Unit C Lesson C11 Eyes of Other Animals
Completion requirements
Lesson C11: Eyes of Other Animals
Video Lesson
Human eyes are different from the eyes of other animals. Why can some animals see better at night than humans? Why do insect eyes look like bulging domes? Watch this video to learn about the eyes of other animals.
Lesson C11: Eyes of Other Animals
Figure C.3.11.1 – Light reflects off a raccoon’s tapetum lucidum.
Figure C.3.11.2– Light reflects in a cat’s eyes.
Figure C.3.11.3– Nocturnal animals, like koalas, often have eyeshine.
Reading and Materials
for This Lesson
Science in Action 8
Reading: Pages 236–238
Materials:
No additional materials are needed for this lesson.
Glowing Eyes
Some animals have a shiny layer of tissue at the back of the eye. This structure is called the tapetum lucidum. It acts like a mirror behind the retina, reflecting incoming light back to the retina cells. The tapetum lucidum is an adaptation that enhances the night vision of nocturnal animals, like cats. Humans do not have a tapetum lucidum.
When large amounts of light enter the eye of animals with a tapetum lucidum, their eyes appear to glow. For example, light from car headlights makes deer eyes appear to glow. A camera flash in a cat’s eyes will make the cat’s eyes appear to glow. This glow is also sometimes called eyeshine, or nightshine.
Some animals have a shiny layer of tissue at the back of the eye. This structure is called the tapetum lucidum. It acts like a mirror behind the retina, reflecting incoming light back to the retina cells. The tapetum lucidum is an adaptation that enhances the night vision of nocturnal animals, like cats. Humans do not have a tapetum lucidum.
When large amounts of light enter the eye of animals with a tapetum lucidum, their eyes appear to glow. For example, light from car headlights makes deer eyes appear to glow. A camera flash in a cat’s eyes will make the cat’s eyes appear to glow. This glow is also sometimes called eyeshine, or nightshine.
Watch More
Tapetum Lucidum
These videos explain more about the tapetum lucidum and how it reflects light in some animal eyes.
These videos explain more about the tapetum lucidum and how it reflects light in some animal eyes.
Figure C.3.11.4– Ostriches have very large eyes.
Figure C.3.11.5– Giant squids have eyes the size of a basketball.
Figure C.3.11.6– Eagles can spot prey from 3 kilometres away.
Big Eyes
Many animals have better sight than humans. The shape of some animal eyes provides them with excellent vision. For example, eagles can see clearly at great distances. Eagle eyes are about the same size as human eyes, even though their bodies are smaller than humans. The retina of an eagle eye is flattened and holds many more cones and rods than a human eye. A large, flat retina with many light-sensing cells gives eagles a sharper sense of sight than humans.
Animals that have large eyes relative to their body size also have an excellent sense of sight. Ostriches have the largest eyes of all land animals. Ostrich eyes are 5 cm in diameter, which is about the size of a billiard ball. Ostrich eyes are bigger than their brains! An ostrich’s eye collects a lot of light so they can see predators from far away.
The colossal squid and the giant squid have the largest eyes of any species on Earth. Their eyes are 30 cm in diameter, which is similar to the size of a basketball! Large squid eyes collect any available light in their dim ocean habitat, so the squid can detect their main predator, the sperm whale.
Many animals have better sight than humans. The shape of some animal eyes provides them with excellent vision. For example, eagles can see clearly at great distances. Eagle eyes are about the same size as human eyes, even though their bodies are smaller than humans. The retina of an eagle eye is flattened and holds many more cones and rods than a human eye. A large, flat retina with many light-sensing cells gives eagles a sharper sense of sight than humans.
Animals that have large eyes relative to their body size also have an excellent sense of sight. Ostriches have the largest eyes of all land animals. Ostrich eyes are 5 cm in diameter, which is about the size of a billiard ball. Ostrich eyes are bigger than their brains! An ostrich’s eye collects a lot of light so they can see predators from far away.
The colossal squid and the giant squid have the largest eyes of any species on Earth. Their eyes are 30 cm in diameter, which is similar to the size of a basketball! Large squid eyes collect any available light in their dim ocean habitat, so the squid can detect their main predator, the sperm whale.
Figure C.3.11.7– The cones in dog eyes detect blue and yellow light.
Figure C.3.11.8– Despite not having rods in their eyes, leaf-tailed geckos have excellent night vision.
Figure C.3.11.9– The mantis shrimp eye has twelve different colour-detecting cones.
Animal Colour Vision
The colours that animals see depends on the cone cells in their retina. Humans see colour because we have three different types of cone receptors in our eyes. Human cones detect red, green, and blue light.
