Chapter 37 Communities and Ecosystems

Transcription

1 Chapter 37 Communities and Ecosystems PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Lecture by Edward J. Zalisko Introduction Natural ecosystems are valuable because they provide, support outdoor recreation, and provide natural services including against hurricane damage, recycling, preventing erosion, and crops. Figure 37.0_2 1

2 COMMUNITY STRUCTURE AND DYNAMICS 37.1 A community includes all the organisms inhabiting a particular area Community ecology is concerned with factors that influence species and distribution of communities and affect community A community includes all the organisms inhabiting a particular area A biological is an assemblage of all the of organisms living close enough together for potential interaction and described by its species composition. The boundaries of a community vary with the research question to be. For example, the boundaries of a community could be defined as a or the intestinal of a pond organism. 2

3 37.2 Interspecific interactions are fundamental to community structure interactions are relationships with individuals of species in the community, greatly population structure and dynamics, and can be categorized according to their effect on the interacting populations Interspecific interactions are fundamental to community structure competition occurs when populations of two different species compete for the same limited resource. In, both populations benefit. In, one species (the predator) kills and eats another (the prey). In, an animal consumes plant parts or algae. In, the host plants or animals are victimized by parasites or pathogens. Table

4 37.3 Competition may occur when a shared resource is limited An is the sum of an organism s use of the biotic and abiotic resources in its environment. Interspecific competition occurs when the of two populations overlap. Competition lowers the of competing populations because the resources used by one population are not available to the other population. Figure 37.3A 37.4 Mutualism benefits both partners Reef-building corals and dinoflagellates illustrate the win/win nature of mutualism. Photosynthetic dinoflagellates gain shelter in the cells of each coral, produce sugars used by the polyps, and provide at least half of the used by the coral animals. Video: Clownfish and Anemone 4

5 Figure EVOLUTION CONNECTION: Predation leads to diverse adaptations in prey species Predation benefits the predator but kills the prey. Prey using protective strategies that include, mechanical, and chemical defenses. Video: Seahorse Camouflage Figure 37.5A 5

6 37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants Herbivores and plants undergo, a series of evolutionary adaptations in two species, in which change in one species acts as a new force on another EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants A plant whose body parts have been by an animal must expend energy to replace the loss. Thus, numerous defenses against have evolved in plants. Plant defenses against herbivores include and thorns and toxins. Figure 37.6 Eggs Sugar deposits 6

7 37.7 Parasites and pathogens can affect community composition A lives on or in a host from which it obtains nourishment. parasites include nematodes and tapeworms. External parasites include mosquitoes, ticks, and aphids. are disease-causing microscopic parasites that include, viruses,, or protists. Figure Parasites and pathogens can affect community composition pathogens can have rapid and dramatic impacts. The American chestnut was devastated by the chestnut blight. A fungus-like pathogen is currently causing sudden oak death on the West Coast. Non-native can cause a decline of the ecosystem. 7

8 37.8 Trophic structure is a key factor in community dynamics The of a community is a pattern of feeding relationships consisting of several different levels. The sequence of food transfer up the trophic levels is known as a. The transfer of food moves chemical and energy from producers up through the trophic levels in a community Trophic structure is a key factor in community dynamics are and support all other trophic levels. Consumers are heterotrophs. Herbivores are. typically eat herbivores. Tertiary typically eat secondary. typically eat tertiary Trophic structure is a key factor in community dynamics derive their energy from detritus, the dead material produced at all the trophic levels. are mainly and fungi and secrete enzymes that digest molecules in organic materials and convert them into inorganic forms, in the process called decomposition. Video: Shark Eating a Seal 8

9 Figure 37.8_s5 Trophic level Hawk Quaternary Killer whale Snake Tertiary Tuna Mouse Secondary Herring Grasshopper Primary Zooplankton Producers Plant Phytoplankton A terrestrial food chain An aquatic food chain 37.9 Food chains interconnect, forming food webs A is a network of interconnecting food chains. Notice that may eat more than one type of producer and several species of may feed on the same species of producer. Figure 37.9 Quaternary, tertiary, and secondary Tertiary and secondary Secondary and primary Primary Producers (plants) 9

