Chap 20

Resources and Consumers

Ecology 2000

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 2000 3

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 2000 4

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

Ecology 2000 5

Fig. 20-1 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 2000 6

20.2 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 2000 7

Fig. 20-1 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 2000 8

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 2000 9

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

Ecology 2000 10

Ecology 2000 11

Fig. 20-4 Filtering rate and ingestion rate of individual Daphnia magna feeding on cultures of the alga at different food densities.

Ecology 2000 12

Ecology 2000 13

Fig. 20-5 Graphic representation of selected data from Table 20-2.(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 105 cells cm-3.

Ecology 2000 14

問題與討論問題與討論

請提出問題！