Ricklefs Chapter 27
1) What are 4 human activities that are threatening ecological processes?
- Species Introduction
- Habitat Conversion
- Irrigation and Water Use
2) Explain how many consumer-resource interactions reach a steady state.
Consumption of a particular resource will eventually become scarce. When this occur the consumer populations will being to decline or the consumer will find an alternative resource to fulfill its needs. This will continue until the consumer population has achieved normal levels or the original resource has been brought back into balance.
3) Describe shifting agriculture.
First, the trees and other flora in a particular patch of land are burned; this releases nutrients into the soil. These regions are cultivated until the fertility of the soil has dropped, which occurs after a few years. The population will then abandon that patch in search for another. After the disturbance the abandon area can recover.
4) Which reduces pressure on water supplies, cereal grains or meat?
Cereal grains. 1.5 km^3 of water is used to produce 1 kilogram of cereal grains as opposed to meat which consumes anywhere from 6-15 km^3 for one kilogram.
5) What are the classes of toxins?
- Heavy metals
- Organic compounds
- Radioactive substances
6) Should we concern ourselves with toxins if they are found naturally in the ecosystem? Why?
Yes, because human activities have caused many of these substances to accumulate in nature and in some areas at very nigh levels. These levels have cascading negative effects in nature.