How do animals see in the dark? - Anna Stöckl

TED-Ed

25 Aug 201604:23

Summary

TLDRThe nocturnal world is vibrant and detailed, contrasting sharply with human perception of night as a grey canvas. Nocturnal animals, like tarsiers and cats, have evolved unique adaptations, such as larger eyes and reflective layers, to enhance their vision in low light. Toads use slower photoreceptors to gather more photons over time, while hawk moths balance detail and light sensitivity to locate flowers in color. These adaptations create a rich visual experience, showcasing the wonders of the night that remain hidden from the eyes of daytime creatures.

Takeaways

🌙 Nocturnal animals experience a vibrant world at night, unlike humans, who see a formless grey landscape.
👁️ Moths and other nocturnal animals have evolved eyes that adapt to low light conditions, allowing them to see better in darkness.
💡 All eyes, regardless of the time of day, rely on photoreceptors in the retina to detect light particles known as photons.
☀️ On sunny days, the human eye receives up to 100 million times more photons than during a cloudy, moonless night.
🐢 Many daytime animals struggle to see in the dark due to the unreliable arrival of photons, while nocturnal animals have adapted to this challenge.
👀 The tarsier has the largest eye-to-brain ratio of any mammal, with eyes as large as grapefruits if scaled to human proportions.
✨ Cats have a reflective layer called the tapetum lucidum, enhancing their night vision by giving incoming light a second chance to be detected.
🐸 Toads can form images with just a single photon per second due to their slow photoreceptors, allowing them to gather more light over time.
🌼 Hawk moths can perceive colors in flowers even at night by grouping photoreceptor information, trading off detail for better light capture.
🌌 The various adaptations of nocturnal creatures—whether large, shiny, slow, or coarse—enable them to thrive in their unique nighttime environments.

Q & A

What is the main difference between how humans and nocturnal animals perceive the world at night?
-Humans see a formless canvas of grey at night due to limited light, while nocturnal animals perceive a rich and detailed world, thanks to their adapted eyes that can compensate for low light conditions.
How do photoreceptors in the eyes function?
-Photoreceptors in the retina detect light particles called photons and send this information to other cells in the retina and brain, which then process the information to build an image of the environment.
Why is it difficult for daytime animals to see in the dark?
-Daytime animals struggle to see in the dark because, in low-light conditions, the sparse scattering of photons makes it challenging for their eyes to gather sufficient information to create a reliable image.
What adaptation allows tarsiers to see well in the dark?
-Tarsiers have disproportionately large eyes compared to their brain size, which allows them to gather more light through larger pupils and lenses, enhancing their night vision.
What is the role of the tapetum lucidum in cats' eyes?
-The tapetum lucidum is a mirror-like structure behind the photoreceptors that reflects incoming light back towards them, giving cats enhanced night vision and the characteristic eerie glow in their eyes.
How do toads adapt their vision for low light?
-Toads have photoreceptors that are over 25 times slower than those of humans, allowing them to accumulate light for longer periods (up to four seconds), which helps them form an image even with minimal light.
How do hawk moths manage to see colors in low-light conditions?
-Hawk moths see their favorite flowers in color at night by grouping information from neighboring photoreceptors in their brains, which increases photon detection but sacrifices some detail in the image.
What is the trade-off for nocturnal animals in their visual adaptations?
-Nocturnal animals must balance the need for detecting more photons with the loss of detail in their visual perception, as adaptations to gather light often come at the cost of image clarity.
What might it be like to see the world through the eyes of nocturnal animals?
-Seeing through the eyes of nocturnal animals would reveal a vibrant world full of details, shapes, and colors that are invisible to humans at night, highlighting the uniqueness of their visual adaptations.
How do biological adaptations enhance the visual capabilities of nocturnal animals?
-Biological adaptations, such as larger eyes, reflective structures like the tapetum lucidum, and slower photoreceptors, combine to enhance the ability of nocturnal animals to perceive their environment in low-light conditions.