10 Figure 37.9_1 Primary Producers (plants) Figure 37.9_2 Quaternary, tertiary, and secondary Tertiary and secondary Secondary and primary Primary Species diversity includes relative abundance and species richness is defined by two components: 1. Species richness, the of species in a community, and 2. Relative, the proportional representation of a species in a community. 10

11 37.10 Species diversity includes relative abundance and species richness species diversity in a community affects the species diversity of animals. Species diversity has consequences for. Low species diversity is characteristic of most modern ecosystems. Figure 37.10A Woodlot A Woodlot B Table

12 37.11 Keystone species have a disproportionate impact on diversity A species is a species whose impact on its community is larger than its biomass or abundance indicates and occupies a that holds the rest of its community in place. Examples of keystone species in marine ecosystems include Pisaster and long-spined sea urchins. Figure 37.11A Keystone Keystone absent Figure 37.11B 12

13 37.12 Disturbance is a prominent feature of most communities are events that biological communities and include, fires, floods, droughts, overgrazing, or activity. The types, frequency, and severity of disturbances vary from community to community Disturbance is a prominent feature of most communities Communities change following a severe disturbance that strips away and removes significant amounts of soil. results from colonization by a variety of species, which are replaced by a succession of other species Disturbance is a prominent feature of most communities succession begins in a virtually lifeless area with no soil. succession occurs when a disturbance destroys an existing community but leaves the soil intact. 13

14 Figure 37.12A Figure 37.12B Annual plants Perennial plants and grasses Shrubs Softwood trees such as pines Time Hardwood trees CONNECTION: Invasive species can devastate communities species are organisms that have been introduced into habitats by human actions and have established themselves at the expense of native communities. The absence of natural often allows rapid population growth of invasive species. 14

15 37.13 CONNECTION: Invasive species can devastate communities Examples of invasive species include the deliberate introduction of into Australia and into Australia. Figure 37.13B ECOSYSTEM STRUCTURE AND DYNAMICS 15

16 37.14 Ecosystem ecology emphasizes energy flow and chemical cycling An consists of all the organisms in a community and the abiotic environment with which the organisms interact. In an ecosystem, moves through the components of an ecosystem and is the transfer of materials within the ecosystem Ecosystem ecology emphasizes energy flow and chemical cycling A terrarium represents the components of an ecosystem and illustrates the fundamentals of flow. Figure Energy flow Light energy Chemical energy Heat energy Bacteria, protists, and fungi Chemical elements 16

17 37.15 Primary production sets the energy budget for ecosystems production is carried out by, is the amount of solar energy converted to chemical energy by an ecosystem s producers for a given area and during a given time period, and produces, the amount of living organic material in an ecosystem. Different ecosystems vary in their production and contribution to the total production of the biosphere. Figure Open ocean Estuary Algal beds and coral reefs Desert and semidesert scrub Tundra Temperate grassland Cultivated land Boreal forest (taiga) Savanna Temperate deciduous forest Tropical rain forest ,000 1,500 2,000 2,500 Average net primary productivity (g/m 2 /yr) Energy supply limits the length of food chains A caterpillar represents a consumer. Of the organic compounds a caterpillar ingests, about % is eliminated in feces, % is used in cellular respiration, and % is used for growth. 17

18 Figure 37.16A Plant material eaten by caterpillar 100 kilocalories (kcal) Feces 50 kcal 15 kcal 35 kcal Cellular respiration Growth Energy supply limits the length of food chains A of production shows the flow of energy from producers to primary and to higher trophic levels. Only about of the energy stored at each trophic level is available to the next level. Figure 37.16B Tertiary Secondary Primary 10 kcal 100 kcal 1,000 kcal Producers 10,000 kcal 1,000,000 kcal of sunlight 18

19 37.17 CONNECTION: A pyramid of production explains the ecological cost of meat When humans eat or fruit, we are primary, or other meat from herbivores, we are secondary, and fish like trout or salmon, we are or quaternary CONNECTION: A pyramid of production explains the ecological cost of meat Only about % of the chemical energy available in a trophic level is passed to the next higher trophic level. Therefore, the human population has about ten times more energy available to it when people eat instead of the meat of herbivores. Eating meat of any kind is expensive and environmentally. Figure Trophic level Secondary Meat-eaters Primary Vegetarians Cattle Producers Corn Corn 19

