Evolution of Sex Flashcards
Whiptail Lizards’ Reproduction
Some whiptail lizard species reproduce through parthenogenesis, where females clone themselves without male fertilization. Offspring are genetically identical to the mother, maintaining population continuity without sexual reproduction
Prevalence of Sexual Reproduction
Sexual reproduction promotes genetic diversity, improving populations’ adaptability to changing environments and resilience against parasites, diseases, and environmental pressures
Disadvantage of Asexual Reproduction
Asexual reproduction limits genetic diversity, making populations more vulnerable to environmental changes, diseases, and evolutionary stagnation
Red Queen Hypothesis
This hypothesis suggests that organisms must constantly evolve to maintain their fitness relative to co-evolving species like parasites, predators, or competitors
Robert Vrijenhoek’s Topminnow Experiment
Initially, sexual topminnows in a third pond were highly susceptible to parasitic flukes due to low genetic diversity from the founder effect. Vrijenhoek introduced genetically diverse sexual fish, increasing resilience against parasites
Differences Between Eggs and Sperm
(1) size: eggs are large and nutrient-rich; sperm are small and mobile, (2) production: few eggs vs. millions of sperm, (3) motility: sperm are motile; eggs are stationary, and (4) energy investment: eggs require more energy to produce; sperm are energetically cheap
Evolution of Peacocks’ Tails
Magnificent tails evolved through intersexual selection, as females prefer larger, more colorful tails, signaling health and genetic fitness
Darwin and Peacock Tails
Darwin was initially puzzled by peacocks’ tails because their extravagant features seemed to hinder survival, contradicting natural selection
Intersexual Selection
Female mate choice for traits like plumage or songs
Intrasexual Selection
Male competition for mates through dominance or territory control
Peacock Tail Experiment
Peacocks with fewer eyespots on their tails had reduced mating success, highlighting the importance of tail display in sexual selection
Female Caution in Mate Choice
(1) High reproductive investment (e.g., pregnancy, offspring care), (2) limited reproductive opportunities, and (3) desire for high-quality genes or resources from mates
Purpose of a Rooster’s Comb
The comb signals health and vitality, attracting hens by indicating strong genetics and overall fitness
Hen’s Response to Subdominant Roosters
Hens can eject sperm from subdominant roosters post-mating, favoring dominant males’ genetic contribution
Male Damselfly Behavior
Before insemination, male damselflies use specialized anatomy to remove sperm from previous mates, increasing their reproductive success