Summer Texbook Reading Notes

Michael Zhuang Chapter 50 - An Introduction to Ecology and the Biosphere Concept 50.1 - Ecology is the scientific study of interactions between organisms and the environment •

Interactions may include the distribution of organisms and their abundance

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Three main questions: 1) Where do they live? 2) Why do they live there? 3) How many are there?

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The Biosphere is the entire portion of Earth that is inhabited by life.

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Tropical forests are especially rich in life. Most microbial species are unknown to scientists.

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Ecology is both a descriptive science and a very rigorous experimental science.

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Ecologists have been challenged to create accurate and consistent results from field experiments.

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Ecological Time = [Minutes, Months, Years] Evolutionary Time = [Decades, Centuries, Millennia, Longer]

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Ecology and evolutionary biology are closely related, because the evolution of an organism closely relies on its environment. " For example, hawks feeding on field mice kill certain individuals (over ecological time), reducing population size (an ecological effect), altering the gene pool (an evolutionary effect), and selecting for mice with fur color that camouflages them in their environment (over evolutionary time)." (Page 1081) •

Abiotic Environment -The environment of any organism that is nonliving (temperature, light, water)

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Biotic/Biota - All living organisms in a certain organism's environment. (Act as prey, predator, parasite, effect abiotic environment)

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Two common ecological questions. What limits distribution of organism, and what determines abundance?

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Organismal Ecology - How an organism's structure, physiology, and behavior me the challenges of environment.

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Population - Group of individuals of the same species populating the same area

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Population Ecology - Studies how individuals of a particular species live in an area

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Community - All the organisms of all the species that inhabit a particular area

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Michael Zhuang Community Ecology - Studies how the interactions between species in a community (competition, disease, abiotic) affects the community structure and organization.

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Ecosystem - All the abiotic factors in addition to the entire community of species that exist in a certain area.

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Ecosystem Ecology - Emphasizes on the energy flow and chemical cycling that occurs between various biotic and abiotic components.

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Landscape ecological research focuses on the factors controlling exchanges of energy, materials, and organisms among ecosystem patches.

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Patchiness - Localized variation of environmental conditions within an ecosystem, arranged spatially into a complex of discrete areas that may be characterized by distinctive groups of species or ecosystem processes.

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Biosphere - The whole world and its ecosystems. Studies include that of climate changes (CO2).

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Precautionary Principle - "An ounce of prevention is worth a pound of cure."

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Ecology provides a scientific context for evaluating environmental issues.

Concept 50.2 - Interactions between organisms and the environment limit the distribution of species • Biogeography is the study of past and present distributions of individual species in the context of evolutionary theory. • Biogeographic Realms - Areas with distinct global and regional patterns in climate and geography that came about from the separation of Pangaea. Concept 50.2 - Interactions between organisms and the environment limit the distribution of species

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Dispersal - The movement of individuals away from centers of high population density or from their origin. Dispersal can limit distribution if there are physical barriers that prevent animals from spreading. 2

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Potential Range is where an animal can survive and reproduce. Some organisms (plants, anopheline mosquitoes, European Corn Borers) choose where they produce offspring. • Biotic factors (other species) can limit distribution like predators and herbivores or the absence of pollinators. • Abiotic factors that limit distribution can include temperature, water, sunlight, wind, and rocks and soil. • Climate is the prevailing weather conditions in a particular area. • Macroclimate - Patterns on a global, regional, and local level • Microclimate - Very fine patterns, such as those encountered by a community of organisms living under a log. • The sun's heat and light have the largest effects on the earth's climate. • Bodies of water affect the world's climate by heating and cooling the overlying air, which affects weather. • Mountains can affect the local temperature, amount of sunlight reaching an area, and the amount of rainfall. • The angle that the sun strikes the earth causes many seasonal changes on earth. • One way to predict future global climate change is to look back at the changes that occurred previously • The American beach will have shorter ranges in the future due to erosion. Concept 50.3 - Abiotic and biotic factors influence the structure and dynamics of aquatic biomes • Biomes are major types of ecological associations that occupy broad geographic regions of land or water. • Aquatic biomes (fresh and salt water) account for the largest portion of the biosphere. (Oceans cover 75%) • Aquatic biomes are separated into zones and layers determined by the depth and light penetration. • Photic zone is at the top (with sunlight), aphotic zone is below that (with little sunlight), and the benthic zone is the substrate that is made up of sand and sediments and the organisms living there are called benthos. Concept 50.4 - Climate largely determines the distribution and structure of terrestrial biomes • Climate is important in determining why certain terrestrial biomes are found in certain areas • Climographs, a plot of the temperature and precipitation in a particular region, are good for seeing the impact of climate on distribution. • Terrestrial biome are commonly named for their predominant vegetation, and have organisms adapted to that particular environment. • Many terrestrial biomes are separated vertically into strata, like forests, which have layers like canopies and forest floors. • The ecotone is the area of integration between multiple biomes. • Biomes are dynamic, so there are more commonly periods of disturbance than periods of stability.

