Ecology

I.Ecology of Ecosystems and

Communities

A. Interdependence of Ecosystems

Ecosystems depend on each other for survival (no defined boundaries)Depend on abiotic factors of other ecosystems (temp., wind, sunlight,etc.)Ex: rainforests produce lots of oxygen, wind can carry to other areas to support more consumers.

The size of an ecosystem can vary. It may be a whole forest or a small pond. Ecosystems areoften separated by geographical barriers, like deserts, mountains, or oceans, or are isolatedsuch as lakes or rivers. These borders are never rigid, though, so ecosystems tend to blendinto each other. As a result, the whole earth can be seen as a single ecosystem, or anindividual lake can be divided into several ecosystems, depending on the scale used.

B. Energy Flow in Ecosystems

1. Energy cannot be created or destroyed, but can be transferred to other forms (light energy to heat, electrical, or chemical energy).

2. Most energy in a system is given off as heat (metabolism).

3. Flow of energy:a) light is the initial source for whole

ecosystemb) autotrophs produce organic matter with

this energy through photosynthesisc) heterotrophs consume macromolecules

organic matter through other organisms

Types of heterotrophs:i) consumers feed on other living things

-primary (herbivores)-secondary (carnivore)-tertiary (secondary carnivore)

ii) detritivores feed on dead organic matter by ingesting it (earthworms)

iii) saprotrophs secrete enzymes and ingest broken down products (certain mushrooms)note: detritivores and saprotrophs are not

considered to be part of the energy foodchain, but are involved in recycling nutrients for an ecosystem

Examples of Food ChainsLabel Produce

rPrimary consumer

Secondary consumer

Tertiary consumer

Quaternary consumer

Trophic Level

1 2 3 4 5

Aquatic Example

Elodea (aquatic plant)

Freshwater snail

Leech Stickleback fish

pike

Terrestrial Example

Carrot Plant

Carrot Fly

Fly Catcher Bird

Sparrow hawk

Goshawk

Terrestrial Example

Passion-flower

Heliconius butterfly

Tegu lizard

Jaguar

4. Energy Flow Diagramsa) Food webs (at least 10 organisms and 4 trophic levels)

i) no more than 5 levels supportedii) 10-20% efficiency between levels, rest lost as heat through cell respiration, metabolism, not

assimilated, waste.b) Energy pyramids show relative amount of energy lost at each trophic level (bottom level shows GP of ecosystem)

Gross Production= Net Production + Cellular Respiration (10% energy transferred at each level) -GP=total amount of organic matter

produced by plants-NP=amt. left after cellular

respiration -GP represents 1st trophic levelmeasured in KJ m-2year-1

Gross Production=10000kJ

1000kJ

100kJ

Example: Field in Michigan

Net Production =20.79 x 103 kJ m-2 year-1

Plant Respiration=3.68 x 103 kJ m-2 year-1

GP= 24.47 x 103 kJ m-2 year-1

(GP=NP + PR)

Biomass=organic matter-Loss of biomass accompanies loss of energy because organic matter consumed has mass!

-energy content per gram of food stays relatively constant

-total number of biomass available in higher trophic levels is small; low numbers of organisms at high trophic levels-not enough biomass to support

Assignment of Trophic Levels:

Sometimes difficult due to variety in diet of organisms, classified by main food source

Examples:Euglena-producer and consumer

Oyster-consumer, detritivore

5. Nutrient Flow in Ecosystems-energy can leave or enter an ecosystem, nutrients must be recycled (C, P, N2)

-done through biogeochemical cycles

a) Carbon Cycle

b) Nitrogen Cycle

c) Phosphorus Cycle

Carbon inAtmosphere

Carbon in The Earth

Carbon in living things

Components of the Nitrogen Cycle

Bacteria (chemoautotrophs)Nitrogen Fixation (converts atmospheric

nitrogen-N2 to ammonia-NH3)-Azotobacter (soil)-Rhizobium (found in root nodules of legumes)

Nitrification (changes NH3 to NO2- (nitrite) and

then to NO3- (nitrate))-Nitrosomonas (nitrification I to nitrite)-Nitrobacter (nitrification II to nitrate)

Denitrification (changes NO3- back to atmospheric

nitrogen-N2)-Pseudomonas denitrificans (anaerobic

conditions to use nitrate as an electron acceptor instead of oxygen)

