Animal Reproduction and Development Flashcards
~Asexual Reproduction
● Produced offspring genetically identical to the parent
● Includes budding, fragmentation/regeneration, parthenogenesis
~Budding
● Involves the splitting off of new individuals from existing ones
● Hydra
~Fragmentation and regeneration
● Occurs when a single parent breaks into parts htat regenerate into new individuals
● Sponges, planaria, starfish
~Parthenogenesis
● Involves the development of an egg without fertilization
● Resulting adult is haploid
● Honeybee, whiptail lizards
~Sexual reproduction
● Each offspring is the product of both parents
~Epididymis
● Tube in the testes where sperm gain motility
~Leydig cells
● Clusters of cells located between seminiferous tubules that produce testosterone
~Prostate gland
● Large gland that secrete semen directly into the urethra
~Scrotum
● Sac outside the abdominal cavity that hodes the testes
● Cooler the temperature there enables sperm to survive
~Seminal vesicles
● Secrete mucus, fructose sugar (which provides energy for the sperm) and the hormone prostaglandin during sexual intercourse
~Prostaglandin
● Stimulates uterine contractions
~Seminiferous tubules
● Sites of sperm formation int he testes
~Sertoli cells
● Provide nutrients for developing sperm
~Testes/testis
● Male gonads, where sperm are produced
~Urethra
● Tube that carries semen and urine
~Vas dferens
● Muscular duct that carries sperm during ejaculation from the epididymis to the urethra in the penis
~Ovaries
● Where meiosis occurs
~Oviducts/Fallopian tubes
● Where fertilization occurs
● After ovulation, the egg moves through the oviduct to the uterus
~Uterus
● Where blastocyst will implant and where the embryo will develop during the nine-month gestation if fertilization occurs
~Endometrium
● Lining of the uterus that thickens monthly in preparation for implantation of the blastocyst
~Vagina
● Birth canal
● During labor and delivery, the baby passes through the cervix and into the vagina
~Cervix
● The mouth of the uterus
~Follicular phase
● Several follicles in the ovaries grow and secrete increasing amounts of estrogen in response to follicle-stimulating hormone (FSH) from the anterior pituitary
~Ovulation
● Secondary oocyte ruptures out of the ovaries in response to luteinizing hormone
~Luteal phase
● Corpus luteun forms in response to luteinizing hormone
● It is the follicle left behind after ovulation and secretes estrogen and progesterone, hwich thicken the endometrium of the uterus
~Menstruation
● The monthly shedding of hte lining of the uterus when implantation of an embryo does not occur
~Positive feedback in the menstrual cycle
● Enahces a process until it is completed
● During the follicular phase, estrogen released from the follicle stimulates hte release of LH from the anterior pitruitary
● The increase in LH stimulates the follicle to release even more estrogen
● The hormone levels continue to rise until the follicle matures and ovulation occurs
~Negative feedback in the menstrual cycle
● Stops a process once homeostasis is reached
● During the luteal phase, LH stimulates the corpus luteum to secrete estrogen and progesterone
● Once the levels of estrogen and progesterone reach sufficiently high levels, they trigger the hypothalamus and pituitary to shut off, thereby inhibiting the secretion of LH and FSH
~Spermatogenesis
● Process of sperm production
● Contiuous process that starts at puberty
~Oogenesis
● Production of ova
● Begins prior to birth
● Within the embryo, an oogonium cell (2N)
- These remain quiescent within small follicles in the ovaries until puberty, when they become reactivated by hormones
● FSH periodically stimulates the follicles to complete meiosis I, producing secondary oocytes (N), which are released at ovulation
● Meiosis II then stops again and does not continue until fertilization, when a sperm penetrates the secondary oocyte
~Fertilization
● Fusion of pserm and ovum nucleic
● Begins with the acrosome reaction
● Specific recognition
~Acrosome reaction
● The head of the sperm (acrosome) releases hydrolytic enzymes that penetrate the jelly coat of the egg
● Specific molecules from the sperm bind with receptor molecules on the vitelline membrane before the sperm come in contact with the ovum’s plasma membrane
~Specific recognition
● Ensures that the egg will be fertilized by only sperm from the same species
~Fast block to polyspermy
● Lasts only a minute but just long enough to allow the slow block to polyspermy
● Once a sperm binds to receptors ont he egg, the membrane is dramatically depolarized and no other sperm can penetrate the egg membrane
~Slow block to polyspermy
● Converts the vitelline membrane into an impenetrable fertilization envelope
~8Parthenogenesis
● Development of an unfertilized egg
● An unfertilized egg can be activated artificially by electrical stiulation or by injection with Ca ions
● Resultin adult is haploid
~Drone honeybees
● Develop by natural parthenogensis from unferilized eggs and are haploid males
~Embryonic devel[opment
● Consists of three stages: cleavage, gastrrulation and organogenesis