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Chapter 51 - Behavioral Ecology Modern behavioral ecology studies how behaviors are controlled and how they develop, evolve, and contribute to survival and reproductive success. Concept 51.1 - Behavioral ecologists distinguish between proximate and ultimate causes of behavior Questions about behavior either focus on the immediate stimulus and mechanism for the behavior or explore how the behavior contributes to the survival and reproduction of the organism. Behavior is everything an animal does (muscular and non-muscular) and how it does it. Proximate questions about behavior focus on environmental stimuli that cause a certain behavior, along with genetic, physiological, and anatomical causes. Ultimate questions focus on the evolutionary significance of a behavior. Ethology - the scientific study of how animals behave, particularly in their natural environments. In 1963, Niko Tinbergen suggested four questions that must be answered to fully understand any behavior. 1. What is the mechanistic basis of the behavior, including chemical, anatomical, and physiological mechanisms? 2. How does development of the animal, from zygote to mature individual, influence the behavior? 3. What is the evolutionary history of the behavior? 4. How does the behavior contribute to survival and reproduction (fitness)? Fixed Action Pattern (FAP) - A sequence of unlearned and innate behaviors that are unchangeable and are usually carried to completion once initiated. A FAP is triggered by an external sensory stimulus called a sign stimulus. Imprinting is a type of behavior that includes both learning and innate components and is generally irreversible. There is a sensitive period in an animal's development when imprinting is most successful. Can't teach an old dog new tricks. Concept 51.2 - Many behaviors have a strong genetic component Innate behaviors are strongly influenced by an organism's genotype. Directed movements are animal movements that have genetic influences. A kinesis is a simple change in activity or turning rate in response to a stimulus. Taxis is a more or less automatic, oriented movement toward or away from a stimulus Many migratory behaviors in birds are genetically programmed. Others are imprinted at a young age. Signal - behavior that causes a change in another animal's behavior Communication - the reception of and response to signals Animals communicate using odors, visual, chemical, tactile, electrical, and auditory signals (adapted for environment) Concept 51.3 - Environment, interacting with an animal’s genetic makeup, influences the development of behaviors Environmental factors such as quality of the diet, nature of social interactions, and opportunities for learning can influence the development of behaviors in every group of animals. Learning - the modification of certain behaviors based on experiences. 4

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Michael Zhuang Habituation is the lack of a response to stimuli that do not yield information or actions (cry-wolf effect). Spatial learning - the modification of behavior based on experience with the spatial structure of the environment, including the locations of nest sites, hazards food, and prospective mates. The fitness of an organism may be enhanced by the capacity for spatial learning. Landmarks are location indicators. Some animals use them to locate areas of interests. Cdogninitve map - an internal representation, or code, of the spatial relationships between objects in an animal's surroundings. Associative learning is the ability to associate on feature of the environment with another. Classical conditioning is when an arbitrary stimulus is associated with either an award or punishment. Operant conditioning is aka trial-and-error. Cognition is the ability of an animal's nervous system to perceive, store, process, and use information gathered by sensory receptors. The study of cognition is called cognitive ethology. It examines an animal's nervous system and its behavior. Studies how animals' brains represent objects in an environment. Cognitive skills are relatively well developed in mammals like monkeys and dolphins as well as in some birds. Genetic and environmental factors strongly influence an animal's cognitive skills. Concept 51.4 Behavioral traits can evolve by natural selection Natural selection can result in the evolution of behavioral traits in populations (since behavior is influenced by genetics, so behavior can be passed down from generation to generation). There can be behavioral differences within a species (probably due to past evolution). Foraging - behavior associated with recognizing, searching for, capturing, and consuming food Examples of change of behavior because of evolution include those of Drosophila and Blackcaps Optimal foraging theory views foraging behavior as a compromise between the benefits of nutrition and the costs of obtaining food such as energy released when capturing prey. Mating behavior is the product of a form of natural selection called sexual selection. Mating relationships can be promiscuous (no strong paring), monogamous (one mate), or polygamous (many). Polygyny (males ornamented) is one male and many females, while polyandry (females ornamented) is one female and many males. Monogamous = hard to distinguish between male and female. Sexual selection can cause competition among animals of the same sex in a species. Agonistic behavior is an often ritualized contest that determines which competitor gains access to a resource such as food or mates. Game theory is the study of strategies in situations where the outcome is determined by not only the actions an individual but also on the actions of the other competitors. 5

