IB DP Biology HL 2025 Revision Resources
IB DP Biology HL 2025 Revision Resources
IB DP Biology HL 2025 Revision Resources includes Exam Style Questions , Study Notes , flashcards and syllabus details. These materials will help ace IB Biology HL exam. IB DP Biology HL study material here is based on latest Syllabus for First Assessment in 2025. IBO info for IB DP Biology
IB DP Biology HL 2025 Revision Resources
Exam Style QuestionsNew
Mock Tests (2024 updated)
Study NotesNew
FlashcardsNew
IB DP Biology HL 2025 Course Structure
For IB DP Biology HL students, the program is designed to foster a deep understanding of scientific principles and skills through a concept-driven and experimental approach. Key elements include:
- Engaging Experimental Work – Students participate in hands-on experiments and labs to develop practical skills and apply theoretical knowledge.
- The Nature of Science – This overarching theme encourages students to explore science’s methodologies, values, and the impact of scientific understanding in a broader societal context.
- Concept-Based Syllabus – The curriculum is structured around fundamental concepts, helping students see connections across biological topics and understand their relevance.
- Scientific Investigation – Students complete one piece of internally assessed work, an independent research project that encourages inquiry and scientific methodology.
- Collaborative Sciences Project – This interdisciplinary project allows students to work with peers to tackle scientific problems, promoting teamwork and application of knowledge across scientific disciplines.
These core components equip students with a robust foundation for further study or careers in scientific fields, emphasizing analytical thinking, collaboration, and a holistic understanding of science.
IB DP Biology HL 2025 V/s IB DP Biology SL 2025
The HL course requires students to increase their knowledge and understanding of the subject, and so provides a solid foundation for further study at university level.
The HL course has a recommended 240 teaching hours, compared to 150 hours for the SL course. This difference is reflected in the additional content studied by HL students. Some of the HL content is conceptually more demanding and explored in greater depth. The increased breadth and depth at HL result in increased networked knowledge, requiring the student to make more connections between diverse areas of the syllabus.
IB DP Biology HL 2025 Paper 2
- Duration: 2 hour and 30 minutes
- Weighting: 44%
- Marks: 80
- Section A : 48 marks
- Data-based question.
- Short-answer questions on standard level and additional higher level material
- Section B: 32 marks
- Extended-response questions on standard level and additional higher level material.
Two of three extended-response questions to be attempted by candidates
- Extended-response questions on standard level and additional higher level material.
- CALCULATOR ALLOWED
- Data booklet provided
IB DP Biology HL 2025 Paper 1A and Paper 1B
- Duration: 2 hour
- Paper 1 is presented as two separate booklets.
- Paper 1A and Paper 1B are to be completed together without interruptions.
- Paper 1A 40 marks
- 40 multiple-choice questions on standard level and additional higher level material.
- No marks are deducted for incorrect answers
- Paper 1B 35 marks
- Four data-based questions related to experimental work and the syllabus.
- CALCULATOR ALLOWED
- Data booklet provided
- 36 % weight
- Marks: 75
IB DP Biology HL 2025 Revision Resources Exam Style Questions and High Quality Resources including Flashcards and Past Papers
Resources like exam-style questions, flashcards, and other study aids is a great way to reinforce learning and prepare for IB DP Biology HL 2025 exams. Expect to find all relevant Exam Style Questions and High Quality Resources including Flashcards , Study notes and Past Papers solution for IB DP Biology HL at IITian Academy
Question
The foxglove, Digitalis purpurea, was once classified in the figwort family. The figwort family has been reclassified and is now much smaller.
Why were species such as the foxglove moved into other families?
A. The appearance was too dissimilar.
B. The plants are found in different locations.
C. The genera were different.
D. The DNA sequences indicated different ancestry.
Answer/Explanation
Ans:D
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[h] IB DP Biology HL A2.2 Cell structure Flashcards
[q] Explain how an improvement in apparatus allowed for greater understanding of cell structure.
Nature of Science: Developments in scientific research follows improvements in apparatus- the invention of the electron microscopes led to greater understanding of cell structure.
[a] Technology = machinery and equipment developed from the application of scientific knowledge.
Begets = gives rise to; brings about.
Discovery = the act of finding or learning something for the first time.
[q] Define “resolution.”
