250 



ASEXUAL REPRODUCTION 



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- 

 tion. 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 



Photomicrograph of a hydra. , , ^1*111 mi 



Note the buds still attached to develop an unusually thick wall. I he 

 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 multiply rapidly. The Yeast cells often form 



a group of four spores. 



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



. . 111 i vorable period and at the 



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



, i< i rrn P , . the spore case. Each 



bon dioxide. This process of yeast attacking sp ore 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 



