Study Saturday: How to Succeed in Organismal Biology

Organismal Biology (often labeled General Biology II) is the course that zooms out from cells and molecules to whole organisms, populations, and ecosystems. Most DPT programs require two semesters of biology with labs, and this second semester covers evolution, ecology, plant biology, animal diversity, and how organ systems integrate at the organism level. It is a different kind of challenge than Biology I, relying more on comparative thinking and less on memorizing molecular pathways.

Why DPT Programs Require This

Physical therapists treat human beings as integrated organisms, not isolated cells. Organismal biology teaches you to think about how biological systems function together: neural control, hormonal regulation, nutrition and transport, homeostasis, and how structure relates to function. This whole-organism perspective directly underpins the clinical reasoning you will use in DPT school and practice.

The course also bridges cellular biology (Biology I) to the advanced anatomy, physiology, and pathology courses in your DPT curriculum. Without understanding how systems integrate at the organism level, the systems-based thinking required in graduate coursework becomes much harder.

Important: All prerequisite biology courses must be for science or pre-health majors. Survey-level courses designed for non-majors are generally not accepted by DPT programs.

What You Will Cover

A typical organismal biology course includes:

• Evolution and phylogenetics: natural selection, genetic drift, speciation, phylogenetic trees, Hardy-Weinberg equilibrium, evidence for evolution
• Diversity of life: bacteria, archaea, protists, fungi, plant diversity (bryophytes through angiosperms), animal diversity (invertebrate phyla, vertebrate classes)
• Plant biology: plant structure (roots, stems, leaves, vascular tissue), resource acquisition and transport, angiosperm reproduction
• Animal form and function: body plans, tissue types, gas exchange, circulation, digestion, homeostasis, thermoregulation
• Ecology: population growth models, community ecology (competition, predation, symbiosis), ecosystem ecology (energy flow, nutrient cycling), biomes, conservation biology
• Scientific process: experimental design, hypothesis testing, data analysis, lab reports

Study Strategies That Work

Group similar organisms, then contrast them. When studying diversity, build comparison tables. Vascular vs. nonvascular plants. Protostomes vs. deuterostomes. Ectotherms vs. endotherms. Focusing on key distinguishing features is more efficient than memorizing each group in isolation.

Draw phylogenetic trees from memory. Phylogenies are the organizational backbone of this course. After studying a tree, close your notes and redraw it. Add the key innovations (synapomorphies) that define each branch. If you cannot reconstruct the tree, you have not learned it yet.

Use the "what if" method. After learning how a system works (plant vascular transport, animal thermoregulation, predator-prey dynamics), ask what would happen if you removed, broke, or modified one component. Exam questions in organismal biology frequently test this kind of applied reasoning.

Connect concepts across biological scales. The central challenge of this course is linking molecules to cells to tissues to organs to organisms to populations to ecosystems. Build concept maps that trace these connections explicitly. For example: how does photosynthesis (molecular) relate to plant growth (organismal) relate to primary productivity (ecosystem)?

Practice with real organisms. If your course has a lab component, photograph specimens and create your own field guide. Use iNaturalist (free app) to practice species identification from photos. The app uses AI-powered identification and contributes to real biodiversity databases.

Study in layers, not marathons. Taxonomic groups, phylogenies, and ecological concepts require spaced repetition. Short daily review sessions significantly outperform long cramming sessions for this type of material.

Read before class. At minimum, look at the figures and captions in your textbook before lecture. Within 24 hours after lecture, rewrite your notes in complete sentences and add labels to diagrams while the material is fresh.

Free Resources

Video lectures:

• Khan Academy Biology covers evolution, ecology, and organismal diversity with videos and practice exercises
• CrashCourse Biology has 50 short animated episodes covering evolution, ecology, and diversity, produced with HHMI BioInteractive
• CrashCourse Ecology offers 12 focused episodes on population dynamics, community ecology, and ecosystems
• iBiology features 600+ free videos from leading scientists on topics across biology

Free textbooks:

• OpenStax Biology 2e covers the full two-semester biology sequence, free under Creative Commons
• Georgia Tech Organismal Biology OER is a free resource covering biodiversity, evolutionary history, growth and reproduction, signals, nutrition, and homeostasis
• An Interactive Introduction to Organismal and Molecular Biology from Michigan State University features interactive HTML5 content with embedded quizzes and simulations

Interactive tools:

• HHMI BioInteractive provides research-based multimedia resources, virtual labs, and data analysis activities
• Genetic Science Learning Center (University of Utah) offers interactive modules on genetics, ecology, and evolution
• PhET Simulations includes interactive simulations for natural selection and gene expression

Recommended Textbooks

• Campbell Biology (12th edition) by Urry, Cain, Wasserman, Minorsky, and Orr (Pearson) is the most widely assigned text for two-semester biology sequences
• Life: The Science of Biology (12th edition) by Hillis, Heller, Hacker, Hall, Laskowski, and Sadava (Macmillan/Sinauer) has strong evolution and ecology coverage
• Principles of Life (3rd edition) by Hillis et al. (Macmillan) is a more concise alternative for one-semester or accelerated Biology II courses
• OpenStax Biology 2e by Clark, Choi, and Douglas is free and peer-reviewed

Apps Worth Using

• Anki for spaced repetition flashcards, especially useful for taxonomy, phylogenies, and process steps
• iNaturalist for AI-powered species identification from photos during lab and field work
• Quizlet for pre-made biology flashcard decks with game-based study modes
• Khan Academy (app available) for structured lessons with built-in practice and progress tracking

How This Connects to DPT School

The comparative and systems-level thinking you develop in organismal biology translates directly to DPT coursework. Understanding how structure relates to function across organisms helps you grasp why human anatomy is designed the way it is, how tissues respond to mechanical stress, and why certain movement patterns exist. The ecology concepts (systems interactions, energy flow, population dynamics) parallel the systems thinking used in physical therapy: understanding how a patient's body systems interact, how environmental factors affect recovery, and how to think about health outcomes at the population level.

This is part of our Study Saturday series, where we break down how to succeed in each PT school prerequisite course. For an overview of all prerequisites, see understanding PT school prerequisites.