This was a tactic I observed in one of my field placements where the teacher would devote a few moments to show the kids either a motivational meme or video to get the kids excited for the week. It also works as a good transition from weekend mode to classroom mode without being too harsh in the transition. The students can also get involved the previous week by suggesting possible motivation prompts for the next Monday. Another good example of motivational Monday is the kid president videos: https://www.youtube.com/watch?v=RwlhUcSGqgs
This series of videos is a youtube channel that showcase two cartoon sisters who happen to be amoebas. These sisters provide videos that can help explain concepts in science including mitosis, meiosis, and photosynthesis. This acts as a good engage because it can begin to help introduce a new concept or review a learned concept while being interesting and entertaining. These videos can also be used elsewhere in the learning cycle, but as an ENGAGE it gets kids thinking about the subject for the day. Here is the link to their mitosis video on youtube: https://www.youtube.com/watch?v=gwcwSZIfKlM
This is a short video that talks about meiosis, but in square dance form! this video is in a very old cartoon style and can seem to be repetitive at times but even if it is only used for the comedic quality, it will be well used in the classroom. Maybe later on in the lesson you could have the students actually do the meiosis square dance to help reinforce the learning that is taking place. https://www.youtube.com/watch?v=iCL6d0OwKt8
Flickclips.com is a website that provides small clips from a huge list of movies that showcase science in some way. The automatic ones that come to mind may be Finding Nemo for ocean science of Osmosis Jones for anatomy or biology. However, many "typical" movies that seem to not involve science at all can have a few moments of science in them which can really help in the classroom. For example, Iron Man can be used to show the scientific method. It involves a format that is easily relateable to students in the classroom and topics in science that may be more difficult to understand. Link to the site: http://www.flickclip.com/
Using demo's in the classroom is a good way to showcase real life examples of what the students are learning in the classroom. A demo is something you can use in your class within the first few minutes and the effect can be long lasting, especially in the minds of the students. Some examples of demo's include the edible candle (using a cheese stick, a slivered almond, and a flame), surface tension boat (using a paper boat, water, and soap), and even capillary action toothpicks (using water and toothpicks). The idea of demo a day was provided by Flinn Scientific and they have a whole set of books about different demos you can do every day for a year with your class for different science disciplines. https://www.flinnsci.com/teacher-resources/emails/video-landing-pages/a-demo-a-day%E2%84%A2-books/