SBI3U · Exam review

Biology Exam Review

A practice exam with questions from all 5 units, then the key facts from every lesson, unit by unit. For a deeper look at one unit, open its test review.

Unit test reviews

Practice exam

35 questions, the same number from each unit. Each one shows the lesson it comes from.

Unit 1: Classification and Taxonomy
1
Which scientific name is written correctly?
Unit 1: Dichotomous Keys and Field Sampling
2
Which couplet is best for a dichotomous key?
Unit 1: Prokaryotes, Eukaryotes and Viruses
3
Which observation most strongly supports the idea that chloroplasts were once free-living bacteria?
Unit 1: Protists and Fungi
4
Put the steps of fungal feeding in order.
1. 1Absorbed nutrients fuel growth of more hyphae
2. 2Small molecules are absorbed through the hyphal walls
3. 3Large molecules are broken down outside the hyphae
4. 4Hyphae grow into the food source
5. 5Hyphae release digestive enzymes
Unit 1: From Algae to Flowers: Plant Diversity and Evolution
5
Why could seed plants spread into dry habitats where ferns struggle?
Unit 1: The Animal Kingdom: Invertebrates to Vertebrates
6
Match each body-cavity type to an example phylum.
Acoelomate
Pseudocoelomate
Coelomate
Unit 1: Biodiversity and Human Impact
7
Which conservation strategy protects all three levels of biodiversity at once?
Unit 2: The Theory of Evolution and Its Evidence
8
Which idea from Charles Lyell was most important to Darwin's thinking?
Unit 2: The Theory of Evolution and Its Evidence
9
Why is DNA comparison considered especially strong evidence for evolution?
Unit 2: Natural Selection and Adaptation
10
Which statement about antibiotic resistance is correct?
Unit 2: Mechanisms of Evolutionary Change
11
Why does genetic drift have a much stronger effect in small populations?
Unit 2: Selective Breeding: Benefits and Trade-offs
12
The cross that produced Marquis wheat was made in 1892, and the variety was released to farmers in about 1909. How many years did the breeding program take? Give a whole number.
Unit 2: Speciation and Extinction
13
According to the biological species concept, two organisms belong to the same species if they:
Unit 2: Speciation and Extinction
14
Which species is most likely to be vulnerable to extinction if its habitat changes rapidly?
Unit 3: DNA, Genes, Chromosomes and Mitosis
15
Arrange the levels of genetic organization from smallest to largest.
1. 1Gene
2. 2Genome
3. 3Chromosome
4. 4Nucleotide
Unit 3: Meiosis
16
In which stage do homologous chromosomes separate and move to opposite poles?
Unit 3: Mendelian Inheritance
17
A pea plant has the genotype $Tt$ , where $T$ (tall) is dominant to $t$ (short). Which statement is correct?
Unit 3: Beyond Simple Dominance
18
A red bull and a white cow have a calf whose coat has a mix of red hairs and white hairs. What pattern of inheritance does this show?
Unit 3: Beyond Simple Dominance
19
Match each example to its pattern of inheritance.
Red and white snapdragons produce pink offspring
Type AB blood shows both A and B markers
A carrier mother passes a trait to half her sons
Two genes give a 9 : 3 : 3 : 1 phenotypic ratio
Unit 3: Gene Mutations and Single-Gene Disorders
20
SemBioSys Genetics of Calgary engineered which organism to produce human insulin?
Unit 3: Chromosomal Disorders and Genetic Technologies
21
What is the name for a picture of an individual's chromosomes arranged in homologous pairs by size and banding pattern?
Unit 4: The Digestive System
22
Where does the chemical digestion of protein begin?
Unit 4: The Respiratory System
23
What does the diaphragm do during inhalation?
Unit 4: The Circulatory System
24
Which chamber of the heart has the thickest muscular wall?
Unit 4: Dissection: How the Systems Fit Together
25
In a fetal pig, which term describes the position of the kidneys relative to the intestines?
Unit 4: Dissection: How the Systems Fit Together
26
Which action is an example of the "Replace" principle of the Three Rs?
Unit 4: Breathing, Circulation and Digestion Across the Animal Kingdom
27
Why is a four-chambered heart linked to endothermy in birds and mammals?
Unit 4: System Disorders and Medical Technology
28
Match each technology to how it works.
MRI
CT
Ultrasound
Insulin pump
Unit 5: Plant Tissues and Structures
29
Which tissue produces the new cells that make a root grow longer?
Unit 5: Plant Tissues and Structures
30
Put these leaf layers in order from the top surface of the leaf to the bottom surface.
1. 1Lower epidermis
2. 2Spongy mesophyll
3. 3Palisade mesophyll
4. 4Cuticle
5. 5Upper epidermis
Unit 5: Transport in Plants
31
At 400×, a microscope's field of view is 0.50 mm in diameter. A leaf peel shows 30 stomata in one field of view. What is the stomatal density, in stomata per mm², to the nearest whole number?
stomata/mm²
Unit 5: Plant Growth and Reproduction
32
Which hormone is mainly responsible for a shoot bending toward light?
Unit 5: Plant Growth and Reproduction
33
Corn has a diploid chromosome number of 2n = 20. How many chromosomes are in each cell of a corn kernel's endosperm?
chromosomes
Unit 5: Plants, Sustainability and Society
34
In the Haudenosaunee Three Sisters planting, what is the main role of the squash?
Unit 5: Plants, Sustainability and Society
35
Match each medicine to the plant it was first derived from.
ASA (aspirin)
Morphine
Quinine
Paclitaxel
Digoxin

