Aim: What determines ecosystem structure?

Date: November 8, 2013 Catalyst: A mouse population is 25,000 and is

decreasing in size at a rate of 20% per year. What is the mouse population after 3 years?

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QOTDDuring the evolutionary process, which is the correct sequence of events?

A. Change in phenotype -> change in genotype -> speciation -> selection

B. Speciation -> change in genotype -> selection -> change in phenotype

C. Speciation -> selection -> change in phenotype -> change in genotype

D. Change in genotype -> change in phenotype -> selection -> speciation

E. Selection -> speciation -> change in phenotype -> change in genotype

Agenda

• Interspecific Interactions

• Species Richness and Diversity

• Trophic Structure and Food Chains

• Review and Additional Help

Name that Symbiosis!

Name that Symbiosis!

Parasitism

Species Richness and Relative Abundance

Species Richness and Relative Abundance

Species Richness and Relative Abundance

• Species Diversity is made up of Richness and Abundance

• Species richness - number of different species

• Relative Abundance - number of individuals of each species

Diversity and Community Stability

Diversity and Community Stability

• Communities with high Biodiversity are more stable

• Each species has a niche in the ecosystem, from producer to consumer

• Invasive species can disrupt this

Invasive Species

Invasive Species

• Ecosystems can be disrupted by a non - native species entering into the environment

• These organisms may be more fit for the environment, displacing a native organism from its niche

Trophic Levels

• Feeding relationships between organisms

An important species in the chesapeake bay estuary is the blue crab. It is an omnivore, eating eelgrass and other primary producers as well as clams. It is also a cannibal. In turn, the crabs are eaten by humans and by the endangered Kemp’s Ridley sea turtle.

A. Based on this information, draw a food web that includes the blue crab.

B. What do you think would happen to the abundance of eelgrass if humans stopped eating blue crabs?

An ecologist studying plants in the desert performed the following experiment. She staked out two identical plots, each of which included a few sagebrush plants and numbers small annual wildflowers. She found the same five wildflowers species in roughly equal numbers on both plots. She then enclosed one of the plots with a fence to keep out kangaroo rats, the most common grain - eaters of the area. After two years, four of the wildflower species were no longer present in the fenced plot, but one species had increased drastically. The control plot had not changed in species diversity. Using the principles of community ecology, propose a hypothesis to explain her results. What additional evidence would support your hypothesis?