Section 5 - 13 Energy and ecosystems Flashcards
What is the ultimate source of energy for almost all organisms?
sunlight - converted to chemical energy by plants.
What three groups can organisms be divided into?
Producers, consumers and saprobionts
Define - producers
Photosythetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions.
define - consumer
Organisms that obatin energy by feeding on other organisms rather than using the energy of the sunlight directly.
What is a primary consumer?
An animal that directly eats producers.
What is a secondary consumer?
Animals eating the primary consumers.
usually, predators but may also be scavengers and parasites.
What is a tertiary consumer?
Consumers eating secondary consumers.
usually, predators but may also be scavengers and parasites.
What is a saprobiont?
Decomposers
Groups of organisms that break down the complex materials in dead organisms into simple ones.
They release valuable minerals and elements in a form that can be absorbed by plants and so contribute to recycling.
Majorly done by fungi and bacteria
What is a food chain?
- The feeding relationship in which the producers are eaten by primary consumers.
- These are eaten by secondary consumers which are eaten by tertiary consumers.
Each stage of the food chain is a trophic level.
Arrows on food chain diagram represent the direction of energy flow.
What is a trophic level?
Each stage of the food chain
What is a food web?
A complex diagram depicting the many food sources of animals within a single habitat.
What is biomass?
The total mass of living material in a specific area at a given time.
How do you measure biomass?
Dry mass per given area in a given time.
Grams per square metre. - area is being sampled.
What can you use to estimate the chemical energy store in dry mass?
Calorimetry
- Bomb calorimetry - sample of dry material is weighed and then burnt in pure oxygen within a sealed chamber called a bomb.
- The bomb is surrounded by a water bath and the heat of combustino caused a small temperature rise in this water.
- We know how much heat is required to raise the temp of 1g of water by 1*C, if we know the volume of water and the temperature rise we can calculate the energy released from the mass of burnt biomass in units such as kJkg^-1
What is the source of energy for ecosystems?
The sun
What proportion of light energy from the sun is captured by green plants?
As little as 1% is captured.
What proportion of the suns energy available to plants is converted into organic matter?
Between 1% and 3%
Why is most of the suns energy not converted to organic matter for photosynthesis?
- 90% of suns energy is reflected back into space by clouds and dust or absorbed by the atmosphere.
- Not all wavelengths of light can be absorbed and used for photosynthesis
- Light may not fall on a chlorophyll molecule
- Factors such as low CO2 levels may limit the rate of photosynthesis.
What proportion of suns energy is reflected back into space by clouds and dust or absorbed by the atmosphere?
90%
Define - Gross primary production
The total quantity of the chemical energy store in plant biomass in a given area or volume in a given time.
What proportion of plants GPP is lost during respiration?
20-50%
What is the net primary productivity?
The chemical energy store which is left when losses due to respiration have been taken into account.
What is the equation for net primary production?
Net primary production (NPP) = gross primary production (GPP) - respiratory losses (R)
What proportion of plants NPP can be used by primary consumers for growth?
10% of net primary production
How much energy is available to secondary and tertiary consumers from their prey?
More efficient than primary (10%)
20% of energy
Why is there a low percentage of energy transferred at each stage of the food chain?
- some of organism is not consumed
- some parts consumed but cannot be digested and therefore lost as faeces
- some energy is lost in excretory materials eg. urine.
- Some energy losses occur as heat from respiration and lost to the environment.
What is explained due to the relative inefficiency of energy transfer between trophic levels?
- Most food chains have only four or five trophic levels because insufficient energy is available to support a large enough breeding population at trophic levels higher than these
- the total mass of organisms in a particular place (biomass) is less than higher trophic levels
- the total amount of energy available is less at each level as one moves up a food chain.
What is the general cycle for nutrients?
- Nutrient taken up by producers as simple inorganic molecules
- producer incorporates nutrient into complex organic molecules
- when the producer is eaten nutients are passed to consumers
- then passes along the food chain when these animals are eaten by other consumers.
- When producers and consumer die their complex molecules are broken down by saprobiontic microorganisms that release the nutrient in its original simple form. Cycle is complete.
Describe the process of the phosphorous cycle
- Phosphorous origins in the seas but brought to surface by the geological uplifting of rocks.
- Weathering and erosion of rocks help phosphate ions dissolve
- they are now available for absorption by plants who incorporate them into their biomass.
- phosphate ions pass to animals who feed on plants.
- excess is excreted and may accumulate in waste material such as guano.
- on death of plants and animal, decomposers break them down and release phosphate ions into water or soil