Key facts by unit

Unit 1: Diversity of Living Things

Classification and Taxonomy

Ranks from broadest to most specific: domain, kingdom, phylum, class, order, family, genus, species.
Binomial name = Genus (capitalized) + specific epithet (lowercase), italicized or underlined: Homo sapiens.
Three domains: Bacteria and Archaea (prokaryotic) and Eukarya (eukaryotic). Archaea are more closely related to Eukarya than to Bacteria.
Six kingdoms: Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia.
The lower the rank two organisms share, the more closely related they are.
Cladograms group organisms by shared derived characteristics; each node is a common ancestor.

Dichotomous Keys and Field Sampling

A dichotomous key offers two contrasting choices at each step; a key for $n$ organisms needs $n - 1$ couplets.
Good couplets use observable, stable features, stated as true opposites.
Population density: $D = \frac{total counted}{total area sampled} .$
Estimated population: $N = D \times$ total habitat area.
Random placement and many replicate samples reduce bias and error.
Mark and recapture for mobile animals: $N = \frac{M \times C}{R}$ .

Prokaryotes, Eukaryotes and Viruses

Prokaryotes: no nucleus, circular DNA in a nucleoid, 70S ribosomes, binary fission. Eukaryotes: nucleus, linear chromosomes, 80S ribosomes, membrane-bound organelles.
Typical sizes: prokaryotes about 1–10 µm, eukaryotic cells about 10–100 µm, viruses about 20–300 nm (1 µm = 1000 nm).
A virus = DNA or RNA inside a protein capsid, sometimes with an envelope; it can reproduce only inside a host cell.
Lytic cycle: attachment, entry, replication, assembly, release (cell bursts).
Endosymbiotic theory: mitochondria came from engulfed aerobic bacteria and chloroplasts from engulfed photosynthetic bacteria (cyanobacteria).
Evidence: both organelles have circular DNA, 70S-type ribosomes, double membranes and divide like bacteria.

Protists and Fungi

Protists are eukaryotes that are not fungi, plants or animals; they are grouped informally as animal-like, plant-like or fungus-like by how they get food.
Amoeba moves and feeds with pseudopods, Paramecium with cilia, and Euglena with a flagellum; freshwater protists use contractile vacuoles to expel excess water.
Most protists reproduce asexually by binary fission; Paramecium can exchange genetic material by conjugation, which adds variation without making new cells.
Fungi are built of chitin-walled hyphae forming a mycelium, digest food outside their bodies and absorb it, and spread by spores.
Zygomycetes make zygosporangia, ascomycetes make spores in asci, and basidiomycetes make spores on basidia.
Fungi are key decomposers and form lichens (with algae) and mycorrhizae (with plant roots); some cause disease and Penicillium gave us penicillin.

