What are the advantages of asexual reproduction?

No need to find mates

Can produce many offspring in a short time

Perpetuates successful genotypes- no change from generation to generation

Sexual reproduction uses (blank) to produce haploid gametes

How is this process advantageous?

Meiosis

Increases genetic variability

Fertilization activates the egg by triggering (blank) to start (blank)

Metabolic changes

Embryonic development

Reproduction cycles are often related to what? Why are they dependent on this factor? (3 reasons)

How else can cycles be controlled?

Changing seasons

Allows conservation of resources

Reproduction requires energy- waiting til ideal season means least energy used

Seasonal conditions are favorable to offspring

Environmental and hormonal cues

What are hormones? Where are they synthesized and secreted? How do they travel?

Substances that act as chemical signals

Synthesized and secreted by endocrine glands

Travels around body via circulatory system

How do hormones work to affect the regions they need to?

They inject into target cells: cells with specific receptors for the specific hormone

Name the 3 stages of how a hormone affects the body

1) Reception of the signal- hormone binds to a specific receptor protein in/on cell

2) Signal is transducted (transformed from one form to another)

3) A response occurs: cell behavior changes

How many receptors can a hormone bind to?

a variety in various target cells

(e.g adrenaline causes heart cells to contract, in liver causes glycogen breakdown)

What reproductive structures are common to both males and females?

Gonads: produce gametes and secrete hormones

Ducts: for gamete transport and storage

Structures for copulation

What structures are found in the female reproductive

Ovaries

Oviducts (Fallopian tubes)

Uterus

Vagina

External Organs (vulva)

Mammary glands

What are the functions of the ovaries?

Produce gametes (secondary oocytes) (eggs)

Produces hormones- Estrogen and progesterone

What are the functions of oviducts?

Allows eggs/zygotes to travel from the ovaries to the uterus

Fertilization usually occurs in the upper third of the oviduct

What is the main function of the uterus? How (briefly) does this occur?

The muscular organ where the fetus develops

the fertilized egg travels through the oviduct, and it eventually implants into the uterus where it will finish development until birth

What are mammary glands? How does their function occur?

What kinds of tissue make up these organs in non lactating female mammals?

Small sacs of epithelial tissue that secrete milk. The milk drains into a series of ducts opening at the nipple

In non lactating mammals, the tissue is adipose tissue

What is oogenesis? What does it produce?

The development of egg cells

Produces 1 mature egg and polar bodies (degenerates)

When does oogenesis begin?

Begins in the female fetus before birth

-females are born with all egg cells they will ever have

What milestone needs to be reached to release a primary oocyte and its follicle, and how often does this occur?

Puberty

Once a month one follicle matures, and it and its oocyte is ovulated (released)

What is the corpus luteum?

 The ruptured follicle that produces estrogen and progesterone to support development of the fertilized egg until placenta takes over in trimester two

If fertilization does not occur, what happens?

The corpus luteum degenerates

Progesterone drops

Menstruation occurs

New follicle is stimulated to develop

What organs are affected during the female reproductive cycle? What occurs?

The ovaries change- an oocyte matures

The uterus changes- prepares for the arrival of a fertilized egg

The cervix and breasts change shape/size

What are the female sex hormones? (3)

How do they affect a woman?

Estrogen, progestins, androgens

Affect growth and development, regulate reproductive cycles and sexual behaviour

progestins prepare and maintain uterus

What are the male internal reproductive organs? What are the accessory glands?

Internal: testes, seminiferous tubules, epidydymis, vas deferens, ejaculatory duct, urethra

Accessory: seminal vesicles, prostate gland, bulbourethral gland

What is the function of the scrotum?

Keeps testes cool enough to function (testes contain the epididymis where sperm are stored)

What is the function of seminiferous tubules?

Form sperm

What is the function of the epididymis? Where do sperm go during ejaculation?

Stores sperm, sperm are propelled into the vas deferens through muscular contraction

What do the accessory glands do?

a) Seminal vesicles

b) Prostate gland

c) Bulbourethral gland

a) Secrete fluid containing mucus, amino acids, fructose, and prostaglandins

Provides nutrients and energy for sperm

Make up 60% of volume

b) Empties into urethra, seceretes milky alkaline fluid to activate sperm and neutralize acidity of residual urine

c) Empties into urethra, secretes viscous fluid before ejaculation

What is spermatogenesis? What does it produce?

The production of sperm cells in adult males, it is continuous in the seminiferous tubules

Produces 4 mature sperm

What is the order of development in male sperm?

Spermatogonia

Primary Spermatocytes

Secondary Spermatocytes

Spermatids

Mature Sperm

diploid primary Spermatocytes form by (blank) then divide by (blank)

mitosis

meiosis

Sperm are composed of?

Head- contains DNA (HAPLOID number of chromosomes)

Acrosome- specialized coating that contains enzymes to help sperm penetrate egg

Midpiece- contains mitochondria generating ATP to move

Tail- flagellum that propels sperm

What is "the pill" composed of, and how does it work to prevent pregnancy?

What are the risks?

