Chapter 27 - Human Development And Heredity

The primary germ layers refer to the three main layers of cells that form during embryonic development: the endoderm, mesoderm, and ectoderm. These layers give rise to different tissues and organs in the body. The endoderm forms the lining of the digestive tract and respiratory system, the mesoderm forms muscles, bones, and connective tissues, and the ectoderm forms the skin, nervous system, and sensory organs. The umbilical cord and placenta are structures that provide nutrients and support to the developing fetus.

A mutation refers to a change in the genetic code, which can result in a change in a particular trait. Mutations can occur in genes, which are segments of DNA that provide instructions for the development and functioning of organisms. Mutations can also occur in sex chromosomes or autosomes, which are types of chromosomes that carry genetic information. Therefore, the correct answer is mutation.

Sex chromosomes are responsible for determining the sex of an individual. In humans, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). These sex chromosomes carry genes that are specifically related to sexual development and reproduction. Traits that are controlled by genes located on the sex chromosomes are called sex-linked traits. In contrast, genes located on autosomes, which are non-sex chromosomes, are responsible for controlling other traits that are not related to sex determination. Therefore, the answer to this question is sex chromosomes.

The given answer, "fetus," is the correct answer because it refers to the stage of development of a baby from 9 weeks until birth. After the initial stages of being an embryo and zygote, the baby reaches the stage of a fetus, where its major organs and body systems continue to develop and mature. This stage is characterized by the baby's growth in size and the ability to move and respond to stimuli. Therefore, "fetus" is the appropriate term to describe the baby's name during this specific period of development.

Prolactin is the hormone that stimulates the mammary glands to produce milk. It is primarily responsible for initiating and maintaining lactation in mammals. During pregnancy, prolactin levels rise, preparing the mammary glands for milk production. After childbirth, prolactin levels remain high, promoting the production and release of milk for breastfeeding. This hormone plays a crucial role in the lactation process and is essential for providing nourishment to newborns.

A sex-linked trait refers to any trait that is carried on the X or Y chromosome. Unlike autosomes, which are non-sex chromosomes, the sex chromosomes determine the individual's sex. Genes, on the other hand, are segments of DNA that provide instructions for the development and functioning of an organism. Therefore, the correct answer is sex-linked trait, as it specifically refers to traits carried on the sex chromosomes.

A zygote is the result of the fusion of a sperm and an egg during fertilization. It is the earliest stage of development and marks the beginning of a new individual. The zygote undergoes cell division and differentiation, eventually forming an embryo. The trophoblasts are cells that surround the embryo and play a crucial role in implantation and the formation of the placenta. The fetus is the later stage of development, after the embryo, characterized by the development of organs and systems. Therefore, the correct answer is zygote, as it represents the initial stage of development after fertilization.

Parturition refers to the process of giving birth. It is the final stage of pregnancy where the fetus is expelled from the mother's body. The other terms mentioned in the question, such as trophoblasts, embryo, and primary germ layers, are unrelated to parturition. Therefore, the correct answer is parturition.

A gene is a segment of a DNA strand that carries the code for a specific trait, such as eye color. Genes are responsible for transmitting hereditary information from parents to offspring and determine the characteristics and traits of an organism. They are located on chromosomes, which are thread-like structures found in the nucleus of cells. Genes control the production of proteins, which in turn influence the development and functioning of cells and tissues.

Aldosterone is a hormone that is responsible for stimulating the reabsorption of sodium ions and expanding blood volume. During pregnancy, the body undergoes numerous physiological changes, including an increase in blood volume. Aldosterone helps in maintaining the increased blood volume by promoting the reabsorption of sodium, which in turn helps in retaining water and expanding the blood volume. Therefore, aldoesterone is the correct answer as it plays a crucial role in regulating blood volume during pregnancy.

Implantation refers to the process where the blastocyst, which is the early stage of development of the baby, attaches and burrows into the endometrium, which is the lining of the uterus. This is a crucial step for successful pregnancy as it allows the blastocyst to receive nutrients and oxygen from the mother's blood supply. Implantation typically occurs around 6-10 days after fertilization, and it marks the beginning of the development of the placenta and the formation of the embryo.

Oxytocin is the correct answer because it is the hormone involved in the milk let-down reflex. When a baby suckles at the breast, oxytocin is released from the posterior pituitary gland. This hormone causes the muscles around the milk ducts in the breast to contract, pushing the milk towards the nipple and allowing it to be released for the baby to consume. Oxytocin is also involved in other reproductive functions, such as uterine contractions during childbirth and bonding between mother and baby.

