AP Syllabus focus:
‘In some reptiles, environmental temperature during development influences sex determination, demonstrating genotype–environment interactions.’
Temperature-dependent sex determination shows how environmental conditions can direct developmental pathways. In several reptiles, incubation temperature influences whether embryos develop testes or ovaries, linking gene regulation, hormones, and ecological context.
Core idea: temperature can determine sex
In many animals, sex is set primarily by sex chromosomes. In contrast, some reptiles use environmental sex determination, where incubation temperature during embryonic development biases sex outcomes.
Practice Questions
FAQ
They shift clutches between temperatures at different developmental stages and record resulting sex ratios.
Short, repeated “temperature switch” experiments map when sex outcomes change.
No single universal sensor is known.
Evidence points to temperature affecting multiple inputs, including enzyme kinetics, membrane properties, and epigenetic marks that alter transcription in the developing gonad.
Often the relevant cue is an integrated thermal experience, not a single moment.
Some species respond to mean temperature; others are influenced by time spent above or below threshold temperatures during the TSP.
Not necessarily.
Pivotal temperature can vary with:
population genetics
maternal effects (yolk hormones)
local adaptation to climate and nesting substrates
Approaches include:
shading nests or changing nest depth
relocating nests to cooler/warmer sites
controlled incubation in hatcheries to produce needed sex ratios
