Reproduction 2nd year Topic 6 Flashcards
1
Q
Mention the 2 types of reproduction
A
Asexual and sexual
2
Q
What is the difference between asexual and sexual reproduction?
A
asexual: one organism
sexual: 2 organisms male and female
3
Q
Mention some organisms which carry out these 2 forms of reproduction
A
Sexual: fish and mammals (higher invertebrates and all vertebrates)
asexual: bacteria and some plants (lower organisms)
4
Q
What happens if there is a lack of sexual reproduction?
A
If there is a lack of sexual reproduction, organisms are not going to adapt to their environment because they are not going to benefit from the genetic variation produced by sexual reproduction
5
Q
How does cell division occur in organisms who carry out asexual and sexual reproduction?
A
Asexual: mitosis/budding/vegetative reproduction
Sexual: meiosis – fertilization occurs
(how cell division occurs)
6
Q
Name some advantages of asexual and sexual reproduction
A
asexual: quick
less energy
sexual: genetic variation
unique and organism is protected
7
Q
Name some disadvantages of asexual and sexual reproduction
A
Asexual: no genetic variation, if the parent has a disease, the offspring has it too
sexual: requires more energy and the need for 2 mates
8
Q
When we speak about asexual and sexual reproduction in terms of evolution,which is the “better” one?
A
Sexual reproduction is better because there is a higher chance of genetic variation, which is fundamental to evolution.
Regarding asexual reproduction there is a very little chance of variation. Mutations in the genetic material can still occur but not as often as sexual reproduction
9
Q
How long does asexual and sexual reproduction take to complete?
A
Asexual: very short period of time
sexual : takes months to complete
10
Q
Which type of reproduction is involved in the formation or the fusion of gametes?
A
Sexual
Asexual does not occur
11
Q
Where does the unit of reproduction take place in both forms of reproduction?
A
asexual: whole parent body or or fragment
sexual: gametes
12
Q
How many offspring are produced in each types of reproduction?
A
asexual: 2 or more
sexual: one or more
13
Q
Mention 4 types of asexual reproduction
A
Budding
Vegetative propagation
Fragmentation
Fission
14
Q
Define fragmentation
A
Includes the parent colony being spontaneously broken down into fragments to produce new colonies ex: Spriogyra
15
Q
Define fission
A
The generation of offspring in unicellular organisms. They could produce 2 daughter cells (binary fission ex: amoeba) or more than 2 daughter cells
ex:Plasmodium
16
Q
Define vegetative propagation
A
asexual reproduction in plants involving the parent plant’s fragments or a special reproductive structure
17
Q
Define budding
A
The formation of a small clone on the mother organism. It could remain attached or get dislodged to produce another colony
18
Q
Why is genetic variation so present in sexual reproduction?
A
Because it involves 2 partners and due to the crossing ,and independent assortment of genes during meiosis
19
Q
True or false.
Sexual reproduction ensures genetic diversity which is fundamental in terms of evolution
A
True
Because it helps the adaption of environments
20
Q
How can sexual reproduction be divided?
A
Internal or External
21
Q
What is the difference between internal and external reproduction?
A
Internal: where there are specialized structures that could enter into each other: (to bring the sperm in proximity with the ovum)
External: when sperm and ova are released into the water and find each other through a process of chemotaxis
22
Q
What are some disadvantages of external fertilization?
A
Loss of energy and offspring due to predation or loss with currents
23
Q
What is another word for sex cells?
A
Gametes
24
Q
Where are gametes produced?
A
sex organs
25
Mention the male and the female gametes.
Male: sperm
Female: ova
26
Where are the male and the female gametes made?
Male: testes
Female:ovaries
27
What happens during fertilization?
The sperm will join up with the ovum to produce a zygote
28
What is a zygote?
The very first fertilized cell
29
What will the zygote mature as?
Embryo
30
Define fertilization
When the nucleus of the male gametes will fuse with the nucleus of the female gamates,resulting in the union of genetic material to produce a cell called the zygote
31
How many chromosomes does a single gamete have?
23 chromosomes (In pairs)
32
Therefore,if a male and female gamete will fuse together,how many chromosomes will there be in all?
