The largest amount of yolk is found in the egg of

Analyze the question: It asks which group of animals has eggs containing the largest amount of yolk. Yolk is the stored food (nutrients) that feeds the developing embryo.

Explain the concept: The amount of yolk depends on how long the embryo develops inside the egg and whether it has a larval stage or other food source.

• Amphibians: Eggs have little yolk. They hatch quickly into free-feeding tadpoles.
• Pisces (fishes): Most fish eggs have a small to moderate amount of yolk, and the larvae soon feed on their own.
• Reptiles: Eggs are large and rich in yolk. They are laid on land and the young hatch as miniature adults.
• Aves (birds): Eggs are also large and rich in yolk. The embryo develops entirely inside the shell and hatches fully formed.

Step-by-step solution:

1. Eggs with a large yolk are called macrolecithal (telolecithal) eggs.
2. Both reptiles and birds lay these, because the embryo must complete its development inside a shelled egg with no outside food.
3. Comparing the two, a bird's egg (such as an ostrich or hen egg) has the largest relative and absolute yolk mass among the options.

Note that reptile eggs are also very yolky, so the question is a bit close. The expected answer is based on birds, which are well known for their big yolks (think of a hen's egg).

Answer: D. aves

Tip: Remember "big yolk = big shelled egg." Of the options, birds are the classic example. When a question about yolk lists both reptiles and birds, pick aves, since the yolk of a bird's egg is the one most often used in textbooks.