New York State Chemistry RegentsNew York State Earth Science Regents

 
Reproduction and Development
Living Environment Regents June 2004 Question 11 PDF Print E-mail

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Correct Answer: The rate of evolution in this species is slower than in one that reproduces sexually

Evolution refers to all the changes that have transformed life on earth from its earliest beginnings to the diversity that characterizes it today. One of the differences between mitosis and meiosis is the crossing over of chromosomes. This only occurs in meiosis. During this event, there is an exchange of genetic material between homologous chromosomes, and thus there is a variation between the parent and its offsprings. Since evolution is a process of deviating from the original forms of life, meiosis makes evolution to occur faster.

 
Living Environment Regents June 2004 Question 15 PDF Print E-mail

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Correct Answer: (1) meiosis and fertilization.

The male and female gametes are formed by meiosis. During this process, the chromosome number of each gametes are halved. And then, when the male and female gametes unite, the chromosomes are combined to recover the diploidy of the cell.

Incorrect Answers:

During mitosis, the chromosome number of the daughter cells is the same with the parent cells. Mutation is the change in the DNA sequence.

Differentiation refers to the change in the cell's structure and function during the development of the organism. Aging is the latest stage of development wherein most cells of the body are old and not regenerating.

Homeostasis and dynamic equilibrium refer to the stable state of the organism's internal environment.

 
Living Environment Regents June 2004 Question 16 PDF Print E-mail

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Correct Answer: (4) permit passage of nutrients and oxygen from the mother to the fetus

Placenta functions for the delivery of oxygen and food from the mother to the fetus. Aside from that, it also aids in disposal of the fetus' waster through the mother's kidney.

Incorrect Answers:

The fetal blood and heart are developed from the fetus itself through the process of differentiation of cells during embryonic development.

Oxygen and nutrients diffuse from the maternal blood to the fetal blood.

 
Living Environment Regents June 2004 Question 17 PDF Print E-mail

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Correct Answer: (1) transfer of sperm to a female

Structure X is the vas deferens. It is a muscular part where the sperm is propelled from the epididymis during ejaculation.

Incorrect Answers:

Testis is the male gonad responsible for the production of sperm.

Kidney is the excretory organ responsible for the production of urine.

Penis is an organ of the male reproductive system and excretory system which is responsible for the release or transfer of sperm and urine.

 
Living Environment Regents June 2004 Question 58 PDF Print E-mail

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In order for fertilization to take place, the male and female gametes (sperm and egg cells) must unite. The head of the sperm contains enzymes that help the sperm penetrate the egg. As the sperm crosses the cell membrane of the egg, its nucleus and the egg's nucleus combine to form a zygote.

The genetic content of the zygote is different from the parents', but their chromosome numbers are the same. During the meiosis of each of the gametes, the chromosomes underwent chromosomal crossover. This phenomenon brings about variation. Plus, when the genetic materials of the parents are combined, more variation occurs in the zygote.

The earliest stage after fertilization is the cleavage stage, characterized by successive cell divisions.  During this stage, the cells undergo the S (DNA synthesis) and M (mitosis) phases of the cell cycle but other virtually skip the G1 and G2 phases. Gene transcription is virtually shut down during cleavage because of rapid DNA replication, and the embryo does not grow during this period of development. It simply partitions the cytoplasm of the unicellular zygote into many smaller cells called the blastomeres which later forms into a hollow ball of cells called blastocyst.

Most time of fetal development occurs in the uterus, a thick and muscular organ that can expand during pregnancy. Its inner lining is called the endometrium, which has several blood vessels for the supply of nutrients and oxygen from the mother to the embryo.

The blood sugar levels and blood pressure of the mother affects the fetal development. This might cause premature birth of the baby. Another factor affecting fetal development is the medicines taken up by the mother. There are a number of medicines that can cause birth defects.

 
Living Environment Regents June 2004 Question 59 PDF Print E-mail

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AIDS or Acquired immune deficiency syndrome is caused by the HIV (human immunodeficiency virus). HIV attacks the immune system of the body by weakening the immune system making the human vulnerable to opportunistic infections and tumors. Most AIDS cases are due to sexual contact with another individual infected with HIV. Thus, safe sex is promoted by using condoms. Another mode of transmission is by contact with body fluids like blood and sputum of an infected individual. Healthcare personnel who are most often exposed to these body fluids of various individuals are advised to follow precautionary methods. These include frequent washing of hands and usage of barriers such as gloves, masks, protective eyeware or shields, and gowns or aprons which prevent exposure of the skin or mucous membranes to blood borne pathogens.

 


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