Chapter 14: Animal Reproduction and Development

Most of what you need to know about reproduction and development involves processes that have already been discussed in earlier chapters but can serve as additional examples that you can cite to show your understanding of a concept.

Eggs and sperm production is an example of meiosis.
Its regulation is an example of negative and positive feedback mechanisms.

An example of cell communication is the highly coordinated series of cell divisions and programmed cell deaths.

The AP exam doesn't require you to know the names of specific stages of embryo development.

Male and female mammals are distinguished by their primary and secondary sex characteristics.

The testes in males and females are examples.
Deer antlers, lion manes, and peacock tails are examples of secondary sex characteristics in nonhumans.
Secondary sex characteristics can be used to indicate sexual maturity or sexual readiness, to attract or locate mates, or to compete for females.

Only the primary oocytes progress to prophase I.

They remain at this stage until puberty, at which time one primary oocyte during each menstrual cycle (averaging 28 days) continues its development through the remainder of meiosis I.
The cytoplasm is concentrated in one of the daughter cells.
The polar body can continue with meiosis II and divide into two polar bodies, but they eventually die.

Adequate amounts of stored food, as well as mitochondria, ribosomes, and other cytoplasmic organelles, will be available for the developing embryo if the cytoplasm is separated in one viable secondary oocyte and at the end of meiosis II, one egg.

The sperm contributes very little at fertilization.

If it is fertilized by a sperm as it moves through the oviduct, the secondary oocytes will complete meiosis II and produce an egg that combines with the chromosomes contributed by the sperm.

The spermatozoa are stored until needed in the epididymis, a coiled tube attached to each testis.

Should an egg become fertilized, the uterus should be prepared to implant it.

The activities of the ovary and uterus are coordinated by negative and positive feedback from the hypothalamus, anterior pituitary, and gonadotropin releasing hormone.

The levels of hormones in the blood are monitored by the hypothalamus.

The follicle is growing.

The oocyte and the follicle are stimulated by FSH.

Estradiol is produced by the follicle.

Estradiol is produced from the follicle.

There is ovulation.

Estradiol and progesterone are produced by the corpus luteum.

The endometrium is growing.

The endometrium is the lining of the uterus.
It is prepared for the implantation of a fertilized egg with the help of tissue and blood vessels.

The endometrium is falling apart.

Growth of the endometrium is no longer supported, and it is no longer able to function during menstruation.

The embryo sustains the uterus.

Human chorionic gonadotropin is produced by the embryo if it is implanted.
The endometrium is maintained by the production of estrogen and progesterone from the corpus luteum.
The embryo would be aborted if there was no hCG.
Fetal hormones are replaced by hormones produced by the placenta.
The embryo is able to maintain the pregnancy.

The hormones that regulate the female reproductive cycle are the same hormones that regulate the male reproductive cycle.

The Leydig cells are located between the seminiferous tubules and produce testosterone and other male sex hormones.
Sertoli cells play a role in the development of sperm.
During the reproductive life of the male, hormone and gamete production are constant.

The development of the secondary sex characteristics in males and females is stimulated by testosterone and estrogen.

The sperm penetrate the secondary oocytes.

Each of the resulting cells contains less cytoplasm than the original.

The 959 cells in an adult are all traced back to the egg.

All of the cells that were created during embryonic development have the same chromosomes and DNA sequence.

It is possible for a cell to be divided into equal parts.

Cells acquire variations based on the orientation of the cleavage.
If daughter cells can individually complete normal development, a cleavage is not indeterminate.
If separated from other cells, daughter cells can't develop into a complete embryo.
Their program is limited to the production of cells that contribute to a part of the embryo.
Cells are more likely to be determined later in the developmental sequence if the cytoplasmic influences are narrowed by each successive cell division.

The egg hasplasmic material in it.

The quality of the daughter cells will vary when the egg is divided.

Substances unique to certain daughter cells may promote the expression of genes specific to the development and differentiation of that cell.

In a famous experiment, Hans Spemann separated the cells that formed during early cleavages and showed that only a portion of the gray crescent was needed to make a normal frog.

Morphogen gradients occur across the developing embryo.

In each cell, the morphogens act as transcription factors, which are specific to that part of the embryo.

The influence of one cell over another is called embryonogenesis.

Cell-to-cell communication can be done by way of diffusible chemicals or interaction between cell surfaces.

Communication leads to the expression of genes.

The blastopore leads to the inside of a sphere of cells.

The notochord, a stiff strip of cells that provides support in the developing embryo, was discovered by Spemann.
A second notochord developed when Spemann transplanted a second lip into the embryo.
The lip is an organizer.

The inducer is a signaling molecule.

The production of transcription factors that bind to a promoter on the DNA is activated in the cells closest to the anchor cell.
When translated, this causes the production of an mRNA that stimulates the differentiation of the cell into a cell that is involved in egg laying.
Cells farther away from the anchor cell become skin cells.

Some cells that are produced during development are not destined to be a part of the multicellular organisms.

During the assembly of the organisms, some cells are deliberately destroyed.

The process of destruction begins with an external signal.

The genes break down the proteins.

The signaling pathway in neighboring cells is stimulated by the release of chemicals by the dying cell.

During the early stages of development, the spaces between fingers and toes are connected.

During normal embryonic development, the cells that make up the webbing begin to die, allowing the fingers and toes to form separate digits.

In ducks and other animals where the webbing is still present, the genes that initiate the process of apoptosis are not activated.

The expression of genes is turned on or off by external and internal signals.

