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Reproduction - Coggle Diagram
Reproduction
Sexual reproduction
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Asexual
this involves 3 mechanisms of fission, budding, and fragmentation
parthenogensis literally means virgin birth and is when some animals produce an egg without fertilisation and is often used when conditions are favourable for mass offspring
it creates genetic variation via fusion of gametes produced by meiosis and this diversity increases chance of survival if environment changes
Internal fertilisation
fertilisation requires an internal or external medium which allows teh sperm to swim to the egg, using ferimones released by the egg to pull the sperm towards it
internal is beneficial since external has risks of wind which may move them and fish which may eat them
Types
Oviparous
spiders, birds and reptiles young hatch out of an external egg that is laid
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the egg provides nutrients for development and have waterproof membranes or shells protect from desiccation
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Viviparous
the mother retains the young and provide nourishment and waste removed through exchanges with mother tissue
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Copulation is the physical joining of male and female accessory sex organs, but sperm transfer can also be indirect (like with spermatophores)
Mating systems
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Promiscuous is when male has less involvement in paretning but they live in a troop so still protect their own genes
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Hermaphroditism
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Simultaneous
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the benefit is that if an organism density is sparse th eindividual does not need an individual with different gonads it just needs another indivdual
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Female
Anatomy
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teh opening of the fallopian tubes lead into the uterus and down into the cervix out through the vagina
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Egg
stored nutrients and factors needed for early embryo development since initially no links to placenta
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the cell is surrounded by cell sof corona radiata adn the zona pellucida hardens, these prevent polyspermy
Hormones
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Hormonal control
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For the first 12 dats oestrogen exerts postive feedback on pituitary so a surge in LH and lesser FSH occur, the LH surge triggers mature follicle rupturing and stimulates corpus luteum development
Oogenesis
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primary oocytes immediately enter prophase of first meiotic division. There is a decline in number between 16-24 weeks because of apoptosis and the oocytes experience developmental arrest so they remain in this state until puberty (but there is steady decay between birth and puberty by atresia)
during this prolonged prophase I the primary oocytes development (grow larger, increased organelle, ribosome, RNA and energy store production)
Once meiosis resumes the daughter cell recieves uneven shares of cytoplasm, the daughter cell that receives almost all the cytoplasm becomes th esecondary oocytes and the other the first polar body
The second meiotic division of the secondary oocyte produces a large, haploid ootid (which differentiates to egg) and a second polar body
the polar bodies are usually degenerated but few species have evolved so they reproduce parthenogenetically so a polar body fuses with egg to restore diploid
Ovarian cycle
Follicular phase
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the promordial follicle develops into primary follicle and sits there until puberty, the primary follicle begins to develop an antrum formation
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The follicle lies on the ovary wall and ruptures it and the ovum is ovulated and ultimately goes up the fallopian tube towards the uterus
oestrogen secreted to circulation from thecal interna cells and follilcular fluid from granulosa cells; and the dominant follicle is achieved by oestrogen secretion
ovulation at day 14, big peak in LH and FSH
Luteal phase
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this secretes oestrogen and progesterone to support the possible pregnancy and degenerates if no pregnancy
Uterine Cycle
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Day 5-14 is proliferation phase so lining of uterus builds up in preparation to receive the blastocyst and little secretion in uterine tissue
if no blastocyte is received the endometrium breask down, the lining is lost when corpus luteum is lost
driven by progesterone (vascularisation, coiled glands and fluid secretion) since secreted by cortus luteum
Male
development
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this protein initiates production of multiple proteins that cause gonad medulla to differentiate into tests
the testes has Leydig cells that secrete testosterone and Sertoli cells that secrete Anti-Mullerian hormone
Anatomy
The accessory sex glands are seminal vesicles, bulbourethral and prsotate glands produce supporting secretion into the tract that support function of the system as a whole
the testes hang because of the lower temperature (androgen insensitivity syndrome is a male with female features as testes don't drop)
teh epididymis, vas deferens and urethra are involved in storage and release of sperm
Testosterone
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effects
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promotes growth and maturation of system at puberty, adn is needed for spermatogenesis and maintenance of tract as an adult
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controls gonadotrophin hormone secretion and has protein anabolic effect to build up bone and tissue
Spermatogenesis
Sperm are hughly specialised to carry genetic material a relatively far distance, like many mitochondria adn the head has acrosomal vesicles to digest through the ovum when they bind and nucleus to hold genetic material
There is proliferation of male germ cells (2n) into spermatogenia (2n) by mitosis, which then continue to divide by mitosis
When the spermatogonium divide, one daughter cell remains at the outer edge of semiferous tubult to maintain the germ cell line and the other moves to the lumen for further mitosis
The primary spermatocyte undergoes the first meiotic division (the reduction division) to form 2 secondary spermatocytes (n)
the second meiotic division produces 4 haploid spermatids, the mammalian spermatocytes remain in cytoplasmic contact (with cytoplasmic bridges)because of assymetry of sex chromosomes: half recieve an X, the other a Y, and the X chromosome contains genes essential for sperm development so cytoplasmic connection is needed
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