Regents Examination in Living Environment: Questions on Standard 4, Biological Concepts, Key Idea 4 - Reproductive Continuity

Key Idea 4—Reproductive Continuity
The continuity of life is sustained through reproduction and development.
 

Which occurs in a plant cell but not in an animal cell during mitotic cell division?
formation of spindle fibers
chromosome duplication
formation of a cell plate
cytoplasmic division

A plant cell with 12 chromosomes undergoes normal mitosis. What is the total number of chromosomes in each of the resulting daughter cells?
24
12
6
4

Asexual reproduction differs from sexual reproduction in that, in asexual reproduction,
new organisms are usually genetically identical to the parent
the reproductive cycle involves the production of gametes
nuclei of sex cells fuse to form a zygote
offspring show much genetic variation

In most multicellular animals, meiotic cell division occurs in specialized organs known as
gonads
gametes
kidneys
cytoplasmic organelles

Which is an important adaptation for reproduction among land animals?
fertilization of gametes outside the body of the female
fertilization of gametes within the body of the female
production of sperm cells with thick cell walls
production of sperm cells with thin cell walls

In humans, a single primary sex cell may produce four gametes. These gametes are known as
diploid egg cells
monoploid egg cells
polar bodies
sperm cells

In sexual reproduction, the 2n chromosome number is restored as a direct result of
fertilization
gamete formation
cleavage
meiosis

In human females, the main function of the follicle-stimulating hormone (FSH) secreted by the pituitary gland is to
stimulate the adrenal glands to produce cortisone
stimulate activity in the ovaries
control the metabolism of calcium
regulate the rate of oxidation in the body

If the first stage of an uninterrupted human menstrual cycle is the follicle stage, the last stage includes the
formation of sperm cells in the testis
release of a mature egg
buildup of the uterinelining
shedding of the uterine lining

Which statement best describes internal fertilization?
It does not require motile gametes.
It helps to make terrestrial life possible.
It requires the presence of many eggs.
It normally occurs in the male.

What are the normal chromosome numbers of a sperm, egg, and zygote, respectively?
monoploid, monoploid, and monoploid
monoploid, diploid, and diploid
diploid, diploid, and diploid
monoploid, monoploid, and diploid
 

When compared with the number of gametes produced from a single primary sex cell during oogenesis, the number of gametes produced from a single human primary sex cell during spermatogenesis is usually
four times as great
twice as great
half as great
the same

In human males, sperm cells are suspended in a fluid medium. The main advantage gained from this adaptation is that the fluid
removes polar bodies from the surface of the sperm
activates the egg nucleus so that it begins to divide
acts as a transport medium for sperm
provides currents that propel the egg down the oviduct

Base your answers to next 2 questions on the diagrams and the information below.

Which organisms were produced as a result of fertilization?
A, B, and C, only
B and C, only
C and D, only
B, C, and D, only

Structures that function in the storage of food to be used by growing embryonic cells are indicated by
1 and 3
2 and 3
2 and 4
3 and 4

Base your answers to next 3 questions on your knowledge of biology and the information below.
A biologist cut a flap of ectoderm from the top of a developing embryo. He did not remove the piece of ectoderm but just folded it back. Then he cut out the mesoderm underneath and completely removed it. He folded the flap of ectoderm back in place. The ectoderm healed; however, a complete nervous system did not develop.

This experiment was most likely performed immediately after
cleavage
gestation
fertilization
gastrulation

This experiment interfered with the process of
differentiation
zygote formation
cleavage
ovulation

This experiment demonstrates that the
ectoderm is solely responsible for development of the nervous system
nervous system is destroyed during surgical operations
mesoderm influences the development of the nervous system
digestive enzymes have a major role in the development of embryonic layers

In a developing embryo, the mesoderm layer normally gives rise to
epidermal tissue
skeletal tissue
digestive tract lining
respiratory tract lining

What is the function of the placenta in a mammal?
It surrounds the embryo and protects it from shock.
It allows mixing of the maternal and fetal blood.
It permits the passage of nutrients and oxygen from the mother to the fetus.
It replaces the heart of the fetus until the fetus is born.

