Reproduction 2nd year Topic 6 Flashcards
Mention the 2 types of reproduction
Asexual and sexual
What is the difference between asexual and sexual reproduction?
asexual: one organism
sexual: 2 organisms male and female
Mention some organisms which carry out these 2 forms of reproduction
Sexual: fish and mammals (higher invertebrates and all vertebrates)
asexual: bacteria and some plants (lower organisms)
What happens if there is a lack of sexual reproduction?
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
How does cell division occur in organisms who carry out asexual and sexual reproduction?
Asexual: mitosis/budding/vegetative reproduction
Sexual: meiosis – fertilization occurs
(how cell division occurs)
Name some advantages of asexual and sexual reproduction
asexual: quick
less energy
sexual: genetic variation
unique and organism is protected
Name some disadvantages of asexual and sexual reproduction
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
When we speak about asexual and sexual reproduction in terms of evolution,which is the “better” one?
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
How long does asexual and sexual reproduction take to complete?
Asexual: very short period of time
sexual : takes months to complete
Which type of reproduction is involved in the formation or the fusion of gametes?
Sexual
Asexual does not occur
Where does the unit of reproduction take place in both forms of reproduction?
asexual: whole parent body or or fragment
sexual: gametes
How many offspring are produced in each types of reproduction?
asexual: 2 or more
sexual: one or more
Mention 4 types of asexual reproduction
Budding
Vegetative propagation
Fragmentation
Fission
Define fragmentation
Includes the parent colony being spontaneously broken down into fragments to produce new colonies ex: Spriogyra
Define fission
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
Define vegetative propagation
asexual reproduction in plants involving the parent plant’s fragments or a special reproductive structure
Define budding
The formation of a small clone on the mother organism. It could remain attached or get dislodged to produce another colony
Why is genetic variation so present in sexual reproduction?
Because it involves 2 partners and due to the crossing ,and independent assortment of genes during meiosis
True or false.
Sexual reproduction ensures genetic diversity which is fundamental in terms of evolution
True
Because it helps the adaption of environments
How can sexual reproduction be divided?
Internal or External
What is the difference between internal and external reproduction?
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
What are some disadvantages of external fertilization?
Loss of energy and offspring due to predation or loss with currents
What is another word for sex cells?
Gametes
Where are gametes produced?
sex organs
Mention the male and the female gametes.
Male: sperm
Female: ova
Where are the male and the female gametes made?
Male: testes
Female:ovaries
What happens during fertilization?
The sperm will join up with the ovum to produce a zygote
What is a zygote?
The very first fertilized cell
What will the zygote mature as?
Embryo
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
How many chromosomes does a single gamete have?
23 chromosomes (In pairs)
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
Name the main parts of the male reproductive system
The penis
Accessory glands
Testes (singular: testis)
The genital ducts
What are the testes enclosed in ?
Scrotum
Where is sperm produced?
Testes
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
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
What type of epithelium are seminiferous tubules made of?
Sertoli and Germ cells
Name the function of Sertoli cells
Supportive and nourishment function
Name the function of Germ cells
Undergo differentiation to become mature spermatozoa
Where are Leydig cells located?
Between the seminiferous tubules
Function of Leydig cells.
To synthesize testosterone
What hormone triggers the production of testosterone?
LH
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
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
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
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
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
Name all of the accessory glands
Seminal vesicles
Prostate gland
Cowper’s glands
Urethral glands
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
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
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
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
What happens to the penis during sexual excitement?
Erection
This is when blood will rush to the erectile tissue which causes an erection
What is the penis made up of?
Consists of 3 cylindrical bodies made up of spongy tissue
Shaft
Foreskin
Glans
What are the glans?
Penis tip and sexual stimulation
What is the shaft?
The tubular portion
What is the foreskin
Loose skin fold over the glans
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.
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
What is the sperm + fluid called?
Semen
What is the ejection of the sperm through the penis called?
Ejaculation
Label a the male reproductive tract
What does semen contain?
Semen contains a mixture of sperm,water,dissolved nutrients,enzymes and proteins
Name the main parts of a sperm cell
Head
Middle part
Tail
Name the function of the tail
A typical eukaryotic flagellum which aids in movement
Name the function of the middle part
Contains a lot of mitochondria that produce energy to help the sperm move
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
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
Mention the main parts from where the sperm passes
1) Seminiferous tubules
2)epididymis
3)Vas Deferens
4)Urethra