Biology Homework Chapter 35: Social Behavior
Textbook Assignment: Chapter 37: Ecological Structures, sections 14-21.
- 37.14 Ecosystems depend on energy and material (chemical) flows. Energy supply limits the flow of food chains and number of trophic levels.
- 37.15 The ability of a region to support communities (measured by their biomass) depends on the amount of solar energy available to the community. The production of biomass by this energy is primary production, since the conversion of energy occurs at the first trophic level, sunlight to producers.
- 37.16 Energy available for primary production limits the number of links or trophic leves represend in a food chain, since each level receives about 1/10 of the energy available to the previous level. While many individuals can be supported in species at the first trophic level, very few can be supported in species at the fourth trophic level, which receives 1/100000 of the solar energy supplied to the region.
- 37.17 Animals (including humans) that depend on second or third trophic level species (meat) require more energy than animals that depend on first trophic level species (plants). More individuals of omnivore species can be supported as vegetarians than as carnivores.
- 37.18 Chemical recycling allows element atoms to be used over and over by different organisms.
- 37.19 The carbon cycle moves carbon from air to plant producers to animal consumers to animal, plant, and fungi decomposers though multiple pathways, depending on the complexity of the food chain supporting the consumers.
- 37.20 The phosphorus cycle moves phosphorus from the soil to the water supply to plants to animals to decomposers.
- 37.21 The nitrogen cycle is dependent on specific bacteria which break up atmospheric nitrogen and bind it to hydrogen (called "fixing nitrogen") in ammonia ion complexes, which are then absorbed by plants and animals, and returned to the soil through decomposition and wastes. This "single pathway" cycle is unique to nitrogen, which otherwise requires huge energy expenditures to pull in its diatomic state from the atmosphere.
- 37.22 An imbalance of nutrients in an ecosystem gives some species an advantage over the others, and the species may grow to the point where it consumes all available energy resources. This is most often seen in aquatic systems, where the oxygen supply required by all species is limited.
- 37.23 Humans create ecosystems by diverting natural resources to specific uses, such as agriculture and human habitation. In many cases, the disruption to the native community is followed by overconsumption of the resources, making the human ecosystem fragile as well. Sustainable practices in agriculture and habitat design attempt to create ecosystems in balance, where use does not outstrip available energy or other resources, and in many cases, recycles resources for later use.
Read the following weblecture before chat: Ecosystems
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Use the Nitrogen Cycle activity at the PBS learning site to explore how nitrogen cycles through the environment.
- Click on the launch button and read the short introduction.
- Click on the STEP (right) button to step through the animation.
- How does N2 move from the atmosphere to living organisms?
- What is nitrogen fixation? What organisms are needed to make this happen?
- What is ammonification? What organisms are needed to make this happen?
- What is nitrification? What organisms are needed to make this happen?
- How does nitrogen return to the atmosphere?
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.
- Required: Complete the Mastery Exercise with a score of 85% or better.
- Optional: Test yourself with the textbook multiple choice questions and note any that you miss that still don't make sense. Bring questions to chat!
- Go to the Moodle and take the quiz for this 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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