2.2: Energy And Biomass In Ecosystems Flashcards
What is an example of a food chain?
(Sun) -> primary producer-grass -> primary consumer-grasshopper -> secondary consumer-frog -> tertiary consumer-snake -> quaternary consumer-eagle
All energy originally from sun
(- chemosynthetic bacteria)
Définition of trophic level
Position that an organism occupies in a food chain/web
1 -> producers
2 -> primary consumers
3 -> secondary consumers
4 -> tertiary consumers
What are producers?
Typically plants or algae
Produced their own food using photosynthesis
Chemical energy stored in produced is transferred to consumer as they eat each other
What is a herbivore?
Consumer that feeds primarily on plant and plant-derived material
Ex:
Deer - graze on grasses, leaves, shrubs
Rabbits - consume grasses, herbs, vegetables
What is detritivore?
Consumers that consume decomposing organic matter and help break it down
Ex:
Earthworms: feed on decaying plant material and enhance soil structure
Dung beetles: consume animal dung, aiding in nutrient recycling
What are predators?
Consumers that hunt and consume other organisms for food
Apex predator: predator on the top of the food chain (carnivores/omnivores with no predators) -> energy passed onto decomposers
Ex:
Lions: prey on various herbivores such as gazelles and zebras
Wolves: hunt animals like deer and elk in packs
What are parasites?
Consumers that depend on a host organism for survival
Often harms but does not immediately kill
Ex:
Tapeworms: live in the intestines of mammals, absorbing nutrients from the host’s food
Mosquitoes: feed on the blood of animals, including humans, for nourishment
What are saprotrophs?
Consumers that decompose dead organic matter externally and absorb nutrients
Ex:
Fungi: break down dead plant material, such as fallen leaves and wood, into simpler compounds
Bacteria: decompose organic matter, releasing nutrients for plant uptake
What are decomposers?
Consumers that break down organic matter into simpler substances, playing a vital role in nutrient recycling
What are scavengers?
Consumers that consume dead animal carcasses, helping to clean up ecosystems
Ex:
Vultures: feed on the remains of dead animals, scavenging carrion
Hyenas: opportunistic scavengers known to consume a wide range of animal remains
What are consumers?
organisms that obtain energy and nutrients by consuming other organisms or organic matter which is living or recently killed
What are food chains?
A model that shows the flow of energy through the trophic levels of a feeding relationship
Boxes -> stored energy
Arrows -> transfer of energy
Carbon compounds (+elements they contain) -> passed from producer to primary consumers…etc.
What is a food web?
Network of interconnected food chain in a habitat
More realistic way of showing connections
Give more info that food chains
Shows interdependence
What is autotrophy? What are the subcategories?
Autotrophy: self feeding -> organisms which produce their own food from organic molecules
Producers:
Photoautotrophy: photosynthesis -> green plants, phytoplankton, algae
Chemoautotrophy: chemosynthesis -> deep sea chemosynthetic bacteria
What is heterotrophy? What are the subcategories?
Heterotrophy: other source feeding -> organisms which derive energy from other living organisms
primary: eat producers - herbivores
secondary +: eat other consumers - omnivores/carnivores
decomposers: derive energy from non-living organic matter
detritivores: ingest non-living organic matter, ingest then digest - mouth -> earthworms, woodlice
saprotrophs: lives on or in non-living organic matter secreting digestive enzymes into it and absorbing digestive products, digest then absorb -> bacteria, fungi
Energy flow in ecosystems
Ecosystems -> rely on steady supply of energy and matter to maintain structure and function
Energy -> essential for driving biological process while matter cycles through ecosystem
Ecosystems -> open -> exchange energy and matter with their surroundings
energy in from sun -> chemical energy by producers -> goes through trophic levels (some lost as heat) -> décomposer break down matter -> release energy and retiring nutrients to enviroment
What is the first law of thermodynamics? How does it apply to energy flow?
Energy can neither be created nor destroyed, it can only be transformed from one form to another
Principle conservation of energy -> energy entering system = energy out of system
Demonstrated in food chains within ecosystems
What is the second laws of thermodynamics? How does this apply to energy flow?
