Marine Iguana Ecology and Reproductive Strategies

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Questions and Answers

How does the size preference in female marine iguanas impact their survival under scarce food conditions?

Female marine iguanas prefer larger sizes, which may enhance their mating success, but this larger size can also increase vulnerability to starvation when food is scarce.

What role does the average $2pq$ play in assessing reproductive strategies among marine iguana subpopulations?

The average $2pq$ for individual subpopulations reflects genetic diversity and mating success, influencing reproductive strategies across different groups.

Explain how fecundity limits female reproductive success in relation to mate quality.

Fecundity restricts female reproductive success because a higher quality mate can result in fewer but more viable offspring, influencing overall reproductive outcomes.

What is the difference between polygyny and polyandry in the context of marine iguanas?

<p>Polygyny involves one male mating with multiple females, while polyandry consists of one female mating with multiple males, each strategy affecting population dynamics uniquely.</p> Signup and view all the answers

How does the value of FST indicate genetic variation within marine iguana populations?

<p>A value of FST=0 indicates no genetic differentiation among individuals, while FST=1 indicates complete differentiation, guiding insights into population structure.</p> Signup and view all the answers

What are reproductive isolating mechanisms (RIMs) and how do they contribute to speciation?

<p>Reproductive isolating mechanisms (RIMs) prevent interbreeding between species, contributing to speciation by ensuring that gene flow is restricted.</p> Signup and view all the answers

What distinguishes allopatric speciation from sympatric speciation?

<p>Allopatric speciation occurs due to geographic barriers isolating populations, while sympatric speciation happens without geographic separation.</p> Signup and view all the answers

Explain the concept of homoplasy in phylogenetics.

<p>Homoplasy refers to similar traits that evolved independently in different species, making it challenging to determine true evolutionary relationships.</p> Signup and view all the answers

What is a phylogenetic tree and what does it represent?

<p>A phylogenetic tree is a graphical representation that illustrates the hypothesized ancestor-descendant relationships among related species.</p> Signup and view all the answers

How do qualitative and quantitative measures contribute to constructing phylogenetic trees?

<p>Qualitative measures focus on common characteristics, while quantitative measures assess genetic distances or similarities among species.</p> Signup and view all the answers

What is disruptive selection and how does it affect genetic variation?

<p>Disruptive selection favors extreme phenotypes over the average, which can increase genetic variation within a population.</p> Signup and view all the answers

What does the harmonic mean formula for effective population size, $N_e$, encompass?

<p>The harmonic mean formula calculates $N_e$ over multiple generations by summing the inverse of population sizes.</p> Signup and view all the answers

How is loss of heterozygosity calculated in a random mating population?

<p>Loss of heterozygosity is calculated using the formula $F_{ST} = rac{1}{4N_m + 1}$.</p> Signup and view all the answers

What is the difference between disassortative and assortative mating?

<p>Disassortative mating occurs when individuals mate with those who are genetically or phenotypically different, while assortative mating occurs with those who are similar.</p> Signup and view all the answers

What is inbreeding depression and what causes it?

<p>Inbreeding depression is the reduced biological fitness due to mating between genetically similar individuals, often caused by recessive deleterious alleles.</p> Signup and view all the answers

How does gene flow influence a population's genetic diversity?

<p>Gene flow introduces new alleles into a population, increasing its genetic diversity and facilitating adaptation.</p> Signup and view all the answers

Explain how intrasexual and intersexual selection function in sexual selection.

<p>Intrasexual selection involves competition among the same sex for mating opportunities, while intersexual selection involves one sex choosing mates based on traits.</p> Signup and view all the answers

What does the term 'homozygous' mean in genetic context?

<p>Homozygous refers to having two identical alleles for a specific gene.</p> Signup and view all the answers

What is meant by 'effective population size' and its significance in conservation biology?

<p>Effective population size refers to the number of individuals contributing to the gene pool, crucial for maintaining genetic diversity in conservation efforts.</p> Signup and view all the answers

Discuss the role of female choice in sexual selection.

<p>Female choice allows females to select mates based on desirable traits, which can enhance the fitness of offspring.</p> Signup and view all the answers

What are transitional fossils and why are they significant in understanding evolution?

<p>Transitional fossils are remains of organisms that show intermediate traits between ancestral and descendant species, providing evidence of how species evolve over time.</p> Signup and view all the answers

How does the lack of change in genotype frequencies not imply that evolution has not occurred?

<p>Evolution can still occur through mechanisms such as genetic drift or balancing selection, even if observed genotype frequencies remain constant.</p> Signup and view all the answers

Define the role of heritability in the response to selection.

