Topic 5B: Energy transfer and Nutrient cycle- 1. Energy Transfer in Ecosystems Flashcards
Where do plants get their energy from?
The sun
Where do animals get their energy from?
By eating plants or other animals
Definition of ecosystem?
An ecosystem includes all the living organisms living in a particular area and all the non-living (abiotic) conditions.
Definition of producer?
Organisms that makes their own food
What is an example of a producer in a land-based ecosystem?
- Plants e.g. trees, shrubs and grasses.
- They produce their own food through photosynthesis
What is an example of a producer in a aquatic ecosystem?
- Plants e.g. water lilies and watercress
- Algae e.g. seaweeds
- They produce their own food through photosynthesis
What happens during photosynthesis?
- Plants use energy from sunlight and carbon dioxide from the atmosphere in land-based ecosystems or dissolved in water in aquatic ecosystems to make glucose and other sugars.
What are the sugars produced in photosynthesis used in?
- Respiration- to release energy for growth
- Rest of it is used to make other biological molecules e.g. cellulose which make up the cells biomass
Definition of biomass?
Chemical energy stored in a plant
Definition of food chain?
Show simple lines of energy transfer
Food chain example
Producer
I
Primary consumers
I
Secondary consumers
I
Tertiary consumers
Definition of dry mass?
Mass of an organism with the water removed
How can biomass be measured?
- Mass of carbon that an organism contains
- Dry mass of it’s tissue per unit area
Why is dry mass used as a measure of biomass rather than wet mass?
To eliminate the problem of variability due to water content as it varies
How is dry biomass estimated?
- A sample of the organism is dried in an oven at a low temperature
- Sample is weighed at regular intervals
- Once the mass becomes constant, this means all the water has been removed.
What are the typical units for dry mass?
Kg m-2
How can you estimate the amount of chemical energy stored in dry biomass?
By using a calorimetry
- Sample of dry biomass is burnt in a calorimeter
- Energy released is used to heat a known volume of water
- Change in temperature of the water is used to calculate the chemical energy of the dry biomass
Definition of gross primary production?
Total amount of chemical energy converted from light energy by plants, in a given area
How much of the gross primary production is lost to the environment as heat when the plants respire?
50% and this is called respiratory loss
Definition of net primary production?
The energy available to the plant for growth and reproduction
What is the formula for net primary production?
GPP-R
What is it called when primary production is expressed as a rate?
Primary productivity
What are typical units for primary production?
- KJ ha-1 yr-1 (kilojoules per hectare per year)
- kJ m-2 yr-1 ( kilojoules per square metre per year)
From NPP where is the energy stored?
- In the plants biomass
- Also the energy available to organisms at the next stage in the food chain (next tropic level)
Where do consumers also store their chemical energy?
- In their biomass
How do consumers get energy?
- By ingesting plant material or animals that have eaten plant material
How much percentage of the total available energy is lost?
90%
How is energy lost in food chains?
- Some parts of the organism is not eaten e.g. plant roots, bones
- Some parts are indigestible so are egested as faeces
- Some parts are lost in excretory materials such as urine
- Some energy is lost through heat from respiration
What is the formula for net production?
N= I (F+R)
N= Net production
I= Chemical energy in ingested food
F= Chemical energy lost in faeces and urine
R= Energy lost through respiration
What is the formula for efficiency of energy transfer?
% efficiency of energy transfer= Net production of trophic level/ Net production of previous tropic level x 100
What does the efficacy of energy transfer mean?
It shows how efficient energy transfer is between one trophic level and the next
As you move up a food chain what happens to energy transfer and why?
- It becomes more efficient as plants (producers) contain more indigestible matter than animals (consumers)
What is the definition of a trophic level?
A position occupied by a group of organisms in a food chain
