1. A small population is more likely to become extinct because random events are more likely to adversely affect a population of only a few individuals. Inbreeding leads to direct loss of genetic vigor and loss of variability affects the ability to adjust to changing conditions, therefore increasing the possibility of extinction.
2. The three types of dispersion are random spacing, even spacing, and clumping. The most frequent in nature is clumping because specific environmental conditions are neither randomly nor evenly distributed. Animals often congregate for various reasons, and the young of a species are likely to be near the parents.
3. The biotic potential of a population is the rate at which a given population will increase with no limits placed on it. The actual rate of population increase is the difference between birth rate and death rate per individuals per time. Two factors that affect it are emigration and immigration.
4. An exponential capacity for growth means that the rate of increase remains constant while the actual increase in numbers accelerates rapidly as the population size grows. This type of growth typically occurs when a species expands into a new habitat, such as the introduction of bacteria into a fresh medium.
5. Carrying capacity is the number of individuals that can be supported in a habitat indefinitely. This tends to be a dynamic measure, as environmental characteristics are also dynamic.
6. Density-dependent factors are those in which the resources are in short supply, causing the individuals to compete more intensely as the population grows. Density-independent factors are those caused by factors that operate regardless of population size (i.e., weather and physical disruption).
7. Partway up the sigmoid growth curve reflects a rapid growth phase, and yields will therefore be better longer, extending the period of rapid growth. Harvesting small populations results in overharvesting, destroys long-term productivity, and increases the likelihood of extinction.
8. A K strategist exhibits a sigmoid growth curve, and the limiting factor is K, the carrying capacity. These types of organisms reproduce late and have long generation times. They have few, large offspring and provide lengthy parental care; their offspring mature slowly. An r strategist exhibits an exponential growth curve, and the limiting factor is r, the intrinsic rate of increase. These types reproduce early and have short generation times. They have many, small offspring and provide little parental care; their offspring mature rapidly.
9. Interspecific competition is competition among different species. Intraspecific competition is competition among individuals of a single species. Gause's principle essentially states that no two species can occupy the same niche.
10. Survivorship is the percentage of an original population that survives to a given age. The three types are I-large proportion of individuals reach their physiologically determined maximum age and the greatest mortality is in the aged; II-mortality constant through all ages; and III-mortality especially high in the young stages and declines with age. Examples are as follows: I, humans; II, hydra; III, oysters.
11. Demography is the statistical study of populations, which involves predicting the ways in which populations will change in the future. The two factors taken into account in demographic studies are age distribution of the population and changing population size through time. The characteristics of a stable population are births plus immigration equals deaths plus emigration, and population size and age structure remain constant.
12. Predation contributes to the elimination of the sick, weak, and genetically inferior members of prey populations.
13. The terms niche and habitat are not synonymous. The habitat is part of the niche, but only the physical part; an organism's niche additionally includes behavior, seasonal factors, and daily patterns. The theoretical niche is the potential niche if there were no competitors present, and the actual niche is what the organism occupies under natural circumstances.
14. Under these circumstances, the niche widens. If the species become different enough to have different niches, there is no exclusion; if they are not different enough, additional selection will occur or one will become excluded.