1. Show pictures of members of the same species (e.g. a flock of birds, a school of fish, a pack of wolves) and discuss intraspecific competition.

2. Show a picture of Charles Darwin and be sure to include his critical observation that organisms are in competition for limited resources.

1. To distinguish a range from a habitat, show two maps with the same ranges delineated (e.g. from two Petersen field guides for different animals, such as birds and mammals) and discuss how the birds and mammals that live there occupy different habitats in the same range.

2. Figure 26.1 shows dispersal patterns.

3. Figure 26.3 shows how the same area can be either fine-grained (for a bird) or course-grained (for a slug).

4. Figure 26.4 shows a mechanism for uniform plant dispersal.

5. Figure 26.5 shows migrating birds and how dispersion can change with time.

6. Show pictures of an island shore covered with sea lions, to illustrate density.

1. Figure 26.6 shows an exponential growth curve.

2. Show and explain the equations related to growth rate and death rate.

1. Figure 26.8 shows changes over time in the size of a grasshopper population, which reaches a peak and a stable size each year.

1. Figure 26.9 shows how a population fluctuates around equilibrium level, and illustrates that all populations are limited in size.

2. Show a photograph of very crowded streets in China and India, two of the most at-risk areas for human population crash.

1. Show dissected owl pellets and the quantitative results from an owl pellet study, which illustrate changes in a population that are affected by predator-prey interactions.

2. Show pictures of deer, cattle, and wolves and discuss the Grand Canyon experiment carried out by Harrison, Smith, and Slobodkin.

1. Figure 26.10 shows how density affects population growth.

1. Show Figure 26.11 and discuss how fecundity is related to density.

2. Figure 26.12 shows how stresses limit the density of flour beetles.

3. Show photos of insects or other organisms that commonly produce pheromones, and discuss the signaling that occurs among members of a population.

1. Figure 26.14 is a schematic illustrating the distribution of animals in two habitats with differences in richness for some resource; this might be coupled with other drawings showing how the animals are redistributed over time as the resource availability changes.

2. Figure 26.15 illustrates fish managing their own distribution in a fish tank.

1. Figure 26.16 shows how territory numbers tend to remain constant and how they affect the allocation of resources.

2. Figure 26.17 illustrates a study on territories and shows that territory size may be determined based on daily energy requirements.

1. Show Figure 26.18 in discussing the three ideal survivorship curves.

1. Figure 26.19 shows the growth curve of the human species; the population explosion in the last thousand years is remarkable.

2. Figure 26.20 shows how more stable populations have rectangular age-structure graphs; contrast the graphs for less stable populations.

3. A graph of the logistical growth equation (Figure 26.9), is described as sigmoid or S-shaped, and it levels off at K.

1. He surmised that group selection favors populations that develop mechanisms to keep their sizes within the limits of their resources.

2. He defined group selection as competition between groups; individual selection results from competition between individuals.

3. Most population biologists give this hypothesis little credence do to the fact that it doesn't consider "cheaters" that might be defined as mutants.

1. populations can be limited by random catastrophes such as weather,

2. populations can be limited by limited resources,

3. populations can be limited by predators, where predation is defined most broadly to include herbivory (herbivores eating phototrophs).

1. Many populations reach a limit because their members are competing for limited resources.

2. Competition takes the form of either exploitation or interference.

3. An example of exploitation of resources would be when each member of a population exploits the supply of food maximally and independently. The result is that some members of the population get less food than they need.

4. In animal species where males compete actively for females, two males engaged in combat are obviously interfering with each other.

5. Intraspecific competition for resources ultimately affects the ability of individuals to survive and to reproduce.

1. In 1960, Nelson Hairston and his associates argued that herbivores are not food-limited, since there is plenty of food available; they are not catastrophe-limited, so they must be limited by predation.

2. This group also argued that carnivores are food-limited, because there are no predators above them to limit their populations.

3. They added that decomposers are food-limited because, by definition, they are the organisms that consume organic debris.

1. Density-independent factors affect large and small concentrations of organisms equally.

2. Density-dependent factors affect a crowded population much more than a sparse one.

1. Food is the most obvious resource that may reduce survival and fecundity.

2. As crowded individuals find it harder to get adequate nourishment, they may die before they can mature and reproduce, or they may produce fewer, less viable offspring (Figure 26.11).

1. Dense populations impose stresses on their members.

2. Classical experiments by R. N. Chapman and by Thomas Park on flour beetles (Tribolium confusum; Figure 26.12) show how these stresses can limit population density.

3. Park showed that male flour beetles release the pheromone ethylquinone when another beetle interrupts them during mating.

4. Park also showed that egg-laying in flour beetles is inhibited by the presence of ethylquinone. Thus, ethylquinone acts as a population control device.

1. The stress syndrome, first described by Hans Selye, holds that often the factors that produce stress (injury, fear, anxiety, overcrowding) often activate the adrenal glands to produce hormones.

2. One hormonal effect is to inhibit the infammatory reaction that fights infections, making animals under stress more susceptible to disease.

3. Stress inhibits the growth of reproductive organs.

1. The Principle of Allocation says that an organism may allocate its energy in various ways, but by allocating more energy to one activity, it reduces the energy available for others.

2. An individual organism does not necessarily actually make allocation decisions, but rather follows the strategy of growth and reproduction inherent in its genome.

1. An ideal free distribution is the distribution of organisms who are free to optimize their access to resources, and their densities in the areas will be proportional to the relative richness of the areas (Figure 26.15).

1. Territoriality means claiming an area for one's own and defending it actively, rather than simply roaming freely through a habitat.

2. When animals defend a territory, they retain control over a set of resources, and territoriality is one way of limiting the number of individuals who try to share those resources.

3. Generally, individuals without a territory do not breed. This leads to relatively stable numbers of individuals inhabiting each territory year after year (Figure 26.16).