Process Description of process Example of material exchanged
Component of plasma membrane involved
Simple diffusion Passive process in which particles move from an area of high concentration to an area of low concentration, along a concentration gradient
oxygen, carbon dioxide, urea
Diffuse directly through the phospholipids bilayer by passing between the phospholipids molecules
Facilitated diffusion
Passive process—particles move along a concentration gradient but their movement is assisted by protein channels embedded in the membrane
amino acids, glucose Protein channel embedded in plasma membrane
Osmosis Special kind of diffusion that involves the passive movement of water through a partially permeable membrane from a region of high concentration of free water molecules to a region of low concentration of free water molecules.
water Diffuse directly through the phospholipids bilayer by passing between the phospholipids molecules
Active transport Energy-requiring process in which particles move from a region of low concentration to an area of high concentration
materials that are required in relatively high concentrations by cells, e.g. mineral ions by plant root hair cells; digested nutrients by gut epithelial cells in animals
Enzymes do not affect the final amount of product in a reaction.
Enzymes decrease the activation energy required to initiate reactions.
Worksheet 5: Active enzymes 1
2 Enzymes are specific for a particular substrate, in the same way a key is specific for a particular lock. A given
enzyme will only catalyse a reaction involving the substrate molecules that fit its active site.
3 Enzyme activity is affected by temperature, pH, concentration of substrate, concentration of product and concentration of enzyme.
4 When the active site of an enzyme is denatured, its shape is altered so that it no longer ‘fits’ the substrate molecule. When this happens, the ability of the enzyme to catalyse a reaction ceases, i.e. no further reaction occurs.
6 Graph B represents a reaction in which energy is released—this makes it an exergonic reaction. Energy stored in the sucrose molecule is present in the chemical bonds of the molecule. When the chemical bond between the glucose and the fructose molecule is broken, energy is released.
Worksheet 6: Energy transformations 1 From top to bottom: mitochondrion, lactic acid, electron transport, exergonic reaction, chloroplast, Krebs
2 • The energy-rich molecule ATP is generated from ADP and inorganic phosphate in a cycle that continues to make energy available for cells.
• First step in breakdown of glucose—glucose molecule is split (glycolysis) to produce two pyruvate molecules (3C molecules), generating 2 molecules of ATP.
• The process of photosynthesis combines carbon dioxide and water in the presence of light and chlorophyll to construct energy-rich glucose molecules. Oxygen and water are also produced.
Worksheet 7: Mighty mitochondria 1 Cellular respiration is the process in which complex organic compounds such as glucose are broken down to
release energy. Carbon dioxide and water are byproducts.
5 Mitochondria make energy available to cells, which is used to power or drive metabolic processes. They represent the cell’s power generator, and so are likened to a powerhouse.
Worksheet 8: Zooming in on photosynthesis 1 Correct order of terms: grana, light-dependent, stroma, light-independent (or dark)
2
3 Any two of:
• CO2 concentration—the higher the CO2 concentration, the greater the rate of photosynthesis.
• Light intensity—the greater the light intensity, the greater the rate of photosynthesis.
• Temperature—rate of photosynthesis increases with increasing temperature until optimal temperature is reached.
• Water availability—water is an important ingredient in photosynthesis; reduced water availability reduces the rate of photosynthesis.
4 Feature 1: number of hydrogen bonds—adenine and thymine share three hydrogen bonds, and so can only bond with one another; cytosine and guanine share two hydrogen bonds.
Feature 2: size of base molecules—adenine and guanine are purines (double ring structure) so are large molecules; each bonds with a purine (single ring), thymine and cytosine respectively; this results in consistency of size at the ‘rungs’ of the DNA helix, keeping the strands parallel.