Understanding: Electron microscopes have a much higher resolution than light microscopes.
[a] The smallest interval distinguishable by the microscope, which then corresponds to the degree of detail visible in an image created by the instrument.
[q] Compare the functionality of light and electron microscopes.
Understanding: Electron microscopes have a much higher resolution than light microscopes.
[a] LIGHT MICROSCOPES
Use lenses to bend light and magnify images.
Used to study dead or living cells in color.
Cell movement can be studied.
Larger field of view.
Objects can be magnified up to 2000X.
Can resolve objects 200 nm apart.
ELECTRON MICROSCOPES
Uses electron beams focused by electromagnets to magnify and resolve.
Requires cells to be killed and chemically treated before viewing.
No movement can be seen.
Without stain or dye, no color can be seen.
Smaller field of view.
Can magnify objects up to 250,000 times.
Can resolve objects that are 0.2 nm apart.
[q] Outline the major differences between prokaryotic and eukaryotic cells.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Prokaryotic Cells
Smaller (about 0.2 – 2 um)
DNA in nucleoid region (no nuclear membrane)
No membrane bound organelles
Cell wall of peptidoglycan
Smaller ribosomes (70s) in cytoplasm
DNA is circular and without histone proteins
Has plasmid DNA
Asexual cell division
Eukaryotic Cells
Bigger (10-100 um)
DNA in a true nucleus
Membrane bound organelles present
Cell wall of cellulose (plants) or chitin (fungus)
Larger ribosomes (80s) in cytoplasm and on ER
//also has 70s ribosomes within mitochondria and chloroplasts//
DNA is linear with histone proteins
Do not have plasmid DNA
Asexual or sexual cell division
[q] State the function of the prokaryotic cell cell membrane.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Forms the boundary of the cell, acts as a selective barrier allowing certain materials to pass into and out of the cell, but not others.
[q] State the function of the prokaryotic cell nucleoid.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Location of the genetic material for inheritance and protein coding; circular DNA not associated with histone proteins.
[q] State the function of the prokaryotic cell plasmid.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Smaller, circular DNA not associated with DNA in the nucleoid. Often contains genes for antibiotic resistance.
[q] State the function of the prokaryotic cell cytoplasm.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Primarily water and dissolved molecules, the location of many metabolic reactions.
[q] State the function of the prokaryotic cell ribosome.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Responsible for catalyzing the formation of polypeptides during protein synthesis. Size is 70s.
[q] State the function of the prokaryotic cell cell wall.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Found in most prokaryotic cells.
Provides shape and protection to the cell.
Composed of peptidoglycan.
[q] State the function of the prokaryotic cell pili.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Pilus (singular)
Found in some (not all) prokaryotic cells.
Hair-like structures that help the cell attach to surfaces.
[q] State the function of the prokaryotic cell capsule.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Found in some (not all) prokaryotic cells.
Helps the cell maintain moisture and adhere to surfaces. Protects the cells from other organisms.
[q] State the function of the prokaryotic cell flagella.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Found in some (not all) prokaryotic cells.
Long extension used for cell locomotion.
[q] Contrast the size of eukaryotic and prokaryotic ribosomes.
Understanding: Prokaryotes have a simple cell structure without compartmentalization.
[a] Prokaryotes have a smaller, 70s ribosome.
Eukaryotes have a larger, 80s ribosome. Although, the mitochondria and chloroplasts within eukaryotic cells have 70s ribosomes.
(The “s” stands for Svedberg unit, a measure of particle sedimentation rate)
[q] Explain why understanding of the ultrastructure of prokaryotic cells must be based on electron micrographs.
Skill: Drawings of the ultrastructure of prokaryotic cells based on electron micrographs.
[a] “Ultrastructures” are small structures of/in a biological specimen that are too little to see with a light microscope.
[q] Draw the ultrastructure of E.coli, including the cell wall, pili, flagella, plasma membrane, cytoplasm, 70s ribosomes, and nucleoid with naked DNA.
Skill: Drawings of the ultrastructure of prokaryotic cells based on electron micrographs.
[a] Cell wall drawn uniformly thick and outside the cell membrane.
Capsule drawn outside the cell wall.
Pili drawn as hair-like structures connected to cell wall.
Flagellum drawn at one end only and longer than pili.
