Temperature-dependent sex determination

Temperature-dependent sex determination (TSD) is type of environmental sex determination

Environmental sex determination

Environmental sex determination or ESD is any sex-determination system in which sex is established by a nongenetic cue experienced within a discrete period after conception. In contrast, genotypic sex determination occurs when sex is established by genetic factors at conception...

in which the temperatures experienced during embryonic development determine the sex of the offspring. It is most prevalent and common among amniote

Amniote

The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...

vertebrates that are classified under the reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

class, but is also used among some birds, such as the Australian Brush-turkey

Australian Brush-turkey

The Australian Brushturkey or Australian Brush-turkey, , also frequently called the Scrub Turkey or Bush Turkey, is a common, widespread species of mound-building bird from the family Megapodiidae found in eastern Australia from Far North Queensland to Illawarra in New South Wales...

. It differs from the chromosomal sex-determination system

Sex-determination system

A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual...

s common among vertebrates. It is a type of environmental sex determination (ESD); in other ESD systems, some factors such as population determine the sex of organisms (see Polyphenism).

The eggs are affected by the temperature at which they are incubated during the middle one-third of embryonic development

Embryogenesis

Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...