Structure, Naming, Stereochemistry,
Acid-Base Chemistry, Titration,
Peptide Bond Formation and Hydrolysis
Primary and Secondary Protein Structure
Tertiary and quaternary Protein Structure
Denaturation
Enzymes as Biological Catalysts
Mechanisms of Enzyme Activity
Enzyme Kinetics
Effects of Local Conditions on Enzyme Activity
Regulation of Enzyme Activity
Cellular Functions
Biosignalling
Protein Isolation
Protein Analysis
Classification
Cyclic Sugar Molecules
Monosaccharides
Complex Carbohydrates
Structured Lipids
Signaling Lipids
Energy Storage
DNA Structure
Eukaryotic Chromosome Organization
DNA Replication
DNA Repair
Recombinant DNA and Biotechnology
The Genetic code
Transcription
Translation
Control of Gene Expression in Prokaryotes
Control of Gene Expression in Eukaryotes
Fluid Mosai Model
Membrane Components
Membrane Transport
Specialized Membranes
Glucose Transport
Glycolysis
Pyruvate Dehydrogenase
Glycogenesis and Glycogenolysis
Gluconeogenesis
The pentose phosphate pathway
Acetyl-CoA
Reactions of the citric Acid Cycle
The Electron Transport Chain
Oxidative Phosphorylation
Lipid Digestion and Absorption
Lipid Mobilization
Lipid Transport
Cholesterol Metabolism
Fatty Acids and Triacylglycerols
Ketone Bodies
Protein Catabolism
Thermodynamics and Bioenergetics
The Role of ATP
Biological Oxidation and REDUCTION
Metabolic States
Hormonal Regulation of Metabolism
Tissue Specific Metabolism
Integrative Metabolism
1.1 Structure of Water and hydrogen bonding 2 ENE
1.2 2 SYI elements of life
1.3 2 introduction to biological Macromolecules SYI
1.4 Properties of Biological Macromolecules 1 SYI
1.5 Structure and Function of Biological 6 Macromolecules IST
1.6 Nucleic Acids
~11-13 Class Periods 10-13% AP Exam Weighting
2.1 1 SYI cell structure: subcellular components
2.2 Cell Structure and Function 6 ENE
2.3 Cell Size 5 2 ENE
2.4 Plasma Membranes 2 ENE
2.5 Membrane Permeability 3 ENE
2.6 Membrane Transport 3 ENE
2.7 Facilitated Diffusion 6 ENE
2.8 Tonicity and Osmoregulation 4 ENE
2.9 Mechanisms of Transport 1 ENE
2.10 Cell Compartmentalization
2.11 origin of cell compartmentalization
~14-17 Class Periods Cell Communication and Cell Cycle UNIT 4 ~9-11 Class Periods Heredity UNIT 5 ~9-11 Class Periods IST
3.1 1 Enzyme structure
3.2 Enzyme Catalysis 3 ENE
3.3 Environmental Impacts on Enzyme Function 6 ENE
3.4 Cellular Energy 6 ENE
3.5 Photosynthesis 6 ENE
3.6 Cellular Respiration 4 SYI
3.7 Fitness
4.1 Cell Communication 1 IST
4.2 Introduction to Signal Transduction 1 IST
4.3 Signal Transduction 6 IST
4.4 6 ENE changes in signal transduction pathways
4.5 Feedback 6 IST
4.6 Cell Cycle 4 5 IST
4.7 Regulation of Cell Cycle 6 ENE
5.1 Meiosis 1 IST
5.2 Meiosis and Genetic Diversity 3 EVO
5.3 Mendelian Genetics IST 6 5 IST
5.4 5 SYI non-mendelian genetics
5.5 Environmental Effects on Phenotype 1 SYI
5.6 Chromosomal Inheritance 6 IST
~18-21 Class Periods
6.1 DNA and RNA Structure 1 IST
6.2 2 IST replication
6.3 Transcription and RNA Processing 2 IST
6.4 6 2 IST translation
6.5 Regulation of Gene Expression 6 IST
6.6 Gene Expression and Cell Specialization 6 IST
6.7 Mutations 2 3 IST 6
6.8 Biotechnology
~20-23 Class Periods
7.1 Introduction to Natural Selection 2 EVO
7.2 1 EVO natural selection
7.3 Artificial Selection 4 EVO
7.4 Population Genetics 3 EVO
7.5 5 hardy-weinberg Equilibrium 1 EVO
7.6 Evidence of Evolution 4 EVO
7.7 6 EVO common ancestry
7.8 Continuing Evolution 3 EVO
7.9 2 EVO phylogeny
7.10 6 2 EVO speciation
7.11 3 SYI extinction
7.12 Variations in Populations 6 SYI
7.13 3 IST origin of life on earth
~18-21 Class Periods ENE IST 3
8.1 Responses to the Environment ENE
8.2 6 SYI energy flow through ecosystems
8.3 Population Ecology 4 SYI
8.4 5 ENE effect of density of populations
8.5 Community Ecology 5 SYI
8.6 6 EVO biodiversity
8.7 Disruptions to SYI Ecosystems 5 EVO
Content overview Candidates for Cambridge International AS Level Biology study the following topics:
AS Level candidates also study practical skills. Candidates for Cambridge International
A Level Biology study the AS topics and the following topics:
An understanding of particle theory, including the structure of atoms and ions, and how they bond together to form compounds, helps to explain the properties of water and other substances important to marine life.