Cell membrane represented by a continuous single line.
70S ribosomes drawn as small discrete dots (not circles).
Nucleoid DNA shown as a tangled line not enclosed in membrane.
Plasmid drawn as a small circular ring of DNA.
Cytoplasm labeled within the cell.
[q] Define “asexual reproduction.”
Understanding: Prokaryotes divide by binary fission.
[a] Asexual reproduction creates offspring from a single parent organism.
The offspring are genetic clones of that parent.
[q] Outline the four steps of binary fission.
Understanding: Prokaryotes divide by binary fission.
[a] 1. The nucleoid DNA replicates to create an exact duplicate copy.
2. The nucleoid DNAs attach to the cell membrane.
3. The cell membrane (and wall, if present) grow, causing the cell to elongate and the DNA molecules to move apart from each other.
4. The cell membrane pinches inward, creating two genetically identical cells.
[q] State the meaning and advantages of eukaryotic cells being “compartmentalized.”
Understanding: Eukaryotes have a compartmentalized cell structure.
[a] Compartmentalization is the presence of membrane bound partitions (organelles) within the eukaryotic cell. The compartments allow for:
1. Specialization of regions within the cell for specific functions.
2. Molecules needed for a specific function to be concentrated in a region within the cell.
[q] State structural differences between plant and animal cells.
[a] Animal Cells
No cell wall
No chloroplasts
No large vacuole
Not a fixed shape
Stores carbohydrates as glycogen
Plant Cells
Cell wall
Chloroplasts
Large vacuole
Fixed shape
Stores carbohydrates as starch
[q] Draw and label a diagram of the ultrastructure of a generic animal cell.
Skill: Drawings of the ultrastructure of eukaryotic cells based on electron micrographs.
[a] Cell membrane shown as a single continuous line.
Nucleus drawn with double membrane and nuclear pores.
Mitochondria with a double membrane, the inner one folded into internal projections, shown no larger than half the nucleus.
Rough endoplasmic reticulum drawn as a multi-folded membrane with dots on surface.
Golgi apparatus drawn as a series of enclosed sacs with evidence of vesicle formation.
80S ribosomes drawn as small discrete dots (not circles) in cytoplasm and on rER.
lysosome and vesicles drawn as circles with single line.
[q] Draw and label a diagram of the ultrastructure of a generic plant cell.
Skill: Drawings of the ultrastructure of eukaryotic cells based on electron micrographs.
[a] Cell wall drawn on outside perimeter with two continuous lines to indicate the thickness.
Cell membrane shown as a single continuous line.
Nucleus drawn with double membrane and nuclear pores.
Vacuole drawn with a single continuous line.
Chloroplast drawn with a double line and internal stacks of thylakoid.
Mitochondria with a double membrane, the inner one folded into internal projections, shown no larger than half the nucleus.
80S ribosomes drawn as small discrete dots (not circles) in the cytoplasm and on rER.
[q] Explain why cells with different functions will have different structures.
[a] Cells will have different types and/or quantities of organelles depending on the primary function of the cell type.
This allows for cells to specialize for a specific task.
[q] Deduce the function of the cell based on the structures present.
[a] This is a cell from a pancreas exocrine gland.
It has a lot of rough endoplasmic reticulum, so it can be deduced that the cell secretes a protein.
There are vesicles concentrated near one edge of the cell containing the protein that will be excreted.
[q] Deduce the function of the cell based on the structures present.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] These are cells from an aquatic leaf.
There are many chloroplast present, so it can be deduced that the cells do photosynthesis.
[q] Deduce the function of the cell based on the structures present.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] This cell is from the small intestine. It is an epithelial cell of a villus.
This cell has many microvilli which increase the surface area for nutrient absorption.
There are many vesicles (dark stain) containing materials brought into the cell via endocytosis.
[q] State the function of an exocrine gland cell in the pancreas.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] Exocrine gland cells synthesize molecules (often proteins) for secretion from the cell into an external space.
Exocrine gland cells of the pancreas secrete enzymes that function in digestion in the small intestine.
[q] Describe the function of the plasma membrane in an exocrine gland cell.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] Forms the boundary of the cell, acts as a selective barrier allowing certain materials to pass into and out of the cell.
