Answer the following question given this paragraph: 19.5 Development of the Heart The heart is the first organ to form and become functional, emphasizing the importance of transport of material to and from the developing infant. It originates about day 18 or 19 from the mesoderm and begins beating and pumping blood about day 21 or 22. It forms from the cardiogenic region near the head and is visible as a prominent heart bulge on the surface of the embryo. Originally, it consists of a pair of strands called cardiogenic cords that quickly form a hollow lumen and are referred to as endocardial tubes. These then fuse into a single heart tube and differentiate into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus, starting about day 22. The primitive heart begins to form an S shape within the pericardium between days 23 and 28. The internal septa begin to form about day 28, separating the heart into the atria and ventricles, although the foramen ovale persists until shortly after birth. Between weeks five and eight, the atrioventricular valves form. The semilunar valves form between weeks five and nine. Q: In humans, what is the first organ to form and become functional? Choices: - brain - liver - pancreas - heart A:
heart

Answer the following question given this paragraph: A food chain is a simple diagram that shows one way energy flows through an ecosystem. Pictured below is an example of a food chain ( Figure below ). Producers form the base of all food chains. The consumers that eat producers are called primary consumers. The consumers that eat primary consumers are secondary consumers. This chain can continue to multiple levels. Q: What is a diagram that shows a single way that energy flows throughout an ecosystem? Choices: - fuel chain - dependent chain - water cycle - food chain A:
food chain

Answer the following question given this paragraph: The depth (distance from top to bottom) of the atmosphere is greatest at sea level and decreases at higher altitudes. With greater depth of the atmosphere, more air is pressing down from above. Therefore, air pressure is greatest at sea level and falls with increasing altitude. On top of Mount Everest, which is the tallest mountain on Earth, air pressure is only about one-third of the pressure at sea level. Q: The depth of the atmosphere is greatest where? Choices: - under water - the ionosphere - the stratosphere - sea level A:
sea level

Answer the following question given this paragraph: Water can remain in a particular location for a long time. This is known as a reservoir . Reservoirs for water include oceans, glaciers, ponds, or even the atmosphere. A water molecule may pass through a reservoir very quickly or may remain for much longer. The amount of time a molecule stays in a reservoir is known as its residence time . The residence time of water in the ocean is 3,200 years. Of course, not every molecule stays that long. That number is an average for all molecules. Q: What is the amount of time a molecule stays in a reservoir known as? Choices: - known time - reservoir time - suitable time - residence time A:
residence time