46 chromosomes
23 from the mother
23 from the father
33
Name the main parts of the male reproductive system
The penis
Accessory glands
Testes (singular: testis)
The genital ducts
34
What are the testes enclosed in ?
Scrotum
35
Where is sperm produced?
Testes
36
What are the necessary conditions needed for sperm production?
Sperm production requires a lower temperature than that outside of the body. (Body temperature is higher). This is achieved by the suspension of the testes outside of the body in the scrotum
37
What are seminiferous tubules?
These are located within the testes.
Males usually have 2 or 3 of these coiled structures, where actual sperm production takes place
38
What type of epithelium are seminiferous tubules made of?
Sertoli and Germ cells
39
Name the function of Sertoli cells
Supportive and nourishment function
40
Name the function of Germ cells
Undergo differentiation to become mature spermatozoa
41
Where are Leydig cells located?
Between the seminiferous tubules
42
Function of Leydig cells.
To synthesize testosterone
43
What hormone triggers the production of testosterone?
LH
44
Name 3 functions of testosterone in males
1) stimulates sexual and aggressive behaviour
2) promotes secondary sexual characteristics
3) Controls the growth, formation and function of the male reproductive tract
45
Name 2 functions of FSH in males
1) It influences the testes by stimulating immature germ cells to become into mature spermatozoa cells causing sperm production to increase.
2) diffuses into sertoli cells, improving testosterone uptake by these cells, in ways that improve sperm production
46
What is the function of the epididymis
1) 1mm in diameter and 6m long
2) This is the site of accumulation and storage of mature spermatozoa. When they leave the epididymis they become motile
3) Highly coiled and very compact tube
47
What is the function of the Vas Deferens? (sperm duct)
1) Mucous is secreted in the Vas Deferens by the seminal glands which aids in sperm motility
2) The Vas Deferens branch from the epididymis and then it continues towards the base of the urinary bladder, it pierces the prostate gland ,then branches into the urethra
3) Contains smooth muscle in its wall which helps to aid in peristalsis allowing more motility for the sperm. It passes over the ureter and then behind the urinary bladder
48
Name a function of the urethra
The urethra is a single tube which extends from the urinary bladder to the tip of the penis.
It conducts urine from the bladder during urination and provides path for sperms during copulation
49
Name all of the accessory glands
Seminal vesicles
Prostate gland
Cowper's glands
Urethral glands
50
Name a function of the seminal vesicles
Secrete a fluid containing fructose which is used by sperm for energy
This fluid is alkaline which neutralizes the acidity of the urine remaining in the urethra
51
Name a function of the prostrate gland
Lies below the bladder
Maintains the proper ph for the sperm being alkaline
Provides several enzymes which aid the motility of spermatozoa helping it to reach the egg
52
Mention some functions of the Cowper's glands
Small glands located underneath the prostate gland
Their contents are emptied into the urethra
1) provide lubricants during copulation
2) provide nutrients that sperm require for motility
3) neutralize the acidity of urine remaining in the urethra
53
Name some functions of the urethral glands
Located as bulges in the walls of the urethra
Provides mucous which serves a s a lubricant to semen
54
What happens to the penis during sexual excitement?
Erection
This is when blood will rush to the erectile tissue which causes an erection
55
What is the penis made up of?
Consists of 3 cylindrical bodies made up of spongy tissue
Shaft
Foreskin
Glans
56
What are the glans?
Penis tip and sexual stimulation
57
What is the shaft?
The tubular portion
58
What is the foreskin
Loose skin fold over the glans
59
What happens if there is a continued stimulation during copulation?
It causes an intense glandular and muscular contractions to occur in the male reproductive tract.
60
Explain the 4 stages of sexual stimulation in the male reproductive tract
1) The muscles in the walls of the epididymis ,Vas deferens and seminal vesicles will contract in a series of peristaltic contractions
2) The urethral sphincter closes, preventing the backflow of sperm into the bladder and passage of urine into the urethra
3) Semen is forced into the urethra driven by contractions of the muscles surrounding the tubules (emission)
4) Further forceful contractions of the urethral muscles will force the semen through the length of the urethra in spurts.