Farmers/Gardeners-nitrogen fertilizers-plowing and digging-crop rotation (legumes increase nitrogen content)

II. Ecology of Species

A. Distribution of Plants-ranges of places it inhabits depending on abiotic factors (soil pH, temp., water, light, salinity, etc.)-Avicennia germinans is a Mexican swamptree that grows where soil is anaerobic and pH is neutral; thrives where most plants would not survive

B. Distribution of Animals1) Temperature (especially ectothermic)2) Water (required amount varies)3) Breeding sites (ex:mosquitos in stagnant water)4) Food supply (type of food needed must

be available)5) Territory (defended for feeding and

breeding)

c. The Niche Concept1) habitat, nutrition, relationships with

other organisms2) Competitive Exclusion Principle

D. Ecological Succession-changes to an ecosystem caused by interactions between living organisms and abiotic environment

-some species die, others join until stable=climax community (about 200 years)

-usually due to environmental catastrophe (volcanic eruption, forest fire, grass fire, etc.)

-glaciers are a good example(organic matter in soil increases, soil becomes deeper, increase in amt. of water retained, excess drainage, soil erosion, mineral recycling increases)

III. Population EcologyA. Studying Population Size

1.) natality, mortality, immigration, emigration2.) Population Curve (exponential, transitional, and plateau phases; carrying

capacity3.) Measurement of Population Size

a) random sampling- every individual has an equal chance of being selected

Types of Random Sampling

i) Quadrats• 1 sq. meter• good for organisms that don’t move• count species in quadrats all over, get mean

# plants per quadrat, estimate total area• formula:

population size = mean #per quadrat x total area

area of each quadratExample:data= 6,8,7,4,3,2 total area = 250 sq.meters

5(250)/1=1250 plants

ii) Capture-mark-release-recapture method• Good for animals that move around• Trap lots of animals in area, mark or tag carefully,

release, recapture• Count how many marked/unmarked• Use Lincoln Index to estimate population size

n1= total # organisms first caught and marked

n2= total # caught in second sample

n3= # marked in second sample

total population size = n1 x n2

n3

B. Using Statistics in Ecological Research

1.) Mean=sum of all values divided by the total number of values

2.) Standard Deviation =spread of values around the mean (measures how closely values are clustered toward the mean value)

Normal Distribution Curve

(Grades)

68% of data usually falls within +/- 1.00 standard deviation of the mean value

95% of data falls within +/- 2.00 standard deviations of the mean value

3.) The T-Test-Used to find if there is a significant difference between the mean values of two populationsa) The null hypothesis (Ho)=states that there is NO difference between the two populations and the difference in mean values is due to errors in sampling

b) Probability (p) = If the probability that a null hypothesis is correct is low (less than .05 or 5%), the null hypothesis is rejected and there is a significant difference between the two populations

c) Degrees of freedom =a method to estimate variability in a sample (for a t-test, df=(n1+n2)-2

Methods to analyze t-test results:a) Table of Critical Values (handout)- used to decide whether there is a significant difference between two populations. If the calculated t-value is less than the critical value found on the chart, there is no significant difference between the mean values and the null hypothesis is accepted. If calculated t-value is greater than the critical value, the difference is significant and the null is rejected.b) Analysis of p-value- computer program will tell you a p-value so you can decide if it is greater or less than .05 and whether or not the difference is significant.

4.) Simpson Diversity Index –measures “species richness” in an ecosystem through random samplinga.) instead of focusing on one particular organism, all organisms are accounted forb.) used to assess areas for wildlife conservation purposes (value can be from 1.0 to anything, but is most valuable when compared to other calculated indexesc.) Formula:

total # of organisms = N D= N(N-1)

number of species = ∑ n(n-1)diversity index = D

Ex: Collect 3 species with 40, 25, and 15 individualsD= (80 x 79)/(40 x 39) + (25 x 24) + (15 x 14) =

6320/2370=2.67

IV. EvolutionIV. Evolution--process of cumulative change in heritable process of cumulative change in heritable

characteristics of a populationcharacteristics of a population

Charles Darwin’s Observations and Charles Darwin’s Observations and DeductionsDeductions

A)A) Populations of organisms Populations of organisms increase exponentially but increase exponentially but stay the same overallstay the same overall

Environment cannot Environment cannot support so much, so support so much, so organisms will eventually organisms will eventually struggle for survivalstruggle for survival