HcG, which stands for human chorionic gonadotropin, is the hormone that sustains the corpus luteum. The corpus luteum is a temporary endocrine structure that forms in the ovary after ovulation. It plays a crucial role in maintaining early pregnancy by producing progesterone, which is necessary for the development of the uterine lining and the support of the growing embryo. HcG is secreted by the developing placenta and stimulates the corpus luteum to continue producing progesterone until the placenta is fully developed and can take over hormone production.

Trophoblasts are cells that secrete hCG. hCG, or human chorionic gonadotropin, is a hormone that is produced by the placenta during pregnancy. It is responsible for maintaining the corpus luteum, which produces progesterone to support the pregnancy. hCG is also the hormone that is detected in pregnancy tests. Therefore, trophoblasts play a crucial role in early pregnancy by secreting hCG.

Fertilization refers to the process where a sperm cell and an egg cell combine to form a zygote. This is the initial step in the formation of a new individual. After fertilization, the zygote undergoes cell division and develops into an embryo. Implantation occurs after the embryo travels down the fallopian tube and attaches itself to the lining of the uterus. Therefore, fertilization is the correct answer as it accurately describes the event of the sperm and egg coming together to form a zygote.

The umbilical cord is the correct answer because it is the baby's lifeline and contains the umbilical blood vessels. The umbilical cord connects the baby to the placenta, allowing nutrients and oxygen to pass from the mother to the baby and waste products to be removed. It is through the umbilical cord that the baby receives essential nutrients and oxygen for growth and development during pregnancy.

Human chorionic gonadotropin (hCG) is a hormone that is produced during pregnancy. It plays a crucial role in maintaining the corpus luteum, which is the structure that forms in the ovary after the release of an egg. The corpus luteum produces progesterone, which is necessary to support the early stages of pregnancy. If the corpus luteum is not maintained, it will degenerate and progesterone levels will drop, potentially leading to a miscarriage. Therefore, hCG ensures the continued production of progesterone by maintaining the corpus luteum, supporting the development of the embryo.

The correct answer is "refers to the pre-embryonic cluster of cells." This is because the morula is a stage in embryonic development where the fertilized egg undergoes several cell divisions and forms a cluster of cells. It occurs before the blastocyst stage and is characterized by a solid ball of cells. This cluster of cells will eventually differentiate and develop into the various tissues and organs of the embryo.

Autosomes are pairs of chromosomes that are not involved in determining an individual's sex. In humans, there are 22 pairs of autosomes, numbered from 1 to 22. These chromosomes contain the majority of an individual's genetic information, including genes that determine various traits and characteristics. Sex chromosomes, on the other hand, determine an individual's sex and are not considered autosomes. Therefore, the correct answer is autosomes.

Hcg, or human chorionic gonadotropin, is a hormone that is secreted during pregnancy. It is produced by the placenta and plays a crucial role in maintaining the pregnancy during the early stages. The secretion of Hcg continues at a high level for about 2 months and then steadily declines as the placenta takes over hormone production. This hormone is responsible for various functions during pregnancy, including supporting the development of the fetus and regulating the production of other hormones.

Trophoblastic cells are responsible for the process of implantation in pregnancy. These cells play a crucial role in the attachment of the fertilized egg to the uterine wall, allowing for the development of the placenta. They help in the invasion of the uterine lining and facilitate the establishment of a connection between the maternal and fetal blood vessels. This process is essential for the proper nourishment and development of the growing embryo. Therefore, trophoblastic cells assist with implantation.

Implantation is the process by which the fertilized egg, known as the blastocyst, attaches itself to the uterine lining. This is a crucial step in pregnancy as it allows the embryo to receive nutrients and oxygen from the mother's body. Implantation typically occurs within the uterus and not in the fallopian tubes or ovaries. The morula, which is an early stage of embryonic development, is not responsible for implantation.

Oxytocin is a hormone that stimulates the contraction of the myometrium, which is the muscular layer of the uterus. This hormone plays a crucial role in labor and childbirth, as it helps to initiate and strengthen uterine contractions. Oxytocin is also involved in the release of breast milk during breastfeeding and is sometimes administered to induce labor or control postpartum bleeding. Therefore, out of the given options, oxytocin is the correct answer for the hormone that stimulates the contraction of the myometrium.

The umbilical cord is the structure that connects the developing baby to the placenta in the womb. It contains blood vessels that transport oxygen and nutrients from the mother to the baby, and remove waste products from the baby's bloodstream. The umbilical cord is responsible for supplying the baby with everything it needs to survive and grow during pregnancy, including oxygen, nutrients, and hormones. It also serves as a conduit for waste elimination, allowing the baby to excrete waste products into the mother's bloodstream for disposal.

The placenta is not responsible for nourishing the zygote as it matures into the morula. The placenta is formed after the morula stage and is responsible for providing nutrients and oxygen to the developing fetus. It also serves as a barrier between the mother and fetus, allowing for the exchange of waste products. The other options listed are all true or associated with the placenta.