5C Energy and Ecosystems Flashcards
What is the ultimate source of energy for almost all organisms and how is it stored?
- sunlight
- stored as chemical energy by plants
Define producer
photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions
Define consumer
- organisms that get their energy by feeding on other organisms rather than directly using energy from sunlight
- animals are consumers
- those that eat green plants are primary consumers, those that eat primary consumers are secondary etc.
Define saprobiont
- group of organisms that break down the complex materials in dead organisms into simpler ones
- in doing so, they release valuable minerals and elements in a form that can be absorbed by plants so they contribute to recycling
What organisms are saprobionts mainly?
bacteria and fungi
Define trophic level
- each level of a food chain is called a trophic level
What do the arrows in a food chain indicate?
direction of energy flow
Define food web
a more complex food chain
Define food chain
describes a feeding relationship involving producers and primary,secondary… etc consumers
Define biomass
- total mass of living material in a specific area at a given time
- presence of varying amounts of water makes fresh mass measuring unreliable
- measuring carbon or dry mass requires death so only done in small quantities but this then isn’t representative
Define calorimetry
a measure of chemical energy in dry mass
Define ecosystem
all the living and non-living components of a particular area
Describe extracellular digestion
- saprobionts (fungi and bacteria) feed on soluble organic matter from dead organisms
- enzymes are secreted onto the dead organism to digest the large molecules
Describe how different biological molecules are digested by saprobionts and how they are absorbed
- proteins are broken down into amino acids through the breaking of peptide bonds by protease
- lipids are broken down into fatty acids and glycerol by breaking ester bonds by lipase
- starch is broken down into simple disaccharides by amylase/carbohydrase
- new small molecules are absorbed by endocytosis then transported within the fungus
What is gross primary product?
- the total quantity of the chemical energy store in plant biomass in a given area or volume in a given time
How much energy from GPP do plants use in respiration?
20-50%
What is net primary productivity?
- the chemical energy store which is left when losses to respiration have been taken into account
What is the formula for NPP?
NPP = GPP - R
NPP = net primary productivity
GPP = gross primary product
R = respiratory losses
What is the formula for the net production of consumers?
N = I - (F+R)
N = net product of consumers
I = ingested food chemical energy
F = energy lost in faeces
R = respiratory losses
What is the net primary production of plants available for?
- plant growth and reproduction
- other trophic levels in the ecosystem eg. consumers and decomposers
Describe the efficiency of different types of consumers based on their use of net primary production in plants
- primary consumers can usually use less than 10% of the NPP
- 2nd and 3rd consumers are more efficient and can transfer around 20% of the energy from their prey into their own bodies
Why can consumers only use a low % of the energy from the NPP of plants or their prey?
- some of the organism isn’t consumed
- some parts are consumed but can’t be digested so are lost in faeces
- some energy is lost in excretory materials eg. urine
- some energy losses occur as heat from respiration (mammals and birds lose more energy this way than reptiles as they need to maintain their body temp)
What does the relative inefficiency of energy transfer between trophic levels explain?
- most food chains only have 4 or 5 trophic levels
- the total amount of biomass decreases at higher trophic levels
- the total amount of energy available at each level decreases the further along a food chain you go
How does energy enter and leave an ecosystem?
- enters as sunlight
- leaves as heat which can’t be recycled
Describe the general sequence of nutrient cycles
- the nutrient is taken up by producers as simple inorganic molecules
- the producer incorporates the nutrient into complex organic molecules
- when the producer is eaten, the nutrient passes into consumers
- it then passes along the food chain when these animals are eaten by other consumers
- when the producers and consumers die, their complex molecules are broken down by saprobiontic microorganisms (decomposers) that release the nutrient in its original simple form
Why are saprobionts extremely important?
- they’re the driving force that ensures nutrients are released for reuse
- without them, nutrients would remain locked up in complex molecules that can’t be taken up by plants
What are mycorrhizae?
- associations between certain species of fungi and the roots of the vast majority of plants
Explain the function of mycorrhizae
- the fungi act as extensions of plant roots and increase the surface area for water and mineral absorption
- the plant benefits from improved water and mineral uptake while the fungus receives organic compounds such as sugars and amino acids from the plant
How do plants take up most of the nitrogen that they need?
- from the soil
- via active transport
- in the form of nitrate ions (NO3-)
What happens after plants take up their nitrogen in the form of nitrate ions?
- converted to amino acids/proteins
How do animals obtain nitrogen-containing compounds?
- by eating and digesting plants
Describe the diagram of the nitrogen cycle
Describe ammonification
- the production of ammonia from organic nitrogen-containing compounds
- including urea (from breakdown of excess amino acids) and proteins, nucleic acids and vitamins (found in faeces and dead organisms)
- saprobiontic organisms feed on faeces and dead organisms, releasing ammonia, which then forms ammonium ions in the soil
Describe nitrification and an example of it
- plants use light energy to produce organic compounds
- some bacteria obtain their energy from chemical reactions involving inorganic ions
- eg. conversion of ammonium ions to nitrate ions (oxidation so it releases energy)
- this is carried out by free-living soil microorganisms called nitrifying bacteria
Describe the conversion of ammonium ions into nitrate ions
- oxidation of ammonium ions to nitrite ions (NO2-)
- oxidation of nitrite ions to nitrate ions (NO3-)
Explain how the rate of nitrifcation is enhanced
- nitrifying bacteria require oxygen to carry out these conversions and so they require a soil that has many air spaces
- to improve productivity, farmers must keep soil structure light and aerated by ploughing
- good drainage also ensures air spaces don’t become filled with water
Describe the process of nitrogen fixation
- a process by which nitrogen gas is converted into nitrogen containing compounds
- can be carried out industrially or naturally
How can nitrogen fixation occur naturally?
when lightning passes through the atmosphere
What are the 2 main types of microorganisms that carry out nitrogen fixation?
- free-living nitrogen-fixing bacteria
- mutualistic nitrogen-fixing bacteria
Describe what happens when free-living nitrogen-fixing bacteria carry out nitrogen fixation
- reduce gaseous nitrogen to ammonia which they then use to manufacture amino acids
- nitrogen-rich compounds are released from them when they die and decay
Describe what happens when mutualistic nitrogen-fixing bacteria carry out nitrogen fixation
- live in nodules on the roots of leguminous plants such as peas and beans
- they obtain carbs from the plant and the plant acquires amino acids from the bacteria
What changes in microorganisms occur during denitrification?
- when soils become waterlogged and have a low oxygen conc, the type of microorganism present changes
- fewer aerobic nitrifying and nitrogen-fixing bacteria are found and more anaerobic denitrifying bacteria are found
Describe what happens in denitrifcation and what conditions are needed
- soil nitrates are converted into gaseous nitrogen
- this reduces the availability of nitrogen-containing compounds for plants
- for land to be productive, the soils must be kept aerated to prevent the buildup of denitrifying bacteria
In the phosphorus cycle, where is the main reservoir of phosphorus?
- in mineral form
- no gas phase of the cycle
- phosphorus exists mostly as phosphate ions in the form of sedimentary rock deposit and these are brought to the surface in the geological uplifting of rocks
Describe the diagram for the phosphorus cycle
