Sexual Reproduction Topic 16

Crossing over Ovaries Diploid Ovum Fertilization Testes Gamete Sperm Haploid Zygote Homologous chromosomes Meiosis

Advantages of Sexual Reproduction Offspring are genetically diverse Better chance of surviving environmental changes

Chromosomes Humans: 46 chromosomes 23 from mother, 23 from father

Meiosis Animation http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__how_meiosis_works.html

Homologous Chromosomes Chromosomes are paired Similar size and shape Carry same genetic info

Diploid Number 2n Number of chromosomes in somatic (body) cells 2 sets of chromosomes

Haploid/Monoploid Number Half the diploid number Number of chromosomes in gametes 1 set of chromosomes

Meiosis Process of forming sex cells 2 cell divisions Meiosis 1 and Meiosis 2 Results: 4 haploid (1n) daughter cells

Haploid Cells

Describe the similarities and differences in these individuals Describe the similarities and differences in these individuals. Do you believe they are related? Explain why or why not.

Meiosis Video http://www.sumanasinc.com/webcontent/animations/content/meiosis.html

Steps of Meiosis 1st Meiotic Division Chromosomes replicate Each double stranded chromosome finds its homologous pair

Crossing Over The strands get tangled and exchange genes Leads to variation

Independent Assortment Homologous chromosomes can line up in different orders Leads to more variation

2nd Meiotic Division Both daughter cells divide again 4 haploid cells are formed

Results of Meiosis 4 daughter cells Haploid (1n) number of chromosomes

Exit Ticket Explain the significance of crossing over and independent assortment. If a fish has 20 chromosomes in her diploid cells, how many chromosomes will be in each of her eggs?

Gametogenesis Formation of gametes (sex cells) Spermatogenesis Oogenesis

Spermatogenesis Testes produce sperm Primary sex cell → meiosis→ 4 haploid cells

Results of spermatogenesis: 4 motile sperm

Oogenesis Ovaries produce eggs (ova/ovum) Primary sex cell → meiosis → 1 larger ovum + 3 polar bodies Unequal division of cytoplasm Polar bodies disintegrate

Results of oogenesis: 1 non-motile ovum

Types of Fertilization Internal Occurs inside female Usually terrestrial animals Few eggs produced Development internal or external

Types of Fertilization External Occurs outside of the body Usually aquatic animals Many eggs produced Development external

Zygote Formation Zygote- fertilized egg Egg + Sperm = Zygote Fertilization- process of combining chromosomes Zygote is diploid

Fertilization Zygote Cleavage

Embryo Formation Zygote will divide by mitosis Cleavage- series of mitotic divisions of the zygote Differentiation- cells will become specialized

Embryo Formation Morula- solid ball Blastula- hollow ball of cells Gastrula- 3 germ layers

Germ Layers Ectoderm- outer layer Becomes nervous system, epidermis, nails, hair, & sweat glands

Germ Layers Mesoderm- middle layer Becomes bones, muscles, blood vessels, dermis, reproductive & excretory systems

Germ Layers Endoderm- inner layer Becomes digestive tract, trachea, bronchi & lungs

Embryo Formation http://www.youtube.com/watch?v=UgT5rUQ9EmQ

Human Reproduction

Male Reproductive System 2 major functions: 1. Make sperm 2. Deposit in female (internal fertilization)

Structures and Functions: 1. Scrotum: keeps sperm 2-4 degrees cooler than normal body temperature

2. Testes: Male gonads Seminiferous Tubules: small, coiled tubes within the testes where sperm form Testosterone produced

3. Epididymis: stores sperm while they mature 4. Vas Deferens: a 3. Epididymis: stores sperm while they mature 4. 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.

Fluids which provide nutrients to sperm are produced in: Semen: sperm + fluids Fluids which provide nutrients to sperm are produced in: 5. Bulbourethral (Cowper’s) Gland 7. Seminal Vesicles 9. Prostate Gland .

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)

Estrogen and Progesterone: a. regulate secondary sex characteristics b. regulate menstrual cycle

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

6. Vagina: birth canal (menstruate through here too) 7 6. Vagina: birth canal (menstruate through here too) 7. Cervix: base of uterus

The Menstrual Cycle http://www.youtube.com/watch?v=8qrWlf0bXpU&feature=related

Menstrual Cycle Series of changes in ovaries and uterus Begins at puberty Ends at menopause (45-55 years old) Pregnancy stops the cycle temporarily

The Menstrual Cycle

Follicle Stage – 10 Days Uterine lining thickens Egg matures in follicle & swells Pituitary Gland → Follicle Stimulating Hormone (FSH) Ovaries → Estrogen

Ovulation – 1 day Egg released from follicle Remains in oviduct for 2-3 days Pituitary Gland → Luteinizing Hormone (LH)

Corpus Luteum – 14 Days Follicle dies, forming a scar (corpus luteum) Uterine lining stays thick Corpus luteum → Progesterone

Menstruation If the egg was not fertilized- uterine lining breaks down and is shed Cycle begins again

Internal Development in Placental Mammals Development inside the female uterus

1. Placenta Forms inside uterus Feeds fetus- nutrition Exchange of gases- respiration Removal of fetus wastes- excretion All occurs by DIFFUSION No direct contact between mother & fetus bloodstreams

2. Oviduct Fallopian tube- transports egg from ovary to uterus 3. Uterus Muscular organ where fetus develops

4. Umbilical Cord 5. Fetus Attaches placenta to fetus Transports nutrients, gases and wastes 5. Fetus Developing baby

6. Amniotic Sac Filled with amniotic fluid Protects fetus

Multiple Embryos Identical Twins- 1 egg, 1 sperm Zygote splits into 2 during cleavage 1 placenta, 1 amniotic sac Fraternal Twins- 2 eggs, 2 sperm Separate placentas & amniotic sacs

Artificial Insemination Sperm artificially inserted into female

In Vitro Fertilization Fertilization takes place in a petri dish Zygote then implanted into uterus

Amniocentesis Amniotic fluid extracted Chromosomes of fetus analyzed

Kangaroo Birth http://www.youtube.com/watch?v=2lCKc8tURtc

http://blog.savcds.org/swanson/files/2010/12/chromosome.gif http://www.phschool.com/science/biology_place/labbench/lab3/images/homologs.gif

STUDENT VERSION http://www.lew-port.com/10712041113402793/lib/10712041113402793/animations/meiosis.html