[q] Describe the function of the nucleus in an exocrine gland cell.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] Contains most of the genes that control the eukaryotic cell, contains the nucleolus and chromatin.
[q] Describe the function of the mitochondria in an exocrine gland cell.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] The location of aerobic cellular respiration used to make ATP.
[q] Describe the function of the Golgi apparatus in an exocrine gland cell.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] Consists of flattened membranous sacs; receives transport vesicles from the ER, modifies proteins produced in the ER, produces secretory vesicles.
[q] Describe the function of the lysosomes in an exocrine gland cell.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] Contains digestive enzymes that are used to break apart cellular debris and waste.
[q] Describe the function of the vesicles in an exocrine gland cell.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] Transport materials within the cell and out of the cell via exocytosis.
[q] Describe the function of the endoplasmic reticulum in an exocrine gland cell.
Application: Structure and function of organelles within exocrine gland cells of the pancreas.
[a] Ribosomes on the ER synthesize proteins which are then moved through the ER and packaged into vesicles for transport.
[q] State the function of a palisade mesophyll cell of a leaf.
Application: Structure and function of organelles within palisade mesophyll cells of the leaf.
[a] Palisade mesophyll cells are found on the upper surface of a leaf and have the primary job of performing photosynthesis.
[q] Describe the function of the cell wall in a palisade mesophyll cell of a leaf.
Application: Structure and function of organelles within palisade mesophyll cells of the leaf.
[a] Provides structural rigidity and support.
[q] Describe the function of the plasma membrane in a palisade mesophyll cell of a leaf.
Describe the function of the plasma membrane in a palisade mesophyll cell of a leaf.
[a] Forms the boundary of the cell, acts as a selective barrier allowing certain materials to pass into and out of the cell.
[q] Describe the function of the chloroplast in a palisade mesophyll cell of a leaf.
Application: Structure and function of organelles within palisade mesophyll cells of the leaf.
[a] Location of photosynthesis reactions.
Produce carbohydrates using light energy, CO2 and H2O.
[q] Describe the function of the vacuole in a palisade mesophyll cell of a leaf.
Application: Structure and function of organelles within palisade mesophyll cells of the leaf.
[a] Membrane bound sacs, larger than vesicles, stores water and dissolved nutrients and helps maintain cell turgidity.
[q] Describe the function of the nucleus in a palisade mesophyll cell of a leaf.
Application: Structure and function of organelles within palisade mesophyll cells of the leaf.
[a] Contains most of the genes that control the eukaryotic cell, contains the nucleolus and chromatin.
[q] Describe the function of the mitochondria in a palisade mesophyll cell of a leaf.
Application: Structure and function of organelles within palisade mesophyll cells of the leaf.
[a] The location of aerobic cellular respiration used to make ATP.
[q] Identify the plasma membrane in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Look for a thin line around the edge of the cell.
[q] Identify the ribosomes in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Tiny dark dots, can be “free” in the cytoplasm or “bound” to the rough ER.
[q] Identify the nucleus in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Often stained a darker color, look for a nuclear membrane and the nucleolus.
[q] Identify the rough endoplasmic reticulum in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Look for stacks of lines, often with visible little dark dots attached.
Typically closer to the nucleus than Golgi.
[q]Identify the Golgi apparatus in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Look for stacks of lines, without little dark dots attached.
Typically further from the nucleus than ER.
[q] Identify the lysosome in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Little sacs, often a light grey color.
Hard to distinguish from vesicles.
[q] Identify the mitochondria in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Often stain dark. Circular or kidney shapes with internal wavy lines.
[q] Identify the chloroplast in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Typically an oval shape with stacks visible on the inside.
If image is in color, the chloroplasts will be green.
[q] Identify the vacuole in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Clear sac, typically larger in size than a vesicle or lysosome. More prevalent in plant cells than in animal cells.
[q] Identify vesicles in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Little roundish sacs. Often stain dark.
Can be hard to distinguish from lysosome.
[q] Identify the flagella in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Long tail-like structure emerging from the main cell body.
[q] Identify the cell wall in a micrograph of a eukaryotic cell.
Skill: Interpretations of electron micrographs to identify organelles and deduce the function of specialized cells.
[a] Rigid outermost layer of a plant cell, external to the cell membrane. Thicker than the cell membrane.
