Overview:A) THE BIOSPHEREB) POPULATION ECOLOGYC) COMMUNITY ECOLOGYD) ECOSYSTEM ECOLOGYE) THE CARBON & NITROGEN CYCLESF) ECOLOGICAL TECHNIQUESG) SIMPSON’S INDEXH) LOCAL ECOLOGYI) BIOLOGICAL DIVERSITY
Two processes proceed concurrently in ecosystems: ENERGY FLOW Light Heat SUN Biotic component energy energy nutrients Abiotic component The movement of: 1. ENERGY 2. NUTRIENT ELEMENTS linear cyclic renewed all the time originates from the abiotic component
Some Energy Roles
Why is the SUN considered the ultimate source of energy?
Provides energy to almost all organisms. These organisms get energy indirectly from the sun. Plants get energy directly from the sun.
Some Energy Roles Producers: harness energy from the sun e.g. plants, algae
Some Energy Roles Consumers: organisms that eat something else e.g. animals
Some Energy Roles Decomposers: return energy to the environment e.g. fungus, bacteria
the terms detritivore and decomposer are often used interchangeably Detritivores - small animals like earthworms, crabs that feed on detritus springtail Detritus: fragments of decaying material
What do decomposers and detritivores have in common?BOTH receive energy from decayed matter Fungus: DECOMPOSER Spider crab: DETRITIVORE
How do they differ? Detritivores in fact eat the organic matter, but decomposers secrete enzymes to digest organic matter and then absorb the ensuing molecules
The decomposers are a special subset of detritivores that: break the organic compounds in inorganic form and then
The decomposers are a special subset of detritivores that: break the organic compounds in inorganic form and then absorb whatever they need for nutrition
Consumers Vultures Four types Herbivore: eats only plants E.g. Cows, horses Carnivore: eats only meat E.g. Polar bear Omnivore: eats plants and animals E.g. Humans, bears Scavenger: carnivore that feeds on bodies of dead organisms E.g. Vultures
Food Chains & Food Webs
A Food Chain is the:energy flow from one trophic level to the other One organism at each trophic level.
What does an arrow show?The direction of the energy transfer, NOT “what ate what”Rose Aphid Ladybird
A Trophic Level describes the position of the organism in relation to how it gets nutrients & energy The main trophic levels are: Primary producers Consumers Decomposers
The Main Trophic Levels are:Primary producers:Photosynthesisers - are autotrophs: get their energy directly from sunlightConsumers & Decomposers are:Heterotrophs:consume, directly or indirectly, the energy-rich molecules made by the primaryproducers
Organisms in one trophic level feed in the same way4th Trophic Level3rd Trophic Level2nd Trophic Level 1st Trophic Level Terrestrial food chain Aquatic food chain
Two Types of Food Chain: Detritus food chainsGrazing food chains Leaf litter
Two Types of Food Chain:1. grazing food chains grass rabbit fox eagle2. detritus food chains leaf litter earthworm blackbird dead animal blowfly maggots frog (detritus detritivore carnivore) blowfly maggot
What is a Food Web? When more than one organism is present at each trophic level
When compared to food chains, Food Webs are: reticulate more stable more resistant to disruptionIf all deer die ,do bears starve to death? NO!!
Note how: energy flows in ONE direction, but all the matter ends up in the detritivores & decomposers
Energy Losses in Ecosystem
How much of the solar energy falling on a leafis used for photosynthesis? only about 1% What happens to the rest of the solar energy falling on a green leaf?
The light energy which is not absorbed by aleaf is: Sunlight 100% Reflected 15% Evaporation 75% Transmitted 5% Can a plant absorb ALL wavelengths of light?
White Light NO. Certain wavelengths of light cannot be absorbed (e.g. green) Leaf Pigments Absorb Most Colors
Why do leaves look green?Green wavelength is reflected
Question:Give FOUR reasons why not all the light energyreaching a plant can be used for photosynthesis.1) Light is reflected away by the cuticle;2) Light may not be of the correct wavelength such as the green wavelength;3) Light is not trapped by chloroplasts but passes right through the leaf - transmitted;4) Light heats up water inside the leaf and makes it evaporate.
What is the photosynthetic efficiency? Sunlight1880 x 106 kJ m-2 yr -1 Reflected Evaporation Photosynthesis 24 x 106 kJ m-2 yr -1 1880 x 106 100% Transmitted 24 x 106 ? 24 x 106 x 100 = 1.3% 1880 x 106
Why does a food chain rarely have more than 7 trophic levels? Substantial losses in energy at every trophic level
What happens to the energy in the food once eaten?Which portion willbe available to thenext trophic level?
