Go to the first list slide Animals and click anywhere in the text/list box (but do not have any text highlighted!) ...
Add any green animation and you should see numbers 1-4 beside the bullets.
In the Animation Pane, click on the grey bar to expand the list.
If you don't see little mouse icons beside each animation, right-click on any of them and Hide Advanced Timeline
Click on one of the photos, then hold SHIFT and click on the other photos so they are all selected.
Add any green animation.
You will see a "5" beside each photo.
The Animation Pane should look like this...
With your picture animations still highlighted, go to the Start option on the toolbar and use the drop-down menu there to change it to With Previous.
When you've done this, no Picture animations have a mouse icon beside them.
If you clicked off and your picture animations are not highlighted anymore, just use the drop-down menu for the first picture to change the Start to With Previous.
Repeat the same steps on the other list slides:
Keep your Animation Pane open and get your work checked so far.