Ecological Principles 100... · Web view1.word "ecology" coined from Greek word "oikos", which...

BIOL 100 – Human BiologyBasic Ecological Principles

I. IntroductionA. Definition of Ecology

1. word "ecology" coined from Greek word "oikos", which means "house" or "place to live"2. the study of the interaction of organisms with their environments3. involves understanding biotic and abiotic factors influencing the distributions and

abundance of living thingsa. biotic fatctors

1) dispersal (how species get distributed from one location to another)2) behavior3) interactions between species

a) competitionb) predator-preyc) symbiosis

b. abiotic factors1) temperature2) water availability3) light (intensity and spectral characteristics)4) salinity5) wind6) currents7) substrate

4. Ernst Haekel credited Charles Darwin as the “Father of Ecology”B. Scope of Ecology

1. population growth2. competition between species3. trophic relationships4. symbiotic relationships5. interaction with the physical environment6. species diversity7. ecosystem change (succession)6. human impacts on the environment

C. Some Important Terms1. population

a. a group of individuals, all belonging to the same species, living in a defined areab. gene flow occurs throughout the entire population

2. communitya. a group of interacting speciesb. concerned with feeding, competitive, and symbiotic relationships among these species

3. ecosystema. the interaction between the biological community and the physical environment

surrounding this communityb. concerned with how living things influence this environment and how the

environment influences these living thingsc. involves biogeochemical cycles

4. biospherea. all of the areas of the earth where living things existb. consists of all of the ecosystem of the earthc. note that the biosphere is primarily a closed system

1) energy fluxes through it2) materials are recycled

5. habitat (Fig. 23.1, p. 524)a. type of location where a species chooses to live

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Windward Community College BIOL 100 – Human Biology Dr. Dave Krupp

b. determined mainly by the physical, chemical and biological characteristics of theenvironment

6. geographic rangea. the geographic boundary beyond which a species does not occurb. a species’ habitats will occur within this range

II. Population GrowthA. Exponential Growth

1. hypothetical example of a single-celled organism that divides at a constant rate2. population growth rises exponentially with time3. determined by the biotic potential (see below)

Figure 1. Exponential population growth

B. Real Population Growth1. populations cannot increase exponentially indefinitely2. population growth is really the net outcome of the following processes: births, deaths,

immigrations, & emigrationsC. Characteristics of the Population Growth Curve

1. biotic potentiala. maximum rate of population growth under ideal conditionsb. determined by

1) number of offspring per individual2) time to reach reproductive maturity3) ratio males to females in a sexually reproducing species4) number of reproductive age members of the population

2. environmental resistance (Fig. 23.2, p. 525)a. limits species’ realization of its biotic potentialb. manifested by

1) decrease in birth rate2) increase in death rate3) resistance increases as population size increases due to density-dependent factors

3. carrying capacity, Ka. K = maximum sustainable population size in a given environmentb. also known as the equilibrium densityc. consequence of the fact that intensity of environmental resistance increases as the

population size increases

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d. if population size exceeds K, then population will decreasee. if population size < K, then population will increase

4. logistic growth to predict what populations will do in naturea. combining the effects of biotic potential and environmental resistanceb. biotic potential influences the steepness of the early part of the curvec. value for K determines when population size levels offd. consequences

1) when population size (N) small, growth is slow2) as size increases, growth rate increases3) as population size (N) approaches carrying capacity growth rate slows down due to

environmental resistance4) growth rate is 0 when population size is at the carrying capacity5) thus population size reaches an equilibrium state (constant size) once N = K

Figure 2. Logistic population growth taking into account the carrying capacity, K, as well as the bioticpotential.

