Animal Reproduction and Development Flashcards
Advantages of Asexual Reproduction
- It enables organisms to live in isolation without a mate.
- It can create numerous offspring quickly.
- There is no expenditure of energy maintaining reproductive systems or hormonal systems.
- Offspring are clones of the parent and is advantageous when the environment is stable.
Fission
Separation of an organism into two new cells (amoeba).
Budding
The splitting off of new individuals from existing ones (hydra).
Fragmentation & Regeneration
A single parent breaks into part that regenerate into new individuals (sponges, planaria, starfish)
Parthenogensis
The development of an egg without fertilization. The resulting adult is haploid (honeybees, some lizards).
Advantages of Sexual Reproduction
Variation; each offspring is the product of both parents and may be better able to survive than either parent in an environment that is changing
Male Reproductive System: Testes
male gonad where sperm are produced
Male Reproductive System: Seminiferous Tubules
the site of sperm formation in the testes
Male Reproductive System: Vas Deferens
the muscular duct that carries sperm during ejaculation from the epididymic to the urethra in the penis
Male Reproductive System: Seminal Vesicles
secrete mucus, fructose sugar (energy for the sperm), and the hormone prostaglandin
Male Reproductive System: Prostaglandin
stimulates uterine contractions during ejaculation
Male Reproductive System: Prostate Fland
the large gland that secretes semen directly into the urethra
Male Reproductive System: Scrotum
the sac outside the abdominal cavity that holds the testes; the cooler temperature enables the sperm to survive
Male Reproductive System: Urethra
tube that carries semen and urine
Female Reproductive System: Ovaries
where meiosis occurs and where the secondary oocyte forms prior to birth
Female Reproductive System: Oviducts & Fallopian Tubes
where fertilization occurs; after ovulation the egg moves through the oviduct to the uterus
Female Reproductive System: Uterus
where the blastocyst will implant and where the embryo will develop during the nine-month gestation if fertilization occurs
Female Reproductive System: Endometrium
the lining of the uterus that thickens monthly in preparation for implantation of the blastocyst
Female Reproductive System: Vagina
the birth canal; during labor and delivery the baby passes through the cervix and into the vagina
Phase of Menstrual Cycle: Follicular Phase - 1
Several follicles in the ovaries grow and secrete increasing amounts of estrogen in response to follicle-stimulating hormone (FSH) from the anterior pituitary
Phase of Menstrual Cycle: Ovulation - 2
The secondary oocyte ruptures out of the ovaries in response to luteinizing hormone.
Phase of Menstrual Cycle: Luteal Phase - 3
The corpus luteum forms in response to luteinizing hormone. It is the follicle left behind after ovulation and secretes estrogen and progesterone which thicken the endometrium of the uterus.
Phase of Menstrual Cycle: Menstruation - 4
The monthly shedding of the lining of the uterus when implantation of an embryo does not occur.
Positive Feedback in the Menstrual Cycle
During the follicular phase, estrogen released from the follicle stimulates the release of LH from the anterior pituitary. The increase in LH stimulates the follicle to release even more estrogen. The hormone levels continue to increase until the follicle matures and ovulation occurs.
Negative Feedback in the Menstrual Cycle
During the luteal phase, LH stimulates the corpus luteum to secrete estrogen ad progesterone. Once the levels of estrogen and progesterone are sufficiently high they trigger the hypothalamus and pituitary to shut off, thereby inhibiting the secretion of LH and FSH.
Spermatogenesis
Process of sperm production that starts and puberty
Spermatogenesis Process
Luteinizing Hormone (LH) induces the interstitial cells of the testes to produce testosterone. Together with FSH, testosterone induces maturation of the seminiferous tubules and stimulates the beginning of sperm production. In the seminiferous tubules, each spermatogonium cell (2n) divides by mitosis to produce two primary spermatocytes (2n) which each can undergo meiosis I to produce 2 secondary spermatocytes (n). Each of those undergo meiosis II which yields 4 spermatids (n). These spermatids differentiate and move to the epididymis where they become motile.
Oogenesis
The production of ova begins prior to brith.
Oogenesis Process
Within the embryo, an oogonium cell (2n) undergoes mitosis to produce primary oocytes (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 the stops again and does not continues until fertilization when a sperm penetrates the secondary oocyte.
Oogenesis vs. Spermatogenesis
- It is a 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 polar bodies which will disintegrate.
- One primary oogonium cell produces one active egg cell.
