Chapter 16: Community Interactions

Transcription

1 Chapter 16: Community Interactions Lecture Outline Enger, E. D., Ross, F. C., & Bailey, D. B. (2012). Concepts in biology (14th ed.). New York: McGraw- Hill

2 The Nature of Communities A community consists of all of the populations of different species that interact in a particular location. Before an ecologist can study a community, he must first define the community boundaries. 16-2

3 Defining Community Boundaries The boundaries of an aquatic community are naturally defined by the water s edge. But does the community involve the plants and animals that live at the edge, or the predators that enter the area to eat and then leave? All community boundaries are artificial. Generated by ecologists for the purposes of studying the community s interactions 16-3

4 Complexity and Stability 16-4 The interactions between species in a community involve a number of food chains. These food chains interconnect as a food web. Even though the interactions are complex, community structure is relatively stable. Complexity and stability are directly correlated. More complex communities with more species that interact are more stable. Simpler communities that have been influenced by humans tend to be less stable.

5 A Food Web 16-5

6 Communities are Dynamic Saying that communities are stable does not imply that they do not change. On a large scale they are not changing, but individual organisms are constantly experiencing change. Individuals are producing, consuming, or decomposing. Populations are growing and shrinking. However, if one particular species increases or decreases significantly, the community as a whole will be affected. 16-6

7 Niche and Habitat Studying all of the species interactions in a community at one time is not possible. Ecologists often focus on the activities and impact of a few species. One element that ecologists focus on is the specific niche and habitat of individual species. 16-7

8 The Niche Concept 16-8 An organism s niche is its specific functional role in the community. Involves the organisms impact on the biotic and abiotic elements of the community Also involves how the abiotic and biotic elements in a community impact that organism The niche of an earthworm Affected by characteristics of the soil (abiotic) Affects soil composition by transporting minerals, air, and water to deeper regions Impacts biotic elements since it is food for a number of different species; serves as a host for various parasites

9 The Niche of an Earthworm 16-9

10 The Niche Concept Organisms with broader niches are more evolutionarily successful than organisms with more narrow niches. Opossum vs. koala Understanding the niche concept is important to understanding the impact of a new species on a community. Cows and dung beetles in Australia

11 The Habitat Concept The habitat of an organism is the place or community where it lives. Habitat is a part of their niche. Habitats are described in terms of features of an organism s home. Habitat examples Prairie dogs live in grasslands. Tuna live in the open ocean. Cacti live in the desert.

12 Kinds of Organism Interactions An important aspect of an organism s niche is how it interacts with other species in the community. Interactions between species occur when organisms share a common habitat. Some interactions are positive, some are negative and some are neutral

13 Competition Occurs when two organisms need a vital resource that is in short supply Can be food, water, shelter, nesting sites, mates, etc. Usually harms both organisms to some extent The most common interaction between species Intraspecific competition occurs between members of the same species. Pine seedlings competing for sunlight Interspecific competition occurs between members of different species. Cultivated plants and weeds competing for sunlight, water, space

14 Competition 16-14

15 Competition and Natural Selection In a competitive relationship, usually one of the two species wins the competition. The winner gains access to the limited resource. Competition is a force for natural selection. The more similar organisms are, the more intense the competition will be between them. The competitive exclusion principle states that no two species can occupy the same niche at the same time. If two organisms occupy the same niche, the competition will be so intense that One of the two species will become extinct. One of the two species will evolve to occupy a slightly different niche.

16 Examples of Competitive Exclusion Warblers Different species of warblers feed on similar organisms, but do so in different parts of trees. Different species of birds eat flying insects. Some feed at night, others feed at different altitudes. Birds are specialized by the size and kind of insect eaten

17 Niche Specialization 16-17

18 Predation Predation occurs when one organism is captured, killed, and eaten by another. The predator is the killer and the prey is killed. Predators are specially adapted to catch their prey. Predation strategies are widely varied. Chase and kill (leopards, lions, etc.) Camouflage, wait, and strike (frogs, lizards, etc.) Pounce and kill (spiders)

19 Predation Predators help control populations of potentially dangerous organisms. Populations of prey benefit from predation by Controlling population growth Predators also act as selecting agents by eliminating less well adapted individuals

20 The Predator-prey Relationship 16-20

21 Symbiotic Relationships Symbiosis means living together. Emphasized in interspecific relationships in which two species live in close physical relationship Not always positive for both species Include Parasitism Mutualism Commensalism 16-21

