studyden bio220 notes

Ecological and Evolutionary Genetics

Introduction to Genetics

  • Genetics is the transmission of information from one generation to the next, allowing for changes in organisms over time.

  • The evolution of Homo sapiens has led to branches like humans and chimpanzees.

Genomes and Mosaics

  • Genome: Total DNA present in an organism.

  • Mitochondria: Once free-living prokaryotes, they were engulfed in an endosymbiotic event.

  • Chloroplasts: Similar endosymbiotic origins, present in all living organisms.

Sex Chromosomes

  • Human and Fruit Fly Examples:

    • Humans: XY (male) or XX (female).

    • Fruit Flies: XY or XX with Y indicating male.

  • Genetic males (heterogametic sex) produce either X or Y gametes; females (homogametic sex) only produce X gametes.

  • Birds and Lepidoptera: Females are the heterogametic sex with chromosomes ZW (female) and ZZ (male).

Autosomes and Recombination

  • Autosomes: Non-sex chromosomes that exhibit areas of high and low recombination.

  • Mitochondria and chloroplasts are maternally inherited; autosomes show equal contribution from both parents.

  • Understanding recombination is key for studying inheritance across chromosomes.

Genome Transmission

  • Modes of inheritance include:

    • Uniparental Inheritance: From one parent (e.g., mitochondria, Y chromosome).

    • Biparental Inheritance: From both parents (e.g., autosomes, X-chromosome).

  • Certain loci may be independently inherited while others are not due to recombination.

Using Genomic Data

  • Utilize biparentally inherited regions to track parental contributions:

    • Autosomal Loci: Reflects both parents' contributions.

    • Mitochondrial DNA: Reflects maternal lineages.

    • Y Chromosome: Tracks paternal lineages.

  • Genetic markers help in evolutionary studies of fitness and lineage.

Studies in Elephants

Social Structures and Breeding Patterns

  • Female elephants usually stay with natal groups (kin), forming small familial units.

  • Males leave at adolescence and do not integrate into new social groups, primarily seeking females in estrous.

Inbreeding Avoidance in Elephants

  • Two hypotheses:

    1. Inbreeding leads to lower fitness in offspring, prompting avoidance of close relatives.

    2. If inbreeding depression is weak, it may not affect reproductive success significantly.

  • Alternative for males with low mating opportunities: to refrain from reproducing instead of mating with relatives.

Inbreeding Experimentation

  • Inbreeding depression in elephants is hard to measure cumulatively due to long gestation and lifespan.

  • Proposed method: using genetic markers to infer historical inbreeding patterns.

    • Collecting DNA from stool samples allows for paternity analysis.

Observations of Behavior and Mating

  • Courtship behaviors indicate mating choices between kin and non-kin. Evidence suggests male elephants prefer non-kin.

  • Study Findings:

    • Males follow females in estrous but show a clear preference for non-kin over kin during courtship and mating.

    • Graphs illustrate male mating behaviors, reinforcing the preference for non-relatives during reproductive activities.

Genetic Data Analysis in Elephants

  • Genetic analyses revealed males avoid mating with females related through their father, showing a consistent pattern in mate selection based on genetic data.

  • Independent reproductive studies can deduce broader patterns of genetic influence on mating strategies.

Summary of Elephant Genetics

  • High variability exists in elephant reproductive success, where individual fitness is correlated with kin avoidance.

  • Identified genetic mechanisms assist in tracking and analyzing elephant breeding patterns, revealing behavioral tendencies towards kin avoidance.

Rat Population Dynamics

Urban Rat Studies in NYC

  • Brown rats were introduced to NYC in the mid-18th century, adapting to urban life.

  • Genetic studies show high local genetic diversity due to urban ecology, documented through sampling and genetic analysis.

Genetic Differentiation in Rats

  • Research into the rats emphasizes areas with high variability versus those with inbreeding dependency due to urban structures.

  • Genetic markers help to understand geographic and ecological influences on local rat populations.

Conservation Genetics and Human Impacts

The Role of Genetics in Conservation

  • Conservation genetics investigates the effects of genetic diversity on population health.

  • Examples shared include the impact of human activities on genetic variation, assessing local versus larger population effects.

Cheetahs and Florida Panthers

  • Studied populations exemplify the genetic bottlenecks and inbreeding in endangered species.

  • Suggested genetic rescue initiatives can enhance population viability by increasing genetic diversity.

Impacts of Human Behavior on Species Population Trends

  • Human agricultural practices show implications for genetic diversity and sustainability in crop production.

  • Modern issues present a dilemma between maximizing yield and minimizing ecological impacts.

Sustainable Agriculture and Food Production

The Green Revolution

  • The introduction of high-yielding crop varieties and intensive farming techniques overwhelmed through mechanization.

  • Highlighted the balance between modern agricultural demands and environmental costs, suggesting alternative methods to sustain agriculture without exhaustive resource use.

Issues with Modern Agriculture

  • Over-reliance on synthetic fertilizers and pesticides poses environmental and health risks.

  • Sustainable practices may involve shifting towards diverse crop rotations and enhancing soil health through natural fertilizers.

Future Directions

  • Continued genetic research will be critical in guiding agricultural practices to ensure sustainability alongside food security.

  • Leveraging genetic tools in breeding may yield resilient crop varieties adaptable to changing environmental pressures.