chapter 6Review
Community ecology examines how species interactions help to determine the species that are present in a community. Different characteristics of populations affect their abundance and distribution including density-
Population Community Population ecology Population size (N) Population density Population distribution Sex ratio Age structure Limiting resource Density-dependent factor Carrying capacity (K) Density-independent factor Population growth model Population growth rate Intrinsic growth rate (r) Exponential growth model (Nt = N0ert) J-shaped curve Logistic growth model S-shaped curve Overshoot Die-off K-selected species r-selected species Survivorship curve Type I survivorship curve Type II survivorship curve Type III survivorship curve Corridor Metapopulation Inbreeding depression Community ecology Symbiotic relationship Competition Competitive exclusion principle Resource partitioning Predation Parasitoid Parasitism Pathogen Herbivory Mutualism Commensalism Keystone species Ecosystem engineer Ecological succession Primary succession Secondary succession Pioneer species Theory of island biogeography | An interaction in which one organism lives on or in another organism. The curve of the exponential growth model when graphed. When individuals with similar genotypes—typically relatives—breed with each other and produce offspring that have an impaired ability to survive and reproduce. A description of how many individuals fit into particular age categories in a population. A specialized type of predator that lays eggs inside other organisms—referred to as its host. A species that can colonize new areas rapidly and grow well in full sunshine. The study of interactions between species. The shape of the logistic growth model when graphed. A factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of the population. Ecological succession occurring on surfaces that are initially devoid of soil. The number of individuals per unit area at a given time. A relationship between species in which one species benefits and the other species is neither harmed nor helped. The struggle of individuals to obtain a shared limiting resource. A theory that demonstrates the dual importance of habitat size and distance in determining species richness. A graph that represents the distinct patterns of species survival as a function of age. An interaction between two species that increases the chances of survival or reproduction for both species. An interaction in which one animal typically kills and consumes another animal. A pattern of survival over time in which there is high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age. A pattern of survival over time in which there is low survivorship early in life with few individuals reaching adulthood. A factor that has the same effect on an individual’s probability of survival and the amount of reproduction at any population size. The principle stating that two species competing for the same limiting resource cannot coexist. The total number of individuals within a defined area at a given time. The maximum potential for growth of a population under ideal conditions with unlimited resources. A species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity. The number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period. A species that plays a far more important role in its community than its relative abundance might suggest. A description of how individuals are distributed with respect to one another. The relationship between two species that live in close association with each other. A species that has a high intrinsic growth rate, which often leads to population overshoots and die-offs. The predictable replacement of one group of species by another group of species over time. Strips of natural habitat that connect populations. A keystone species that creates or maintains habitat for other species. An interaction in which an animal consumes a producer. The limit of how many individuals in a population the environment can sustain. A parasite that causes disease in its host. A pattern of survival over time in which there is a relatively constant decline in survivorship throughout most of the life span. When a population becomes larger than the environment’s carrying capacity. Mathematical equations that can be used to predict population size at any moment in time. A group of spatially distinct populations that are connected by occasional movements of individuals between them. A resource that a population cannot live without and that occurs in quantities lower than the population would require to increase in size. All of the populations of organisms within a given area. A rapid decline in a population due to death. The study of factors that cause populations to increase or decrease. When two species divide a resource based on differences in their behavior or morphology. A growth model that estimates a population’s future size (Nt ) after a period of time (t), based on the intrinsic growth rate (r) and the number of reproducing individuals currently in the population (N0). The succession of plant life that occurs in areas that have been disturbed but have not lost their soil. The ratio of males to females in a population. The individuals that belong to the same species and live in a given area at a particular time. A growth model that describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment. |
Module 18 The Abundance and Distribution of Populations
Explain how nature exists at several levels of complexity.
Nature exists at several levels of complexity: individuals, populations, communities, ecosystems, and the biosphere.
Discuss the characteristics of populations.
Populations can have distinct population sizes, densities, distributions, sex ratios, and age structures.
Contrast the effects of density-
Density-
Module 19 Population Growth Models
Explain the exponential growth model of populations, which produces a J-
The exponential growth model describes rapid growth under ideal conditions when resources are not limited. The J-
Describe how the logistic growth model incorporates a carrying capacity and produces an S-
The logistic growth model incorporates density-
Compare the reproductive strategies and survivorship curves of different species.
Organisms have a range of reproductive patterns. At the extremes are r-
Explain the dynamics that occur in metapopulations.
Metapopulations are groups of spatially distinct populations that are connected by occasional movements of individuals. These movements reduce the probability of any of the populations going extinct.
Module 20 Community Ecology
Identify species interactions that cause negative effects on one or both species.
Competition is an interaction between two species that share a limiting resource. Over time, competition for a resource can cause natural selection to favor those individuals that have reduced overlap in resource use and this can lead to spatial, temporal, or morphological resource partitioning. Predation is an interaction in which animals partially or entirely consume another animal. Predators can affect the abundance of prey populations and cause the evolution of antipredator defenses in prey populations. Parasitism is an interaction in which one organism lives on or in another organism. Those parasites that can cause disease in their hosts are known as pathogens. Herbivory is an interaction in which animals consume producers. In some cases, herbivores can have dramatic effects on plant and algal communities by removing the most palatable species.
Discuss species interactions that cause neutral or positive effects on both species.
Mutualisms are interactions that benefit two interacting species by increasing the chances of survival or reproduction for both. One of the most common mutualisms is the interaction between flowering plants and their pollinators. A second well-
Explain the role of keystone species.
Keystone species play a role in the community that is far more important than its relative abundance might suggest. Common examples include predators that alter the outcome of competition in intertidal communities and beavers that create large ponds by constructing dams on streams.
Module 21 Community Succession
Explain the process of primary succession.
Primary succession occurs on surfaces that are initially devoid of soil, such as bare rock that is exposed after the retreat of glaciers or the cooled lava from a volcanic eruption. Over time, plants and animals arrive at the site and modify the environment, making it more favorable for other species to arrive and persist.
Explain the process of secondary succession.
Secondary succession occurs in areas that have been disturbed but have not lost their soil. A common example is the bare soil left behind when farmers stop planting crops in a field. Over time, plants and animals colonize the site, alter the environmental conditions, and favor the persistence of other species.
Explain the process of aquatic succession.
Lakes and ponds experience sedimentation over long periods of time and this slowly fills in the basin. Over thousands of years, the lakes and ponds can be slowly converted into terrestrial habitats.
Describe the factors that determine the species richness of a community.
The species richness of a community is typically higher at latitudes that are closer to the equator. Richness is also higher in older sites where evolution has been producing new species for longer periods of time. Finally, more species exist in larger habitats and habitats that are closer to sources of new species, as is the case for oceanic islands that are located close to continents.