Sexual Reproduction

-involves 2 parents -Involves the process of

meiosis

Background Vocabulary:

- gametes – sex cells – sperm and egg

- gonads – sex organs/glands – testes and ovaries

- zygote – fertilized egg

egg + sperm = zygote

- meiosis – process by which sex cells develop

- gametogenesis, oogenesis, &spermatogenesis

- diploid (2n) – normal # of chromosomes (46 – human)

- haploid or monoploid (n) – ½ the # of chromosomes (23 – human)

Meiosis – results: 4 daughter cells with ½ the number of chromosomes

Meiosis – result 4 daughter cells ½ the # of chromosomes

Gamete Formation (Gametogenesis)Spermatogenesis

- testes produce sperm

- primary sex cell meiosis 4 monoploid cells

- each usually matures into a motile sperm cell

Result 4 motile sperm – 4/4

Oogenesis

- ovaries produce eggs (ovum/ova)

- ovum: larger, non-motile

- only 1 monoploid ovum usually forms

- other 3 – polar bodies – die

- unequal cytoplasmic division

Result: 1 egg and 3 polar bodies

Spermatogenesis Oogenesis

Zygote Formation

- zygote fertilized egg

- sperm + egg = zygote (fertilized egg)

- process is called fertilization

- recombination occurs (genes from mom and dad come together)

- chromosomes from both parents recombine – increases variety

Fertilization Zygote Cleavage

Internal Fertilization

- fertilization occurs inside the female

- usually terrestrial (land) organisms

- few eggs produced - protected

- could have either internal (mammals) or external (birds) development

External Fertilization

- fertilization occurs outside the body of the female

- usually aquatic (water) organisms

- many eggs – ensure survival

- only external development

Embryo Formation

- the zygote divides by mitosis (cleavage) to form an embryo

- zygote embryo – divisions by mitosis (cleavage)

- Gastrulationembryo forms layers- Differentiation occurs cells become

different - take on their own identity (hair cell, skin cell, etc.)

                                           

Embryo Formation –

zygote morula(solid ball) blastula (hollow ball) gastrula (3 germ layers – endoderm mesoderm, ectoderm)

Sperm + egg = zygote

Fertilization Cleavage

mitosis

Differentiation – Cells become different or specialized

• Ectoderm (Outer Layer): Skin & Nerves• Mesoderm (Middle Layer): Muscles & Blood

Vessels• Endoderm (Inner Layer): Digestive Tract

Sequence of events in sexual reproduction:

1. Meiosis2. Fertilization3. Mitosis (Cleavage)4. Gastrulation5. Differentiation

Male Reproductive System

Male Reproductive System

2 major functions:

1. Make sperm

2. Deposit in female (internal fertilization)

Structures and Functions:

1. Testes: Male gonads

a. Sperm and testosterone production

b. Location scrotum – keeps sperm 1 – 2 degrees cooler than normal body temperature

2. Vas Deferens:

a. tube that connects testes to urethra

b. sperm transported here

c. along the way secretions from 3 glands are picked up to make semen.

3. Semen: sperm + fluids

4. Testosterone: hormone secreted by testes, regulates development of secondary

sex characteristics.

Male Reproductive System – Frontal View

Male Reproductive System

Female Reproductive System

Female Reproductive System

Structures and Functions

1. Ovaries:

a. female gonads

b. produce eggs (meiosis – oogenesis)

c. eggs enclosed in follicles

d. once a month egg is ovulated (released – into fallopian tube)

2. Fallopian Tubes (oviducts):

a. connects ovary to uterus

b. fertilization here

3. Uterus:

a. implantation here (embryo embeds itself into uterine wall

b. development from embryo to fetus here

4. Vagina:

a. birth canal (menstruate through here too)

5. Estrogen and progesterone:

a. female hormones (ovaries)

b. regulate secondary sex characteristics

c. menstrual cycle

Menstrual Cycle

Background information:

-series of changes in ovaries and uterus

-Begins at puberty

-Temporarily stops during pregnancy

-Menopause – cycle stops permanently

Stages of the Menstrual Cycle

Stages of the Menstrual Cycle

(Lasts about 28 days)

A. Stage 1: Follicle Stage (10 days)

a. Pituitary FSH

b. Ovaries estrogen – thickens uterus

c. Egg matures in follicle – swells

B. Stage 2: Ovulation (1 day – stays in tube 2 – 3 days)

a. Pituitary LH

b. egg released from follicle

C. Stage 3: Corpus Luteum Stage (~ 14 days)

a. Follicle dies – forms a “scar” corpus luteum

b. Corpus luteum progesterone

c. Causes uterine lining to stay thick

D. Stage 4: Menstruation (4 days)

a. egg not fertilized – uterine lining breaks down

Internal Development: Placental Mammals

- development inside the female

- gestation- time period between fertilization and birth

1. Placenta:

a. Forms in uterus

b. Feeds fetus - nutrition

c. Exchanges gases for fetus – respiration

d. Rids fetus of wastes – excretion

e. No direct connection of bloodstreams between mother and fetus (Diffusion occurs across the blood vessels)

Placenta

2. Umbilical Cord:

a. attaches placenta to fetus

b. food, wastes, gases, travel through here

3. Amniotic Sac:

a. filled with amniotic fluid

b. protects fetus

Multiple embryo’s:

Identical twins: 1 sperm 1 egg splits same placenta/sacFraternal twins: 2 eggs 2 sperm separate sacs and placenta

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7 weeks - Brain has the first detectable brain waves, muscles develop and get stronger

                                         

8 weeks - Eyes are well-developed, Fingers lengthen while distinct grooves (digital rays) form between the fingers

                                            

12 weeks - Fetus begins to move around, though the mother cannot yet sense these movements.

                                            

14 weeks - Fetus is more flexible with ability to move head, mouth, lips, arms, wrists, hands, legs, feet, and toes.

                          

18 weeks - Fetus has phases of sleep and waking and may prefer a favorite sleep position, temporary hair called lanugo appears on the head

                           

20 weeks -  Fetus may suck on thumb. Extremely rapid brain growth; eyebrows and scalp hair become more visible and fetus blinks more often.

                                       

24 weeks - Fetal brain waves begin to activate auditory and visual systems, both mouth and lips show more sensitivity.  Eyes respond to light, while ears respond to sounds originating outside uterus.

                                       

32 weeks - Eyes open during alert times and close during sleep. Eye color is usually blue, regardless of the permanent color as pigmentation is not fully developed. Fingernails reach over finger tips and fetus can scratch itself.

                                             

40 weeks

Vaginal Delivery

Cesarean Delivery (C-section)

Artificial Insemination: sperm artificially inserted into female.

In Vitro Fertilization: fertilization occurs in a petri dish, then implanted in the uterus.

Amnioscentesis: removal of amniotic fluid from the sac during gestation chromosomes analyzed for genetic disorders