Biological Principles Unit 3 Lec. 4

What are the two types of reproduction?

Asexual and Sexual

What is Asexual Reproduction?

It involves the formation of individuals whose genes come from one parent.

-no fusion of sperm and egg

What are the types of asexual reproduction?

-Fission

-Budding

-Fragmentation

What is Fission?

Asexual reproduction in which a parent separates into two or more approximately equal sized individuals.

What is Budding?

Asexual reproduction in which new individuals split off from existing ones

What is Fragmentation?

Asexual reproduction by fragments of body parts of another organism. When followed by regeneration will form a new individual.

What is Pathenogenesis?

Process by which an unfertilized egg develops into (often) haploid adult.

-Common in females since they do not need sperm from males.

If you are a haploid male wasp how do you produce haploid sperm?

Through Mitosis

What are the advantages of asexual reproduction?

-Can reproduce without mate

Can have numerous offspring in a short period of time.

-In stable environments, allows for the perpetuation of successful genotypes.

What is Sexual reproduction?

The formation of offspring by the fusion of haploid gametes.

What is an Ovum?

Female gamete - usually large and motile

What is a Spermatozoan?

Male gamete- usually small and motile

What is the advantage of sexual reproduction?

Sexual reproduction increases genetic variation among offspring.

What is hermaphroditism?

A type of sexual reproduction where on individual is functional as both male and female.

What are the characteristics of hermaphrodites?

-Some self fertilize

-Most mate with another member of the same species.

-Each individual receives and donates sperm.

-Results in twice as many offspring as would occur if only one set of eggs were fertilized.

What is sequential hermaphroditism?

An individual reverses its sex during its lifetime.

What is Protogynous?

Female first sequential hermaphroditism.

What is Protandrous?

Male first sequential hermaphroditism.

What is the default sex for humans?

Female (XX) because of absence of “SRY" gene.

“SRY” gene is present where and produces?

On Y chromosome and Testosterone

If embryo at 7 weeks has a Y chromosome and functioning “SRY” gene this means?

That a peak of testosterone will be produced leading to the formation of a penis. This is because the opening of the vagina closes and the clitoris forms to become the head of the penis instead, and the flaps of the vagina (labia) become the scrotum holding testicles.

In the absence of testosterone and “SRY” gene what happens?

What would have been the head of the penis becomes the clitoris. The opening of vagina remains and does not close. The flaps of skin become inner and outer labia. Lastly, with a small whole where women urinate below clitoris.

What happens when inner genitalia have the presence of testosterone and “SRY” gene at 7 weeks?

Males will only need gonads so other tubules will disappear. Gonads will form testicles by descending down to scrotum.

Why is it dangerous if testicles do not descend down?

Testicles sperm can be killed because in the stomach it is too warm for them.

For inner genitalia if no testosterone and “SRY” gene is present what occurs?

The embryo is female which it will need both sets of tubules and gonads. The gonads become ovaries connected by membrane to fallopian tubules and second set of tubules will be oviducts which brings ovum to uterus. And the opening of uterus will be the vagina.

What is Spermatogenesis?

The production of mature sperm cells from spermatogonium in testis.

Spermatogenesis is?

A continuous and prolific process in the adult male.

How much sperm does each ejaculation contain?

100- 650 million sperm

Where does spermatogenesis occur?

Seminiferous tubules

As spermatogenesis progresses the developing sperm cells do what?

Move from the wall to the lumen of a seminiferous tubule.

A large number of mitochondria do what for the sperm cells?

Provide ATP to power the flagellum of sperm.

How does spermatogenesis meiosis work?

Interphase (Diploid/ Spermatogonium) → Meiosis 1 (Primary Spermatocyte/Diploid) → Meiosis 2 (Secondary Spermatocytes/Haploid→ Spermatids/Haploids)→ Sperm goes through specialization to form sperm with flagellum.

What does the structure of male reproductive organ contain?

• Urinary bladder

• Seminal vesicle

• Ejaculatory duct

• Prostate gland

• Bulbourethral gland

• Vas deferens

• Erectile tissue

• Urethra

• Epididymis

• Testes

• Penis

What is the Scrotum?

Skin that holds testis outside of the body for optimum temperautre. Contains muscle. Sperm production in testes up to 40 days.

What is Epididymis?

Tubules that leave testes into and around urinary bladder to the side joining with other glands such a prostate gland and it will unite with urethra. The epididymis receives immature sperm from the testes and stores them while they mature and become motile. 

What do the testis have inside and what do they do?

Seminiferous tubules meiosis will occur to from sperm which will be stored in epididymus.

What is the Vas Deferens?

This is where the sperm passes to go the liquid in the seminal vesicle.

What is the seminal vesicle?

Contains thick mucus (prostaglandins) which promote contraction of smooth muscles of uterus and contain glucose.

What is the prostate gland?

Thin milky white fluid mobility and viability of sperm.

What is the bulbourethral gland?

Releases fluid that neutralizes the pH of urethra for sperm to pass through.

What is the urethra?

The only other opening other than the anus that is through penis and tip that can release urine or sperm.

The penis is made up of?

Erectile tissue which is a spongy tissue where blood is shoved into penis that maintains erection.

What is the disadvantage of having gonads outside body?

Tubules can be crushed leading to infertilization.

How does a vasectomy or cutting of the vas deferens prevent pregnancy?

The sperm will stay stuck in testes and epididymis.

If there is low testosterone produced in the 7 weeks of embryo forming genitalia what could occur?

Female genitalia can form on the outside while the male inner genitalia stays inside.

At birth there is a peak of testosterone for males that changes?

The brain for males or behaviors.

What is the structure of the sperm?

• Haploid Nucleus

• Tipped with acrosome

  -Contains enzymes that help the sperm penetrate the egg.

• Spiral Mitochondrium

• Tail: Flagellum & Sheath (Plasma membrane that protects tail)

How does the hormonal control of spermatogenesis work?

• Individual hits puberty

• Hypothalamus releases gonadotropin releasing hormone (attraction of gonads)

• GnRH goes through blood to pituitary triggering production of 2 hormones.

• The hormones are follicle stimulating hormone (FSH) and luthanizing hormone (LH)

• The follicle stimulating hormone that is going to encourage the production of the meiosis or spermatogenesis falls in the blood. LH also goes in blood.

• They hit the testes and they go to different cells. The Lh goes to the Lydic cells to produce testosterone.

• FSH go to spermatogonia giving signal to start meiosis.

What does follicle stimulating hormone (FSH) do?

Stimulate spermatogenesis

What does luthanizing hormone (LH) do?

Tells specific cells of the testes to produce testosterone.

What are the primary sex characteristics of males before puberty?

Presence of testicles

What are the secondary sex characteristics of males after puberty?

• Hair growth

• Voice changes

• Adams apple

• Muscle mass

Summary of male sexual reproduction?

• GnRH is produced in hypothalamus goes to anterior pituitary and enforces pituitary to produce and release FSH and LH in the blood.

• LH is produced in the anterior pituitary targeting the male gonads. Wanting to produce testosterone. If too much testosterone is produced can cause gnrh, fsh and lh to stop producing.

• Follicle stimulating hormone foes to gonads promoting meiosis or spermatogenesis.