6 mRNA strand should follow structure shown in Figure 3.27, using the following order of bases:
G U G G A G U G A
Worksheet 12: Hypothetical halitosis 1 a Subjects 1 and 5.
b Subject 1 tests positive for both salivary proteins JM and PU, i.e. two positives for bad breath proteins. Subject 5 tests positive for three proteins, both JM and PU, and NS, which has no smell and so doesn’t cancel the effect of either JM or PU.
2 While Subject 4 tests positive for both JM and PU, the presence of protein TP cancels the effect of one of these. This effectively reduces the magnitude of the halitosis.
3 Neither Subjects 3 nor 6 tests positive for either of the bad breath proteins JM or PU. They both test positive for one salivary protein. Subject 3 tests positive for TP, which results in a pleasant odour, while Subject 6 tests positive for protein NS, which has no smell. Subject 3 has the most pleasant breath. Based on the SPIT results alone, Subject 3 gets the date.
4 Subjects 1 and 5—equal first place, followed by Subject 4, then Subjects 2 and 6—equal third, and Subject 3 with least halitosis.
Negative feedback system: stimulus–response system in which the response reduces the magnitude of the initial stimulus.
Disturbance detector: receptor that detects a change in internal or external environment that may lead to a change in that particular internal factor.
Misalignment detector: receptor that detects a change in an internal factor that is under homeostatic control.
Oxygen debt: the volume of oxygen that is required to break down the lactic acid accumulated during a period of anaerobic respiration.
Worksheet 14: Breathe deep—respiratory gases and negative feedback 1 Correct order of terms: response, reduced, limits, carbon dioxide, oxygen
2 receptor: chemoreceptors in arteries and brainstem
effector: diaphragm
response: increased breathing rate
feedback: decreased blood level of carbon dioxide
3 The negative feedback mechanism restores blood pH by reducing the amount of hydrogen ions that dissociate from H2CO3. This occurs as a result of the increased ventilation rate that maintains a high concentration gradient between the blood and the alveolar air, resulting in increased diffusion of carbon dioxide out of the blood at the alveoli.
Worksheet 15: Hormonal plants—plant growth regulators 1 Coleoptile A is the control against which the experimental set-ups B and C are compared. There should be no
change to the control. Any change to the control suggests that extraneous factors have influenced the test and this would render any results from the experimental set-ups inconclusive.
2 The mica sheets establish an impermeable barrier between cells at the tip and cells below the mica. Any materials present in the tip that might diffuse downwards and influence the bending response are blocked.
3 A plant growth regulator that is present in the tip and affects cells below is unable to diffuse downwards due to the mica. B establishes that when such a chemical is blocked from moving down the coleoptile away from the light source, no bending response can occur.
4 The experimental results support the hypothesis. Coleoptile C did show a bending response towards the light source when a chemical present in the tip after exposure to light was able to move down the side of the coleoptile away from the light source.
5 Experimental design: Set up a number of coleoptiles into two groups, half with no foil cap (Group A) and half with foil cap (Group B). Expose all of the coleoptiles to a light source from one direction only for a period of 1 hour.
Results: It is expected that Group A coleoptiles show a growth response (bending) towards the light source, and that Group B coleoptiles show no bending at all.
Hypothesis: If only those coleoptiles that had their tips stimulated by light showed the bending response, then the hypothesis would be supported.
Worksheet 16: Transpiring trees and other vascular plants
Worksheet 17: Critical signals—detecting and responding to signals 1 Correct order of responses: true, true, true, false, false, false, true, false, true, true, false, true, false, true
2 • Neurotransmitter is a signalling molecule released from the pre-synaptic membrane of nerve cells; neurotransmitter is a chemical messenger but it is not a hormone. Hormones are different kinds of chemical messengers that travel in the bloodstream.
• Excitability of nerve cells depends in part upon the unequal distribution of sodium ions and potassium ions inside and outside the cells (high concentration of sodium ions outside the cell, high concentration of potassium ions inside the cell).
• The pituitary gland is sometimes called the master gland of the endocrine system because of its role in coordinating the release of hormones from other endocrine glands.
