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

ADVANTAGES DISADVANTAGES

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.

SPERM OVUM

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

ADVANTAGES DISADVANTAGES

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 asac–like pouch called the amniotic sac and is nourished by the placenta.