Horses and donkeys can mate, but they produce a mule, which is always a sterile animal. this means that they cannot produce viable offspring and are .

1. this system transports blood through the body and heart. 2. this system relates to the process by which an organism gets rid of its waste. 3.this system is responsible for movement of bones and fluids throughout the body. 4. this system receives and transmits information and responses. it depends upon electrical impulses created by the movement of charged particles. 5. this system relates to the process by which an organism replicates. sexually reproduction usually involves male cells (sperm) meeting female cells (eggs) to produce a fertilized egg or zygote. 6. this system gets oxygen to the cells of the body and rids the body of waste gases. some organisms use their skin. this is also a cell-level process. 7. this system relates to the structure and support of an organism. it is made of salts and proteins and found in vertebrate animals. 8. this is the system of organs which circulate blood around the body of most animals. 9. this system controls the glands that secrete hormones. 10. this organ system to protect the body from damage. itembank : system circulatory digestive system endocrine system excretory integumentary system muscular system nervous system reproductive system respiratory system skeletal system cardiovascular system