• The intensity of a stimulus is important in the generation of an action potential—a stimulus must polarise a nerve cell sufficiently to reach the threshold potential in order for an action potential to occur.
• Misalignment detectors and disturbance detectors together ensure the stability of the internal environment. For example, in temperature regulation, disturbance detectors in the skin are sensitive to changes in the external environment and misalignment detectors in the brain fine-tune mechanisms that regulate core temperature.
• Plant hormones include auxins, gibberellins, abscisic acid and ethylene.
Worksheet 18: Signalling cells—cell communication 1
2 a An action potential or nerve impulse is a wave of electrical change that moves along a nerve cell.
b An action potential is generated when a nerve cell is sufficiently polarised by the difference in charge between the inside and outside of a cell to trigger depolarisation. This is called the threshold potential.
3 a acetylcholine
b Acetylcholine is called a signalling molecule because it binds with receptor sites on target cells and signals an instruction to respond in a particular way, i.e. it stimulates the target cell, causing a response.
4 a A → Z; B → Y; C → W; D → X
b receptor site
c The receptor sites on target cells are specific to particular signalling molecules, i.e. they bind with and respond only to the signalling molecules they fit.
Artificially acquired active immunity: immunity conferred by the administration of a vaccine that provokes antibody production
Toxoid: inactivated toxins (e.g. produced by bacteria) that are used in vaccines to produce antibodies in an immune response
Allergen: substance that provokes an allergic reaction
Worksheets 24: Horrible hayfever and other allergies 1
2 antibody
3 IgE
4 Mast cells are located in the walls of blood vessels, and in the lining of gut and respiratory passages.
5 The release of histamines causes dilation of blood vessels in a local area, resulting in leakage of white blood cells as well as an increased volume of tissue fluid, which leads to swelling.
6 Allergen particles combine with IgE immunoglobulins on mast cells, triggering the release of histamines and an allergic reaction. The reaction becomes increasingly lessened as fewer and fewer antibody sites are available for allergen particles. Eventually all sites are taken, so the incoming allergen cannot combine with immunoglobulin and no reaction occurs.
Worksheet 26: Counting characteristics—variation in a group 2 Figures entered into the table are dependent on class/sample size. It is expected that a ratio pattern of 3:1 will
emerge. However, this will depend on the make-up of the sample and in particular on the sample size. The larger the sample size, the closer to a 3:1 ratio will be expected.
3 A pattern of ratio of 3:1 is expected to emerge. Very small sample sizes may vary significantly from this. Any sample size is a random sample, so a ratio that is different from the expected result is possible.
4 Larger sample sizes are more likely to be representative of a population than smaller sample sizes. For example, a random sample of 2 marbles from a bucket containing 4 reds and 8 blues may net 2 red marbles. The sample is not representative of the ratio that exists in the entire ‘marble population’. Taking a random sample of 20 marbles from a bucket that contains 40 reds and 80 blues (the same ratio) is likely to net at least some of each colour. The larger the sample, the more representative it is likely to be, and therefore the more reliable.
Worksheet 27: Genetic dictionary—reading the code 1
2 a During transcription, the DNA template strand is copied to produce a single-stranded molecule of
mRNA.
b During translation, the nucleotide sequence in mRNA is interpreted using the genetic code—amino acids are arranged in a linear sequence to produce a polypeptide chain.
3 AUG is a start codon—it initiates polypeptide production. UAG is a ‘stop’ codon—it signals the end of polypeptide production.
4 polypeptide
Summary: The role of genes is to direct the production of polypeptides (proteins).
