Energy and Ecosystems Flashcards
What are producers?
Photosynthetic organisms that manufacture organic substances using light energy, water and CO2.
6CO2 + 6H2O + energy light = C6H12O6 + 6O2
green plants are producers
What are consumers?
Organisms that obtain energy by feeding on other organisms rather than using the energy of the sun directly.
Animals are consumers.
What are the 3 types of consumers?
PRIMARY- first in the chain, eat producers (green plants)
SECONDARY- eat primary consumers
TERTIARY- eat secondary
secondary and tertiary are usually predators but sometimes scavengers or parasites.
What are decomposers and what do they do?
When producers or consumers die, the energy they contain can be used by a group of organisms that break down these complex materials into simple components again. In doing so they release valuable minerals and elements in a form that can be absorbed by plants and so contribute to recycling. The majority of work carried out by fungi and bacteria- decomposers but some by earthworms- detritivores.
What is a food chain?
Describes the feeding relationship in which producers are eaten by primary consumers, who are in turn eaten by secondary consumers who are in turn eaten by tertiary.
What is each stage in a food chain referred to as?
A trophic level
What do the arrows on a food chain represent?
Energy flow
What is a food web?
Most animals do not rely on a single food source and within a single habitat many food chains will be linked together to form a food web.
What is the problem with food webs?
They are vary complex, it is likely that all organisms within a habitat, even within an ecosystem, will be linked to other in the food web.
Relationships are not fixed, may change throughout year.
How much of the Sun’s energy available to plants is usually converted into organic matter?
1-3%
Why is most of the Sun’s energy not converted to organic matter by photosynthesis?
- Over 90% of the Sun’s energy is reflected back to space by clouds and dust or absorbed by atmosphere.
- Not all wavelengths of light can be absorbed and used for photosynthesis.
- Light may not fall on a chlorophyll molecule.
- A factor, such as low CO2 levels, may limit rate of photosynthesis.
What is gross production?
The total quantity of energy that plants convert to organic matter. Use 20-50% of energy in respiration
What is net production?
= gross production- respiratory losses.
Why is there a low % of energy transferred between primary, secondary and tertiary consumers? How much is transferred?
Consumer- primary = 10% of energy
primary-secondary/secondary-tertiary = 20%
- Some of the organism is not eaten
- Some parts are eaten but cannot be digested and therefore lost in faeces.
- Some energy lost in excretory materials, such as urine.
- Lost as heat from respiration and directly from body to environment. High in mammals and birds because of high body temp. Energy needed to maintain body temp. when heat constantly being lost.
What does the relative inefficiency of energy transfer explain?
- Most food chains only have 4 or 5 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 at higher trophic levels.
- The total amount of energy stored is less at each level as one moves up a food chain.
What is the energy available at each trophic level usually measured in?
kJm-2year-1
How do you calculate the efficiency of energy transfer between trophic levels?
energy available after transfer/energy available before X100
What are ecological pyramids of number used for?
Shows the number of organisms at each trophic level.
What are the drawbacks of using a number pyramid to describe a food chain?
- No account is taken of size- one giant tree is treated the same as one tiny aphid and each parasite has the same numerical value as its larger host. Means pyramid is not a pyramid or inverted.
- The number of individuals can be so great that it is impossible to represent them accurately on the same scale as other species in the food chain.
What is a pyramid of biomass?
Measure of the biomass at each level.
What is biomass and what is it measured in?
The total mass of plants and animals in a particular space.
grams per square metre (gm-2) AREA
grams per cube metre (gm-3) VOLUME
What are the issues with measuring biomass and how is it solved?
- Fresh mass is quite easy to assess, but the presence of varying amounts of water makes it unreliable. Use of dry mass overcomes problem but organisms must be killed so may not be representative (small sample).
- Only measures organisms present at that time, seasonal differences are not apparent.
