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This 6 page Class Notes was uploaded by Aurora Moberly on Saturday October 15, 2016. The Class Notes belongs to Biol 3030 at Southern Utah University taught by Dr. Rachel Bolus in Fall 2016. Since its upload, it has received 4 views. For similar materials see Ecology in Biology at Southern Utah University.
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Date Created: 10/15/16
Test 10/21 Life History Life History Life History: An individual’s major life events related to its growth, development, reproduction and survival Life History Strategy: The overall pattern in the timing and nature of life history events averaged across all the individuals in the species Phenotypic Plasticity: A single genotype may produce different phenotypes (traits) under different environmental conditions Allocation: The relative amounts of energy or resources that an organism devotes to different functions There is variation in life histories among species due to variation in genetics (nature) and variation in environment (nuture) Reproduction Morphs: Discrete phenotypes of a single genotype with no intermediate forms Allometry: Differential growth of body parts that results in a change in shape or proportion with size Isogamy: Production of equal sized gametes Anisogamy: Production of gametes of a different size Hermaphrodites: Reproduce by selffertilization or by mating Sequential Hermaphroditism: Changes in sex during the course of the life cycle Complex Life Cycle: Life cycle in which there are at least two distinct stages that differ in their habitat, physiology or morphology Metamorphosis: An abrupt transition from the larval to the juvenile stage that is sometimes accompanied by a change in habitat Direct Development: Development from fertilized egg to juvenile occurs within the egg prior to hatching and no freeliving larval stage occurs Semelparous: Species reproduce only once in a lifetime Iteroparous: Species reproduce multiple times in their life Lack Clutch Size: The maximum number of offspring that a parent can successfully raise to maturity Scheme for classifying reproductive diversity: rselection and kselection rSelection: Selection for high population growth rates; Occurs when population densities are low kSelection: Selection for slower population growth rates; Occurs in populations that are at or approaching K K: The carrying capacity or stable population size for the environment in which they live Organisms at the rselected end of the spectrum are often small, short life spans, rapid development, early maturation, low parental investment, high rates of reproduction Organisms at the kselected end of the spectrum are often longlived, develop slowly, delay maturation, invest heavily in each offspring, low rates of reproduction Plants are limited by two factors stress and disturbance and can be classified using those factors Stress: External abiotic factor that limits vegetative growth Disturbance: Any process that destroys plant biomass Three plant life history patterns correspond to three habitat types 1. Competitive: Low stresslow disturbance 2. Ruderal: Low stresshigh disturbance 3. StressTolerant: High stresslow disturbance Competitive Plants: Will have a selective advantage in conditions of low stresslow disturbance due to their superior ability to acquire light, minerals, water, space Ruderals: Classification of plants that are adapted to habitats with low stresshigh disturbance StressTolerant Plants: Will have a selective advantage in high stresslow disturbance Life Cycle Evolution Dispersal: The movement of organisms from their birthplace Dormancy: A state of suspended growth and development in which an organism can survive unfavorable conditions Small offspring are well suited for dispersal and dormancy Transcript:Itishypothesizedthatthreeenvironmentalgradientsandtheir interactionsaffecttheextremesinplantlifehistorytraits:disturbance,competition, The small sizes of early life cycle stages make them vulnerable to predationandstress.shortages Complex life cycles allow life histories the flexibility to respond to differences in selection pressures on different life cycle stages Organisms that make a large investment in each offspring produce small numbers of large offspring and vice versa Behavioral Ecology Test 10/21 Evolution and Behavior Behavioral Ecology: The study of the ecological and evolutionary basis of animal behavior Behavior: Response of an organism to its environment Proximate Causes: An immediate cause based on internal features of an organism that can be used to explain how a behavior occurs Ultimate Cause: The underlying evolutionary reason for a particular behavior Assuming that genes affect behaviors and that natural selection has shaped behaviors over time we can predict how animals will behave in certain situations Umwelt: An organism’s own worldview, shaped by its sensory systems, neural structures, genetics, etc. Any behavior can be explained by four causes: 1. Causation (Mechanism) “Proximate Question” 2. Ontogeny (Development) “Proximate Question” 3. Phylogeny (Evolutionary History) “Ultimate Question” 4. Function (Adaptation) “Ultimate Question” Altruism: Behavior that has costs but no benefits for the organism Foraging Behavior Individuals will alter foraging decisions based on predators or the perceived risk of predation Prey survive predation using behaviors like avoiding being seen by predators, detecting predators, preventing attack or escaping an attack Optimal Foraging Theory: Predicts that foraging animals will maximize their net energy gain invested in seeking, capturing and extracting food resources Marginal Value Theorem: Model proposing that an animal should stay in a food patch until the rate of energy gain declines to the average rate for the habitat then depart to another patch Mating Behavior Monogamy: One sexual partner Polygyny: One male mates with multiple females Polyandry: One female mates with multiple males Promiscuity: Males and females mate with multiple partners Males are often larger, colored or possess unusual weapons or ornaments as a result of sexual selection Females invest more in the offspring and that is why they get to be choosy; Some species are the opposite and the male is choosy Handicap Hypothesis: If a female chooses a male that can support a costly ornament it is likely that he will pass on good genes