<p>Heritability measures the proportion of trait variation that can be attributed to genetics, affecting the expected response to selection (R) based on the strength of selection (S).</p> Signup and view all the answers

What is the expected response to selection (R) influenced by strength of selection (S) and heritability (h2)?

<p>The expected response to selection is calculated using the formula $R = S \times h^2$, indicating that stronger selection and higher heritability lead to greater R.</p> Signup and view all the answers

Explain how balancing selection can maintain genotype diversity within a population.

<p>Balancing selection occurs when multiple alleles are actively maintained in the gene pool due to selective advantages, leading to increased genetic diversity.</p> Signup and view all the answers

What limitations arise from the effective population size (Ne) being less than the actual population size (Nc)?

<p>When Ne is less than Nc, it can lead to reduced genetic diversity, increased inbreeding, and a higher risk of extinction due to evolutionary bottlenecks.</p> Signup and view all the answers

How does genetic variation contribute to the process of natural selection?

<p>Genetic variation provides the raw material upon which natural selection acts, allowing some individuals with advantageous traits to survive and reproduce more successfully.</p> Signup and view all the answers

What conditions must be met for genotype frequencies to remain stable in a population?

<p>Genotype frequencies will remain stable if the population experiences random mating, lacks mutation, has no selection, has no migration, and has a large population size.</p> Signup and view all the answers

Describe how the strength of directional selection (S) impacts the evolutionary trajectory of a trait.

<p>A greater strength of directional selection (S) leads to a more pronounced shift in the population's average trait value over generations, indicating rapid evolutionary change.</p> Signup and view all the answers

Why is it important to consider both the strength of selection and heritability in understanding evolutionary changes?

<p>Both strength of selection (S) and heritability (h2) determine how effectively advantageous traits are passed to offspring, influencing overall evolutionary rates.</p> Signup and view all the answers

What type of variation is typically observed in polygenic traits, such as the coloration of the Peppered Moth?

<p>Continuous variation.</p> Signup and view all the answers

How does natural selection influence the color morph frequencies of the Peppered Moth in urban versus rural environments?

<p>Urban areas favor lighter morphs due to predation, while rural areas favor darker morphs.</p> Signup and view all the answers

What is the role of multiple genes in the expression of polygenic traits?

<p>The interaction of three or more genes leads to the expression of phenotypic variations.</p> Signup and view all the answers

In the Peppered Moth, which allele is responsible for the black coloration and what is its genetic representation?

<p>The dominant allele responsible for black coloration is represented as DD or Dd.</p> Signup and view all the answers

What type of genetic variance is caused by epistatic deviations and how does it relate to traits in polygenic inheritance?

<p>Dominance genetic variance (Vd) is caused by epistatic deviations.</p> Signup and view all the answers

What might be a possible physiological advantage of black coloration in certain species, such as lizards?

<p>Black coloration may allow higher absorption of sunlight, leading to increased body temperatures.</p> Signup and view all the answers

What does the presence of several genotypes producing the same phenotype indicate in terms of genetic diversity?

<p>It indicates genetic diversity within a population, showing that multiple genetic combinations can lead to similar traits.</p> Signup and view all the answers

How does the concept of dominance alleles differ between the black and pepper coloration in Peppered Moths?

<p>Black coloration is caused by dominant alleles (D), whereas pepper color is a result of recessive alleles (d).</p> Signup and view all the answers

What does narrow-sense heritability (h2) indicate in a population?

<p>Narrow-sense heritability (h2) indicates the proportion of phenotypic variation in a population that is attributable to additive genetic variance.</p> Signup and view all the answers

How is the directional selection differential (s) calculated?

<p>The directional selection differential (s) is calculated as the difference in mean phenotype between the entire population before selection and the mean phenotype of individuals that reproduce.</p> Signup and view all the answers

What relationship does the equation ℎ2 = 𝑟/𝑠 illustrate?

<p>The equation ℎ2 = 𝑟/𝑠 illustrates the relationship between realized heritability (h2), the correlation (r) between relatives, and the directional selection differential (s).</p> Signup and view all the answers

What does the term 'ontogeny' refer to in the context of evolutionary biology?

<p>Ontogeny refers to the development of an individual organism, which follows a progression similar to the evolutionary history (phylogeny) of its species.</p> Signup and view all the answers

Describe the significance of the hourglass-like metazoan phylotypic stage in embryonic development.

