CHAPTER 50 AN INTRODUCTION TO ECOLOGY AND THE BIOSPERE Section A: The Scope of Ecology 1. The interaction between organisms and their environments determine the distribution and abundance of organisms 2. Ecology and evolutionary biology are closely related sciences 3. Ecological research ranges from the adaptations of individual organisms to the dynamics of the biosphere 4. Ecology provides a scientific context for evaluating environmental issues Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The environment of any organism includes the following components: Ecology is the scientific study of the interactions between organisms and their environment. Ecologists make predictions of what should be observed in the environment. The environment of any organism includes the following components: Abiotic factors: non-living chemical and physical factors such as temperature, light, water, and nutrients Biotic factors: the living components Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Events that occur in the framework of ecological time (minutes, months, years) translate into effects over the longer scale of evolutionary time (decades, centuries, millennia, and longer). Population: a population is a group of individuals of the same species living in a particular geographic area. Population ecology examines factors that affect population size and composition. Community: community consists of all the organisms of all the species that inhabit a particular area. Community ecology examines the interactions between populations, and how factors such as predation, competition, and disease affect community structure and organization.

Ecosystem: an ecosystem consists of all the abiotic factors in addition to the entire community of species that exist in a certain area. Ecosystem ecology examines the energy flow and cycling of chemicals among the various abiotic and biotic components. Landscape ecology deals with the array of ecosystems and their arrangement in a geographic region. A landscape or seascape consists of several different ecosystems linked by exchanges of energy, materials, and organisms. This could also have been referred to this as a biome by some authors, e.g. the boreal forest biome.

Ecologists have long recognized distinct global and regional patterns in the distribution of organisms. Fig. 50.4 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Annual means for temperature and rainfall are reasonably well correlated with the biomes we find in different regions). Fig. 50.10 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Ponds and lakes are sensitive to seasonal temperature change. Turnover brings oxygenated water from the surface of lakes to the bottom and nutrient-rich water to the top. Fig. 50.15 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Zonation in Marine communities. Freshwater biomes (ponds and lakes, small and large freshwater). The littoral zone is shallow and close to shore. The limnetic zone is the open surface water. The profundal zone consists of the deep, aphotic regions. Zonation in Marine communities. The intertidal zone is where the landmeets the water. The neritic zone includes the shallow regions over the continental shelves. The oceanic zone extends past the continental shelves, and can be very deep. The pelagic zone is the open water. The benthic zone is the seafloor. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 50.17 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 50.26 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Ecologists ask a series of questions to determine what limits the geographical distribution of any species. Biogeography is the study of past and present distributions of individual species, which provides a good starting point to understanding what limits geographic distributions. Fig. 50.5 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Species dispersal contributes to the distribution of organisms Dispersal can be a factor in limiting distribution. An analysis of accidentally or intentionally transplanted species to areas where it was previously absent demonstrate this. The African honeybee and Zebra mussel are good examples of this explosion. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Abiotic factors affect the distribution of organisms Temperature: some organisms can only tolerate specific ranges of temperature. Water: some organisms can only tolerate either fresh or salt water. Sunlight provides energy that drives nearly all ecosystems. The intensity and quality of light, and photoperiod can be important to the development and behavior of many organisms. Wind amplifies the effects of temperature by increasing heat and water loss (wind-chill factor). Rocks and soil: the physical structure and mineral composition of soils and rocks limit distribution of plants and the animals that feed upon them. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The ecological niche of an organism depends not only on where it lives but also on what it does. By analogy, it may be said that the habitat is the organism's "address", and the niche is its "profession", biologically speaking. Odum - Fundamentals of Ecology - W B Saunders 1959 The fundamental niche is the "set of resources and physical factors required for survival and reproduction of individuals of a species" and the realized niche is the "set of resources and physical habitats actually used by individuals of a species in an area " http://notes.utk.edu/bio/greenberg.nsf/0/cb2581ecfdd46749852568e9004bebf2?OpenDocument Niche construction is the process whereby organisms, through their activities and choices, modify their own and each other's niches. http://www.st-andrews.ac.uk/~seal/niche/

The cultural trait of dairy farming is thought to have evolved in association with the gene for lactose absorption (Figures12). http://www.st-andrews.ac.uk/~seal/niche/nicheconstruction5.html

CHAPTER 52 POPULATION ECOLOGY Characteristics of Populations A population is a group of individuals of a single species that occupy the same general area. 1. Two important characteristics of any population are density and the spacing of individuals Demography is the study of factors that affect the growth and decline of populations Populations have size and geographical boundaries. The density of a population is the number of individuals per unit area. The dispersion of a population is the pattern of spacing among individuals within the geographic boundaries. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Uniform dispersion is when individuals are evenly spaced. Clumped dispersion is when individuals aggregate in patches. Random dispersion is the position of each individual is independent of the others. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Life tables and survivorship curves. Demography studies the vital statistics that affect population size such as births and deaths. Life tables and survivorship curves. A life table is an age-specific summary of the survival pattern of a population. The best way to construct life table is to follow a cohort, a group of individuals of the same age throughout their lifetime. Table 52.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Type I curve shows a low death rate early in life (humans). Survivorship curves. Type I curve shows a low death rate early in life (humans). Type II curve shows constant mortality (squirrels). Type III curve shows a high death rate early in life (oysters). Fig. 52.3 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Other organisms reproduce once semelparity. Table 52.2 Some organisms have repeated reproductive episodes and this is known as iteroparity. Other organisms reproduce once semelparity. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Population Growth 1. The exponential model of population growth describes an idealized population in an unlimited environment The logistic model of population growth incorporates the concept of carrying capacity If N represents population size, and t represents time, then N is the change is population size and t represents the change in time, then: N/t = B-D Where B is the number of births and D is the number of deaths We can simplify the equation and use r to represent the difference in per capita birth and death rates. N/t = rN OR dN/dt = rN If B = D then there is zero population growth (ZPG). Exponential population growth is said to be happening Under these conditions, we may assume the maximum growth rate for the population (rmax) to give us the following exponential growth dN/dt = rmaxN

dN/dt = rmaxN((K-N)/K)

