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Science grade 9 > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

What are the secondary sexual characteristics in males? Why are they secondary?

A

They include growth spurts, facial, underarm and pubic hair and the deepening of the voice. They distinguish males from females but don’t have a role in reproduction.

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2
Q

What is puberty and when does it start in males?

A

It is when males mature and gain the ability to reproduce. It begins between the ages of 12 to 18, when hormones are released from the pituitary gland in the brain and stimulate the testes to produce the male sex hormone testosterone.

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3
Q

What are the primary sexual characteristics in males?

A

They include reproductive organs that produce sperm and allow them to reach the female.

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4
Q

Explain the structure of the sperm.

A

Sperm is divided into three sections; the head, middle, and tail. The head is composed of a capsule which contains chemicals that allow it to penetrate the egg. The head also has a haploid nucleus which has 23 chromosomes. The middle piece has mitochondria that provides energy for the sperm cell. The tail (flagellum) helps it move. The sperm is streamlined and built to move.

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5
Q

What do the testes do and what are they surrounded with?

A

They are outside the abdominal cavity and are enclosed in a protective sac called scrotum. The function of the testes is to produce and nourish developing sperm. They also produce testerone.

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6
Q

Where are the seminiferous tubules located and what is their function?

A

They are a mass of coiled tubes inside each testis. They contain diploid cells which undergo meiosis to produce haploid sperm cells.

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7
Q

Where are mature sperm cell stored?

A

They are stored in the epididymis above the testes.

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8
Q

What is the path of a mature sperm cell?

A

They travel out of the body through two tubes. Vas deferens is a tube that carries the sperm to the urethra. The urethra, which is located in the penis, transports the sperm outside the body. It enters a female during sexual intercourse. The sperm cells and other fluids are ejaculated outside the penis when inside female.

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9
Q

What is the function of the urethra?

A

It is part of both the excretory and reproductive system. It carries both urine and sperm outside the body at separate times.

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10
Q

How does seminal fluid help sperm?d

A

It provides sugar for energy, protects the sperm from acidic female reproductive tract, and provides fluid for swimming.

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11
Q

What are the male accessory glands and what are their functions?

A

The seminal vesicles, prostate gland and cowper’s glands are all accessory glands that secrete seminal fluid.

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12
Q

Why do sperm need male accessory glands?

A

Sperm needs a fluid to swim in and nutrients to provide energy for the journey. The accessory glands secrete seminal fluid, which acts as a substance for sperm to swim in. Seminal fluid also provides sugar as energy and protection from the acidic reproductive tract in a female.

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13
Q

What it semen composed of?

A

It is made of sperm and seminal fluid.

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14
Q

How many sperm are produced in a single day?

A

200 to 300 million sperm are produced in a single day.

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15
Q

How long does it take for sperm to mature?

A

It takes 65 to 75 days for sperm to mature.

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16
Q

How do sperm cells mature?

A

Sperm cells start as diploid cells on the insides surface of seminiferous tubules. They increase in number by undergoing meiosis to become haploid cells. Because they need a lot of energy to mature, special support cells povide nourishment to developing sperm. When sperm reach the centre of the tubule, they are almost mature. Sperm cells then move to the epididymis where they finish maturing.

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17
Q

What happens to the sperm that don’t reach the egg?

A

They die and are broken down by white blood cells. New sperm cells replace the old ones.

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18
Q

Can sperm be produced in old age?

A

Yes, although the number of mature sperm decreases.

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19
Q

What are the secondary sexual characteristics in females?

A

They include the development of mammary glands, the growth of underarm and pubic hair, the widening of the hips, and the maturing of sexual organs.

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20
Q

When does puberty begin for females?

A

It begins between the ages 10 to 12.

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21
Q

Where do eggs mature? Where are they released?

A

They mature in the ovary, and are released into the oviduct monthly.

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22
Q

How many eggs do females start with at birth?

A

They start with about two million eggs, though most will degenerate, leaving 400 000 at puberty. Old eggs are not replaced by new ones, unlike sperm.

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23
Q

What hormones are produced in the female reproductive system and what are their functions?