Whilst all of this is happening the prostate gland and the seminal vesicles add fluid which aids in motility
61
What is the sperm + fluid called?
Semen
62
What is the ejection of the sperm through the penis called?
Ejaculation
63
Label a the male reproductive tract
64
What does semen contain?
Semen contains a mixture of sperm,water,dissolved nutrients,enzymes and proteins
65
Name the main parts of a sperm cell
Head
Middle part
Tail
66
Name the function of the tail
A typical eukaryotic flagellum which aids in movement
67
Name the function of the middle part
Contains a lot of mitochondria that produce energy to help the sperm move
68
Name the function of the head
Contains a haploid nucleus.
Acrosomes are present in the head which contain enzymes which help to puncture the protective layers of the ova during fertilisation
69
What are acrosomes?
An organelle covering the head of animal cells, which contain enzymes which digest the protective layers of the ovum allowing fertilisation to occur
70
Mention the main parts from where the sperm passes
1) Seminiferous tubules
2)epididymis
3)Vas Deferens
4)Urethra
71
Mention 5 main differences between ova cells and sperm cells
1) Ova cells are larger than sperm cells. (sperm cells are very small,ova cells are much larger)
2) Ova cells are immobile whilst sperm cells are mobile
3) Ova cells are usually round in shape and are protected by a thin membrane and a jelly coat,whilst the sperm consists of a head,middle part and a tail
4) Ova cells usually mature singly and monthly,whilst sperm cells millions of them are produced at one time (during ejaculation)
5) Within the cytoplasm of ova cells,yolky droplets provide food store which helps to nourish the embryo until the placenta forms,whilst the sperm cell does not have any food sources,they just reloy on the middle part to produce energy,allowing it to move
72
What are the main parts of a female ovum cell
Cell membrane
cytoplasm containg yolky droplets
jelly coat (zona pellucida)
haploid nucleus
73
When do males start to produce sperm?
Males are born with immature germ cells,however they start to become mature spermatozoa during puberty. Then a man keeps on producing them throughout his life.
74
When do females start to produce ova?
Females start to develop ova before they are born. At birth a girl has all of the ova that she will have in her lifetimes,however they are in an immature stage. They start to become mature during puberty. Then after puberty once a month,one of these ova will develop into a mature ovum
75
Name the 6 main parts of the female reproductive system
1) Ovaries: where ova are produced
2) Oviducts : 2 tubular tubes where the egg passes to after they are released from the ovaries
3) Uterus : sac where the embryo develops
4) Vagina: leads from the uterus to the exterior
5) Vulva :external genitalia
6) Mammary glands: provide milk for the offspring
76
Describe the structure of the ovary
Almond shaped ,located on each side of both the sides of the lower abdominal cavity
77
What do we call an immature female egg cell?
Oocyte
The oocyte matures completley into an ovum DURING THE MENSTRUAL CYCLE
78
What 3 things does an ovary have?
Primary Oocytes: potential egg cells
Graafian follicles (mature)
Atretic follicles (cease to develop and degenerate)
79
Define an ovarian follicle
An ovarian follicle is a fluid-filled sac that contains an immature egg cell or oocyte. During ovulation a mature egg is released from the follicle
80
What hormone do ovaries produce?
Oestrogen
81
What is the function of oestrogen?
Steroid hormones which are responsible in developing body form and other features characteristic of a female
82
What is the oviduct/fallopian tube?
Long narrow ducts which are locttaed in the female abdominal cavity.
83
What happens in the fallopian tube?
The egg will be released from the ovary and will pass on to the oviduct. If the egg is fertilised it will become a zygote or if it not fertilised it will degenerate (period)
The oviducts transport the egg from the ovary,to the fallopian tubes to the uterus.
84
Where does the actual fertilisation take place in the female reproductive tract
Oviduct
85
What 3 things does a fallopian tube have?
Fimbriae
Ciliated cells
Secretory cells
86
Define fimbriae
Finger like projections which are located very close to the ovary. (do not touch the actual ovary),however when triggered by hormones to catch a released egg and move it down into the fallopian tube.
