Biology Homework Chapter 37: Communities and Species Interactions
Textbook Assignment: Chapter 37: , sections 1-10
- 37.1 Communities include all the organisms of all species populations in a given area.
- 37.2 Interactions between species are dynamic (constantly changing) and may help the community stabilize or become imbalanced. Some interactions that are mutually beneficial to both species involved (mutualism, symbiotic relationships), but others (parasitism, predation) benefit one species at the expense of another. Herbivory may be considered a special case of predation, where animals depend on plants for nourishment, but generally do not wipe out the plant populations altogether.
- 37.3 Competition occurs whenever a resource is limited, and can take place between species (interspecific); and between species who occupy similar niches (competitive exclusion). A niche is the role a species plays in the community.
- 37.4 In mutualism between two species, each species involved provides some resource, usually food or shelter, for the other. An example: corals and dinoflagellates in coral reefs.
- 37.5 Predator-prey relationships create complex population changes and alignments. Prey may attempt to avoide predators by mimicking poisonous by species that are benign (Batesian) or also poisonous (Mullerian mimicry).
- 37.6 Herbivory (predation of plants by animals) gives rise through natural selection to plants which can avoid predators by defensive means, such as spiky leaves and foul smelling or noxious secretions. In some cases, plants limit but do not eliminate predators, creating dependence by specific species on the plant (coevolution).
- 37.7 Parasitic relationships are similar to predation in which one individual benefits and the other suffers, except that the predator is usually smaller than, and lives on, the host prey.
- 37.8 Trophic structure follows the flow of energy from plants (producers) through first consumers and higher levels of consumers. Detrivores or decomposers return raw materials to the cycle.
- 37.9 Since individual organisms can operate at different tropic levels, we talk about food webs rather than food chains.
- 37.10 Species richness measures the number of types of species in a community; species abundance measure the number of individual organisms of each species in the community. Both contribute to the overal species diversity of a community.
- 37.11 Keystone species are critical species within a given community whose presence controls the species abundance of other species in the community. We measure the presence of a species within the community by its biomass, that is, its total living mass, which requires an average amount of energy to maintain. If the dependency of other species on the keystone species is high, it will have more effect than other species with the same biomass.
- 37.12 Disturbances damage communities; ecological succession is the transition of the species composition in a community over time. Primary succession occurs when life returns to an area after a major catastrophe that requires soil first. Secondary succession occurs when soil already exists.
- 37.13 Invasive species introduced to a community where they lack natural predators to control their population may overwhelm native species by outcompeting them for available resources.
Read the following weblecture before chat: Communities Characteristics
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Read through the description of Moose-Wolf interactions at Isle Royale.
- How are wolf populations determined (i.e, what factors cause the wolf population to change)?
- How are moose populations determined?
- Why is the interaction between the two populations not a simple boom-and-bust cycle?
- What does it mean to say the moose population is "unstable"?
- Which appears to have more affect on the moose population, wolf predation or severe winters? What information is needed ot determine this?
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- No quiz yet: the Chapter Quiz opens when we finish the chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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