Key Idea 4—Reproductive Continuity: Answers and Explanations

3 Mitosis is the process by which two identical nuclei are formed. Mitotic cell division is usually followed by cytoplasmic division. A plant cell has a rigid cell wall. Division of the cytoplasm begins with the appearance of a cell plate between the two nuclei. The cell plate is composed of membrane fragments from the endoplasmic reticulum.
Wrong Choices Explained:
(1) Spindle fibers are elastic-like protein fibers. Chromosome movement is controlled by spindle fibers.
(2) In order for two nuclei to be identical, they must have the same number and kind of chromosomes. The chromosomes duplicate before the nucleus divides. The mitotic process is the same in both plant and animal cells.
(4) Cytoplasmic division, or cytokinesis, usually follows nuclear division in both plant and animal cells.
 

2 Chromosomes are structures in the nucleus. During mitosis, two cells with identical chromosomes are formed. Because the cell had 12 chromosomes, the daughter cells must also have 12 chromosomes.
Wrong Choices Explained:
(1) A cell with 24 chromosomes has twice the diploid number. The condition in which there are extra sets of chromosomes is known as polyploidy.
(3) A cell with 6 chromosomes has one-half the diploid number. Monoploid cells arise through meiosis.
(4) A cell with 4 chromosomes can only arise through a complete breakdown of the mitotic or meiotic process.
 

1 In asexual reproduction, new organisms are produced by a single parent. Asexual reproduction involves the mitotic process. The genetic material of the offspring is identical to that of the parent.
Wrong Choices Explained:
(2) Gametes are produced by sexually reproducing organisms.
(3) The fusion of sex cells (gametes) to form a zygote is characteristic of sexually reproducing organisms.
(4) Genetic variation among offspring is characteristic of sexually reproducing organisms. The process of meiosis through synapsis and segregation ensures new combinations of genetic material.
 

1 Gonads are sex glands. In these glands, gametes, or sex cells, are produced from primary sex cells that undergo meiosis, also known as reduction division. Male gonads are called testes, and female gonads, ovaries.
Wrong Choices Explained:
(2) Gametes are sex cells and not organs. Sex cells are specialized for fertilization.
(3) Kidneys are organs of excretion and are specialized for filtering metabolic wastes out of the blood. The nephron is the unit of structure and function in the kidney. Meiosis does not take place in kidney cells.
(4) Cytoplasmic organelles such as mitochondria, ribosomes, lysosomes, and endoplasmic reticula are not organs.
 

2 A gamete is a reproductive cell that must fuse with another gamete to produce a new individual. Sperm cells and egg cells are gametes. Fertilization is the fusion of an egg cell and a sperm cell. In land animals, fertilization occurs within the body of the female and is known as internal fertilization.
Wrong Choices Explained:
(1) External fertilization, the union of gametes outside the female’s body, occurs in animals that live in a watery environment. Fish and amphibians reproduce by external fertilization.
(3), (4) The question refers to reproduction in animals. Animal cells, including gametes, do not have cell walls.
 

4 Primary sex cells give rise to gametes. Gametes are formed by the process of meiosis. In meiosis, a diploid cell divides twice to form four monoploid cells. In humans the four gametes, which are identical in size, are known as sperm cells.
Wrong Choices Explained:
(1) Chromosomes occur in pairs. The diploid number of chromosomes is the full number of chromosomes of all the pairs. Meiosis is cell division in which the nucleus receives one member of each pair of chromosomes. The nucleus of an egg cell thus contains half the diploid chromosome number, or the monoploid number.
(2) In formation of the egg cell, the cytoplasm does not divide equally. One large monoploid cell, the egg cell, and three very small cells (polar bodies) are produced from one primary sex cell.
(3) The three small monoploid cells accompanying the egg cell are known as polar bodies. Polar bodies degenerate and do not function in fertilization.
 