From Algae to Flowers: Plant Diversity and Evolution

Land plants evolved from freshwater green algae; both share chlorophyll a and b, cellulose walls and starch storage.
Key adaptations to land: cuticle (water loss), stomata (gas exchange), vascular tissue (transport and support), pollen and seeds (reproduction without water), flowers and fruits (pollination and dispersal).
Alternation of generations: sporophyte (2n) → meiosis → spores (n) → gametophyte (n) → mitosis → gametes (n) → fertilization → zygote (2n) → sporophyte.
The gametophyte dominates in bryophytes; the sporophyte dominates in ferns, gymnosperms and angiosperms.
Order of appearance: bryophytes → seedless vascular plants (ferns) → gymnosperms → angiosperms.
Monocots: one cotyledon, parallel veins, parts in threes. Dicots: two cotyledons, net veins, parts in fours or fives.

The Animal Kingdom: Invertebrates to Vertebrates

Animals are multicellular heterotrophs that ingest food, lack cell walls and are motile at some stage.
Symmetry: asymmetrical (sponges), radial (cnidarians, adult echinoderms) or bilateral (most animals, with cephalization).
Tissue layers: none (sponges), two (cnidarians) or three, with mesoderm (all other phyla).
Body cavity: acoelomate (flatworms), pseudocoelomate (roundworms) or coelomate (annelids, molluscs, arthropods, echinoderms, chordates).
Chordates have a notochord, dorsal hollow nerve cord, pharyngeal slits and post-anal tail at some stage of life.
Vertebrate classes: fish, amphibians, reptiles, birds, mammals; birds and mammals are endotherms with four-chambered hearts.

Biodiversity and Human Impact

Three levels of biodiversity: genetic (alleles within a species), species (richness and evenness), ecosystem (variety of ecosystems).
Simpson's index of diversity: $D = 1 - \frac{\sum n ( n - 1 )}{N ( N - 1 )}$ ; closer to 1 means more diverse.
Biodiversity increases resilience through functional redundancy, complex food webs and genetic variation.
Major threats: habitat loss, invasive species, overharvesting, pollution, monoculture and climate change.
Genetically uniform populations, such as monocultures, can be wiped out by a single disease.

Unit 2: Evolution

The Theory of Evolution and Its Evidence

Evolution is descent with modification: species change over generations and share common ancestors.
Lamarck's inheritance of acquired characteristics was rejected because changes to body cells during life are not passed on in eggs and sperm.
Homologous structures (same origin, different function) show common ancestry; analogous structures (same function, different origin) do not.
Radiometric dating: after $n$ half-lives, the fraction of isotope remaining is $(\frac{1}{2})^{n}$ ; carbon-14 has $t_{1/2} \approx 5730$ years.
Five independent lines of evidence support evolution: fossils, biogeography, comparative anatomy, embryology and molecular biology (DNA and proteins).

Natural Selection and Adaptation

Natural selection needs four conditions: variation, overproduction, selection (differential survival and reproduction) and inheritance.
Fitness = relative reproductive success, not strength or speed.
Individuals do not evolve; populations evolve as allele frequencies change over generations.
Batesian mimicry: harmless mimics harmful. Müllerian mimicry: harmful species resemble each other.
Resistance evolves because the antibiotic or pesticide kills susceptible individuals and leaves resistant variants that were already present to reproduce.
Artificial selection = humans choose which individuals breed; it follows the same logic as natural selection.

Mechanisms of Evolutionary Change

Evolution at the population level = a change in allele frequencies over generations.
Allele frequency of $A$ = $\frac{2 ( AA ) + ( A a )}{2 N}$ ; all allele frequencies for one gene add to 1.
Mutation is the only source of new alleles; gene flow, drift, selection and non-random mating change the frequencies of existing alleles.
Genetic drift is random and has its greatest effect in small populations; the bottleneck and founder effects are special cases.
Sexual selection favours traits that increase mating success, through competition (intrasexual) or mate choice (intersexual).

Selective Breeding: Benefits and Trade-offs

Selective breeding (artificial selection) needs variation, inheritance and human-chosen reproduction; it changes allele frequencies just as natural selection does.
Inbreeding makes lines uniform but increases homozygosity for harmful recessive alleles, causing inbreeding depression.
Hybridization combines traits from two lines and often produces hybrid vigour.
Canadian examples: Marquis wheat (early ripening), canola bred from rapeseed (low erucic acid and glucosinolates), Holstein dairy cattle (milk yield).
Monocultures of genetically uniform crops, such as the clonal Gros Michel banana, can be wiped out by a single disease.
Seed banks preserve genetic diversity; breeding mixes genes within a species, while genetic modification inserts specific genes, possibly from other species.