A

The hormones estrogen, progesterone, and prolactin are produced. Estrogen stimulates the development of the secondary sexual characteristics. Progesterone stimulates the endometrium to develop in preparation for the fertilized egg. Also, progesterone prevents any other eggs from maturing and stimulates for the mammary glands to develop more milk ducts during pregnancy. Prolactin causes for milk to be produced in mammary glands after birth.

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24
Q

What is the path of the egg?

A

The egg is first released from the ovary into the oviduct, where it travels to the uterus. In the oviduct, wave like muscular contractions, called peristalsis, and cilia help move the egg. If the egg is not fertilized by the time it has reached the uterus, it will be flushed out through menstruation. It will go out through the cervix and then the vagina.

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25
Q

What is menstruation?

A

It is the shedding of the endometrium, which is the lining of the uterus. It is rich in blood vessels, nutrients, and mucus.

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26
Q

What is the flow phase?

A

It’s the first phase of menstruation, in which the endometrium is shed.

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27
Q

What is the follicular phase?

A

It is the phase in which a new follicle is developed, the endometrium reforms, and estrogen is produced.

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28
Q

What is ovulation?

A

It’s when an egg is released from the ovary.

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29
Q

What is the luteal phase?

A

In the luteal phase, the empty follicle develops into the corpus luteum. The endometrium thickens, and estrogen and progesterone are produced.

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30
Q

How long is each menstrual cycle?

A

Each cycle lasts for approximately 28 days, though it can vary between 20 to 40 days.

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31
Q

What is menopause and when does it occur?

A

It is the permanent end of the menstrual cycle. It occurs between the ages 40 and 50.

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32
Q

Where does fertilization take place?

A

It takes place in the oviduct.

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33
Q

What organ receives the embryo?

A

The uterus recieves the embryo.

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34
Q

What is a female accessory gland?

A

Mammary glands are female accessory glands. They contain milk producing lobes to feed the baby.

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35
Q

What is the size of an zygote?

A

It is 0.1 mm in diameter.

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36
Q

How many sperm are needed to ensure fertilization?

A

Several million sperm are needed to ensure fertilization.

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37
Q

How many sperm reach the oviduct and how many fertilize the egg?

A

100 sperm reach the egg but only one fertilizes it.

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38
Q

What happens after a single sperm penetrates the egg?

A

The egg releases a protein that prevents other sperm from penetrating. The cell membranes and the nuclei of the egg and sperm fuse to produce a zygote.

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39
Q

When is a zygote called embryo?

A

A zygote is called an embryo when it begins dividing in oviduct and is implanted into the uterus by the end of the first week.

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40
Q

What is the period of pregnancy?

A

It takes place over 9 months divided into 3 trimesters of 3 months.

41
Q

What are the signs of pregnancy? What confirms it?

A

Signs of pregnancy are no menstruation, enlarged breasts and nausea. A blood test can confirm it.

42
Q

Explain the first trimester.

A

The first trimester starts at fertilization and ends after 3 months. The zygote begins dividing in the oviduct and becomes an embryo when implanted into the uterus by the end of first week. After implanting, a sac forms around it and is filled with amniotic fluid. By the fourth week, the brain and nervous system are developing, and the heart is beating. The beginnings of eyes, ears and nose are noticeable. Limb buds and a tail are visible. All cells develop different structures and functions. By the end of eight week, the embryo now has beginnings of all organs and is called a fetus. By the end of the 3rd month, muscles and bones are forming. The fetus can flex their arm and leg muscles, as well as hiccup. Their heart is beating and blood is circulating. Their head is half the size of their body.

43
Q

By the end of 4th week, how big is the embryo?

A

It is 500 times bigger than the zygote.

44
Q

When does an embryo change into a fetus?

A

It is called a fetus when it has the beginnings of all organs.

45
Q

What is the size of the fetus in the first trimester?

A

The fetus is 12 cm long and it’s mass is 50 g.

46
Q

What is a birth defect?

A

A birth defect is a structural or physiological problem in the fetus before birth.

47
Q

When is a fetus most affected by birth defects?

A

It is most vulnerable during the first trimester.

48
Q

At what stage of pregnancy can a fetus’s gender be determined and why?

