Energy in Ecosystems II
IB syllabus: 2.1.1-2.1.5, 2.2.1, 2.2.3
AP syllabus
Ch. 4
Syllabus Statements
• 2.1.1: Distinguish between biotic and abiotic (physical) components of an ecosystem
• 2.1.2: Define trophic level• 2.1.3: Identify and explain trophic levels in food
chains and food webs selected from a local environment
• 2.1.4: Explain the principles of pyramids of numbers, pyramids of biomass and pyramids of productivity, and construct pyramids from given data
• 2.1.5: Discuss how the pyramid structure effects the functioning of an ecosystem
Syllabus Statements• 2.2.1: List the significant abiotic (physical)
factors of an ecosystem
• 2.2.3: Describe and evaluate methods for measuring at least three abiotic factors in an ecosystem
• 2.3.3: Describe and evaluate methods for estimating the biomass of trophic levels in an ecosystem
Syllabus Statements
• 2.5.1: Explain the role of producers consumers and decomposers in an ecosystem
• 2.5.3: Describe and explain the transfer and transformation of energy as it flows through an ecosystem
vocabulary
• Abiotic factor
• Biomass
• Biotic factor
• Ecosystem
• Standing crop
• Trophic Level
Ecosystems
• Are communities and their interactions with the abiotic environment
Ecosystem Components
2 parts
– Abiotic – nonliving components
(water, air, nutrients, solar energy)
– Biotic – living components
(plants, animals, microorganisms)
Biota
Terrestrial Ecosystems Aquatic Life Zones
• Sunlight
• Temperature
• Precipitation
• Wind
• Latitude (distance from equator)
• Altitude (distance above sea level)
• Fire frequency
• Soil
• Light penetration
• Water currents
• Dissolved nutrient concentrations (especially N and P)
• Suspended solids
• Salinity
Significant abiotic factors
What abiotic factors effect this Aquatic food chain?
The abiotic influence
• Species thrive in different physical conditions
• Population has a range of tolerance for each factor
• Optimum level best for most individuals
• Highly tolerant species live in a variety of habitats with widely different conditions
Po
pu
lati
on
Siz
e
Low High Temperature
Zone ofintolerance
Zone ofphysiological stress
Optimum range Zone ofphysiological stress
Zone ofintolerance
Noorganisms
Feworganisms
Lower limitof tolerance
Abundance of organismsFew
organismsNo
organisms
Upper limitof tolerance
The Law of Tolerance: The existence, abundance and distribution of a species in an ecosystem are determined by whether the levels of one or
more physical or chemical factors fall within the range tolerated by that species
Abiotic factors may be Limiting Factors (2.6.1)
• Limiting factor – one factor that regulates population growth more than other factors
• Too much or too little of an abiotic factor may limit growth of a population
• Determines K, carrying capacity of an area
• Examples– Temperature, sunlight, dissolved oxygen
(DO), nutrient availability
Techniques to measure abiotic factors• Terrestrial
– Light intensity or insolation ( lux) – light meter; consider effect of vegetation, time of day…
– Temperature (°C) – themometer; take at different heights, points, times of day, seasons…
– Soil moisture (centibars) – tensiometer or wet mass dry mass of soil; consider depth of soil sample, surrounding vegetation, slope…
• Aquatic (specify marine or fresh)– Salinity (ppt) – hydrometer;
consider role of evaporation– Dissolved Oxygen (mg/L) – DO
meter, Winkler titration; consider living organisms, water circulation,
– pH – pH probe or litmus paper; consider rainfall input, soil and water buffering capacity
– Turbidity (FTU) – Secchi disk or turbidity meter; consider water movement,
Techniques (2.2.2)
• For any of them you should know the following
1. What apparatus is used for measurement and its units
2. How it would vary or be used to measure variation along an environmental gradient
3. Scientific concerns about its implementation
4. Evaluation of its effectiveness or limitations
Terminology and Roles of Biota
• Producers (Autotrophs) – Through photosynthesis convert radiant to chemical energy (energy transformation)
• Consumers (Heterotrophs) – Must consume other organisms to meet their energy needs– Herbivores, Carnivores, Omnivores, Scavengers,
Detritivores
• Decomposers – Break down organisms into simple organic molecules (recycling materials)
Food chains and Food webs• Food chain Sequence of organisms each of which
is the source of food for the next • Feeding levels in the chain Trophic levels
– First trophic level = producer– Second trophic level = consumer, herbivore– Third trophic level = consumer, carnivore– Highest trophic level = top carnivore– Arrows indicate direction of energy flow!!!– Decomposers are not included in food chains and webs
