I have started combing through the new AP Biology CED and comparing it to the old. My goal is to tease out any differences to get ready for teaching AP Biology next year. As I go, I am writing down those differences and I thought it would be helpful to share it with the world of AP Biology teachers!
If you’ve checked out the College Board’s announcement for the 2025 AP Biology Course and Exam Description (CED), your first impression might be the same as mine: nothing looks drastically different at first glance. And honestly, that’s true—there aren’t a bunch of new concepts or surprise additions.
Instead, most of the changes are about clarity, structure, and organization—and I’m actually really happy about that! The new CED feels much more streamlined and easier to navigate, which should help both teachers and students keep track of where everything fits.
Why I’m Writing This
As I prepare for the upcoming school year, I’ve been doing a side-by-side comparison of the old and new CEDs—and taking detailed notes on everything that’s changed. I figured, why not share what I find with the AP Bio teacher community?
Alongside this blog, I’m also updating all of my AP Biology Unit Learning and Study Guides, which I use in my own classroom and share on my website and Teachers Pay Teachers store. So if you’re looking for resources that are fully aligned to the 2025 framework, check it out here! The Keys also highlight every EK and LO that are different from the previous CED so you can easily find the changes!
One Big Win: The New Numbering System
The first thing that jumped out to me was how much more intuitive the numbering system is. Each Learning Objective (LO) and Essential Knowledge (EK) statement now has a clear label that ties it directly to its unit and topic.
For example:
- 1.1.A.1 = Unit 1, Topic 1, Learning Objective A, Essential Knowledge 1.
- 2.3.B.1 = Unit 2, Topic 3, Learning Objective B, EK 1.
It’s simple, it’s logical, and it makes referencing content so much easier—especially when designing lessons, assessments, or study guides. Love it.
Topics Are Now Linked to Big Ideas
Each topic is also clearly labeled with the primary Big Idea it’s connected to. This is a great move—it’ll help both teachers and students see how those four overarching Big Ideas thread through every unit.
As a teacher, I appreciate this reminder to keep circling back to those big-picture concepts. For students, it reinforces that what they’re learning in one unit connects to the broader themes of biology.
What’s Actually Different in Terms of Content?
Let’s go unit by unit, topic by topic through the new AP Biology CED and see what has changed!
Unit 1: Chemistry of Life
Topics 1.1 & 1.2: Water and Elements
The unit still kicks off with water and biological elements, but there are a few key updates:
- More detail on the properties of water, including high specific heat and high heat of vaporization. I usually focus on water as the “universal solvent,” so I’ll be adjusting my notes to emphasize these new additions.
- Sulfur is now explicitly listed in Topic 1.2 as important for protein synthesis—so it’s no longer just CHONP, it’s CHONPS now!
Topic 1.3: Introduction to Macromolecules
Same general content, but expanded explanation of dehydration synthesis and hydrolysis. If you’ve always taught these reactions with diagrams or models, you’re already ahead of the game—this just gives students a little more context.
Macromolecules: 1.4–1.7
Each macromolecule now has its own dedicated topic—finally! I’ve always broken them up this way in my own teaching, so it’s nice to see the framework match that structure.
- 1.4 Carbohydrates
- 1.5 Lipids
- 1.6 Nucleic Acids
- 1.7 Proteins
Not sure why Proteins come last, after Nucleic Acids—I personally prefer to teach proteins first, since it makes more sense how to get from DNA to proteins. But hey, you can still teach them in any order you like! Let me know your preference in the comments.
The Carbs, Proteins, and Nucleic Acids topics haven’t changed much, but the Lipids section finally got some love. New additions include:
- A clearer distinction between saturated and unsaturated fats
- Explanation that saturated fats solidify more easily at cooler temps
Specific lipid functions:
- Energy storage and insulation (though oddly, no mention of “blubber”)
- Steroid hormones (no examples given—just a general nod to growth and development)
- Cholesterol as a membrane stabilizer in animals
- And, of course, phospholipids
That’s it for Unit 1! If you’ve noticed anything I missed—or if you have thoughts on teaching order, new emphasis areas, or how you’re adjusting your lessons—drop a comment! I’d love to hear how other AP Bio teachers are interpreting and integrating the new CED.