A

The gender can be determined during the first trimester because the sex organs are forming.

49
Q

What are the placenta and the umbilical cord?

A

The placenta is like a disk which grows 20-30 cm in diameter. It contains blood vessels from both the mother and fetus. Nutrients and oxygen from the mother diffuses into the fetus’s blood. The fetus’s circulatory system is connected to the placenta by the umbilical cord. The umbilical cord transports nutrients and oxygen and carries wastes away.

50
Q

Where does a fetus get nutrition from before birth?

A

It gets its nutrition from the mother through the placenta and umbilical cord.

51
Q

Explain the second trimester.

A

In the second trimester, the fetus experiences intense growth. It grows from 8 to 30 cm by the end of it. The heartbeat of the fetus can be detected and it is now sucking and swallowing amniotic fluid, which will be excreted in urine. The mother’s abdomen is now swelled up, and she can feel the movement of the fetus as its arms and legs develop. At the end of the second trimester, the fetus resembles a tiny infant. Their fingers and toes have elongated. Their facial features are more developed and eyelashes are visible. They are now covered with fine hair. They practice breathing, though no gas exchange occurs.

52
Q

Explain the third trimester.

A

During the third trimester, the fetus puts on most of its mass. The organ systems are functioning properly. The fetus has sleeping and waking patterns and reacts to stimuli from the outside world. The brain is developing rapidly. The bones are developed but still soft. The eyelids are open. The fetus fills the uterus and the mother’s belly may undulate as the baby changes position. The fetal hair disappears. The fetus turns so that their head is pointing down. The lungs continue to mature right up to birth.

53
Q

Explain the process of birth.

A

First, the mother goes through labour, then the cervix begins to open up. The membrane surrounding the baby is forced into the birth canal. Then, the amniotic membrane breaks and the amniotic fluid lubricates the canal. Once the cervix has widened to 10 cm, uterine contractions push the baby’s head into the birth canal. After the baby’s head and shoulders, the rest of the body slides out easily.

54
Q

What is labour?

A

It is the contraction of the muscles in a mother’s uterus. They happen every 15 to 20 minutes, and last for at least 40 seconds.

55
Q

What is the birth canal?

A

The birth canal is the vagina.

56
Q

What happens when stem cells undergo cell division?

A

The daughter cells with either stay the same or begin differentiating into types of specialized cells. As the embryo grows, stem cells lose their ability to grow into all types of specialized cells and they can only be found in certain tissues.

57
Q

What are stem cells?

A

They are unspecialized cells that have the ability to reproduce themselves.

58
Q

What is differentiation?

A

It is the process of growing from unspecialized cells into many different specialized cells.

59
Q

Why are scientists interested in stem cells?

A

Scientists are interested in stem cells because of their ability to differentiate into different types of cells. This could be used for new technology (regrowing limbs).

60
Q

What is the difference between fraternal and identical twins?

A

Fraternal twins occur when more than one egg is released at the same time from the ovary. Both are fertilized by different sperm. Each has its own placenta and different DNA. Identical twins occur when one fertilized egg splits at the zygote or embryo stage. After cell division, each daughter cell develops into an embryo but shares the same placenta. They are of same gender because they have the same DNA.

61
Q

What happens to the placenta and umbilical cord after birth?

A

The placenta (or “afterbirth”) is pushed out of the uterus. The umbilical cord is cut and tied to prevent bleeding after the baby starts breathing on their own. The belly button is the scar from the umbilical cord.

62
Q

What is a karyotype?

A

It is the arrangement of an organism’s chromosomes from one body cell.

63
Q

What are the steps of making a karyotype?

A

The steps of making a karyotype are to use a microscope to take pictures of the condensed chromosomes during metaphase, magnify the pictures and cut out individual chromosomes, and match up homologous pairs by shape and size.

64
Q

What are sex chromosomes?

A

They are chromosomes that determine the gender of an individual. They are called the X and Y chromosomes. They control primary and secondary sexual characteristics. The X chromosome is larger than the Y chromosome.

65
Q

Which sex chromosomes are in females and males?

A

Females have two X chromosomes. Males have one X and one Y chromosome.