to both her sons and daughters Sexy Son Hypothesis: The female receives indirect genetic benefits through her sons who will themselves be attractive and produce many grandchildren Selfish Gene: Evolution favors genes for behavioral traits that result int heir being passed on to as many offspring as possible Living in Groups Dilution Effect: As the number of individuals in a group increases the change of being the one attacked decreases Benefits of group living is access to mates, protection from predators, improved foraging success Costs of group living are greater energy expenditures, increased competition for food, higher risk of disease Optimal group size will have a balance between the benefits and costs of group living Population Ecology Populations Population: Groups of individuals of the same species that live within a particular area and interact with one another Populations are dynamic, their distributions and abundances can change greatly over time and space Populations can be spatially isolated from one another but dispersion can link populations of a species Distribution and Abundance Distribution: The geographical area where individuals of a species are present Abundance: The number of individuals of a species that are found in a given area Abundance can be reported by either population size or population density Population Size: The number of individuals in the population Population Density: The number of individuals per unit of area Test 10/21 Dispersion Within Populations In species that can reproduce asexually individuals can be defined in terms of genetic individuals (genets) or physiological individuals (ramets) Genet: A genetic individual resulting from a single fertilization event that may have multiple parts that can each function as an independent physiological unit Ramet: A potentially physiologically independent member of a genet that may compete with other members for resources Disturbance: An abiotic event that kills or damages some individuals and thereby creates opportunities for other individuals to grow and reproduce Dispersion: Spatial arrangement of individuals within a population Dispersal Limitation: A species limited capacity for dispersal can prevent it from reaching areas of suitable habitat Regular Dispersion: Individuals are relatively evenly spaced throughout their habitat Random Dispersion: Individuals are randomly spaced in their habitat Clumped Dispersion: Individuals are grouped together in their habitat Clumping may result from short dispersal distances Competition can produce a nearly regular dispersion Behavioral interactions in which individuals repel or attract one another can affect the dispersion of individuals within a population Estimating Abundances and Distributions Absolute Population Size: The total number of individuals in a population Relative Population Size: The number of individuals in one time interval relative to the number in another Ecological Niche: The abiotic and biotic conditions that the species needs to grow, survive and reproduce Niche Model: A tool that predicts a species geographic distribution based on the environmental conditions at locations the species is known to occupy The distribution and abundance of organisms are limited by habitat suitability, historical factors and dispersal The suitability of habitat depends on abiotic and biotic features, and the interaction between abiotic and biotic factors and disturbance Dispersal and events in the evolutionary and geologic history of Earth also influence the distribution and abundance of organisms The most direct way to determine the number of individuals in a population is to count all of them Other ways to determine population numbers are areabased counts, distance methods, markrecapture studies The geographical distribution of an organism can be analyzed in terms of its ecological niche, the abiotic and biotic conditions of the environment that the organism needs to grow, survive and reproduce Population Growth Life Tables Life Table: A summary of how survival and reproductive rates vary with the age of the organisms Survival Rate (S )x The chance that an individual of age x will survive to be age x+1 Survivorship (I )x The proportion of individuals that survive from birth to age x Fecundity (F ): The average number of offspring produced by a female while she is of age x x If agespecific survival and fecundity rates are constant over time the population will grow at a fixed rate from year to year Cohort Life Table: The fate of a group of individuals born during the same time period (cohort) is followed from birth to death (Used for plants or sessile organisms) Static Life Table: The survival and reproduction of individuals of different ages during a single time period are recorded (Used for mobile organisms or organisms with long life spans) Survivorship Curves: Survivorship data are used to plot the numbers of individuals from a hypothetical cohort that will survive to reach different ages Type I Survivorship: Young organisms have high survival rates and death rates do not increase until old age Type II Survivorship: Individuals have the same change of surviving from one age to the next throughout their lives Type III Survivorship: Individuals die at high rates when they are young but those who reach adulthood survive The most common type observed in nature, species usually produce lots of offspring Age Structure Age Structure: The proportions of the population in each age class Age Class: Members of a population whose ages fall within a specified range Age structure influences whether a population increases or decreases in size Stable Age Distribution: When the age structure of a population does not change from one year to the next Test 10/21 Population Growths Geometric Growth: If the population changes in size by a constant proportion from one time period to the next Exponential Growth: A population with continuous reproduction changes in size by a constant proportion at each instant in time Doubling Time: Time it takes for a population to double in size Net Reproductive Rate: The mean number of offspring produced by individual during its lifetime Whenever R is0greater than 1 then will be greater than 1 Logistic Growth: A pattern in which abundance increases rapidly at first then stabilizes at carrying capacity Carrying Capacity: The maximum population size that can be supported indefinitely