B)B) Members of a species Members of a species have variation, some of have variation, some of which are favorable for which are favorable for their environmenttheir environment

Better adapted individuals Better adapted individuals tend to survive (natural tend to survive (natural selection)selection)

C)C) Variations and traits are Variations and traits are hereditaryhereditary

As generations follow, As generations follow, characteristics change and characteristics change and a species can evolvea species can evolve

Sexual Reproduction and EvolutionSexual Reproduction and Evolution MeiosisMeiosis-(crossing over, two sources of -(crossing over, two sources of

genes, new combinations of alleles)genes, new combinations of alleles)

FertilizationFertilization allows variation (change of allows variation (change of traits over time so species can survivetraits over time so species can survive

Asexual reproductionAsexual reproduction provides less provides less capacity for evolution (but can produce capacity for evolution (but can produce some mutations for variation)some mutations for variation)

Environmental Change and EvolutionEnvironmental Change and Evolutiona.) antibiotic resistancea.) antibiotic resistance

1) gene given to bacterium gives variation so 1) gene given to bacterium gives variation so some some are resistant and some are notare resistant and some are not

2) Natural selection favors resistant bacteria when 2) Natural selection favors resistant bacteria when antibiotics administeredantibiotics administered3) Non-resistant bacteria killed3) Non-resistant bacteria killed4) Resistant bacteria reproduce and spread 4) Resistant bacteria reproduce and spread

(mostly (mostly resistant)resistant)5) Doctors change to different antibiotic, same 5) Doctors change to different antibiotic, same

things things happen, happen, multiple resistancemultiple resistance evolves evolves

B.) Metal Tolerance in PlantsB.) Metal Tolerance in Plants

1.) Waste from mining, plants don’t grow well 1.) Waste from mining, plants don’t grow well (copper pollution)(copper pollution)

2.) Some plants do grow2.) Some plants do grow

3.) Growing plants are tested for copper 3.) Growing plants are tested for copper tolerance tolerance and compared to plants in a non-polluted and compared to plants in a non-polluted areaarea

4.) Plants in the polluted area more copper 4.) Plants in the polluted area more copper tolerant, offspring more copper tolerant than n tolerant, offspring more copper tolerant than n

non-non- polluted areapolluted area

5.) Pollen carrying copper tolerance genes can 5.) Pollen carrying copper tolerance genes can be be carried by wind to other areascarried by wind to other areas

v. Classificationvaluable for:

a) species identification (file already exists)b) predictive value (same groups)c) evolutionary links (common ancestors)

1.) Taxonomy-classification into groupsHuman Blue Whale Sequoia Plant

Kingdom Animalia Animalia PlantaePhylum Chordata Chordata ConiferophytaClass Mammaila Mammaila PinopsidaOrder Primates Cetacea

PinalesFamily Homonidae Balaenopteridae TaxodiaceaeGenus Homo Balenoptera SequoiaSpecies Homo sapiens Balenoptera Sequoia

musculussempervirens

2.) Binomial System-international genus (group of similar species) and species names (Ex: Homo sapiens)Rules: for naming species

a.) first name (genus name) is capitalizedb.) second name is lower casec.) both names underlined if handwritten,

italics if printed

3.) Generally 5 Kingdoms:Prokaryotes (bacteria), Protista (algae,

amoeba, paramecia), Fungi (molds and yeasts), Plantae, Animalia

4.) Dichotomous Keys

VI. Conservation of Biodiversity

A. Reasons for conservation1) Economic (medicines, new crops, etc.)2) Ecological (species interdependency, changes are damaging, etc.)3) Ethical (right to life, cultural

importance)4) Aesthetic (looks nice, inspiring)

B. Extinction of SpeciesExamples: passenger pigeon, dodo bird, Carolina parakeet, Sexton Mountain mariposa lily

C. Monitoring Environmental Change1) Living organisms can act as “indicator species”

Examples: -lichens (tolerance of SO2)-stonefly, mayfly, damselfly larvae

require unpolluted, well-oxygenated water-chironomid midge larvae, rat-tailed maggot larvae, tubifex worms show low oxygen levels (too much organic matter)

2) Abiotic factors (can be measured directly)

D. Nature ReservesManaged through…Restoration of degraded areasElimination of aggressive alien speciesSupplementary feeding and clearing of vegetation if necessaryControl of exploitation of animals and vegetation by humans

