A cellulose cell wall
Spiegazione
Plant cells contain a cellulose cell wall, whereas animal cells have a cell membrane but lack a cellulose cell wall. Chloroplasts and a sap vacuole are also plant-cell structures.
It contains circular DNA and may contain plasmids
Spiegazione
Bacterial cells contain circular DNA and may contain plasmids. Unlike plant and animal cells, they do not have a nucleus surrounded by a membrane.
Its structure is related to its specific function
Spiegazione
A specialised cell has a structure adapted or related to the specific function it performs. Size, genetic material, and independence do not define specialisation.
400×
Spiegazione
Magnification is calculated as image size divided by actual size: 12 ÷ 0.03 = 400. Therefore, the magnification is 400×.
A group of organisms that can produce fertile offspring
Spiegazione
A species is a group of organisms capable of reproducing to produce fertile offspring. Similar appearance, habitat, or naming does not by itself define a species.
Its genus and species
Spiegazione
The binomial system gives each organism a two-part scientific name consisting of its genus and species. A common name does not follow this required structure.
By guiding the user through successive choices based on observable features
Spiegazione
A dichotomous key directs the user through a series of choices about identifiable features until the organism is identified. It does not require DNA comparison or rely on one feature alone.
Animal, Plant, Fungus, Prokaryote and Protoctist
Spiegazione
The five kingdoms are Animal, Plant, Fungus, Prokaryote, and Protoctist. The other lists contain vertebrate or arthropod groups, or include categories that are not part of this five-kingdom list.
Net movement of particles from higher to lower concentration
Spiegazione
Diffusion is the net movement of molecules or ions down a concentration gradient, from higher to lower concentration, caused by random movement. Movement against the gradient using energy is active transport.
Water moves from higher to lower water potential through a partially permeable membrane
Spiegazione
Osmosis is the net movement of water molecules from higher water potential to lower water potential through a partially permeable membrane. It specifically involves water and does not require respiratory energy.
It may become turgid, flaccid or plasmolysed
Spiegazione
Depending on the surrounding solution, osmosis can cause plant tissue to become turgid, flaccid, or plasmolysed. The outcome depends on the relative water potentials.
From lower to higher concentration using energy released during respiration
Spiegazione
Active transport moves molecules or ions against the concentration gradient, from lower to higher concentration, using energy released during respiration. Diffusion does not require this energy and moves down the gradient.
Nitrogen only
Spiegazione
Proteins contain carbon, hydrogen, oxygen, and nitrogen, whereas carbohydrates and lipids contain carbon, hydrogen, and oxygen. DNA also contains phosphorus, but proteins do not.
Amino acids for proteins and fatty acids plus glycerol for lipids
Spiegazione
Proteins are made from amino acids, while lipids are made from fatty acids and glycerol. These substances have different molecular building blocks.
Benedict’s solution
Spiegazione
Benedict’s solution is used to test for glucose and maltose. Iodine solution tests for starch, biuret reagent tests for protein, and the ethanol emulsion test detects lipids.
A protein that acts as a biological catalyst
Spiegazione
An enzyme is a protein that functions as a biological catalyst in metabolic reactions. It is not primarily a storage molecule, membrane lipid, or genetic-information molecule.
To make carbohydrates from raw materials using light energy
Spiegazione
Photosynthesis uses light energy to make carbohydrates from raw materials. Breaking down glucose to release energy is associated with respiration.
It transfers light energy into chemical energy
Spiegazione
Chlorophyll is a green pigment in chloroplasts that transfers light energy into chemical energy used to form glucose and other carbohydrates. Chloroplasts are the organelles that contain chlorophyll.
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Spiegazione
Photosynthesis combines six molecules of carbon dioxide with six molecules of water to form glucose and six molecules of oxygen, in the presence of light and chlorophyll.
The concentration of carbon dioxide
Spiegazione
The limiting factor is the environmental factor in shortest supply. In this situation, the low carbon dioxide concentration limits the rate of photosynthesis.
Root hair cells, root cortex cells, xylem, mesophyll cells
Spiegazione
Water passes from root hair cells through root cortex cells, then travels in the xylem before reaching mesophyll cells. Root hair cells absorb water, whereas xylem transports it through the plant.
The loss of water vapour from leaves
Spiegazione
Transpiration is the loss of water vapour from leaves. The movement of sucrose and amino acids through phloem is called translocation.
It evaporates from mesophyll surfaces and diffuses out through stomata
Spiegazione
Water evaporates from mesophyll-cell surfaces into internal air spaces and then diffuses out through stomata as water vapour. This process produces transpiration.
