chapter 49 ~ reproductive system Flashcards
A single individual gives rise to offspring; there is no genetic input from another individual
Asexual reproduction
Male and female parents produce offspring through fusion of gametes generated by meiosis
Sexual reproduction
What are the three mechanisms involving mitosis?
Fission, budding and fragmentation
The parent separates into two or more offspring of approx equal size
Fission
What organisms undergo fission?
Planarians
A new individual develops while attached to the parent ~ offspring may break free from the parent or remain attached to form a colony
Budding
What organism undergo budding?
Hydra
Pieces separate from the body of a parent and develop (regenerate) into new individuals
Fragmentation
What organisms undergo fragmentation?
Flatworms, annelids, and some echinoderms
Offsprings of asexual reproduction are genetically
Identical to one another and to the parent (genetic clones of parent)
What are some advantages of asexual reproduction?
-preserves genetic uniformity , helpful in stable environments
-no energy expended producing gametes
-no energy expanded in finding a mate
What are the disadvantages of asexual reproduction?
- Low genetic variability
- slows evolution
- difficult to adapt to environment
Animals produce offspring by development of an egg without fertilization
Parthenogenesis
Offspring of parthenogenesis are genetically….
Not genetically identical to the parent or to each other
What are offspring via parthenogenesis not genetically identical?
The egg is produced by meiosis in the female parent
What is the parthenogenesis offspring?
Haploid or diploid - depends on species
What is an example of parthenogenesis offspring?
Haploid male bees (drones) develop from unfertilized eggs produced by reproductive females
What are the advantages of sexual reproduction?
Genetic diversity, increase chance of offspring grow, and reproduce successfully in a changing environment
What are the disadvantages of sexual reproduction?
Expenditure of energy to produce gametes and find mates, finding mates increases exposure to predation and takes time from finding food and shelter and caring For offspring
What two mechanisms of meiosis give vise to genetic diversity?
Genetic recombination and independent assortment
What are other sources of genetic variability?
-Eggs and sperm fusing together randomly
-random DNA mutations (For both sexual and asexual)
Pairing of a male and a female for the purpose of sexual reproduction
Mating
Formation of male and female gametes
Gametogenesis
Formation of sperm in males
Spermatogenesis
Formation of ova or eggs in females
Oogenesis
What is fertilization?
Union of gametes
What does the fusion of a haploid sperm and egg during fertilization produce?
A diploid zygote - the first cell of a new individual
What do gametes form from?
Germ cells
A cell line that is set aside early in embryonic development and distinct from other body cells (somatic cells)
Germ cells
Where are germ cells located?
Gonads (testes and ovaries)
What do mitotic divisions of germ cells produce?
Spermatogonia and Oogonia
What cells enter meiosis to give rise to gametes via gametogenesis?
Spermatogonia and oogonia
What are the basic components of the reproductive system?
Gonads, ducts, accessory glands and organs, perineal structures (external genitalia)
What are the ducts role in the reproductive system?
Receive and transport gametes
What are the accessory glands and organs role in the reproductive system?
Secretes fluids into the ducts of the reproductive system and other excretory ducts
What does spermatogenesis produce?
4 mature haploid spermatozoa (sperm)
What makes sperm cells motile?
Flagellum
What happens during maturation from a spermatid to a sperm?
Most of the cytoplasm is lost except for the mitochondria
What does the mitochondria in a sperm do?
Produce the ATP to drive the flagellum
A specialized secretory vesicle that contains enzymes and other proteins that help the sperm penetrate the egg; forms a cap over the nucleus in the head of the sperm
Acrosome
Where does spermatogenesis begin?
Outermost layer of cells in the seminiferous tubules
What happens at each step of spermatogenesis?
The daughter cells move closer to the lumen
What do seminiferous tubules contain?
-Spermatogonia, spermatocytes at different stages of development
-spermatids, spermatozoa and nurse cells (sertoli cells)
Nurse cells that provide nourishment to developing spermatozoa
Sertoli cells
What are the anatomical parts of a spermatozoan?
Head, neck, middle piece, tail
Flattened elliptical structure, contains nucleus with densely packed chromosomes, acrosome at the tip of the head which contains enzymes essential for fertilization
The head of a spermatozoan
Attaches head to the middle piece
Neck of a spermatozoan
Contain mitochondria that provide ATP required to power its movement
Middle piece of a spermatozoan
Helps in the mobility using a whiplike movement
Tail
Why is a mature sperm small in size and mass?
They lack other organelles
What does oogenesis produce?
One mature, haploid ovum (egg)
A large cell containing most of the cytoplasm of the parent cell
Ovum (egg)
Other products of oogenesis that are nonfunctional cells
Polar bodies
How do polar bodies form?
They form due to unequal cytoplasmic divisions concentrating nutrients and other molecules required for development in the egg
Where are oocytes rested in meiosis until ovulation and puberty?
Prophase 1
Where do oocytes advance to in mitosis at ovulation?
Metaphase 2
When do oocytes complete meiosis?
Fertilization
What are the 3 features of the egg?
