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Chapter 44

Chapter 44 and 45.docx

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Wilfrid Laurier University
Tristan Long

Chapter 44 Definitions: Habitat – the specific environment in which it lives, as characterized by its biotic and abiotic features Age structure – a statistical description of the relative numbers of individuals in each age class Generation time – the average time between the birth of an organism and the birth of its offspring Sex ratio – the relative proportions of males and females (number of females has a bigger impact on population growth than males) Demography – the statistical study of the processes that change a population’s size and density through time Cohort – a group of individuals of similar age Life history – includes the lifetime patterns of growth, maturation, and reproduction (studied to understand tradeoffs in the allocation of resources to these three activities) Carrying capacity – the maximum number of individuals that an environment can support indefinitely (represented by variable K) Intraspecific competition – the dependence of two or more individuals in a population on the same limiting resource r-selected – species that often have large numbers of small young K-selected – species that usually have small numbers of larger young 44.1: The Science of Ecology - Basic ecology: major research questions relate to the distribution and abundance of species and how they interact with each other and the physical environment - Applied ecology: develop conservation plans and amelioration programs to limit, repair, and mitigate ecological damage caused by human activities - Organismal ecology: organisms are studied to determine the genetic, biochemical, physiological, morphological, and behavioural adaptations to the abiotic environment - Population ecology: focused on groups of individuals of the same species that live together and studied on how the size and other characteristics of populations change in space and time - Community ecology: populations of different species that occur together in one area (sympatric) are examined and are studied on the interactions between species, analyzing how predation, competition, and environmental disturbances influence a community’s development, organization, and structure - Ecosystem ecology: explore how nutrients cycle and energy flows between the biotic components of an ecological community and the abiotic environment - Ecologists can test hypotheses by mathematical models representing growth, distribution, etc. 44.2: Population Characteristics - Dispersion patterns o Random (rare): individuals are neither attracted or repelled by each other o Clumped (common): offspring are close to parents, individuals close to others for mating season, areas where resources are abundant o Uniform: individuals repel one another because resources are in short supply, their environments do not overlap - Greater generation time = greater body length, smaller generation time = smaller body length - Age structure predicts future growth potential (longer life span  K-selected spcies, short  r- selected) whereas sex ratios influence number of offspring depending on number of females within the population 44.3: Demography - Life table contains this info for each age interval: o Number alive at start of age interval o Number dying during age interval o Age-specific mortality rate o Age-specific survivorship rate o Proportion of original cohort alive at state of age interval o Age-specific fecundity (seed production) - Purpose is to collect data for short-lived organisms - Three types of survivorship curves o Type I: many surviving offspring, great mortality rate for the elderly (K-selected) o Type II: constant decrease of surviving population throughout lifespan (linear) o Type III: many offspring but high mortality rate for the young (r-selected) 44.4: The Evolution of Life Histories - Greater fecundity = less parental care - Larger litter = earlier age of first reproduction 44.5: Models of Population Growth - Exponential growth: a model for when populations experience unlimited growth - Logistic growth: a model for when population growth is limited, often because available resources are finite - Species’ intrinsic rate of growth: rmax, which is the maximum per capita growth rate - Per capita growth rate: birth rate minus death rate - Growth rate would decrease the closer it gets to its carrying capacity because (b-d) would be close to zero - Greater intrinsic rate of increase = longer generation time 44.6: Population Regulation - Density-dependent factors: environmental factors, intraspecific competition, overcrowding, predation - Density-independent factors: environmental change, such as climate change - Both affect rate of mortality if populations cannot adapt well to their environment - K-selected species adapt well to fast changing environments as opposed to r-selected species - More predation = less prey, less predation = more prey  populations fluctuate around the same times 44.7b: Population Growth and Age Structure – Not All Populations Are the Same - Birth rate > death rate  pyramid - Birth rate < death rate  upside down pyramid - Birth rate = death rate  rectangle Chapter 45: Population interactions and community ecology Definitions: Coevolution – genetically based reciprocal adaptation in at least two interacting species Specialist – species that feed on one or just a few types of food (picky eaters) Generalist – species that feed on many types of food Herbivory – interaction between herbivores and the plants they eat Predation – interaction between predator and prey Batesian mimicry – occurs when a palatable/harmless species (mimic) resembles an unpalatable or poisonous one (model) Mullerian mimicry – involves two or more unpalatable species looking the same, presumably to reinforce lessons learned by a predator that attacks any species in the mimicry complex (mutual) Interspecific competition – competition between species using the same limiting resources Interference competition – one species harms another directly to access resources (ie. Killing other predators or chasing them away) Exploitative competition – two or more populations
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