Question

question 3
a few birds, such as ostriches, have wings but cannot fly. which of the following best explains this?
a ostriches evolved from an amphibian ancestor that had wing - like arms and glided among trees.
b ostriches evolved from a bird ancestor that flew.
c when reptiles evolved into birds, some birds developed wings for flight, but others developed wings incapab
of flight.
d ostriches evolved first, then all other flying birds evolved from ostriches.
e ostriches are not true birds.

Explanation:

• Option A: Ostriches evolved from reptilian ancestors, not amphibian ancestors.
• Option B: This is correct. Ostriches evolved from a flying bird ancestor. Over time, due to their environment and lifestyle (e.g., running on land for food and evading predators), the need for flight diminished. Natural selection favored traits like stronger legs for running rather than maintaining the ability to fly, but they still retain wings as a vestigial structure from their flying ancestors.
• Option C: Reptiles evolving into birds is a general evolutionary trend. But the key is that ostriches have a specific evolutionary path from a flying bird ancestor, not just a random development of non - flight wings during reptile - to - bird evolution.
• Option D: Ostriches did not evolve first. The evolutionary tree of birds shows a more complex branching pattern where different bird lineages evolved at different times.
• Option E: Ostriches are true birds. They have bird - specific characteristics like feathers, beaks, and lay amniotic eggs (a characteristic of birds and reptiles, but in the context of classifying as birds, they meet the avian criteria).

Answer:

B. Ostriches evolved from a bird ancestor that flew.