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Michael Zhuang Altruism - some animals behave in ways that reduce their individual fitness but increase that of another's…selflessness Inclusive fitness - the total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables other close relatives, who share many of those genes, to produce offspring. Coefficient of relatedness - the probability that if two individuals share a common parent or ancestor, a particular gene present in one individual will also be present in the second individual. B = the benefit to the recipient C = the cost to the altruist r = the probability that a particular gene present in one individual will also be inherited from a common parent or ancestor in a second individual. Hamilton's rule: rB > C The more closely related two individuals are, the greater the value of altruism. Kin selection is the form of natural selection that favors altruistic behavior by enhancing the fitness of relatives • Reciprocal altruism - altruism between unrelated animals. (common in humans and species with social groups but rare in other species) • Social learning is learning by observing others. • Culture is a system of information transfer through social learning or teaching that influences the behavior of individuals in a population. • Mate choice copying is when an individual makes a mate selection based on the mate choice of others. • Sociobiology - certain behavioral characteristics exist because they are expressions of genes that have been perpetuated by natural selection. • Sociobiology places social behavior in an evolutionary context. • Human culture is linked to evolutionary theory with sociobiology.

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Michael Zhuang Chapter 52 - Population Ecology •

Population ecology is the study of populations in relation to the environment, including environmental influences on population density and distribution.

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Concept 52.1 - Dynamic biological processes influence population density, dispersion, and demography

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A population is a group of individuals of a single species living in the same general area.

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Members of a population rely on the same resources, have a high likelihood of interacting with and breeding with one another, and are influenced by similar environmental factors.

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Populations can evolve through natural selection by changing the frequency of certain traits.

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Density and dispersion (spacing) are important characteristics of a population.

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Density is the number of individuals per unit area of volume.

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Dispersion is the pattern of spacing among individuals within the boundaries of the population.

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Population numbers are usually estimated.

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A way to estimate a density of a certain population is to count the number of individuals in a series of randomly located plots, calculate the average density in the samples, and extrapolate to estimate the population size in the entire area. This method is accurate if there are many sample plots.

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Mark-recapture method - One group of animals are captured and marked and released. Then a second group is captured that includes both marked and unmarked animals. Using the ratio between marked and unmarked animals, ecologists are able to estimate the population density.

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Immigration - influx of new individuals from other areas.

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Emigration - the movement of individuals out of a population.

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Density independent factors are unrelated to population density.

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Density dependent factors have an increased effect on a population as population density increases.

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High density usually causes high competition for resources and mates.

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A clumped dispersion (caused by available resources or behavior) is one in which individuals aggregate in patches.

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Michael Zhuang A uniform dispersion * caused by social interactions) is one in which individuals are evenly distributed

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A random dispersion is one in which the position of each individual is independent of other individuals

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Demography is the study of the vital statistics of a population and how they change over time.

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Life tables are age-specific summaries of the survival pattern of a population.

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Cohort - a group of individuals of the same age.

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Survivorship curve - a graphic way of representing the data in a life table.

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Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Examples are humans and other large mammals that produce few offspring.

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Type III curve drops sharply at the start, reflecting high death rates for the young, but flattens out as death rates decline for those few individuals that have survived past a certain age. Examples include long-lived plants, many fishes, and other animals who commonly have large groups of offspring but provide little to no care.