5. real population growth is much more complex, consisting of fluctuations and change (Fig.23.2, p. 525)

D. Density-Dependent Factors Controlling Population Size ("self-regulating" populations")1. = factors that change in their ability to affect birth/mortality rates in response to the

population size or density2. usually operating with a significant effect when population size is near the carrying

capacity of the environment3. factors

a. limiting resources (e.g., food and shelter)b. production of toxic wastesc. infectious diseasesd. predatione. stressf. emigration

E. Density-Independent Factors1. = factors not related to population size2. may exert an effect upon any population size value3. examples include unpredictable catastrophic events

a. severe storms and floodingb. sudden unpredictable cold spellsc. earthquakes and volcanoes

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d. catastrophic meteorite impactsF. Human Population Growth (Fig. 23.14, p. 536)

1. throughout much of human history, population size has been low2. growth rate began increasing about 4000 years ago coincident with development of

agriculture and domestication of animals3. rapid exponential growth began coincident with the Industrial Revolution 300 years ago4. population doublings

a. was 1 billion in 1800b. was 2 billion in 1927c. was 4 billion in 1974d. is currently 7.3 billione. expect 8 billion by 2025

G. Population Age Structures (Fig. 23.15, p. 537)1. can illustrate population age structure as a pyramid (Fig. 3)

Figure 3. Population age structure2. shape of pyramid can indicate whether population is growing, stable, or declining

a. growing population with large numbers in younger age groups (Fig. 4)

Figure 4. Age structure of a growing populationb. declining population with smaller numbers in younger age groups (Fig. 5)

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Figure 5. Age structure of a decreasing populationIII. Interspecies Interactions

A. Competition Among Species (Interspecific Competition)1. Ecological Niche Concept

a. = the "role" a species "plays" in the ecosystemb. contrast with the "habitat"

2. Competitive Exclusion Principlea. "no two similar species occupy the same niche at the same time"b. possible outcomes of competition

1) extinction of one of the competing species2) resource partitioning

a) = "splitting" the niche, that is closely-related species avoiding competition byutilizing different parts of the niche

b) example: dividing up the forest canopy by different species of insectivorousbirds

3) character displacementa) co-existing species, that have very similar niches, evolve in such a way so as

to specialize on different aspects of the niche, thus avoiding competitionb) example seed-eating finch beak sizes on the Galapagos Islands

B. Predator-Prey Relationships1. expect predators to influence prey populations and visa versa2. possible outcomes of predator-prey relationships

a. oscillations in population sizesb. coevolution between predator and preyc. inducible defenses (defenses of prey brought on only by the presence of the predator)d. trophic cascade (web of indirect interactions precipitated by predation of one species

upon another)C. Keystone Species

1. definition: a species whose presence exerts a significant influence on the components ofthe biological community

2. examplesa. sea otters of California kelp bedsb. sea stars in the rock intertidal zone

D. Symbiosis1. condition in which two different species live in close association with one another

a. host, usually the larger of the two, may serve as the home for the other species (thesymbiont)

b. symbiont, usually the smaller of the two, often lives on or in the host2. types of symbiosis

a. mutualism (e.g., cleaning associations)b. commensalismc. parasitism

E. Biodiversity

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1. refers to the number of species (species richness)2. often regarded as a measure of ecosystem health3. factors influencing biodiversity

a. environmental (habitat) heterogeneityb. latitudec. environmental stability and disturbanced. human activities

4. also important to consider species evennessa. contrast communities in which one or a few species may dominate versus those in

which most species are equally represented by individualsb. many measures of species diversity take into account species evenness as well as the

total number of speciesIV. Ecological Succession

A. Basic Process1. process of how ecosystems change through time = ecological succession2. stages

a. bare substrateb. colonizing stagec. successionist staged. left undisturbed, the biological community will approach a climax stage (Fig. 23.4,

p. 527)B. Primary Versus Secondary Succession

1. primary successiona. involves starting off with a new substrateb. examples

1) new lava flows2) rock substrate left after glacier retreat

2. secondary successiona. severe disturbance cleared away existing community without wiping out existing

substrateb. examples

1) substrate left behind after a forest fire2) abandoned farmland

C. Successional Models and their Impacts (see Fig. 6)

Figure 6. Successional models and their impacts, example of coral reef ecosystems.

