Reproduction & Development Flashcards
Binary Fission
- Prokaryotes, algae, bacteria
- Key step - DNA replication
- Only 1 chromosome in a single long circular DNA;
- Gets attached to cell membrane and replicated as the cell grows
- DNAs are drawn apart when cell grows and adds more membrane between the DNAs
Conjugation
- primitive form of sexual reproduction used by bacteria
- move genes between cells by exchanging a circular extrachromosomal DNA with eachother
- individuals exchange genetic information
Transduction
- viruses that infect bacteria can accidentally carry bacterial genes with them into a new cell they infect
- introduce new genes into bacteria
Cell Cycle
Interphase
- Stage G1 - intense biochemical and biosynthetic activity - growth - cell doubles in size - new organelles are produced
- Stage S - synthesis - DNA replication - chromosomes each consist of 2 identical sister chromatids held by centromere, ends are called telomeres
- Stage G2 - prepares for mitosis
**Stage M (Mitosis and Cytokinesis) **
Advantages of Asexual reproduction
- enables animals living in isolation to reproduce without a mate
- creates many offsprings quickly
- no expenditure of energy to maintain complex reproductive systems or hormonal cycles
- when the environment is stable and favorable
- mechanism for perpetuating primitive organisms and plants, especially in times of low population density
Budding
- unequal division of cytoplams, but equal division of the nucleus
- yeast, hydra
- parent cell forms smaller daughter cell that sprouts off with less cytoplasm
- the daughter organism becomes independent and is released
- splitting off new idnividuals from existing ones
Parthenogenesis
- Asexual Reproduction (in animals)
- egg develops without fertilization by sperm
- occurs naturally in bees
- fertilized eggs develop into worker bees and queen bees
- unfertilized eggs become male drone bees
Regeneration
• Asexual Reproduction
Ability to regrow a missing body part
- Fragmentation – single parent breaks into parts that regenerate into new individuals
- Ex/ Sponges, planaria, earthworm, lobster, sea star, plants
Gonads
specialized organs that produce gametes through meiotic cell division
- Male - testes - produce sperm
- Female - ovaries - produce ova
Germ cell
- A cell that is committed to the production of gametes
- Diploid; not a gamete
- Its genome contributes to gametes and offspring
- Mutations in somatic cells won’t be passed on
Testes
- Male gonads
- Site of sperm formation
- Produce male hormones(testosterone)
semniferous tubuoles - support the stem
Vas deferens
Duct that carries sperm during ejaculation from the epididymis to the penis
Prostate gland
secretes semen directly into the urethra
Scrotum
- sac outside the abodminal cavity that holds the testes
- cooler temperature enables sperm to survive
Urethra
• Tube that carries urine and semen
Spermatogenesis
- Begins as luteinizing hormone(LH) induces the testes to produce testosterone
- FSH and testosterone stimulate sperm production
• Produces 4 mature sperm; each sperm has an X or Y chromosomes and doesn’t donate mitochondria to the embryo
• Continuous process
• Produces fresh sperm daily
• Spermatogonium(2n) –(Mitosis)–> Primary Spermatocyte(2n) –(Meiosis I)–> 2 Secondary spermatocyte(n) –(Meiosis 2)–> 4 spermatids(n) —-> 4 spermatozoa(n)
o Specialized sac called acrosome on sperm tip has enzymes that break through protective layers around the egg
Oogenesis
- produces 1 egg and 3 polar bodies
- begins prior to birth; a female is born with all the primary oocytes she will ever have
- produces ova with only X chromosomes and donates mitochondria to the embryo
- discontinuous process
- ova progress to meiosis I and gets stuck at this stage; ova that mature during each menstrual cycle progress through this meiotic block
- primary oocyte remains inactive within follicles in the ovaries until puberty, when they become reactivated by hormones
- Oogonium(2n) –(mitosis)–> Primary Oocyte(2n) –(Meiosis I)–> Secondary Oocyte(n) & 1st polar body(n) –(Meiosis II)–> Ovum(n) & 2 2nd Polar Bodies(n)
Ovaries
female gonad
where meiosis occurs and where the secondary oocyte forms prior to birth
one ova develops each month within a follicle in an ovary
Fallopian tube/ Oviduct
- where fertilization occurs
- after ovulation, egg moves through the oviduct to the uterus
Uterus
where the blastula stage of the embryo will implant and develop during the nine-month gestation
vagina
birth canal; during labor and delivery, the baby passes through the cervix and into the vagina
Cervix
mouth of the uterus
Endometrium
lining of the uterus
Menstrual Cycle
- Follicular Stage
- Ovulation
- Corpus Luteum Stage
- Menstruation
key hormones - GnRH, FSH, LH, estrogen, progesterone
cycle that repeats every 28 days
Follicular Phase
- 1st stage of Menstrual Cycle
- Follicles(tiny cavities) grow/mature in the ovaries and secrete increasing amounts of estrogen in response to follicle-stimulating hormone(FSH) from the anterior pituitary
- Estrogen promotes thickening of the uterine lining to support an embryo if fertilization occurs
- 9-10 days
Ovulation
- 2nd stage of Menstrual Cycle
- Secondary oocyte ruptures out of the ovaries in response to a rapid surge in luteinizing hormone(LH) from the anterior pituitary
- 14th day
- Constant high levels of estrogen usually block the LH surge and block ovulation(birth control pills)
Luteal Phase
- 3rd stage of Menstrual Cycle
- After ovulation, the remains of the follicle create the corpus luteum
- LH from the pituitary stimulates it to secrete estrogen and progesterone that thicken the endometrium of the uterus; triggers vascularization(growth of blood vessels)
- Lasts 12-15 days
Menstruation
- 4th and last stage of Menstrual Cycle
- If no fertilization, the increased estrogen and progesterone block LH production
- Without LH, the corpus luteum wastes away and progesterone levels fall
- Without progesterone, the buildup of the uterus lining breaks down and is shed
- Lasts 4 days
What happens if fertilization occurs?