Worksheet 28: GTT—genetic tools and technology 1 Correct order of terms: genetic modification, endonucleases, polymerase chain reaction, Taq polymerase, gel
electrophoresis, DNA sequencing, DNA probes, recombinant DNA
2 Cloning: technology used to create genetically identical individuals
Primers: short, single-stranded DNA sequences that bind to specific DNA sequence in the larger DNA molecule; used to target a particular section of DNA, e.g. for the purposes of amplification
DNA ligase: enzyme that rejoins cut ends of DNA molecule
DNA profiling: technology used to produce a DNA banding pattern unique to an individual; banding pattern identified using technique such as gel electrophoresis
Genome: full complement of genes in a particular individual
Worksheet 29: PCR—a gene amplification technology 1 Target DNA is the section of a DNA molecule that has been identified for amplification.
2 The DNA polymerase adds nucleotides to the unzipped DNA strands, thereby constructing new copies of the original strands.
3 Taq polymerase functions normally at temperatures that are excessive for human DNA polymerase. PCR requires high temperatures, e.g. to denature the DNA molecule.
4 Primers are short, single-stranded DNA sequences that bind to a specific section of the DNA molecule. They are used in PCR to target the section of the DNA molecule to be amplified, i.e. they indicate the point along the DNA molecule at which amplification begins.
5 Adenine, thymine, cytosine, guanine. These nucleotides have been added to the buffer solution to provide the building materials for the construction of the DNA fragments to be copied.
6 The PCR reaction produces are very large number of target DNA copies in a relatively short time.
7 PCR technology makes large quantities of identical DNA fragments available for analysis using other techniques, when only very small amounts (not enough for meaningful analysis) may have been recovered at a crime scene, for example.
Worksheet 30: Cell reproduction—matchmaker 1 Correct order of terms: somatic cells, crossing-over, homologous chromosomes, gamete, differentiation,
2 Cell division: process in which a cell separates (divides) into two new cells
The following four terms represent sequential stages during the process of mitosis:
Prophase: duplicated chromosomes appear as fine strands, condensing to form double stranded chromosomes composed of two chromatids
Metaphase: chromosomes are arranged about the centre of the spindle attached by their centromeres
Anaphase: centromeres divide so that sister chromatids are separated, each moving to opposite poles
Telophase: nuclear membrane begins to reform and cell membrane pinches inwards in readiness for cell division
Cytokinesis: Dividing cell becomes completely separated into two new cells as cytoplasm is divided and cell membrane is formed between the cells
Interphase: Stage that occurs between mitotic divisions; chromosomes not visible during this stage; chromosome replication occurs as well as cell growth and metabolic processes
Worksheet 31: Marvellous meiosis—a mixture of gametes 1 ABC and abc
2 Mixing the chromosomes and then grouping them into gametes at random increases the variety of gamete combinations.
3 ABC, ABc, AbC, Abc, aBC, aBc, abC, abc
4 a 24 = 16
b 25 = 32
c 210 = 1024
5 chiasma
6 prophase I
7 Crossing-over results in new combinations of alleles on chromosomes, thereby increasing the variety of gametes that are produced.
Summary: Independent assortment of chromosomes and crossing-over events during meiosis contribute to the variety of gametes produced. Independent assortment means that the order in which homologous chromosome pair is not influenced by other homologous chromosome pairs. This ‘mixes’ up the maternal and paternal chromosomes. Crossing-over further increases the combinations of alleles along chromosomes, which in turn adds to the variety of gametes that are produced.
Worksheet 32: True or false?—karyotypes, alleles and mutations 1 Correct order of responses: false, true, true, false, false, true, false, true, true, false
2 • In a karyotype the full set of chromosomes of a cell or an individual are set out in a formal arrangement with chromosomes displayed in homologous pairs, the pairs usually arranged in order from largest to smallest.
• Metacentric, submetacentric and acrocentric are terms used to identify the approximate position of the centromere on chromosomes as ‘central’, ‘nearer one end than central’ and ‘close to one end’ respectively.
• In humans, females are said to homogametic because of the presence of similar sex chromosomes, while males are said to be heterogametic due to the presence of sex chromosomes that are not similar.