1. no disturbance (Competitive Exclusion Model): initially species diversity increases but thendecreases as competitive interactions eliminate lesser competitors

2. occasional strong disturbance (Intermediate Disturbance Model): occasional disturbances

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(e.g., major storms) prevent competitive exclusion from occurring3. constant disturbance (Colonial Model)

a. constant severe environment with only a few species capable of survivingb. potential competing species are rare

V. Energy and Materials Through EcosystemsA. Trophic Levels

1. 1st trophic level = primary producers, usually plants (Fig. 23.5, p. 528)2. 2nd trophic level = herbivores or primary consumers eat plants3. 3rd+ trophic levels = carnivores or secondary (or higher level) consumers eat other animals4. highest trophic level = top carnivore5. decomposers utilize nonliving organic matter

B. Simple Food Chain (Fig. 7)1. illustrates feeding relationships (i.e., the flow of energy and materials through the

community)2. example (note decomposers have not been included in this diagram)

Figure 7. A very simplified food chain

C. Food Webs (Fig. 23.7, p. 5301. many animals feed upon different trophic levels2. feeding relationships usually much more complex than simple good chain3. food webs more complicated in tropical ecosystems than in polar ecosystems4. complicated food webs usually more stable than simple ones

D. Primary Productivity1. definition

a. the rate of production of organic matter by autotrophic organisms (= primary producers)b. types of autotrophs

1) photosynthetica) use light energy in the conversion of inorganic carbon (i.e., carbon dioxide) into

organic carbon (i.e., carbohydrates; see Fig. 23.5, p. 528)b) examples include terrestrial plants, seaweeds, phytoplankton, and blue-green

algae2) chemosynthetic

a) use energy released by the catalysis of certain inorganic chemical reactions toconvert inorganic carbon into organic carbon

b) example: chemosynthetic bacteria from hydrothermal vents on the deep seafloor

c. primary productivity important because primary producers are the first link in the foodchain

2. factors influencing plant primary productivitya. light

1) light intensity2) spectral distribution

b. temperaturec. evapotranspirationd. availability of inorganic nutrients required for plants

3. photosynthesis vs. respirationa. photosynthesis (Fig. 23.5, p.528)

1) involves many steps with the following overall consequencesa) light energy (electromagnetic radiation) absorbed and converted to chemical

energy (= energy stored in chemical bonds between atoms of certainmolecules)

b) captured chemical energy used to synthesize carbohydrates (usually glucose)

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2) overall chemical reaction:

light energy + 6CO2 + 6H2O C6H12O6 + 6O2

3) carbohydrates produced may be used in the following waysa) sources of stored energy for energy-requiring processes of the plantb) building blocks for molecular components of cells and tissues for repair,

growth, and reproduction4) occurs in plants and certain photosynthetic bacteria

b. aerobic respiration1) involves the release of chemical energy stored in organic molecules (e.g., glucose)

for energy-requiring metabolic processes2) appears to be the opposite of photosynthesis (but is actually different)3) overall chemical reaction:

C6H12O6 + 6O2 6CO2 + 6H2O + chemical energy

4) occurs in nearly all cells (including plants) except certain anaerobic bacteria

4. Gross Primary Production Versus Net Primary Productiona. definitions

1) gross primary production (GPP) = the amount of light energy converted intochemical energy by photosynthesis

2) respiration (R) = consumption of chemical energy by primary producers3) net primary production (NPP) = chemical energy stored in primary producers after

respirationb. relationships among these parameters: NPP = GPP – R

5. ecosystem-by-ecosystem comparison of net primary productivity (Fig. 8)

Figure 8. Percent of global net primary productivity contributed by different ecosystems.

D. Energy Flow Through Ecosystems (Fig. 23.6, p. 529)

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1. energy enters ecosystem primarily as light (through plant photosynthesis)2. most of this energy leaves ecosystem as heat and is thus lost to space3. energy transfers from one trophic level to the next not very efficient4. fate of assimilated energy by each trophic level

a. heat lost due to metabolic activitiesb. death of whole organisms & parts of whole animals (this goes to the decomposers)c. consumption & assimilation by the next trophic level

Figure 9. The fate of energy through the ecosystem

E. Ecological Pyramids (Fig. 23.8, p. 531)1. usually more biomass in lower trophic levels than in higher trophic levels2. in addition, size of the individual organism generally increases as the trophic level

increasesF. Biogeochemical Cycles

1. while energy fluxes through ecosystems, materials are recycled2. these cycles regenerate inorganic nutrients so that plants may use them3. biogeochemical cycle examples

a. carbon cycle (see also Fig. 23.11, p. 533)

