Outline. Ecology: Succession and Life Strategies. Interactions within communities of organisms. Key Concepts:

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1 Ecology: Succession and Life Strategies Interactions within communities of organisms u 1. Key concepts Outline u 2. Ecosystems and communities u 3. Competition, Predation, Commensalism, Mutualism, Parasitism 4. Succession u 5. Conclusions Key Concepts: 1. A habitat is the type of place where individuals of a species normally live 2. Every species in the community has its own niche 3. Interactions among species influence the structure of a community 4. The first species to occupy a habitat are replaced by others 5. Different stages of succession often exist in the same habitat

2 Ecosystems and communities Ecosystem: all factors affecting an organism s survival: abiotic and biotic Individuals of a species form populations living in a given habitat Several populations interact to form communities within a habitat Many communities + abiotic factors form an ecosytem Everything interacts! Each organism plays a special role within a community Competition Predation Commensalism Mutualism Parasitism Competition Organisms compete for same resources by innate complex behaviors or by adaptive fitness Competitive exclusion: if resources are limited, the most efficient of two competing species will eliminate the other species in that location

3 Competition Niches: organism s place in an ecosystem Realized: the niche an organism actually occupies in a given ecosystem Fundamental: niche it could occupy in the absence of competition Two species cannot occupy exactly the same niche indefinitely Competition Resource Partitioning Three annual plants in a plowed abandoned field All require water and minerals but differ in adaptations for securing them

4 Predation Relationship in which an organism of one species (predator) kills and eats an organism of another species (prey) Predator may: kill all prey and then die itself (no food) kill most prey; predator dies; some prey hide and survive go through alternating cycles of predation and recovery along with prey Predation Predation Other factors affecting predator/prey interaction: Prey dispersal pattern Other predators or prey in community Coevolution: evolutionary adjustment of characteristics of both predator and prey Protective Coloration: prey adaptations Mimicry of organisms with defenses Camouflage for concealment

5 Commensalism Commensalism: an organism of one species benefits from its interactions with another; the other species neither benefits nor is harmed EX: epiphytes; barnacles; clownfish and anemones Mutualism A relationship where two species live together in close association, with benefits for both Frequently one species gets protection and/or support while the other gets food or a home or transportation Parasitism Relationship in which an organism of one species (the parasite) lives in or on another (the host). The parasite benefits; the host is usually harmed successful parasites do not kill the host Parasites may be viruses, bacteria, fungi, protists, invertebrates Host/parasite interactions are examples of coevolution; dynamic natural selection

6 Succession Dynamic process of change in an environment where a sequence of communities replaces one another over time Primary succession: in areas not previously supporting organisms pioneer community climax community Secondary succession: in areas originally occupied but disturbed by humans or nature Succession In Conclusion 1. A habitat is the type of place where individuals of a given species normally live 2. Each species has its own niche in the community 3. Mutualism, commensalism, competition, predation, and parasitism are species interactions that directly or indirectly link the populations in a community

7 In Conclusion 4.Species that require the same limited resource tend to compete 5.The classical model of ecological succession explains how a community develops from its pioneer species to an array of species