The life history traits that natural selection favors may vary with population density and environmental conditions. In K-selection, organisms live and reproduce around K, and are sensitive to population density. In r-selection, organisms exhibit high rates of reproduction and occur in variable environments in which population densities fluctuate well below K.

This is a type of negative feedback. Density-dependent factors increase their affect on a population as population density increases. This is a type of negative feedback. Density-independent factors are unrelated to population density, and there is no feedback to slow population growth. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Population dynamics reflect a complex interaction of biotic and abiotic influences Carrying capacity can vary, thus population data should be acquired over several years. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Behavior and Behavioral Ecology Proximate questions are mechanistic, concerned with the environmental stimuli that trigger a behavior, as well as the genetic and physiological mechanisms underlying a behavioral act. Ultimate questions address the evolutionary significance for a behavior and why natural selection favors this behavior. Behavioral ecology is the research field that views behavior as an evolutionary adaptation to the natural ecological conditions of animals. Behavior results from both genes and environmental factors Innate behavior is developmentally fixed Learning is the modification of behavior resulting from specific experiences.

Migration Behavior. Migration is the regular movement of animals over relatively long distances. Piloting: an animal moves from one familiar landmark to another until it reaches its destination. Fig. 51.15 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

CHAPTER 53 COMMUNITY ECOLOGY Section A: What Is a Community? Contrasting views of communities are rooted in the individualistic and interactive hypotheses A community is defined as an assemblage of species living close enough together for potential interaction Communities differ in their species richness, the number of species they contain, and the relative abundance of different species. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

There are different interspecific interactions, relationships between the species of a community Populations maybe linked by competition, predation, mutualism, and commensalism Community biodiversity measures the number of species and their relative abundance

Competition. Interspecific competition for resources can occur when resources are in short supply. There is potential for competition between any two species that need the same limited resource. The competitive exclusion principle: two species with similar needs for same limiting resources cannot coexist in the same place. The ecological niche is the sum total of an organism’s use of abiotic/biotic resources in the environment. An organism’s niche is its role in the environment. The competitive exclusion principle can be restated to say that two species cannot coexist in a community if their niches are identical. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Character displacement Resource partitioning is the differentiation of niches that enables two similar species to coexist in a community. Fig. 53.3 Character displacement Fig. 53.2 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The trophic structure of a community is determined by the feeding relationships between organisms. The transfer of food energy from its source in photosynthetic organisms through herbivores and carnivores is called the food chain. Food web or who eats whom

If they are removed, community structure is greatly affected. Keystone species exert an important regulating effect on other species in a community. If they are removed, community structure is greatly affected. Fig. 53.15 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The structure of a community may be controlled bottom-up by nutrients or top-down by predators. Simplified models based on relationships between adjacent trophic levels are useful for discussing how communities might be organized Consider three possible relationships between plants (V for vegetation) and herbivores (H). V  H V  H V  H Arrows indicate that a change in biomass of one trophic level causes a change in the other trophic level. The bottom-up model postulates V  H linkages, where nutrients and vegetation control community organization. The top-down model postulates that it is mainly predation that controls community organization V  H. Other models go between the bottom-up and top-down extreme models. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Ecological succession is the sequence of community changes after a disturbance Ecological succession is the transition in species composition over ecological time. Primary succession begins in a lifeless area where soil has not yet formed. Secondary succession Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 53.20 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The composition of a community has two components. Species richness, the total number of species in the community. Relative abundance of the different species. Species richness may be equal, but relative abundance may be different.

The species-area curve quantifies what may seem obvious: the larger the geographic area, the greater the number of species.

Species richness on islands depends on island size and distance from the mainland Because of their size and isolation, islands provide great opportunities for studying some of the biogeographic factors that affect the species diversity of communities. Imagine a newly formed island some distance from the mainland. Robert MacArthur and E. O. Wilson developed a hypothesis of island biogeography to identify the determinants of species diversity on an island. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Two factors will determine the number of species that eventually inhabit the island. The rate at which new species immigrate to the island. The rate at which species become extinct. Fig. 53.26 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Studies of plants on many island chains confirm their hypothesis. Galapagos Islands Fig. 53.27 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The Ecosystem Approach to Ecology ECOSYSTEMS The Ecosystem Approach to Ecology 1. Trophic relationships determine the routes of energy flows and chemical cycling in an ecosystem 2. Decomposition connects all trophic levels 3. The laws of physics and chemistry apply to ecosystems An ecosystem consists of all the organisms living in a community as well as all the abiotic factors with which they interact. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Total primary production is known as gross primary production (GPP). The net primary production (NPP) is gross primary production minus the energy used for respiration (R) by primary producers:

The human population is disrupting chemical cycles throughout the biosphere