22 Parasitism Involves one organism living in or on another living organism in order to obtain nutrients The parasite benefits and the host is harmed. Parasites do not kill their host immediately because they need nutrients from it. However, as the parasite drains nutrients from the host, it is weakened and may die. Bacteria, viruses, protists, plants, fish, insects, worms, mites, and ticks are common parasites

23 Styles of Parasitism External parasites Live on the exterior of their hosts Fleas, ticks Internal parasites Live inside their hosts 16-23

24 Parasite Life Cycles Parasites have complicated life cycles. Many parasites experience different parts of their life cycles in different hosts. Some parasites use vectors, organisms that they infect simply to get to their necessary host. Ticks are vectors for the bacterium that causes Lyme s disease

25 Lyme Disease Hosts, Parasites and Vectors 16-25

26 Commensalism Commensalism is a relationship in which one organism benefits and the other is not affected. Sharks and remora Trees and epiphytic plants 16-26

27 Mutualism Mutualism is a relationship in which both species benefit. Usually involves a close physical association Bacteria in the guts of herbivores Lichens and corals Flowering plants and bees 16-27

28 Types of Communities The world can be subdivided into different types of communities called biomes. Biomes are particular communities or organisms that are adapted to a particular set of climate conditions. These conditions include Precipitation types and amounts Temperature ranges 16-28

29 The Influence of Precipitation and Temperature on Vegetation 16-29

30 Biomes of the World 16-30

31 Temperate Deciduous Forest Moderate rainfall spread over the entire year Relatively long summer growing season The dominant vegetation is deciduous forest. Deciduous trees lose their leaves in the fall. Adapted to significant precipitation and short, mild winters 16-31

32 Temperate Deciduous Forest Spreads from Mississippi River to Atlantic coast, from Florida to southern California; found in Europe and Asia Primary consumers in this community are leaf-eating insects, squirrels, deer Secondary consumers are birds Carnivores include foxes, hawks, and owls 16-32

33 Temperate Deciduous Forest 16-33

34 Temperate Grassland Also called a prairie Rainfall is not adequate to support the growth of trees. Long periods of time between rainfall Trees only exist near streams Dominant vegetation is grasses Interspersed with wildflowers 16-34

35 Temperate Grassland Primary consumers are large grazing mammals, small insects, and rodents Carnivores include meadowlarks, coyotes, and snakes. Birds are merely visitors. Fires are common during the dry season. Found between the Mississippi River and the Rocky Mountains Also in Eurasia, Africa, Australia, and South America 16-35

36 Temperate Grassland 16-36

37 Savanna Tropical biomes that have distinct wet and dry seasons Found in central Africa, northern Australia, South America Dominant vegetation is grasses Includes some drought-resistant trees Animals include grazing animals Antelope, wildebeest, zebras, kangaroos, capybara Termites are common 16-37

38 Savanna 16-38

39 Mediterranean Shrublands (chaparral) Located near an ocean Wet, cool winters and hot, dry summers Vegetation dominated by woody shrubs Can withstand the hot, dry summer by becoming dormant Fire is common feature Wide variety of animal life Not much still in existence because of human activity 16-39

40 Mediterranean Shrublands (chaparral) 16-40

41 Tropical Dry Forest Characterized by seasonal rainfall Heavy monsoons for several months are followed by extensive dry periods. Plants have special adaptations for withstanding drought. Animals are similar to tropical rain forest, but not as abundant 16-41

42 Tropical Dry Forest 16-42

43 Desert Very dry areas where rainfall levels are low and irregular Either extremely hot or cold Show large daily fluctuations in temperature Characterized by scattered thorny plants Lack leaves as an adaptation to the dry climate Stems are green and undergo photosynthesis Many store water in their stems (cacti) Contains flowering plants, insects, reptiles, and mammals These species are active at night and burrow during the day.