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Type II curves drop at a constant rate. Include some squirrels, and annual plants.

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A reproductive table is an age-specific summary of the reproductive rates in a population

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Concept 52.2 - Life history traits are products of natural selection

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Natural selection favors traits that increase an organism's fitness.

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Life history (genetic) is the traits that affect when an organism reproduces and survives.

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Big-bang reproduction/semelparity - describes species that reproduce one and then die

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Repeated reproduction/iteroparity - describes species that produce offspring repeatedly over time.

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The limited supply of resources affects when species choose to reproduce and when survival is more important.

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For example, some plants (namely weeds) produce a large number of seeds so that at least a few are guaranteed to germinate, while other plants grow a small number of very well nourished seeds so that the ones they do create have a high likelihood of surviving. Concept 52.3 - The exponential model describes population growth in an idealized, unlimited environment 8

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Michael Zhuang Important for the study of population growth in an idealized situation because it helps us understand the capacity of species for increase and the conditions that may facilitate this type of growth

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(Excluding immigration and emigration) Population growth = birth rate - death rate

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N represents population size, and t represents time, then ∆ N is the change is population size and ∆ t is the time interval.

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B = number of births and D - number of deaths

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∆ N/∆ t = B − D

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B = bN

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Exponential population growth results in a J-shaped curve. Characteristic of rebounding populations.

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Concept 52.4: The logistic growth model includes the concept of carrying capacity

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Exponential growth cannot be sustained for very long.

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Carrying capacity (K)-the maximum population size that a particular environment can support.

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Realistic population models limit growth by taking in account the effects of the carrying capacity of a certain area.

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In a Logistic population growth model - the per capita rate of increase declines as carrying capacity is reached.

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dN/dt = rmaxN*[(K-N)/K]

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Logistic model produces a sigmoid (S) curve. (like a titration curve)

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Some populations overshoot K, before some die off because of starvation or some other reasons and then density becomes stable and hovers around K.

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Logistic models rarely fit populations irl, but they are useful for estimating possible growth.

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Some life history traits can be favored by natural selection while others are not depending on the environment.

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K-selection (density-dependent selection) - selection for life history traits that are sensitive to population density.

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r-selection (density-independent selection) - selects for life history traits that maximize reproduction. 9

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K/r-selection - has been criticized for oversimplifying the matter Concept 52.5 - Populations are regulated by a complex interaction of biotic and abiotic influences

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Two questions about the regulation of population growth:  What environmental factors stop a population from growing?  Why do some populations show radical fluctuations in size over time, while others remain stable?

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Birth and death rates do not change with population density in density-independent populations.

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Birth rates fall and death rates rise with increases in population density for densitydependent populations.

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The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variation in population size.

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High levels of immigration combined with higher survival results in greater stability in populations .

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Metapopulations - groups of populations linked by immigration and emigration.

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Boom-and-bust cycles are influenced by complex interactions between biotic and abiotic factors

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Concept 52.6: Human population growth has slowed after centuries of exponential increase

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The human population increased slowly until around 1650 and then grew exponentially.

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40 years ago, the rate of growth of the human population began to slow.

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Zero population growth is either high birth and high death or low death and low birth.

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Age structure - the relative number of individuals of each age. good for predicting growth trends.

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Infant mortality is the number of death per 1000 live births.

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Life expectancy at birth is the predicted average of life at birth, which varies widely among different populations.

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A demographic transition is the move from one state to another state.

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Carrying capacity of biosphere for humans is uncertain.

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World in ecological deficit. 10

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Ecological capacity - actual resource base of each country.

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Ecological footprint - All the resources used by a nation to produce all the resources it consumes.

Chapter 53 - Community Ecology •

A biological community is an assemblage of populations of various species living close enough for potential interaction.

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Concept 53.1 - A community’s interactions include competition, predation, herbivory, symbiosis, and disease

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Interspecific interactions - Interactions between and organism with other species in a community.

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Affects the survival and reproduction of the species involved in the interactions.

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Interspecific competition (-/-) occurs when multiple species fight over limited resources.

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Competition can lead to one of the two species being eliminated in a certain area, called competition exclusion.

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Competitive exclusion principle - two species competing for same limited resources cannot coexist in same location.