Learning outcomes Candidates should be able to:
1.1.1 explain the changes of state in water, between solid, liquid and gas, in terms of the kinetic particle theory
1.1.2 describe the structure of the atom, including the nucleus containing protons and neutrons, surrounded by electrons arranged in shells
1.1.3 understand that sea water is a mixture of different elements and compounds
1.1.4 describe (including through the use of diagrams) the covalent bonding in a water molecule, limited to the sharing of electron pairs between atoms
1.1.5 identify (including from diagrams) covalent molecules, including water, carbon dioxide, oxygen, sulfur dioxide and glucose
1.1.6 describe (including through the use of diagrams) the ionic bonding in sodium chloride, limited to the loss and gain of electrons to form ions and the subsequent attraction between positive and negative ions
1.1.7 identify (including from diagrams) ionic substances, including sodium chloride and calcium carbonate
1.1.8 state the chemical name and formula of salts found in sea water, including sodium chloride (NaCl), magnesium sulfate (MgSO4) and calcium carbonate (CaCO3)
1.1.9 explain the formation of hydrogen bonds in water
1.1.10 explain how hydrogen bonding in water affects the properties of water, limited to solvent action, density, and specific heat capacity
Sea water is a solution made up of many different solutes dissolved in water. Various environmental factors affect the solubility of salts and gases in sea water. Hydrogen ion concentration is particularly important, as this affects pH.
Learning outcomes Candidates should be able to: 1.2.1 explain the terms solute, solvent, solution and solubility 1.2.2 describe how soluble salts, such as sodium chloride, dissolve in water by the dissolution of ions 1.2.3 explain the effect of water temperature on the solubility of salts 1.2.4 define the term salinity as the concentration of dissolved salts in sea water (note that the unit for salinity used in this syllabus is parts per thousand (ppt)) 1.2.5 (PA) investigate the effect of salinity on the freezing point of water 1.2.6 explain the effect of surface run-off, precipitation and evaporation on the salinity of sea water 1.2.7 describe the pH scale as a measure of the hydrogen ion concentration in water, including the terms acidic, neutral and alkaline (calculations relating to hydrogen ion concentration are not required) 1.2.8 (PA) use litmus indicator, Universal Indicator and pH probes to measure the pH of water samples 1.2.9 state that oxygen has a low solubility in water 1.2.10 describe the effect of water temperature, water pressure (depth), atmospheric pressure and salinity on the solubility of gases in water and the implications this has for marine organisms (knowledge of the gas laws is not expected)
Density is a measure of the mass of a defined volume of water, and is affected by temperature, pressure and salinity. Density differences help to maintain temperature and salinity gradients in the oceans, which affect the distribution of organisms.
Learning outcomes Candidates should be able to: 1.3.1 explain how water temperature, water pressure and salinity affect the density of sea water 1.3.2 recall and apply the formula: density = mass ÷ volume, with units of kg m–3, kg and m3 respectively 1.3.3 state that the density of ice is lower than sea water, causing ice to float 1.3.4 explain the importance of ice floating, limited to its action as a thermal insulator and as a habitat for marine organisms 1.3.5 describe how temperature and salinity gradients form in water columns to produce ocean layers, including the surface layer, thermocline, halocline and deep ocean, and how subsequent mixing of these layers may occur
The movement of tectonic plates is responsible for the formation of many different features of the ocean floor, including hydrothermal vents and ocean trenches, and phenomena such as earthquakes and tsunamis.
Learning outcomes Candidates should be able to: 2.1.1 describe the structure of the Earth, limited to crust (oceanic and continental), mantle and core 2.1.2 describe and apply the theory of plate tectonics, and the evidence supporting the theory, limited to the geological matching of rock formations, distribution of similar fossils and living organisms, paleomagnetic stripes on the ocean floor and the jigsaw fit of the continental coastlines 2.1.3 identify and describe the three types of plate boundary as convergent, divergent and transform 2.1.4 explain how tectonic processes produce ocean trenches, midocean ridges, hydrothermal vents, abyssal plains, volcanoes, earthquakes and tsunamis 2.1.5 state that the water coming from hydrothermal vents is under pressure, hot and rich in dissolved nutrients and that this forms the hydrothermal vent plume 2.1.6 understand that the effects of the hydrothermal vent plume can be detected some distance from the hydrothermal vent site 2.1.7 explain how the chimneys form at hydrothermal vents, including reference to temperature and solubility of salts
Weathering of rocks results in the production of small fragments, which may be eroded (carried away) and deposited elsewhere as sediment. The balance between the rate at which sediments are eroded and deposited in the littoral zone determines the type of shore that forms.
Learning outcomes Candidates should be able to: 2.2.1 distinguish between weathering and erosion 2.2.2 describe the three main types of weathering: chemical, physical and organic, and be able to describe an example of each type 2.2.3 describe the four main types of erosion: by ice, water, wind and gravity 2.2.4 describe sedimentation as the deposition of suspended particles 2.2.5 understand how the speed of water flow and particle size affect the removal, transport and deposition of particles 2.2.6 define the littoral zone as the intertidal region on a shoreline, between the highest and lowest spring tide marks 2.2.7 state examples of the littoral zone, including rocky shores, sandy shores, muddy shores, estuaries and deltas 2.2.8 describe how weathering, erosion and sedimentation give rise to the morphology of rocky shores, sandy shores, muddy shores, estuaries and deltas
Twice each day, the level of the seas and oceans rises and falls, in a pattern determined by the alignment of Earth, Moon and Sun. The magnitude of these changes in level, known as tides, is also affected by environmental factors such as winds. Winds and temperature, along with other factors, also give rise to ocean currents. These currents ensure that the water in all the world’s oceans is able to mix, via the global ocean conveyor belt.
