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Listening
Narrator: Listen to part of a lecture in a biology class.
Professor: Birds have some of the best vision capabilities in the animal kingdom.
Some bird species have vision that is eight to ten times greater than humans.
Overall a birds' eyes are extremely important for its survival.
One aspect of bird's eyes that plays a role in helping them survive,
in other words, to find food or to avoid predators is the position of the eyes in the skull.
Some birds have eyes that faced forward on the skull,
kind of similar to how humans' eyes are positioned.
Forward-facing eyes allow a bird to clearly see and judge distances,
because it can focus on objects with both of its eyes and correctly perceive height, width and depth.
One type of bird with eyes positioned in the front of the skull is the hawk.
Hawks eat animals like mice.
Hawks have such good eyesight that they can spot a tiny mouse in a field from high up in the air.
They spot the mouse and swooped down to catch it.
Without such good eyesight,
they would not be able to spot or catch their food.
Other birds have eyes that are located on each side of the skull.
This positioning of the eyes can help a bird to avoid predators.
Instead of just seeing what's directly in front,
they can see things that are on either side,
permitting them to watch for danger in all directions.
Imagine a duck waiting near the edge of a lake.
It needs to spend time eating grasses and insects,
but it also is on constant lookout for danger from its predator, like the fox.
An eye on each side of the duck's head allows it to see a fox approaching from either side.
If it spots of fox, it can then fly away to safety.
The placement of the eyes are critical in helping the duck avoid predators.
Question
Using the examples in the lecture, explain how the position of birds’ eyes is critical to their survival.