• For complexity of real ecosystem need food web which shows that individuals may exist at multiple trophic levels in a system (omnivores)
Figure 53.10 Examples of terrestrial and marine food chains
Local examples
Trophic Level Estuary system Everglades habitat
Producer Turtle grass Phytoplankton
Primary Consumer Grass shrimp Zooplankton
Seconday Consumer Pin fish Blue gill
Tertiary Consumer Spotted Sea trout Bass
Quarternary Consumer Osprey Racoon
6th trophic level Aligator
Food Web
• Summarizes the trophic relationships of a community through a diagram
• Food chain web, once a given species enters the web at multiple trophic levels
• Most consumers are not exclusive to one level (ex. we are omnivores)
Figure 53.11 An antarctic marine food web: Identify the trophic levels
Antarctic pelagic (open ocean) community found in
seasonally productive Southern Ocean
1. Zooplankton: dominant herbivores in Antarctic are euphausids (krill) and herbivorous plankton called copepods
2. The zooplankton are eaten by carnivores including penguins, seals, fish, baleen whales
3. Carnivorous squid feeding on fish and zooplankton are important link in food web
4. Seals and toothed whales eat squid5. During whaling years humans became top predators
in the system6. Entire food web depends on phytoplankton
photosynthesizing microorganisms obtaining energy from the sun
Food Webs
• Food webs are limited by the energy flowing through them and the matter recycling within them
• Ecosystem is an energy machine and a matter processor
1. Autotrophs: make their own food (plants algae & photosynthetic prokaryotes)
2. Heterotrophs: directly or indirectly depend on photosynthetic output of primary producers
Producers
• Transform energy into a usable form
• Starting form may be light energy or inorganic chemicals
• Turned into organic chemical energy
• This is the form that is used at other trophic levels
Photoautotrophs
Consumers
• Heterotrophs: get energy from organic matter consumed
• Primary, Secondary & Tertiary consumers• Herbivores primary consumers, eat
plant material e.g. – termites, deer• Carnivores other consumer levels, eat
animal material e.g. eagles, wolves• Omnivores consumers eating both e.g.
bears
Figure 53.0 Lion with kill in a grassland community
Decomposition
• Decomposers obtain energy by breaking down glucose in the absence of oxygen
• Anaerobic respiration or fermentation
• End products = methane, ethyl alcohol, acetic acid, hydrogen sulfide
• Matter recycling inorganic nutrients returned to producers
MushroomWoodreduced
to powder
Long-hornedbeetle holes
Bark beetleengraving
Carpenterant
galleries
Termite andcarpenter
antwork
Dry rot fungus
Detritus feeders Decomposers
Time progression Powder broken down by decomposersinto plant nutrients in soil
Decomposition Process
Consumers or Decomposers
• Detritivores = get their energy from detritus, nonliving organic material remains of dead organisms feces, fallen leaves, wood
• May link producers to consumers– Dung beetles, earth worms
• Saprotrophs = feed on dead organic material by secreting digestive enzymes into it and absorbing the digested products
• Producers can reassimilate these raw materials– Fungi (mold, mushrooms), bacteria
Energy in living systems
• Food chains, webs and pyramids, ultimately show energy flow
• Obey the laws of thermodynamics
• Obey systems laws – input, transfer, transformation, output
Thermodynamics Review
Universal laws that govern all energy changes in the universe, from nuclear reactions to the buzzing of a bee.
a) The 1st law: Energy can be transferred and transformed but not created or destroyed
- Energy flow in the biological world is unidirectional:– Sun energy enters system and replaces energy lost from heat– Energy at one trophic level is always less than the previous level
b) The 2nd law: Energy transformations proceed spontaneously to convert matter from a more ordered, less stable form, to a less ordered, more stable form
- Energy lost as heat from each level- Energy at one level less than previous because of these lossed
Energy Flow in Communities
• Energy unlike matter does not recycle through a community it flows
• Energy comes from the sun• Converted by autotrophs into sugars• Amount of Light energy converted into chemical
energy by autotrophs in a given time period Gross Primary Production GPP
• The amount to pass on to consumers after plants have used their share Net Primary Production NPP
• NPP = GPP - R
The Source of All energy on Earth is the …
Figure 3-10Page 52
Ene
rgy
emitt
ed f
rom
sun
(K
cal/c
m2/m
in)
0
5
10
15
0.25 1 2 2.5 3
Wavelength (micrometers)
VisibleLight is The usableEnergy
What is the sun?
