Bio sex final

Sex Determination

• Genetic Factors: Determine underlying sex via sex chromosomes.

  • Male in chickens: ZZ

  • Male in humans: XY

• Environmental Factors: Include temperature-dependent influences.

  • Size can also affect sex determination (in certain species).

• Intersex Individuals:

  • Represents variations in sex that do not conform to typical definitions of male or female.

  • Approximately 5 million people classified as intersex globally.

  • Prader Scale: A tool used to quantify intersex characteristics in external genitalia.

Disorders and Syndromes

• Turner Syndrome (X0):

  • Individuals can survive with just one X chromosome.

  • Presents as female with broad neck.

  • Cannot reproduce.

• Klinefelter Syndrome (XXY):

  • Common genetic disorder that may lead to mild feminization and reduced fertility.

• XYY Syndrome:

  • Generally undiagnosed; height is often the only noticeable symptom.

• Androgen Insensitivity Syndrome:

  • Individuals are XY but have no functional testosterone receptors.

  • Presents as female; characterized by absence of ovaries and uterus, but presence of testes.

• Congenital Adrenal Hyperplasia (CAH):

  • XX individuals may have elevated testosterone levels, potentially masculinizing anatomy.

• 5-alpha Reductase Deficiency:

  • A lack of crucial enzyme affecting external genital development in XY individuals.

Processes of Sexual Development

• Testis development in XY individuals begins with the SRY gene on the Y chromosome.

  • Fetal testes produce testosterone and MIH (Müllerian Inhibiting Hormone), inhibiting female duct development.

  • In the absence of testosterone, female duct systems develop by default.

• Sexual Differentiation:

  • Occurs during the 6-7 week post-fertilization embryo stage.

  • Testosterone induced male duct systems develop, while MIH prevents female duct progression.

Sex Determination in Nature

• Atrazine: A herbicide causing certain amphibians to develop both male and female reproductive traits by lowering testosterone levels.

• Temperature-Dependent Determination:

  • In some species, like turtles, temperature influences sex: low temps favor males, high temps favor females.

  • Patterns observed in some reptiles and fishes, demonstrating diverse evolutionary pathways for sex determination.

Mating Systems

• Definitions:

  • Polygamy: 1 male mates with multiple females.

  • Polyandry: 1 female mates with multiple males.

  • Promiscuity: Mating with multiple partners regardless of social bonds.

  • Monogamy: 1 male and 1 female mate; can also be social or genetic.

• Extra Pair Copulation (EPC): Occurs in socially monogamous species where pairs mate but may also engage with others.

  • Example: Penguins often practice social monogamy while sourcing resources from others.

• Sexual Conflict: Males and females can have differing reproductive strategies and preferences.

Evolutionary and Behavioral Strategies

• Sexual Selection:

  • Overt competition for mates and territories, as observed through aggressive interactions.

  • Choice predominantly by females, often based on physical displays such as ornaments (i.e., peacock tails).

• Mating Displays and Benefits:

  • Displays of beauty or territory can attract mates, leading to better reproductive outcomes.

  • Indirect benefits to offspring quality when choosing dominant males known for traits indicative of health and survival.

Human Mating Behavior

• Humans exhibit unique mating customs influenced by culture and social constructs.

  • Variations exist across populations in fertility cues and attractiveness preferences.

  • Studies indicate that waist-to-hip ratios, facial symmetry, and health indicators play roles in mate selection.

• Parental Care Dynamics:

  • Parents often invest more in their biological offspring, despite variations in family structures.

  • The effects of stepparenting can introduce stress and impacts on the health of stepchildren.

Gender Identity and Sexual Attraction

• Definitions:

  • Sex: Biological classification (XX or XY).

  • Gender: Psychological sense of identity.

  • Transgender: Individuals whose gender identity differs from assigned sex at birth.

  • Cisgender: Individuals whose gender identity matches their assigned sex at birth.

• Gender Dysphoria: A condition experienced by some transgender individuals regarding alignment with sex identity.

• Gender-Affirming Care: Access to medical treatments for transitioning, including surgeries primarily focused on breast reduction.