Evolution of Eyes: Complex Adaptations

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Questions and Answers

What did Darwin express about the evolution of the eye in relation to natural selection?

He believed that complex organs like the eye were beyond reach of evolution.

He found it plausible that natural selection could produce the eye.

He thought the human eye could not have evolved from simpler forms.

He considered the idea of natural selection producing the eye to be absurd. (correct)

Which of the following best describes the presence of eyes in the common ancestor of all animals?

Eyes were absent in the common ancestor of all animals. (correct)

Sponges were known to possess primitive eyes in their lineage.

The common ancestor of all animals had various types of eyes.

Eyes were common in the common ancestor of all animals.

What feature do all animal eyes use to capture light?

Lens structures

Crystallins

Photoreceptors (correct)

Pupil adjustments

How do the eyes of octopuses and squids differ from human eyes?

Their photoreceptors point outward from the retina. Signup and view all the answers

Which of the following correctly categorizes the clade that contains animals with eyes?

Eumetazoans Signup and view all the answers

What kind of eyes do scallops possess?

Delicate chains of eyes Signup and view all the answers

Which type of animal is stated to lack eyes according to the evolutionary lineage?

Sponges Signup and view all the answers

What is a key difference in the photoreceptors of different animal groups?

They vary in shape and function. Signup and view all the answers

What is the primary role of opsins in the eye?

Opsins trigger chemical reactions in photoreceptor cells. Signup and view all the answers

Which type of opsin is found in all vertebrates?

c-opsin Signup and view all the answers

What distinguishes r-opsins from c-opsins in terms of storage?

R-opsins are kept in membrane foldings, while c-opsins are in disks. Signup and view all the answers

Which of the following animal lineages does not utilize c-opsins for image capture?

Insects Signup and view all the answers

What was the conclusion made by scientists regarding the evolution of eyes in different animal lineages?

Eyes have a common evolutionary origin across animal lineages. Signup and view all the answers

In humans, what is the role of r-opsins?

To process images from the retina. Signup and view all the answers

What does the presence of c-opsins in invertebrates like ragworms suggest?

C-opsins may have a shared ancestor with some invertebrates. Signup and view all the answers

Which statement is true regarding the opsins found in different animal groups?

Only vertebrates possess c-opsins. Signup and view all the answers

Study Notes

Complex Adaptations: The Evolution of Eyes

Darwin was amazed by the complexity of the human eye, considering it a prime example of natural selection.
The eye's evolution can be traced back to the earliest derived lineages of living animals, the sponges and placozoans, which lack eyes.
Eyes evolved in a clade of more derived animals known as eumetazoans.

Eye Types and Diversity

All animal eyes capture light with cells called photoreceptors but vary greatly in shape and structure, from the camera-like eyes of humans and octopuses to the simple light-sensitive spots of flatworms.
The photoreceptors of octopuses and squids point outward from the retina, while human photoreceptors point inwards.

The Role of Opsins

Light triggers reactions in opsin molecules located on the surface of photoreceptor cells, initiating electrical signals sent to the brain.
All vertebrates utilize c-opsins, which are found in stacks of disks within the cilia of the retina.
Invertebrates, including insects, octopuses, and scallops, use r-opsins, which are stored in membrane foldings of their photoreceptors.
Both c-opsins and r-opsins evolved in separate lineages, suggesting independent evolution of image-capturing organs.

Convergent Evolution: Similarities and Differences

Humans produce both c-opsins and r-opsins, but r-opsins play a role in image processing rather than light capture.
Invertebrates also have c-opsins, as found in ragworms.
These discoveries demonstrate that complex organs like the eye can evolve through convergence, with different evolutionary paths leading to similar structures and functions.

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Description

This quiz explores the fascinating evolution of eyes, highlighting the complexity observed by Darwin and the various forms of eyes across the animal kingdom. Delve into the differences in eye structure and the role of opsins in vision, revealing the intricacies of natural selection as it relates to visual systems.