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Community Ecology - Coggle Diagram
Community Ecology
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Microevolution is the change in a population's gene pool from generation to generation. It occurs when the conditions for Hardy-Weinberg equilibrium are violated.
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No genetic drift. The population is so large allele frequencies do not change due to random sampling effects. (Genetic drift is the random loss of alleles, acting most strongly in small populations). Includes the bottleneck effect (large population suddenly diminished).
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No migration. (Migration or gene flow is the movement of alleles into (immigration) and out of (emigration) a population. Can be impeded by environment/life history.).
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Random mating. (Nonrandom mating occurs when individuals reproduce more based on phenotype or when plants "choose" mates via pollinators. Includes sexual selection like male-male competition or female choice
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Natural selection occurs when one allele is selectively advantageous. Individuals with beneficial alleles are more likely to survive and reproduce. Over generations, this changes allele frequencies and alters species characteristics. The result is a population better adapted to its environment or more successful at reproduction.
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Death alone does not mean natural selection has occurred; it requires differential survival based on heritable phenotypes coded by genotypes.
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Directional selection: Favors one extreme phenotype. The mean trait value changes (x0 ≠ x1), while variance may remain similar (var0 = var1). Example: Gladiolus longicollis flower tube length (implied).
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Stabilizing selection: Favors the intermediate phenotype, reducing variation. The mean trait value stays the same (x0 = x1), but variance decreases (var0 > var1 - Note: The source states var0 > var1, which indicates a decrease in variance over time, assuming x0 and var0 are the initial mean and variance). Example: Rhodolirium montanum flower size (implied).
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Disruptive selection: Favors both extreme phenotypes, leading to a bimodal distribution. The mean trait value may stay the same (x0 = x1), but variance increases (var0 < var1 - Note: The source states var0 < var1, which indicates an increase in variance over time, assuming x0 and var0 are the initial mean and variance). Example: Polomonium viscosum flower nectar production (implied).
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Artificial selection is selection by humans to increase the frequency of desired traits and eliminate undesired ones, practiced for thousands of years in crop breeding (e.g., Brassica)
Heredity
Genetic Variation
In a diploid individual, each chromosome has a partner (homologous chromosomes
Homologous chromosomes resemble each other in size, shape, and hereditary information
Independent assortment: The random orientation of bivalents during Metaphase I and sister chromatids during Metaphase II of meiosis
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Sexual reproduction: Combines alleles from each parent, promoting heterozygosity
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Chromosome mutation: Deletion, duplication, inversion, translocation
Chromosome mutation: Deletion, duplication, inversion, translocation
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Allopolyploid: Meiotic error and mismatch during mating, followed by a second mating to create matched pairs
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Incomplete dominance: Phenotype of heterozygote is intermediate between those of the parent homozygotes (e.g., red x white snapdragons = pink).
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Multiple alleles: Many populations have more than two alleles for a particular locus (e.g., determining dominance requires breeding experiments).
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Polygenic inheritance: Multiple genes influence one character. Phenotype is the cumulative result of combined effects of many genes. Most traits are polygenic and show continuous variation, leading to a normal distribution in populations. Example: abscisic acid production.
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Epistasis: One gene interacts with another, potentially interfering or masking its effect. Example: Digitalis petal color involving genes for red intensity and pigment location.
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Linkage: Genes located close together on the same chromosome may not segregate independently. This results in parental haploid genotypes being more abundant than recombinant types.
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Pleiotropy: A single gene has multiple effects on the phenotype, visibly influencing several traits. Example: wheat awns affecting yield
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Parental: True breeding, homozygous.
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F1: First filial generation, typically heterozygotes from a cross between two different homozygotes.
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Principle of Dominance: In heterozygotes, one allele (dominant) has a detectable effect on appearance, while the other (recessive) has no discernable effect
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Principle of Segregation: Alleles separate from one another during meiosis. Each gamete contains only one allele for each gene. Offspring inherit two alleles for a gene, one from each parent, by inheriting homologous chromosomes
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Principle of Independent Assortment: Gene pairs that are not linked segregate independently. Evidence comes from dihybrid crosses showing a 3:1 phenotypic ratio for each allele
Monohybrid cross: A cross between two homozygous parents with different alleles. Punnett square is a visual representation of offspring inheritance patterns
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Plant Strategies
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selected species (e.g., Dandelion):
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Grime's model considers factors like stress (resource availability, growth inhibitors) and disturbance (biotic and abiotic)
A community is a group of actually or potentially interacting species living in the same location, bound by a shared environment and a network of influence
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A community is a group of actually or potentially interacting species living in the same location, bound by a shared environment and a network of influence
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Life History: Ecologists use birth and death rates at different ages and the current age and sex makeup of a population to predict if it will grow or shrink
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Key parameters in a life table include: age, Number alive proportion of individuals of age x that survive to age proportion of individuals that survive from birth average number of offspring born to a female average number of offspring per capita
Mean generation time It represents the average time between two consecutive generations or the average age between parent and offspring
Survivorship curves visually represent how long individuals survive. They are plotted logarithmically, typically using log10 of (lx * 1000) against age
Survivorship curves are dependent on the environment, and the same species
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Population Genetics
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Gene pool: All of the alleles of every gene in a population. A population is a group of interbreeding individuals of the same species in the same location.
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Allele frequency: Number of copies of an allele divided by the total number of alleles for that gene in a population.
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Genotype frequency: Number of individuals with a particular genotype divided by the total number of individuals in a population.
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Hardy-Weinberg equation predicts unchanging allele and genotype frequencies from generation to generation if certain conditions are met.
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The frequency of gametes carrying a particular allele equals the allele frequency in a population in Hardy-Weinberg equilibrium.
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(p + q)² = 1², which expands to p² + 2pq + q² = 1 (Genotype frequencies sum to 1)
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