Learning outcomes Candidates should be able to: 2.3.1 explain how tides are produced, and how the alignment of the Earth, Moon and Sun, coastal geomorphology, wind, air pressure and size of water body affect the tidal range 2.3.2 explain the formation of spring and neap tides 2.3.3 interpret tide tables and graphs in terms of tidal height, tidal range, spring and neap tides 2.3.4 describe how wind, temperature, density, the Coriolis effect (limited to the deflection of currents clockwise in the northern hemisphere and anticlockwise in the southern hemisphere) and the shape of the sea bed produce ocean currents and upwelling 2.3.5 explain the formation of the global ocean conveyor belt and its importance in moving sea water around the Earth 2.3.6 discuss the causes and effects of El Niño and La Niña events during the El Niño Southern Oscillation (ENSO) cycle in the Pacific Ocean
Different species of organism may live in a close relationship with one another, which is known as symbiosis. Parasitism, commensalism and mutualism are types of symbiosis, differing from one another in the degree of benefit gained by the host and by the symbiont.
Learning outcomes Candidates should be able to: 3.1.1 describe the meaning of parasitism, commensalism and mutualism, and understand that they are all examples of symbiotic relationships 3.1.2 describe parasitic relationships, including the relationship between copepods and marine fish 3.1.3 describe commensal relationships, including the relationship between manta rays and remora fish 3.1.4 describe mutualistic relationships, including the relationship between boxer crabs and anemones
Producers harness an energy source – through either photosynthesis or chemosynthesis – to convert inorganic substances to organic substances, which contain energy that becomes available to consumers. The rate at which producers transfer energy into organic substances and produce biomass is measured as productivity, and this is affected by factors such as the availability of light. Energy is lost as it passes along a food chain, and this results in a decrease in the energy content of the organisms at each trophic level.
Learning outcomes Candidates should be able to: 3.2.1 explain the following terms in relation to feeding relationships: consumer (including primary, secondary, tertiary and quaternary), producer, herbivore, carnivore, omnivore, decomposer, predator, prey, food chain, food web, trophic level 3.2.2 represent and interpret feeding relationships in an ecosystem as food chains and food webs 3.2.3 understand that producers can be photosynthetic or chemosynthetic 3.2.4 explain that photosynthesis captures the energy of sunlight and makes some of the energy available to the food chain, and, it can be summarised by the word equation carbon dioxide + water light → chlorophyll glucose + oxygen (further details of photosynthesis and balanced chemical equations are not required at AS Level) 3.2.5 (PA) investigate the effect of light intensity on the rate of photosynthesis (use of fresh water plants is acceptable) 3.2.6 understand that some of the glucose produced by photosynthesis is used to produce biomass 3.2.7 understand that some of the glucose produced by photosynthesis is used in respiration to provide usable energy and can be summarised by the word equation glucose + oxygen → carbon dioxide + water (further details of respiration and balanced chemical equations are not required at AS Level) 3.2.8 define productivity as the rate of production of biomass per unit area or volume, and explain how high primary productivity may influence food chains 3.2.9 calculate and explain the energy losses along food chains 3.2.10 draw, describe and interpret pyramids of energy, numbers and biomass, including those that incorporate parasites and periods of plankton/algal bloom
Nutrients are materials that are required by organisms for an energy supply, and for growth and maintenance of body tissues. The availability of nutrients has a large effect on productivity, and therefore on the types and numbers of organisms that live in different parts of the oceans at different times.
Learning outcomes Candidates should be able to: 3.3.1 understand that nutrient is a generic term for substances that are required by an organism for growth, repair, energy or normal metabolism 3.3.2 understand that nutrients can include gases such CO2, ions such as Mg2+, CO3 2–, PO4 3– and NO3 – and organic compounds such as carbohydrates, lipids and proteins 3.3.3 state the chemical elements that make up carbohydrates, lipids and proteins 3.3.4 state that large molecules are made from smaller molecules, limited to starch and cellulose from glucose, proteins from amino acids, and lipids from fatty acids and glycerol 3.3.5 understand that some nutrients supply organisms with a source of essential elements and these elements have important biological roles: • nitrogen, which is used to make proteins, chlorophyll and DNA • carbon, which is used to make all organic compounds • magnesium, which is used to make chlorophyll • calcium, which is used to make bones, shells and coral skeletons • phosphorus, which is used to make DNA and bones 3.3.6 understand that some nutrients are soluble and that there is a reservoir of these nutrients dissolved in the ocean which is available to producers and consumers 3.3.7 explain the processes by which the reservoir of dissolved nutrients is replenished, including upwelling, run-off, tectonic activity, dissolving of atmospheric gases, excretion and decomposition 3.3.8 understand that the reservoir of dissolved nutrients is depleted by uptake into organisms 3.3.9 outline how marine snow transfers energy-containing organic material from surface waters to the deep ocean 3.3.10 understand that the nutrients taken up by organisms in food chains can be removed by harvesting 3.3.11 explain why productivity may be limited by the availability of dissolved nutrients 3.3.12 describe the carbon cycle, limited to combustion, photosynthesis, respiration, decomposition, formation of fossil fuels, formation and weathering of rocks containing carbonate
Organisms are classified in a hierarchical system, in which the largest group is the domain. Each type of organism belongs to a particular species, which is given a universally recognised two-word name called a binomial. Dichotomous keys are made up of pairs of contrasting descriptions, constructed so that the sequential choice of one of each pair leads to the name of the organism.