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Ecological niche - the sum of a species' use of the biotic and abiotic resources in its environment.

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Ecologically similar species can coexist in a community if there is one or more significant difference in their niches

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Fundamental niche is niche potentially occupied and realized niche is the niche actually occupied in a particular environment. Can be different as a result of competition.

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Resource partitioning - differentiations of niches that enables similar species to coexist in a community.

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Character displacement - the tendency for characteristics to me more divergent in sympatric populations of two species than in allopatric populations of the same two species.

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Predation (+/-) refers to an interaction where one species, the predator, kills and eats the other, the prey.

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Cryptic coloration - aka camouflage, makes prey hard to spot. 11

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Michael Zhuang Aposematic coloration - colors used by poisonous animals to warn predators.

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Batesian mimicry - innocuous animals mimic coloration of poisonous ones to scare predators.

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Mullerian mimicry - two or more unpalatable species resemble each other

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Herbivory (+/-) interaction in which herbivores eat plants or alga

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Parasitism (+/-) symbioric interaction in which a parasite derives its nourishment from a host, which is harmed in the process.

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Endoparasites - parasites that live within the body of their hosts (e.g. tapeworms).

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Ectoparasites - parasites that feed on the external surface of a host (e.g. ticks and lice).

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Parasitoidism - insects that lay eggs on or in living hosts. Larvae then feed on body of host.

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Pathogens (+/-) are similar to parasites. Are typically bacteria, viruses, or protists.

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Mutualistic symbiosis, or mutualism (+/+) is an interspecific interaction that benefits both species involved.

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Commensalism (+/0) - an interaction between species that benefits one of the species but neither harms nor helps the other. Examples are rare because ant close association between two species is likely to affect both.

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Generalized adaptation of organisms to other organisms in their environment is a fundamental feature of life. Concept 53.2 - Dominant and keystone species exert strong controls on community structure

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In general, a small number of species in a community exert strong control on that community’s structure.

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The Species diversity of a community is the variety of different kinds of organisms that make up the community.

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One component of species diversity is species richness, the total number of different species in the community.

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A second component is relative abundance of the different species , the proportion each species represents of the total individuals in the community.

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A community with an even species abundance is more diverse than one in which one or two species are abundant and the remainder rare.

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Michael Zhuang The feeding relationships between organisms is known as the trophic structure of a community. It is a key factor in community dynamics.

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Food webs - a branching food chain with complex trophic interactions.

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Food webs can be simplified by isolating a portion of a community that interacts very little with the rest of the community.

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Energetic hypothesis - length of a food chain is limited by the inefficiency of energy transfer along the chain.

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Dynamic stability hypothesis -long food chains are less stable than short ones.

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Most data supports the energetic hypothesis.

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Some species are very important on the structure of communities because they are either large in number or because they are important to the community dynamics.

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Dominant species are those in a community that are either the most abundant or collectively have the most biomass.

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Invasive species can attain a high biomass due to the lack of natural predators and pathogens.

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Keystone species (not always high in number) exert strong control on community structure not by numeral might but by their pivotal ecological roles, or niches.

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Some organisms exert their influence by causing physical changes in the environment that affect community structure (e.g. beavers and humans).

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The bottom-up model of community organization proposes a unidirectional influence from lower to higher trophic levels

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The top-down model of community organization proposes that control comes from the trophic level above

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Communities can shift from the bottom-up model to the top-down model

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Biomanipulation - deliberate alteration of an ecosystem by adding or removing species, especially predators. Concept 53.3 - Disturbance influences species diversity and composition

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Ecologists used to believe that communities are in a state of equilibrium

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Stability - tendency of a community to reach and maintain a relatively constant composition of species in the face of disturbance.

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Nonequilibrium model - describes communities as constantly changing after being buffeted by disturbances. 13

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Michael Zhuang A disturbance is an event that changes a community by removing organisms or altering available resources.

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Fire is a significant disturbance in most ecosystems, although it can be a necessity in some communities.

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Intermediate disturbance hypothesis - suggests that moderate levels of disturbance can foster higher species diversity than low levels of disturbance.

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Humans are the most widespread cause of disturbance. Usually reduce species diversity and sometimes prevent natural disturbances like wildfires.