Speciation and Extinction

Biological species concept: populations that interbreed in nature to produce fertile offspring and are reproductively isolated from other groups.
Prezygotic barriers (habitat, temporal, behavioural, mechanical, gametic) prevent zygote formation; postzygotic barriers (reduced hybrid viability, reduced hybrid fertility, hybrid breakdown) act after it.
Allopatric speciation requires a geographic barrier; sympatric speciation occurs without one, often by polyploidy in plants.
Adaptive radiation: one ancestor gives rise to many species filling different niches (e.g. Darwin's finches).
Canadian risk categories: extinct, extirpated, endangered, threatened, special concern.

Unit 3: Genetic Processes

DNA, Genes, Chromosomes and Mitosis

Nucleotide = phosphate + deoxyribose + base; A pairs with T and G pairs with C.
Gene: a DNA segment that codes for a protein. Chromosome: one DNA molecule with its proteins. Genome: all of an organism's DNA.
Cell cycle: G1 (growth) → S (DNA replication) → G2 (preparation) → M (mitosis and cytokinesis).
Mitosis: prophase, metaphase, anaphase, telophase (PMAT), then cytokinesis; it produces two diploid, genetically identical cells.
Somatic cells divide by mitosis for growth and repair; germ cells undergo meiosis to make gametes.
In a root-tip count, % of cells in a phase ≈ % of the cycle spent in that phase.

Meiosis

Diploid $2 n$ has two sets of chromosomes; haploid $n$ has one set. Humans: $2 n = 46$ , $n = 23$ .
Meiosis I separates homologous chromosomes (reduction division); meiosis II separates sister chromatids.
One diploid cell $\to$ four genetically different haploid cells.
Independent assortment gives $2^{n}$ chromosome combinations per gamete ( $2^{23} = 8388608$ in humans).
Crossing over happens between non-sister chromatids at chiasmata during prophase I.
Non-disjunction in meiosis I makes all four gametes abnormal; in meiosis II, two of the four.

Mendelian Inheritance

Law of segregation: the two alleles for a gene separate into different gametes, so each gamete carries one allele.
$A a \times A a$ gives genotypes $1 AA : 2 A a : 1 aa$ and phenotypes $3$ dominant $: 1$ recessive.
Test cross: unknown dominant $\times$ homozygous recessive. Any recessive offspring means the unknown is heterozygous; $A a \times aa$ gives $1 : 1$ .
Product rule (and): $P (A and B) = P (A) \times P (B)$ . Sum rule (or): $P (A or B) = P (A) + P (B)$ for mutually exclusive outcomes.
Genotype is the allele combination; phenotype is the observable trait.

Beyond Simple Dominance

Incomplete dominance: heterozygote is intermediate; $C^{R} C^{W} \times C^{R} C^{W}$ gives $1$ red $: 2$ pink $: 1$ white.
Codominance: both alleles are fully expressed in the heterozygote (roan cattle, type AB blood).
ABO: $I^{A}$ and $I^{B}$ are codominant, both dominant to $i$ ; type O is $ii$ .
X-linked recessive: males ( $X^{b} Y$ ) show the trait with one allele; females need $X^{b} X^{b}$ . Fathers pass their X to every daughter and never to sons.
$A a B b \times A a B b$ gives $9 : 3 : 3 : 1$ ; for independent genes, multiply the single-gene probabilities.

Gene Mutations and Single-Gene Disorders

A mutation is a permanent change in DNA base sequence; germline mutations are inherited, somatic mutations are not.
Substitution: one base replaced, changing at most one codon. Insertion or deletion of a number of bases that is not a multiple of 3 causes a frameshift.
Cystic fibrosis (CFTR gene, identified in 1989 by Lap-Chee Tsui's team in Toronto), sickle cell disease, PKU and Tay-Sachs are autosomal recessive; Huntington disease is autosomal dominant.
Heterozygote advantage: sickle cell carriers resist severe malaria, so the allele stays common where malaria is widespread.
Two carriers of a recessive allele (Aa × Aa) have a 1/4 chance of an affected child; an affected heterozygote with a dominant allele (Hh × hh) has a 1/2 chance.
Treatments range from diet (PKU) and symptom management to protein-targeting drugs, transplants, gene therapy, and medicines like insulin made by engineered organisms.

