Following statements are regarding to determination of filament formation by actin concentration.

A. The critical concentration (Cc) is the concentration at which G-actin monomers are in equilibrium with actin filaments.

B. At monomer concentrations below the Cc, no polymerization takes place. 

C. When polymerization is induced at monomer concentrations above the Cc, filaments assemble until steady state is reached and the monomer concentration falls to Cc.

D. At steady state, the concentration of monomeric actin below the critical concentration.

Which of the following statements promotes spontaneous filament assembly?

#Question id: 5002

#Unit 11. Evolution and Behavior

All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.

The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the information above, which explanation is most likely?

#Question id: 5003

#Unit 11. Evolution and Behavior

Fruit fly eyes are of the compound type, structurally very different from the camera-type eyes of mammals. Even the camera-type eyes of mollusks, such as octopi, are structurally quite different from those of mammals. Yet, fruit flies, octopi, and mammals possess very similar versions of Pax-6. The fact that the same gene helps produce very different types of eyes is most likely due to

#Question id: 5004

#Unit 11. Evolution and Behavior

Pax-6 usually causes the production of a type of light-receptor pigments. In vertebrate eyes, though, a different gene (the rh gene family) is responsible for the light-receptor pigments of the retina. The rh gene, like Pax-6, is ancient. In the marine ragworm, for example, the rh gene causes production of c-opsin, which helps regulate the wormʹs biological clock. Which of these most likely accounts for vertebrate vision?

#Question id: 5005

#Unit 11. Evolution and Behavior

Fossilized stromatolites

#Question id: 5006

#Unit 11. Evolution and Behavior

The oxygen revolution changed Earthʹs environment dramatically. Which of the following adaptations took advantage of the presence of free oxygen in the oceans and atmosphere?

#Question id: 5007

#Unit 11. Evolution and Behavior

Select the factor most likely to have caused the animals and plants of India to differ greatly from species in nearby Southeast Asia.