Energy Losses in Ecosystem Only about 10% of energy passes through each step of a food chain
Energy Losses in Ecosystem Only about 10% of energy passes through each step of a food chain 90% of energy is lost at each step
Energy Losses in Ecosystem If the pea plant contains 100 units of energy, how much energy would be present in the hawk? 100 10 1 0.1 0.01
Energy is lost at each trophic level.What could cause the energy to be lost? Heat Movement Waste e.g. faeces, urine Respiration Uneaten parts e.g. bones, fur, shells, wood
Why are energy losses greater in homeotherms(birds & mammals) than in poikilotherms (fish, reptiles)?Homeotherms use a great proportion of food eaten to keep a constantly warm body temperature.Heat Heat
Question:This cow has eaten 100 kJ of stored energy in the formof grass, and lost 63 kJ in the form of faeces, urine andgas. The energy stored in its body tissues is 4 kJ. Sohow much has been used up in respiration?The energy released by respiration:Eaten: 100Lost: 63Kept: 4100 – (63 + 4) = 33 kJ
Question:Only 4 kJ of the original energy available to thecow is available to the next stage, which mightbe humans.What is the efficiency of this energy transfer?Efficiency = 4⁄100 × 100 = 4%
Explain the following observation:Average efficiency of transfer from: plants to herbivores = 10% from animal to animal = 20% 10% 20% Herbivores are less efficient than carnivores as they eat grass having material which is not digestable (lignin & cellulose).
QuestionThe diagram shows the transfer of energy through acow. The figures are in kJ × 106 year–1.Key: A = energy absorbed from the gutC = energy consumed in foodF = energy lost in faecesP = energy used in production of new tissueR = energy lost by respirationU = energy lost in urine
a) (i) Complete the following equation for the energy used in the production of new tissue. Use only the letters C, F, R and U. (1) P = C – (U + F + R)
ii) Calculate the value of P. (2) P = C – (U + F + R) = 91.34 (0.03 + 57.06 + 30.51) = 91.34 – 87.6 = 3.74 kJ x 106 year -1
Productivity / Production refers to the rate of generation of biomass in an ecosystem per unit area per unit time unit is: joules/m2/year (energy) or g/m2/year (dry organic matter)
Two types of Productivity: Primary: Secondary: productivity of productivity of autotrophs (plants) heterotrophs (animals)Glucoseformed Food CO2 eaten O2 H2O
Primary Productivity is the rate at which energy is stored by primary producers in the form of organic substances which can be used as food materials
Gross Primary Production (GPP) is the rate at which plants store chemical energy and is entirely available for growth
Net Primary Production (NPP) is the energy potentially available to the next trophic level NPP = GPP - R Glucose produced during photosynthesis (Gross Primary Production) Remaining glucose Some glucose used to available to be laid down supply energy to drive as new material - biomass cellular processes (Net Primary Production) (Respiration)
Net Primary Productivity NPP = GPP - Respirationplant≈50% of GPP is used for respiration
Which refers to(i)NPP and (ii) GPP?
GPPWhich refers to NPP(i)NPP and (ii) GPP?
Biomass / Standing Crop the amount of dry organic matter per unit area present at a given time Unit of biomass: g/m2 OR the amount of stored food energy per unit area present at a given time Unit of biomass: J/m2
Does Productivity mean the same as Biomass?No.Productivity is the RATE at which organic matterforms.There is no element of time involved in thedefinition of biomass. Give a reason why an ecosystem can be highly productive but has a low biomass.
It is rapidly grazed
It is rapidly grazed
Secondary Production: The conversion ofassimilated energy into new tissue Energy assimilated = Food eaten – Faeces Total energy taken in (food eaten) Waste (faeces)
How much energy is available to the next trophiclevel?
REMEMBER: Respiration, mai ntenance Gross primaryproduction (GPP) Net primary production (NPP)
Components of energy transfer betweentrophic levels Energy from lower trophic level Energy not used Gross energy intake Egested energy Digested energy Urinary waste Assimilated energy Resting energy Activity Growth Reproduction Maintenance or Production respiration
What is the correlation in each case? Positive correlation
Coral Reef: High productivity
Factors that influence Primary Productivityinclude: Temperature Intensity of sunlight (which varies seasonally)
Generalisations about Community Productivity The tropics have among the most productive systems, in part because incident solar radiation is greater toward the equator. The most productive temperate systems are marshes. Nutrients are continually brought in and wastes are flushed out as water moves through them. Deserts and oceans are among the least productive systems. Little water in deserts and few nutrients in open oceans are responsible. Thus, 80% of the Earth’s surface is covered by the least productive systems.
