Answer:
They digest without the use of teeth.
Explanation:
The food trickles from the crop into the bird's stomach (proventriculus or gizzard) where digestive enzymes are added to the mix and physical grinding of the food occurs. The gizzard is why chickens do not need teeth.
Answer:
Cells are so little, so they can maximize their ratio of surface area to volume.
Explanation:
Smaller cells have a higher ratio which allows more molecules and ions to move across the cell membrane per unit of cytoplasmic volume. Cells are so small because they need to be able to get the nutrients in and the waste out quickly.
Answer:
Arteries
Explanation:
There are three main types of blood vessels: veins, arteries, and capillaries. Arteries are the blood vessels that carry the oxygenated blood from the heart to various body parts. Veins pick the deoxygenated blood and deliver it to the heart to be oxygenated.
Arteries are the blood vessels with thick walls and no valves. Blood is pumped with higher pressure from the heart into arteries. The pulmonary artery is the only exception that carries deoxygenated blood from the right ventricle to the lungs for oxygenation.
