Diploma Prep Population Dynamics PDF

Population and Community Dynamics Possible Diploma Questions ~6-8 questions Breakdown Hardy-Weinberg Calc. and/or conditions Gene flow/genetic drift Density Dep/Indep, inter/intra competition Symbiosis Growth Curve/Carrying Capacity S vs J curve, K vs r-selected strategies Population/commun...

Population and Community Dynamics Possible Diploma Questions ~6-8 questions Breakdown Hardy-Weinberg Calc. and/or conditions Gene flow/genetic drift Density Dep/Indep, inter/intra competition Symbiosis Growth Curve/Carrying Capacity S vs J curve, K vs r-selected strategies Population/community/succession 2nd calculation  Textbook: pgs. 678 - 697 Notes: pg. 2-5 The Hardy- Weinberg Principle Recall: Genotype vs allele - Genotype: genetic composition of an individual - Genotype frequency: proportion of a population with a particular genotype (eg. number of people in brooks with blue eyes - homozygous recessive) - Allele: one version of a particular gene - Allele frequency: rate of occurrence of a particular allele within a population (eg. number of blue eye recessive alleles for eye colour in Brooks (includes heterozygotes) “Gene Pool” - Total of all the alleles for all the genes of all the individuals in a population - Represents genetic diversity within that population  The Hardy-Weinberg Principle - States that the genetic composition of a population will stay the same from one generation to the next in the absence of forces affecting allele frequency - No natural selection = no evolution = consistent allele frequencies Calculating Allele Frequency p+q=1 p = frequency of the dominant allele q = frequence of the recessive allele Calculating Genotype Frequency p2 + 2pq + q2 = 1 p2 = homozygous dominant 2pq = heterozygous q2 = homozygous recessive  Conclusion: if allele frequencies do not change between generations, the population is said to be in Hardy-Weinberg equilibrium. Evolution is not occurring. 5 Conditions of Hardy-Weinberg Equilibrium 1. Population must be large enough for allele frequencies to be unaffected by chance events 2. Mates are chosen randomly 3. No new mutations 4. No migration 5. No natural selection against any of the phenotypes This is Rarely Seen in Nature! Instead, Allele frequencies affected by: - Genetic drift - Founder effect - Bottleneck effect - Gene flow - Mutations - Natural selection - Sexual selection  Textbook: pg. 704 - 716 Notes: pg. 6-8 Population Changes Populations can be described in terms of size or density Calculating Population Density Dp = N A Dp = population density N = number of individuals A = area Patterns of Population Distribution Clumped: organisms Random: organisms dispersed in an unpredictable manner clustered in groups Uniform: organisms evenly spaces over the area they occupy What kinds of factors may contribute to each type of population distribution? Calculating Change in Population Size ΔN = (factors increasing pop.) - (factors decreasing pop.) Birth rate/natality Death rate/mortality Immigration Emigration Calculating Growth Rate gr = ΔN cgr = ΔN Δt N Per capita growth rate Increase in individuals over a describes the change in specific amount of time population compared to the initial population Formulas available in your data booklet Carrying Capacity (K) = theoretical maximum number of individuals that can be supported by a given environment. - Logistical pattern of population growth (S-shaped curve). Fluctuations are caused by: - Density-dependent factors: biotic factors (competition, predation, disease) - Density-independent factors: abiotic factors (floods, drought) Note: competition may be intraspecific (within a species) or interspecific (between different species) Absence of limiting factors = exponential growth Life Strategies: evolution of species to utilize resources differently r-Selected Strategies - Short lifespan - Early reproductive age - High biotic potential (produce many offspring and reproduce quickly) - Minimal parental investment - Often display exponential growth - Tend to have smaller body size Examples?? Life Strategies: evolution of species utilizing resources differently K-Selected Strategies - Long lifespan - Late reproductive age - Low biotic potential (produce small number offspring less frequently) - Considerable parental investment - Often display logistical growth - Tend to have larger body size Examples?? Some r-selected and some K-selected strategies r vs k Selected Species  Textbook pages: 717 - 728 Population Interactions Defences to Predation & Competition: shape evolution - Mimicry: one organism resembling another - Eg. harmless milk snake resembling the colouring of the venomous coral snake - Camouflage: organisms use to disguise their appearance, usually to blend in with their surroundings. - - Chemical defence: produce a toxin change to avoid predation - Eg. milkweed producing cardenolide toxins to avoid being eaten by caterpillars Predator - Prey Interactions = Essential to Ecosystem Balance Competition Interspecific Intraspecific - Competition between individuals - Competition between individuals of different species of the same species Symbiotic Relationships: a close, prolonged association between two or more different biological species Mutualism Commensalism Parasitism Both individuals benefit One individual benefits, One individual benefits, the other is unaffected the other is harmed Example? Example? Example? Ecological Succession Primary = starting from bare rock Secondary = starting over following an ecological disturbance Final stage = climax community (stable community in balance)