20 37.18 Chemicals are cycled between organic matter and abiotic reservoirs Ecosystems are supplied with a continual influx of energy from the and Earth s interior. Except for, there are no extraterrestrial sources of chemical elements. Thus, life also depends on the of chemicals Chemicals are cycled between organic matter and abiotic reservoirs cycles include components, abiotic components, and reservoirs, where a chemical accumulates or is stockpiled outside of living organisms. Biogeochemical cycles can be local or global. Figure Consumers 2 Producers 1 Nutrients available to producers Decomposers 4 Abiotic reservoirs Geologic processes 20

21 37.19 The carbon cycle depends on photosynthesis and respiration is the major ingredient of all organic molecules and found in the atmosphere, fuels, and dissolved in carbon compounds in the ocean. The return of CO 2 to the atmosphere by closely balances its removal by photosynthesis. The carbon cycle is affected by burning wood and fossil fuels. Figure Burning CO 2 in atmosphere 3 Cellular respiration Photosynthesis 1 Higher-level Plants, algae, cyanobacteria Wood and fossil fuels Primary 2 Decomposition Decomposers (soil microbes) 4 Wastes; death Detritus Plant litter; death The phosphorus cycle depends on the weathering of rock Organisms require for acids, phospholipids, and ATP. 21

22 37.20 The phosphorus cycle depends on the weathering of rock The cycle does not have an atmospheric component. are the only source of phosphorus for terrestrial ecosystems. Plants absorb phosphate ions in the soil and build them into organic compounds. Phosphates are returned to the soil by. Phosphate levels in aquatic ecosystems are typically low enough to be a limiting factor. Figure Uplifting of rock Weathering of rock Phosphates in rock Animals Runoff Plants 1 Assimilation 2 Phosphates Detritus Phosphates in soil in solution (inorganic) 5 3 Rock Precipitated (solid) phosphates 4 Decomposition Decomposers in soil The nitrogen cycle depends on bacteria is an ingredient of and nucleic acids, essential to the structure and functioning of all organisms, and a crucial and often limiting plant nutrient. Nitrogen has two abiotic reservoirs: 1. the atmosphere, of which about 80% is nitrogen gas, and

23 37.21 The nitrogen cycle depends on bacteria fixation converts N 2 to compounds of nitrogen that can be used by plants and is carried out by some. Figure Nitrogen (N 2 ) in atmosphere Plant Animal 6 Assimilation by plants 5 Denitrifiers 3 Nitrates in soil (NO 3 ) Nitrifying 4 bacteria 7 Detritus Decomposers 1 Nitrogen-fixing bacteria in root modules Free-living nitrogen-fixing bacteria Ammonium (NH 4 ) in soil CONNECTION: A rapid inflow of nutrients degrades aquatic ecosystems In ecosystems, primary production is limited by low nutrient levels of phosphorus and nitrogen. Over time, standing water ecosystems gradually nutrients from the decomposition of organic matter and fresh influx from the land, and primary production increases in a process known as eutrophication. 23

24 37.22 CONNECTION: A rapid inflow of nutrients degrades aquatic ecosystems of lakes, rivers, and coastal waters depletes oxygen levels and decreases species diversity. In many areas, phosphate pollution leading to eutrophication comes from agricultural fertilizers,, sewage treatment facilities, and runoff of animal waste from feedlots CONNECTION: A rapid inflow of nutrients degrades aquatic ecosystems of aquatic systems may also result from increased levels of nitrogen from feedlots and applications of large amounts of. Video: Cyanobacteria (Oscillatoria) Figure 37.22A 24

25 Figure 37.22B Winter Summer CONNECTION: Ecosystem services are essential to human well-being Although agricultural and other managed ecosystems are necessary to supply our needs, we also depend on services provided by natural ecosystems. Healthy ecosystems supply water and some foods, recycle, decompose wastes, and regulate and air quality CONNECTION: Ecosystem services are essential to human well-being Enormous increases in production have come at the expense of ecosystems and the services they provide. Human activities also many forest ecosystems and the services they provide. 25