Some animals have different numbers of cones than humans. For example, dogs only have two types of cones in their eyes. The cones in dog eyes detect different colours of light compare to humans. Cones in dog eyes detect yellow and blue light. The mantis shrimp has twelve different types of colour-detecting cones in its compound eyes.
Lizards don’t have any rods in their eyes, just cones. This means that lizards see colour during the day and the night. Despite not having any rods in its eyes, the leaf-tailed gecko’s night vision is 350 times better than human night vision. The leaf-tailed gecko has huge cones in its eyes that allow it to see colour in the dark.
The colours that animals see depends on the cone cells in their retina. Humans see colour because we have three different types of cone receptors in our eyes. Human cones detect red, green, and blue light.
Some animals have different numbers of cones than humans. For example, dogs only have two types of cones in their eyes. The cones in dog eyes detect different colours of light compare to humans. Cones in dog eyes detect yellow and blue light. The mantis shrimp has twelve different types of colour-detecting cones in its compound eyes.
Lizards don’t have any rods in their eyes, just cones. This means that lizards see colour during the day and the night. Despite not having any rods in its eyes, the leaf-tailed gecko’s night vision is 350 times better than human night vision. The leaf-tailed gecko has huge cones in its eyes that allow it to see colour in the dark.
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Different Animal Eyes
Watch this video to see how dogs view the world.
Watch this video to see how dogs view the world.
Watch this video to learn more about the mantis shrimp’s highly-sensitive eyes.
Figure C.3.11.10– Cats have vertical slit pupils.
Figure C.3.11.11– Goat pupils are horizontal slits.
Figure C.3.11.12– Insects have amazing eyes.
Interesting Eye Adaptations
The eyes of different animals are adapted to help them survive in their habitats. Eyes help animals detect approaching predators. Eyes help animals spot food and prey.
One eye adaptation is pupil shape. Humans have round pupils. This is different from many nocturnal predators that have vertical slits for pupils. Dogs, snakes, and cats all have vertical slit pupils. Slit pupils can open and close to a greater degree than round pupils. As a result, animals with slit pupils have eyesight that adjusts better to changing light conditions during the day and at night.
Some animals, like goats, have horizontal slit pupils. Horizontal pupils allow goat eyes to collect lots of light in their peripheral vision. Even as goats graze on grass, their horizontal eyes can still scan the surroundings for predators.
The eyes of different animals are adapted to help them survive in their habitats. Eyes help animals detect approaching predators. Eyes help animals spot food and prey.
One eye adaptation is pupil shape. Humans have round pupils. This is different from many nocturnal predators that have vertical slits for pupils. Dogs, snakes, and cats all have vertical slit pupils. Slit pupils can open and close to a greater degree than round pupils. As a result, animals with slit pupils have eyesight that adjusts better to changing light conditions during the day and at night.
Some animals, like goats, have horizontal slit pupils. Horizontal pupils allow goat eyes to collect lots of light in their peripheral vision. Even as goats graze on grass, their horizontal eyes can still scan the surroundings for predators.
Watch More
Animal Eye Adaptations
Different animals have different-shaped pupils. Watch this video to learn more.
Different animals have different-shaped pupils. Watch this video to learn more.
Watch this video to learn more about vertical slit pupils in cats.
Did you know goat eyes can rotate? Watch this video to learn more about this helpful adaptation.
Watch this video to learn about some additional interesting animal eye adaptations.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
Unit C Lesson 11 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here.
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
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REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
Cougars are a type of cat. Cats are nocturnal predators, which mean they hunt smaller animals for food at night. Rods detect light and movement, which is most important for a cougar hunting at night. Seeing colour is less important for cougars,
which is why they have more rods than cones.
Raptor birds hunt their prey from the air. Their large eyes can collect large amounts of light. Their large eyes can also hold many light-sensing cells. This allows raptors to see prey from a large distance, and allows them to see prey at night.
Some similarities between camera and compound eyes are:
- Both types of eyes have lenses to refract light.
- Both types of eyes contain light sensitive cells.
- Both types of eyes send a message to the brain.
Some differences between camera and compound eyes are:
- A camera eye contains one large lens that refracts light to many smaller light-sensitive cells. Compound eyes contain many ommatidia, each with a lens that refracts light down a tube to a single light-sensitive cell.
- Compound eyes create a pixelated-like image, while camera eyes create a smoother image.
Colour vision allows animals to easily distinguish between objects. This helps in finding food, such as fruit, flowers, and other animals for prey.