Learning outcomes Candidates should be able to: 4.1.1 describe the classification of species into the taxonomic hierarchy of domain, kingdom, phylum, class, order, family, genus and species 4.1.2 understand and use the binomial system of species nomenclature 4.1.3 construct and use simple dichotomous keys based on easily identifiable features 4.1.4 (PA) make observations and drawings from unfamiliar structures or specimens from the key groups in topic 4.2 and additionally Cnidaria in topic 5.2
The number of phyla living in the oceans is considerably greater than on land. The adults and larvae of many different types of organism are planktonic, drifting in ocean currents. Crustaceans, echinoderms, bony fish and cartilaginous fish are some of the more obvious animals in the oceans, while macroalgae (seaweeds) and seagrasses form the basis of many food chains.
Learning outcomes Candidates should be able to: 4.2.1 define plankton as a diverse collection of generally microscopic organisms that have limited motility and drift in water currents 4.2.2 understand that phytoplankton are producers which absorb nutrients from their environment (like all producers) and obtain their nutrition by photosynthesis; examples include microscopic algae such as diatoms and dinoflagellates 4.2.3 understand that zooplankton are consumers; examples include larvae, copepods and larger animals such as jellyfish 4.2.4 state the main features of a typical adult echinoderm, limited to pentaradial symmetry and tube feet 4.2.5 understand the ecological and economic importance of echinoderms, including the crown of thorns starfish 4.2.6 state the main features of a typical adult crustacean, including carapace, segmented abdomen, jointed legs and two pairs of antennae 4.2.7 understand the ecological and economic importance of crustaceans, including Antarctic krill 4.2.8 state the main internal and external features of a typical adult bony fish, including bony skeleton, operculum, gills, swim bladder, scales, externally visible lateral line, fins (pectoral, caudal, pelvic, anal and dorsal) 4.2.9 understand the ecological and economic importance of bony fish, including the Peruvian anchoveta 4.2.10 state the main internal and external features of a typical adult cartilaginous fish, including cartilaginous skeleton, gill slits, gills, denticles, lateral line, fins (pectoral, caudal, pelvic, anal and dorsal)
4.2.11 understand the ecological and economic importance of cartilaginous fish, including the blue shark 4.2.12 understand that bony fish and cartilaginous fish are both chordates (i.e. in the Phylum Chordata) and that all organisms in this phylum share common features (at some point in their development), including notochord, dorsal neural tube, pharyngeal slits and post-anal tail 4.2.13 state the main features of a typical macroalga, such as kelp, including holdfast, stipe, gas bladders and blades 4.2.14 understand the ecological and economic importance of macroalgae, including kelp 4.2.15 state the main features of a typical marine plant, such as seagrass, including rhizome, roots, flowers and leaves 4.2.16 understand the ecological and economic importance of marine plants, including seagrass
Biodiversity is a measure of the range of different species and ecosystems, as well as the genetic diversity within a species. High biodiversity tends to be linked to stability in ecosystems on both small and large scales.
Learning outcomes Candidates should be able to: 4.3.1 explain that biodiversity can be considered at three different levels: • genetic diversity (variation in the genes of a species) • species diversity (number of species and their relative abundance) • ecological diversity (variation in ecosystems on a regional and global level) 4.3.2 understand the importance of marine biodiversity in terms of the services /benefits it provides, including: • maintaining stable ecosystems (for example, diversity in communities maintains complex interactions between all organisms and the physical environment) • protection of the physical environment (for example, coral reefs protect coastlines) • climate control (for example, phytoplankton absorb CO2 and release O2) • providing food sources (for example, algae, crustaceans and fish) • providing a source of medicines (for example, anticancer drugs such as keyhole limpet hemocyanin (KLH))
Biotic and abiotic factors affect the distribution and abundance of different types of organism in the marine environment. It is important to select appropriate techniques to study distribution and abundance in particular circumstances – for example, whether sampling should be random or systematic. The data collected can be analysed to look for correlations between abundance and a particular environmental factor.
Learning outcomes Candidates should be able to: 4.4.1 explain, using marine examples, the terms ecosystem, habitat, niche, species, population and community 4.4.2 explain the terms biotic factor (including intra- and inter-specific competition, symbioses, predation and disease) and abiotic factor (including salinity, temperature, pH, oxygen concentration, carbon dioxide concentration, light availability, turbidity, wave/tide action, nutrient availability and exposure to air) and identify those factors that affect an organism in a named marine ecosystem 4.4.3 understand the mark-release-recapture method for estimating population size of a named species 4.4.4 apply the Lincoln index and identify the limitations of this method (the equation and symbols for the Lincoln index will be provided in the question papers) N m n n 2 1 2 # = N = estimate of population size n1 = number of individuals captured in first sample n2 = number of individuals (both marked and unmarked) captured in second sample m2 = number of marked individuals recaptured in second sample 4.4.5 describe random and systematic sampling and understand their advantages and disadvantages 4.4.6 (PA) use suitable methods, including frame quadrats, line transects, belt transects and mark-release-recapture, to investigate the distribution and abundance of organisms in the littoral zone (note that candidates should be taught the importance of designing an ethical and safe method)
4.4.7 use Simpson’s index of diversity (D) to calculate the species diversity of a habitat and interpret different values of D (the equation and symbols for the calculation of D will be provided in the question papers) D N n 1 2 = -e/c m o Σ = sum of (total) n = number of individuals of each different species N = the total number of individuals of all the species 4.4.8 use Spearman’s rank correlation (rs) to analyse the relationships between the distribution and abundance of species and abiotic or biotic factors (the equation and symbols for the calculation of rs will be provided in the question papers) r n n D 1 6 s 3 2 # = - - e o / Σ = sum of (total) n = number of pairs of items in the sample D = difference in rank between each pair of measurements (candidates should understand that correlations exist between –1 (perfect negative correlation), 0 (no correlation) and +1 (perfect positive correlation), and, that a correlation does not necessarily imply a causal relationship)
Depth zones in the oceans range from the surface layers to the very deepest parts in the benthic zones. The oceans have considerable influence on global climate and on the composition of the atmosphere, with which they continually interact.