44 Desert 16-44

45 Boreal Coniferous Forest Also known as Northern coniferous forest Taiga Long, cold winters Dominated by evergreen trees Adapted to long, cold winters and short growing seasons Spruce, firs, pines 16-45

46 Boreal Coniferous Forest Evaporation is low, therefore, this climate is humid. Animals include mice, snowshoe hare, lynx, bears, wolves, squirrels, moose, midges, and flies. Found in northern regions of the US, and southern Canada, northern Europe and Asia 16-46

47 Boreal Coniferous Forest 16-47

48 Temperate Rainforest Wind from ocean brings moister air to the coast Moisture falls as rain or snow. Abundant water, fertile soil and mild temperatures Plants include evergreens like spruce, fir, hemlock. As well as deciduous trees such as red alder, maple, cottonwood Trees are covered in mosses, ferns, etc. Found in coastal areas of northern California, Oregon, Washington, British Columbia, and southern Alaska

49 Temperate Rainforest 16-49

50 Tundra Characterized by extremely long, severe winters Short, cool summers Short growing season (less than 100 days) Low rainfall Deep layers of soil remain frozen (permafrost) Very few animals and plants can survive. No trees Plants include grasses, sedges, shrubs, lichen. Animals include caribou, wolves, fox, snowy owls, mice, insects. Found in the extreme north (Alaska)

51 Tundra 16-51

52 Tropical Rainforest High temperature Rainfall everyday Thousands of plants and animals Balsa, teak, ferns Trees covered with orchids vines and mosses Tree frogs, bats, lizards, birds, monkeys, and insects Found primarily at the equator Human clear-cutting, coupled with the excess rainfall, causes extensive leaching of the soil

53 Tropical Rainforest 16-53

54 The Relationship Between Elevation and Climate Air temperatures are warmest near the equator and become cooler toward the poles. Air temperature decreases as elevation increases. Traveling from the ocean to mountain peaks will lead through the same biomes as traveling from the equator to the north pole

55 The Relationship Among Elevation, Latitude and Vegetation 16-55

56 Major Aquatic Ecosystems Can be separated into: Marine: salt content greater than 35 parts per thousand Freshwater: salt content less than 0.5 parts per thousand Also vary in terms of: depth of water how far sun s rays penetrate water nature of bottom substrate water temperature

57 Major Marine Ecosystems Pelagic consists of organisms that float or actively swim in the ocean Benthic consists of organisms that live on the ocean floor Estruaries shallow, partially enclosed areas where water enters the ocean 16-57

58 Pelagic Marine Ecosystem Plankton are so small and weakly swimming that they are carried by the ocean currents Phytoplankton carry out photosynthesis Majority are bacteria or algae Commonly found in the upper layer of the ocean, known as the euphotic zone Zooplankton are weakly swimming animals that feed on phytoplankton. Dependent on material dissolved in the water 16-58

59 Role of Plankton in Marine Ecosystems 16-59

60 Benthic Marine Ecosystems Consists of organisms that live on ocean floor (whether attached or not) Photosynthesis by seaweed can occur in shallow regions Material that makes up the ocean bottom is important in determining the type of community. Sand makes it difficult for plants to attach, but is good for crustaceans. Mud provides suitable habitat for rooted vegetation, and burrowing organisms that filter feed in the water above the mud. Rocky surfaces provide a good substrate for large algae and a variety of animals. Temperature also affects which type of benthic community arises.

61 Two Types of Benthic Marine Ecosystems Coral reef ecosystem Dependent upon photosynthesis, so found at shallow depths Abyssal ecosystem Not dependent upon photosynthesis, so found at great depths 16-61

62 Coral Reef Ecosystem Produced by coral animals that build cup-shaped external skeletons around themselves Corals protrude from their skeletons to catch food and be exposed to sunlight. While coral animals are not themselves photosynthetic, they harbor photosynthetic algae. Coral skeletons provide a surface upon which many animals live. Considered one of the most productive ecosystems 16-62

63 Coral Reef Ecosystem 16-63

64 Abyssal Ecosystem No light for photosynthesis Rely on organic material from euphotic zone All organisms are scavengers, eating material that drifts their way. Some animals generate light to aid in their search for food

65 Estuary Shallow, partially enclosed areas where freshwater meets the ocean Saltiness changes with the ocean tides and the flow of the rivers. Organisms are specially adapted to these conditions. Phytoplankton and algae provide photosynthetic activity which supports the ecosystem. Important as nursery sites for fish and crustaceans Serve to trap river sediments from entering ocean 16-65

66 Human Impact on Marine Ecosystems Over-fishing has destroyed many traditional fishing industries. Estuaries are impacted by the flow of fertilizer, animal waste and pesticides downriver. The use of oceans for transport results in oil and trash pollution. Coral reefs are impacted by over-fishing and siltation from rivers.