Energy conversion are never fully efficient and the more conversions there are, the greater the inefficiency
Ex:
Concentrated light energy -> dispersed/disordered (heat energy)
OR
Absorbed by producers -> very inefficient
-> reflection
-> transmission
-> inefficient energy transfer during photosynthesis
Energy to plant biomass -> inefficiently transferred along the food chain due to respiration (biggest loss) /waste/heat energy
AS A RESULT:
Inefficient energy transfer
Food chains short (no more than 5 trophic levels)
How to calculate efficiency in food chains
Efficiency = percentage
Using biomass:
amount of biomass transferred/amount of biomass available x100 = efficiency
Using energy:
amount of energy transferred/total energy available x100 = efficiency
Unit: (k)J/m^2/yr
Why is the total amount of organic matter transferred never 100%?
Not all food available to a given trophic level is harvested
Of what is harvested -> not all consumed
Of what is consumed -> not all absorbed
Of what is absorbed -> not all stored
What process do producers perform to produce chemical energy?
Majority of ecosystems: light energy to chemical energy via photosynthesis
- producers/autotrophs: plants, algae, photosynthetic bacteria use to produce their own food
Photosynthesis:
CO2 + water —(light + chlorophyll)—> glucose + oxygen
Produces raw materials for producing biomass
- glucose energy store + basic starting material for organic molecule (from CO2)
- most sugars synthesized used as respiratory substrates
- very important in many ecosystems with sunlight
What are the inputs/outputs/processes/transformations in photosynthesis?
Input: sunlight (energy source), CO2 and water
Output: glucose and oxygen
Processes: inside chloroplast -> chlorophyll capture certain visible wavelengths of sunlight energy + stores as chemical energy
Transformations: light energy -> stored chemical energy (form of glucose)
What is respiration?
Conversation of organic matter into carbon dioxide and water in living organisms, releasing energy
- cellular respiration releases energy from glucose bu converting it into chemical form -> easily used in active processes
Glucose + oxygen -> CO2 + water
Chemical energy released -> heat
- heat generated because cell respiration is not 100% efficient
- heat generated -> cannot be transformed into chemical energy -> lost from body
- heat energy released increase entropy of ecosystem (2nd law of thermodynamics) -> allow organism to have low entropy
What are the inputs/outputs/processes/transformations in respiration?
Input: organic matter (glucose) and oxygen
Output: release of energy for work + heat
Processes: oxidation processes inside cells
Transformations: stored chemical energy released during cellular respiration -> heat
What is bioaccumulation?
The gradual buildup of persistent/non-biodegradable pollutants in a living organism/trophic level because it cannot be broken down
Chemicals stored in fatty tissue of animal
- stored in animal -> not used or passed as waste
When another animal eats -> that animal gains chemical accumulation
What is biomagnification?
The increasing concentration of substances in successive trophic levels
- predator will have higher concentration of a chemical compared to prey
Type of chemicals that biomagnify:
Often chlorinated hydrocarbons (used to produce pesticides)
Heavy metals
Other organic compounds used in industry
What are POPs?
Persistent organic pollutants
- type of chemical most likely to biomagnify
Do not degrade/break down easily in environment
Can last for decades
Some have been banned, still problematic
What are microplastics?
Where so they come from?
How do they enter the ecosystem?
Any piece of plastic less than 5 mm long
Come from:
Degradation of larger pieces of plastic
Microbeads found in cosmetics
Synthetic clothes
Enter ecosystem:
Plastic in landfills
Littering
Products than go down drains
Why are microplastics bad?
Absorb and release toxic chemicals
- PCBs, pesticides, heavy metals
- increase transmission of pollutants in food chains
Mistaken for food by organisms
- ingested -> blockage in gastrointestinal tract -> think they arefull -> starve
Biomagnification/accumulation
- Smaller organisms consume microplastics containing pollutants -> toxins accumulate in their bodies
- larger predators consume -> biomag -> concentration increases
Negative consequences:
Ex: oysters exposed to microplastics contain pollutants:
- lower feeding rates
- altered growth patterns
- reduced reproductive success
What is gross productivity?