Genes are expressed when their genes are transcribed.
If theRNA is an messenger RNA, it can produce a different type of molecule that contributes to the specialization of the cell.
Different tissues combine to form organs and a multicellular organisms.

The histone packaging is held more tightly by the histone groups.

Cell lines have specific sequences of methylated DNA that are maintained.
The fate of a cell line is determined after the occurrence of methylation.
There have been errors in cancer cells.

The expression of genes is influenced by the influence of theseRNAs.

Fruit flies have genes that drive the formation of body segments and antennae.

Homeotic genes have features.

It codes for a long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long, long,

The timing of the body parts is correlated with the order of the genes.

A review of the material presented in this chapter is provided by the questions that follow.

They can be used to evaluate how well you understand the concepts.
AP multiple-choice questions are often more general, covering a broad range of concepts.
The two practice exams in this book are for these types of questions.

Four possible answers or sentence completions are followed by each of the following questions or statements.

The one best answer or sentence is what you choose.

You can use the following key for questions.

The answer in the key can be used more than once or not at all.

This hormone is produced by Follicles.

The questions that follow are typical of an entire AP exam question or just that part of a question that is related to this chapter.

There are two types of questions on the AP exam.

It takes about 20 minutes to answer a long free-response question.
Sometimes they offer you a choice of questions to answer.
6 minutes is the time it takes to answer a short free-response question.
diagrams can be used to supplement your answers, but a diagram alone is not adequate.

The menstrual cycle begins again when the estrogen and progesterone production stops because of the decline in LH and FSH.

In two or three sentences, explain how the endometrium is maintained if the corpus luteum is no longer viable and secreting estrogen andprogesterone.

Cells burst and release their contents when they die from injury.

Explain how programmed celldeath is different in two or three sentences.

Oogenesis starts during the early stages of development.

When the production of all eggs stops, the process is suspended.
One secondary oocyte is produced each month at puberty.
The eruption of a secondary oocyte at the end of meiosis I leads to ovulation.
Meiosis II occurs if the secondary oocyte is penetrated by a sperm.

There is a surge in LH that causes ovulation from a follicle.

The endometrium is the inside lining of the uterus.

Estradiol and prostaglandins are produced by the follicle.

The corpus luteum produces hormones after ovulation.

Interstical cells in the testes produce testosterone and other androgens.

The anterior/posterior and dorsal/ventral axes of the embryo are established by the distribution of morphogens.

The strength of the morphogens in a particular cell signals to the cell where it is relative to the rest of the embryo and stimulates gene expression appropriate to the specific cell.

The process of mishing involves attaching groups of amino acids to histones that serve to pack DNA into strands.

It is more difficult for the DNA to be untangled because of the methyl groups.

Human chorionic gonadotropin is produced by the implanted embryo.

The corpus luteum is maintained by the hCG, which allows it to continue its production of hormones.
The hormones are produced later during development.

Apoptosis is a process in which proteases break down cellular structures.

Fragments of these structures are packaged inside the cell wall.

Both sexes have the same hormones that regulate the production of gametes.

For both males and females, the hypothalamus monitors hormone levels in the blood and releases gonadotropin releasing hormone, which stimulates the anterior pituitary to produce follicle stimulating hormone and luteinizing hormone.
The testicles in males and females are stimulated by these hormones.
Sex hormones are produced in both males and females by LH.
The development of the gametes is stimulated by FSH.
In males and females, it stimulates the development of an oocyte in a follicle.
Positive and negative feedback loops in both males and females establish levels of hormones that maintain the constant production of sperm in males and the release of eggs in females.

Gametogenesis in females begins with an oogonium and ends with a single viable egg and three nonfunctional polar bodies.

By producing a single egg, the potential embryo gets most of its nutrition.
Each spermatogonium divides to produce four viable sperm, each containing an equal amount of cytoplasm, in males.
Gametogenesis in females begins during embryo development, stops at birth, and begins again at puberty, releasing one egg a month until menopause.
Gametogenesis begins at puberty in males.

The menstrual cycle is regulated by the female reproductive cycle, which also regulates the endometrium.

The feedback loops are more complex in females than in males.

The beginning of the menstrual cycle can be signaled by low levels of estrogen.

The response to gonadotropin releasing hormone is initiated by the hypothalamus.
GnRH stimulates the anterior pituitary to release hormones.
FSH stimulates the development of the egg within the follicle as part of the ovarian cycle.
In a positive feedback reaction to rising estrogen levels, the anterior pituitary produces more LH.
The release of the egg from the follicle is caused by a spike of LH in the middle of the cycle.
Estradiol and progesterone are produced by the corpus luteum after ovulation.
The hormones regulate the menstrual cycle by stimulating the endometrium.
A negative feedback response causes the anterior pituitary to stop making FSH and LH because of high levels of progesterone.
The endometrium is removed because the follicle stops producing hormones.

If the egg is fertilized and implants into the endometrium, the cells from the developing embryo will produce human chorionic gonadotropin, which will keep the endometrium functioning.

Both questions require a discussion of the reproductive processes, but their focuses are different.

In answering the first question, you need to state the similarities and differences between males and females.
The details of hormone regulation are not enough to address the question.
The details of hormoneregulation and feedback loops are exactly what you need to discuss with females.
The two parts of the answer to the first question are clearly indicated.

Explain the various mechanisms that influence embryonic development, including mechanisms of gene expression.

You can cite the effects of genes on fruit flies and the influence of egg cytoplasm.
The subject of development is one of the few areas where you may need to give historical information.