67 Freshwater Ecosystems Amount of salt present is lower than marine Temperature of water can change greatly Water is in the process of moving to the ocean. Oxygen can be in short supply. Two major types: Lakes and ponds: water is relatively stationary Streams and rivers: water is running downhill 16-67

68 Lakes and Ponds Large lakes are similar to oceans in that there is a deep, non-photosynthetic zone and a euphotic zone in shallower regions. Flowering plants rooted in the bottom are present along the shore. Emergent plants have leaves that float on or protrude above the surface (cattails, water lilies). Submerged plants stay below the surface (Elodea, Chara). Region with rooted plants is called the litteral zone; region without rooted plants is the limnetic zone. Dissolved oxygen is important for the ecosystem. Oxygen comes from photosynthesis, or by mixing of air into the water by wave action

69 Lakes and Ponds 16-69

70 Streams and Rivers Since water is moving, plankton organisms are not as important as attached organisms. Most algae grows attached to rocks or other attached surfaces. It is difficult for photosynthetic organisms to accumulate nutrients necessary for growth. Debris is used as a source of food

71 Human Impact on Freshwater Ecosystems Any activity on land eventually affects freshwater ecosystems because of runoff. Agricultural runoff, sewage, sediment, and trash all make their way to streams and lakes

72 Succession A climax community is a stable, long-lasting community. When communities change from one type to another, succession occurs. Successional stages lead to a climax community. Primary succession occurs when a community develops in a previously uninhabited location. Secondary succession occurs when a community is disturbed and then has to re-grow

73 Primary Succession Relatively rare because there are few areas that are not already inhabited Tops of mountains, newly formed volcanic rock 16-73

74 Primary Succession Pioneer organisms grow first and establish a pioneer community. Bacteria, algae, fungi, and lichens Lichens are particularly important. Combination of algae and fungi Able to grow on bare rock Capable of photosynthesis and can form new organic matter Small consumers can eat lichen. Breaks down rock and liberates minerals Soil begins to form.

75 Primary Succession As soil forms, small plants become established. This adds more soil. As larger plants grow, animal consumers move in. Introduces shade, smaller plants die out Succession from this point depends on the climate

76 Pioneer Organisms 16-76

77 Primary Succession 16-77

78 Secondary Succession Occurs after a community is altered by a natural or human-induced disaster Hurricane, fire, abandoned agricultural land Soil is already present. A reservoir of seeds from plants still exists from the original community. A pioneer community of weeds appears first. Then grasses emerge. Grasses can support insects, small mammals, and birds. If rainfall is adequate Shrubs and small trees will begin to grow. Larger trees will follow and grasses will die out.

79 Succession From a Pond to a Wet Meadow 16-79

80 Secondary Succession on Land 16-80

81 The Impact of Human Activities on Communities Humans have affected almost every community on earth. We must analyze the effects of our actions when we manipulate a community. Analyzing the impact of human activity on communities is crucial for the future of our environment

82 Introduced Species Humans have introduced many species into new communities, both planned and accidental. Agricultural species are almost always introduced species. Cattle have displaced native grazers in the Midwest. Pigs are destroying natural communities in Hawaii. Accidental introductions significantly alter communities. Chestnut blight Fungal disease Zebra mussels

83 Introduced Species 16-83

84 Predator Control Humans have destroyed large predators to protect livestock. The absence of predators has led to a number of problems. Deer have become over-populated. Alligators present problems to pets and children. Elk and bison populations have increased in national parks

85 Predator Control 16-85

86 The Reintroduction of Wolves to Yellowstone 16-86

87 Habitat Destruction Human activity has destroyed the habitat of many communities. Communities with less species diversity are more fragile and susceptible to damage by human activity. The tundra has been severely affected by human activity. Human activity has impacted certain species by destroying their habitat. Whales, condors, eagles, etc. Converting land to farmland or developing land destroys habitats.

88 Habitat Destruction 16-88

89 Endangered and Threatened Species 16-89

90 Pesticide Use Herbicides kill plants; insecticides kill insects. Continual use of pesticides selects for resistant organisms. This makes the pesticides no longer useful. Pesticides also kill other valuable organisms. Natural predators and parasites can kill pests. Take longer than pesticides, but do not negatively impact the community Integrated pest management Involves using pesticides and encouraging the growth of natural pest enemies

91 Pesticide Use 16-91

92 Biomagnification The continual use of chemical pesticides and fertilizers significantly impact the food chain. Chemicals ingested by organisms in the lower trophic levels are passed to successively higher trophic levels. The chemicals accumulate as they are passed to higher trophic levels. This can result in the death of secondary and tertiary consumers. This is called biomagnification. DDT, PCBs, dioxins, methylmercury 16-92

93 Biomagnification of DDT 16-93