Total gain in biomass by an organism or community in a given area or time period
- includes energy captured by organisms
Ex: pond ecosystem -> total amount of energy captured by aquatic plants + other species in pond = gross productivity of that ecosystem
What is net productivity?
The amount of energy or biomass remaining after losses due to cellular respiration
- energy losses removed from gross productivity
- reflects energy available form growth + reproduction
Ex: plant capture 1000 kJ of energy via photosynthesis (GP)
Use 300 kJ for cellular respiration -> NP is 700 kJ
Losses due to respiration greater in consumers than in producers
- consumer do more energy intensive activities
How does net productivity relate to sustainable yield?
NP of any organism/trophic level -> maximum sustainable yield that can be harvested without decreasing the availability of resources for the future
Maintain ecosystem stability -> avoid harvest beyond sustainable yield of populations
Ex: fisheries management
- sustainable yield of fish determined by considering NP of fishery
- harvest beyond that -> over exploitation and depletion of stock
- affect both ecosystem itself and human livelihoods
Measuring biomass: measurement of dry mass
Collect samples of organisms from a trophic level -> dry (in oven to remove all water) -> sample weighed and measured
Used to estimate total biomass of the population that have been sampled
- dry mass approximately equal to mass of organic matter (water represent majority of inorganic matter)
Ex: dry mass of 1 daffodil plant is 0.1 kg
Dry mass of 200 daffodils -> 20 kg (20 x 0.1)
Dry mass of 1m^2 is 0.2 kg
-> grass had dry biomass of 0.2 kg/m2
Grass field 200 m2 -> biomass of field is 40 kg
Measuring biomass: controlled combustion
Involves burning a known quantity of biomass and measuring the heat produced
Know heat value of biomass -> possible to estimate total biomass of population/trophic level based on amount of heat produced
Calorimeter:
Burning sample heats known volume of water
Change in temp -> estimate of chemical energy is sample
Measuring biomass: extrapolation from samples
Estimate biomass by taking small samples of population and extrapolating data
Useful when dealing with large/difficult to sample populations
Data from this method can be contributed using ecological pyramids
Measuring biomass: limits of calorimetry
Longtime to fully dehydrate biological sample to find dry mass
- sample heated at low temp to ensure it doesn’t burn
- depends on sample size -> could take days
Precise equipment needed
- not available, expensive
- precise digital balanced (measure mass of sample)
- > detect small changes
More simple/basic -> less accurate
- heat energy lost/not transferred efficiently
- bomb calorimeter ensure all heat energy is transferred to water -> accurate
What is a pyramid of numbers?
Shows how many organisms are in each level of the food chain
- width of box indicates the number of organisms at that trophic level
Usually number of organisms decreases along food chain
- due to decrease in available energy since energy is lost at each level
- usually narrower at top
But doesn’t have to be
- when lower trophic level have large organism ex oak tree pyramid can be inverted
What is a pyramid of biomass?
Shows how much mass the organisms at each trophic level would have without including all the water that is in the organism (dry mass)
2nd law of thermodynamics: quantities of biomass decrease along chain -> pyramid narrower at top
Occasionally they can be inverted:
- happen due to marked sessional variations
- ex: marine ecosystems
-> 1 trophic level (phytoplankton) -> lower than mass of primary consumer (zooplankton)
-> productivity of PP can vary depending on sunlight intensity
What is a pyramid of energy/productivity?
Show the flow of energy through trophic levels indicating the rate at which that energy is being generated
- illustrate the amount of energy/biomass of organisms at each trophic level / unit area / unit time
Measured in units of flow
- the units are mass or energy per metre squared per year (g/kg m2yr1or J/kJ m2yr1)
- length of each box/bar represents quantity of energy present
Always widest at base and decrease as you go up
- bc 2nd law of thermodynamics
- large amount of energy in producers
- move up -> quantity of energy decreases -> not all energy transferred (around 10% passed on)
-> due to incomplete consumption/digestion, heat loss, excretion