Unit 2: Cells
Unit 2 didn’t get a dramatic overhaul in the 2025 CED, but there are a few notable changes—especially in how organelle content is structured, and how membrane transport topics are distributed. Some concepts were clarified or expanded, while a few other details were streamlined or relocated to other units. Let’s take a look at the updates:
2.1 Cell Structure: Subcellular Components
This topic now covers more ground than before, as Topic 2.2 (Cell Structure and Function) has been partially merged into it. The rest of 2.2, which focused on cell energetics, has been moved to Unit 3 (which makes much more sense thematically).
There’s also a bit more specific detail provided for organelles. One standout addition is the vacuole—the new CED compares plant and animal vacuoles in terms of size, number, and function, which helps students better understand structural differences across cell types.
Another welcome addition is the introduction of the endomembrane system—a term that wasn’t included in the previous CED but is definitely important when talking about organelle interactions.
2.2 Cell Size
This topic got a bit of a rewording, with slightly less emphasis on specific cell adaptations and more focus on core concepts. The list of illustrative examples hasn’t changed, so the actual content is essentially the same—just phrased more clearly.
Also, a connection to metabolic rate has been added. The relationship between surface area-to-volume ratio and metabolic demand is now included here—it used to live in Topic 8.2 (Energy Flow in Ecosystems). It’s a better fit here in Unit 2, where cell structure and function are front and center.
2.3 Cell Membranes
There’s a little more detail here, especially around hydrophobic vs. hydrophilic proteins and how they’re positioned within the membrane. That should help reinforce the structure-function relationship.
One small change worth noting: cholesterol is now described as a component of “vertebrate animal” membranes, rather than “eukaryotic” membranes. A minor but more precise update.
2.4 Membrane Permeability
This topic got a nice clarification boost. The new CED does a better job explaining why membranes are selectively permeable, tying it directly to the hydrophobic interior of the lipid bilayer. That’s a much clearer explanation than the old “because of the membrane’s structure.”
There’s also more detail about how various molecules cross membranes, which helps students make sense of diffusion vs. facilitated transport.
As for cell walls, the CED now points out that they help prevent osmotic lysis, which wasn’t mentioned before. On the flip side, it no longer includes what cell walls are made of complex carbohydrates)—a bit of a strange omission.
2.5 Membrane Transport
This topic is largely unchanged. Just a few wording tweaks here and there, but no big content shifts. It still covers the general categories of active and passive transport, and remains a central spot to introduce the big-picture ideas.
2.6 Facilitated Diffusion
This topic now focuses only on passive transport via transport proteins. The active transport content—which always felt a little out of place here—has been moved to Topic 2.8. Honestly, this makes a lot more sense. Facilitated diffusion and protein pumps aren’t doing the same job, so separating them should help reduce student confusion.
2.7 Tonicity and Osmoregulation
This topic sticks to the basics: osmosis, water potential, and how cells regulate water balance. There’s a bit of rewording, but overall, the content and expectations are exactly the same as before.
2.8 Mechanisms of Transport
Okay, let’s talk about this one.
Even though the title remains “Mechanisms of Transport,” the only content in the 2025 CED under this topic is about active transport, specifically the sodium-potassium pump. That’s a sharp departure from the broader overview the topic title suggests.
It honestly seems like either:
- The title should have been changed to “Active Transport”, or
- More content about other types of transport should have been included under this topic.
So how should we teach it? The best move seems to be covering general transport mechanisms under 2.5, and treating 2.8 as your space to go deeper into active transport, especially protein pumps. Strangely, there’s still no direct mention of simple diffusion in the CED (old or new), but I definitely still include it when teaching.
2.9 Compartmentalization
No changes here! The EKs are word-for-word identical to the previous CED.
2.10 Origins of Cell Compartmentalization
The first Learning Objective remains unchanged.