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Ecological succession - sequence of community and ecosystem changes after a disturbance

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Primary succession occurs where no soil exists when succession begins

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Secondary succession begins in an area where soil remains after a disturbance

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Early-arriving species can facilitate/inhibit appearance of later species.

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Retreating glaciers provide scientists with opportunities for researching succession. Concept 53.4 - Biogeographic factors affect community diversity

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Geographical location and size are correlated with a community's species diversity.

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The two key factors in equatorial-polar gradients of species richness sre probably evolutionary history and climate

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The two main climatic factors correlated with biodiversity are solar energy input and water availability

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Evapotranspiration is the evaporation of water from soil plus the transpiration of water from plants.

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Species-area curve - the larger geographically a community, the more diverse its species are. (Larger areas are more diverse)

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The equilibrium model of island biogeography -species richness on an ecological island levels off at some dynamic equilibrium point

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Concept 53.5: Contrasting views of community structure are the subject of continuing debate

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Two diff views on community structure emerged in early 20th century

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Integrated hypothesis - Describes a community as an assemblage of closely linked species, locked into association by mandatory biotic interactions. The presence or absence of a species depends on the presence or absence of other species in a community. 14

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Michael Zhuang Individualistic hypothesis - Chance Assemblage. Communities are loosely organized associations of independently distributed species with the same abiotic requirements. Species are distributed according to their tolerance ranges for abiotic factors.

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In actual cases, the composition of communities change continuously, with each species more or less independently distributed.

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Rivet model of communities - suggests that mmost of the species in a community are associated tightly with particular other species in a web of life. Also, the loss of even a single species has strong repercussions for the community.

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Redundancy model of communities - if a species disappears from a community, other species will take its place.

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Models and hypothesis are extremes. Most communities are hybrids of different models.

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Chapter 54 - Ecosystems An ecosystem consists of all the organisms living in a community as well as all the abiotic factors with which they interact. Ecosystems range from microcosms like fish tanks to large areas like lakes and rivers. Regardless of an ecosystem’s size, its dynamics involve two main processes: energy flow and chemical cycling. Energy flows through ecosystems while matter cycles within them. Concept 54.1 - Ecosystem ecology emphasizes energy flow and chemical cycling Ecosystems are transformers of energy and processors of matter . Energy is conserved as it moves through an ecosystem, but it is degraded into heat during processes. Primary producers of an ecosystem are autotrophs, most of which are photosynthetic. Primary consumers are herbivores which eat the primary producers. Secondary consumers are carnivores that eat herbivores. Tertiary consumers are carnivores that eat other carnivores. Detritivores/decomposers are consumers that get their energy from detritus, which is nonliving organic matter. Energy enters an ecosystem as light and leaves as heat. (Most organisms create organic compounds that break down into ATP. Nutrients cycle in an ecosystem. Concept 54.2: Physical and chemical factors limit primary production in ecosystems An ecosystem's primary production is the amount of light energy converted to chemical energy by autotrophs during a given time period. Organic producers use sunlight to synthesize energy-rich molecules that ultimately break down into ATP. The earth is bombarded by about 1022 joules of solar radiation every day. Only about 1% of the light that reaches plants is used for photosynthesis. Primary producers on earth produce about 170 billion tons of organic material per year. Total primary production in an ecosystem is known as that ecosystem's gross primary production (GPP). Net primary production (NPP) is equal to gross primary production minus the energy used by the primary producers for respiration (R). NPP = GPP - R Terrestrial ecosystems contribute 2/3 of global NPP, while marine ecosystems contribute 1/3. 15

