1. Communities in Motion A biological community is an assemblage of populations of various species living close enough for potential interaction  For example, the “carrier crab” carries a sea urchin on its back for protection against predators © 2011 Pearson Education, Inc.

2. Community interactions are classified by whether they help, harm, or have no effect on the species involved Ecologists call relationships between species in a community interspecific interactions Examples are competition, predation, herbivory, symbiosis (parasitism, mutualism, and commensalism) Interspecific interactions can affect the survival and reproduction of each species, and the effects can be summarized as positive (+), negative (–), or no effect (0) © 2011 Pearson Education, Inc.

3. Competition Interspecific competition (–/– interaction) occurs when species compete for a resource in short supply © 2011 Pearson Education, Inc. Competitive Exclusion Strong competition can lead to competitive exclusion, local elimination of a competing species The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place

4. Ecological Niches and Natural Selection Ecological niche  can also be thought of as an organism’s ecological role (it’s use of biotic and abiotic factors) Ecologically similar species can coexist in a community if there are one or more significant differences in their niches; however, TWO SPECIES CANNOT OCCUPY THE EXACT SAME NICHE! (One will be excluded through competition.) © 2011 Pearson Education, Inc. Resource partitioning of a niche enables similar species to coexist in a community

5. Figure 54.2 A. distichus perches on fence posts and other sunny surfaces. A. insolitus usually perches on shady branches. A. ricordii A. aliniger A. insolitus A. distichus A. christophei A. cybotes A. etheridgei

6. Predation Predation (+/– interaction) refers to interaction where one species, the predator, kills and eats the other, the prey Some feeding adaptations of predators are claws, teeth, fangs, stingers, and poison Prey display various defensive adaptations: include hiding, fleeing, forming herds or schools, self-defense, and alarm calls

7. Animals also have morphological and physiological defense adaptations Cryptic coloration, or camouflage, makes prey difficult to spot © 2011 Pearson Education, Inc. http://www.youtube.com/watch?v=PmDTtkZlMwM Animals with effective chemical defense often exhibit bright warning coloration, called aposematic coloration Predators are particularly cautious in dealing with prey that display such coloration

9. In some cases, a prey species may gain significant protection by mimicking the appearance of another species In Batesian mimicry, a palatable or harmless species mimics an unpalatable or harmful model © 2011 Pearson Education, Inc. In Müllerian mimicry, two or more unpalatable species resemble each other

11. Symbiosis Symbiosis is a relationship where two or more species live in direct and intimate contact with one another - Parasitism In parasitism (+/– interaction), one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process Parasites that live within the body of their host are called endoparasites (worms), or on the external surface of a host are ectoparasites (ticks)

12. Mutualism Mutualistic symbiosis, or mutualism (+/+ interaction), is an interspecific interaction that benefits both species A mutualism can be –Obligate, where one species cannot survive without the other –Facultative, where both species can survive alone © 2011 Pearson Education, Inc.

13. Figure 54.7 (a) Acacia tree and ants (genus Pseudomyrmex) (b) Area cleared by ants at the base of an acacia tree

14. Commensalism In commensalism (+/0 interaction), one species benefits and the other is neither harmed nor helped Commensal interactions are hard to document in nature because any close association likely affects both species © 2011 Pearson Education, Inc.

15. An ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interact Regardless of an ecosystem’s size, its dynamics involve two main processes: energy flow and chemical cycling Remember: Energy flows through an ecosystem…while matter is recycled! Physical laws govern energy flow and chemical cycling in ecosystems

16. Trophic structure is the feeding relationships between organisms in a community Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores) Trophic level refers to where a species falls in the food chain Food chains link trophic levels from producers to top carnivores

17. Energy, Mass, and Trophic Levels Heterotrophs depend on the biosynthetic output of other organisms © 2011 Pearson Education, Inc. Every food web must contain a PRIMARY PRODUCER! It is responsible for making all of the organic materials that will be passed along the food chain. Primary producers “capture” all the ENERGY the ecosystem will have! Primary production is the amount of light energy converted to chemical energy by autotrophs during a given time period  The extent of photosynthetic production sets the spending limit for an ecosystem’s “energy budget”

18. Key Chemical cycling Energy flow Sun Heat Primary producers Primary consumers Secondary and tertiary consumers Detritus Microorganisms and other detritivores Figure 55.4

19. Tropical rain forests, estuaries, and coral reefs are among the most productive ecosystems per unit area Marine ecosystems are relatively unproductive per unit area, but contribute much to global net primary production because of their volume

20. Energy transfer between trophic levels is typically only 10% efficient © 2011 Pearson Education, Inc. The other 90%: gets used by the organism for cellular process & growth some is lost as heat some eliminated as waste

21. © 2011 Pearson Education, Inc. In a biomass pyramid, each tier represents the dry weight of all organisms in one trophic level Most biomass pyramids show a sharp decrease at successively higher trophic levels

22. Trophic Efficiency and Ecological Pyramids Trophic efficiency is the percentage of production transferred from one trophic level to the next It is usually about 10%, (with a range of 5% to 20%) © 2011 Pearson Education, Inc. Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer *Food chains rarely go beyond quaternary consumers because there simply isn’t enough energy left to sustain that level of consumer.

