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Following fertilization, a zygote divides and soon becomes a multicelled embryo with many different cell types, as represented below.
Which statement best explains this development?*
Which process allows a mammal to continue to grow in size?*
A zygote develops into a multicellular organism through*
Some plants increase in height due to changes in specialized regions of cells in the tips of their branches. The processes that result in these changes include*
For a human zygote to become an embryo, it must undergo*
Base your answers to questions 6 on the illustration below and on your knowledge of biology. The illustration shows two methods of reproduction, method A and method B.
Which process takes place in both method A and method B?*
Base your answers to questions 7 on the diagram below and on your knowledge of biology. The diagram represents the reproductive cycle of a squirrel species with 40 chromosomes in each zygote.
A process that could be represented by A is*
DNA replication occurs in preparation for*
After a zygote is formed, specialization of cells occurs. Through which process do the cells of a zygote become specialized?*
The development of organs and tissues from a zygote includes*
Identify one way in which the process of growth of a human embryo is similar to the process of reproduction in a single-celled organism. *
The diagram below represents a cell nucleus. Complete the diagram so that it shows the arrangement of the genetic material in the two new cells that are produced by mitosis. 
Base your answer to question 13-15 on the information below and on your knowledge of biology.
The Critical Role of the Placenta
The proper functioning of the placenta is critical to the growth and development of a healthy fetus. For example, the placenta appears to act as a nutrient sensor. It regulates the amounts and types of nutrients that are transported from the mother to the fetus.
Improper functioning of the placenta can alter the structure and function of specific cells and organ systems in the developing fetus, putting it at risk for health problems as an adult. For example, in some pregnancies, the placenta develops a resistance to blood flow. This resistance appears to force the heart of the fetus to work harder. This could result in an increased chance of the individual developing heart disease as an adult. A group of hormones known as glucocorticoids affects the development of all the tissues and organ systems. One of the things this group of hormones does is to alter cell function by changing the structure of cell membrane receptors.
Discuss the importance of the placenta in the development of a healthy fetus. In your answer, be sure to:
• identify two factors that could influence the nutrients that can pass from the mother to the fetus 
• identify the group of hormones that alter cell membrane receptors and explain how this alteration can affect cell function 
• state the role of the uterus in the development of the fetus and the placenta *
All organisms need to reproduce for the continuation of their species. Discuss the process of reproduction in humans. In your answer, be sure to:
• identify one hormone present in a female that is involved in regulating the reproductive cycle 
• state one way the nucleus of a sex cell is different from the nucleus of a body cell 
• state how the normal chromosome number for humans is maintained from one generation to the next 
• identify one action by the mother that can influence the development of the embryo and state a result of that influence *
Scientists have learned that when a pregnant woman smokes, one of the chemicals absorbed, nicotine, can narrow the diameter of her blood vessels that lead to the placenta. Explain why narrowing the diameter of these blood vessels can result in low birth weight babies. *