Energy Flow Through A Grazing Food Chain
Energy Flow Through A Grazing Food Chain
WORKED OUT PROBLEM: FLOW OF ENERGY (kJ/m2/yr) IN A GRASSLAND
1) Find the gross primary production of grasses and herbs. 36x105 + 20.4x106 = 24x106 kJ/m2/yr
2) Find the photosynthetic efficiency (i.e. efficiency of conversion of incident solar energy to gross primary production. 1880x106 100% 24x106__ x 100 = 1.3% 24x10 6 ? 1880x106
3) What is the net production of seed-eating birds, spiders and grasshoppers respectively? i) Birds: 60x103 – 59.2x103 = 800 kJ/m2/yr
3) What is the net production of seed-eating birds, spiders and grasshoppers respectively? ii) Spiders: 700 – 500 = 200 kJ/m2/yr
3) What is the net production of seed-eating birds, spiders and grasshoppers respectively? iii) Grasshoppers: 444x103 - 374.3x103 = 69700 kJ/m2/yr
What are ‘Ecological Pyramids’? diagrammatic representations of feeding relationships and energy transfer through the biotic component of ecosystems
Three types of Ecological Pyramids:1. Numbers2. Biomass3. Energy Secondary consumers Primary consumers Producers
Pyramid of Numbers: Nos. at each trophic level Tertiary Consumer 4th Trophic 1 eagle Level Secondary Consumer 3rd Trophic 8 frogs Level Primary Consumer 29 grasshoppers 2nd Trophic Level Producers 1500 blades 1st Trophic of grass Level
What happens to the population size on moving upthe pyramid? Decreases Tertiary Consumer 4th Trophic 1 eagle Level Secondary Consumer 3rd Trophic 8 frogs Level Primary Consumer 29 grasshoppers 2nd Trophic Level Producers 1500 blades 1st Trophic of grass Level
Pyramid of Numbers may be inverted: Typical Inverted Inverted pyramid with pyramid with pyramid with a carnivore a LARGE PARASITES producer
How would you collect data to draw a pyramid of fresh biomassfor a field ecosystem? Place a quadrat at random. Collect all organisms enclosed. Separate into various trophic levels: producers, herbivores & carnivores. Weigh organisms at each trophic level. Calculate biomass in g m-2 Repeat to get an average. Draw a pyramid to scale.
How would you know to which trophic level anorganism belongs? Observe an animal while it feeds. Inspect mouthparts. Dissect ONE animal and observe gut contents.
How is a pyramid drawn to scale? Organisms Fresh biomass / g Green plants 2250 Herbivores 240 Divide each Carnivores 38 number by the smallest value. Green plants: 2250/38 = 59 boxes Herbivores: 240/38 = 6 boxes Carnivores: 38/38 = 1 box
Pyramid of Biomass Why is the pyramid inverted in autumn?Low food production by producers & a lot of grazers
Draw a pyramid of numbers & of biomass for thisfood chain:Pyramid of Numbers Pyramid of Biomass Ladybird Aphid Rosebush Rosebush Aphid Ladybird
90% Loss in energy at EACH trophic level Pyramid of Energy kJ/m2/day
Why does biomass decrease up a food chain? As energy is consumed by the organisms ateach trophic level, less energy is available toorganisms further along the food chain which thus supports a smaller biomass
Pyramid of Energy: is the ideal way of representing relationships between individuals because:- 1. it takes into account the rate of production (flow of energy in a specific time) Energy Flow Biomass kJ/m2/day grams/m2 Forest
Pyramid of Energy: is the ideal way of representing relationships between individuals because:- 2. Comparison based on biomass may be misleading because weight for weight two species may not have the same energy content
Pyramid of Energy: is the ideal way of representing relationships between individuals because:- 3. inverted pyramids are not obtained
Pyramid of Energy:Different ecosystems can be compared and the relative importance of populations within one ecosystem can be comparedFor example, the great importance of soil bacteria in terms of energy flow is not obvious from their small biomass Density Biomass Energy flow (No./m2) (g/m2) (kJ/m2/day) Soil 1012 0.001 4.2 bacteria Marine 200 10.0 4.2 snails
Pyramid of Energy: is the ideal way of representing relationships between individuals because:- 4. input of solar energy can be added as an extra rectangle at the base of the pyramid
Criticisms of ecological pyramids1. It is difficult to allocate a trophic level to many carnivores and omnivores which eat a varied diet.2. Another major problem is where to place dead and waste material. Way to show decaying material in a pyramid of biomass or energy.