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All-Female Species, Middle school

A desert grassland whiptail lizard, a species with no males

In some species of lizards, snakes, fish and salamanders, every adult is female. There are zero males.

Could a species with no males keep having babies for thousands of years?

Some species are all female and they still make babies

Some lizard, snake, fish and salamander species have only females. Whiptail lizards and the Brahminy blind snake make babies with no male at all, and the babies are near copies of their mom. Some all-female fish and salamanders still need sperm from a male of another species to start their eggs.

A man riding a unicycle on a beach
A unicycle has one wheel.

Your word of the day is

yoo-nih-SEK-shoo-ul

uni-onefrom Latin ūnus
-sexualsexfrom Latin sexus

Having only one sex. Every unisexual animal with a backbone that scientists have found is all female.

Two whiptail lizards on the ground

Whiptail lizards make babies by parthenogenesis, making babies without fertilization.

Why are whiptail babies near copies of their mom?

A lizard guarding the eggs she just laid

What’s one good thing about a whiptail species where every adult is female?

An Amazon molly fish

The Amazon molly is a fish. She needs sperm from a male of another species to start her eggs.

What’s the best reason to call the Amazon molly an all-female species?

Two whiptail lizards, one on top of the other

Whiptails don’t need males. But sometimes two female whiptails act like they are mating.

Which test would show if mating-like behavior helps whiptails have babies?

Hands filling a flower pot with soil

The Brahminy blind snake has no males. It spread around the world in the soil of potted plants.

The smallest number of Brahminy blind snakes that can start a new group in a new place is ____.

A Chihuahuan spotted whiptail lizard, a species with no males

In the video, Raven says some all-female fish need sperm from a male of another species to start their eggs. She also says two female whiptails act out mating-like behavior, even though whiptails need no male.

What does a male’s sperm do for an Amazon molly egg?

A spotted lizard resting among dry rocks and leaves

Why do two female whiptails act out mating-like behavior?

A New Mexico whiptail lizard, a species with no males

Lesson complete

Today’s word

unisexual

yoo-nih-SEK-shoo-ul

Having only one sex. Every unisexual animal with a backbone that scientists have found is all female.

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Sources
  1. Aracely Lutes, Peter Baumann and colleagues, Stowers Institute, Nature, 2010
  2. A. A. Newton, P. Baumann and colleagues, Development, 2016
  3. David Crews, Mark Grassman and Jonathan Lindzey, University of Texas at Austin, PNAS, 1986
  4. Yuan Lu, Wesley Warren, Manfred Schartl and colleagues, Genome Research, 2021
  5. Review by Kathrin Lampert and Manfred Schartl, BMC Biology, 2010
  6. Florida Museum of Natural History, Florida snake ID guide
  7. Toronto Zoo, Desert grassland whiptail page
  8. The Reptile Database, Aspidoscelis uniparens entry
  9. Vision and Change core concepts and competencies, as summarized in Brownell and others, CBE Life Sciences Education, 2014
  10. Word origins from Dictionary.com: unisexual, uni-, unison, gynogenesis, gyno-, kleptomania