Ecology - 2.2 Energy and Biomass in Ecosystems Flashcards
How is an ecosystem sustained?
By supplies of energy and matter
* Energy enters, flows through and exits
* Matter cycles repeatedly within ecosystems
First law of thermodynamics
As energy flows through ecosystems, it can be transformed from one form to another but cannot be created or destroyed
Photosynthesis
The conversion of light energy to chemical energy in the form of glucose - some of which can be stored as biomass by autotrophs
Cellular respiration
The process of breaking down glucose to release energy for cellular activities
Glucose
A simple sugar that serves as a primary energy source for living organisms
* transformed into ATP - a simpler compound - used for metabolic processes within cells
Biomass
The total mass of living organisms in a given area or ecosystem
Why does cellular respiration produce heat?
It is not 100% effective at transforming energy from carbohydrates into chemicals
* this heat is ultimately lost from the body
Second law of thermodynamics
Energy transformations in ecosystems are inefficient
Why is there usually only 4-5 trophic levels?
The loss of energy at each step is so great that very little usable remains after four or five trophic levels
* usually only 10% of energy transformed is carried on from one trophic level to another
Autotroph
An organism that produces its own food using light or chemical energy
Producer
An organism that makes its own food through photosynthesis or chemosynthesis
Consumer
Obtains energy by eating other organisms or their products
Herbivore
An animal that feeds primarily on plants
Detritivore
An organism that feeds on dead plant and animal matter
Predator
An animal that hunts and kills other animals for food
Parasite
An organism that lives on or in a host organism and benefits at the host’s expense
Saprotroph
An organism that obtains nutrients by absorbing dissolved organic matter
Scavenger
An animal that feeds on dead organisms it has not killed itself
Decomposer
An organism that breaks down dead plant and animal matter, releasing nutrients
How does energy move across the food chain?
Through the passing of carbon compounds and the energy they contain
Food chain
A linear sequence of organisms through which energy and matter flow in an ecosystem
Trophic level
A feeding position in a food chain or web
Why is energy lost between each trophic level? (3)
- Of what is harvested, not all is consumed
- Of what is consumer, not all is absorbed (some excreted)
- Of what is absorbed, not all is stored (some lost as heat through cellular respiration)
Gross productivity
Total rate if energy captured by producers in an ecosystems
Net productivity
The rate of energy storage by producers or consumers after accounting for respiration
Food web
A network of interconnected food chains in an ecosystem
How to find (dry) biomass and energy from biological samples?
- Carefully collect the samples including all roots
- Gently rine all soil
- Weight the sample
- Place it in an incubator for 24-28 hours
- Weight the sample again
- Repeat steps 4 and 5 untilt the mass does not change
Limitations of dry biomass calculation (name 2)
- Hard to get truly representative ecosystem samples
- Destructive sampling prevents future study of organisms
Benefits of dry biomass calculation (name 2)
- Removes water content variability between samples
- Simple and inexpensive
Ecological pyramid
A graphical representation of energy, biomass or numbers at different trophic levels
Pyramid of numbers
An ecological pyramid showing the number of organisms at each trophic level
Pyramid of biomass
An ecological pyramid representing the total dry mass of organisms at each trophic level
Pyramid of energy
Depicting the amount of energy at each trophic level
Bioaccumulation
The gradual build-up of substances in an organism’s tissue over time
Biomagnification
The increasing concentration of substances in organisms at higher trophic levels
What human activities have an impact on flows of energy and transfer of matter in ecosystems? (4)
- burning fossil fuels
- deforestation
- urbanisation
- agriculture
How does deforestation impact food chains?
Causes losses of biomass when trees are removed from the system and photosynthesis decreases