- The developing placenta produces HCG(human chorionic gonadotrophic hormone), which maintains the corpus luteum
- It continues to make progesterone and estrogen
- Progesterone prevents menstruation and ensures uterus lining is thickened to continue pregnancy
- The placenta develops and takes over estrogen and progesterone production during pregnancy
Hormonal Control of the Menstrual
Hypothalamus
Releases
.
.
Gonadotropic-Releasing Hormone(GnRH)
.
.
Stimulates
Anterior Pituitary
Releases
**Follicle-Stimulating Hormone(FSH) **
Luteinizing Hormone(LH)
Stimulates
.
.
Ovary
Releases
Estrogen Progesterone
Stimulates
Thickens the lining of the uterus
Fraternal Twins
- if there are 2 or more eggs released by the ovaries, more than 1 can be fertilizaed
- the result of multiple fertilizations
- dizygotic - 2 separate sperm fertilize 2 eggs
Identical twins
- monozygotic
- one fertilized egg, split during early stages of cleavage
- identical genomes
- most differences between twins caused by environment
External Fertilization
• Occurs in vertebrates that reproduce in water
- fish and amphibians
- eggs – laid in water
- sperm – deposited near eggs in the water; have flagella to swim through water to the eggs
- sperm likely to be diluted and chances of fertilization are reduced
- decreases probability of survival of the young after fertilization
Internal Fertilization
- in vertebrate land animals
- reptiles, birds, mammals
- direct route to the egg for mobile sperm
- increases the chance of fertilization
- the less parental care, the more eggs are made
Embryonic Development Stages
Zygote —– Cleavage —– Morula —— Blastula —— Gastrulation —– Gastrula —– Organogensis —— Fetus
Cleavage
- starts in the oviduct immediately after fertilization
- rapid mitotic cell division of the zygote
- creates a solid ball of cells - morula
- end of cleavage when a blastula is made
Blastula
- a hollow, fluid-filled ball of cells
- a signle layer thick
- the fliud-filled center is a blastocoel
- the individual cells are blastomeres
Gastrulation
- rearrangement of the blastula to prouce a gastrula
Gastrula
- 3-layered embryo
- 3 differentiated layers called embryonic germ layers
- ectoderm, endoderm, and mesoderm develop
ectoderm
- exterior
- skin
- nervous system
- eyes
- hair
- teeth
- sweat glands
Endoderm
- lining of digestive and respiratory tracts
- lining of the bladder, pancreas, liver
- viscera
*
Mesoderm
- develop between the ectoderm and endoderm
- muslces
- skeleton
- circulatory system
- excretory system
- gonads
- inner layer of skin(dermis)
- kidney
Organogenesis
- process by which cells continue to differentiate, prouducign organs from the 3 embryonic germ layers
- embryo increases in size and becomes a fetus
Extraembryonic membranes
- Chorion
- Yolk sac
- Amnion
- Allantois
Chorion
- lies under the shell
- alloows diffusion of respiratory gases
Allantois
- same function as placenta in mammals
- saclike structure developed from digestive tract
- respiration and excretion
- has many blood vessels to take in Oxygen and give off Carbon DIoxid, water, salt, and nitrogenous wastes
*
Amnion
- encloses embryo in amniotic fluid
- protection from shock
Yolk sac
- encloses the yolk, which is food
Placental animals
- no direct contact between teh bloodstreams of the mother and embryo
- diffusion and active transport between adjacent blood vessels of mother and embryo in teh placenta
- egss are very small
Umbilical Cord
- attaches embryo to the placenta
- composed of tissues of embryonic, not maternal, origin
- contains the umbilical artery and vein
