Teaching NGSS 1-LS3-1 includes teaching first graders about similarities and differences between adult and baby animals. I covered this by diving into a study of bats and orcas, both mammals.
This orca flip book was an integral part of our study on orcas. This flip book is available on Teachers Pay Teachers here. We read orca facts and wrote about what we learned. We also watched some videos. A link to videos I use are on my school website under the subtitle: Whales. Click here.
We also did a fun lab from Steve Spangler. The students loved this hands on activity.