66
Q

What happens during meiosis in males?

A

It produces four haploid sperm cells. Two of those would have X chromosomes and the other two would have Y chromosomes.

67
Q

What happens during meiosis in females?

A

It produces one haploid egg cell. It contains 23 chromosomes and the majority of the cytoplasm from the parent cell. The other three cells, each composing of a haploid nucleus eventually disintegrate.

68
Q

What is released when a mother’s water breaks during pregnancy?

A

Amniotic fluid is released.

69
Q

Which parent decides the gender of the offspring?

A

The father decides the gender of the offspring. It depends on which sperm fertilizes the egg, which will always have the X chromosome. If the sperm with the Y chromosome fertilizes the egg, the zygote will have XY chromosomes, making it male. If the sperm with the X chromosome fertilizes the egg, the zygote will be female.

70
Q

What are sex linked characteristics?

A

Certain traits that are controlled by the X chromosome are called sex linked characteristics. The X and Y chromosomes do not carry the same amount of genetic information (the Y chromosome is missing some), so some traits are are controlled solely by the genes of the X chromosome. Examples are baldness, colourblindness, and hemophilia.

71
Q

Why do sex linked characteristics occur more frequently in males than females?

A

They are expressed more frequently in males because they have one X and one Y chromosome, while females have two X chromosomes. Females have equal chances of getting genetic info from both chromosomes, but males can only depend on the X chromosome they have for some traits. There is a higher chance for males to get the traits.

72
Q

What is nondisjunction?

A

Nondisjunction occurs when the homologous chromosomes do not separate during meiosis. It produces gametes with wrong number of chromosomes. If one of the gametes coming together during fertilization has the wrong number of chromosomes, the zygote will have either too much or too little genetic material. In most cases the zygote doesn’t divide and dies.

73
Q

Does nondisjunction only occur with homologous chromosomes?

A

It does not only occur in homologous chromosomes. It can also occur with sex chromosomes, which leads to gametes being produced with either an extra sex chromosome or none at all. A gamete with a X chromosome can be produced with two X chromosomes.

74
Q

What is Down syndrome?

A

Down syndrome is a common disorder resulting from a zygote dividing while it has 47 chromosomes instead of dying. People with down syndrome have three copies of chromosome 21 instead two (a pair). They have similar facial features, mild to severe mental disabilities and physical disorders.

75
Q

What is Turner syndrome?

A

Turner syndrome occurs in females when they are born with one X chromosome. One of the gametes is missing the sex chromosome. Reproductive organs in females with Turner syndrome don’t develop at puberty therefore they don’t menstruate or reproduce.

76
Q

What is a Trisomic female?

A

A Trisomic female has an extra X chromosome. Their reproductive organs develop so they can reproduce, unlike females with Turner syndrome. Trisomic female are taller and skinnier than average.

77
Q

What is Klinefelter syndrome?

A

The Klinefelter syndrome occurs when males are born with two X chromosomes and one Y chromosome. One of the gametes had an extra X chromosome which meant less testosterone was produced so males diagnosed with Klinefelter syndrome cannot father children.

78
Q

What diseases are caused by mutated genes?

A

Cystic fibrosis and Huntington’s disease are examples of diseases caused by mutated genes.

79
Q

When does an embryo change into a fetus?

A

An embryo is called a fetus when it has the beginnings of all organs.

80
Q

What is cystic fibrosis?

A

Cystic fibrosis’s main symptom is a buildup of mucus in lungs, which develops in childhood. This makes breathing difficult and most people do not live beyond their twenties.

81
Q

What is Huntington’s disease?

A

Huntington’s disease is the death of nerve cells. Symptoms of it are personality changes, the loss of memory and the loss of muscle control. These symptoms do not develop until the mid-thirties or forties.

82
Q

What is the purpose of prenatal procedures?

A

The purpose of prenatal procedures is to diagnose genetic disorders and gender.

83
Q

What is an ultrasound?

A

Ultrasounds are used to detect abnormalities in the fetus. They use high frequency sound waves to create 3D images called sonograms. Ultrasounds can also determine the gender of the fetus.