1 The diploid chromosome number is represented as 2n, and the monoploid number as n. When two gametes in the n condition combine, a 2n cell is produced. Fertilization is the union of two gametes.
Wrong Choices Explained:
(2) Gamete formation reduces the chromosome number from 2n to n.
(3) Cleavage is mitotic cell division without growth. It is the process by which a fertilized egg cell becomes a multicellular embryo.
(4) Meiosis, or reduction division, reduces the chromosome number of diploid cells.
 

2 Follicles contain immature egg cells. The follicles are found in the ovary. FSH stimulates ovarian follicle development.
Wrong Choices Explained:
(1) ACTH stimulates the adrenal glands to produce cortisone. ACTH is secreted by the pituitary gland.
(3) Calcium metabolism is controlled by parathormone. The parathyroid gland secretes parathormone.
(4) Thyroxin secreted by the thyroid gland is the major regulator of the rate of oxidation. The hormones from the adrenal glands and the pancreas also play a role in the oxidation of glucose.
 

4 The menstrual cycle is a series of changes that occur within the female reproductive system. The events of the cycle prepare the uterus to receive an embryo. The lining of the uterus is built up. If the cycle is not interrupted, the egg is not fertilized and no embryo is formed. In the last stage of the cycle, the lining of the uterus disintegrates and is shed.
Wrong Choices Explained:
(1) Sperm cells are produced by the male.
(2) Ovulation (release of a mature egg) occurs midway through the menstrual cycle.
(3) Once a month the uterus is prepared to receive an embryo. What happens to the lining of the uterus depends upon presence or absence of an embryo. If an embryo is present, the uterus continues to develop and the menstrual cycle is interrupted.
 

2 It helps to make terrestrial life possible is the correct response. Internal fertilization, as its name implies, occurs within the body of the parent (usually female). The conditions in the female reproductive tract provide an ideal environment for the survival and pairing of gametes, helping to ensure that fertilization occurs successfully. This method of reproduction is especially helpful in the survival of terrestrial animal species, who live where harsh conditions (such as drying, heat, and cold) can easily damage or kill gametes released into the environment for external fertilization.
Wrong Choices Explained:
(1) Motile gametes (such as human sperm cells) are common in species employing both external and internal fertilization. Motility (ability to move) enables the sperm cells to swim toward the egg cell in either environment.
(3) Because of the dangers posed to fragile gametes in any environment, the presence of many eggs is characteristic of species employing external fertilization. Species using internal fertilization produce relatively few eggs in the reproductive process.
(4) In most species internal fertilization occurs within the body of the female, not that of the male.
 

4 Monoploid, monoploid, and diploid is the correct combination. Sperm cells and egg cells are monoploid (n) gametes formed during the process of meiotic cell division. A zygote results from the fusion of two monoploid nuclei in fertilization and so must be diploid (2n) in chromosome number.
Wrong Choices Explained:
(1), (2), (3) Each of these distracters contains an incorrect combination of choices (see above).
 

1 In the process of oogenesis, a single primary sex cell gives rise to a single monoploid egg cell and three nonfunctional monoploid polar bodies. The process of spermatogenesis yields four functional monoploid sperm cells for each primary sex cell. Therefore, a comparison of these two processes leads to the conclusion that, per primary sex cell, spermatogenesis yields four times as many gametes as oogenesis does.
Wrong Choices Explained:
(2), (3), (4) Each of these distracters contains a mathematical comparison that is not consistent with the explanation above.
 