• A mutation is a change in the sequence of bases in a strand of DNA. This may result in damage or disease in the individual in which it occurs or to whom it is passed on. When silent mutations occur there is no observable change in phenotype of an individual.
• Frameshift mutations are generally more damaging than missense mutations because the addition or deletion of a single nucleotide in the DNA sequence results in a ‘shift’ in the codons so that during translation all subsequent amino acids placed in the polypeptide chain are altered.
Worksheet 33: Counting on karyotypes—chromosomal diagnoses 1 Individual A: Female, normal
Individual B: Male, trisomy 21 (Down syndrome)
Individual C: Male, XXY—extra X chromosome (Klinefelter’s syndrome)
Individual D: Female, XO—missing one X chromosome (Turner’s syndrome)
2 Sex determination, chromosomal abnormalities such as extra or missing chromosomes, translocation conditions in which one chromosome is physically connected to another.
3 Karyotyping does not provide information about gene mutations that might confer a genetic disease, because the shape of the chromosome in such instances remains unchanged.
4 The technique of ‘chromosome painting’ uses fluorescent dyes to identify particular chromosomes so that they are distinguishable from other chromosomes on the basis of colour. Each homologous pair takes up a different coloured fluorescent dye. Arranging homologous chromosomes in a karyotype can be done with greater accuracy.
Worksheet 34: Genotype, phenotype and crosses—crossword
Across 6 Describes the state of having only one allele of a pair rather than two; eg, X chromosome in human males.
7 Describes a characteristic that is observed in the phenotype of a heterozygote.
8 Genetic make-up of an individual in relation to one or more genes.
11 Describes a characteristic that is observed in the phenotype of an individual homozygous of a particular allele, but not observed in the heterozygote.
12 Alternative form of a gene.
Down 1 Describes alternative forms of a characteristic that are observed in intermediate form in the phenotype of a
heterozygote
2 Describes alternative forms of a characteristic that are fully expressed in the phenotype of a heterozygote
3 Cross between individuals that takes into account one particular characteristic
4 State of an individual that carries two different forms of a gene in relation to a particular characteristic
5 Cross between individuals that takes into account two different characteristics
6 State of an individual that carries identical alleles for a given gene
9 Cross between an individual displaying a dominant phenotype and an individual displaying a recessive phenotype (homozygous) for the purposes of determining whether the dominant individual is heterozygous or homozygous
10 Physical expression of a particular genotype
Worksheet 35: Mendel’s spin on meiosis—Mendel’s principles 1 During meiosis alleles for a given gene separate so that gametes are formed that each contain one copy of an
2 Map distance = number of recombinant offspring × 100 total number of offspring 1
= 12 × 100 300 1
= 4 map units
Worksheet 37: Puzzling pedigrees—analysing family histories 1 IAi, IBi respectively.
2 The expression of the alleles that determine A antigens and B antigens on red blood cells are codominant—they are fully and equally expressed in the phenotype. The expression of the i allele is recessive to both A and B.
3 The mode of inheritance for haemophilia is X-linked recessive. Males that carry the allele that confers haemophilia have only one X-chromosome—there is no homologue with an allele for the expression of normal clotting factor to mask the effect of the haemophilia allele.
4 Haemophilia appears in descendants of Queen Victoria who are not descendants of Leopold. Victoria’s second daughter must be a carrier to pass the condition on to her third son, and at least two of her daughters in the pedigree who also have sons with the condition.