However, the second Learning Objective—which asked students to: “Describe the relationship between the functions of endosymbiotic organelles and their free-living ancestral counterparts”
…has been removed.
Honestly, it probably was a little redundant, since the core idea of endosymbiosis is already covered in the first LO. Still, it’s a noticeable omission for those of us who’ve emphasized that link between modern organelles and their bacterial ancestors.
That wraps up Unit 2! The core themes remain the same, but there are some structural shifts that affect how we organize and sequence our teaching. The organelle content is now more consolidated, membrane transport is better divided between passive and active mechanisms, and a few confusing bits (like protein pumps in facilitated diffusion) have been cleared up.
Unit 3: Cellular Energetics
Unit 3 saw some meaningful updates in the 2025 AP Biology CED—most notably a reorganization of early topics and a few clarifications in how photosynthesis and respiration are presented. Some changes make the content more streamlined, but a few adjustments might raise eyebrows for teachers paying close attention.
3.1 Enzymes
The first two topics from the previous CED—enzyme structure and enzyme function—have been merged into a single topic: 3.1 Enzymes.
This new version also introduces the concept of the enzyme-substrate complex, which is a helpful and much-needed addition. It’s a more complete way to describe how enzymes function during reactions and gives students better conceptual grounding.
3.2 Environmental Impacts on Enzyme Function
A new EK has been added that explains why enzymes denature at extreme temperatures and pH levels—pointing to disruptions in hydrogen bonds that destabilize the protein’s structure. This gives a more molecular-level explanation for denaturation, which helps connect this topic to earlier discussions on protein structure.
However, a couple of things were removed:
- The pH equation is no longer mentioned in the CED, even though it’s still on the AP Biology Formula Sheet. Oddly inconsistent.
- The old statement that competitive inhibitors could bind “reversibly or irreversibly” has been trimmed down. The phrase “or irreversibly” was removed, which makes the definition more limited. Not inaccurate, but less complete.
3.3 Cellular Energy
The original Learning Objective remains, but a new one has been added emphasizing that glycolysis and phosphorylation are conserved processes across all forms of life. This addition links well to evolutionary biology and highlights biochemical universality—a key AP theme that also shows up in Unit 7.
3.4 Photosynthesis
This topic got the most substantial update in the new AP Biology CED.
- Content that used to be part of Topic 2.2 (Cell Organelles) is now incorporated here.
- There’s more detail about where and how each step of photosynthesis occurs, which should help students visualize the overall process better.
That said, a couple of Essential Knowledge statements in this section could use improvement:
- EK 3.4.B.1 says: “In photosynthesis, electrons that pass through the thylakoid membrane are picked up and ultimately transferred to NADP+, reducing it to NADPH in photosystem I.”
This phrasing is problematic. Electrons aren’t actually passing through the membrane—they’re being passed between proteins embedded in the membrane. And technically, Photosystem I doesn’t reduce NADP+; it re-excites the electron, which then moves through additional proteins before NADP+ is finally reduced.
The exclusion statement says students don’t need to know the enzyme names, but this summary still oversimplifies the process in a way that could cause confusion.
- EK 3.4.B.2 states: “During photosynthesis, chlorophylls absorb energy from light, boosting electrons to a higher energy level in photosystems I and II. Water then splits, supplying electrons to replace those lost from photosystem II.”
The order here is confusing. The splitting of water actually initiates the process, not follows it. This statement suggests water splits after electron excitation, when in reality, Photosystem II starts by splitting water to generate the electrons that are then energized. Again, not technically wrong—but not great for building clear mental models.
3.5 Cellular Respiration
This topic is largely the same, but there are two notable changes:
- A new statement was added explaining that the intermembrane space of the mitochondria becomes more acidic due to H+ ion accumulation during the electron transport chain. A great addition for understanding how the proton gradient drives ATP synthesis.
- However, the topic still follows an illogical order (in my opinion), starting with the ETC, then discussing glycolysis and the Krebs cycle after. I think most of us teach the pathway in chronological order, starting with glycolysis. It would be nice if the CED aligned with how it’s taught in practice.
