed through growth)
How do we work out the efficiency of secondary productivity in animals?
P= C- (R+U+F)
P=net secondary productivity
C= energy consumed through eating
R= energy lost through respiration
U= energy lost through excretion of urine
F= energy lost through egestion of faeces
