Chapter 3 Review Questions

F (see “Part B: The Ecosphere”)

T (see “Introduction”)

F (see “Energy”)

T (see “Energy”)

F (see “Law of Thermodynamics”)

F (see “Biotic Pyramids”)

F (see “Producers and Consumers”)

T (see “Producers and Consumers”)

T (see “Food Chains”)

F (see “Biodiversity in Canada”)

The scientific community now understands that Indigenous peoples often have detailed knowledge of their local environments, which is not surprising for peoples gaining their sustenance directly from that environment. Indigenous peoples tend to undertake the same kinds of tasks as Western scientists, such as classification and naming of different organisms and studies of population dynamics, geographical distributions, and optimal management strategies. In contrast to Western science, however, this knowledge is rarely recorded in written form but is handed down orally from generation to generation.

(see “Part B: The Ecosphere”)

The ecosphere is an area that stretches from the depths of the ocean trenches up to the highest mountain peaks and is a product of the combination of three layers that combine to produce the conditions necessary for life. These are the hydrosphere, lithosphere, and atmosphere.

(see “Introduction”)

Energy is the capacity to do work and is measured in calories.

(see “Energy”)

Energy derived from an object’s motion and mass is known as kinetic energy (e.g., heat), whereas potential energy is stored energy that is available for later use (e.g., gasoline).

(see “Energy”)

The law of conservation of energy (the First Law of Thermodynamics), tells us that energy can neither be created nor destroyed; it is merely changed from one form into another. The second law of thermodynamics, (the law of entropy), tells us that when energy is transformed from one form into another, there is always a decrease in the quality of usable energy.

(see “Laws of Thermodynamics)

Organisms with the ability to capture energy and manufacture matter are known as autotrophs or producers. All other organisms obtain their energy supply through eating other organisms and are known as heterotrophs or consumers. There are two kinds of autotrophs: phototrophs and chemoautotrophs. Phototrophs obtain their energy from light; chemoautotrophs gain energy from chemicals in the environment.

(see “Producers and Consumers”)

The energy pyramid has important implications for humans. For example, it takes between 8 and 16 kilograms of grain to produce 1 kilogram of beef. This means that more land must be cultivated to provide people with a diet high in meat as opposed to a diet based on grains. Since humans are one of the species that can access food energy at several different trophic levels, in terms of energy efficiency it would be better to operate as low on the food chain as possible—that is, as primary consumers or vegetarians.

(see “Biotic pyramids”)

A food chain is a simple model of ecosystem energy transfer between trophic levels. In reality, there are many competing organisms and energy paths representing food webs rather than simple food chains.

(see “Food Chains”)

Carnivores must always have the lowest numbers in an ecosystem in order to be supported by the energy base below, and since there are losses at each level, there is little left at upper trophic levels.

(see “Food Chains”)

Productivity in ecosystems is measured by the rate at which energy is transformed into biomass, Gross primary productivity (GPP) is the overall rate of biomass production, but there is an energy cost to capturing this energy. This cost, cellular respiration (R), must be subtracted from the GPP to reveal the net primary productivity (NPP). This is the amount of energy available to heterotrophs. Net community productivity can also be measured, which includes heterotrophic and autotrophic respiration.

(see “Productivity”)

The ecosphere can be broken down in size into smaller units. At the smallest level is the individual organism. A group of individuals of the same species is a population. The populations in a particular environment are known as a community. The ecosystem is a collection of communities interacting with the physical environment. Similar ecosystems can be grouped together as ecozones, representing their dominant vegetation and animal communities. In turn, these can be grouped into the largest classification of life forms, biomes, based upon dominant vegetation and adaptations of other organisms to that particular environment.

(see “Ecosystem Structure”)

Abiotic components play an important role in determining how biotic components are distributed.

(see “Abiotic Components”)

See Figure 3.12 (“Abiotic Components”):

The limiting factor principle tells us that all factors necessary for growth must be available in certain minimum quantities if an organism is to survive. The most limiting factor, or weakest link, is known as the dominant limiting factor. The range of conditions that species can tolerate and still survive is known as the range of tolerance. The range of conditions in which the population can tolerate the conditions, but because the conditions still are not optimal relatively few individuals can exist, is known as the zone of physiological stress.

(see “Abiotic Components”)

Specialist species have relatively narrow niches and are generally more susceptible to population fluctuations as a result of environmental change. Generalist species may have a very broad niche and have adapted most successfully to the new environments created by humans.

(see “Biotic Components”)

Intraspecific competition occurs among members of the same species, whereas interspecific competition occurs between different species. Both forms of competition are a result of demands for scarce resources.

(see “Competition”)

In predation, a predator species benefits at the expense of a prey Predation is a major factor in population control. Prey species have evolved many strategies to avoid being transferred along the food chain, including physical and chemical defenses and avoidance strategies. Parasitism is a special kind of predator–prey relationship where the predator lives on or in its prey (or host).

(see “Biotic Relationships”)

The optimal foraging theory recognizes that there is a point of compensation between the benefit of obtaining the prey and the costs of doing so and that the predator’s behaviour adjusts to optimize the benefits. Optimal foraging theory also suggests that as one type of prey becomes scarce, most predators will switch prey if they can.

(see “Biotic Relationships”)

The three forms of biodiversity are genetic diversity, species diversity, and ecosystem diversity.

(see “Biodiversity”)

The competitive exclusion principle tells us that no two species can occupy the same niche in the same area. Most species have a fundamental niche, representing the potential range of conditions that they can occupy, as well as a narrower realized niche, representing the range actually occupied. The physical conditions for growth exist throughout the fundamental niche, but the species may be out-competed in parts of this area through the overlapping requirements of other species.

(see “Biotic Components”)