Also removed: ENE-1.L.7 “The conversion of ATP to ADP releases energy, which is used to power many metabolic processes.”
This was a really helpful EK, and it’s disappointing to see it cut. The Learning Objective still states that students are expected to understand how energy is used in the cell, but this direct statement tied ATP hydrolysis to energy release in a clear, concrete way. Its absence feels like a missed opportunity for clarity.
Removed Topic: 3.7 Fitness
This topic is no longer part of Unit 3. Its Learning Objectives—about cellular processes influencing fitness—have been moved to Topic 7.2 in the Natural Selection unit, which honestly makes a lot more sense thematically.
So overall, Unit 3 keeps most of its core structure, but gets a few more specifics and one confusing photosynthesis rewrite. Some content shifts help streamline instruction, while others (like omitting the ATP energy release EK) seem like odd choices.
Unit 4: Cell Signaling and the Cell Cycle
Unit 4 didn’t undergo a major overhaul, but there are a few small updates worth noting. Most of the changes involve added clarification and a bit of streamlining—especially when it comes to the Essential Knowledge (EK) statements. Let’s walk through the updates, topic by topic.
4.1 Cell Communication
The only change here is the removal of one illustrative example: “Plasmodesmata between plant cells allow material to be transported from cell to cell.”
All the other examples (like local regulators and immune cell interactions) are still included. Other than that, this topic remains exactly the same.
4.2 Introduction to Signal Transduction
This topic also stays largely the same. The Learning Objectives and EKs have just been slightly reworded for clarity.
A single new bullet point has been added to EK 4.2.B.1, explaining that: “Receptors may be located on the surface of a target cell or in the cytoplasm or nucleus of the target cell.”
It’s a nice clarification that helps students visualize how different kinds of signals reach their targets.
4.3 Signal Transduction
Here’s where a more noticeable structural change happens. The 2025 CED combines the old Topics 4.3 and 4.4 into one unified topic (now just called 4.3).
- The first Learning Objective and EK have been revised to reflect what used to be Topic 4.3.
- The content from the old Topic 4.4 now appears under LO 4.3.B.
- Most illustrative examples remain the same, but one has been removed: “Expression of the SRY gene triggers the male sexual development pathway in animals.”
It’s not a huge change, but merging these topics does help reduce redundancy and improve the overall flow of the unit.
4.4 Feedback
Not much has changed here—the language and core concepts are essentially the same.
The only difference: the positive and negative feedback mechanisms, which were previously written as separate EKs, are now grouped as bullet points under a single EK. It’s a small formatting change, but one that makes the topic feel a bit more concise.
4.5 The Cell Cycle
This topic gets a small but helpful expansion!
- The first Learning Objective now includes specifics about the G1, S, and G2 phases of the cell cycle.
- A second Learning Objective (4.5.B) has been added that breaks down the stages of mitosis—Prophase, Metaphase, Anaphase, Telophase—and also includes Cytokinesis.
These additions provide more clarity around a process that students often struggle with. It’s not new content per se, but it’s a clearer outline of what students are expected to know.
4.6 Regulation of the Cell Cycle
No changes here at all. This topic remains exactly the same in both structure and content.
That’s it for Unit 4! Just a few small changes to clarify, condense, or slightly restructure the material. Nothing too overwhelming here—but worth adjusting your materials to reflect the merged topics and added detail.
Unit 5: Heredity
There have been quite a few changes to Unit 5 in the 2025 AP Biology CED—some content has been expanded, some shifted around, and one topic has been removed altogether. Let’s take a look at what’s new and what’s gone.
5.1 Meiosis
This topic has been significantly expanded. The updated CED now includes a step-by-step description of each stage in Meiosis I and II, which gives students a more detailed understanding of the process. It’s a good addition that brings clarity to what can often be confusing for students.