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Michael Zhuang Both light (depth of light penetration) and nutrients are instrumental in controlling primary production. A limited nutrient is the element that must be added in order for production to increase in a particular area. Nitrogen and phosphorous are two common limited nutrients in marine ecosystems. Iron is also common. Temperature and moisture affect the primary production in terrestrial and wetland ecosystems. Actual evaporation is the annual amount of water transpired by plants and evaporated from the landscape, usually measured in mm. Used to show the contrast between wet and dry climates. Related to net primary production Nutrients in soil also limit primary production. (like nutrients in water) Concept 54.3 - Energy transfer between trophic levels is usually less than 20% efficient The amount of chemical energy in consumers' foods that is converted to their own new biomass during a given time period is called the secondary production of the ecosystem. For example, only 1/6 of energy from leaf eaten by a caterpillar is used for secondary production. Production efficiency = (Net secondary production)/(Assimilation of primary production) Production efficiency is the fraction of energy stored in food that is not used for respiration. Trophic efficiency - the percentage of production transferred from one trophic level to the next. Usually 5%-20% Biomass pyramids decrease from base to top as energy is lost from one trophic level to the next. Turnover time = Standing crop biomass/Production It would be easier and more efficient to feed people using plants since more energy is directly gained. According to the green world hypothesis, terrestrial herbivores consume relatively little plant biomass because they are held in check by a variety of factors, including predators, parasites, and disease. Herbivores are actually only a minor nuisance to plants (they only eat about 17% of plant biomass). The green world hypothesis proposes these factors that keep herbivores in check.  Defenses like spines and noxious chemicals protect plants from herbivores.  Some nutrients like protein that animals need are not supplied by plants.  Abiotic factors can keep herbivore populations below the carrying capacity so vegetation is not stripped.  Intra-specific competition can limit herbivore populations.  Interspecific competition like disease, predators, and parasites are the most important limiting factors based on the green world hypothesis. Concept 54.4 - Biological and geochemical processes move nutrients between organic and inorganic parts of the ecosystem

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Organic life on earth depends on the cycling and recycling of key elements and chemicals through trophic layers. (Circle of life!) Biogeochemical cycles are nutrient circuits that involve both biotic and abiotic components. Gaseous forms of carbon, oxygen, sulfur, and nitrogen cycle globally in the atmosphere. Phosphorous, potassium, and calcium cycle on a more local level. (Not gasses) 16

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Michael Zhuang A general model of nutrient cycling has elements that are in main reservoirs (organisms, minerals, atmosphere) both organic and inorganic. The elements are then transferred between these resevoirs. Water cycles globally with the force of solar energy. The carbon cycle reflects the reciprocal processes of photosynthesis and cellular respiration Four important factors that ecologists consider as they research biogeochemical cycles:  The biological importance of each chemical  The forms in which each chemical is available for use  The major repositories or resevoirs for each chemical  The key processes that drive the movement of each chemical through its biogeochemical cycle Nitrogen cycles locally between animals, soil, and water. Phosphorus also cycles relatively locally. Detritivores (decomposers) play a key role in breaking down dead organisms into simple molecules and elements. Differences in rates of decomposition lead to varied speeds at which nutrients cycle through a system. Vegetation also regulates nutrient cycling. Long-term ecological research projects like the Hubbard Brook Experiment monitor ecosystem dynamics over relatively long periods of time. The results of the Hubbard Brook Experiment showed how human activity can affect ecosystems Concept 54.5 - The human population is disrupting chemical cycles throughout the biosphere Human population growth has caused disturbances in trophic structure, energy flow, and chemical cycling of ecosystems in most parts of the world. Humans have added entirely new materials like nutrients and toxins, to ecosystems. Agriculture removes nutrients from ecosystems. Nitrogen is the main nutrient that is lost. Fertilizer is used to replace nitrogen, but it can often have detrimental effects on an ecosystem. The critical load for a nutrient is the amount of that nutrient that can be absorbed by plants in an ecosystem without damaging it. Excess nutrients can contaminate freshwater and groundwater ecosystems. Sewage runoff causes eutrophication, excessive algal growth, in freshwater ecosystems. Combustion of fossil fuels causes acid rain. One of the reasons such toxins are so harmful is that they become more concentrated in successive trophic levels of a food web In biological magnification, toxins concentrate at higher trophic levels because biomass tends to be lower at higher trophic levels. Harmful materials and chemicals can stay in ecosystems for long times and cause continual harm. One big problem caused by humans is rising levels of carbon dioxide in atmosphere. (IT’S A MYTH!) The greenhouse effect is necessary to keep the surface of the Earth at a habitable temperature. The earth's ozone protects us from harmful UV radiation. Satellite studies of the atmosphere suggest that the ozone layer has been gradually thinning since 1975. 17

