Animal models are non-human organisms used in research to study biological processes, disease mechanisms, and potential treatments in a controlled experimental setting. These models provide valuable insights into human biology and disease, as many physiological processes and genetic features are conserved across different species. Researchers often use animal models to investigate the safety, efficacy, and side effects of new drugs and therapies before proceeding to clinical trials in humans.

Some common animal models used in research include:

1. Mice: Mice are the most widely used animal model due to their small size, short lifespan, ease of breeding, and low cost. They share approximately 85% of their protein-coding genes with humans, making them a valuable model for studying human genetics, diseases, and drug development.
2. Rats: Rats are larger than mice and have a more complex nervous system, making them particularly useful for studying neurobiology, behavior, and cognition. They are also commonly used in toxicology and pharmacology studies.
3. Zebrafish: Zebrafish are small, transparent, and easy to breed, making them a popular model for developmental biology, genetics, and drug discovery. They have a high degree of genetic and physiological similarity to humans, with approximately 70% of human genes having a zebrafish ortholog.
4. Fruit flies (Drosophila melanogaster): Fruit flies have a short life cycle, are easy to maintain in the laboratory, and have a well-characterized genome. They are widely used in genetics research and are particularly useful for studying developmental processes, gene function, and signaling pathways.
5. Caenorhabditis elegans (C. elegans): This small, transparent roundworm has a simple nervous system and a fully sequenced genome, making it an excellent model for studying gene function, development, and aging.
6. Chickens (Gallus gallus): Chick embryos are a valuable model for studying embryonic development, tissue regeneration, and immune responses. They are also used in vaccine development and research on avian diseases.
7. Non-human primates: Non-human primates, such as rhesus macaques and marmosets, are used in research due to their close genetic and physiological similarity to humans. They are particularly valuable for studying complex cognitive processes, social behaviors, and neurodegenerative diseases. However, the use of non-human primates in research is subject to strict ethical guidelines and regulations due to concerns about animal welfare.

While animal models have contributed significantly to our understanding of human biology and disease, they have limitations. Not all aspects of human physiology and disease can be accurately replicated in animal models, and findings from animal studies may not always translate directly to humans. Nevertheless, animal models remain a critical tool in biomedical research, enabling scientists to explore complex biological processes and develop new treatments in a controlled experimental setting.