250 



ASEXUAL REPRODUCTION 



Photomicrograph of a hydra. 

 Note the buds still attached to 

 the original animal. 



Budding is not as common a form of reproduction as binary 

 fission. Budding and binary fission are types of reproduction 



found only among the simplest of plants 

 and animals. 



Reproduction by means of spore forma- 

 tion. A third type of reproduction found 

 among simple organisms is spore forma- 

 fioti. If yeast cells are subjected to an 

 unfavorable condition of heat, food, or 

 water, they sometimes go through another 

 type of reproduction. Each yeast cell will 

 develop an unusually thick wall. The 

 nucleus and cytoplasm break up into three 

 to eight parts. Very often only four parts are formed. Each of 

 these parts is known as a spore. The spores will remain in the 

 spore case, the thickened cell wall, until the surrounding condi- 

 tions become favorable for them to live alone. Then the spore 

 case will absorb water, burst, and the four yeast cells will come 

 out. Each will feed, grow, and reproduce. This type of propa- 

 gation accomplishes protection as well as reproduction. 



Due to lack of chlorophyll, yeast cells are unable to make their 

 own food. They depend upon food already made. Their food 

 consists of fruit juices and other sugar solutions. If molasses 

 solution, preserved fruit, grape juice, or any 

 other sweet food is left exposed to the air, wild 

 yeast plants, in the form of spores, will settle 

 on the surface and multiplv rapidlv. The Yeast ceiis often form 



. '' a group of four spores. 



yeast cells give off enzymes wdiich attack the These last over an unfa- 



. , . . , . Ill 1 vorable period and at the 



sugar, breaking it down into alcohol and car- proper time break from 



1 T .1 rr^i . p j^ j^j^ 1 • the spore case. Each 



Don dioxide. I his process Ot yeast attacking spore becomes a yeast 



sugar and converting it into alcohol and carbon ^ *°*" 



dioxide is known as fermentation. Bubbles of carbon dioxide 



may be observed in fermented solutions. The test performed in 