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Michael Zhuang Chapter 55 - Conservation Biology and Restoration Ecology Conservation biology integrates ecology, physiology, molecular biology, genetics, and evolutionary biology to conserve biological diversity at all levels. Restoration ecology applies ecological principles in an effort to return degraded ecosystems to conditions as similar as possible to their natural state Tropical forests, which contain some of the greatest concentrations of different species, are being destroyed. Humans are altering ecosystems that both humans and animals depend upon. Concept 55.1 - Human activities threaten Earth’s biodiversity Rates of species extinction are difficult to determine under natural conditions The current rate of species extinction is high and is largely a result of ecosystem degradation by humans Humans are threatening Earth’s biodiversity Biodiversity has three main components: genetic diversity, species diversity, and ecosystem diversity. Genetic diversity is made up of genetic variation in and within populations. Species diversity is the variety of species in an ecosystem or throughout the biosphere. An endangered species is one that is in danger of becoming extinct throughout its range. Threatened species are those that are considered likely to become endangered in the foreseeable future. Hundred Heartbeat Club - species that number fewer than 100 individuals and are only that many heartbeats from extinction. Ecosystem diversity, which identifies the variety of ecosystems in the biosphere, is being affected by human activity. Human biophilia allows us to realize that species diversity is beneficial for our own sake. Many pharmaceuticals are derived from plants. Ecosystem services encompass all the processes through which natural ecosystems and the species they contain help sustain human life on Earth. They include purification of air and water, reduction of the severity of droughts and floods, generation and preservation of fertile soils, detoxification and decomposition of wastes, pollination of crops and natural vegetation, dispersal of seeds, cycling nutrients, moderation of weather extremes, and others. Most species loss can be traced to four major threats: habitat destruction, introduced species, overexploitation, and the disruption of “interaction networks” such as food webs. Humans alteration of habitat is the single greatest threat to biodiversity. Habitat fragmentation and destruction usually leads to loss of biodiversity. Overexploitation refers generally to the human harvesting of wild plants or animals at rates exceeding the ability of populations of those species to rebound. Fishing population has caused reduction in population sizes of some fish species. Extermination of keystone species can have a devastating effect on ecosystems and communities. Concept 55.2: Population conservation focuses on population size, genetic diversity, and critical habitat 18

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Michael Zhuang Conservation biologists who adopt the small-population approach study the processes that can cause very small populations finally to become extinct The key factor driving the extinction vortex is the loss of the genetic variation necessary to enable evolutionary responses to environmental change The minimum viable population (MVP) is the minimum population size at which a species is able to sustain its numbers and survive. A population viability analysis (PVA) predicts a population’s chances for survival over a particular time. Conserving species often requires resolving conflicts between the habitat needs of endangered species and human demands. Concept 55.3 - Landscape and regional conservation aim to sustain entire biotas One goal of landscape ecology, of which ecosystem management is part, is to understand past, present, and future patterns of landscape use and to make biodiversity conservation part of land-use planning. As habitat fragmentation increases and edges become more extensive, biodiversity tends to decrease In fragmented forests, there are species that live on the exterior and species that live in the interior of a forest. A movement corridor is a strip of habitat that connects two isolated patches. They promote dispersal and help sustain populations. Most of biologists' conservation efforts are given to areas with large biological diversity. A biodiversity hot spot is a relatively small area with an exceptional concentration of endemic species and a large number of endangered and threatened species. They are good choices for nature reserves. The zoned reserve model recognizes that conservation efforts often involve working in landscapes that are largely human dominated A zoned reserve is an extensive region of land that includes one or more areas undisturbed by humans surrounded by lands that have been changed by human activity and are used for economic gain. For example, some zoned reserves in the Fiji islands are closed to fishing, which actually helps to improve fishing success in nearby areas Concept 55.4 - Restoration ecology attempts to restore degraded ecosystems to a more natural state It takes longer to recover larger areas that are disturbed (duh) We assume that most environmental damage is reversible. Bioremediation is the use of living organisms, usually prokaryotes, fungi, or plants, to detoxify polluted ecosystems. Biological augmentation uses organisms to add essential materials to a degraded ecosystem. Concept 55.5 - Sustainable development seeks to improve the human condition while conserving biodiversity Humans must figure out how to best manage earth's resources. Sustainable Biosphere Initiative - The goal of this initiative is to define and acquire the basic ecological information necessary for the intelligent and responsible development, management, and conservation of Earth’s resources 19