Stoned nutrients, egg coats and mechanisms that prevent the egg from being fertilized by more than one sperm
Contains few nutrients, microscopic because embryo compel eyes development in mothers uterus and mothers body provides all the nutrients required for development
Mammal eggs
What is the role of egg coats?
To protect the egg from injury and infection, in some species, protect the embryo after fertilization
Gel like matrix of proteins, glycoproteins, or polysaccharides immediately outside the plasma membrane of the egg cell
Vitelline cell
Zone pellucida
Vitelline coat in mammals
Additional outer protein coats that form a hard, water impermeable layer for preventing desiccation
Egg coats of insect eggs
Have an outer egg jelly layer instead of a tough protein coat
Egg coats in amphibians and some echinoderms
In birds, reptiles and monotremes, the egg white and a surrounding shell
Are added in the oviduct
In mammals, what is the egg surrounded by?
Follicle cells
Cells that grow from ovarian tissue and nourish the developing egg - make up a part of the zone pellucida in ovary and remain as a protective layer after egg released
Follicle cells
How are gametes delivered from the gonads to the site of fertilization?
Ducts, oviducts and sperm ducts
How do eggs (nonmotile) move through oviducts?
The beating of cilia lining the oviducts or by contractions of the oviducts or body wall
What are the two modes of sexual fertilization?
External and internal
Where does external fertilization occur?
In most aquatic invertebrates, bony fishes and amphibians
What happens in external fertilization?
Males and females synchronize the release of large quantities of eggs and sperm into the surrounding water
Sperm swim until they collide with the egg of the same species
Where does internal fertilization take place?
In reptiles, birds, mammals, annelids, and some arthropods, mollusks and fishes
What happens in internal fertilization?
Sperms are released close to or inside the entrance of the female’s reproductive tract
Internal fertilization provides the aquatic medium required for fertilization inside the female’s body
Sperm swim through fluids in reproductive tract until reach and fertilize each egg - some molecules released by egg attract sperm to its outer coat
Reflex response in which the male claps the female tightly around the body with his forelimbs
Amplexus
What does amplexus stimulate?
The female to shed a mass of eggs into the water through the cloaca
The cavity in reptiles, birds, amphibians and many fishes into which the both the intestinal and genital tracts empty
Cloaca
Introduction of the mate’s accessory sex organ into the female’s accessory sex organ to accomplish internal fertilization
Copulation
What binds the sperm to the vitelline coat?
Receptor proteins in the sperm plasma membrane do the binding when a sperm touches the outer surface of the egg
Where is species recognition important?
In animals that carry out external fertilization
What is triggered by the attachment of sperm to egg?
Acrosomal reaction
Enzymes in the acrosome are released from the sperm and digest a path through the egg coats
Acrosomal reaction
When does the sperm stop following/ digesting the path through the egg coat?
Until its plasma membrane tones and fuses with the plasma membrane of the egg
Introduces the sperm nucleus into the egg cytoplasm- activates egg to
Complete meiosis and begin development
Fusion
Fusion of egg and sperm opens ion channels in egg plasma membrane - electrical depolarization over egg surface
Fast block to polyspermy
How does depolarization after the egg plasma membrane potential?
Negative to positive - makes it so it can’t fuse with any additional sperm
Fusion of egg and sperm triggers release of Ca 2+ ions
Slow block to polyspermy
Where are Ions released from in slow block to polyspermy?
Eggs Er into cytosol
Activate control proteins and enzymes that initiate intense metabolic activity
Ca 2+ ions
What reaction do Ca 2 + ions trigger?
Cortical reaction
Cortical granules under the egg’s plasma membrane release their contents by exocytosis
Cortical reaction
What do enzymes released from cortical granules do?
Alter the egg coats so that no further sperm can penetrate to the egg surface
What moves fuses fun sperm and egg nuclei together?
Microtubules
Where do sperm and egg nuclei fuse?
Egg cytoplasm
What initiates events of embryonic development?
When chromosomes of the egg and sperm nuclei assemble together and enter the mitosis
Lay eggs - development outside mother’s body
Oviparous
Embryo retained within mothers uterus - nourished during at least early development
Viviparous
Animals retain fertilized eggs within body, embryo develops in egg (no uterus) and eggs hatch inside mother then released
Ovoviviparous
In which organisms does oviparous reproduction occur?
Insects, spiders, and most reptiles and birds
Mammal exception: monotreme ant eaters and platypus
Oviparous exception
Ovoviviparous examples
Fishes, birds, lizards, amphibians and snakes
Viviparous examples
Mammals
Have a placenta that connects embryo to uterus - facilitates transfer of nutrients from mothers blood to embryo and wastes from embryo to mother
Eutharians/ placental mammals
Provide nutrients to embryo during early development via an attached membranous sac containing yolk
Marsupials
Abdominal pouch in which the embryo born at early stage crawls into to attach to a nipple and continue development
Marsupium
BOTH mature egg and sperm producing tissues are present in the same individual
Hermaphroditism
T/F: most hermaphroditic animals fertilize themselves - explain
F, self fertilization is prevented by anatomical barriers or by producing mature eggs and sperm at different times
Develop functional ovaries and testes at the same time
Simultaneous hermaphrodites
Change from one sex to the other
Sequential hermaphrodites