Figure 10. A simplified representation of the carbon cycle

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b. nitrogen cycle (see also Fig. 23.12, p. 534)

Figure11. A simplified representation of the nitrogen cycle

c. phosphorus cycle (see also Fig. 23.13, p. 535)4. importance of nutrients in water (aquatic ecosystems)

a. nutrient levels in aquatic ecosystems1) oligotrophic: nutrient-poor water2) eutrophic: nutrient-rich water

b. eutrophication (Fig. 24.7, p. 547; see also pp. 547-548)1) as nutrients are added, an oligotrophic condition becomes eutrophic2) manifested by a bloom in aquatic plants3) can be detrimental to aquatic ecosystems4) cultural versus natural eutrophication

a) natural eutrophication1) aquatic succession2) occurs over several hundreds of years

b) cultural eutrophication1) driven by human activities2) occurs rapidly3) consequences: heavy organic waste leading to depleted oxygen levels and

fish kills5. the water cycle (Fig. 23.10, p. 533)

a. involves evaporation and precipitation (e.g., rainfall)b. important to other biogeochemical cycles since minerals are dissolved into the water

6. generalized pattern for biogeochemical cycles

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Figure 12. Generalized representation of biogeochemical cycles in the ocean.

TEXT PAGES COVERED

521-538; 547-548

VOCABULARY

ecology oikos biotic factor abiotic factorpopulation community ecosystem biospherehabitat geographic range immigration emigrationbiotic potential environmental resistance carrying capacity (K) density dependent factordensity independent factor population age structure ecological niche competitive exclusionresource partitioning character displacement predator preycoevolution keystone species symbiosis hostsymbiont mutualism commensalism parasitismbiodiversity species richness species eveness ecological successionprimary succession secondary succession trophic level biomassherbivore carnivore consumer top carnivoredecomposer food chain food web ecological pyramidinorganic nutrient biogeochemical cycle carbon cycle nitrogen cyclephosphorus cycle water cycle eutrophication natural eutrophicationcultural eutrophication oligotrophic eutrophic light-dark bottleprimary productivity net primary productivity respiration gross primary productivityGPP NPP R

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STUDY QUESTIONS

1. Define the discipline called "ecology". What kinds of things to ecologists study?

2. Draw and label a diagram that illustrates the general pattern of logistic population growth over time. Be able to explain the different portions of the growth curve in terms of biotic potential and environmental resistance.

3. How are population sizes regulated? Be sure to describe both density-dependent and density-independent factors influencing population sizes.

4. Explain how population age structures may reveal about population growth. How do these patterns relate to industrialized versus non-industrialized nations?

5. What is meant by the Competitive Exclusion Principle? Be sure you define the term "niche" in your answer. How may two similar species evolve to minimize the impact of this principle?

6. Discuss short term and long term consequences of predator-prey relationships. Give real life examples to illustrate your discussion.

7. Compare and contrast, using examples, the three different kinds of symbiotic relationships.

8. Contrast photosynthesis with chemosynthesis. Give examples of organisms that carry out these processes.

9. Contrast gross primary productivity (GPP) with net primary productivity (NPP).

10. Discuss how primary productivity is measured using the light-dark bottle technique. What assumptions are made in using this technique?

11. Discuss the environmental factors that influence primary productivity.

12. Contrast the following geographic areas in terms of primary production per unit area, total primary production, and yield of food resources suitable for human consumption: open ocean, coastal regions, upwelling regions. Explain the differences observed.

13. Contrast food chains with food webs. Draw a labeled diagram that illustrates the characteristics of each.

14. Explain why the relative biomass of the various trophic levels of an ecosystem may be illustrated in the shape of a pyramid.

15. Contrast how energy and materials move through ecosystems. It would be useful to use labeled diagrams to illustrate your points.

16. Discuss, using written text supported with labeled diagrams, the carbon, nitrogen and water cycles.

17. What is eutrophication? Contrast natural and cultural eutrophication.

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