Transpiration pull acting on a continuous water column
Spiegazione
Transpiration pull draws water upwards through xylem. The continuous column is maintained by attraction between water molecules.
Physical digestion changes particle size, whereas chemical digestion changes large molecules into smaller ones
Spiegazione
Physical digestion breaks food into smaller pieces without changing its molecules. Chemical digestion breaks large molecules into smaller molecules.
Amylase converts starch into maltose
Spiegazione
Amylase breaks starch down into maltose. Maltase then converts maltose into glucose, while protease and lipase act on proteins and lipids respectively.
A diet supplying principal dietary components in appropriate amounts for health
Spiegazione
A balanced diet supplies the principal dietary components in appropriate amounts to maintain health.
It has a large area, a thin surface, and a good blood and air supply
Spiegazione
Efficient gas exchange is supported by the alveoli’s large surface area, thin exchange surface, and good blood and air supply.
The brain and spinal cord
Spiegazione
The central nervous system consists of the brain and spinal cord. Nerves outside these structures belong to the peripheral nervous system.
Receptor, sensory neurone, relay neurone, motor neurone, effector
Spiegazione
A simple reflex arc carries impulses from a receptor through a sensory neurone and relay neurone, then through a motor neurone to an effector.
Neurotransmitters are released, diffuse across the gap, and bind to receptors on the next neurone
Spiegazione
An arriving impulse causes vesicles to release neurotransmitters. These diffuse across the synaptic gap and bind to receptor proteins on the next neurone, stimulating an impulse.
A chemical made by a gland and carried in the blood to alter specific target organs
Spiegazione
A hormone is a chemical substance produced by a gland and transported in the blood to alter the activity of one or more specific target organs.
Phototropism
Spiegazione
Phototropism is a plant growth response toward or away from light. Gravitropism is the corresponding response to gravity.
It becomes unevenly distributed and stimulates cell elongation in particular regions
Spiegazione
Auxin is made in the shoot tip, becomes unequally distributed in response to light and gravity, and stimulates cell elongation, causing growth to occur unevenly.
It produces genetically identical cells while preserving chromosome number
Spiegazione
Mitosis produces genetically identical daughter cells and maintains the original chromosome number. Meiosis, in contrast, halves the chromosome number and generates genetic differences.
Mitosis producing genetically identical replacement cells
Spiegazione
Mitosis supports tissue repair by producing genetically identical cells that can replace damaged or dying cells. Meiosis and fertilisation are associated with sexual reproduction rather than routine tissue replacement.
One set
Spiegazione
A haploid nucleus contains one set of chromosomes, whereas a diploid nucleus contains two sets. Human diploid cells contain 23 pairs of chromosomes.
It is reduced from diploid to haploid
Spiegazione
Meiosis is a reduction division that halves the chromosome number from diploid to haploid during gamete production. It also produces genetically different cells.
Asexual reproduction uses one parent and produces identical offspring, whereas sexual reproduction involves fusion of haploid nuclei and produces variation
Spiegazione
Asexual reproduction involves one parent and produces genetically identical offspring. Sexual reproduction involves fusion of haploid nuclei to form a diploid zygote and usually produces genetically different offspring.
Pollen tube growth into the ovule, fertilisation, seed development from ovules, and fruit development from the ovary
Spiegazione
After pollination, the pollen tube grows into the ovule and fertilisation occurs. The ovules then develop into seeds, while the ovary develops into a fruit.
Suitable temperature, water, and oxygen
Spiegazione
Seeds require a suitable temperature, water, and oxygen for germination. Light and carbon dioxide are not listed as the essential germination conditions.
A flagellum for movement, mitochondria for energy, and acrosome enzymes for fertilisation
Spiegazione
The sperm cell has a flagellum for movement, mitochondria that provide energy, and enzymes in the acrosome involved in fertilisation. The egg instead has energy stores and a jelly coat that changes at fertilisation.
Differences between individuals of the same species
Spiegazione
Variation refers to differences between individuals belonging to the same species. It is distinct from the definition of a species, which concerns organisms capable of reproducing together.
A range of heights with many intermediate values
Spiegazione
Continuous variation produces a range of phenotypes between two extremes and includes intermediate values, such as different heights. Discontinuous variation produces distinct categories with no intermediates.
Discontinuous variation is usually caused by genes alone, whereas continuous variation is caused by genes and the environment
Spiegazione
Discontinuous variation is usually determined by genes only. Continuous variation results from the combined effects of genes and environmental conditions.