5.2 Meiosis and Genetic Diversity
This one is mostly unchanged, but there’s a small update: the concept of nondisjunction (when sister chromatids or homologous chromosomes fail to separate properly) has been added here. Previously, nondisjunction was covered in Topic 5.5, but since that topic has been removed, this is its new home.
5.3 Mendelian Genetics
One Learning Objective has been removed from this topic: “EVO-2.A Explain how shared, conserved, fundamental processes and features support the concept of common ancestry for all organisms.”
This LO and its related EKs have now been moved to Unit 3 (Cellular Energetics), Unit 6 (Gene Expression), and Unit 7 (Natural Selection). Honestly, this move makes sense. That content always felt a little out of place in a unit focused on Mendelian inheritance.
5.4 Non-Mendelian Genetics
This topic gets some great additions! Three new EK statements now explicitly describe:
- Codominance
- Incomplete dominance
- Pleiotropy
These were previously implied but are now clearly defined in the CED, which is helpful for instruction and review.
That said, one EK was removed: “IST-1.J.3 Many traits are the product of multiple genes and/or physiological processes acting in combination; these traits therefore do not segregate in Mendelian patterns.”
Surprisingly, there’s now no mention of polygenic traits or multiple alleles anywhere in the new AP Biology CED, which feels like a pretty big omission for a unit on genetics.
5.5 Environmental Effects on Phenotype
No changes here!
5.6 Chromosomal Inheritance
This topic has been completely removed from the 2025 CED.
Some of the core ideas—like chromosome behavior and inheritance patterns—have been distributed to other topics within Unit 5 and Unit 6. However, a lot of the illustrative examples that used to be here (like Tay-Sachs, Huntington’s disease, and Down Syndrome) have been taken out entirely.
The only example that remains is Sickle Cell, which now appears in Unit 6.
So overall, Unit 5 has been streamlined quite a bit. The focus is now more squarely on the mechanics of inheritance and genetic expression, with less emphasis on specific human genetic disorders or chromosomal conditions.
If you’re revising your curriculum or updating your classroom resources, don’t forget to check out our 2025 CED-aligned study guides—condensed, clear, and ready to go with zero prep required!
Unit 6: Gene Expression and Regulation
Unit 6 hasn’t changed too dramatically, but there are a few subtle shifts, added clarifications, and some restructuring of content that’s worth noting. Overall, the 2025 AP Biology CED has aimed to tighten things up, make concepts clearer, and reassign a few ideas to more logical locations.
6.1 DNA and RNA Structure
This topic is mostly the same, but a helpful phrase has been added to clarify that chromosomes are made of DNA coiled around histones and other proteins.
Also, some of the Essential Knowledge (EK) statements have been condensed and simplified. So while the core concepts haven’t changed, there are actually fewer EKs listed—just more concise ones.
6.2 DNA Replication
No changes here!
6.3 Transcription and RNA Processing
- A clarification that DNA is in the nucleus and ribosomes are in the cytoplasm,
- An explanation of the importance of the Poly-A tail and 5’ GTP cap in protecting and stabilizing mRNA.
A few new details have been added here to flesh things out:
Like in 6.1, some of the EKs have been merged or reworded slightly for smoother flow.
One thing that was removed: the explanation of template vs. noncoding strands. The 2020 CED included this statement: “The DNA strand acting as the template strand is also referred to as the noncoding strand, minus strand, or antisense strand…”
This distinction is no longer mentioned in the 2025 version, which is a bit surprising, since it’s such a common point of confusion for students.
6.4 Translation
This topic is mostly untouched. The one change is the removal of the statement that translation requires energy, which feels like an odd omission, since it’s still true.
A small but helpful addition: the start codon AUG is now explicitly listed as the only codon students are required to know for the AP Exam. That’s a nice bit of clarity for both teachers and students.
6.5 Regulation of Gene Expression
This topic gets a couple of helpful additions:
- The concept that some genes are constitutively expressed while others are inducible.
- A mention that gene products determine phenotype, which was moved here from Topic 6.7 (a better fit, I think).