[x] Exit text
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E. Water: The Versatile Molecule
➢ In water, electrons are not shared equally in the bonds between hydrogen and oxygen
- Hydrogen atoms have a partial positive charge while oxygen atoms has a partial negative charge
■ Water is polar
➢ Hydrogen bonds
- Weak attractions that result of water’s polarity
■ Positive end of another polar molecule attracted to oxygen negative charge, and vice versa with the hydrogen end
■ Hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom
■ Weak Individually, but strong on a larger scale
- Lends watermany special properties
■ Cohesion
● Tendency for water to stick to water
● Important during transpiration - Water evaporates, pulls other water molecules with it, pulling all the way down from leaves to roots
■ Adhesion
● Tendency of water to stick to other substances
● $\text{Cohesion + Adhesion =}$ capillary action - Allows water to flow up roots/trunks/branches of trees in thin vessels
■ Surface tension
● Results from cohesion of water molecules
● Ex. water striders can sit on top of water without sinking
■ High heat capacity
● Heat Capacity=ability of a substance to resist temperature changes
● Keeps ocean temperatures stable
● Allows organisms to keep constant body temperature, since most life
forms are mostly made up of water
● Heat is absorbed when hydrogen bonds break, released when hydrogen bonds form
■ High heat of vaporization
● Heat a liquid must absorb for 1g to be converted to gas
● Evaporative cooling - As a liquid evaporates, its remaining surface cools
■ How sweat works to cool body down
■ Expansion on freezing
● Lattice structure of ice causes water to expand on freezing
● Allows ice to float on top of lakes in winter - Animal life can live beneath ice
■ Versatility as a solvent
● Solution is a liquid that is a homogenous mix of substances
● Solvent is the dissolving agent of a solution
● Solute is the substance that is dissolved
● Aqueous solution is one where water is the solvent
● Polarity of water allows it to be a versatile solvent - Can form hydrogen bonds easily
● Hydrophobic substances do not dissolve in water, but hydrophilic ones will
Syllabus for IBDP Biology First Assessment 2025
A. Unity and diversity
- 1. Molecules
- A1.1 Water
- A1.2 Nucleic acids
- 2. Cells
- A2.1 Origins of cells [HL only]
- A2.2 Cell structure
- A2.3 Viruses [HL only]
- 3. Organisms
- A3.1 Diversity of organisms
- A3.2 Classification and cladistics [HL only]
- 4. Ecosystems
- A4.1 Evolution and speciation
- A4.2 Conservation of biodiversity
B. Form and function
- 1. Molecules
- B1.1 Carbohydrates and lipids
- B1.2 Proteins
- 2. Cells
- B2.1 Membranes and membrane transport
- B2.2 Organelles and compartmentalization
- B2.3 Cell specialization
- 3. Organisms
- B3.1 Gas exchange
- B3.2 Transport
- B3.3 Muscle and motility [HL only]
- 4. Ecosystems
- B4.1 Adaptation to environment
- B4.2 Ecological niches
C. Interaction and interdependence
- 1. Molecules
- C1.1 Enzymes and metabolism
- C1.2 Cell respiration
- C1.3 Photosynthesis
- 2. Cells
- C2.1 Chemical signaling [HL only]
- C2.2 Neural signaling
- 3. Organisms
- C3.1 Integration of body systems
- C3.2 Defence against disease
- 4. Ecosystems
- C4.1 Populations and communities
- C4.2 Transfers of energy and matter
D. Continuity and change
- 1. Molecules
- D1.1 DNA replication
- D1.2 Protein synthesis
- D1.3 Mutations and gene editing
- 2. Cells
- D2.1 Cell and nuclear division
- D2.2 Gene expression [HL only]
- D2.3 Water potential
- 3. Organisms
- D3.1 Reproduction
- D3.2 Inheritance
- D3.3 Homeostasis
- 4. Ecosystems
- D4.1 Natural selection
- D4.2 Stability and change
- D4.3 Climate change
IB DP Biology HL Success Tips
Use IB DP Biology HL 2025 Revision Resources to religiously follow below steps to secure a 7
- Prepare Topic wise notes for IB DP Biology HL
- Practice Topical Exam Style Questions for All papers
- Update back your topical notes with new concepts learnt in topical questions
- Three Weeks before actual exam , go through Year wise past papers- Start with latest year and go back word