In situ conservation-conserving a species in its own habitat

Good if…Species remain adapted to habitatGreater genetic diversityNatural behavior patternsInteraction of species

Not so good if …Too few of species, unsafe in wildlifeDestruction of natural habitat could negatively affect species

Ex situ conservation- species are conserved outside of their environment

captive breeding-animals caught and moved to a zoo, returned to wildlife when numbers are considered high enough

Botanical gardens

Seed banks (endangered species can be kept in cold storage for up to 100yrs)

E. Conservation of FishOverexploitation of fish can…

Cause fish to fail in spawningCause fish to become extinctCause species dependent on fish to decrease in population

What is being done to control thisproblem?International measures (difficult to enforce):

Monitoring of populations, reproduction ratesQuotas for catches with low population stocksMoratoria for endangered speciesMinimum net sizesBans of drift nets

International Organizations for ConservationWWF-World Wildlife Fundmonitors endangered species, political lobbying, establishing nature reserves, 10,000 projects in conservation

CITES-Convention on International Trade in Endangered Species100 member states, regulates trade in threatened species (Appendix 1=banning of trade, Appendix 2= monitoring of trade with licensing) reviewed every 2yrs

VIII. Human ImpactLocal Impacts-(Introduction of alien species)

Rats in New ZealandSea Lampreys in Great LakesRats/Mongoose in Hawaii

Global ImpactsA.) Greenhouse Effect

Natural Process that is being compounded by humansGreenhouse gases-CO2, CH4, CFCs, H2O, SO2

Effects include global warming, rising sea levels, etc.Sources since 1880 have recorded increased levels of atmospheric CO2 (less photosynthesis from deforestation, increased amounts of fossil fuels)

B.) Ozone DepletionO3 absorbs short wave radiation (UV), reduces UV light to earth’s surfaceUV light

-damages DNA, increases mutation rates-increases skin cancer, cataracts, sunburn-reduces photosynthesis rates in plants/algae

Caused by CFCs (refrigerants, aerosol, plastics)-Chlorine is bad! UV breaks CFCs and Cl comes out to catalyze the reaction breaking O3 into O2 and O (hundreds of thousands of ozone molecules can be broken up by a single Cl atom)

CFCs have been reduced-by 2010, there should be a leveling off of ozone

C.) Acid RainCO2 dissolves in H2O in clouds to make carbonic acid (weak acid)SO2, NO cmpds have more drastic effect (ph=about 3) and are caused by human activities (vehicles, power stations, industry)Lakes rich in limestone can be buffered (CaCO3)Acidification of soil where K+, Ca2+ and Mg2+ are leached out making soil less fertileTrees have premature leaf fallAluminum becomes soluble in water and combines with acid anion. This compound runs into lakes, streams and is toxic to fish

D.) Eutrophication (increased level of mineral nutrients in water)Happens when raw sewage goes into rivers (bathing, drinking water pathogens become a problem as well)

Sewage(OrganicMatter)

Bacteria(consume and

Proliferate)

More Bacteria

(less O2, inc.In BOD)

Some Fish Killed Bacteria

Digest organic Matter to make

NH3, PO4-3

Nitrate

Eutrophication

Algal Bloom(Photosynthetic

Bacteria and algaeAbsorb nutrients)

PrimaryConsumers

Feed on algae

Release of O2Reoxygenated H2O

Recovery Of River

Nitrifyingbacteria

Nitrate Fertilizer in rivers can also cause eutrophication-algal blooms-too much algae so some die and sink to the bottom-bacteria decompose dead algae, increase BOD and deoxygenate water-low oxygen levels kill fish

E.) Biological FuelsBiomass can be used for fuel (wood, crop residues, dried manure, ethanol and methane)

Generation of Methane (renewable and non-polluting)Need methanogenic bacteria (anaerobic) to produce methane from CO2, H2, CH3COOH or a bioreactor that mimics this process (handout)Reactions:CO2 + 4H2 CH4 + 2H2O

CH3COOH CH4 + CO2

First groups of bacteria convert organic matter into acids and alcoholSecond groups of bacteria convert organic acids and alcohol to CO2, H2, and CH3COOHThird groups of bacteria are methanogens (Methanobacterium and Methanococcus)Leftovers are used for fertilizer