Ko'p hujayrali hayvonlarni kelib chiqish nazariyasi Introduction to Ko'p hujayrali hayvonlarni kelib chiqish nazariyasi

B. White-tailed deer

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Another animal that has seen significant changes in its behavior as a result of human activity in recent 
decades is the White-tailed deer. Once forced to inhabit the dense forests of the eastern US and Canada, 
these adaptable creatures have proven themselves capable of living in a wide variety of environments, 
including suburbs and even city parks. Unfortunately, this flexibility has come at a cost. Deer populations 
have exploded in some areas, causing problems such as overgrazing, car accidents, and the spread of 
Lyme disease. In response, hunters have been encouraged to kill more deer, while various forms of birth 
control and sterilization have been trialed as potential solutions. These efforts are still ongoing, and it 
remains to be seen whether they will be successful in bringing deer populations under control.
C. Zebra mussels
One of the most concerning invasive species in recent years is the zebra mussel (Dreissena polymorpha). 
Originally native to the freshwater lakes and rivers of Southern Russia, zebra mussels have been acci-
dentally introduced to the Great Lakes region of North America and have since spread to other bodies of 
water across the continent. These small, fingernail-sized mollusks feed by filtering microscopic particles 
from the water, but in doing so, they also consume the plankton that many aquatic species rely on for 
food. Zebra mussels reproduce quickly and can form dense clusters that clog water intake pipes, damage 
boat hulls and motors, and outcompete native species for resources. Additionally, they are able to survive 
in a wide range of temperatures and water conditions, making them difficult to control once established. 
The economic and ecological impacts of zebra mussels have been significant, with estimates of over $1 
billion in damage and control costs in the United States alone.
In conclusion, the theory of the emergence of complex multicellular organisms from single-celled 
organisms has been a topic of longstanding debate among evolutionary biologists. The gradual process 
of evolution through natural selection has been proposed as the main explanation for this transition, with 
various intermediary stages postulated. However, recent research in molecular biology has shed new light 
on the genetic mechanisms that have driven this process. Regulatory genes that control the expression of 
other genes have been shown to play a crucial role in the development of multicellularity. In particular, 
genes that enable cells to recognize and stick to one another have been found to be key players in the 
formation of multicellular organisms. Future research in this field will undoubtedly shed even more light 
on the complex processes that have shaped the evolution of life on Earth.