Some options that come to mind:

1. Increase the amount of funding available for biologists working on projects within EA-aligned areas (neglected tropical diseases, pandemic prevention, longevity, etc.)

2. Create a professional network for biologists working on said projects and hold events

3. Invite biologists who receive Open Phil or other EA grants to attend EA Global (with free tickets/travel)

4. Something anyone reading this might be able to do: Find biologists working on cool things and make them feel appreciated. Try to understand their work, share their work enthusiastically (to the extent that you understand it), tell them they're making a difference, and recommend they look into any EA funding options which might be relevant for them. (Be selective in this last case; you don't want anyone to waste their time applying for grants that aren't actually a good fit for their projects.)

In general, people either find EA because they like the general mission or because EA contains a lot of work/people relevant to something they liked already. If you're thinking about a particular interest group (like biologists), think about what biologists value, and ways to let them know the EA community has those things.

I'm not sure if this is answering the intent of the question, but one could refer undergrad/grad biologists to the biology part of effective thesis.