Why Do Cave Fish Lose Their Eyes

the ability to see

the ability to see

the ability to swim

the ability to hear

Darwin's understanding of evolution and his explanation of blindness in cave fishes

the animals Darwin studied as a young man that led him to develop his theory of evolution

the objections that have been raised to the theory of evolution developed by Darwin

Darwin's daily life in the 19th century and the places where he studied blindness in cave fishes

"...if you have an accident and lose a finger, your children will still be born with five fingers on each hand. If you lift weights and become a body builder, it doesn't mean your children will be born with bulging biceps. In each case, your genes haven't changed-even though your body has."

"We usually think of evolution in a positive sense, that is, as a process in which species acquire new traits. But in cave fishes we have an example of regressive evolution, a process in which species lose a trait-in this case, the ability to see."

"In some of these underground caves, there are fishes, crustaceans, salamanders and other organisms that have evolved to live without light. For example, more than one hundred species of cave fishes live their lives in perpetual darkness. They depend on senses other than sight to hunt, eat and reproduce. "

"jean-Baptiste Lamarck...suggested that giraffes stretched their necks to reach higher leaves, and as a result their offspring were born with longer necks. The idea that cave fishes lost their eyesight because generations of fish didn't use their eyes is a Lamarckian mistake."

The trait of blindness has positive effect; it gives the fish an evolutionary advantage.

The trait of blindness has a mixed effect; it is an advantage for the fish at certain times and a disadvantage at other times.

The trait of blindness has a neutral effect: it is neither an advantage nor a disadvantage.

The trait of blindness has a negative effect; it gives the fish an evolutionary disadvantage.

The neutral mutation hypothesis about the blindness of cave fishes is based on the idea that the mutations that cause blindness have no effect (or a neutral effect) on the survival of a fish living in a dark cave.

Many cave fishes are blind, and an experiment carried out by scientists suggests that blindness in these fishes is the result of a mutation that also improves their sense of smell.

Charles Darwin was a scientist living in the 19th century who was convinced that cave fishes lost their eyesight because they did not use their eyes.

There are caves deep underground where the sun never shines, and in some of these underground caves, there are fishes, crustaceans, salamanders, and other organisms that have evolved over many years to live without light.

to criticize scientists for not having reached a definite answer about why cave fishes lose their eyes

to encourage readers to answer the question on their own before they read the article

to prepare readers for a discussion of possible answers to this question in the article

to praise scientists for the effort they have put into understanding the cause of blindness in cave fishes

Consequently

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