Learning outcomes Candidates should be able to: 5.1.1 identify the world’s five oceans as the Arctic, Atlantic, Pacific, Indian and Southern, and understand that these oceans are inter-connected and encircle the Earth as a World Ocean 5.1.2 identify zones found in the open ocean, limited to epipelagic, mesopelagic, bathypelagic, abyssopelagic and benthic zones, and describe these zones in terms of light penetration 5.1.3 explain the importance of oceans and their interaction with the atmosphere: • as carbon sinks • as sources of oxygen • in temperature buffering • in global climate control 5.1.4 identify regions of the oceans as polar, temperate, or tropical
Tropical coral reefs are built by tiny coral polyps, which live in close association with photosynthetic zooxanthellae and are therefore limited in their distribution to areas where abundant light is available and temperatures are warm. The polyps themselves are consumers and require a source of small organisms that they can capture and digest. Changes to biotic or abiotic factors in the oceans can lead to the erosion of coral reefs. Artificial structures can be provided as a substrate on which reef communities can develop.
Learning outcomes Candidates should be able to: 5.2.1 describe the conditions required for tropical coral reef formation 5.2.2 describe and compare the four types of tropical coral reef: fringing, barrier, patch and atoll, in terms of their proximity to the coast and lagoon structure (if present) 5.2.3 describe corals as animals in the Phylum Cnidaria that form sessile colonies of polyps, often having a symbiotic relationship with zooxanthellae 5.2.4 understand that there are two general types of coral, hard (for example, staghorn) and soft (for example, sea fan) which are characterised by the extent of calcification and the presence of zooxanthellae 5.2.5 describe the structure of a typical coral polyp, limited to tentacle, nematocyst, mouth, stomach, calyx, theca and basal plate, and describe the functions of these structures 5.2.6 explain how corals obtain their nutrition, including the mutualistic relationship between the polyps of some corals and zooxanthellae 5.2.7 discuss the importance of coral reefs, including tourism, food source, coastal protection, medicines and biodiversity 5.2.8 discuss the causes and effects of reef erosion, including pH change, temperature change, predation, physical damage and the presence of sediment 5.2.9 discuss the use of artificial reefs
Organisms living on rocky shores experience variations in temperature and salinity, availability of water and exposure to sunlight at different stages of the tidal cycle. High on the shore, these abiotic factors are the main influence on the distribution and abundance of species, but lower down the shore biotic factors such as competition and predation have the greatest influence.
Learning outcomes Candidates should be able to: 5.3.1 identify the different zones on a typical exposed rocky shore, limited to splash zone, upper shore, middle shore and lower shore, and describe the changing abiotic factors across these zones during one tidal cycle 5.3.2 explain how biotic and abiotic factors interact to affect the distribution and abundance of organisms in the different zones on the rocky shore (candidates should study a range of named organisms from the different zones) 5.3.3 explain, using named examples, the adaptations that organisms have to living in the different zones
Organisms cannot attach securely to the unstable substrate on sandy shores. The variations in abiotic factors through the tidal cycle can be even greater than on a rocky shore, and relatively few types of organism have adaptations – such as the ability to burrow – that enable them to live there.
Learning outcomes Candidates should be able to: 5.4.1 describe the sandy shore as an ecosystem with an unstable, shifting substrate that is porous 5.4.2 explain how the biotic and abiotic factors that affect a sandy shore lead to a relatively low biodiversity 5.4.3 (PA) investigate the effect of particle size on the permeability of substrates 5.4.4 explain, using named examples, the adaptations that organisms have to living on a sandy shore
Mangroves have adaptations for surviving in environments where they are partly submerged in salt water. They grow on muddy shores in tropical and subtropical regions, and have a major influence on biodiversity. They are of great value to human coastal communities, although many human activities pose serious threats to mangrove forests.
Learning outcomes Candidates should be able to: 5.5.1 describe the mangrove forest as a tidal ecosystem featuring salt tolerant trees and other plants, together with populations of other species, all interacting in the littoral zone of some tropical and subtropical coasts 5.5.2 outline the conditions required for the formation of mangrove forest 5.5.3 explain how the red mangrove tree, Rhizophora mangle, is adapted to the mangrove environment, including: • prop roots for stability in unstable substrates and supplementary oxygen uptake due to low oxygen concentrations in the substrate • salt exclusion by the roots • viviparous reproduction using propagules 5.5.4 explain the ecological importance of mangrove forests in terms of: • nursery area for juveniles of many animal species • sediment trapping which stabilises and protects the coastline and prevents sediment build up on coral reefs and seagrass beds 5.5.5 discuss the importance of mangrove forests, including tourism, food source, coastal protection, timber, fuel source and biodiversity 5.5.6 discuss the threats to mangrove forests, including temperature change, over-harvesting, storm damage and change in coastal land use
All living organisms are formed of units called cells, which have many features in common. Each cell is separated from its immediate environment by the cell surface membrane, and contains genetic material and organelles within the cytoplasm. An understanding of the structure of the cell surface membrane enables us to understand its functions. We use microscopes to visualise cells. The images produced can be studied and interpreted to increase understanding of cell structure.