87
What is the internal lining of the fallopian tube lined with?
Ciliated and secretory cells
88
Function of ciliated cells in the oviduct
Movements of cilia currents which help to move the egg away from the ovary
89
Function of secretory cells in the oviduct
Provide nutrients for the egg cell as it passes from the oviduct
90
What type of muscle is located in the oviduct to help the egg move towards the uterus?
Smooth muscle which carries out peristaltic contractions
91
What is the uterus?
A hollow pear shaped sac
92
What 3 epithelial layers is the uterus made up of?
Endometrium
Myometrium
Perimetrium
93
What does the endometrium consist of?
epithelial cells,glands and blood vessels
94
What does the myometrium consist of?
blood vessels,connective tissue and smooth muscles
95
What does the perimetrium consist of?
Continuous with the ligaments which support the uterus and uterine tubes
96
What is the cervix?
Separates the uterus from the vagina
The cervix secretes mucous that fills the cervical canal
97
What is the vagina?
It runs from the uterus to the outside of the body
Sperm are deposited here and then they run to the cervix, to fertilize the egg
98
What is the vulva?
Present at the body surface
Consists of the labia majora and the labia minora
Consists also of the clitoris which is an organ for sexual stimulation
99
What are the mammary glands?
They produce milk for offspring for the infant
100
What does the milk consist of?
Rich in nutrients and antibodies to fight off diseases
Consists of water,lactose,fat protein calcium and phosphorus
101
Which hormone stimulates the production of milk?
Prolactin
102
Which hormone stimulates the secretion of milk?
Oxytocin
103
How is sexual life divided?
Before Puberty and After Puberty
104
Describe before puberty?
When the organism is not yet sexually active (the gonads are not productive yet)
105
Define gonads
The main reproductive organs. In males the main reproductive organs are the testes which make sperms,whilst in females the main reproductive organs are the ovaries which make egg. The gonads also make hormones
106
Describe after puberty
When the organism is ready to produce offspring
107
What is a function of hormones regarding reproduction?
They help to grow the secondary sexual characteristics in humans
108
What is the pituitary gland?
Attached to the base of the brain and is like the "master" gland in the endocrine system which produces many hormones. It is also responsible for growth hormone which affects growth
109
Which hormone is responsible to start puberty in females? (to cause an immature oocyte to become a mature ovum)
FSH
Its released in the blood then it reaches the ovary to stimulate the growth of immature egg cells into mature ones.
110
Where is oestrogen produced in females and mention its role
Ovary
Controls secondary sexual characteristics
(responsible for the growth of the body form and other characteristics which make a woman)
111
Which hormone "starts" puberty in males?
testosterone which is stimulated by the LH
112
Mention some differences of sexual secondary characteristics between boys and girls
Boys:
1) Testes enlarge
Penis enlarges
Pubic hair grows
Voice deepens
Facial hair grows
Height and growth spurt
Girls:
Breasts enlarge
Vagina and uterus enlarge
Pubic hair grows
Menstruation starts
Height and growth spurt
Hips widen
113
How long is the menstrual cycle?
28 days
114
When is the mature egg cell going to get released? Which phase of the menstrual cycle?
Ovulation (day 14)
115
How many stages are there in the menstrual cycle?
4
116
What happens to the lining of the uterus during the menstrual cycle just before ovulation?
The uterus lining will start to thicken
117
Name the 4 stages of the menstrual cycle
menstruation:loss of lining from the uterus if no fertilisation ocurred
Uterus lining starts to thicken
Ovulation: the egg is released from the ovary (egg will travel across the fallopian tube from the ovary)
The lining is maintained ready to fertilize an egg
118
How many hormones control the menstrual cycle?
4
119
Name the hormones which are involved in the menstrual cycle
LH
FSH
Oestrogen
Progesterone
120
Which hormones are secreted by the pituitary gland in the brain?
LH and FSH
121
Function of FSH in the menstrual cycle
Causes maturation of the egg in the ovary
122
Function of LH in the menstrual cycle
Causes the egg to be released from the ovary
123
What do oestrogen and progesterone mainly focus on regarding the menstrual cycle
Focus on thickening the lining of the uterus
124
Where is progesterone made?
