Why pure insert operation in master result in update and read operation in slave?

I use multi threads to do pure insert operation in master(mysql 5.7),then I use orzdba to observer the mysql status as following picture:

but when I observe in slave(mysql 5.7) ,I found though the salve do also the pure insert operation,but the innodb rows influenced not only contains insert but also update and read operation,the orzdba's observation is as following(slave is single thread so TPS is slower than master):

My question is why pure insert has update and read operation in slave?