Introduction interspecific interactions

Transcription

1 Introduction There are different interspecific interactions, relationships between the species of a community (what s the definition of a community again?). Here s one. And how evolution works. While you re at it, what s the definition of interspecific? How about a POGIL?

2 1. Populations may be linked by competition, predation, mutualism and commensalism. Possible interspecific interactions are introduced in Table 53.1, and are symbolized by the positive or negative affect of the interaction on the individual populations. Note the comparison with symbiotic relationships. Are these all symbiosis?

3 Competition. Interspecific competition for resources can occur when resources are in short supply. There is potential for competition between any two species that need the same limited resource. The competitive exclusion principle: two species with similar needs for the same limiting resources cannot coexist in the same place.

4 The ecological niche is the sum total of an organism s use of abiotic/biotic resources in the environment. The competitive exclusion principle can be restated to say that two species cannot coexist in a community if their niches are identical. This is the this town s not big enough for the both of us principle. What are some possible outcomes of this competition?

5 Classic experiments confirm this principle. Which one out-competes the other? Fig. 53.2

6 Resource partitioning is the differentiation of niches that enables two similar species to coexist in a community. Fig Fig. 53.2

7 Predation. A predator eats prey. Herbivory, in which animals eat plants. In parasitism, predators live on/in a host and depend on the host for nutrition. Symbiosis? Watch this wasp and his cockroach host! Predator adaptations: many important feeding adaptations of predators are both obvious and familiar. Claws, teeth, fangs, poison, heat-sensing organs, speed, and agility.

8 Plant defenses against herbivores include chemical compounds that are toxic. Animal defenses against predators. Behavioral defenses include fleeing, hiding, selfdefense, noises, and mobbing. Camouflage includes cryptic coloration, deceptive markings. Fig. 53.5

9 Mechanical defenses include spines. Chemical defenses include odors and toxins Aposematic coloration is indicated by warning colors, and is sometimes associated with other defenses (toxins). Fig. 53.6

10 Mimicry is when organisms resemble other species. Batesian mimicry is where a harmless species mimics a harmful one. Fig. 53.7

11 Müllerian mimicry is where two or more unpalatable species resemble each other, like this bee and its wasp mimic. Fig. 53.8

12 Mutualism is where two species benefit from their interaction. Commensalism is where one species benefits from the interaction, but other is not affected. An example would be barnacles that attach to a whale. How about this one? Fig. 53.9

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14 Here s a really neat look at termites! eu 7 minutes

15 Coevolution and interspecific interactions. Coevolution refers to reciprocal evolutionary adaptations of two interacting species. When one species evolves, it exerts selective pressure on the other to evolve to continue the interaction. For example, adaptations for speed in both cheetahs and antelopes. Look at these. Flowers and their pollinators are classic examples.

16 SC.912.L.17.9 Use a food web to identify and distinguish producers, consumers, and decomposers. Explain the pathway of energy transfer through trophic levels and the reduction of available energy at successive energy levels.

17 4. Design an ecosystem that displays the interdependence of producers, consumers and decomposers. Develop a path of the energy that follows through each of the trophic levels within your ecosystem and relate the cause and effect of changes in predator and prey 3. Use a food web to identify and distinguish producers, consumers, and decomposes Explain the pathway of energy transfer through trophic levels and the reduction of available energy at successive trophic levels

18 2. Trophic structure is a key factor in community dynamics The trophic structure of a community is determined by the feeding relationships between organisms. The transfer of food energy from its source in photosynthetic organisms through herbivores and carnivores is called the food chain.

19 Charles Elton first pointed out that the length of a food chain is usually four or five links, called trophic levels. He also recognized that food chains are not isolated units but are hooked together into food webs. Fig

20 Marine Ecosystem: can you draw a food web?

21 Food webs. Who eats whom in a community? Which ones are the producers here? What transforms food chains into food webs? Which ones feed on only one other type? Fig

22 3. Dominant species and keystone species exert strong controls on community structure Dominant species are those in a community that have the highest abundance or highest biomass (the sum weight of all individuals in a population). If we remove a dominant species from a community, it can change the entire community structure.