Also worth noting: the EK about prokaryotic operons still includes inducible and repressible systems, but the lac operon is no longer provided as a named example. It is still a great example to use, but it’s not in the CED.
6.6 Gene Expression and Cell Specialization
No changes at all here.
6.7 Mutations
This is where most of the action happens in Unit 6. Several new terms and clarifications were added:
- Types of mutations like point mutations, frameshift, nonsense, and silent are now defined directly in the EKs.
- The term aneuploidy has been added to the section on nondisjunction and chromosomal abnormalities.
However, quite a bit was also removed:
- The older phrasing about how changes in chromosome number can cause sterility or increased vigor is gone.
- The specific examples of Trisomy 21 and Turner Syndrome have been taken out.
- A new exclusion statement clarifies that knowing individual genetic disorders is no longer required for the AP Exam.
Illustrative examples have also been trimmed. Pesticide resistance, antibiotic resistance, and sickle cell heterozygote advantage are no longer listed under Topic 6.7. That said:
- Antibiotic resistance still appears in Unit 7.
- Sickle cell is still an illustrative example in 7.2 Natural Selection, though the term heterozygote advantage is only found in 8.7 Disruption in Ecosystems.
6.8 Biotechnology
Last but not least, Topic 6.8 has a couple of small updates:
- A bit more detail has been added about the PCR (polymerase chain reaction) process,
- And there’s a clearer explanation of how DNA sequencing works.
That’s about it for biotech—no major restructuring here.
Unit 7: Natural Selection
Unit 7 is still the longest unit in AP Biology—but now it has one fewer topic than before! The 2025 AP Biology CED includes some significant content cuts, a few reshuffles, and a fair amount of rewording for clarity. Let’s break down what’s changed.
7.1 Introduction to Natural Selection
This topic is unchanged in terms of content. Just a bit of rephrasing here and there to make the language more student-friendly.
7.2 Natural Selection
The first Learning Objective (LO) remains the same as before. A new LO has been added that emphasizes how cellular-level variation can affect a population’s survival—a concept that was previously part of Topic 3.7: Fitness. That old topic is now gone, and its core ideas have been absorbed here.
One noticeable omission: the peppered moth is no longer included as an illustrative example of natural selection. That feels like a surprising change, considering how iconic the example is. However, it hasn’t disappeared completely—it still shows up under Scientific Practice 6.C as it did in the previous CED, where students are asked to analyze data and justify claims related to peppered moth evolution.
7.3 Artificial Selection
This topic has been trimmed down. The second LO—about convergent evolution—has been moved to Topic 7.10, which actually makes way more sense. It never quite fit under artificial selection in the first place!
7.4 Population Genetics
This topic gets a nice upgrade. Rather than just listing genetic phenomena like bottlenecks, founder effects, and migration, the CED now includes brief explanations of each. It also adds more detail about genetic drift and gene flow. These changes make the content more complete and easier to teach.
7.5 Hardy–Weinberg Equilibrium
I might be biased, but I love Hardy-Weinberg—like a puzzle to solve!
The first LO gets a small but helpful addition that clarifies that Hardy–Weinberg conditions don’t actually exist in real populations, but serve as a null hypothesis. That’s a solid clarification and a great way to tie stats and biology together.
The second LO has been removed, with its content absorbed into the expanded 7.4.
7.6 Evidence of Evolution
The first LO sticks around unchanged. The second LO, however, has been removed. It focused on how certain molecular and cellular processes are conserved across life forms. It looks like that content was relocated to Topic 3.3, specifically in EK 3.3.B.1, which now highlights glycolysis and oxidative phosphorylation as conserved core processes.
7.7 Common Ancestry and 7.8 Continuing Evolution
No changes here—these two topics made it through the update untouched!
7.9 Phylogeny
This topic received a bit of extra clarification in its EKs, especially when it comes to comparing and contrasting cladograms and phylogenetic trees. A small change, but helpful for student understanding.
7.10 Speciation
Here’s where that convergent evolution LO from 7.3 now lives (and rightfully so). The 2025 CED also adds clear definitions for allopatric and sympatric speciation, which should help students get a better grasp of these important terms.
