Animal Reproduction and Development

Question 1

Advantages of Asexual Reproduction

Answer 1

• 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.

Question 2

Fission

Answer 2

Separation of an organism into two new cells (amoeba).

Question 3

Budding

Answer 3

The splitting off of new individuals from existing ones (hydra).

Question 4

Fragmentation & Regeneration

Answer 4

A single parent breaks into part that regenerate into new individuals (sponges, planaria, starfish)

Question 5

Parthenogensis

Answer 5

The development of an egg without fertilization. The resulting adult is haploid (honeybees, some lizards).

Question 6

Advantages of Sexual Reproduction

Answer 6

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

Question 7

Male Reproductive System: Testes

Answer 7

male gonad where sperm are produced

Question 8

Male Reproductive System: Seminiferous Tubules

Answer 8

the site of sperm formation in the testes

Question 9

Male Reproductive System: Vas Deferens

Answer 9

the muscular duct that carries sperm during ejaculation from the epididymic to the urethra in the penis

Question 10

Male Reproductive System: Seminal Vesicles

Answer 10

secrete mucus, fructose sugar (energy for the sperm), and the hormone prostaglandin

Question 11

Male Reproductive System: Prostaglandin

Answer 11

stimulates uterine contractions during ejaculation

Question 12

Male Reproductive System: Prostate Fland

Answer 12

the large gland that secretes semen directly into the urethra

Question 13

Male Reproductive System: Scrotum

Answer 13

the sac outside the abdominal cavity that holds the testes; the cooler temperature enables the sperm to survive

Question 14

Male Reproductive System: Urethra

Answer 14

tube that carries semen and urine

Question 15

Female Reproductive System: Ovaries

Answer 15

where meiosis occurs and where the secondary oocyte forms prior to birth

Question 16

Female Reproductive System: Oviducts & Fallopian Tubes

Answer 16

where fertilization occurs; after ovulation the egg moves through the oviduct to the uterus

Question 17

Female Reproductive System: Uterus

Answer 17

where the blastocyst will implant and where the embryo will develop during the nine-month gestation if fertilization occurs

Question 18

Female Reproductive System: Endometrium

Answer 18

the lining of the uterus that thickens monthly in preparation for implantation of the blastocyst

Question 19

Female Reproductive System: Vagina

Answer 19

the birth canal; during labor and delivery the baby passes through the cervix and into the vagina

Question 20

Phase of Menstrual Cycle: Follicular Phase - 1

Answer 20

Several follicles in the ovaries grow and secrete increasing amounts of estrogen in response to follicle-stimulating hormone (FSH) from the anterior pituitary

Question 21

Phase of Menstrual Cycle: Ovulation - 2

Answer 21

The secondary oocyte ruptures out of the ovaries in response to luteinizing hormone.

Question 22

Phase of Menstrual Cycle: Luteal Phase - 3

Answer 22

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.

Question 23

Phase of Menstrual Cycle: Menstruation - 4

Answer 23

The monthly shedding of the lining of the uterus when implantation of an embryo does not occur.

Question 24

Positive Feedback in the Menstrual Cycle

Answer 24

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.

Question 25

Negative Feedback in the Menstrual Cycle

Answer 25

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.

Question 26

Spermatogenesis

Answer 26

Process of sperm production that starts and puberty

Question 27

Spermatogenesis Process

Answer 27

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.

Question 28

Oogenesis

Answer 28

The production of ova begins prior to brith.

Question 29

Oogenesis Process

Answer 29

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.

Question 30

Oogenesis vs. Spermatogenesis

Answer 30

1. It is a Stop-Start process. It begins prior to birth and is completed after fertilization.
2. Cytokinesis divides the cytoplasm of the cell unequally, producing one large cell and two small polar bodies which will disintegrate.
3. One primary oogonium cell produces one active egg cell.

Question 31

Acrosome Reaction

Answer 31

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.

Question 32

Parthenogenesis

Answer 32

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.

Question 33

Stages of Embryonic Development

Answer 33

Cleavage, Gastrulation, and Organogenesis

Question 34

Embryonic Development and Yolk

Answer 34

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.

Question 35

Cleavage

Answer 35

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.

Question 36

Cleavage: Prostomes

Answer 36

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

Question 37

Cleavage: Deuterostomes

Answer 37

cleavage is radial and indeterminate which means that each cell retains the capacity to develop into a complete and normal embryo

Question 38

Gastrulation

Answer 38

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.

Question 39

Embryonic Germ Layers

Answer 39

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.

Question 40

Organogenesis

Answer 40

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.

Question 41

Frog: Fertilization

Answer 41

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.

Question 42

Frog: Cleavage and Gastrulation

Answer 42

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.

Question 43

Frog: Organogensis

Answer 43

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.

Question 44

Bird: Cleavage and Gastrulation

Answer 44

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.

Question 45

Bird: Extraembryonic Membrane

Answer 45

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.

Question 46

Cytoplastmic Determinants

Answer 46

If an eight ball sea urchin embryo is cut longitudinally development is normal. however, if it is cut horizontally the embryo is abnormal.

Question 47

The Gray Crescent

Answer 47

Hans Spemann demonstrated the importance of the cytoplasm associated with the gray crescent. Removal of the gray crescent caused an abnormal cells to form.

Question 48

Embryonic Induction

Answer 48

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.

Question 49

Hox Genes (Homeobox)

Answer 49

Control the expression of genes that regulate the placement of specific anatomical structures, They pray a critical role in normal embryonic development.