Chap 20 Resources and Consumers Ecology 2000

2  20.1 Species interactions may be categorized based on the effect of the interaction on the species involved.  20.2 What are resources and consumers?  20.3 A water flea consumer and an algal resource reveal the characteristics of a consumer-resource system. Resources and Consumers

Ecology  20.4 Rates of change in resource level and consumer population growth can be dynamically coupled with logistic models.  20.5 The Monod equation relates population growth rate to the abundance of a single resource.  20.6 Two resources can simultaneously limit a consumer population.  20.7 Consumer-resource systems may involve more than two resources or more than one consumer.

Ecology Species interactions may be categorized based on the effect of the interaction on the species involved.

Ecology Fig A schematic diagram of the relationships between species involved in (a) resource-consumer interactions, (b) competition, and (c) indirect competition. Solid arrows indicate the direction of consumption; dashed arrows indicate competitors. Resource-consumer interactions competition Indirect competition

Ecology What are resources and consumers?  A resource is a substance or an object that is required by an organism for normal maintenance, growth, and reproduction.  When a resource is used, its amount is reduced.  Types of resources: nonrenewable resources and renewable resources

Ecology Fig Three types of relationships between consumers and renewable resources. (a) A resource external to the place where it is consumed. (b) A resource generated near the place where it is consumed. (c) A resource that arises near where a consumer uses it, but is used first by an intermediate consumer. (d) Nitrogen cyclings as an example of indirect linkage between consumer and resource.

Ecology Limiting resources  Consumption reduces the availability of a resource.  What is used by one organism cannot be used by another.  By diminishing their resources, consumers limit their own population increased.  Populations were limited by the single resource having the greatest relative scarcity. This principle has been called Liebig's law of the minimum.

Ecology A water flea consumer and an algal resource reveal the characteristics of a consumer-resource system.

Ecology

Ecology Fig Filtering rate and ingestion rate of individual Daphnia magna feeding on cultures of the alga at different food densities.

Ecology

Ecology Fig Graphic representation of selected data from Table (a) Increased food resulted in more eggs per brood. (b) The percentage of the population reproducing showed the same pattern as broods per female because of reduction in life expectancy. The net reproductive rate was highest at 10 5 cells cm -3.

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