Chromosomal Disorders and Genetic Technologies

Trisomy (2n + 1) = 47 chromosomes in humans; monosomy (2n − 1) = 45. Both usually come from non-disjunction.
Down syndrome is trisomy 21; Turner syndrome is 45,X; Klinefelter syndrome is 47,XXY.
A karyotype arranges metaphase chromosomes in pairs by size, centromere position and banding pattern.
Recombinant DNA: restriction enzyme cuts, DNA ligase joins a gene into a plasmid, bacteria express the protein (e.g. human insulin).
Somatic gene therapy is not inherited; germline changes are, and Canadian law prohibits heritable changes to the human genome.
Embryonic stem cells are pluripotent; adult stem cells are multipotent; iPSCs are adult cells reprogrammed to be pluripotent.

Unit 4: Animals: Structure and Function

The Digestive System

Mechanical digestion (chewing, churning, emulsifying) increases surface area; chemical digestion (enzymes, acid) breaks bonds by hydrolysis.
Carbohydrates become monosaccharides, proteins become amino acids, and lipids become fatty acids and glycerol.
Starch digestion begins in the mouth (salivary amylase), protein digestion in the stomach (pepsin, pH about 2), and fat digestion mainly in the small intestine (lipase helped by bile).
Villi and microvilli give the small intestine a huge surface area for absorption; sugars and amino acids enter capillaries, fats enter lacteals.
The large intestine absorbs remaining water and houses bacteria that make vitamin K.
Food energy: about 4 Cal/g for carbohydrate and protein and 9 Cal/g for fat.

The Respiratory System

Air path: nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli.
Inhalation: diaphragm and external intercostals contract, chest volume increases, lung pressure drops, air flows in.
Gases move across the alveoli by diffusion down a concentration (diffusion) gradient; no energy is used.
Hemoglobin in red blood cells carries almost all oxygen; each molecule can carry up to four $O_{2}$ .
Minute ventilation = breathing rate × tidal volume; a typical resting breathing rate for healthy adults is about 12 to 20 breaths/min.
Rising blood carbon dioxide is the main stimulus that increases breathing rate.

The Circulatory System

Blood path: vena cavae, right atrium, tricuspid valve, right ventricle, pulmonary arteries, lungs, pulmonary veins, left atrium, bicuspid valve, left ventricle, aorta.
Arteries carry blood away from the heart and veins carry blood toward it, regardless of oxygen content; capillary walls are one cell thick for exchange.
The left ventricle has the thickest wall because it pumps blood through the whole systemic circuit.
Blood is about 55% plasma; red blood cells carry oxygen, white blood cells fight infection, platelets start clotting.
Blood pressure is systolic/diastolic, typically around 120/80 mmHg for a healthy adult; resting heart rate is typically about 60 to 100 beats/min.
Cardiac output = heart rate × stroke volume.

Dissection: How the Systems Fit Together

Anterior = toward the head, posterior = toward the tail, dorsal = back, ventral = belly; left and right are the specimen's own.
Cut skin with scissors tips up, open the specimen ventral side up, and separate tissues with a blunt probe.
The diaphragm divides the thoracic cavity (heart, lungs, trachea, esophagus, thymus) from the abdominal cavity (liver, stomach, intestines, pancreas, spleen).
Hepatic portal system: blood from the intestines goes to the liver before the heart.
Pulmonary circuit: right ventricle → pulmonary arteries → lungs → pulmonary veins → left atrium.
The Three Rs of animal use: Replace, Reduce, Refine.

Breathing, Circulation and Digestion Across the Animal Kingdom

Good respiratory surfaces are moist, thin, large in area and well supplied with blood; surface area to volume ratio falls as animals grow.
Gas exchange: skin (earthworms, frogs), gills (fish), tracheae (insects), lungs (most land vertebrates).
Countercurrent exchange in gills keeps a concentration gradient along the whole gill, extracting most of the oxygen from water.
Open circulation: hemolymph bathes organs at low pressure (insects). Closed circulation: blood stays in vessels at higher pressure (earthworms, vertebrates).
Hearts: fish 2 chambers (single circuit), amphibians 3, most reptiles 3 (partly divided), birds and mammals 4 (complete separation, supports endothermy).
Gastrovascular cavity has one opening; a complete tract allows specialization such as the crop, gizzard and the four-chambered ruminant stomach.