Ovaries
125
What is the corpus luteum?
The follicle from where the mature egg was released from. Now it has become a structure called the corpus luteum which produces progesterone which helps to maintain the lining of the uterus for a potential pregnancy.
(empty egg follicle)
126
How does the immature egg cell exactly grow into a mature egg cell?
With the help of a follicle in the ovary which is triggered by FSH secreted in the pituitary gland
127
True or false
FSH stimulates the production of oestrogen
True
The follicle will produce oestrogen
The follicle starts to grow by the FSH
128
True or false
After oestrogen is produced it inhibits the production of FSH
True
129
What happens when oestrogen has risen to a high enough level?
LH is secreted from the pituitary gland to during ovulation
130
What happens after?
The follicle will release the egg with the help of LH
Then this follicle will become a structure called the corpus luteum which produces progesterone.
Maintaining the uterine lining for a potential pregnancy
131
What will happen to progesterone production if fertilization occurs and if fertilization does not occur?
If fertilization does not occur, progesterone levels will drop and the corpus luteum dill degenerate. This is when menstruation will happen. (loss of the uterine lining)
If fertilization does occur, then progesterone will continue to be produced, to keep on maintaining the uterus lining.
132
When is LH secreted by the pituitary gland?
LH is ONLY secreted when oestrogen levels have risen to a high enough amount. The job of LH is to stimulate the release of the mature ovum from the ovary.
LH also stimulates the production of progesterone.
133
When is exactly progesterone produced?
Progesterone will only get produced when ovulation starts. If fertilisation occurs progesterone will continue to be produced. If fertilisation does not occur progesterone levels drop. (Therefore it will result in menstruation: loss of the uterine wall)
134
Name the types of follicles in the ovaries.
Primary and secondary follicles
135
What will the secondary follicle mature as?
Graafian follicle
136
Name the 4 phases of the menstrual cycle
The menstrual phase (phase 1)
The Pre-ovulation phase (phase 2)
Phase 3
The post ovulation phase
137
Describe the menstrual phase
Menstruation is caused by a fall in progesterone and oestrogen. Because they are hormones which promote the maintaintence of the uterus lining but since fertilisation didnt occur,these 2 hormones will drop.
The lining of the endometrium will shed as menstrual discharge
After the oestrogen and progesterone (their levels dropped) this will stiumlate the secretion of FSH and LH
138
Describe the Pre-ovulation phase
FSH is secreted from the pituitary which stimulates the growth of a Graafian follicle
Ovary starts to produce oestrogen, which will start before ovulation to allow to endometrium to start to thicken for a potential pregnancy.
This will cause the blood vessels and endometrial glands to grow into the endometrium
Endometrial glands provide all the substances necessary for a potential implantation and embryo development.
139
Describe phase 3
LH gets secreted from the pituitary gland and causes the graafian follicle to rupture causing ovulation
140
Describe the post-ovulatory phase (days 15-28)
Under the influence of LH the ruptured follicle becomes a corpus luteum.
Corpus luteum continues to produce progesterone and oestrogen to maintain the endometrium.
These 2 hormones will cause the growth and repair of the uterus lining for the potential pregnancy. Blood vessels will continue to grow and enlarge rather than cell growth.
The other extra follicles stop maturing and degenerate
141
What prevents the corpus luteum from degenerating if fertilisation occurs?
HCG
Produced by the implanted embryo
So the corpus luteum keeps on producing oestrogen and progesterone
142
True or false
If fertilisation occurs FSH and LH continue to be released
False
They are stopped. To prevent ovulation
143
True or false.
The corpus luteum eventually will degenrate and until the placenta forms. The placenta will produce progesterone and oestrogen
True
144
During pregnancy why is progesterone levels high and oestrogen levels low?
Because progesterone prevents uterine contractions and oestrogen to maintain the lining of the uterus
145
What will happen to the levels of progesterone and oestrogen towards the end of the pregnancy?
Progesterone falls and oestrogen rises.
