Presentation on theme: "G5: Population Ecology (4 hours). G.5.1 Distinguish between r-strategies and K-strategies. How resources are invested!! r-strategy –produce many offspring."— Presentation transcript:
G5: Population Ecology (4 hours)
G.5.1 Distinguish between r-strategies and K-strategies. How resources are invested!! r-strategy –produce many offspring –short life span –early maturity –reproducing only once –having a small body size K-strategy –development and long-term survival. –longer life span –late maturity –more likely to involve parental care –production of few offspring –reproducing more than once Some organisms display extreme r- or K-strategies, but most organisms have life histories intermediate on the continuum. Some organisms such as Drosophila switch strategies depending on environmental conditions
G.5.2 Discuss the environmental conditions that favour either r-strategies or K-strategies. In a predictable environment, in order to maximize fitness, it pays to invest resources in long-term development and long life (K-strategy). In an unstable environment, it is better to produce as many offspring as quickly as possible (r-strategy). Of concern is that ecological disruption favors r-strategists such as pathogens and pest species.
G.5.3 Describe one technique used to estimate the population size of an animal species based on a capture–mark–release–recapture method. Various mark-and-recapture methods exist. Lincoln index (which involves one mark–release– recapture cycle) is required: Population size (N) = (n 1 x n 2 ) / n 3 n 1 = number of individuals initially caught, marked and released n 2 = total number of individuals caught in the second sample n 3 = number of marked individuals in the second sample. choosing an appropriate method for marking organisms
G.5.4 Describe the methods used to estimate the size of commercial fish stocks.
G.5.5 Outline the concept of maximum sustainable yield in the conservation of fish stocks. Student Debates –groups- representing at least 2 countries Fishermen Conservationists Politicians Aim 8: There are clear ethical, social, environmental and economic issues here, some of which conflict with each other. TOK: Data about fish stocks is very difficult to obtain and interpret, allowing huge differences in views on what is sustainable. In addition to fishing, whale hunting is an area where there is widespread disagreement about what is sustainable and also what is ethical.
G.5.6 Discuss international measures that would promote the conservation of fish. Aim 8: As in G.5.5, there are many issues involved here, and there is a chance to discuss the need for international agreement and cooperation in a world that is largely governed at a national level, with large areas of ocean under no government control at all. TOK: This is a chance to discuss decision- making, based partly on scientific evidence, that has to take place at an international level.