System Disorders and Medical Technology

The digestive and respiratory systems supply glucose and oxygen; the circulatory system delivers them to cells and removes carbon dioxide.
Asthma narrows the bronchioles (inflammation, muscle tightening, mucus); emphysema destroys alveolar walls, reducing the surface area for diffusion.
Most peptic ulcers are linked to Helicobacter pylori infection or long-term use of anti-inflammatory pain relievers, which let acid damage the stomach or duodenum lining.
Arteriosclerosis is the hardening and narrowing of arteries; a blocked coronary artery causes a heart attack, while cardiac arrest is an electrical failure of the heartbeat.
CT uses X-rays (ionizing radiation); MRI uses magnetic fields and radio waves; endoscopes look inside the digestive tract directly.

Unit 5: Plants: Anatomy, Growth, and Function

Plant Tissues and Structures

Four tissue types: meristematic (divides), dermal (protects and exchanges), ground (photosynthesis, storage, support) and vascular (transport).
Apical meristems add length (primary growth); lateral meristems such as the vascular cambium add width (secondary growth).
Xylem carries water and minerals up from the roots in dead, hollow cells; phloem carries sugars from where they are made to where they are used, in living sieve tube cells.
Leaf layers from top to bottom: cuticle, upper epidermis, palisade mesophyll, spongy mesophyll (with veins), lower epidermis with stomata and guard cells.
Monocots: one cotyledon, parallel veins, scattered bundles, fibrous roots, flower parts in threes. Dicots: two cotyledons, net veins, bundles in a ring, taproot, parts in fours or fives.
Biological drawings: $magnification = \frac{drawing size}{actual size},$ with both sizes in the same unit.

Transport in Plants

Osmosis: water diffuses across a selectively permeable membrane toward the side with the higher solute concentration.
Root hairs actively pump in mineral ions (using ATP), so water follows by osmosis; the Casparian strip forces water through endodermal membranes.
Cohesion-tension: transpiration creates tension, cohesion (hydrogen bonds) keeps the water column continuous, and adhesion to xylem walls helps it resist gravity.
Guard cells take in potassium ions and water, swell, and open the stoma; they lose water and close it. Abscisic acid triggers closing during drought.
Transpiration speeds up with brighter light, higher temperature, lower humidity and more wind.
Pressure flow: sugar loaded at a source draws in water and raises pressure, pushing phloem sap toward a sink where sugar is unloaded.

Plant Growth and Reproduction

Growth depends on light, water, nutrients (especially N, P and K), temperature and soil pH; the factor in shortest supply limits growth.
Auxins: cell elongation, phototropism and gravitropism, apical dominance, root formation on cuttings. Gibberellins: stem elongation, seed germination, fruit size.
Phototropism: auxin moves to the shaded side of the shoot, those cells elongate more, and the shoot bends toward the light.
Stamen = anther + filament (male). Pistil = stigma + style + ovary (female). After fertilization, ovule becomes seed and ovary becomes fruit.
Germination needs water, oxygen and a suitable temperature; imbibition starts it and the radicle emerges first.
Asexual reproduction (cuttings, grafting, runners, tubers, bulbs) makes genetically identical clones.

Plants, Sustainability and Society

Plants provide food, medicines, building materials, fibres and fuels, and services such as erosion control, flood control and water filtering.
ASA (aspirin) traces back to salicin in willow bark; other plant-derived medicines include morphine (opium poppy), quinine (cinchona) and paclitaxel (Pacific yew).
Crop rotation with legumes restores soil nitrogen (bacteria in root nodules fix nitrogen) and breaks pest cycles; seed saving keeps locally adapted, genetically diverse varieties.
Haudenosaunee Three Sisters: corn supports the beans, bacteria in bean root nodules fix nitrogen, and squash leaves shade the soil; together they provide starch, protein and vitamins.
Primary succession begins with no soil (pioneers: lichens and mosses); secondary succession begins where soil remains after a disturbance and proceeds faster.