This is done to make the uterine muscles more sensitive to stimulate childbirth.
146
What is the placenta?
An organ that develops in the uterus during pregnancy
147
What is the function of the placenta?
It provides oxygen and nutrients to the growing foetus and to remove waste products. The umbilical cord also arises from it.
148
What is the umbilical cord?
Connects the baby to the mother's placenta. Provides nutrients
149
What is parturition?
childbirth. The process of delivering the baby and the placenta from the uterus to the vagina in the outisde world,also called labour or delivery.
150
Define copulation
When sperm from a male are deposited into a female during mating. (sexual intercourse). When the male introduces sperm into the female reproductive tract.
151
How is the sperm helped to reach the ovum?
With the movement of its tail
Middle part contains mitochondria
Contractions of uterus and oviduct walls
Cervix secretes mucous
152
What will happen when the sperm will encounter the ovum?
The sperm will release digestive enzymes from its acrosome. These enzymes will digest and puncture the thick protective coat of the ovum,in order for the sperm to enter the egg.
(Called the zona pellucida)
153
What is the zona pellucida?
A thick transparent extracellular layer around the ovum which is composed of glycoproteins. Sperms bind to the zona pellucida,but not all of them can penetrate the membrane
154
Which parts of the sperm actually enter the ovum?
The sperm's nucleus and centrioles only enter the ovum's cytoplasm
155
What is a centrioles in sperm cells?
A pair of minute cylindrical organelles near the nucleus in animal cells which are needed for cell division when fertilisation occurs.
156
So what will happen in fertilisation?
23 chromosomes from the mother and 23 from the father will join up to form 46 chromosomes which are needed to form a zygote. (The diploid number of the chromosomes are restored)
157
What is another way how fertilisation can occur but without copulation?
In vitro -fertilisation
When the male gametes and the female gametes are fused together outside of the body system. They are dissolved in a fluid to be induced together.
158
What will happen after fertilisation?
Embryo develops
159
What are the cell divisions called which take place after fertilisation?
Cleavage: the zygote with the zona pellucida they start to undergo a series of cell divisions. The single zygote will start to be subdivided into smaller cells.
160
What are blastomeres and the morula?
The blastomeres are the ball of cells which will turn into another solid ball of cells called the morula
Then a fluid filled cavity forms an d then the blastocyst forms
161
Which cells from the blastocyst form the amniotic sac ,and which ells form the foetus?
Amniotic sac will be formed by the outer cells,whilst the foetus will be formed by the inner cells
162
Define blastomere
a cell which is produced by cell division of the zygote after fertilisation
163
Define morula
solid mass of blastomeres resulting from a number of cleavages of a zygote
164
Define implantation
When the blastocyst will adhere to the endometrium between 5 or 6 days after fertilisation
165
What is the amniotic sac?
The sac where the developing embryo and later foetus develops
166
What holds together the amniotic fluid?
Amnion
167
What is the amnion?
The lining that surrounds the embryo
168
Name some functions of the amniotic fluid?
It acts as a shock absorber
It bursts just before parturition
Prevents dehydration of the tissues by osmosis
168
Give some extra details regarding the placenta
The placenta will secrete progesterone and oestrogen after the corpus luteum degenerates.
Attaches the embryo to its mother
The placenta prevents the mixing of blood of the mother and the baby and protects the foetus against disease
169
What are the 3 blood vessels which are located in the umbilical cord?
2 umbilical arteries: whch carry deoxygenated blood and wastes from the foetus the to placenta
And 1 umbilical vein: which carries oxygenated blood and nutrients from the placenta to the foetus
170
What will the pituitary gland from the embryo release?
ACTH which will stimulate the production of corticosteroids just before childbirth
171
What is the purpose of the corticosteroids
To reduce progesterone level to stimulate the production of oxytocin
172
What is the importance of oxytocin?
To promote further contractions during childbirth.
173
Give an example of what will trigger more oxytocin?
The pressure of the head of the foetus in the cervix
174
What is the pressure of the foetus's head called?
A positive feedback because the nerve impulses will further stimulate the production of oxytocin
175