Progesterone and estrogen

It starts negative feedback on the anterior pituitary and hypothalamus to prevent hormone secretion

-No follicular development or ovulation

Increased risk of blood clot formation

What are other hormonal contraceptive methods (besides pill) (3) and how do they work?

a) Norplant: surgically implanted capsules release progestin and inhibit ovulation for 5 years

b) Depo-Provera: Intra-muscular injections of progesterone every 3 months that change uterine lining and ovum maturation

c) Vaginal ring: worn internally releasing progestin or progestin estrogen combo

How do IUD's work?

Change uterine lining so it is unfavorable for embryo implantation

What is a diaphragm, how does it work? What are the risks of usage?

Dome shaped cap that fits over cervix preventing entry to uterus

Does not protect against AIDS or STDs

May cause recurrent UTIs

Often used in combination with spermatocides

What is a vasectomy? How does it work?

A removal of a portion of the vas deferns

Sperm are still produced, but can no longer reach exterior

They degenerate and are removed by phagocytosis

Does not affect testosterone levels

Where does fertilization occur, and when?

Uterine tube about 12-14 hours post ovulation

In order to reach the egg nucleus, what 3 barriers must the sperm pass through?

Jelly coat

then the Vitelline layer

then the plasma membrane

What are the 3 key phases of embryonic development?

1) Clevage: forms a multicellular embryo

2) Gastrulation produces a 3 layered embryo

3) Organ formation occurs from each layer

Describe what happens during the clevage phase of embryonic development

A rapid series of cell divisions

Turns the unicellular zygote into a multi-cellular embryo

Overall size of the embryo remains the same- the cells get smaller

End result is a fluid filled embryo called a blastula which has different developmental regions

What happens during gastrulation?

More cells are added and migrate to 3 distinct layers:

Ectoderm forms the epidermis of skin, and nervous system

Endoderm forms the digestive tract, respiratory system, liver, pancreas, reproductive system..

Mesoderm forms skeletal system, muscular system, circulatory system, part of reproductive system, and lining of body cavity

The stiff (blank) forms the main axis of the bod and is later replaced by the (blank)

The (blank) develops above the (first blank) and will become the brain and spinal cord

notochord

Vertebral column

Neural tube

notochord

Somite belongs to which of the 3 blastula layers, and what will it develop into?

Mesoderm, segmental structures such as muscles

signalling between neighbouring cells in a developing embryo induces what?

Changes in cell shape

Cell migration

Programmed cell death (apoptosis)

What do vertebrate limbs begin as? Where do bone and muscle develop?

Embryonic structures called limb bud

Develop in precise locations relative to 3 axis

Homeotic genes do what?

Direct embryonic pattern formation

(the emergence of a body form with specialized organs and tissues in correct relative positions)

How do homeotic genes control embryonic pattern formation?

protein made from these genes (directed from homeoboxes: nucleotide sequences in the genes) bind to DNA and turn on/off genes during development

What is gestation?

The act of carrying young in the female reproductive tract from conception to birth (pregnancy)

When does implantation of the blastocyst into the endometrium occur?

7-10 days after fertilization

What does the trophoblast do? What is it?

Secretes enzymes that enable the blastocyst to digest and invade endometrium

It is the outer cell layer of the blastocyst, forms part of the placenta 

Inner cell mass becomes the embryo

Where does fertilization occur?

Oviducts

What are the four extra-embryonic membranes?

Amnion- surrounds the amnionic cavity in which the embryo floats

Chorion- contributes to the placenta

Yolk Sac- source of the first germ cells and blood cells

Allantois- contributes to the umbilical cord

Which of the four extra-embryonic membranes secretes hCG to prevent menstruation?

The Chorion- human chorionic gonadotrophin

What are chorionic villi? How do they help the embryo?

They are part of the placenta associated with the mother's endometrium

Bathed in pools of maternal blood

-Embryo receives nutrients

-Wastes will diffuse into the mother's blood vessels and are carried into her kidneys where they will be excreted

What happens (overall) during the first trimester?

0-13 weeks

Period of greatest change

Embryo forms, looking like other vertebrate embryos

Extraembryonic membranes form

All major organ systems are established

After 9 weeks embryo is called a fetus

-can move arms and legs

-starts to look distinctly human

What happens during second trimester?

14-26 weeks

Fetus greatly increases in size

Its human features are redefined

at 20 weeks:

about 19cm long

weighs about 1 pound

What happens during trimester 3?

Rapid growth and gain of strength

Circulatory and respiratory systems mature

Muscles thicken and skeleton hardens

Maintains its own body temp

Babies born as early as 24 weeks may only survive with extensive medical care

What induces birth? What kind of feedback mechanism controls labour?

Hormonal changes

Positive feedback loop

What hormones specifically affect the labour process, and how?

Estrogen is released from ovaries increasing the sensitivity of the the uterus to oxytocin

Oxytocin is a powerful stimulant for the smooth muscle of uterus, also stimulates placenta to make prostaglandins that stimulate uterus muscles to contract even more

Uterine contractions stimulate the release of more oxytocin and prostaglandins

What are the 3 stages of labour?

1) Dilation of cervix, longest stage (6-12 hours plus)

2) Expulsion

Period from full dilation to deilvery

Uterine contractions every 2-3 min

Infant is forced down out of uterus within 20 minutes

3) Delivery of placenta: 15 mins within birth of baby