Section 5 Energy Flashcards
What is the main source of energy for an ecosystem?
Sunlight
What is the role of producers, consumers, decomposers, in an ecosystem?
producers = plants, perform photosynthesis, use light energy to make biological molecules
consumers = animals, cannot make their own biological molecules, need to eat plants (primary consumers) or other animals (secondary/tertiary consumers) to obtain biological molecules
decomposers = bacteria and fungi, perform saprobiotic decomposition,
release enzyme onto dead plants/dead animals/animal waste (organic matter) breaking them down to obtain biological molecules
Why do producers (plants) need biological molecules?
Glucose = respiration, store as starch, make cellulose
Amino Acids = make proteins e.g. enzymes
Fatty Acid & Glycerol = make triglyceride as energy store, make phospholipid for membranes
Why do consumers (animals) need biological molecules?
Glucose = respiration, store as glycogen
Amino Acids = make proteins e.g. enzymes
Fatty Acid & Glycerol = make triglyceride as energy store and insulation/protection, make phospholipid for membranes
Why do decomposers (bacteria/fungi) need biological molecules?
Glucose = respiration
Amino Acids = make proteins e.g. enzymes
Fatty Acid & Glycerol = make phospholipid for membranes
How do organisms carry energy?
Main Source = Glucose
Stored as Starch in plants and Glycogen in animals
Alternative Source = Lipids/Fats/Triglycerides and Proteins
How does energy move through an ecosystem?
by the food chain, begin with producer and then moves onto primary consumer, then secondary consumer, then tertiary consumer – with decomposers occurring at each stage (trophic level).
Why is all the light energy not utilised by plants in photosynthesis?
only 2% is used in photosynthesis – of the rest, a certain part misses the chloroplast, the other parts would be reflected or the wrong wavelength
Why is energy lost along a food chain?
not all the glucose made by producers is stored as starch or used to build biomass, as a certain part is lost in respiration (as heat)
not all the stored energy in the plant is transferred to primary consumers as certain parts of the plant are inedible and indigestible (available to decomposers)
of the energy the primary consumer obtains, a certain amount is used in respiration, the rest is stored as glycogen and used to build biomass
not all this stored energy is transferred to secondary consumers due to inedible parts and indigestible parts (available to decomposers)
only 10% of energy is transferred from producer to primary consumer
only 20% of energy is transferred from consumer to consumer
the losses are due to respiration, inedible parts, indigestible parts
higher proportion is transferred from consumer to consumer because consumers are more edible and digestible, producers are made up of cellulose
the higher consumers have the highest respiratory losses as they have increased movement (hunt for food)
Effect of energy loss on a food chain?
places a limit on the length of a food chain, those at the higher trophic levels (just quaternary consumers) would not obtain enough energy from the food it consumes
What is Productivity?
Productivity = Amount of Glucose/Energy available to organism
Primary Productivity = Amount of Glucose/Energy available in Plants
Secondary Productivity = Amount of Glucose/Energy available in Animals
Net Productivity = Gross Productivity – Respiratory [and Faeces] Losses
Gross Primary Productivity is amount of glucose made by plant in photosynthesis,
Net Primary Productivity is amount of glucose stored as starch after respiration
Gross Secondary Productivity is amount of glucose consumed by animal,
Net Secondary Productivity is amount of glucose stored as glycogen after respiration
in all cases, net productivity is the glucose/energy available to organisms at next stage of food chain
respiratory losses are higher in consumers then producers due to movement
and respiratory losses are higher in secondary/tertiary/quaternary consumers then primary consumers as they move more to hunt for food
and respiratory losses are higher in consumers that have to maintain a constant body temperature (endotherms)
What does a Pyramid of Number represent?
number of each type of organism at each trophic level – the numbers decrease as we move up trophic levels due to the loss of energy (not as many individuals can be supported)
can look inverted when it does not take into account mass (e.g. 1 oak tree or millions of fleas)
What does a Pyramid of Biomass represent?
biomass of each type of organism at each trophic level
biomass = mass of living tissue (based on dry mass, water excluded)
biomass includes biological molecules, organelles, cells, tissues, organs
units for biomass (g per m2 for land based animals,
g per m3 for water based animals)
so as we move along a food chain (up trophic levels) there is a loss of energy due to respiration/inedible parts/indigestible parts, so there is less energy to build biomass, so biomass decreases
What does a Pyramid of Energy represent?
amount of energy found at each trophic level
as before, loss of energy occurs along a food chain (respiration, inedible parts, indigestible parts)
What are the units for energy?
kJ/m2 /year
What is photosynthesis?
using light energy to make glucose (and other biological molecules)
occurs in plants and algae (both have chloroplast)
Adaptation of plant for photosynthesis?
leaf located near top of plant = closer to light
leaf is thin and wide = large surface area for light, short diffusion distance for CO2
has many veins = connect to xylem to bring in water
has stomata for gas-exchange (CO2/O2)
has air spaces to support ease of gas-exchange
palisade cells located near top of leaf close to the light
palisade cells are large = large surface area for light
palisade cells have a thin cell wall = short diffusion distance for CO2
palisade cells contain many chloroplasts (site of photosynthesis)
palisade cells have a large vacuole = pushes chloroplast to edge of cell closer to light
Structure of chloroplast?
site of photosynthesis
has a double membrane (outer and inner)
contains discs called thylakoids (contain chlorophyll)
a stack of thylakoids = granum
thylakoids are surrounded by a fluid material called stroma
How does photosynthesis take place?
In 2 stages
light dependent stage = on thylakoids, makes ATP and reduced NADP
light independent stage = in stroma, uses the ATP and reduced NADP to make glucose
Describe the light dependent stage?
light hits chlorophyll
chlorophyll absorbs the light if correct wavelength
electrons become excited and are lost from the chlorophyll (photoionisation)
electrons enter an electron carrier system
electrons move down the system releasing energy
this pumps protons from stroma into thylakoid space
protons accumulate in thylakoid space, then diffuse back into stroma
they pass though ATP Synthase which joins ADP and Pi to make ATP (mechanism = chmeiosmosis, process = photophosphorylation)
the electron ends up by joining with NADP to form reduced NADP
light also hits water
causes photolysis (breakdown of water due to light)
forms: H+, e-, O2
the H+ joins with the reduced NADP (now carries a hydrogen atom: H+ and e-)
the e- replaces electrons lost from chlorophyll
O2 given off as waste
Describe the light independent stage?
involves the calvin cycle
RuBP (5 carbon) joins with CO2 to make 2 lots of GP (3 carbon)
the GP is reduced into TP (3 carbon)
this uses energy from ATP and hydrogen atom from reduced NADP
the TP can be used to reform RuBP (uses energy from ATP)
the TP can also be used to form glucose (carbohydrate)
GP can also be used to form amino acids (proteins) and fatty acids
TP can also be used to form glycerol
fatty acids and glycerol will form a lipid
photosynthesis/calvin cycle = produces all the main biological molecules
