Types of reproduction

Sexual Requires two mates of opposite genders (male produces moving sex cell—sperm; female produces non-moving sex cell—egg) Offspring are genetically different from parents and other offspring Greater diversity increases the chance of survival for the group However, there are usually fewer offspring and the cost of reproduction is higher for the female as she must create egg and/or provide for the offspring

Sexual (cont.) Fertilization (the coming together of the egg and sperm) results in a zygote which develops into the offspring External fertilization occurs outside the body of the female (frogs) Internal fertilization occurs inside the body of the female (humans and many plants) May involve pollinators such as birds and bees, wind or water May involve intercourse when sperm is deposited inside the body of the female Usually uses meiosis to create sex cells which have ½ the total chromosome number

Asexual Does not require a mate (and therefore occurs more quickly and without the mating rituals) Offspring are genetically identical to parent Can generate large numbers of offspring in very little time Isolation does not pose a problem to reproduction However, changes in the environment may devastate the population There are many forms

Binary Fission Used by very simple organisms DNA is copied and cell splits In eukaryotic cells this is basically mitosis to generate more organisms

Fragmentation (aka Vegetative Propogation) Runners that lead to plantlet get broken “accidentally” and plantlet becomes a separate organism Does NOT require regrowth Best know in plants such as crab grass and strawberries

Regeneration Like fragmentation, original “accidentally” break off However, BOTH parts must REGROW a portion to be whole again Seen in starfish, planaria, many fungi

Budding Intentionally grows a small version from the side and allows to fall off Seen in yeast, sponges and cnidaria

Spore formation Similar to budding but the bud is surrounded by a protective coat and only develops during non-ideal conditions Spore is protected until desired conditions return Often seen in ferns and fungi

Cloning Generally used to describe a scientific procedure in which DNA from non sex cell is inserted into a sex cell which has had DNA removed intentionally Does not occur in nature

Parthenogenesis An unfertilized egg develops into an organism with ½ the normal DNA Known to occur in frogs and snakes Usually happens in a single sex environment