It determines the amino-acid sequence, which affects the protein’s shape
Spiegazione
The sequence of bases in a gene determines the sequence of amino acids in the protein. Different amino-acid sequences produce proteins with different shapes.
A deliberate change to an organism’s genetic material by removing, changing, or inserting genes
Spiegazione
Genetic modification involves deliberately removing, changing, or inserting individual genes. A random change in the DNA base sequence is a mutation, not genetic modification.
It contains the human gene controlling insulin production
Spiegazione
The human gene controlling insulin production is inserted into bacterial DNA, enabling bacteria to produce human insulin commercially. Bread and ethanol production are associated with yeast, not this insulin-production process.
They reproduce rapidly and contain plasmids that can be manipulated
Spiegazione
Bacteria are useful because they reproduce rapidly, can make complex molecules, and possess plasmids that can be manipulated. Their growth and genetic manipulation also present no ethical concerns in this context.
To optimize large-scale production by controlling factors such as temperature, pH, oxygen, and nutrients
Spiegazione
Fermenters support large-scale production by bacteria and fungi while controlling temperature, pH, oxygen, nutrient supply, and waste products. These conditions help maintain efficient production.
An ecosystem includes both organisms and their interacting physical environment
Spiegazione
An ecosystem consists of a community of organisms together with their environment and the interactions between them. A community contains populations of different species but excludes the physical environment.
Sun, food chains and webs, then the environment
Spiegazione
Energy usually enters biological systems from the Sun, passes through food chains and webs, and is eventually transferred to the environment. Transfer between trophic levels is inefficient, unlike nutrient recycling by decomposers.
More nitrates, increased producer growth, increased decomposition, lower dissolved oxygen, and death of oxygen-dependent organisms
Spiegazione
Eutrophication begins with increased nitrate availability and producer growth. Decomposition and aerobic respiration by decomposers then reduce dissolved oxygen, causing organisms that require oxygen to die.
The dissolved oxygen concentration
Spiegazione
The dependent variable is the factor measured in response to the scientist’s change. Here, dissolved oxygen concentration is measured after changing the fertilizer amount.
The school’s exams officers
Spiegazione
Exams officers submit entries to Cambridge International and work with candidates to select the correct number of candidates and syllabus components. Candidates do not directly submit the official entries.
Geographical areas assigned specific examination timetables
Spiegazione
Administrative zones are geographical areas to which Cambridge schools are allocated. Each zone uses its own specific examination timetable.
English only
Spiegazione
The syllabus and related assessment materials are available in English only. This does not prevent eligible candidates from receiving accessibility arrangements that modify assessment access.
Access arrangements, including modified papers
Spiegazione
Access arrangements, including modified papers, are the principal means of reducing assessment barriers for eligible candidates. They must still preserve the security and integrity of the assessment.
Evidence of the assessment barrier and the candidate’s normal way of working
Spiegazione
Requested arrangements should be supported by evidence of the candidate’s barrier to assessment and should reflect the candidate’s normal way of working at school.
A*
Spiegazione
Cambridge O Level grades range from A* as the highest grade to E as the lowest listed passing grade. “Ungraded” is not a grade within that range.
On the statement of results but not on the certificate
Spiegazione
“Ungraded” appears on the statement of results when performance falls below the standard for grade E, but it does not appear on the certificate.
Learning and achievement against syllabus knowledge, understanding, and skills
Spiegazione
Cambridge O Level assessment measures learning and achievement against the syllabus knowledge, understanding, and skills. It also indicates likely future success, but does not guarantee it.
It contained no significant changes affecting teaching
Spiegazione
Version 4 was published in December 2025 and contained no significant changes affecting teaching. Its only change was an updated weblink on page 42.
A minor typographical correction to metric units and clarification of Paper 02’s duration
Spiegazione
Version 2 made a minor typographical change to the metric units on page 38 and clarified that Paper 02 lasts 1 hour 45 minutes. The command-word amendment belonged to version 3.
Memorizza le risposte con 88 flashcard su Biology Coordination and Inheritance.
How can animal and plant cells be examined under a microscope?
Using a temporary stain like methylene blue or iodine solution.
Which organelles do animal cells contain?
Ribosomes, mitochondria, a nucleus, cytoplasm, and a cell membrane.
What additional structures do plant cells have compared to animal cells?
Chloroplasts, a sap vacuole, and a cellulose cell wall.
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