Photo by Aditya Gurav, CC BY-SA 4.0 Red-eared Slider Turtle Trachemys scripta  Most reptiles do not have sex chromosomes. They have temperature-dependent sex determination (TSD), rather than genetic sex determination. TSD is observed in many fish, all crocodilians, many turtles, and lizards. Sex in reptiles is determined by the temperature of the egg halfway through… Read More

African Clawed Frog Xenopus laevis Amphibian larvae undergo a radical transformation from being a fish-like animal, to a land-dwelling form that can live independently of free-standing water. It is, therefore, a near complete metamorphosis of one entity into another.  Xenopus laevis, commonly referred to as the African clawed frog, is notable for been the first… Read More

Giant Roundworm Ascaris lumbricoides Some nematodes (round worms) exhibit androdioecy, a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison to the other major reproductive systems. In animals, androdioecy has been considered an important stepping stone in the transition from dioecy (separate males and females) to hermaphroditism, and vice versa. … Read More

Photo by Josef Reischig, CC BY-SA 3.0 Protozoa  paramecium caudatum Paramecium protozoa have two nuclei (a large macronucleus and a single compact micronucleus). They cannot survive without the macronucleus and cannot reproduce without the micronucleus. Paramecia reproduce asexually, by binary fission - the cell divides into two halves and each new cell obtains a copy… Read More

Photo by Mogana Das Murtey and Patchamuthu Ramasamy, CC BY-SA 3.0 Tape Worm taenia solium Tapeworms have segmented bodies. Each segment is called a proglottid and contains a set of both male and female reproductive organs. As new segments form, older segments shift down the length of the worm. The oldest are at the posterior… Read More