• 72% hydrogen, 28% helium
• Temp and pressure high so H nuclei fuse to form He releasing energy
• Fusion energy radiated as electromagnetic energy
• Earth receives 1 billionth of the suns Energy
• Most reflected away or absorbed by atmospheric chemicals
Energy to Earth
• 30% solar energy reflected back into space by atmosphere, clouds, ice
• 20% absorbed by clouds & atmosphere• 50% remaining
– Warms troposphere and land– Evaporates and cycles water– Generates wind
• < 0.1% captured by producers for photosynthesis• Energy eventually transformed to heat and trapped
by atmosphere “Natural Greenhouse Effect”• Eventually reradiated into space
So if sunlight in = sunlight + heat out
What state is the system in?
Stable Equilibrium
Summary of solar radiation pathways
• Incident radiation comes in, it is then…– Lost by reflection (ice caps) and absorption (soil,
water bodies)– Converted from light to chemical energy
(photosynthesis in producers)– Lost as chemical energy decreases through
trophic levels– Through an ecosystem completely converted
from light energy into heat– Reradiated as heat back to the atmosphere
Energy Flow II
• Energy measured in joules or kilojoules per unit area per unit time
• Energy conversion never 100% efficient
• Some energy lost as heat
• Of visible light reaching producers, only 1% is converted to chemical energy
• Other levels are 10% efficient – only assimilate %10 of energy from previous level
Figure 54.1 An overview of ecosystem dynamics
Energy Flow and Food webs
• Biomass = the total dry weight of all organisms in one trophic level
• Usable energy degraded with each transfer– Loss as heat, waste, metabolism
• % transferred = ecological efficiency ranges from 5-20%
• More trophic levels = less energy available at high levels
If that loss happens at every trophic level think about how much energy is lost.
Makes the lower trophic levels most efficient in terms of overall energy available in the system
Energy Flow through Producers
• Producers convert light energy into chemical energy of organic molecules
• Energy lost as cell respiration in producers then as heat elsewhere
• When consumers eat producers energy passes on to them
• In death organic matter passes to saprophytes & detritivores
Energy Flow through Consumers• Obtain energy by eating producers or other
consumers
• Energy transfer never above 20% efficient, usually between 10 – 20%
• Food ingested has multiple fates1. Large portion used in cell respiration for
meeting energy requirements (LOSS)
2. Smaller portion is assimilated used for growth, repair, reproduction
3. Smallest portion, undigested material excreted as waste (LOSS)
Figure 54.10 Energy partitioning within a link of the food chain
Energy flow through Decomposers
• Some food is not digested by consumers so lost as feces to detritivores & saprophytes
• Energy eventually released by process of cell respiration or lost as heat
Construct and analyze energy flow diagrams for energy movement through ecosystems
• Trophic level boxes are storages – biomass per area (g m-2)
• Energy Flow in arrows – rate of energy transfer
(g m-2 day-1)
Energy values in KJ m-2y-1
Often the size of the boxes and arrows is proportional to their amount
Using Pyramids to express ecosystem dynamics
EnergyInput:
20,810 + 1,679,190
1,700,000 (100%)
Energy Output
Total Annual Energy Flow
Metabolic heat,export
Waste,remains
1,700,000kilocalories
Producers
Herbivores
Carnivores
Topcarnivores
Decomposers,detritivores
EnergyTransfers
20,810(1.2%)
Incoming solar energynot harnessed
1,679,190(98.8%)
4,245 3,368 13,197
720 383 2,265
90 21 272
5 16
Top carnivores
Carnivores
Herbivores
Producers
5,060
Decomposers/detritivores
20,810
3,368
383
21
© 2004 Brooks/Cole – Thomson Learning
Pyramids
• Graphic models of quantitative differences between trophic levels
• By second law of thermodynamics energy decreases along food webs
• Pyramids are thus narrower as one ascends– Pyramids of numbers may be different large
individuals at low trophic levels – large forests– Pyramids of biomass may skew if larger
organisms are at high trophic levels biomass present at point in time – open ocean
Losses in the pyramid
• Energy is lost between each trophic level, so less remains for the next level– Respiration, Homeostasis, Movement, Heat
• Mass is also lost at each level– Waste, shedding, …
Pyramids of Biomass
• Represents the standing stock of each trophic level (in grams of biomass per unit area g / m2)
• Represent storages along with pyramids of numbers
How do we get the biomass of a trophic level to make these pyramids?
