Animal Reproduction AndDevelopment

AP Biology

Asexual Reproduction

• Identical cells (clones)• Advantages:

– Reproduce without a mate– Lots of babies and fast too!– No energy used for maintaining a Repro system or hormones.– Great in a stable and favorable environment.

• Types:– Fission: Amoeba/ Bacteria separated an organism into 2

cells– Budding: Hydra, Sea Anemone, Grow a buddy off your side– Fragmentation: &regeneration: Sponges, starfish, planaria– Parthenogenesis: development of an egg without

fertilization: honeybees, lizards, et.

The Human Male Reproductive System

• Testis (sl)/ Testes (pl)- olive size (1-1.5in)– Divided into lobules. Male Gonads

• Lobules contain 1-4 seminiferous tubules– Between seminiferous tubules are

interstitial cells (Leydig cells)• Interstitial cells produce androgens =

testosterone– Sperm leave S.F.T. to go into

epididymus.(mobilizes sperm)

The Human Male Reproductive System

• Vas Deferens– Runs up epididymus into pelvic cavity– Arches over bladder– Empties into ejaculatory duct.

• Ejaculatory duct- (ejac to shoot forth)– Passes through prostate gland – Merges with urethra– Moves sperm through peristaltic waves.

Pregnancy & ReproductiveVasectomy

The Human Male Reproductive System

• Urethra– Sperm are ejaculated through it– Urine and sperm can’t travel at the same time

• Bladder sphincter constricts when sperm ejaculates.

• Seminal Vesicle– 60% of semen– Thick and Yellow

• Fructose Sugar nourishes• Vitamin C activates sperm• Prostaglandin (stimulates uterine contraction)

– Excretes into the ejaculatory duct

Cool Factoid: Sperm take 5 minutes to get to the ovary when ejaculated.

The Female Reproductive System

• Ovary. – Floats freely. Contains and matures eggs. – Part of the Endocrine system. Secretes

Estrogen.• Falopian tube.

– No contact between Ovary and Fallopian tubes.When ovary expels the Oocyte the fimbriae or ends of the fallopian tube capture it. Eggs can get lost here in the peritoneal cavity

Carried by peristalsis by cilia that line the fallopian tube. (3-4 Days)

Ovulation

The Female Reproductive System

• Uterus• Receives, retains and nourishes egg.• Pear shaped before pregnancy• 3 layers

– Endometrium – Egg implants here. Sloughs off monthly

– Myometrium- middle layer- smooth muscle= contractions

– Epimetrium- outer layer

• Vagina: birth canal.– Labor and delivery. – Cervix: mouth of the uterus.

The Female Menstrual Cycle

• Day 1-5 Mensus. Lasts 3-5 days. Blood loss is ¼ to ½ cup. *Iron pills important.

• Endometrium, glands, and blood supply increase. Estrogen (produced by follicles on the ovary) and LH peak day 12 + 13 =

• Ovulation Day 14. Follicle is like a boil on the ovary. LH causes it to rupture and the egg is released= ovulation. Used follicle becomes the Corpus Luteum= secretes progesterone.

MenstrualCycle

Explained

The Female Menstrual Cycle

• The four phases– Follicular phase: Follicles grow in overies

and secrete estrogen in response of FSH from anterior pituitary (menopause moment)

– Ovulation: Secondary oocyte (2n) ruptures in response to Luteinizing hormone.

– Luteal Phase: Corpus luteum forms and secretes estrogen and progesterone: thickens endometrium and uterus.

– Menstration: monthly shedding

Feedback and the woman…

• Positive Feedback: Estrogen released in the follicle state releases LH from the anterior pituitary. When ovulation has occurred the process is completed and stops.

• Negative Feedback: In the Luteal phase the corpus luteum secretes estrogen and progesterone, causes the hypothalamus and pituitary to shut off inhibiting LH and FSH.

