Model Organisms in Medicine: Why Comparative Embryology Matters in the Real World

I. Engage

1. Tell students today they will learn about an animal that is both a life-threatening menace and life-saving hero-- ask if they have any guesses?

Confirm or deny guesses by showing them Rollie the Armadillo video and then Armadillo vs. Dog.

Have students practice a quick Claims Evidence Reasoning by supporting either the claim that they are playing or the claim that they are fighting using evidence from the video. 

2. Now we've clearly established armadillos are cute and vicious to toy bears. But how do they help or hurt humans?

Engage students in a close read (stop and ask questions periodically) about the former Hawaiian Leper colony Kalaupapa.

In the article, it mentions armadillos, ask students what they think it means.

3. Give students a leprosy fact sheet located in the attachments. Have them read and summarize as a group.

Key points: leprosy is a bacteria that only grows in humans and armadillos (and some lab mice). Due to the fact it would only grow in armadillos, they were used to study the bacteria, research a vaccine, and develop effective treatments. Leprosy used to mean a life of exile. Now, thanks to armadillos and scientists, people can be screened, be given vaccines or treated so they have normal lives. 

II. Explore

4. Ask students what made the armadillo a successful substitute for humans in researching leprosy-- make a group list on the board (similar temperature, smaller, easier to take care of, not [as] unethical to infect/test on them). Determine some things were similar and some were different in a good way. 

FQ: If one organism has similarities to humans that enable us to study diseases without researching on humans, could there be other organisms with similarities?

Let's consider Motor Neuron Disease. 

Motor neuron disease http://www.ninds.nih.gov/disorders/motor_neuron_diseases/detail_motor_neuron_diseases.htm

It is a problem with the motor neurons—the cells that connect your brain to your muscles and tell them to move. We don’t understand it well in humans—to be able to study the disease in an animal, what characteristics would the animal need to have in common with us?

Example answers: Brain, nervous system, motor neurons, muscles

Suggested questioning: What are the components of the nervous system?

It happens that many animals have similar types of nervous systems to us. It turns out that even though many animals look very different as adults, we are very similar as we develop.

FQ: What are the similarities and how long to they last?

Let’s consider some animals. Ask student to name some cool animals; keep going until you have a big list. Ask students to group the animals by big categories (birds, mammals, fish, reptiles, insects, etc).

We know that all living things are made of cells and all cells come from other cells. So, we all started as one cell. Did that first cell look the same? Probably. So that one cell divides into two, and they each divide into four and so on. Do you think the balls of cells look the same? Probably. Anyone remember one of the names for that? We’re going to use embryo, which means a developing baby. Let’s take a look at embryos for different organisms. See if you can figure out which is which?

5. Students get a copy of "early stage embryo" strip, animal cards, and student embryology sheet (attached). Once students have completed early they get the "mid" strip, then the "late". It should be nearly impossible to tell which is which in early, some indication in middle, and they should be able to figure it out by late. It is important for them to get the strips independently so that they have to think about similarities and differences among stages. 

6. Ask students to identify what was similar among all of the embryos (this will be quick as the drawings don't have a lot of detail).

III. Explain

7. The students are ready for some vocabulary now. All of the animals in guess the embryo are chordates, and we could specify that they are all vertebrates. What makes a chordate is that it has 4 features during development. In some animals these stay, in others they go away, but all chordates have them at some point.

a. A [post anal] tail (just the word "tail" is fine). You can really play this up with students joking about how they used to have a tail.

b. A dorsal hollow nerve cord. Dorsal, like a dorsal fin, means back. Theirs became their spinal cord and brain

c. A notochord. For some animals, this is like a spinal cord. For us it directs a lot of early development and then goes away

d. Pharyngeal (gill) slits. The term "gill" is misleading because we didn't all have gills in development-- it's more about structures that later develop in your head and neck (See pictures in ppt).

8. If you want, students can use dough or clay to make model chordate embryos to show these 4 structures. Here's a college-level lesson; you could have students do much less detail.

9. Have students watch a couple of embryonic development animals: Zebrafish   Chicken   Elephant (this one is amazing). Note how short a time it takes the zebra fish to develop and how long it takes the elephant.

IV. Elaborate 

10. Back to our question about motor neuron disease, what we are looking for is a model organism-- something that will function like a human. Do we now know of some other animals that have similar nervous system development to humans? Yes-- fish, salamander, turtle, etc. Ask students to select one of the animals from the embryo activity to be a model for humans. They should consider which animals have short life cycles, are cheap and easy to take care of, and would be most ethical to experiment on. Ask students to explain their reasoning. 

11. Explain that there are many animals used as model organisms but one of the most popular for development and embryology is the zebra fish-- they are cheap and easy to care for, produce a lot of eggs, have a very short life cycle, and are close enough to humans to be a good model. They are used to study things like cancer, diabetes, and motor neuron disease.

