Asexual vs. Sexual Reproduction Standard 9: Compare sexual re- production (offspring inherit half of their genes from each parent) with asexual reproduction (offspring is an identical copy of the parent’s cell).

Sexual Reproduction Asexual Reproduction Definition Involves sex cells and fertilization DNA from 2 parents Does not involve sex cells and fertilization Only one parent genetically Advantages/ Disadvantages Offspring are not genetically identical to one another There is variation in the offspring Offspring have no variation Offspring are genetically identical to one another

Asexual reproduction in Plants Vegetative Propagation – New plants develop from the roots, stems, or leaves of the parent plant. Examples: -tubers -bulbs -runners

Tubers Tubers are thickened under- ground stems created so plants can survive winter or dry times Examples: potato, artichoke, yam, dahlia, water chestnut, arrowroot

Tubers Food made by the new plant is sent to make new tubers, thereby reproducing itself. Tubers can be separated (see separated dahlia tubers in picture) and planted individually

Bulbs Examples: daffodils, lilies, tulips Similar to tubers- can be separated

Runners Runners are side shoots which grow out from the parent plant. Buds form at points along the runner and eventually these buds form roots and grow into new plants. Examples: spider plant (Anthericum), strawberry ( Fragaria x ananassa)

Artificial (man-made) Propagation in Plants 2 methods used to cultivate plants asexually -taking cuttings -grafting

Cuttings They can be placed in moist soil or water (and sometimes dipped in rooting powder). Cuttings are small pieces of stem with some leaves attached, the new plant grows from this.

Grafting A cut stem of one plant (with good flower or fruit growth) (the graft) is taken and firmly attached to the rootstock of another plant (which has a strong, established root system) (the stock). Examples- roses, fruit trees

Artificial Propagation benefits Artificial propagation has allowed us to adapt and improve plants for our own use. Some of the benefits include: Quick production of large numbers of genetically identical plants. Specific varieties, desired features or consistent quality can be produced especially in fruit, flowers.

Asexual Reproduction in Animals/Fungi Parthenogenesis Regeneration Budding

Parthenogenesis Parthenogenesis is development of an egg into an embryo without fertilization About 1% of animal species reproduce by parthenogenesis an even smaller fraction switch between sexual and asexual reproduction

Parthenogenesis occurs most often in low- level species including some fish, amphibians and reptiles

Why parthenogenesis? Many species reproduce by partheno- genesis in the absence of a wide pool of potential mates (as alleged in the movies "Jurassic Park") Some species switch to sexual reproduction only in adverse conditions for increasing the chance of survival.

WHY??? Why would these organisms prefer asexual reproduction in stable conditions and sexual reproduction in more uncertain or less favorable conditions? Hint- think about genetic diversity

Regeneration * This refers to the ability of some animals to re-grow severed parts.  Some of these animals can also grow whole new organisms from the severed pieces (some sea stars and flatworms shown to the right )

Why regeneration? These organisms can also reproduce sexually They can use regeneration to escape a predator or attack

Budding the parent cell or body gives out a lateral outgrowth called the bud. The bud then falls off and germinates into a new individual. Budding results in the formation of daughter cells of unequal sizes that later grow to adult size.

Budding hydra yeast

Asexual Reproduction in Bacteria & Protists Binary Fission Copying DNA then splitting into 2 equal-sized cells Bacteria Unicellular protists: amoebas, paramecia, etc.

Sexual Reproduction DNA comes from 2 sources Gametes: sex cells: egg and sperm More genetic diversity- helpful