3 The fluid surrounding human sperm cells acts as a transport medium for sperm. This fluid is known as semen. Its primary function is to provide a protective watery medium for sperm cells as they enter the female reproductive tract.
Wrong Choices Explained:
(1) Removes polar bodies from the surface of the sperm is a “nonsense” distracter. Polar bodies are not associated with sperm production.
(2) Activates the egg nucleus so that it begins to divide is not a function of semen. The egg is stimulated to divide by the act of fertilization. Semen is not directly involved in this process.
(4) Provides currents that propel the egg down the oviduct is not a function of semen. Cilia that line the oviduct are responsible for establishing fluid currents that both carry the egg downward toward the uterus and carry sperm upward toward the ovary. Semen is not directly involved in this process.
 

1 Fertilization is one of the processes in sexual reproduction. Sexual reproduction is the method of reproduction in the bean plant, chimpanzee, and chicken (A, B, and C, only). The ameba reproduces asexually by binary fission.
Wrong Choices Explained:
(2) The bean plant (B) was omitted in this choice.
(3) The ameba (D) is an incorrect answer. Both the bean (A) and the chimpanzee (B) were omitted in this choice.
(4) The bean plant (A) was omitted and the ameba (D) is an incorrect answer.
 

3 The structures that function in the storage of food for the embryonic cells are labeled 2 and 4. Structure 2 is the cotyledon of the seed. The yolk sac is structure 4.
Wrong Choices Explained:
(1) Structure 3 refers to the wall of the uterus. The embryo of a chimpanzee is nourished through the placenta, not the uterine wall. Structure 1 is the leaf of the embryo bean plant.
(2) Although structure 2 is a correct answer, structure 3 is incorrect.
(4) Although structure 4 is a correct answer, structure 3 is incorrect.
 

4 The experiment was performed after gastrulation. Gastrulation is a stage in embryonic development that gives rise to three germ layers of cells. The three germ layers are the ectoderm, mesoderm, and endoderm.
Wrong Choices Explained:
(1) Cleavage is a stage of embryonic development in which the zygote undergoes rapid mitotic divisions. The final result is a ball of cells.
(2) Gestation is a prebirth period. It is the time a developing embryo spends in the uterus.
(3) The union of a sperm cell nucleus with an egg cell nucleus is called fertilization. The result of the process is a zygote.
 

1 The experiment interfered with the development of a nervous system. The development of special tissues and organisms is known as differentiation.
Wrong Choices Explained:
(2) Zygote formation must occur before an embryo can develop.
(3) The process of cleavage provides the embryo with hundreds of undifferentiated cells.
(4) Ovulation is the release of an egg from the ovary.
 

3 The experiment demonstrates that the development of the nervous system is influenced by the presence of the mesoderm. The nervous system does not develop when the mesoderm is removed.
Wrong Choices Explained:
(1) If the ectoderm was solely responsible for the development of the nervous system, the nervous system would have developed after the mesoderm was removed.
(2) There was no nervous system present when the surgery was performed.
(4) The experiment was not concerned with the reasons for the development of the embryonic layers.
 

2 Each of the three germ layers of the embryo is responsible for the development of the systems of the body. The skeletal system develops from the mesoderm. The muscle system, circulatory system, and excretory system also evolve from the mesoderm.
Wrong Choices Explained:
(1) Epidermal cells form the outer covering or skin of the body. The skin and nervous system develop from the ectoderm.
(3), (4) The linings of the digestive and respiratory tracts develop from the endoderm.
 

3 The placenta is an area of spongy tissue in the uterus. It is very rich in blood vessels. The placenta functions as a respiratory and excretory organ of the fetus. Vital materials are exchanged between the capillaries of the fetus and the capillaries of the mother.
Wrong Choices Explained:
(1) The amnion is a fluid-filled sac surrounding the embryo. The fluid bathes the cells of the fetus and protects it against shock.
(2) The circulatory systems of the mother and the fetus are separate from each other. Blood does not flow from one system into the other.
(4) The embryo develops its own heart. The placenta provides an area for the diffusion of materials into and out of the fetus.