New York State Chemistry RegentsNew York State Earth Science Regents

Reproduction and Development
Living Environment Regents June 2010 Question 11 PDF Print E-mail
Monday, 30 May 2011 10:24

Correct Answer: (1) Different varieties can develop from a single species as a result of the recombination of genetic information.

During cell division, recombination of genetic information naturally occurs when the chromosomes "cross-over". When this occurs, the genes are rearranged and may code for different characteristics that are not evident in the previous variety of the species.

Incorrect Answers:

(2) Different species can develop from a single species as a result of the effect of similar environmental conditions.

Evolution of species can only occur when one or more of the following requirements are present: natural selection, genetic drift, mutation, gene flow, and nonrandom mating. All of these requirements mean change in the environment leading to transformation of organism. Thus, new varieties or species cannot develop if the environmental conditions are constant or similar to the usual.

(3) Mutations will occur in the genes of a species only if the environment changes.

Mutation refers to the changes in the genetic makeup of a cell and is the ultimate source of genetic diversity. Aside from naturally occurring mutagens, most mutations are caused by radiation or chemicals.

(4) Variations in a species will increase when the rate of mitosis is increased.

Mitosis is a process of cell division in eukaryotic cells conventionally divided into the growth period (interphase) and four stages (prophase, metaphase, anaphase, and telophase). These stages conserve the chromosome number of the cell by equally allocating replicated chromosomes to each of the daughter cells. Mitosis occurs in body cells especially during growth and development. The produced cells are the same with the parental cells. The other type of cell division  responsible for the proliferation and variation of species is meiosis, which is the cell reproduction that occurs in sex cells.

Living Environment Regents June 2010 Question 13 PDF Print E-mail
Monday, 30 May 2011 10:30

Correct Answer: (4) behaviors that lead to reproductive success have evolved

Evolution refers to the transformations that occurred in organisms over time. This may be caused by adaptation due to increase survival. Organisms have the ability to change for reproductive success and prevent extinction.

Incorrect Answers:

(1) unusual courtship behaviors lead to extinction

Extinction is the complete elimination of a certain species. Unusual courtship behaviors are just some of the mechanisms used by organisms to prevent extinction.

(2) some organisms are better adapted for sexual reproduction

All organisms have the ability to reproduce, because this will ensure the continuity of the population in the biosphere. Adaptations only occur to further ensure reproductive success.

(3) homeostasis in an organism is influenced by physical characteristics

Homeostasis or the steady-state physiological condition of the body may be affected by external conditions such as temperature. Physical characteristics like colors of the feathers have no effect on the homeostasis of the organism.
Living Environment Regents June 2010 Question 15 PDF Print E-mail
Monday, 30 May 2011 10:34

Correct answer: (1) zygote contains a complete set of genetic information

The arrow represents the process called fertilization wherein the female gamete (egg cell) and the male gamete (sperm) unite to a zygote, a fertilized egg. Each gamete contributes half of the genetic information, thus, the resulting zygote is diploid, with complete set chromosomes which contains the genetic information.

Incorrect answers:
(2) gametes contain a complete set of genetic information

The resulting zygote after fertilization of male and female gametes is not merely a gamete. A gamete is only haploid, containing only half of the genetic information. The zygote contains a complete set of chromosomes, and will eventually undergo various cell division and differentiation to form a fully-developed organism.

(3) zygote contains half of the genetic information

Zygote is a diploid product of the union of haploid gametes in conception or fertilization. Only the gametes (first and second structures in the illustration on the left side) each contain half of the genetic information.

(4) gametes contain half of the genetic information

While this statement is true that gametes contain half of the genetic information because they are only haploid, it is not true that the result of the process is a gamete. The result of fertilization (arrow) is a zygote, which is diploid, meaning it contains two sets of chromosome, one coming from the female, and another from the male gamete.
Last Updated on Monday, 30 May 2011 10:36
Living Environment Regents June 2010 Question 17 PDF Print E-mail
Monday, 30 May 2011 10:40

Correct answer: (4) division of cells resulting in the development of an embryo from a zygote

Right after fertilization, the zygote undergoes successive cell divisions, differentiation and morphogenesis. Through the succession of mitotic divisions called blastulation, the zygote becomes multi-cellular, made up of identical cells with no specific form or function yet. So, the cells undergo differentiation starting at the gastrulation stage, where the cells of the zygote becomes diverse specialized cells which will next undergo organogenesis, to form specific organs and tissues, each with specific forms and functions.

Incorrect answers:

(1) specialization of cells to form a fetus from an egg

Cellular differentiation or the structural and the functional divergence of cells as they become specialized occur during the organism's embryonic development, but not immediately after fertilization. The fertilized egg still needs to undergo numerous cell divisions in order for it to become a multi-cellular organism.

(2) production of daughter cells having twice the number of chromosomes as the parent cell

Prior to fertilization, the male or female gamete undergoes meiosis. Meiosis is the two-stage type of cellular division that results in daughter cells with half the chromosome number of the original cell.

(3) production of daughter cells having half the number of chromosome as the parent cell

This statement pertains to mitosis, the cell division that occurs in gametes prior to their union or fertilization, not after.
Living Environment Regents June 2010 Question 18 PDF Print E-mail
Monday, 30 May 2011 10:41

Correct answer: (3) 3 and 5

This illustrates the reproductive anatomy of the human female. The organ labeled as 3 is one of the ovaries, which is located in the abdominal cavity, flanking and attached by a mesentery  (not drawn) to the uterus (organ 5). The ovaries are the female gonads, or the organ the produces the egg cells and hormones. When a woman conceives, the egg cell travels from the ovary to the fallopian tube (organ 4), then to the uterus. The uterus is also known as the womb. It is a thick muscular organ that can expand during pregnancy to accommodate a fetus. The inner lining of the uterus is the endometrium, which is richly supplied with blood vessels.

Incorrect answers:

(1) 1 and 2

Organ 1 is the vagina, a thin-walled chamber that forms the birth canal through which the baby is born; it is also the repository for sperm during copulation. Organ 2 is the cervix, which is the neck of the uterus and opens into the vagina.

(2) 2 and 4

The cervix is the neck of the uterus, while organ 4 is the fallopian tube. It is a funnel-like opening, ciliated inner epithelium that aid in collecting egg cell from the body to the duct then to the uterus.

(4) 4 and 5

The fallopian tube serves as the passageway of the egg cell going to the womb or the uterus where it will stay for the next nine months.

Living Environment Regents June 2010 Question 19 PDF Print E-mail
Monday, 30 May 2011 10:43

Correct answer: (3) placenta

The placenta is the structure in the pregnant uterus for nourishing the fetus with the mother's blood supply. It is formed from the uterine lining and embryonic membranes.

Incorrect Answers:

(1) reproductive hormones

The formation reproductive hormones signal the puberty stage of individuals. For instance, a human male can exhibit erection of the male organ at birth however cannot procreate due to absence of sperm. At the age of 8 to 14 years old, a human male starts to produce hormones, specifically gonadotropins, which stimulate the maturation of the reproductive system and development of secondary sex characteristics (by increasing secretion of sex hormones from the gonads).

(2) egg cell

The egg cell formed at the ovaries, when fertilized, will eventually become a fetus.

(4) ovaries

The ovaries are the female gonads, or the organs responsible for the production of female egg cells and hormones.


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