Biological toxins are harmful substances produced by living organisms, such as bacteria, plants, and animals. These toxins can cause illness or death in humans and other animals when they are ingested, inhaled, or absorbed through the skin. Examples include botulinum toxin from the bacterium Clostridium botulinum and ricin from the castor bean plant. These toxins can disrupt biological processes by interfering with cellular functions or damaging tissues. Some biological toxins are used in medicine, such as botulinum toxin for treating certain medical conditions, while others pose significant risks in nature, requiring careful handling and awareness.