Lecture 23 Exam Questions


1. How does human intervention exasperate species extinction?
i. Habitat Loss and fragmentation – In many cases, the extent of biodiversity is directly related to habitatable area in a given ecosystem. Intrusion by humans into these areas reduces the ability of the ecosystem to support larger populations of species. Also, fragmentation limits individual dispersal, making a population increasingly exposed to climate changes, often resulting in extinctions of local populations.
ii. Small population size – Natural variations in population size can make a species more susceptible to extinction at a given point in time, known as stochastic extinction. Habitat fragmentation can accelerate this phenomenon, especially with larger predators who typically have low population densisites.
iii. Overexploitation – Hunting, fishing, deforestation, agriculture and other activities put severe stress on native populations that didn’t evolve to contest against the harvesting humans employ to draw natural resources. Certain species’ lack of defenses and failure of hunters to recognize the dangers of exploitation have led to rapid extinctions.
iv. Species introductions – New predators, competitors or pathogens introduced by humans can have dramatic effects on an ecosystem. Native species may not have the evolutionary defenses to cope to aggressive new entrants nor the time to adapt.
v. Emerging diseases – Animals and plants get sick too and human behavior can sometimes carry infectious diseases and bacteria to new exotic locals where current inhabitants have no natural defenses.

2. How can we measure the value of biodiversity?
Social, economic, moral and ecological issues all come into play when species biodiversity is challenged. Some argue that humankind has a moral responsibility to respect plant and animal life. Others measure biodiversity in terms of the economic value that can be assigned to the many components that comprise an ecosystem. Of course, this perspective stratifies the natural world and assigns greater value to some animal and plant life than others. Biodiversity can also be a value indicator of environmental vitality and ecosystem functionality. Certain species, such as predators or other “keystone” species, have intrinsic value for stabilizing ecosystem sustainability (such as those we’ve explored in our stella labs).

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