Learning outcomes Candidates should be able to: 6.1.1 recognise the following organelles and other cell structures and outline their functions: • cell surface membrane • nucleus • rough and smooth endoplasmic reticulum • ribosomes • Golgi body • mitochondria • chloroplasts • cell wall • large permanent vacuole 6.1.2 describe the fluid mosaic model of membrane structure, including an outline of the structure and functions of phospholipids and proteins, limited to carrier and channel proteins 6.1.3 understand the selectively permeable nature of membranes and relate this to the transport (active and passive) of substances across a membrane 6.1.4 describe and interpret photomicrographs, electron micrographs and drawings of typical animal and plant cells 6.1.5 recall and apply the formula: magnification = image size ÷ actual size 6.1.6 (PA) make observations, drawings and magnification calculations from unfamiliar structures or specimens (taken from any of the key groups in topic 4.2, topic 5.2 or the cell structures in Learning outcome 6.1.1)
Diffusion and facilitated diffusion across cell membranes are passive processes. Osmosis is a particular type of diffusion involving water. Active transport however uses energy provided by the cell to move substances against their concentration gradient. Water potential is a measure of the relative number of water molecules, and their freedom to move, in a solution. Water diffuses down a water potential gradient and can move freely through cell membranes.
Learning outcomes Candidates should be able to: 6.2.1 describe and explain the processes of diffusion, facilitated diffusion, osmosis and active transport 6.2.2 understand the concept of water potential and explain how dissolved solutes affect the water potential of a solution or cell (knowledge of solute potential is not required) 6.2.3 (PA) investigate diffusion and osmosis using plant tissue and non-living materials, such as Visking tubing and agar 6.2.4 calculate surface areas and volumes of simple shapes (all formulae and relevant symbols will be provided) to illustrate the principle that surface area to volume ratio decreases with increasing size 6.2.5 (PA) investigate the effect of changing surface area to volume ratio on diffusion using agar blocks of different sizes 6.2.6 (PA) investigate the effects of immersing plant tissues in solutions of different water potentials, using the results to estimate the water potential of the tissues 6.2.7 explain the movement of water between cells and solutions with different water potentials and explain the different effects on plant and animal cells
Aerobic respiration requires oxygen and produces carbon dioxide. These two gases diffuse into and out of the organism, from and to its environment. This process is called gas exchange. Smaller marine organisms often allow the gases to diffuse across their whole body surface, but most larger organisms have specialised surfaces across which gas exchange takes place. They may also have methods of ventilating these surfaces.
Learning outcomes Candidates should be able to: 6.3.1 understand that the raw materials and waste products of respiration must be moved to and from the surface of organisms 6.3.2 discuss how surface area to volume ratio is dependent on the size and shape of an organism, and relate this to the need for specialised gaseous exchange surfaces and transport systems in larger animals 6.3.3 describe gaseous exchange by simple diffusion, pumped ventilation and ram ventilation, in examples including coral polyps, grouper and tuna 6.3.4 relate an organism’s method of gas exchange to its habitat and motility
Sea water has a similar water potential to the body fluids of most marine organisms, and therefore many species do not need to regulate their water content. Other species are osmoregulators and control the water content of their bodies. Most marine organisms can survive within only a small range of salinity, and are termed stenohaline. Euryhaline species can live in a range of salinities. Salmon are an example of a euryhaline osmoregulator, spending part of their life cycle in the sea and part in fresh water.
Learning outcomes Candidates should be able to: 6.4.1 explain why marine organisms may need to regulate their water content and ion content, with reference to the composition of sea water and of body fluids 6.4.2 explain the terms osmoconformer and osmoregulator with reference to marine mussels and tuna 6.4.3 explain the terms euryhaline and stenohaline with reference to salmon, marine mussels and tuna 6.4.4 outline the processes of osmoregulation in e.g., salmon
Photosynthesis is a two-stage process in which energy is harvested from light by pigments, and then transferred to organic compounds. These compounds can be used to synthesise biomass or to provide useful energy for life processes. Photosynthesis takes place in chloroplasts, whose structure enables these stages to take place efficiently. If a requirement for photosynthesis is in short supply, it may act as a limiting factor, preventing the rate of photosynthesis from increasing.
Learning outcomes Candidates should be able to: 7.1.1 understand that white light is composed of a range of colours, each with a different wavelength 7.1.2 differentiate between the terms wavelength, intensity and penetration in the context of light 7.1.3 describe the effect of wavelength on the penetration of light to different depths 7.1.4 understand that photosynthesis is the process that nearly all marine producers use to fix carbon, and it can be summarised as: 6CO2 + 6H2O light → chlorophyll C6H12O6 + 6O2 7.1.5 understand that photosynthesis is a two-stage process, light-dependent and light-independent 7.1.6 explain that energy is transferred as ATP and reduced NADP from the light-dependent stage to the light-independent stage (Calvin cycle) and is used to produce organic molecules 7.1.7 describe the structures in a typical chloroplast, to include outer membrane, inner membrane, stroma, thylakoids, thylakoid membrane, thylakoid space and grana 7.1.8 state the sites of the light-dependent and the light-independent stages in the chloroplast 7.1.9 describe the role of chloroplast pigments (chlorophyll a and accessory pigments) in light absorption in the grana 7.1.10 relate the presence of accessory pigments, including xanthophylls and phycobilins, in marine producers to the penetration of different wavelengths of light 7.1.11 (PA) describe and use chromatography to separate and identify chloroplast pigments (reference should be made to Rf values) 7.1.12 interpret absorption spectra of chloroplast pigments and action spectra for photosynthesis 7.1.13 describe the light-dependent stage as the photoactivation of chlorophyll resulting in the photolysis of water and the transfer of energy to ATP and reduced NADP (details of cyclic and non-cyclic photophosphorylation are not required) 7.1.14 describe the light-independent stage (Calvin cycle) as the fixation of carbon dioxide using the enzyme rubisco and the ATP and reduced NADP formed during the light-dependent stage (details of intermediate compounds are not required) 7.1.15 describe and explain the effect of limiting factors of photosynthesis, including light intensity, wavelength of light, carbon dioxide concentration and temperature on the rate of photosynthesis 7.1.16 (PA) investigate the effect of wavelength of light on the rate of photosynthesis (use of fresh water plants is acceptable)
Hydrothermal vents provide a habitat for a very unusual community of living organisms adapted to the unique conditions found there. As there is no light, bacteria use energy from inorganic chemicals to produce organic substances. This forms the basis of the food web. The bacteria live in symbiosis with tubeworms.