Acrosome Reaction
The head of the sperm, the 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 of the egg. This recognition ensures that the egg will be fertilized by only sperm from the same species. One a sperm binds, the membrane is dramatically depolarized no other sperm can penetrate the egg.
Parthenogenesis
The development of an unfertilized egg. Electrical stimulation or injection with calcium can case the acrosome reaction and parthenogenesis to occur. Drone honeybees develop by natural parthenogenesis.
Stages of Embryonic Development
Cleavage, Gastrulation, and Organogenesis
Embryonic Development and Yolk
Animal eggs and sea urchin eggs are similar because they share almost no yolk. Frog eggs have more yolk this causes cleavage to be unequal with little cell division in the yolky region. Bird eggs with a lot of yolk cause cleavage to be limited to a small, non-yolky disc at the top of the egg.
Cleavage
The rapid mitotic cell division of the zygote that occurs immediately after fertilization. Cleavage produces a fluid-filled ball of cells called a blastula. The fluid filled center is called the blastocoel.
Cleavage: Prostomes
cleavage is spiral and determinant which means the future of the cells have been determined by the four-ball stage; if one cell is separated it will not develop into a complete embryo
Cleavage: Deuterostomes
cleavage is radial and indeterminate which means that each cell retains the capacity to develop into a complete and normal embryo
Gastrulation
The process that involves rearrangement of the blastula and begins with the formation of the blastopore (opening into blastula). Some of the cells on the surface of the embryo migrate into the blastopore to form a new cavity called the archenteron primtive gut. As a result a three-layered embryo called a gastrula is formed.
Embryonic Germ Layers
Ectoderm which becomes the skin and nervous system. Endoderm which will for the viscera including the lungs, liver and digestive organs. Mesoderm which will give rise to the muscle, blood and bones. Some animals develop the mesoglea instead of the mesoderm.
Organogenesis
Organ building; It is the process by which cells continue to differentiate, producing organs from the three embryonic germ layers. Three kinds of morphogenetic changes - folds, splits and dense clustering (condensation) - are the first evidence of organ building.
Frog: Fertilization
The vegetal pole, the yolk portion of the egg, is only one third of the egg. The top half os the egg is called the animal ole and has a pigmented cap. Eggs are laid directly into water and fertilization is external. When the sperm penetrates the egg, the pigmented cap rotates toward the point of penetration and a gray crescent appears on the side opposite the point of entry of the sperm. The gray crescent is critical.
Frog: Cleavage and Gastrulation
The blastopore forms at the border of the gray crescent and the vegetal pole. Cells at the dorsal lip above the blastopore begin to stream over the dorsal lop and into the blastopore (called involution). As the ectoderm cells stream inward with the epibolic movement, the blastocoel disappears and is replaced by another cavity called the archenteron. This region of the mesoderm lining the archenteron tat formed opposite the blastopore is called the dorsal mesoderm.
Frog: Organogensis
In chordates, the organs to form first are the notochord the skeletal rod characteristics of all chordate embryos and the neural tube, which will become the CNS. The neural tube dorms from the dorsal ectoderm above the notochord. Both form by embryonic induction. After the blueprints of the organs are laid down, the embryo develops into a larval stage, the tadpole. Later, metamorphosis will transform the tadpole into the frog.
Bird: Cleavage and Gastrulation
A bird’s egg has so much yolk that development of the embryo occurs in a blastodisc (flat disk) 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 forms the archenteron. As cleavage and gastrulation occur the yolk gets smaller.
Bird: Extraembryonic Membrane
Tissues outside the membrane form this. The four membranes are the yolk sac, amnion, chorion, and allantois. The yolk sac encloses the yolk and is food for the growing embryo. The amnion encloses the embryo in protective amniotic fluid. The chorion lies under the shell and allows for the diffusion of respiratory gases between the outside and the growing embryo. The allantois is analogous to the placenta in mammals it is a conduit for respiratory gases between the environment and the embryo. Is is also a repository for uric acid and nitrogenous waste.
Cytoplastmic Determinants
If an eight ball sea urchin embryo is cut longitudinally development is normal. however, if it is cut horizontally the embryo is abnormal.
The Gray Crescent
Hans Spemann demonstrated the importance of the cytoplasm associated with the gray crescent. Removal of the gray crescent caused an abnormal cells to form.
Embryonic Induction
The ability of one group of embryonic cells to influence the development of another group of embryonic cells. The dorsal lip of he blastopore initiates a chain of inductions that results in the formation of the neural tube.
Hox Genes (Homeobox)
Control the expression of genes that regulate the placement of specific anatomical structures, They pray a critical role in normal embryonic development.
