Fortunately, there are several other words suggesting that a depiction is not a precise representation of reality but rather a simplification that serves to emphasize certain facts or relationships, and they don't carry any of cartoon's demeaning connotations: diagram, figure, illustration, schematic. IMHO, these are vastly preferable for referring to depictions of biological phenomenon. This seems to be well supported by definitions, synonyms, and word associations:
Merriam-Webster (online)
diagram
Etymology: Greek diagramma, from diagraphein to mark out by lines, from dia- + graphein to write — more at carve
Date: 1619
1 : a graphic design that explains rather than represents; especially : a drawing that shows arrangement and relations (as of parts)
2 : a line drawing made for mathematical or scientific purposes
2 : a line drawing made for mathematical or scientific purposes
schema
Inflected Form(s): plural sche·ma·ta \-mə-tə\ also schemas
Etymology: Greek schēmat-, schēma
Date: circa 1890
1 : a diagrammatic presentation; broadly : a structured framework or plan : outline
figure
Etymology: Middle English, from Anglo-French, from Latin figura, from fingere
Date: 13th century
2 a : a geometric form (as a line, triangle, or sphere) especially when considered as a set of geometric elements (as points) in space of a given number of dimensions b : bodily shape or form especially of a person c : an object noticeable only as a shape or form 3 a : the graphic representation of a form especially of a person or geometric entity b : a diagram or pictorial illustration of textual matter
illustration
Date: 14th century
2 : something that serves to illustrate: as a : an example or instance that helps make something clear b : a picture or diagram that helps make something clear or attractive
cartoon
Etymology: Italian cartone pasteboard, cartoon, augmentative of carta leaf of paper — more at card
Date: 1671
1 : a preparatory design, drawing, or painting (as for a fresco)
2 a : a drawing intended as satire, caricature, or humor b : comic strip
3 : animated cartoon
4 : a ludicrously simplistic, unrealistic, or one-dimensional portrayal or version;
2 a : a drawing intended as satire, caricature, or humor b : comic strip
3 : animated cartoon
4 : a ludicrously simplistic, unrealistic, or one-dimensional portrayal or version
Thesaurus.com
diagram
Part of Speech: noun
Definition: drawing, sketch of form or plan
Synonyms: big picture, blueprint, chart, description, design, draft, figure, floor plan, game, game plan, ground plan, layout, outline, perspective, representation, rough draft
schema
Part of Speech: noun
Definition: design
Synonyms: architecture, arrangement, blueprint, chart, comp, composition, conception, constitution, construction, delineation, depiction, diagram, doodle, drawing, dummy, form, formation, game plan, idea, layout, makeup, map, method, model, outline, paste-up, pattern, perspective, picture, plan, project, scheme, strategy, study, tracery, tracing, treatment
figure
Part of Speech: noun
Definition: object with design; depiction
Synonyms: cast, composition, decoration, device, diagram, drawing, effigy, embellishment, emblem, illustration, image, model, mold, motif, motive, ornamentation, pattern, piece, portrait, representation, sketch, statue
illustration
Part of Speech: noun
Definition: drawing, artwork that assists explanation
Synonyms: adornment, cartoon, decoration, depiction, design, engraving, etching, figure, frontispiece, halftone, image, line drawing, painting, photo, photograph, picture, plate, sketch, snapshot, tailpiece, vignette
cartoon
Part of Speech: noun
Definition: funny drawing, often with dialogue or caption
Synonyms: animation, caricature, comic strip, drawing, lampoon, parody, representation, satire, sketch, takeoff
www.wordassociation.org
associated to diagram
1. chart weak
2. graph weak
3. draw v. weak
4. plan v. weak
5. block v. weak
associated from diagram
1. chart medium
2. picture medium
3. diaphragm weak
4. drawing v. weak
5. graph v. weak
associated to schema
1. scheme strong
2. axiom weak
3. concept weak
4. fema weak
5. pooh weak
associated from schema
1. scheme strong
2. database weak
3. diagram weak
4. paradigm weak
5. seem weak
associated to figure
1. stick medium
2. action weak
3. father weak
4. shape weak
5. authority v. weak
associated from figure
1. shape medium
2. eight medium
3. skate weak
4. skating v. weak
5. out v. weak
associated to schematic
1. plan strong
2. scheme medium
3. architecture weak
4. blueprint weak
5. diagram weak
associated from schematic
1. blueprint strong
2. system strong
3. design medium
4. drawing medium
5. love medium
associated to illustration
1. example medium
2. drawing medium
3. graphic weak
4. book v. weak
5. capella v. weak
associated from illustration
1. picture strong
2. drawing medium
3. book weak
4. cartoon weak
5. draw weak
associated to cartoon
1. animation v. weak
2. simpsons v. weak
3. anime v. weak
4. disney v. weak
5. character v. weak
associated from cartoon
1. character medium
2. network weak
3. animation weak
4. comic v. weak
5. tv v. weak