Using Relative Sizes to Measure Animals

Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

Did you know that scientists don't always explain size by using specific values? They can also compare things to show relative sizes, and how the size of new things relates to what you know. In this lesson, we'll learn how to use this technique.

Relative Sizes

Just what is relative size? Relative size is a way of measuring something by comparing it to the size of something else. For example, by showing a little cat next to a tiger, you can see the relative size of the tiger as compared to the cat, and vice versa. Why should you do this? Because this way of measuring an animal is a good way to really understand just how large or how small something is. For example, if someone told you that a tiger is 9 feet long, you may not think that is very impressive. But if the same person told you that a tiger is 11 times longer than a cat, you might think about your cat or your neighbor's cat. The tiger now seems like a very large animal, probably not an animal you want to meet in the wild!

You can easily make a relative size measurement yourself. What you do is you find a picture of each animal in a similar pose, then change the size of each picture so that they are at the same scale, or proportion of the size of the real animal. This will accurately show just how the size of each animal compares to the others. Let's take a look at the following examples to see how it is done.

Cat vs. Tiger

Let's take a closer look at the tiger and cat comparison.

Here's a cat. Cats typically measure 9.5 inches in height.

relative size of animals

And here's a tiger. Tigers are around 3 feet in height.

relative size of animals

Now, let's put them next to each other and see just how much larger the tiger is.

relative size of animals

As you put the images next to each other, you need to increase or decrease the size of each pictures so that they will accurately show the size difference between the cat and the tiger. To complete this step, you'll make use of the actual measurements you have for your cat and tiger. Your tiger measures 3 feet high and your cat only measures 9.5 inches high. Converting your 9.5 inches to feet so you can better compare them, you get 9.5 / 12 = 0.79 feet. To find the right size for your pictures, divide the height of your cat by the height of your tiger: 0.79 feet / 3 feet = 26.33. Finally, make your tiger picture larger and your cat picture smaller until you see that your cat is roughly 26 percent of the height of the tiger.

Now you can easily see just how much larger a tiger is than a cat.

Dog vs. Elephant

Now, let's try a German shepherd dog vs. an Asian elephant.

Here's a German shepherd dog. This dog is around 24 inches or 2 feet typically from feet to shoulders.

relative size of animals

And here's the Asian elephant. Asian elephants are around 9 feet tall.

relative size of animals

Now you can put these two images together, changing the size of each one as needed so that you can see just how much larger the elephant is. Since the dog is around 2 feet and the elephant is around 9 feet, the dog should be about 2 / 9 = 0.22 or 22 percent of the height of the elephant.

relative size of animals

Putting It All Together

When working with relative sizes of animals, you can put as many animals together as you want. Instead of comparing just two animals at a time, you can put all your animals together so you can see how the animals relate to each other-- just make sure they're all at the same scale!

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