Rats are commonly used as model organisms in laboratory research for several reasons:

1. Genetic Similarity to Humans: Rats share a significant amount of genetic similarity with humans, making them valuable for studying human diseases, genetics, and physiology. This genetic resemblance helps in understanding how certain genes function and contribute to various conditions.

2. Size and Manageability: Rats are relatively small and easy to handle, which makes them practical for laboratory settings. Their size allows researchers to house and care for them efficiently, while still being large enough to perform complex surgical and experimental procedures.

3. Reproductive Rate: Rats have a high reproductive rate and relatively short gestation periods, enabling researchers to study multiple generations in a relatively short period. This is particularly useful for genetic studies and observing the effects of long-term treatments.

4. Well-Established Research Background: Rats have been used in scientific research for many decades, leading to a vast amount of existing data and well-established protocols. This historical context allows for more consistent and comparable results across studies.

5. Behavioral and Cognitive Studies: Rats exhibit complex behaviours and cognitive abilities, making them suitable for research in neuroscience, psychology, and behavioural sciences. They can be trained to perform various tasks, which helps in studying learning, memory, and other cognitive functions.

6. Physiological and Pharmacological Research: Rats are often used to study physiology and the effects of drugs due to their physiological similarities to humans. They are valuable for testing the efficacy and safety of new medications and understanding disease mechanisms.

7. Ethical Considerations: Using rats as model organisms raises fewer ethical concerns compared to higher-order animals like primates. This makes it more feasible to conduct a wide range of experiments that might not be possible with other animals.

In summary, rats are used in laboratory research due to their genetic similarity to humans, practical size, rapid reproduction, extensive research background, suitability for behavioral studies, and ethical considerations. These factors collectively make them an invaluable resource for advancing scientific knowledge.