Making the Gametes…

• Advantages of sexual reproduction: variation– Crossover– The Law of Segregation– The Law of Assortment

Spermatogenesis

• The making of sperm- begins at puberty.– LH causes the interstitial cells to produce

testosterone.– The seminiferous tubules are matured with

testosterone & FSH.

• Spermatogonium (2n) divides by mitosis to produce primary spermatocytes (2n)

• Meiosis 1 occurs producing secondary spermatocyte. Meiosis 2 = 4 spermatids (n)

Spermatogenesis animation

OOgenesis

• Eggs= ova. Begins in the female embryo.

• Oogonium cell (2n) makes primary oocytes (2n) through mitosis

• Meiosis 1 (FSH) stimulates) makes secondary oocytes.

• Meiosis (II) begins in fertilization.

• 1 egg, 3 polar bodies.

• Starts prior to birth, ends at fertilization

OOgenesis

Fertilization

• Fusion of sperm and ovum nuclei– Begins with Acrosome Reaction

• The Acrosome (sperm head) releases hydrolytic enzymes that penetrate egg coating

• Once sperm is bound to the egg receptors- no other sperm can enter.

– Acrosome Reaction sets up the Signal Trasnduction Pathway

• Large Amounts of Ca++ released• Cortical Reaction: Ca++ causes the vitelline

membrane to become a hard fertilization envelope• Rise in Ca++ Causes egg to develop.

Conception

Fertilization: Parthenogenesis

• Development of an unfertilized egg through electrical stimulation or injections of Ca++

• Natural Parthenogenesis occurs in Drone Honeybees (unfertilized eggs haploid males/ drones), and some lizards and sharks

Girls Rule

Embryonic Development.

• Three stages: – Cleavage: Mitotic and forms a blastula

(blastomeres = cells, blastocoel = fluid)• Protosomes: spiral and determinant cleavage

– Determinant= each cell is destined to become X, without which a complete embryo can not form.

• Deuterostopmes: radial and indeterminate (stem-cells)

– Gastrulation– Organogenesis

Embryonic Development Cont..

• Gastrulation: blastula forms a blastopore.– Protostomes: Mouth– Deuterostomes: Anus

• Archenteron cavity/ primitive gut is formed at the blastopore.

• The three layers– Ectoderm: skin and nerves– Endoderm: viscera, lungs, liver, digestive organs– Mestoderm: Muscle, blood, bones (sponges and

cnidarians make a mesoglea instead)Actual Footage

GastrulationAnimation

Embryonic Development Part III

• Organogenesis: cells differentiate into organs. – Cells fold, split and cluster (condensation)

• When organ system

has been developed

the embryo simply

increases in size.

Folding

The Frog Embryo

External Fertilization Creates a Vegetal Pole (Yoke) & Animal Pole (Top) w/ Pigmented Cap which rotates toward point of sperm penetration. A gray crescent appears opposite the penetration point forming the blastopore.

• Involution, when cells stream into the blastopore over the dorsal lip.

• Epibolic movement creates the archenteron from the blastocoel.

• Organogenesis: notochord (spine), & neural tube (CNS)

• Finally metamorphosis turns tadpole to frog.

Poles explained

The Bird Embryo

• A blastodisk sits on top of the yolk. A primitive streak forms (no gray crescent) cell involution creates the archenteron.

• Yolk reduces with cleavage and gastrulating. • Four embryo membranes:

– Yolk sac: encloses the yolk– Amnion: encloses the embryo in amniotic fluid– Chorion: membrane under shell for diffusion of gas.– Allantois: Like the placenta. Gas exhange and holds

uric acid and nitrogenous waste.

Factors that influence embryonic development

• Cytoplasmic Determinants: Watch the movie, it’s the best, but different cells become different things depending on their polar orientation.

• The Gray Crescent: Hans Spemann explains its important & calls the dorsal lip the Primary Organizer.– Embryonic Induction One group of embryonic cells

influences another. – Hox Genes/ homeotic, homeobox genes = master

genes responsible for anatomical structures. Ie where the head and eyes go.

Hans Spemann

Hox Revisited

Hox Genes