Energy and Ecosystems Flashcards
What is net production?
The rate at which energy is stored.
Gross production - respiratory losses
Why do most food chains have only four or five trophic levels?
Insufficient energy is available to support a large enough breeding population at trophic levels higher than these.
Energy transfer =
Energy available after transfer/ energy available before transfer x 100
What do ecological pyramids provide?
Quantitative information
What are the drawbacks of using number pyramids?
- No account is taken of size
2. Impossible to account for a larger number of individuals
Define Biomass
The total mass of the plants in a particular place
The units of Biomass
gm^-2
What is the most accurate representation of energy flow?
Measure energy stored in organisms.
Units for pyramid of energy
Kjm^-2 year^-1
Define productivity
The rate at which something is produced
How is net productivity affected in agricultural ecosystems?
- Efficiency of the crop at carrying out photosynthesis
2. The area of the ground covered by the leaves of the crop
What are the additional input energies of agriculture?
Food and fossil fuels
Define a Pest
An organism that competes with humans for food or space or can be dangerous to human health
What are the qualities of an effective pesticide?
- Be specific
- Biodegrade
- Cost effective
- Not accumulate
What are the disadvantages to Biological control methods of reducing pests?
- Don’t act as quickly so there’s often an interval between introduction and reduction
- A control organism may become a pest
What are the advantages of Biological Control of pests?
- Very specific
- Reproduces itself
- Pests don’t become resistant
What are the disadvantages of using chemical pesticides?
- Always have some effect on non-target species
- Must be reapplied at intervals -> expensive
- Pests develop genetic resistance
What does integrated control involve?
- Choosing animal or plant variants that suit the local area as pest-resistant as possible
- Suitable habitats for natural predators
- Regular monitoring of crops for pests so early action can be taken
- Removing pests mechanically
- Biological agents if necessary
- Pesticides as a last resort
How are many crops grown?
Monoculture -> allows insect and fungal pests to spread rapidly
Why is intensive rearing of livestock used?
Converting the smallest possible amount of food energy into the greatest quantity of animal mass.
How is energy conserved in intensive rearing of livestock?
- Movement is restricted so less energy is used in muscle contraction
- Environment is kept warm so less heat loss
- Optimum amount and type of food for maximum growth with no wastage
- Predators are excluded
- Selective breeding
- Hormones to increase growth rates
What are the benefits of intensive rearing of domestic livestock?
- Use of space -> more natural habitats
- Safety -> smaller, concentrated units are easier to control and regulate
- Larger intensive farms have the resources to maintain a high level of animal welfare and are more easily regulated
- Low cost
- Efficient energy conversion
What are the negatives of intensive rearing of domestic livestock?
- Disease
- Antibiotic resistance
- Kept unnaturally ethical issue -> stress -> aggressive behaviour animals could harm themselves or each other. Restricted movement can lead to osteoporosis.
- Pollution -> large conc. of waste in small area
- Reduced genetic diversity
- Use of fossil fuels
Define Gross Production
The total quantity of energy that plants in a community convert to organic matter.