Answer the following question given this paragraph: Flatworms have a concentration of nerve tissue in the head end. This was a major step in the evolution of a brain. It was also needed for bilateral symmetry. Q: Flatworms have a concentration of nerve tissue in the head end, which was a major step in the evolution of what organ? Choices: - liver - heart - kidney - brain A:
brain
Answer the following question given this paragraph: Development of the Placenta During the first several weeks of development, the cells of the endometriumreferred to as decidual cellsnourish the nascent embryo. During prenatal weeks 412, the developing placenta gradually takes over the role of feeding the embryo, and the decidual cells are no longer needed. The mature placenta is composed of tissues derived from the embryo, as well as maternal tissues of the endometrium. The placenta connects to the conceptus via the umbilical cord, which carries deoxygenated blood and wastes from the fetus through two umbilical arteries; nutrients and oxygen are carried from the mother to the fetus through the single umbilical vein. The umbilical cord is surrounded by the amnion, and the spaces within the cord around the blood vessels are filled with Wharton's jelly, a mucous connective tissue. The maternal portion of the placenta develops from the deepest layer of the endometrium, the decidua basalis. To form the embryonic portion of the placenta, the syncytiotrophoblast and the underlying cells of the trophoblast (cytotrophoblast cells) begin to proliferate along with a layer of extraembryonic mesoderm cells. These form the chorionic membrane, which envelops the entire conceptus as the chorion. The chorionic membrane forms finger-like structures called chorionic villi that burrow into the endometrium like tree roots, making up the fetal portion of the placenta. The cytotrophoblast cells perforate the chorionic villi, burrow farther into the endometrium, and remodel maternal blood vessels to augment maternal blood flow surrounding the villi. Meanwhile, fetal mesenchymal cells derived from the mesoderm fill the villi and differentiate into blood vessels, including the three umbilical blood vessels that connect the embryo to the developing placenta (Figure 28.11). Q: During the first several weeks of development, the cells of the endometrium nourish what? Choices: - egg - nucleus - uterus - embryo A:
embryo
Q: Answer the following question given this paragraph: Groundwater dissolves minerals and rocks into ions. Groundwater deposits those ions into different types of structures. Limestone caves are the best place to see these structures. Water erodes the cave and it has deposits structures like stalactites and stalagmites. The cave pictured here is Carlsbad Caverns in New Mexico. Q: Groundwater dissolves minerals and rocks into what? Choices: - gravel - sand - grit - ions A:
A: ions
Question: Answer the following question given this paragraph: When energy is released in a chemical reaction or process, that energy is expressed as a negative number. Figure below shows electron affinities in kJ/mol for the main group elements. Q: How is energy expressed when it is released in a chemical reaction? Choices: - as an equation - as a percentage - as a positive number - as negative number A:
Answer: as negative number
*Question*
Answer the following question given this paragraph: Birds need a light-weight body in order to stay aloft. Even so, flying is hard work, and flight muscles need a constant supply of oxygen- and nutrient-rich blood. The organ systems of birds are adapted to meet these needs. Q: Why do birds need a light-weight body? Choices: - for cooling - water flotation - food shortages - to stay aloft A:
**Answer**
to stay aloft
Q: Answer the following question given this paragraph: Most air masses form over polar or tropical regions. They may form over continents or oceans. Air masses are moist if they form over oceans. They are dry if they form over continents. Air masses that form over oceans are called maritime air masses. Those that form over continents are called continental air masses. The image below shows air masses that form over or near North America ( Figure below ). Q: If an air mass forms over an ocean it is called what type of air mass? Choices: - cumulus - hurricane - tropical - maritime A:
A: maritime