<p>The hourglass-like phylotypic stage signifies that early embryonic development shows diverse forms, but as it progresses, forms converge to a similar structure before diverging into species-specific forms.</p> Signup and view all the answers

What role do highly conserved genes play in metazoan development?

<p>Highly conserved genes play a crucial role in establishing the body plan during the development of metazoans, influencing the fundamental patterning processes.</p> Signup and view all the answers

How does phenotypic variation relate to evolutionary developmental biology (Evo-devo)?

<p>Phenotypic variation is addressed in Evo-devo by examining how genetic and developmental processes interact to influence evolutionary change in morphology.</p> Signup and view all the answers

What does the progression of embryonic forms suggest about evolutionary history?

<p>The progression of embryonic forms suggests that developmental pathways reflect evolutionary history, indicating phases of morphological convergence and divergence.</p> Signup and view all the answers

Flashcards

Evolution

The change in a population's trait over time due to natural selection.

Response to Selection (R)

The observed change in a trait in response to selection.

Selection Strength (S)

The strength of selection acting on a trait.

Heritability (h^2)

The proportion of variation in a trait due to genetics.

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Transitional Fossils

Fossils that show gradual changes in a species over time, providing evidence of evolution.

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Balancing Selection

A type of selection that maintains different alleles in a population.

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Effective Population Size (Ne)

The effective population size, which is a measure of the number of individuals that contribute to the next generation.

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Genotype Frequencies

The random distribution of alleles within a population, influencing its genetic variation.

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Gene Flow

The process of migration between populations, allowing for genetic exchange.

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Genetic Drift

The reduction in genetic diversity in a population due to random events.

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Heterozygosity (H)

A measure of genetic variation within a population. It represents the average heterozygosity (proportion of individuals with two different alleles at a given locus) in a population.

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Fst

A measure of genetic variation between populations. It represents the proportion of total genetic variation that is due to differences between subpopulations.

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Subpopulation Heterozygosity (S)

The average heterozygosity (H) of individual subpopulations.

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Total Heterozygosity (T)

The total heterozygosity (H) of a population when all subpopulations are combined.

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Polygyny

A mating strategy where one male mates with multiple females. Examples include harems and lekking.

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Disruptive Selection

A type of natural selection where extreme phenotypes are favored, leading to a population with two distinct phenotypes.

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Stabilizing Selection

A type of natural selection where the average phenotype is favored, leading to a decrease in variation.

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Inbreeding Depression

The loss of genetic diversity within a population due to mating between closely related individuals.

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Disassortative Mating

A type of non-random mating where individuals mate with others who are phenotypically different from themselves.

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Assortative Mating

A type of non-random mating where individuals mate with others who are phenotypically similar to themselves.

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Intrasexual Selection

Competition amongst individuals of the same sex for access to mates.

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Intersexual Selection

Selection where members of one sex (usually females) choose mates based on certain traits.

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The Benefit of Female Choice

The process by which females choose mates based on traits that indicate good genes or resources, improving the fitness of their offspring.

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Allopatric speciation

Speciation that occurs when populations are geographically separated.

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Parapatric speciation

Speciation that occurs when populations are separated by a new barrier that arises within the range of an ancestral species.

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Phylogenetic tree

This type of speciation occurs when two or more descendant lineages diverge from a single ancestral lineage.

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Convergent evolution

The independent evolution of similar features in different lineages.

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Parallel evolution

The independent evolution of similar features in different lineages that share a common ancestor.

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Phenotypic Evolution

The change in the frequency of traits within a population over time due to natural selection.

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Polygenic Trait

A type of variation where traits are influenced by multiple genes, resulting in a wide range of phenotypes.

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Normal Distribution

The distribution of traits within a population, often bell-shaped, showing the most common traits in the middle and less common ones at the extremes.

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Dominance Genetic Variance (Vd)

A measure of the variance caused by the interaction of different genes, where one gene's effect can modify the expression of another.

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Natural Selection

The process by which individuals with certain traits are more likely to survive and reproduce, passing those beneficial traits to their offspring.

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Population Genetics

The study of the distribution and change of allelic frequencies in populations over time.

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Genetic Variation

The change in the frequency of alleles in a population due to random events, like genetic drift or natural disasters.

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Epistatic Interactions

The interaction of multiple genes to influence a single trait, leading to a wider range of possible phenotypes.

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Narrow-sense heritability (h²)

The proportion of phenotypic variation in a population that is caused by genetic effects that can be passed on from parents to offspring.

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Directional Selection Differential (s)

The difference in mean phenotype between the original unselected population and the mean of the individuals who actually breed to produce the next generation.