Learning outcomes Candidates should be able to: 7.2.1 describe chemosynthesis as the fixation of carbon using the chemical energy of dissolved substances; these substances include hydrogen sulfide, methane, hydrogen and iron 7.2.2 understand that chemosynthetic bacteria at hydrothermal vents fix the energy into a form that other organisms can use, which allows the formation of a food chain 7.2.3 describe the symbiotic relationship between the giant tubeworm, Riftia, found at hydrothermal vents, and the chemosynthetic bacteria Endoriftia 7.2.4 explain that Endoriftia uses the energy from hydrogen sulfide to fix carbon thereby producing organic compounds such as glucose (word and chemical equations are not required)
Organisms require constant supplies of energy to maintain life processes. Respiration releases energy from organic nutrients in a usable form, as ATP.
Learning outcomes Candidates should be able to: 7.3.1 understand that aerobic respiration is the process that organisms use to release the energy they require in the form of ATP when oxygen is available 7.3.2 represent aerobic respiration using word and chemical equations glucose + oxygen → carbon dioxide + water C6H12O6 + 6O2 → 6CO2 + 6H2O 7.3.3 understand that in conditions where oxygen is limited or unavailable, most organisms also use anaerobic respiration which yields far less ATP per molecule of glucose (word and chemical equations are not required) 7.3.4 describe the structure of a mitochondrion, including matrix, outer membrane and inner membrane forming cristae 7.3.5 state the sites of aerobic respiration and anaerobic respiration in a cell
Many species of marine organisms have complex life cycles with several different stages, in which one or more stages are adapted for dispersal. Marine mammals have simpler life cycles. The female gametes of most invertebrates, and some vertebrates such as bony fish, are fertilised outside the body of the female, but fertilisation is internal in mammals and sharks.
Learning outcomes Candidates should be able to: 8.1.1 describe metamorphosis, larval stage, sessile and non-sessile with reference to life cycles of marine animals 8.1.2 describe the differences between simple and complex life cycles, to include marine mammals (simple) and crustaceans (complex), relating to the presence or absence of a larval stage and metamorphosis 8.1.3 outline the importance of different stages in the life cycle of sessile and non-sessile organisms 8.1.4 discuss the advantages and disadvantages of internal and external fertilisation, and subsequent investment in the care of offspring, with reference to tuna, sharks and whales
Modern fishing methods can harvest so many fish that there is a danger that fish populations may be reduced beyond the point at which they can recover. Sustainable exploitation can be achieved by collecting information about fish stocks, regulating fishing and rehabilitating depleted stocks.
Learning outcomes Candidates should be able to: 8.2.1 explain the need for the sustainable exploitation of fisheries, with reference to a named marine organism 8.2.2 discuss the impact of modern fishing technology, including sonar, purse seine fishing, benthic trawling and factory ships, on populations and habitats 8.2.3 describe the principal information needed to decide how best to exploit fisheries on a sustainable basis, limited to recruitment, growth, natural mortality, fishing mortality, age of reproductive maturity, fecundity and dependency on particular habitats 8.2.4 outline the principal tools used to ensure that fisheries are exploited on a sustainable basis, including: • restriction by season • restriction by quotas • restriction by licensing • restriction of location, including refuge zones, no-take zones and marine protected areas (MPAs) • restriction of method, including minimum mesh sizes and the compulsory use of rod-and-line • restrictions on the size of organism that can be retained • restriction of fishing intensity, including restrictions on the number of boats, boat and engine size, and the amount of fishing gear (for example, maximum net size, maximum number of traps) • monitoring, including air and sea patrols, satellite tracking, inspection of catch and fishing gear • imposition of fines, confiscation of boats and gear, imprisonment • consumer-orientated tools, including labelling, publicity campaigns and price tariffs 8.2.5 discuss the advantages and disadvantages of the tools in 8.2.4, to include their effectiveness and impact on non-target species 8.2.6 discuss the long-term and short-term sociological and economic impacts of, restrictions on fishing and of unrestricted fishing 8.2.7 discuss the advantages and disadvantages of strategies for the rehabilitation of depleted stocks, including replanting mangroves, building artificial reefs and introducing cultivated stock to the wild
Increasingly, marine organisms are grown in controlled systems, as an alternative to harvesting from the wild. Aquaculture systems may be intensive or extensive, and both types can have a range of positive and negative social, economic and environmental impacts that should be considered when developing an aquaculture project.
Learning outcomes Candidates should be able to: 8.3.1 describe intensive and extensive aquaculture techniques, with reference to named marine organisms 8.3.2 outline the process of aquaculture including in salmon, marine mussels and shrimp 8.3.3 explain the requirements for the long-term success of aquaculture projects, limited to availability of stock, availability of clean water, availability of feed, efficiency of use of feed, availability of labour, disease management, availability of location, market demand, access to market and return on investment 8.3.4 discuss the principal impacts of aquaculture, limited to habitat destruction, overexploitation of feedstocks, pollution, escape of cultured stock, introduction of (potentially) invasive species, spread of disease, competition for resources, reduction in the exploitation of native stocks, social impacts and economic impacts
Human activities, whether taking place on land or at sea, frequently affect marine ecosystems. Oil spills, runoff from terrestrial industries and agriculture, and the use and disposal of plastics, have become serious issues, with potentially very significant and widespread effects. Bioaccumulation of heavy metals and other toxins can also have considerable negative impacts.
