Biogeography: Biogeography 1-6

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Geographical Biogeosciences
GEOB 102
Greg Henry

GEOB102 BIOGEOGRAPHY Biogeography 1: Introduction biogeography: scientific study of the spatial and temporal distribution of plants and animals and the processes involved in determining this distribution ecological biogeography: relationships between organisms and the environment that determine where and when organisms can be found levels of organization: - individual organism - population - community - ecosystem - biome plant resources: animals need: - nutrients - nutrients - water - water - space - space - sunlight - oxygen - CO2 climatic environmental factors: temperature, precipitation, light, wind temperature - directly influences rates of physiological processes - metabolic processes have a certain temperature range -indirectly influences the availability of/ demand on resources - influences animal physiology and need for shelter ectotherms - “cold-blooded” animals – lack the ability to internally control temperature eg. invertebrates, reptiles, amphibians endotherms - “warm-blooded” animals create heat by their metabolism eg. mammals, birds precipitation -directly influences rates of physiological processes -indirectly influences the availability of resources – eg. soil nutrients -determines water availability -distribution of organisms affected by precipitation regime: • Amount – eg. rainforests vs deserts • Type – eg. rain vs snow • Timing – eg. wet vs dry season light - photoperiod - seasonal changes in life that trigger life processes -plants - phenology – timing of events : flowering, leaf out seed set, senescence (natural aging of plants) long - day plants - >12 hours daylight, grow naturally at mid and high latitudes where summer nights are short short - day plants - < 12 hours daylight, spring & fall flowering periods, midlatitudes day- neutral plants – not regulated by photoperiod, tropical plants - animals - migration, mating period, diurnal activity (day and night activity) wind - Affects vegetation structure in highly exposed areas eg. limits growth of trees , causes excessive drying edaphic environmental factors: soil -texture, structure, organic matter, organisms, acidity and alkalinity organic matter - leaf litter, woody materials that fall on the floor - humus -rich, dark organic material through decomposition, essential to soil's fertility geomorphic environmental factors: landforms - slope steepness = angle relative to horizontal -slope aspect = orientation of slope - relief of slope position - direct influence on plants by increasing or decreasing exposure to sunlight and prevailing winds eg. slopes facing the sun have warmer, drier environments than shaded slopes exposure to sunlight and wind – rapid drainage of surfaces eg. steep slopes – surface water runoff is rapid, soil water recharge by infiltration decreases -rapid erosion can result in thinner soil gentle slopes – precipitation can penetrate soil and be retained theory of tolerance: each species is able to exist and reproduce successfully only within a definite range of values for a particular environmental factor R = organisms grow and reproduce successfully G = organisms grow but cannot reproduce S = organisms survive or persist but cannot grow T = tolerance range for that factor, beyond tolerance is lethal O = optimum level, at that level maximum performance - There are both upper and lower limits of tolerance, beyond which the organism dies bioclimatic frontiers: climatic factors interacting to determine the distributional limit of the species bioclimatic boundaries climatic elements that limit : the ponderosa pine - distribution is affected by rainfall isohyets (forest boundaries of precipitation), varies with elevation sugar maple - boundaries on N, W, and S coincide with values of annual precipitation, annual min. temperature, mean annual snowfall ecological niche: total structural and functional role of a species in the ecosystem -characteristics of a species niche include combined tolerance ranges for all the environmental factors that can influence the species - each factor can be considered as one niche dimension -multidimensional – as many dimensions as factors that define the niche Biotic factors: 1. Negative Interactions (loss for one or both species) competition Interaction Effect -predation +,- - herbivory +, - - parasitism +,- 2. Positive Interactions (benefit one or both species) symbiosis Interaction Effect - commensalism +, o - mutualism +, + Niche vs Habitat niche: role of a species “profession” in an area fundamental niche: potential distribution of the species with optimal conditions (no competition) realized niche: actual habitats where an organism is found due to interactions and limitations of resources (competition) habitat: the actual place where an organism lives; characterized by a particular set of environmental factors that match the organisms niche Biogeography 2: Population Dynamics population: a group of organisms of the same species in a given place at the same time population dynamics: may refer to: - changes between locations (spatial) - changes in the number of individuals within a population (temporal) geographical range: spatial distribution of a species dispersal: ability to move from the birth site to a new site ecological dispersal: within the geographic range geographical dispersal: expansion of the range jump dispersal: long distance, infrequent (type of geographical dispersal) diffusion: slow extension of the range over time (type of geographical dispersal) corridors: regions of similar climate and vegetation structure that facilitate dispersal barriers: regions a species is unable to colonize, inhibits dispersal.= ecological (biotic) geographical (abiotic) how does a population change in size?: - due to interactions of individual organism with the environment births, deaths, immigration, emigration carrying capacity: (K) number of individuals of a species that can be supported relatively continuously in a given environment - Environmental factors fluctuate with time, the actual number of individuals in the population also varies around k Biogeography 3: Evolution ─ a Population Process theory: a body of knowledge that is unlikely to be disproved, but is likely to be improve through testing hypotheses using the scientific method 6 fundamental propositions of darwin's theory: 1. individuals that make up populations vary 2. at least some of the variation is heritable - genes – units passed from parents to offspring 3. struggle for existence - limited resources, environmental conditions affect populations ) 4. different individuals possessing different traits leave different numbers of descendants 5. survival of the fittest 6. natural selection – select favourable traits, change in genetic structure with environmental change evolution: change in gene frequency (allele) over time changes lead to differential survival and reproductive success of individuals amd populations evolve adaptation by natural selection: genetically determined traits help individuals cope with their environment, arises through evolution of populations survival of the fittest: successful reproduction by individuals best adapted to the environment - measured as genes passed on to offspring and future generations Example of evolutionary processes: Peppered Moth 1. Moths vary in colour 2. Colour is genetically controlled 3. Population side is controlled by predators and the emnvironment 4. Colour determines survival from predators 5. Better camoflauge contributes to reproductive success of individuals 6. With environmental change, the genetics and dominant colour of the moth population changes Modern Genetics and Sources of Genetic Variation: mutation: change in genetic material (DNA) passed down from parent to offspring recombination: offspring receives two slightly different copies of each gene from its parents -number of possible genetic combinations is very large -each individual is unique polyploidy: offspring receive two sets of genes from each parent - fertile, but cannot interbreed with original population = new species species: individuals capable of interbreeding to produce fertile offspring genotype: an organism's full hereditary information - the particular set of genes it possesses phenotype: actual observed properties of an organism such as morphology development, behaviour (results from an interaction of genes and the environment) speciation: set of processes by which species are differentiated and maintained 3 properties of speciation: 1. genetic variation 2. natural selection – suitability of genes in the environment 3. genetic drift - random changes to the genetic composition of a breeding population leading to changes in gene frequency gene flow: constant mixing of genes, tends to dilute variation and prevent differentiation (opposite of speciation) geographic isolation: facilitates speciation by isolating populations, preventing gene flow, and accentuating genetic drift adaptive radiation: new environments provide opportunity for new species to adapt in different habitats through natural selection allopatric speciation: evolution of a new species by geographical isolation -phyical barrier separates a population, causing reproductive isolation eg. plate tectonics, ocean or lakes, mountain ranges, deserts sympatric speciation: speciation within a population, no spatial isolation - same geographic area reproductive isolation -timing of reproduction -mate choice -ability to use habitat or resources Biogeography 4: Biodiversity and Global Environmental Change
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