BIO CH49

asexual reproduction (clonal)

single individual creates offspring, genetically identical, preserves genetic uniformity, no energy expended for finding a mate/producing gametes

mitosis mechanisms

fission, budding, fragmentation

mitosis: fission

parent separates into 2 or more offspsring (approx equal size)

mitosis: budding

new individual develops while attached to parent, may break free or remain attached

mitosis: fragmentation

pieces separate from the parent’s body and develop/regenerate new individuals (like worms)

parthenogenesis (asexual)

producing offspring by development of egg without fertilization, meiosis in female, offspring are not genetically identical, diploid or haploid

sexual reproduction

male and female, fusion of gametes (sperm/egg), generated by meiosis, genetic diversity, good for changing environments, spending energy finding mates/producing gametes

2 meiosis mechanisms for genetic diversity

genetic recombination and independent assortment of chromosomes (+ random DNA mutations)

mating

pairing of male and female for sexual reproduction

gametogenesis

formation of male/female gametes

fertilization

union of gametes, fusion of haploid sperm and egg produces diploid zygote (first cell of new individual)

gametogenesis

germ cells, located in gonads, mitotic division of germ cells produce spermatogonia and oogonia (they enter meiosis to create gametes)

spermatogenesis

produces 4 mature haploid spermatozoa (motile cells driven through watery medium via flagellum)

acrosome

specialized secretory vesicle containing enzymes/proteins to help sperm penetrate egg

oogenesis

produces one mature, haploid ovum (egg), egg cell divides unevenly on purpose, leftover = polar bodies

when do oocytes advance to metaphase of second meiotic division?

ovulation

When do oocytes complete meiosis?

fertilization

3 egg features

stored nutrients, egg coats (protect egg and embryo), mechanisms (prevent egg from being fertilized by more than 1 sperm cell)

external fertilization

aquatic invertebrates, bony fishes, and amphibians, synchronized release of large quantities of sperm and egg into surrounding water

internal fertilization

mammals, reptiles, birds; sperm released close to or inside female’s reproductive tract entrance, provides aquatic medium required for fertilization inside female’s body

copulation

introduction of male’s sex organ into female’s sex organ for internal fertilization

species recognition

sperm touches outer surface of egg, receptor proteins in sperm plasma membrane bind sperm to vitelline coat or zona pellucida, only same species sperm can recognize and bind

acrosomal reaction

triggered by sperm attaching to egg, enzymes released from sperm to eat through egg coats ultimately fusing with egg’s plasma membrane → completes meiosis in egg to begin development

fast block to polyspermy

invertebrates, few seconds after fertilization, fusion of gametes → opens ion channels → depolarizes egg surface (cannot fuse with additional sperm)

slow block to polyspermy

within minutes after fertilization, mammals, fusion triggers calcium ion release from egg’s ER into cytosol → activates proteins/enzymes to initiate metabolic activity → calcium ions trigger cortical reaction (cortical granules release contents) → enzymes released alter egg coats so no further sperm can penetrate

CONTINUE FROM FUSION OF NUCLEI