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Realized Heritability (h²)

Estimate of narrow-sense heritability calculated using the response to selection (r) and selection differential (s).

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Evolutionary Developmental Biology (Evo-devo)

The study of how evolutionary and developmental processes interact to shape the form and function of organisms.

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Phylotypic Stage

A stage in animal development where embryos of different species share similar forms and gene expression.

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Transcriptome

The collective set of RNA molecules expressed in a cell, tissue, or organism at a particular time.

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Hourglass Model of Development

Early stages of embryonic development display diverse appearance, converging towards a shared form before diverging again.

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Highly Conserved Genes in Development

Genes that are highly conserved across different species, playing fundamental roles in body plan development.

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Study Notes

L1-2 Overview

  • Evolution is crucial for understanding health, natural products, agriculture, environmental management, and ourselves.
  • Historical evolutionary ideas, including those of Buffon and Lamarck, predated Darwin's theory.
  • Darwin's theory posited descent from a common ancestor, survival of the fittest variants, and differential reproduction.
  • Evidence for evolution includes shared DNA and ATP, similar genetics in closely related organisms, anatomical similarities, homologous structures, vestigial structures, the fossil record, and transitional fossils.

L3-4 Genetic Diversity & Mutation

  • Variation in traits exists, differentiating individuals within a species.
  • Phenotype is determined by genotype plus environmental influences and interactions.
  • Mutations are copying errors that cause changes in alleles found on homologous chromosomes.
  • Natural selection favors organisms adapted to their environments, enhancing their ability to survive and reproduce. Genetic drift is random fluctuation of allele frequencies, mainly impactful in smaller populations.

L5-6 Selection & Drift

  • Evolution is a genetic change in population phenotype over time.
  • If genotypes aren't randomly distributed in environments, lack of change in mean phenotype doesn't imply lack of evolution.
  • Mutation rates are low, therefore mutations alone do not drive evolution, but are crucial for providing diversity from which selection acts.
  • Inbreeding in small populations leads to a greater accumulation of harmful mutations.

L7-8 Populations & Gene Flow

  • Genotype frequencies remain constant under specific conditions: large population size, no gene flow, no mutations, random mating, and no natural selection.
  • Hardy-Weinberg equilibrium describes a population where genetic variation remains constant across generations, in the absence of disturbing factors.
  • Genotype frequencies are affected by the influx of new alleles into a gene pool due to migration.

L9 Sexual Selection

  • Sexual selection, distinct from natural selection, favors traits that improve mating success.
  • Intrasexual selection occurs through competition between individuals of the same sex, while intersexual selection involves preference for specific traits by the opposite sex.
  • Female choice may promote traits that aren't beneficial for survival but enhance mate attraction.
  • Mating strategies such as monogamy, polygamy, and polyandry vary depending on species.

L10 Speciation

  • Species are reproductively isolated groups of populations.
  • Reproductive isolation mechanisms can be prezygotic (before fertilization) or postzygotic (after fertilization).
  • Speciation mechanisms include ecological, genetic conflict, sexual selection, polyploidy, and hybridization.
  • Geographic isolation (allopatric speciation) or lack of it (sympatric speciation) can also contribute to the separation of species.

L11-12 Phylogeography & Phylogenetics

  • Phylogeny is a hypothesis of evolutionary relationships.
  • Phylogenetic trees display these relationships graphically (branching patterns).
  • Homoplasy (similar traits evolving independently) should be distinguished from homology (similar traits due to common ancestry).

L13-14 Polygenic Inheritance

  • Polygenic traits, influenced by multiple genes, exhibit continuous variation, such as height.
  • The interaction of multiple genes affects traits through additive or non-additive effects.
  • Polygenic traits vary along a bell curve.

L15-16 Evolutionary Developmental Biology

  • Evo-devo compares development patterns in different organisms to understand evolutionary processes.
  • Similar genetic regulatory mechanisms may explain shared developmental stages despite divergent taxa.
  • Recapitulation (ontogeny recapitulates phylogeny) idea, although not completely accurate, highlights the evolutionary connection between developmental stages.

L17-18 Genome Evolution

  • Genome organization and size vary significantly among species.
  • Non-coding DNA, introns, and transposons make up significant parts of many eukaryotic genomes.
  • Retrotransposons replicate through an RNA intermediate.

L19-20 Biodiversity Conservation

  • Neutral genetic diversity is not directly linked to fitness, driven by mutation and drift.
  • Adaptive genetic diversity enhances fitness in given environments; natural selection impacts frequencies.

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