Accelerated Biology According to another theory of reproduction

 The growth of a new individual without the fusion of gametes.  Involves only one parent.  Offspring genetically identical to parent (clones).

 Binary fission – The splitting of one cell into two (bacteria)  Budding – A new individual begins as outgrowths on parent (yeast)  Spores – Asexual reproductive cells that can develop directly into a complete organism.

 Bacteria undergo binary fission

 All the organisms below use budding as a mode of reproduction  Prickly pear cacti (below)  Hydra (right)  Yeast (below right)

 Ferns can reproduce by means of spores

ADVANTAGESDISADVANTAGES  Simple and efficient!  Does not "cost" the parent a great amount of energy or time  No need to look for and court a mate  Lack of genetic variation  All of the organisms are genetically identical and therefore share the same weaknesses. If the environment changes, the consequences could be deadly to ALL of the individuals.

 Involves the fusion of gametes.  Involves two parents.  Offspring genetically different from parents.

 Gamete – Specialized reproductive cells necessary for sexual reproduction. They contain half the genetic information.  Sperm – Male gamete  Ovum (plural: ova) – Female gamete (mature egg)  Fertilization – Fusion of nuclei from two gametes.

SPERMOVUM  Motile – propelled by flagellum  Much smaller than egg  Males begin to produce sperm during puberty  Males release millions of sperm at one time  Consist of a head, midpiece, and a tail  Nonmotile – smooth muscle contractions of the fallopian tube move ovum towards the uterus  Much larger than sperm; can be seen by the unaided eye  Females are born with all the eggs they will ever have ~ 2 million  Females usually release one egg a month

 Zygote – Cell resulting from the fusion of male and female gametes at fertilization.  Gestation – The length of time between fertilization and birth.  Elephant – 22 months!  Human – 9 ½ months  Mouse – ~ 21 days

ADVANTAGESDISADVANTAGES  Genetic variation!  Lots of time and energy spent looking for and courting a mate  Some males pay “the ultimate price” and die to ensure that their genes are passed on.

There are three different patterns in which sexual reproduction can occur.  External fertilization and external development  Most amphibians (salamanders, frogs, toads)  Cnidaria (coral, jellyfish, sea anemones)  Internal fertilization and external development  Most reptiles, birds, monotremes (egg-laying mammals)  Internal fertilization and internal development  Sharks, some snakes, placental mammals

 A female frog lays her eggs and then the male fertilizes them.

 Reptiles and birds lay eggs  Crocodile, python, and bluebird hatching

 Monotreme – mammals that lay eggs  There are only two examples  Duck billed platypus  Echidna (spiny ant eater)

 Marsupial – Mammals that give birth at a very early age of development  Marsupium – Latin for pouch or purse  A joey suckles inside the mother’s pouch for six months

 The only marsupial native to the U.S. is the opossum

 Placental Mammals – The embryo/fetus develops inside a sac–like pouch called the amniotic sac and is nourished by the placenta.