Learning outcomes Candidates should be able to: 9.1.1 explain the impacts on marine water quality, habitats, organisms and food webs of: • the oil industry • agriculture • renewable energy installations • sewage disposal • refuse disposal • desalination plants • fishing practices (including dredging and blast fishing) 9.1.2 explain the bioaccumulation of toxins and their biomagnification along food chains, including heavy metals in antifouling paint and mercury from the combustion of fossil fuels 9.1.3 understand that microplastics are plastic particles with a diameter of less than 5mm and that there are two broad categories; primary microplastics and secondary microplastics 9.1.4 describe how most plastics do not biodegrade but can be broken down to form secondary microplastic fragments, through the action of UV radiation, wind action and wave action, and how temperature affects this process 9.1.5 discuss the impacts of plastics and microplastics on the marine ecosystem, including: • uptake of microplastics by plankton • transfer of microplastics along the food chain • absorption of toxic compounds and their release after being taken up • ingestion of plastics by marine organisms • risk to humans if plastics or toxins enter the human food chain • entanglement (for example, ghost fishing nets) 9.1.6 discuss strategies to limit the release of plastics and microplastics into the marine ecosystem
The Earth’s atmosphere naturally contains carbon dioxide, which produces the greenhouse effect, helping to maintain a temperature on Earth that is suitable for life. However, increasing quantities of carbon dioxide, resulting at least partially from human activities, are enhancing the greenhouse effect and causing global warming. Global warming is already producing a range of negative impacts on the marine environment.
Learning outcomes Candidates should be able to: 9.2.1 describe how the natural greenhouse effect creates the Earth’s ambient temperature 9.2.2 explain how the enhanced greenhouse effect leads to global warming 9.2.3 describe the evidence for global warming 9.2.4 discuss and evaluate the evidence for and against the hypothesis that human activity significantly contributes to global warming 9.2.5 describe the possible impacts of global warming on the marine environment, including sea level rise, coral bleaching, changes in the distribution of species and potential changes to the global circulation of sea water
Carbon dioxide dissolves in sea water to form a weak acid, and increasing concentrations of atmospheric carbon dioxide therefore lead to a decrease in the pH of sea water. This has damaging effects on many marine organisms, particularly those such as corals and molluscs whose skeletons and shells contain calcium carbonate.
Learning outcomes Candidates should be able to: 9.3.1 explain the relationships between atmospheric carbon dioxide, dissolved carbon dioxide and acidity in the ocean, and understand how the oceans help to limit the increase in atmospheric carbon dioxide concentrations 9.3.2 describe how carbon dioxide reacts with water to form hydrogen ions and hydrogen carbonate ions, and, the impact this has on pH and carbonate ion availability 9.3.3 describe the impact of 9.3.2 on hard corals and shelled organisms 9.3.4 (PA) investigate the effect of pH on the loss of mass of empty mollusc shells
Local, regional and global conservation efforts can go some way to reducing and even reversing harmful effects on marine ecosystems, but their implementation can sometimes be difficult and expensive.
Learning outcomes Candidates should be able to: 9.4.1 understand the need for conservation in terms of maintaining or enhancing biodiversity 9.4.2 understand how the International Union for Conservation of Nature (IUCN) Red List can assist in prioritising decisions on local, regional and global marine conservation projects 9.4.3 explain the meaning of the terms invasive species and endangered species, as defined by the IUCN 9.4.4 understand why invasive species pose a threat to native marine species and ecosystems 9.4.5 evaluate the viability of potential conservation projects from given information 9.4.6 discuss strategies for conserving marine species, including: • MPAs and no-take zones • captive breeding and release programmes • legislation both locally and globally, including CITES and IWC moratorium • UNESCO biosphere reserves • the role of marine zoos and aquaria • ecotourism • control of invasive species 9.4.7 understand that due to the scale of many marine ecosystems, international cooperation and legislation is necessary, but not always possible (for example, non-universal sign-up to IWC moratorium or CITES), and the implications of this for conservation
Core
1. Cell biology
2. Molecular biology
3. Genetics
4. Ecology
5. Evolution and biodiversity
6. Human physiology 95 15 21 15 12 12 20 Additional higher level
7. Nucleic acids
8. Metabolism, cell respiration and photosynthesis
9. Plant biology
10.Genetics and evolution
11.Animal physiology
Option (Choice of one out of four) A. Neurobiology and behaviour B. Biotechnology and bioinformatics C. Ecology and conservation D. Human physiology
Unity and diversity • Water • Nucleic acids • Origins of cells * • Cell structure • Viruses * • Diversity of organisms • Classification and cladistics * • Evolution and speciation • Conservation of biodiversity
Form and function • Carbohydrates and lipids • Proteins • Membranes and membrane transport • Organelles and compartmentalization • Cell specialization • Gas exchange • Transport • Muscle and motility * • Adaptation to environment • Ecological niches 26 39
Interaction and interdependance • Enzymes and metabolism • Cell respiration • Photosynthesis • Chemical signalling * • Neural signalling • Integration of body systems • Defence against disease • Populations and communities • Transfer of energy and matter 31 48
Continuity and change • DNA replication • Protein synthesis • Mutations and gene editing • Cell and nuclear division • Gene expression * • Water potential • Reproduction • Inheritance • Homeostasis • Natural selection • Sustainability and change • Climate change