~Sea urchin egg
● Eggs with almost no yolk
● Typical embryonic development
~Frog egg
● In eggs with more yok, such as those of the frog, cleavage is unequal, with very little cell division in the tyoky region
~Bird egg
● In eggs with a great deal of yolk, such as a bird egg, cleavages is limited to a small, nonyolky disc at the top of the egg
~Cleavage
● Rapid mitotic cell division of the zygote that occurs immediately after fertilization
● Produces a fluid-filled ball of cells caleld a blastula
● Embryo at this stage is called a blastocyst in mammals
● Clustered at one end of the blastocoel cavity is a group of cells called the inner cell mass
~Inner cell mass
● Will develop into the embryo
~Pluripotent
● THe cells of the very early blastocoel stage are pluripotent
● Are the source of embryonic stem cell lines
~Trophoblast
● The cells that surround the inner cell mass
● Secrete fluid, creating the blastocoe., and also form sturcutres that will atach the embryo to the mother’s uterus
~Differentiation
● THe cells of the blastocyst or balstula communicate with each other and begin to differentiate
● In many animals, the movement of the cells is so regular that it is possible to leabel a specific blastomere (individiaul cells of a blastocyst) and identify the tissue that results as embryonic development proceeds
- Produces a fate map
~Gastrulation
● Process that involves rearrangement of the blastula or blastocyst and begins with the formation of the blastopore, an opening into the blastula
- In some animals, the blastopore become shte mouth, in others (deuterostomes), the blastopore becomes the anus
~Archenteron/primitive gu
● Some of the cells on the surface of the embryo migrate into the blastopore to form a new cavity
● As a result of this cell movement, gastrulation froms a three-layered embryo
~Gastrulation
● The three embryonic germ layered embryo formed by gastrulation
● Includes ectoderm, endoderm, and mesoderm
~Ectoderm
● Will become the skin and the nervous system
~Endoderm
● Will form the viscera including the lungs, liver, and digestive organs, and so on
~Mesoderm
● Will give rise to the muscle, blood, and bones
● Some primitive animals (sponges and cnidarians) develop a noncellular layer, the mesoglea, instead of the mesoderm
~Organogenesis
● Organ building
● Process by which cells continue to differentiate, producing organs from the three embryonic germ layers
● Three kinds of morphogenetic changes–folds, splitsn and dense clustering called condensation–are the first evidence of organ building
● Once all the organ systems have been developed, the embryo simply increases in size
~Fertilization in frog embryo
● Eggs are laid directly into water and fertilization is external
● When the sperm penetrates the egg, the pigementaed cap rotates toward hte point of penetration and a gray crescent appears
● Animal-vegetal asymetry dictates where the anterior-posterior axis forms in the embryo
~Vegetal pole
● One third of the frog egg is yolk, which is massed in the lower portion of the egg called vegetal pole
~Animal pole
● The top half is called animal pole and has a pigmented cap
~Gray crescent
● Appears ont he side opposite the point of entry of hte sperm
● Marker of the future doral side and is critical to normal dvelopment of hte growing embryo
~Cleavage and gastrulation in frog embryo
● Because of the presence of yolk, cleavage is uneven
● The blastopore forms at the border of the gray crescent and the vegetal pole
● Involution occurs
● A ectoderm cells stream inward by what is called epibolic movement, the blastocoel disappears and is replaced by another cavity called the archenteron
~Involution
● Cells at the dorsal lip above the blastopore begin to stream over the dorsal lip and into the blastopore
~Drorsal mesoderm
● THe region of mesoderm lining the archenteron that formed opposite the blastopore is caleld dorsal mesoderm
~Organogenesis in frog embryo
● In chordates, the organs to form first are the notochord and the neural tube
● Both notochord and neural tube form by embryonic induction
● After the blueprints of the organs are laid down, the embryo develops into a larval stage, the tadpole
● Metamorphisis will transofmr the tadpole into a frog
~Notochord
● The skeletal rod characteristic of all chordate embryo
~Neural tube
● Which will become the central nervous system
● Forms from the dorsal ectoderm just above the notochord
~Cleavage and gastrulation in bird enbryo
● The bird’s egg has so much yolk that development of the embryo occurs in a flast disc of blastodisc that sits on top of the yolk
● A primitive streak forms instead of a gray crescent
● Cells migrate over the primitive streak and flow inward to form the archenteron
● As cleavage and gastrualtion occur, the yolk gets smaller
~Extraembryonic membranes
● Tissue outsid the embryo forms four extraembryonic memrbanes necessary to support hte growing embryo inside the shell
● THey are the yolk sac, amnion, chorion and allantois
~Yolk sac
● Encloses the yolk, food for the growing embryo
~Amnion
● Encloses the embryo in protective amniotic fluid
