2.2: Energy And Biomass In Ecosystems

Question 1

What is an example of a food chain?

Answer 1

(Sun) -> primary producer-grass -> primary consumer-grasshopper -> secondary consumer-frog -> tertiary consumer-snake -> quaternary consumer-eagle

All energy originally from sun
(- chemosynthetic bacteria)

Question 2

Définition of trophic level

Answer 2

Position that an organism occupies in a food chain/web

1 -> producers

2 -> primary consumers

3 -> secondary consumers

4 -> tertiary consumers

Question 3

What are producers?

Answer 3

Typically plants or algae
Produced their own food using photosynthesis

Chemical energy stored in produced is transferred to consumer as they eat each other

Question 4

What is a herbivore?

Answer 4

Consumer that feeds primarily on plant and plant-derived material

Ex:
Deer - graze on grasses, leaves, shrubs
Rabbits - consume grasses, herbs, vegetables

Question 5

What is detritivore?

Answer 5

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

Question 6

What are predators?

Answer 6

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

Question 7

What are parasites?

Answer 7

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

Question 8

What are saprotrophs?

Answer 8

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

Question 9

What are decomposers?

Answer 9

Consumers that break down organic matter into simpler substances, playing a vital role in nutrient recycling

Question 10

What are scavengers?

Answer 10

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

Question 11

What are consumers?

Answer 11

organisms that obtain energy and nutrients by consuming other organisms or organic matter which is living or recently killed

Question 12

What are food chains?

Answer 12

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.

Question 13

What is a food web?

Answer 13

Network of interconnected food chain in a habitat
More realistic way of showing connections

Give more info that food chains
Shows interdependence

Question 14

What is autotrophy? What are the subcategories?

Answer 14

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

Question 15

What is heterotrophy? What are the subcategories?

Answer 15

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

Question 16

Energy flow in ecosystems

Answer 16

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

Question 17

What is the first law of thermodynamics? How does it apply to energy flow?

Answer 17

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

Question 18

What is the second laws of thermodynamics? How does this apply to energy flow?

Answer 18

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)

Question 19

How to calculate efficiency in food chains

Answer 19

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

Question 20

Why is the total amount of organic matter transferred never 100%?

Answer 20

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

Question 21

What process do producers perform to produce chemical energy?

Answer 21

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

Question 22

What are the inputs/outputs/processes/transformations in photosynthesis?

Answer 22

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)

Question 23

What is respiration?

Answer 23

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

Question 24

What are the inputs/outputs/processes/transformations in respiration?

Answer 24

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

Question 25

What is bioaccumulation?

Answer 25

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

Question 26

What is biomagnification?

Answer 26

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

Question 27

What are POPs?

Answer 27

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

Question 28

What are microplastics? Where so they come from? How do they enter the ecosystem?

Answer 28

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

Question 29

Why are microplastics bad?

Answer 29

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 are full -> 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

Question 30

What is gross productivity?

Answer 30

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

Question 31

What is net productivity?

Answer 31

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

Question 32

How does net productivity relate to sustainable yield?

Answer 32

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

Question 33

Measuring biomass: measurement of dry mass

Answer 33

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

Question 34

Measuring biomass: controlled combustion

Answer 34

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

Question 35

Measuring biomass: extrapolation from samples

Answer 35

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

Question 36

Measuring biomass: limits of calorimetry

Answer 36

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

Question 37

What is a pyramid of numbers?

Answer 37

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

Question 38

What is a pyramid of biomass?

Answer 38

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

Question 39

What is a pyramid of energy/productivity?

Answer 39

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 m2 yr1 or J/kJ m2 yr1) - 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