• Why can’t we measure the biomass of an entire trophic level?
• Take quantitative samples – known area or volume• Measure the whole habitat size• Dry samples to remove water weight• Take Dry mass for sample then extrapolate to entire
trophic level• Evaluation It is an estimate based on assumption
that – all individuals at that trophic level are the same– The sample accurately represents the whole habitat
Abandoned Field Ocean
Tertiary consumers
Secondary consumers
Primary consumers
Producers
© 2004 Brooks/Cole – Thomson Learning
Pyramids of Biomass
Pyramids of Numbers
• Needs sampling similar to Biomass and therefore has the same limitations
• Also measures the storages
Grassland(summer)
Temperate Forest(summer)
Producers
Primary consumers
Secondary consumers
Tertiary consumers
Pyramids of Numbers
© 2004 Brooks/Cole – Thomson Learning
Pyramids of productivity
• Flow of energy through trophic levels• Energy decreases along the food chain
– Lost as heat
• Productivity pyramids ALWAYS decrease as they go higher – 1st and 2nd laws of thermodynamics
• Shows rate at which stock is generated at each level
• Productivity measured in units of flow (J / m2 yr or g / m2 yr )
Figure 54.11 An idealized pyramid of net production
Figure 54.14 Food energy available to the human population at different trophic levels
Efficiency of trophic levels in relation to the total energy
available decreases with higher numbers
But efficiency of transfer always remains around that 10% rule
Take an Economic Analogy
1. If you look at the turnover of two retail outlets you can’t just look at the goods on the shelves
• Rates of stocking shelves and selling goods must be known as well
2. A business may have substantial assets but cash flow may be limited
3. So our pyramids of Biomass and numbers are like the stock or the assets and our pyramids of Productivity are like our rate of generation or use of the stock
How does pyramid structure effect ecosystem function?
1. Limited length of food chains• Rarely more than 4 or 5 trophic levels• Not enough energy left after 4-5 transfers to
support organisms feeding high up• Possible exception marine/aquatic systems
b/c first few levels small and little structure
2. Vulnerability of top carnivores• Effected by changes at all lower levels• Small numbers to begin with• Effected by pollutants & toxins passed
through system
Effects II: Biomagnification
1. Mostly Heavy metals & Pesticides• Insoluble in water, soluble in fats, • Resistant to biological and chemical degradation,
not biodegradable
2. Accumulate in tissues of organisms3. Amplify in food chains and webs4. Sublethal effects in reproductive & immune
systems5. Long term health effects in humans include
tumors, organ damage, …
Water0.000002 ppm
Phytoplankton0.0025 ppm
Zooplankton0.123 ppm
Rainbow smelt1.04 ppm
Lake trout4.83 ppm
Herring gull124 ppm
Herring gull eggs124 ppm
Practice Problems
• The insolation energy in an area of rainforest is 15,000,000 cal/ m2/day. This is the total amount of sun energy reaching the ground. The GPP of the producers in the area, large rainforest trees, is 0.0050 g/cm2/day and 25% of this productivity is consumed in respiration. By laboratory tests we found that 1 gram of rainforest tree contains 1,675 calories of energy.
• A. What trophic level are the trees considered? (2 point)
• B. Calculate the NPP of the system. (5 point)• C. Find the efficiency of photosynthesis. (5 point)• D. If a monkey population eats the fruit from the
trees how many square meters of forest will each individual need to feed in if they require 400 calories each day?
Practice
• Create a food web for the following FL organisms
largemouth bass, panther, racoon, white tailed deer, bullfrog, shiner (small fish), water beetles, zooplankton, phytoplankton, marsh grass, rabbit, water moccasin, dragonfly, duckweed, egret, wood duck,
Human
Blue whale Sperm whale
Crabeater seal
Killerwhale Elephant
seal
Leopardseal
Adéliepenguins Petrel
Fish
Squid
Carnivorous plankton
Krill
Phytoplankton
Herbivorouszooplankton
Emperorpenguin
Practice:
Identify the trophic levelsIn the food web
• http://www.indianriverlagoon.org/stats.html