23. Food Webs A food web is a branching food chain with complex trophic interactions Species may play a role at more than one trophic level

24. Be able to identify the primary producers, primary consumers (herbivores), etc… How would a decomposer fit into a food web?

25. Detritivores, or decomposers, are consumers that derive their energy from detritus, nonliving organic matter Prokaryotes and fungi are important detritivores Decomposition connects all trophic levels © 2011 Pearson Education, Inc.

26. Species with a Large Impact Certain species have a very large impact on community structure Such species are highly abundant (Dominant species) or play a pivotal role in community dynamics (Keystone species) © 2011 Pearson Education, Inc.

27. Dominant Species © 2011 Pearson Education, Inc. Dominant species are those that are most abundant or have the highest biomass Dominant species exert powerful control over the occurrence and distribution of other species –For example, sugar maples have a major impact on shading and soil nutrient availability in eastern North America; this affects the distribution of other plant species

28. Keystone Species Keystone species exert strong control on a community by their ecological roles, or niches In contrast to dominant species, they are not necessarily abundant in a community Keystone predators usually increase diversity in a community by holding down prey populations. © 2011 Pearson Education, Inc. For example: It could be a small predator that keeps down a population of herbivores and prevents them from wiping out a plant species. They're effective especially when the other animal has no other predators.

29. Figure 54.17 EXPERIMENT RESULTS With Pisaster (control) Without Pisaster (experimental) Year ’73’72’71’70’69’68’67’66’65’641963 0 5 10 15 20 Number of species present

30. Ecological Succession Ecological succession is the sequence of community and ecosystem changes after a disturbance Primary succession occurs where no soil exists when succession begins. Retreating glaciers provide a valuable field-research opportunity for observing primary succession. Secondary succession begins in an area where soil remains after a disturbance © 2011 Pearson Education, Inc. Early arrival species may facilitate appearance of later species by making the environment favorable

31. © 2011 Pearson Education, Inc. The first stage of succession is called the “pioneer” stage. Succession is the result of changes induced by the vegetation itself A CLIMAX COMMUNITY is a mature, stable community that is the final stage of ecological succession

32. Biological and geochemical processes cycle nutrients and water in ecosystems Life depends on recycling chemical elements Nutrient circuits in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles © 2011 Pearson Education, Inc. A model of nutrient cycling includes main reservoirs of elements and processes that transfer elements between reservoirs All elements cycle between organic and inorganic reservoirs

33. Biogeochemical Cycles Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally Less mobile elements include phosphorus, potassium, and calcium © 2011 Pearson Education, Inc. In terrestrial ecosystems, nitrogen is the most common limiting nutrient.

34. Water is essential to all organisms Liquid water is the primary physical phase in which water is used The oceans contain 97% of the biosphere’s water; 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater © 2011 Pearson Education, Inc.

35. Movement over land by wind Precipitation over land Precipitation over ocean Evaporation from ocean Evapotranspira- tion from land Runoff and groundwater Percolation through soil Figure 55.14a The Water Cycle

36. The Carbon Cycle Carbon-based organic molecules are essential to all organisms Photosynthetic organisms convert CO 2 to organic molecules that are used by heterotrophs Carbon reservoirs include fossil fuels, soils and sediments, plant and animal biomass, the atmosphere, and sedimentary rocks © 2011 Pearson Education, Inc. CO 2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO 2 to the atmosphere

37. CO 2 in atmosphere Photo- synthesis Burning of fossil fuels and wood Phyto- plankton Photosynthesis Cellular respiration Consumers Decomposition

38. The Nitrogen Cycle Nitrogen is a component of amino acids, proteins, and nucleic acids The main reservoir of nitrogen is the atmosphere (N 2 ), though this nitrogen must be converted to other usable forms for the plant  this is done through nitrogen fixation by bacteria © 2011 Pearson Education, Inc.

39. Terrestrial cycling Decom- position Denitri- fication NO 3 – NO 2 – N2N2 Assimilation Fixation in root nodules AmmonificationNitrification NH 4 + NH 3 Uptake of amino acids

40. Decomposition and Nutrient Cycling Rates Decomposers (detritivores) play a key role in the general pattern of chemical cycling Rates at which nutrients cycle in different ecosystems vary greatly, mostly as a result of differing rates of decomposition The rate of decomposition is controlled by temperature, moisture, and nutrient availability © 2011 Pearson Education, Inc.