Not all animal species operate on a system of only males and females! Trioecy, when hermaphrodites coexist with females and males in a population, is an understudied reproductive strategy being brought into the spotlight with pink sea urchins in the Mexican Pacific. Valentina Islas-Villanueva and Francisco Benítez-Villalobos brought their research to our attention because they found that trioecy is maintained as a time-stable mating system, not as a one-time coincidence or a disorder. Their work adds to a growing body of evidence about the naturally occurring diversity of sex in living things.
Boy sea horses get pregnant and give birth to the babies from their pouch. [Gender Showcase, K-5]
Sea Horses
Boy Sea Horses have a pouch where the girl Sea Horse places the fertilized Sea Horse eggs. This allows the boy to be pregnant and care for the growing babies. This daddy carries the babies until they are ready to be born.
Lesson Plan: The Guardian Frogs of Borneo
In this lesson for grades 5-8, students explore diversity in mating and parental behaviors across species with a clearly defined concept of sex as opposed to gender.
Gynandromorph Animals - BBC Earth article
This BBC Earth article explores the rare phenomenon of bilateral gynandromorphs, or animals which develop different physical sex characteristics on their left and right side. This occurs when a cycle of meiosis yields multiple viable eggs rather than one egg and three polar bodies to be discarded. When two eggs are fertilized by sperm, mosaicism can occur in the sex chromosomes.
When introducing students to the article, the teacher should be sure to note that overgeneralizing language is briefly used to describe humans (“In humans, men have an X and a Y chromosome, while women have two X chromosomes.”) However, the article can still have value in demonstrating the nonbinary nature of biological sex and the scientific processes by which evidence is gathered to support this.
A Reddit post shows a gynandromorph lobster found in the wild:
Diverse Reproductive Strategies Gallery Walk
In this lesson, students do a reading about R- and K-selection and then a gallery walk of four more unique reproductive strategies in animals. Students use the notes taken during the gallery walk to write a paragraph response comparing two different strategies.
The examples chosen include sequential hermaphroditism in clownfish and unisexual populations of all-female salamanders. However, they are limited in that all the example species are described to have binary sex. This lesson could be supplemented with examples of species where there are more than two sexes - see Scientific Evidence for examples.
Editor’s note: The term "hermaphrodite" is appropriate for referring to non-human animals with sex characteristics that do not fit typical binary notions of male or female bodies. For humans, “intersex” is the appropriate term—learn more here!
For a longer and more inquiry-based lesson, the gallery walk information could be shortened to remove the explanation for why each species has a unique reproductive strategy. Students could be tasked with hypothesizing the relationship between reproductive strategy and social structure or environment of the animal.
“What Makes a Baby”: 8th grade edition!
In this blog post, Gender Inclusive Biology contributor Lewis-Maday Travis discusses how he adapted a gender-inclusive reproduction picture book for his 8th grade students. He also discusses student-created language to describe a person who contributes an egg or a sperm to create a new human.
Lesson Plan: Animal Patterns of Reproduction
Image shows nine animals species that exhibit sexual dimorphism or unique reproductive strategies: elephant seals, seahorses, mallad ducks, Indian peafowl, Mormon cricket, honey bee, magnificent riflebird, clownfish, and slipper limpet.
In this lesson, students learn briefly about the reproductive strategies nine different animal species. Student use a tally to track what strategies are most common - for example, male competition, female mate choice. More unique patterns like sex-changing clownfish and touch-mediated sex development are included within the nine species.
When I taught this lesson, students learned about each species through short video recordings of teachers in our school describing the species. For more general use, I changed the lesson as posted on this website to have students do online research instead of watching the videos.
Diagrams: Animal Lives Gallery by Humon
Image shows two purple-colored figures with male symbols and one orange-colored figure with a female symbol, all caring for two yellow-colored babies.
This gallery of art by Humon depicts diverse animal mating behavior in 20 different species.
[HS and College] Inclusive and Accurate Approaches for Teaching Sex and Gender in Biology
Image of a presentation slide with the rainbow-colored Project Biodiversify logo containing an atom, a DNA double helix, a single-celled organism, a plant, and a winged insect. Title reads “ESA 2018 WK 44: Inclusive and Accurate Approaches for Teaching Sex and Gender in Biology.” The bottom of the image lists three presenter names: Alex Webster - she/her/hers - @alxweb, Ash Zemenick - they/them/theirs - @mtn_ash, and Sarah Jones - she/her/hers - @joness943.
Project Biodiversify team members Alex Webster, Ash Zemenick, and Sarah Jones presented this workshop at the 2018 Annual Meeting for the Ecological Society of America (ESA). The slides contain comprehensive information about the benefits of teaching inclusive biology, and how to adapt existing curricula using an iterative process. Extensive examples are given for sexual reproduction, sex determination, and sexual selection.