Transcript Reproduction

Reproduction
Review
• Asexual Reproduction
– One parent
– No reproductive organs
– No genetic variation
– Mitosis and Cytokinesis
– Binary Fission, Budding,
Spores, Regeneration,
Vegetative Propagation
Review
• Sexual Reproduction
– Two parents
– Sex cells
– Meiosis
– Genetic variation
• Survival of species
Sexual Reproduction in Lower
Organisms
• Conjugation
– Conjugation bridge
– Exchange or transfer of genetic
material
– No male/female
– Bacteria, paramecia, spirogyra
Spirogyra
Zygote develops tough coat and
now called a Zygospore
Zygospore hatches when conditions
favorable
Sexual Reproduction in Animals
• Have Male and Female
• Have sex organs (Gonads)
– Ovaries-Ova or eggs (Haploid)
– Testes-Sperm (Haploid)
Sexual Reproduction in Animals
• Hermaphrodites
– Ovaries and testes in same animal
– In slow or sessile organisms (worm ,hydra
snail)
– Self fertilization rare
How are gametes made?
• Gametogenesis
– Oogenesis
– Spermatogenesis
Spermatogenesis & Oogenesis
2n
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Sperm vs. Egg
Sperm
Small
Many
Mobile (1-4mm/min)
Complex shape
Egg
Larger
Few
Nonmobile
Round
May have Yolk
Sperm
Digestive Enzymes
Energy to swim
Fertilization
• Sperm swim to egg
• Sperm releases enzymes to make hole in
egg
• Sperm injects nucleus into egg
• Fertilization membrane form around egg
• No future fertilization
• Joining of sperm nucleus and egg nucleus
• Form diploid zygote
Where can fertilization happen?
1. Outside female (External Fertilization)
2. Inside Female (Internal Fertilization)
External Fertilization
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Female releases eggs in water
Male releases sperm in water
Problems?
Sperm find eggs
Many gametes made!
Spawning behavior or Amplexus
Seasonal spawning of Salmon
Amplexus
Internal Fertilization
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Safer
Terrestrial animals and some aquatic
Need moist female repro. tract
Fewer eggs needed
Short life span of gametes (24hrs)
Need specialized organs
Timed release of gametes (Hormonal)
Adult with no fertilization?
• Parthenogenesis
– Egg develops without sperm
– Insects
– Unfertilized eggs of queen bee=male drone
– Fertilized eggs of queen bee=female workers
or queens
What happens after fertilization?
• Development
• Embryology=Study of embryo
development
Stages of Development
1. Cleavage
– Mitotic cell divisions
– 2 cells, 4, 8,…..morula=solid ball of cells
– No growth in cell size (cells get smaller)
Development
• Cleavage
– Blastula stage=Ball hollows out and has fluid
in core (Blastocoel)
Cells with
yolk
Development
2. Gastrulation
– Growth in cell size
– Embryo changes
shape (cells migrate)
Development
• Gastrula:
Development of
3 Primary Germ
Layers
Mesoderm
Development
• Ectoderm:
– Nervous sys, lining of mouth, nostrils and anus
– Epidermis, hair, nails
• Mesoderm:
– Bone, muscles, blood vessels, repro and excretory
system, dermis
• Endoderm:
– Lining of digestive sys, respiratory sys, liver,
pancreas, glands, bladder
Development
3. Differentiation
– Embryonic cells become specialized
– Embryonic Induction=“organizers” influence
cells to take on a certain role in life
– Where cell is located will determine what it will
become
Differentiation
• Ex. Nerve cord
development
External vs. Internal Development
• External:
– Water
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Embryo feeds on yolk
Wastes and Oxygen exchange via diffusion
Little to no care, dangerous
Ex. Many fish
External vs. Internal Development
• External:
– Land
• Embryo feeds on yolk in a
SHELLED egg
• Pores in shell for gas exchange
• Ex. Reptiles (Leathery Shell)-leave
eggs
• Ex. Birds (Hard Shell)-protect eggs
Extraembryonic membranes of Bird
Eggs
Embryo
• Yolk sac=Nutrients
• Amnion=shock
absorption
• Allantois=metabolic
waste storage and gas
exchange
• Chorion=under shell,
