Unit 4 Part 4 Flashcards
D3.1 - Reproduction
Sexual reproduction?
Requires a male and female
- Each parent contributes some genes to offspring
A sexual reproduction?
Requires only 1 parent
- Results in multiple identical organisms
Sexual reproduction features?
- Gametes fertilized
- Two parents
- Offspring genetically unique compared to parents
- New gene combination + promotes genetic variation
- Allows adaptations for changing environment
Asexual reproduction features?
- Organism makes a copy of itself
- Only one parent
- Offspring genetically identical to parent
- No new gene combination and little genetic variation
- Little change in adaptations
Asexual mechanisms?
- Binary fission
- Mitosis
- Budding
- Fragmentation
- Vegetative reproduction
- Parthenogenesis
Binary fission?
When bacteria replicate their DNA and divide into 2 cells
- Can occur more than once an hour for certain bacteria under certain conditions
Mitosis?
When unicellular eukaryotic organisms replicate their DNA and mamy organelles
- Leads to growth in budding, Fragmentation, vegetative reproduction, and Parthenogenesis
Budding?
When new genetically identically organisms grow directly from an existing organism
Fragmentation?
When the body of an existing organism breaks up into several fragments
- Each growing into a complete organism
Vegetative reproduction?
Common in many plants
- W/ new plants emerging from roots, bulbs, tubers, and shoots
Parthenogenesis?
Growth and development of an egg cell w/out the involvement of a male gamete
- In an animal species
Pros of asexual reproduction?
- Almost always faster
- Requires less expenditure of energy
- A single organism can colonize a new area easily
How does meiosis produce haploid cells?
Reduction division
- B/c the number of chromosomes in each gamete is reduced to one half if original number
What happens before meiosis
DNA replication takes place
- Producing a pair of chromatids from each chromosome
How is genetic variation provided?
Crossing over
- Leads to a recombination of alleles during metaphase 1
Independent assortment of chromosomes
- Random orientation and division of chromosomes during m1
Random fertilization
- As there are millions of sperm and egg possibilities
What does meiosis do for chromosomes?
Breaks up parental combination of alleles and provides new Chromosome combination
What are the sperm cells designed for?
To travel to the egg
- Very small in size
- Multiple mitochondria
- Flagellum for swimming
- Do not contribute anything towards food reserves of early embryo
What are egg cells designed for?
Provides initial source of nutrition for development of embryo followed by placenta and uterus
- Mitochondria
- Very big in volume
Semen?
The fluid that contains the sperm in an ejeculation
Anatomical structures of female reproductive system?
- Ovaries
- Fallopian tubes (oviducts)
- Uterus
- Endometrium
- Cervix
- Vagina
Function of ovaries?
Female gonads, produce + secrete oestradiol, produce and release eggs as secondary oocytes
- The area where ovulation occurs and grows into corpus luteum
Fallopian tubes/ oviducts function?
Ducts that carry eggs or early embryo to the uterus
Uterus function?
Muscular structure where early embryo plants and develops
Endometrium function?
Highly vascular inner lining of uterus
Cervix function?
Lower portion of uterus
- Has an opening to the vagina allowing childbirth and sperm ti enter
Vagina function?
Muscular tube that leads from external genitals to cervix
Ovulation?
Release of an egg
What is the purpose of a menstrual cycle?
To time ovulation for possible fertilization and later implantation into inner lining of uterus
When must implantation occur?
When the endometrium is highly vascular
The regulatory centre for the menstrual cycle?
The hypothalamus
What does the hypothalamus do?
Produces the hormone gonadotropin-releasing hormone GnRH
Target tissue of gonadotropin releasing hormone?
Pituitary gland
What hormones does the pituitary gland release into the blood stream after being targeted by gonadotropin releasing hormone?
Follicle stimulating hormone FSH and luteinizing hormone LH
- Target tissue of these two is the ovaries
Main function of Follicle stimulating hormone and luteinizing hormone
Increase production and secretion of oestradiol
- It’s Target tissue is endometrium and increases density of blood vessels in endometrium
What happens with a positive feedback loop due to oestradiol?
Oestradiol stimulates pituitary gland to release for follicle stimulating hormone and luteinizing hormone
What does the increase of Follicle stimulating hormone and luteinizing hormone result in?
The production of structures called Graafian follicles
What is the Graffian follicle?
Under chemical stimulation of FSH and LH the somewhat arranged follicle cells (cells w/in the ovaries) and oocytes (Reproductive cells in a stage of development w/in ovaries) take on a particular cellular arrangement called Graffian follicle
What leads to ovulation?
A spike in level of FSH and LH caused by positive feedback loop
Progesterone?
A hormone that maintains the thickened, highly vascular endometrium
How is progesterone produced?
When follicle cells’s outer ring remains in the ovary they begin to produce and secrete it
Corpus luteum?
A structure that is only hormonally active ( producing progesterone) for 10-12 days after ovulation of no fertilization
How is corpus luteum produced?
When cells of outer ring begin to divide in order to fill the wound area left by ovulation
Anatomical structure of male reproductive system?
- Testes
- Epididymis
- Secrotum
- Vas deferens
- Seminal vesicles
- Prostate gland
- Penis
- Urethra
Testes function?
Male gonads where sperm are produced in small tubes called seminiferous tubules
Epididymis function?
Area where sperm are received, become mature, and become capable of swimming motion
Scrotum function?
A sac that holds testes outside body cavity so sperm production and maturation can happen at a temp cool than body temp
Vas deferens function?
Muscular tube that carried mature sperm from Epididymis to urethra during an ejaculation
Seminal vesicles function?
Small glands that produce and add seminal fluid to semen
Prostate gland function?
Gland that produces much of semen, including carbohydrates for sperm
Penis function?
Organ that becomes erect as a result of blood engorgement to facilitate ejaculation
Urethra function?
The tube that semen leaves the penis after all glands have added fluids
The ovarian cycle?
Controls production and release of eggs and the cyclic release of oestradiol and progestrone
Uterine cycle?
Controls preparation and maintenance of endometrium to receive a fertilized egg
Reasons for infertility?
- Low sperm counts in males
- Failure to achieve/ maintain an erection in males (impotence)
- Inability to ovulate regularly in females
- Blocked Fallopian tubes in females
How does puberty commence?
Hypothalamus increases production of gonadotropin releasing hormone early teens
- Pituitary gland is targeted and in response gonadotropins’s secretion is enhanced
What do the gonadotropins do?
Stimulate steroid production by gonads
- Steroids like Testastrone, oestradiol, and progesterone
Puberty changes in females?
- Increase in height and body mass
- Growth of underarm and pubic hair
- Development of breasts
- Menstral cycle starts
- Acne may begin
- Bone structure of hips widen in preparation for child birth
Puberty changes in males?
- Increase in height and body mass
- Growth of underarm, pubic, facial, and chest hair
- Acne could begin
-Voice becomes deeper - Enlargement of testes and penis
- Erections begin