7.11 Variations in Populations
No changes here!
7.12 Origins of Life on Earth
This topic saw some pretty big cuts. Two major hypotheses about the origin of life—the Earth-based inorganic precursors theory and the meteorite delivery theory—have been completely removed.
Also gone are references to early chemical experiments (like Miller-Urey) that simulated prebiotic Earth conditions. Now, the sole focus is on the RNA World Hypothesis, which has been expanded with a bit more detail—but without any guidance on where that RNA came from. These molecules had to get here/form somehow!
Wait… Where Did “Extinction” Go?
Good catch! The Extinction topic (formerly 7.11) has been removed from the CED entirely. Most of the content wasn’t relocated—it’s just… gone.
That said, one EK about how human activity can drive extinction has been moved to Topic 8.7: Disruptions in Ecosystems. And the content about adaptive radiation is still part of 7.10.
Unit 8: Ecology
Unit 8 doesn’t get a total overhaul, but there are some notable updates—especially in Topic 8.2. Most of the other changes across the unit are minor wording tweaks aimed at improving clarity.
8.1 Responses to the Environment
There’s just one change in Topic 8.1, and it’s a small but interesting one. In Essential Knowledge (EK) 8.1.B.2, the phrase “Natural Selection” has been swapped out for “Fitness.” The updated EK now reads:
“Fitness favors innate and learned behaviors that increase survival and reproductive success.”
Honestly, I think “Natural Selection” might’ve made more intuitive sense here—especially for students still solidifying their grasp of evolutionary processes. The term “fitness” is still accurate, but maybe not quite as clear.
8.2 Energy Flow Through Ecosystems
Now here’s where the big changes happen. First, a quick one: the EK about the relationship between organism size and metabolic rate has been removed from this topic—it is found now inTopic 2.2. Some other EKs have also been expanded with more definitions and clarifications.
But the real standout is the major expansion of the content around the cycling of matter. In previous versions, this was briefly addressed under a broader objective. Now, each of the major biogeochemical cycles—water, carbon, nitrogen, and phosphorus—gets its own dedicated EK. This makes the second Learning Objective in 8.2 way more detailed than before.
Honestly, Topic 8.2 is starting to feel pretty bloated. I think it would’ve made more sense to break out the cycling of matter into its own separate topic from flow of energy.
8.3 Population Ecology
Only a very minor change here! The College Board now clarifies that a population refers specifically to a group of individuals from the same species. Small edit, but it might help with clarity.
8.4 Effect of Density on Populations
This one stays mostly the same. There’s some light rewording and the addition of a clear definition for carrying capacity, which is a helpful inclusion.
8.5 Community Ecology
Not much changes here either. There’s now a definition added for communities, and one Learning Objective (about community structure and energy availability) has been removed—probably because it overlaps with the now more robust Topic 8.2.
8.6 Biodiversity
Only one real change in this topic: the removal of the EK that read, “SYI-3.G.1 The diversity of species within an ecosystem may influence the organization of the ecosystem.”
It’s unclear why this was cut, as it’s still an important idea, but presumably it was removed to streamline content.
8.7 Disruptions in Ecosystems
Almost there—the final topic of AP Biology!
One addition here: the concept of heterozygote advantage has been moved from Topic 6.7 to this one, which actually makes more thematic sense. The only other change is a small but meaningful rewording in an EK:
Before: “Mutations are random.”
Now: “Mutations are not directed by specific environmental pressures.”
It’s basically the same idea, but I do kind of miss the word “random”—it’s more direct and easy for students to grasp.
And that’s a wrap for Unit 8!
No Prep AP Biology Learning and Study Guide
If you’re prepping for the 2025 AP Biology exam, make sure to check out our learning and study guides—they’re fully aligned with the new CED, print-ready, and designed to be compact but thorough. Minimal prep, maximum impact! The Keys also highlight every EK and LO that are different from the previous CED so you can easily find the changes!
So what do you think of the new 2025 AP Biology CED?