I. Engage

1. Tell students today they will learn about an animal that is both a life-threatening menace and life-saving hero-- ask if they have any guesses?

Confirm or deny guesses by showing them Rollie the Armadillo video and then Armadillo vs. Dog.

Have students practice a quick Claims Evidence Reasoning by supporting either the claim that they are playing or the claim that they are fighting using evidence from the video. 

2. Now we've clearly established armadillos are cute and vicious to toy bears. But how do they help or hurt humans?

Engage students in a close read (stop and ask questions periodically) about the former Hawaiian Leper colony Kalaupapa.

In the article, it mentions armadillos, ask students what they think it means.

3. Give students a leprosy fact sheet located in the attachments. Have them read and summarize as a group.

Key points: leprosy is a bacteria that only grows in humans and armadillos (and some lab mice). Due to the fact it would only grow in armadillos, they were used to study the bacteria, research a vaccine, and develop effective treatments. Leprosy used to mean a life of exile. Now, thanks to armadillos and scientists, people can be screened, be given vaccines or treated so they have normal lives. 

II. Explore

4. Ask students what made the armadillo a successful substitute for humans in researching leprosy-- make a group list on the board (similar temperature, smaller, easier to take care of, not [as] unethical to infect/test on them). Determine some things were similar and some were different in a good way. 

FQ: If one organism has similarities to humans that enable us to study diseases without researching on humans, could there be other organisms with similarities?

Let's consider Motor Neuron Disease. 

Motor neuron disease http://www.ninds.nih.gov/disorders/motor_neuron_diseases/detail_motor_neuron_diseases.htm

It is a problem with the motor neurons—the cells that connect your brain to your muscles and tell them to move. We don’t understand it well in humans—to be able to study the disease in an animal, what characteristics would the animal need to have in common with us?

Example answers: Brain, nervous system, motor neurons, muscles

Suggested questioning: What are the components of the nervous system?

It happens that many animals have similar types of nervous systems to us. It turns out that even though many animals look very different as adults, we are very similar as we develop.

FQ: What are the similarities and how long to they last?

Let’s consider some animals. Ask student to name some cool animals; keep going until you have a big list. Ask students to group the animals by big categories (birds, mammals, fish, reptiles, insects, etc).

We know that all living things are made of cells and all cells come from other cells. So, we all started as one cell. Did that first cell look the same? Probably. So that one cell divides into two, and they each divide into four and so on. Do you think the balls of cells look the same? Probably. Anyone remember one of the names for that? We’re going to use embryo, which means a developing baby. Let’s take a look at embryos for different organisms. See if you can figure out which is which?

5. Students get a copy of "early stage embryo" strip, animal cards, and student embryology sheet (attached). Once students have completed early they get the "mid" strip, then the "late". It should be nearly impossible to tell which is which in early, some indication in middle, and they should be able to figure it out by late. It is important for them to get the strips independently so that they have to think about similarities and differences among stages. 

6. Ask students to identify what was similar among all of the embryos (this will be quick as the drawings don't have a lot of detail).

III. Explain

7. The students are ready for some vocabulary now. All of the animals in guess the embryo are chordates, and we could specify that they are all vertebrates. What makes a chordate is that it has 4 features during development. In some animals these stay, in others they go away, but all chordates have them at some point.

a. A [post anal] tail (just the word "tail" is fine). You can really play this up with students joking about how they used to have a tail.

b. A dorsal hollow nerve cord. Dorsal, like a dorsal fin, means back. Theirs became their spinal cord and brain

c. A notochord. For some animals, this is like a spinal cord. For us it directs a lot of early development and then goes away

d. Pharyngeal (gill) slits. The term "gill" is misleading because we didn't all have gills in development-- it's more about structures that later develop in your head and neck (See pictures in ppt).

8. If you want, students can use dough or clay to make model chordate embryos to show these 4 structures. Here's a college-level lesson; you could have students do much less detail.

9. Have students watch a couple of embryonic development animals: Zebrafish   Chicken   Elephant (this one is amazing). Note how short a time it takes the zebra fish to develop and how long it takes the elephant.

IV. Elaborate 

10. Back to our question about motor neuron disease, what we are looking for is a model organism-- something that will function like a human. Do we now know of some other animals that have similar nervous system development to humans? Yes-- fish, salamander, turtle, etc. Ask students to select one of the animals from the embryo activity to be a model for humans. They should consider which animals have short life cycles, are cheap and easy to take care of, and would be most ethical to experiment on. Ask students to explain their reasoning. 

11. Explain that there are many animals used as model organisms but one of the most popular for development and embryology is the zebra fish-- they are cheap and easy to care for, produce a lot of eggs, have a very short life cycle, and are close enough to humans to be a good model. They are used to study things like cancer, diabetes, and motor neuron disease.