C4.2 Transfer of energy and matter (year 6) Flashcards
long chapter
diff btwn open and closed system :(
open: a system that allows matter in and out
closed: matter does not enter/leave so it must be recycled
Why is sunlight the principal source of energy for most ecosystems?
Almost all life on Earth rely indirectly or directly on sunlight, where photosynthetic organisms such as plants/phytoplankton take inorganic CO2 and convert it to energy-rich sugar C6H12O6.
Basically: Light energy > Chemical energy
- although there are some exceptions, such as ecosystems in caves/below the light penetration in the ocean (hydrothermal vents)
Practice drawing/analysing food chains and webs
should be ok
Definition of food chain/web
A sequence showing the feeding relationships and energy flow between species.
- the arrow direction indicates the flow of chemical energy
Purpose of decomposers in an ecosystem
- To unlock precious nutrients stored in the cells of plants and animals by decay - breaking down non-living food sources such as faeces, dead organisms, fallen leaves, shed skin.
- play a major role in the formation of soil, where the rich black layer of soil (humus) is made of organic debris and nutrients released by decomposers
Decomposers can be saprotrophs or detrivores:
Saprotrophs (e.g. fungi) - secrete enzymes over dead matter and absorb nutrients
Detrivores (e.g. minotaur beatle) - have mouthparts to ingest dead matter and digest in bodies.
What are autotrophs + examples
Autotrophs synthesize organic molecules from inorganic substances/sources, and are known as PRODUCERS in an ecosystem. There are 2 types:
Photoautotrophs: use photosynthesis to convert light energy to glucose. The ability to convert inorganic CO2 which is unusable for consumers, to organic molecules useful for energy and growth is called carbon fixation.
- plants
- cynobacteria
Chemoautrophs: take CO2 and using inorganic compounds such as hydrogen sulfide H2S as an energy source, build more complex molecules that can be used as food.
- sulfur/iron/nitrogen-oxidizing bacteria
Describe the sources of energy for photo/chemoautotrophs
Photoautotroph: Light is used to oxidise H2O by photolysis to produce e- and H+ which are used in the production of ATP and in the generation of glucose.
Chemoautotroph: Oxidation reactions such as Fe2+ > Fe3+ by IRON-OXIDIZING BACTERIA generates electrons which are used in the production of ATP
What are heterotrophs?
Organisms that use carbon compounds obtained from other organisms to synthesise compounds that they require. They are CONSUMERS in an ecosystem.
When heterotrophs consume food, the:
- proteins are digested to amino acids
- lipids to fatty acids
- DNA/RNA into nucleic acids
the nutrients are then ASSIMILATED, where they are integrated/converted into useful substances that the body needs
Describe the trophic levels
Producer > primary consumer > secondary consumer > tertiary consumer > (not necessarily) decomposers
Decomposers ARE NOT CONSUMERS and are the FINAL step in every chain
Units for energy pyramids
kJ m-2 y-1
Reasons for energy loss btwn trophic levels
- not 100% of an organism is consumed as a food source
- not all food swallowed can be digested e.g seeds
- There is considerable HEAT LOSS as a result of CELLULAR RESPIRATION at all trophic levels. Heat is generated whenever ATP is used and is RADIATED away from the organism and lost to surroundings. This is as chemical processes are not 100% efficient and some energy is converted to heat energy
Endotherms need to use a considerably larger amount of energy to maintain body temp compared to ectotherms
What is biomass?
Biomass in a trophic level estimates the mass of all organisms in that tropic level. It is defined as the DRY WEIGHT of an organism.
Biomass decreases with each successive trophic level.
However energy per unit mass DOES NOT DECREASE with successive trophic levels.
Define primary production
The accumulation of carbon compounds in biomass by autotrophs. (when they fix carbon and make carbon compounds that can be used as a food source).
- this is measured in mass of carbon per unit area per unit time, e.g. g m-2 y-2
Define secondary production
The accumulation of carbon compounds in biomass by heterotrophs.
- due to loss of biomass when carbon compounds are converted to CO2 and water in cell respiration, Primary > Secondary production
Illustrate with a diagram how carbon is recycled in ecosystems by photosynthesis, feeding, respiration etc.
Page 584 of Pearson 3rd edition
Describe how ecosystems act as carbon sinks/sources
Carbon source: net producer of CO2. Happens if total net respiration exceeds total net photosynthesis
Carbon sink: absorbs and holds more CO2 than it produces. Happens if total net photosynthesis exceeds total net respiration
Organisms can be carbon sinks/sources as well
Analysis the keeling curve in terms of its general trend and fluctuations.
Fluctuations: due to seasonal changes, reflecting the fact that photosynthetic organisms absorb more CO2 in summer and autumn than in winter and spring.
General trend: The sudden increase in atmospheric CO2 is due to human activity such as combustion of fossil fuels (releases CO2 into atmosphere)