~Chorion
● Lies under the shell and allows for the diffusion of respiratory gases between the outside and the growing embryo
~Allantois
● Analogous to the placenta in mammals
● COnduit for respiratory gases between the environment and the embryo
● Also the repository for uric acid, the nitrogenous waste from the embryo that accumulates until the chick hatches
~Cytoplasmic determinants
● The dissection of eight-ball embryo demonstrates that hte cytoplasm surrounding the nucleus has profound effects on embryonic development
● The importance of the cytoplasm in the development of hte embryo is known as cytoplasmic determinants
~Hans Spemann
● Demonstrated the importance of the cytoplasm associated with the gray crescnet in the normal development of the animal
● He dissected embryos in the two-ball stage in different ways
- Only the cell containing the gray crescent developed normally
~Embryonic induction
● The ability of one group of embryonic cells to influence hte development of another group of embryonic cells
● Spemann proved that hte dorsal lip of the blastopore normally initiates a chain of inductions that results in the formation of a neural tube
~Apoptosis
● Programed cell death
● Many more neurons are produced during development of the vertebrate nervous system thatn exist in teha dult
- This is because neruons survive if they make connections iwth other neurons during developemtna nd self-destruct if they do not
~Webbing
● During early embryonic development, it connects hte spaces between fingers and toes
● As developmetn proceeds, cells that make up the webbing undergo apoptosis
● The webbing is eliminated and the fingers and toes can separatej
● Sometimes a human baby is born with some residual webing, the result of incomplete embryonic development
~Homeotic/homeobox/hox genes
● Master regulatory genes that control the expression of genes that regulate hte placement of specific anatomical structures
● Play a critical role in normal embryonic development
~What advantagaes do asexual reproductions have over sexual reproductions?
● Enable animals living in isolation to reproduce without a mate
● Can create numerous offsrping quickly
● No expenditure of energy-maintaing reproductive systems or hormonal cycles
● Because offspring are clones of the parent, it is advantageous hwen the environment is stable
~What advantages do sexual reproductions have over asexual reproductions?
● Genetic variation
● May be better able to survive than either parent, especially in an environment that is changing
~What does the human male reproductive system include?
● Epididymis ● Leydig cells ● Prostate gland ● Scrotum ● Seminal vesicles ● Seminiferous tubules ● Sertoli cells ● Testes ● Urethra ● Vas deferens
~What does the human female reproductive system include?
● Ovaries ● Oviducts/Fallopian tubes ● Uterus ● Endometrium ● Vagina
~What are the four phases in menstrual cycle?
● Follicular phase
● Ovulation
● Luteal phase
● Menstruation
~What stimulates the beginning of pserm production?
● Begins as LH induces the interstitial cells of the testes to produce testosterone
● Together with FSH, tetosterone induces maturation of the seminiferous tubules and stimulates the beginning of sperm production
~What happens in Spermatogenesis?
● In the seminiferous tubules, each spermatogonium cell (2N) divdies by mitosis to produce two primary spermatocytes (2N)
- Each undergoes meiosis I to produce two secondary spermatocytes (N)
- Each secondary spermatocyte then undergoes meiosis II, which yields 4 spermatids (N)
● These spermatids differentiate and move to the epididymis where they become motiel
~How does oogenesis differ from sperm formation?
- Stop-start process
● It begins prior to birth and is completed after fertilization - Cytokinesis divides the cytoplasm of the cell unequally, producing one large cell and two small poar bodies which will disintegrate
- One primary oogonium cell gproduces only one active egg cell
What is the future development of the two halves of embryo depended on?
● Plane in which they are cut
● If the dissection is longtudinal, producing embryos containing cell sfrom both animals and vegetal poles, subsequent development is normal
● If the plant fo dissection is horizontal, the result is four abnromally developing embryo
~What was Spemann’s experient that proved the dorsal lip of the blastopore normally initiates a chain of inductions htat results in the formation of a neural tube?
● He grafted a pice of dorsal lip from one amphibian embryo onto the entral side of a second amphibian embryo
● What developed on the recipient was a complete secondary embryo attached at the site of the graft
● THe dorsal lip induced the abdomen tissue above it to become neural tissue
~What did Spemann name the dorsal lip and why?
● Because it plays a crucial role in development, Spemann named hte dorsal lip the primary embryonic organizer or simply the organizer
● Scientists now have identified that the protein beta-catenin is a likely candidate for the transcription factor that triggers which cells become the organizers