gas exchange
External vs. Internal Development
• Internal
– Some organisms: nutrients mostly from yolk and
babies born self-sufficient
– Others: development in womb (Uterus)
– High protection
– Little yolk, nutrients from mom
– Born undeveloped
– Mammals continue to feed via mammary glands
Placental vs. Nonplacental
Mammals
• Placental
– Have placenta=site of
nutrient and waste
exchange between
mom and baby
– Baby side and mom
side with space
between
– No blood-blood
contact
Placental vs. Nonplacental
Mammals
• Nonplacental:
– **Egg-laying mammals (External Development)
Monotremes
• Ex. Spiny anteater and duckbill platypus
• Eggs with yolk develop outside
• Babies feed on mammary gland milk
Placental vs. Nonplacental
Mammals
• Nonplacental
– Pouched mammals (Marsupials)
– Some internal development
– Poorly developed babies born and remain in a
pouch feeding on milk
– Ex. Opossum, Kangaroo
Link
Human Male Reproductive System
Human Male Reproductive System
Parts
• Testes:
– Semineferous tubules
– Sperm production
– Testosterone production
– In scrotum sac
• Epididymis
– Sperm storage and maturation site
Parts
• Vas deferens
– Sperm ducts
• Urethra
– Exit route for sperm through penis
• Glands:
– Seminal vesicles=thick, nutrient-rich fluid
– Cowper’s Gland (Bulbourethral glands)= preejaulation
lubricant
– Prostate Gland=milky, alkaline fluid
(Semen is sperm and fluids)
Human Female Reproductive
System
Human Female Reproductive
System
Oviduct
Parts
• Ovaries
– matures eggs located in follicle sacs
– Make estrogen
– Usually one egg matures/month
– Mature egg ovulated
– Egg enters oviducts
Parts
• Oviduct
– Site of fertilization
• Uterus
– Site of embryo development
• Cervix
– Doorway into Uterus
• Vagina
– Birth canal and sperm receiving area
Human Sexuality
• Fertilization
– Hundreds of millions of
sperm ejaculated into
vagina
– Fertilization in oviduct
• (In vitro vs. in vivo
fertilization)
Fraternal vs. Identical Twins
“Identical” Twins may
have some genetic
differences.
Can have difference in
quantities of a gene
(Am. J. Human
Genetics)
• Cleavage as zygote moves
towards the uterus
• Implantation and Gastrulation
– Ectopic pregnancy
Human extraembryonic
membranes
• Chorion=surrounds other membranes
– Chorionic villi
– Villi+uterine wall=placenta
• Placenta=Nutrient exchange, no blood-blood
contact
• Amnion=Surrounds fetus
– Amniotic Fluid-shock
• Yolk Sac and Allantois develop into
umbilical cord
Birth
• Gestation Time= Time in womb
– 9 months for humans
– 20 days for mouse
– 21 months for elephant
• Labor
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uterine contractions
Cervix enlargement
Amnion breaks
Baby’s head out first
• Afterbirth
– Placenta comes out
Terms
• Embryo= zygote from fertilization till 8
weeks
• Fetus= 8 weeks-birth
Menstrual Cycle
Starts at Puberty
(10-14 years
old)
Stops at
Menopause
(45-50 years
old)
Stages
1. Follicle Stage
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FSH from Pituitary matures one follicle
Follicle secretes Estrogen
Estrogen enhances Uterine Lining
High Estrogen levels inhibit Pit. From
secreting FSH
Pit. Starts to secrete LH
Days 1-13
Stages
2. Ovulation
– High levels of LH cause egg to pop out of follicle
– Day 14
3. Corpus Luteum Stage
– Ruptured follicle (ie. “corpus luteum”) releases
Progesterone
– Progesterone maintains uterine lining (Hormone of
Pregnancy)
– Progesterone inhibits FSH release
Stages
4. Menstruation
– If no fertilization:
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LH levels drop
Corpus luteum breaks down
Progesterone levels drop
Estrogen levels drop
Uterine lining shed
FSH no longer inhibited
Start maturing a new follicle
Estrous Cycle
• Only humans and other primates have
menstrual cycle
• Other have Estrous Cycle
– Periodic changes in female sex organs
– Periodic desire to mate
– Seasonally fertility (In Heat)