5 Energy transfers- Energy & Ecosystems Flashcards
Why are plants central to all ecosystems?
They produce biomass through photosynthesis
What are producers?
Green plants that use light energy to produce organic molecules (like carbs)
In what ways are organic molecules produced by plants used?
-As respiratory substances
-To make other biological molecules (eg carbs, proteins,lipids) These form new biomass
What is biomass?
The chemical energy store for an organism
What is the role of biomass in a food chain?
Can be passed along food chain to different tropic levels
What do food chains show?
How energy flows within a biological community
What is the role of producers and consumers in food chains?
-Producers (plants, algae) make biomass and are at the base of all food chains
-Consumers rely on producers as their energy source , when they eat plants + algae, chemical energy stored in biomass is transferred
How can you measure biomass?
-Dry mass of tissue per unit of area/mass of carbon in an organism
-Calorimeters
What is the dry mass of tissue per unit area and how can this be obtained?
-Mass of an organism after its water has been removed
-To remove the water, the organism is dried in an oven for several days
-Dry mass of a sample can be used to estimate the total dry mass of a population or a given area
How is dry mass usually measured?
Grams/kilograms per meter (gm-², kg m-²)
What is the mass of carbon of an organism, how does it differ from dry mass?
-Measure of mass of carbon an organism has
-Water content not taken into account
-Usually about half dry mass amount
What does calorimetry do?
-Energy contained within dry biomass can be measured using a calorimeter
-This burns biomass, calculates chemical energy released per gram (by measuring change in temp of know volume of water as a result of sample being burnt)
What is gross primary production (GPP)?
The chemical energy stored in plant biomass, in given area/volume
What is respiratory loss (R)?
During respiration nearly half of GPP is lost as heat
What is net primary production (NPP) and how is it calculated?
The chemical energy stored in biomass after respiratory losses (R) to the environment have been taken into account
NPP= GPP-R
What is secondary/consumer production?
The production of new biomass by consumer
Why can consumers not convert all the energy available from the previous trophic level into new biomass?
Energy is lost, primarily to-
Respiration
Excretion (faeces, urine)
How is net consumer production calculated and what do the letters in the equation represent?
N= I - (F + R)
N= net production of new biomass by consumers
I= chemical energy stored in ingested food
F= chemical energy lost to environment in faeces + urine
R= chemical energy used in respiration
What is productivity?
The rate of production of new biomass
What is primary productivity?
The rate of primary production of green plants
What is secondary productivity?
The rate of secondary production by consumers (herbivores, with a lower secondary production than carnivores as they eat plant material high in cellulose, which is hard to digest so more energy is lost in excretion)
How is productivity measured?
Biomass in a given area in a given time
Example of unit= kJ ha-^1 year-^1
How do farming practices attempt to maximise primary productivity?
Increasing efficiency of energy transfer, by:
Simplifying food webs;
Reducing respiratory losses
How can limiting factors be overcome to maximise primary productivity?
-Maximising plant exposure to light
-Using warmer temp in greenhouses
-Irrigation to maximise water supply
How do fertilisers maximise primary productivity?
-Can be sprayed on fields to maintain nutrient levels in soil, which help plants convert energy to biomass efficiently
How do pesticides maximise primary productivity?
-Remove any pests that might spoil crop & cause loss of biomass
-Herbicides kill weeds, reduce competition for resources like sunlight/soil nutrients
-Fungicides prevent fungal diseases
What methods of reducing energy loss to maximise secondary productivity are used?
Limiting movements of animals- reduce respiration
Using heating in barns
Antibiotics- prevent energy lost to pathogens
How does increasing growth rate maximise secondary productivity?
Helps maximise rate of production of biomass, eg-
-Selective breeding to make breeds w/ higher growth rates
-Steroids to increase growth rates & accumulation of biomass
-Harvest when young; most of animals’s energy is used for growth when young so accumulation of biomass is maximised