by the environment Effects of Density DensityIndependent Factors: Factors that affect birth and death rates independent of the density of the population DensityDependent Factors: Factors that cause birth and death rates or dispersal rates to change as the density of the population changes As density increases birth rates decrease, death rates increase, dispersal increases Population Regulation: When densitydependent factors cause population size to increase when numbers are low and decrease when numbers are high Equations Population Growth Rate Year to Year: = (N )/N t+1 t : Population growth rate year to year Nt Population numbers in year t t: Year Geometric Growth: N = N t+1 t : Geometric population growth rate Nt Population numbers in year t t: Year Geometric Growth: N= N t t 0 : Geometric population growth rate Nt Population numbers in year t t: Year N0: Initial population size Exponential Growth: (dN)/(dt)= rN (dN)/(dt): Rate of change in population size at each instant in time r: Exponential growth rate N: Current population size Exponential Growth: N(t)= N(0)e rt N(t): Population size at each instant in time r: Exponential growth rate N(0): Initial population size e: Base of natural logarithm, 2.718 t: Time Compare Results of Discrete and Continuous Time Growth Models: =e or r=ln() r e: Base of natural logarithm, 2.718 r: Exponential growth rate : Geometric population growth rate Doubling Time: t = (ld(2))/r d : Doubling time r: Exponential growth rate xlast Net Reproductive Rate: R = 0 xfirst IxFx R0: Net reproductive rate Xfirstrst age of reproduction Xlastast age of reproduction I : Survivorship x Fx: Fecundity Logistic Equation: (dN)/(dt)= rN(1(N/K)) Test 10/21 (dN)/(dt): Rate of change in population size at each instant in time t: Time N: Population density r: Population growth rate under ideal conditions K: Density at which the population stops increasing in size (carrying capacity) Population Dynamics Population Growth Patterns Population can change as a result of birth (increases ), death (decreases ), immigration (increases ) and emigration (decreases ) Population Dynamics: The ways a population changes in abundance over time There are four population growth patterns 1. Exponential Growth 2. Logistic Growth 3. Population Fluctuations 4. Regular Population Cycles 1. Exponential Growth: Can occur for a limited time when conditions are favorable If conditions are favorable in a new environment the population will grow exponentially until densitydependent factors act to regulate the population Dispersal can lead to exponential growth because of the new area Jump Dispersal: A long distance dispersal event by which a species that successfully colonize new geographic region 2. Logistic Growth: Found in populations that increase initially and then level off at carrying capacity Some populations reach a stable population size called an equilibrium the changes little over time 3. Population Fluctuations: Found in all populations, population numbers rise and fall over time; Most common growth pattern The population either fluctuations from an overall mean number or deviates from a population growth pattern entirely 4. Regular Population Cycles: Alternating periods of high and low population size occur after constant intervals of time Population cycles may stop entirely if key environmental conditions change BottomUp Control: Occurs when the abundance of a population is limited by nutrient supply or food availability TopDown Control: Occurs when the abundance of a population is limited by predators Delayed Density Dependence Delayed Density Dependence: Delays in the effect that density has on population size Delay density dependence can produce several types of population fluctuations including damped oscillations and stable limit cycles Damped Oscillations: The deviations from the carrying capacity gradually get smaller over time Stable Limit Cycles: Regular cycle that fluctuates indefinitely around the carrying capacity When a population grows rapidly or when there is a long time lag the size of the population can become much larger than carrying capacity before it begins to decline Risk of Extinction The risk of extinction increases in populations whose growth rate () varies from one year to the next Population fluctuations increase the risk of extinction because variations in slow population growth The greater the extent of variation the greater the risk of extinction in small populations Small populations are at a greater risk of extinction than large populations Small populations can be driven to extinction by: 1. Genetic Drift: Chance events influence which alleles are passed on to the next generation Causes a loss of genetic variation Causes an increase in harmful alleles of the population 2. Inbreeding: Mating between related individuals Causes an increase in homozygotes which increases harmful alleles in a population 3. Demographic Stochasticity: Chance events related to the survival and reproduction of individuals Causes small populations to fluctuate Causes allee effects Allee Effects: Occur when the population growth rate decreases as the population density decreases 4. Environmental Stochasticity: Erratic or unpredictable changes in the environment that cause changes in the average birth or death rates from one year to the next Causes fluctuations in population growth rates Causes environmental variation Test 10/21 5. Natural Catastrophes: Extreme environmental events that can affect population size Metapopulations Metapopulation: Spatially isolated sets of populations linked by dispersal; Characterized by repeated extinctions and colonizations Sources: Populations in which the number of individuals that disperse is greater than the number of migrants that are received Sinks: Populations in which the number of migrants received is greater than the number of individuals that dispersed Extinction and colonization rates often vary among metapopulation’s patches Metapopulations can be prone to extinction for two reasons: 1. The distance between patches makes dispersal difficult 2. Environmental conditions can change in a rapid and unpredictable manner Habitat fragmentation can increase patch isolation and decrease patch size thereby increasing extinction risk for metapopulations Rescue Effect: High rates of immigration protect a population from extinction
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