Structure Species Interaction Succession & Sustainability Community Ecology CHAPTER 8 Structure Species Interaction Succession & Sustainability

Stability of ecosystems Key Concepts Community structure Roles of species Species interactions Changes in ecosystems Stability of ecosystems

CASE STUDY: FLYING FOXES fruit-eating bats pollinate flowers from Durian trees  prized fruit in SE Asia  strong odor, custard-like “delicious” fruit mutualism (durian & flying fox) referred to as keystone species  pollinate plant species  disperse plant seeds in dropping (biodiversity)

- stratification, relative size, distribution COMMUNITY STRUCTURE OBJ 8.1 CHARACTERISTICS Physical Appearance - stratification, relative size, distribution Species Diversity - richness vs. eveness Niche Structure - ecological Roles of Species

Community Structure: Appearance and Species Diversity Stratification Fig. 8-2 p. 144

SPECIES DIVERSITY Species richness: # different species Species evenness: abundance within each of its species Sample A could be described as being the more diverse as it contains three species to sample B's two. But there is less chance in sample B than in sample A that two randomly chosen individuals will be of the same species.

Three Factors Affecting Biodiversity Latitude(terrestial)- the closer to the equator, the higher the biodiversity Highest species diversity in tropics; lowest in polar regions Depth(aquatic)- biodiversity increases with depth to @ 2000 m then begins its decrease Pollution- as levels increase, biodiversity decreases Species diversity 25 20 15 5 10 2,000 4,000 6,000 Depth (meters) Coast Deep Sea Snails Tube worms Fig. 8-3 p. 145 Ants Birds

Number of diatom species Unpolluted stream Polluted Number of individuals per diatom species Figure 8-4 Page 145

Island Biodiversity Theory of Island Biogeography-the number of species found on an island is determined by: Species immigration Immigration- movement of organisms into a place Emigration- movement of organisms out of a place Species extinction High Low Rate of immigration or extinction Equilibrium number Immigration and extinction rates Number of species on island (a) © 2004 Brooks/Cole – Thomson Learning

Island Species Effect of island size (b) High Low Rate of immigration or extinction Small island Effect of island size Number of species on island (b) Large island © 2004 Brooks/Cole – Thomson Learning High Low Rate of immigration or extinction Far island Effect of distance from mainland Number of species on island (c) Near island © 2004 Brooks/Cole – Thomson Learning 100 50 25 12.5 6.25 2,000 4,000 6,000 8,000 10,000 Distance from New Guinea (kilometers) Number of species (percentage of sample studied) 100 1 10 1,000 10,000 100,000 Area (square miles) Number of amphibian and reptile species

General Types of Organisms OBJ 8.2 General Types of Organisms Native-organisms that are naturally found in an ecosystem; Nonnative (Exotic/ Invasive/Alien)- any organism that is not found naturally in an ecosystem; usually transported in by humans Indicator- organisms that serve as early warnings of damage to a community Keystone- organisms whose role in more important than their numbers or biomass; Strong interactions with other species affect the life of others Process out materials out of proportion to their numbers or biomass

OBJ 8.3 Competition Competition—Two organisms compete to obtain the same limited resource, and both are harmed to some extinct. Intraspecific—Members of same species competing for resources. Interspecific—Members of different species competing for resources. The more similar the competing species, the more intense the competition.

OBJ 8.4 Competition Competitive Exclusion Principle—No two species can occupy the same ecological niche in the same place at the same time. Less fit species must evolve into a slightly different niche.

Resource Partitioning OBJ 8.5 Resource Partitioning Overlapping Niche of 2 species creates competition Over time, species evolve and become specialized Fig. 8-7 p. 150

Kinds of Organism Interactions Predation—One animal kills/eats another. Predator benefits from food. Prey adaptation is manifested in a higher reproduction rate. Prey species benefits by eliminating non-adaptive genes from the gene pool. Poorly adapted predators are less likely to obtain food and thus pass on non-adaptive genes.

PREY: DEFENSE MECHANISMS adaptation the prey uses adds to the chances of survival for the species Examples of some defense mechanisms prey use are:  Chemical combat  Camouflage  Speed  Trickery: false features and mimicry

Symbiotic Relationships OBJ 8.7 Symbiotic Relationships Symbiosis—Close, physical relationship between two different species. At least one species derives benefit from the interaction. Parasitism—One organism (parasite) living in or on another organism (host), from which it derives nourishment. Ectoparasites—Live on host’s surface. Fleas Endoparasites—Live inside host. Tapeworms

Symbiotic Relationships Commensalism—One organism benefits, while the other is unaffected. Remoras and Sharks Mutualism—Both species benefit. Obligatory in many cases as neither can exist without the other. Mycorrhizae

WHAT IS HAPPENING?

Succession Succession—A series of regular, predictable changes in the structure of a community over time. Activities of organisms change their surroundings and make the environment suitable for other kinds of organisms. Climax community—Stable, long-lasting community, primarily determined by climate.

OBJ 8.8 Succession Primary Succession—Begins with bare mineral surfaces or water and total lack of organisms. Secondary Succession—Begins with disturbance of an existing ecosystem. Much more commonly observed.

Primary Succession Terrestrial Primary Succession Pioneer Community: Collection of organisms able to colonize bare rock (i.e. lichens, mosses). Lichens help break down rock, and accumulate debris helping to form a thin soil layer. Soil layer begins to support small life forms.

Terrestrial Primary Succession Lichen community replaced by annual plants. Annuals replaced by perennial community. Perennial community replaced by shrubs. Shrubs replaced by shade intolerant trees. Shade intolerant trees replaced by shade tolerant trees. Stable, climax community often reached. Successional (seral) Stage—Each step in the process.

Terrestrial Primary Succession OBJ 8.9 Terrestrial Primary Succession

Climax Community Characteristics Maintain species diversity for extended period. Multiple specialized ecological niches. High level of organism interactions. Nutrients recycled and biomass levels remain constant.

Aquatic Primary Succession Except for oceans, most aquatic systems are considered temporary. All aquatic systems receive inputs of soil particles and organic matter from surrounding land. Gradual filling of shallow bodies of water. Roots and stems below water accumulate more material. Wet soil established.

Aquatic Primary Succession

Secondary Succession Occurs when an existing community is disturbed or destroyed. With most disturbances, most of the soil remains, and many nutrients necessary for plant growth may be available for reestablishment of the previous ecosystem. Nearby undamaged communities can serve as sources of seeds and animals. Tends to be more rapid than primary growth.

Terrestrial Secondary Succession

Modern Concepts of Succession and Climax As settlers changed “original” ecosystems to agriculture, climax communities were destroyed. Many farms were abandoned, and land began to experience succession. Ecologists began to recognize there was not a fixed, pre-determined community. Only thing differentiating climax community from successional community is time scale.