1. What is a species?

Questions and Answers from the live classes:

William Wietman: ​@Science Mom how tall are Zeus's legs?

Zeus, the world’s tallest dog in the 2012 and 2013 Guinness Book of World Records, measured 3 feet 8 inches (1.12 meters) from his foot to his withers or shoulders. He reached 7 feet 4 inches (2.23 m) standing on his hind legs. At the Guinness Book of World Records webpage, there is short video that highlights just how large he was.

Photo credit: Guinness World Records (A picture of a very tall great dane)

Kylie and Ellie​: Were dachshunds made tiny by people too?

Photo credit: Windrush Rioter, 1891. From akc.org (An old black-and-white picture of a dachshund)

Yes, dachshunds were created by selectively breeding for a dwarf mutation. It is not known which breeds were used to create dachshunds but they may have included bloodhounds, terriers, and pinschers. Dachshunds have been around for a while. There are reports of them dating back to the 15th century. The Americal Kennel Club has a good article about the history of dachshunds, which were originally bred to hunt badgers. In German, the word "dachs" means badger and "hund" means dog. So dachshund literally means "badger-dog."


3 amigos: What is the difference between a dog and a wolf?

While dogs share 99.9% of their genetic makeup with and are descended from wolves, there are many differences. We have bred dogs to maintain puppy-like features with floppy ears, shorter noses, and an ability to digest a wide variety of food, including grains. Wolves are built to run with a narrow chest and long legs. Domestic dogs come in a variety of shapes and sizes, much of them wider and stockier than wolves. But perhaps the biggest differences are observed in their behaviors. Wolves live in a structured group where a dominant pair (the alpha male and female) control and lead the rest of the pack. The nonprofit organization Living with Wolves has an interactive online exhibit where you can learn more about wolves.

Rebecca Walters​: Are most cats and dogs hybrids? I know that there are pure breeds for dogs and cats but what does that mean for the other kinds?

The term hybrid most often refers to an animal that has parents from two different species, although sometimes it is used to describe a cross between two varieties or breeds. All domesticated dogs are the same species (Canis familiaris) and the same is true for cats (Felis catus). Purebred dogs or cats have been purposely bred by humans to perform a task and have consistent physical traits and temperament. 

Registered breeds of dogs have strict standards for the traits that distinguish that breed. For example, a Great Dane that is less than 30 inches tall at the shoulder would be considered "below standard" for that breed. A breeder who was breeding purebred Great Danes would only select dogs to breed that were taller than 30 inches at the shoulder when fully grown. Mixed breeds and "mutts" (dogs that have no discernible breed) often have fewer health problems than purebred dogs because they have greater genetic diversity. 

Mister Master​: Can fish crossbreed?

Yes, fish can crossbreed, but usually don’t in the wild.

William Wietman​: How can plants be hybrid?

Hybridization of plants occurs in nature through various mechanisms. Some plants (such as the oil palm) are insect-pollinated, and others (such as corn) are wind-pollinated. If pollen from one plant fertilizes the flower on another plant with different genetics, these plants are referred to as cross-pollinated. Many plants have flowers designed so that cross-pollination will happen. But some, such as peas, wheat, and rice, are self-pollinating and will not form hybrids without outside intervention. 

Ibrahim: Why are mules sterile?

A mule receives 32 horse chromosomes from mom and 31 donkey chromosomes from dad for a total of 63 chromosomes. If the mom is a donkey and the dad is a horse, the hybrid animal is called a hinny instead of a mule.

With both hinnies and mules, the odd number of chromosomes causes problems in meiosis (something we'll learn about in our next unit of class) because one chromosome doesn’t match with anything. Because of the odd number of chromosomes and how different horse and donkey chromosomes are, mules usually cannot produce cells like eggs and sperm that are critical for reproduction. 

K & H Roho: ​Can you define chromosome again?

A chromosome is a strand of DNA that is wrapped around proteins and stored in the nucleus of the cell. Humans have 23 pairs of chromosomes. 

Rachel Williams:​ @Science Mom what breed is your dog?

Kaladin is half Poodle and half Havanese. This mix is called a “Havapoo.” We were looking for a dog during June of 2020, a time when it seemed that everyone else in Nevada was also adopting pets. The local animal shelters were empty and often when I called a pet store in Las Vegas to ask if they had a small non-shedding breed, that dog would be gone by the time we arrived because someone else had already taken it home!

One day when I called a pet store and asked if they had any non-shedding dogs, they replied, “We have a Havapoo.” I replied, “A have-a-what?” I had never heard of a Havanese or a Havapoo before we met Kaladin.

(A picture of Kaladin at 12 weeks old.)

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