84
Q

What is amniocentesis?

A

Amniocentesis is when a doctor uses a syringe to remove amniotic fluid from the sac surrounding the fetus. In the amniotic fluid are cells that contain the chromosomes of the fetus. These cells are treated, allowed to reproduce and then placed on a microscopic slide. The picture of its genetic information is used to produce a karyotype. Amniocentesis is done around the 20th week of pregnancy. It is a common procedure to view the chromosomes of a fetus in high risk pregnancies. It is used to determine spinal cord defects. Levels of certain chemicals in the amniotic fluid can be used to determine if the lungs are mature.

85
Q

What is chorionic villus sampling?

A

Chorionic villus sampling is when a catheter is inserted through the vagina into the uterus in order to obtain sample cells of the placenta. This methods collects more fetal cells than amniocentesis. The sample is taken between 8 to 12 weeks of pregnancy The purpose is to determine the karyotype of fetus.

86
Q

What is egg collection?

A

Egg collection is the collection of eggs by a suction device. An optical device called laparoscope is first inserted into the abdominal cavity to view the ovary. The eggs are then put in a laboratory and tested for genetic disorders from the mom.

87
Q

What are chorionic villi?

A

Chorionic villi are extensions of the chorion, the layer of placenta that connects to uterus.

88
Q

What are considered high risk pregnancies?

A

A pregnancy is considered to be high risk if the mother is over the age of 35, if she has already had a child with down syndrome or spinal cord or brain defects, if either parent has a genetic disease in the family, or if the mother has had a miscarriage before.

89
Q

When does a miscarriage occur?

A

Miscarriages occur when a fetus is involuntarily expelled from the womb before it has developed enough to survive on its own. It can be caused by accidents, illness and birth defects in the fetus.

90
Q

What are a few reasons why many couples can’t reproduce?

A

Some reasons why couples can’t reproduce are that the male may not have enough healthy sperm, oviducts of the woman may be blocked or not functioning properly, or there may not be enough of the proper hormone at the correct time in the woman’s cycle.

91
Q

What are a few reproductive technologies that can be used to treat infertility?

A

A few reproductive technologies that can be used to treat infertility are fertility drugs, artificial insemination, intrauterine insemination, gamete intrafallopian transfer, in vitro fertilization, and intracytoplasmic sperm injection.

92
Q

What are fertility drugs?

A

Fertility drugs stimulate the production of hormones that affect a female’s follicles. More eggs mature and are released from ovary. This increases the chances of conception. The side affect is that there is an increased chan e of having multiple births like twins and triplets. Most people are prescribed to fertility drugs when they are undergoing other conception enhancing procedures.

93
Q

What is artificial insemination?

A

Artificial insemination is one of the solutions for low sperm counts. This procedure involves putting the sperm into the female WITHOUT sexual intercourse. The sperm is collected overtime or from a donor, then artificially inserted into the vagina.

94
Q

What is intrauterine insemination?

A

This technology’s purpose is to ensure that a large number of sperm reaches the egg (many sperm die when travelling from the vagina to the oviducts). The sperm is collected from the male and placed directly into the female’s uterus. It is placed high up in the uterus at the time of ovulation.

95
Q

What is the difference between artificial insemination and intrauterine insemination?

A

They happen in different parts of the female reproductive system. Artificial insemination is done in the vagina but intrauterine insemination is done in the uterus.

96
Q

What is in vitro fertilization?

A

In vitro fertilization is when fertilization takes place outside the female’s body and in a Petri dish. Follicles containing the immature eggs are removed from the female’s ovaries. Once the eggs have matured, sperm cells are added. After fertilization takes place, the embryo is reinserted into the mother’s uterus at the right time of the menstrual cycle. Usually many embryos are inserted and multiple births occur. The embryo may be implanted into a different female if the birth mother can’t carry the embryo.

97
Q

What are test tube babies?

A

Test tube babies are babies that are produced by in vitro fertilization.

98
Q

What are surrogate mothers?

A

Surrogate mothers are women who carry an embryo that doesn’t not belong to her. They are inserted when the biological mother’s uterus cannot accept embryos.

Science grade 9 (5 decks)

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