Coquita the Crocodile

Predict

Coquita the crocodile lived alone at a reptile park in Costa Rica for 16 years. She never met a male. Then she laid 14 eggs. Could one of those eggs have a baby inside?

Circle one. Yes / No

Why?

Watch

1. Virgin birth in a crocodileyoutube.com/shorts/9Fil5Efiz9o
2. Coquita’s virgin birth is not a cloneyoutube.com/shorts/PkigBKfd-oU

Word of the day

Parthenogenesis (par-theh-no-JEN-uh-sis). An egg develops into a baby without sperm fertilizing the egg.

• The Parthenon in Athens took its name from Athena Parthenos, “Athena the Virgin.”
• You can spot the same gen root in gene and genetics. Gen means birth or origin.

Bonus words. Homozygous (ho-mo-ZY-gus), the word Raven has you say out loud in video 2, means a gene comes as a matching pair, from homo-, “same.” Heterozygous (het-er-oh-ZY-gus) means a mixed pair, from hetero-, “different.”

Questions

1. Coquita’s baby matched her at more than 99.9% of the spots where she carried two identical copies of a gene. The scientists still say the baby isn’t a clone. How can Coquita’s baby match Coquita at more than 99.9% of her homozygous sites and still not be a clone?

   Hint. Look at the spots where Coquita carried two different versions of a gene.

2. Many female reptiles can store sperm for years. What two pieces of evidence rule out stored sperm as the source of Coquita’s baby?

   Hint. One piece comes from Coquita’s life at the park. The other comes from her baby’s DNA.

3. Coquita’s baby is homozygous at almost every gene, meaning both copies of each gene match. What can happen to Coquita’s baby at a gene where Coquita carries one working copy and one broken copy?

   Hint. Coquita’s baby gets one of Coquita’s two copies, twice. List every pair the baby could end up with.

4. American crocodiles are a vulnerable species, which means they could become endangered. The scientists who studied Coquita say zoos should check eggs from females kept alone, instead of throwing those eggs away. Why would checking eggs from lone females help a vulnerable species like the American crocodile?

   Hint. For a species at risk, every egg that could hatch counts. What might zoos be throwing away?

Claim, evidence, reasoning

Going further

1. Coquita’s kind of parthenogenesis is called facultative, meaning the animal can reproduce with a mate or without one. Scientists have found it in crocodiles and in birds, the two living branches of the archosaurs. And birds are the only dinosaurs alive today. Could extinct dinosaurs like Tyrannosaurus have reproduced without a mate? Use the crocodile and bird evidence, then name one piece of evidence you’d still need.

   Hint. Birds are living dinosaurs, and crocodiles are the closest living relatives of birds. Think about what an ancestor could pass down to both groups.

Exit ticket