23 Keystone species exert an important regulating effect on other species in a community. Fig

24 The Pisaster experiments done by Robert Paine in Washington and elsewhere Demonstrated that some species that were not dominant in terms of biomass or numbers exert a high amount of control on the community they are a part of. Often at the top of the food chain, can you see how these keystone species are part of a feedback system much like we have seen with blood sugar and lactose and other chemicals, just on a larger scale? Here s his story. 20 min. Regulatory systems evolve naturally to result in the homeostatic balances you see in nature.

25 If they are removed, community structure is greatly affected. See this classic story of wolves in Yellowstone. Fig

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27 1. Biological and geologic processes move nutrients between organic and inorganic compartments. Let s follow chemicals A general model of chemical cycling. There are four main reservoirs of elements and processes that transfer elements between reservoirs. Reservoirs are defined by two characteristics, whether it contains organic or inorganic materials, and whether or not the materials are directly usable by organisms.

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29 The carbon cycle fits the generalized scheme of biogeochemical cycles better than water. Fig

30 The water cycle is mostly a physical process (evaporation, condensation), but part is biological, right? Fig

31 Did you get it right? Respiration and dehydration synthesis creates new water, and photosynthesis and hydrolysis breaks water molecules apart.

32 The nitrogen cycle. You DON T need to know this for the EOC, but let s take a look. Nitrogen enters ecosystems through two natural pathways. Atmospheric deposition, where usable nitrogen is added to the soil by rain or dust. Nitrogen fixation, where certain prokaryotes convert N 2 to forms that can be used to synthesize nitrogenous organic compounds like amino acids.

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34 Recent studies indicate that human activities have approximately doubled the worldwide supply of fixed nitrogen, due to the use of fertilizers, cultivation of legumes, and burning. This may increase the amount of nitrogen oxides in the atmosphere and contribute to atmospheric warming, depletion of ozone and possibly acid rain.

35 This may cause big problems in the future with the balance of this cycle, just as human burning of fossil fuels is causing problems related to the carbon cycle. Two more examples of human activity affecting the ecosystem in negative ways.

36 Review and connect Disturbances to food webs obviously are changing population sizes. What kind of limiting factor are the killer whales? Now let s look at another phenomenon that involves changes in population size succession. How about a POGIL?

37 3. Ecological succession is the sequence of community changes after a disturbance Ecological succession is the transition in species composition over ecological time. Primary succession begins in a lifeless area where soil has not yet formed. Like after a volcano, on volcanic islands like Hawaii and the Galapagos. Secondary succession occurs when most if not all life is extinguished, but soil remains.

38 In primary succession, mosses and lichens colonize first and cause the development of soil. These are Pioneer communities. An example would be when a glacier has retreated.

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40 Secondary succession occurs where an existing community has been cleared by some event, such as fire or clear-cutting, but the soil is left intact. Grasses grow first, then trees and other organisms. Climax communities?

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42 A marine food web is shown below. Which of the following would be a long-term effect of removing baleen whales from the ecosystem represented by this food web? A. The krill population would increase B. The orca population would increase C. The phytoplankton population would increase D. The large fish and squid population would increase

43 An arctic food web is shown below. Suppose that the lemming population is removed from this food web. Which of the following will be a short-term effect of this change? A. The arctic fox population will increase B. The polar bear population will increase C. the caribou population will decrease D. The snowy owl population will decrease

44 Part of an ocean food web is shown below. Which of the organisms in the web are secondary consumers? A. blue sprat and mackerel B. mackerel, tuna, and shark C. blue sprat and zooplankton D. blue sprat, mackerel, tuna, and shark

45 A meadow food web is shown below. Which organisms are in the trophic levels that sustains this ecosystem?