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