Mass extinction of dinosaurs; small mammals become the dominant animal life
55 million years ago
Australia still connected to Antarctica via land bridge across Tasmania; Australian land still relatively close to South Pole
Wet but warmer conditions
Rainforests are dominant vegetation
Mammals including monotremes, marsupials and placentals; flightless birds, reptiles, amphibians
20 million years ago
Australia completely separated from Antarctica—an island continent; positioned much further north and closer to the equator
Warm in the north Rainforests in the north of the continent
Marsupials such as kangaroos, possums and koalas existed as well as marsupial lion; bats; reptiles including crocodiles, snakes, lizards; various bird species, insects
8 million years ago
Positioned further north Dry and warm Rainforests limited to coastal regions; open forests and woodlands dominate the drier interior
Megafauna such as diprotodont; marsupial lions and thylacines; kangaroos evolve to move on hind legs only; possums, platypus
4 million years ago
Australia almost in present position with northern boundary in equatorial region
Warm and wet Eucalyptus and acacia (wattle) dominate the landscape; wildflowers
Kangaroos, wallabies, parrots, crocodiles, snakes including giant pythons; rats and mice migrate from South East Asia
100 000 years ago
Still moving further northward; almost in present position; temporary land bridges connect mainland Australian to Tasmania in the south and New Guinea in the north
Fluctuations in polar ice-caps mean fluctuating climate change from cold, dry conditions to warm and wet
Eucalypts adapted to hot, dry conditions, grasslands
Already in present position Relatively wet until about 5000 years ago when the continent became drier
Open eucalypt forests, woodlands and grasslands, wildflowers
Megafauna have disappeared; present day species unique marsupials, birds including emu, parrots; reptiles, amphibians; European settlement has meant extinction for many species
2 110 million years ago, Australia was still connected to the southern landmass that once formed Gondwana. Its global position was much nearer the South Pole, so its climate was much colder and wetter than it is today. Since then it has became separated to form an isolated continent and has slowly moved northward to its present position, with its northern-most parts in the tropics. As a result, its climate has become much warmer and drier. Conifer forests have given way to eucalypts and wattles, rainforests in the warm and wet north-east coastal region, and desert conditions at the interior. Megafauna species have disappeared and the dominant species are the marsupial mammals and colourful birds. Australian plants and animals are unique in the world, having evolved in a cradle of long-term geographical isolation.
Worksheet 40: Evidence of evolution from anatomy and molecules—matchmaker 1 Correct order of terms: mitochondrial DNA, molecular clock, analogous structures, genetic linkage group,
homologous structures, von Baer’s law, comparative anatomy, DNA hybridisation, comparative embryology, thermal stability
2 Chloroplast DNA: DNA contained within chloroplasts
Tetrapod: vertebrate organism that features four limbs
Phylogenetic tree: simple tree diagram indicating evolutionary relationship between related organisms based on structural similarities
Fossil DNA: remnant DNA fragments extracted from remains of fossilised organisms
Vestigial structure: reduced structure present on an organism with no apparent function; suggests a remnant of a function in an evolutionary ancestor
Box 3: Dieldrin-resistant blowflies increase in a population exposed to the pesticide, while the frequency of sensitive individuals declines.
Box 2: A dairy farmer deliberately retains cows for breeding that produce large volumes of milk.
Box 4: A small population that is isolated on an island shows change in allele frequency resulting from chance only.
Box 5: Migration from one population into another introduces new genetic variation into the second population.
2 Variation: different forms of a particular characteristic that exists in a population
Adaptations: features of organisms that make them well-suited to their particular environment or lifestyle
Sexual reproduction: form of reproduction that involves the mixing of genetic information from two parents, thereby generating variety in offspring
Natural selection: process of evolutionary change within species such that individuals with favourable characteristics have an increased chance of survival and reproduction compared with individuals with less favourable characteristics
Biologically fit: individuals that are well adapted to the environment in which they live; produce more offspring than their less biologically fit counterparts
Artificial selection: process of change within a population/species that is driven by human intervention, whereby only those individuals featuring the most desirable characteristics are selected for breeding
Genetic drift: change in allele frequencies in a population that occur as a result of chance alone
Gene flow: exchange of genes between populations of a species as a result of breeding between individuals in those populations
Worksheet 43: Superbugs—a modern tragedy in natural selection 1 Variation exists within a population of Staphylococcus bacteria, i.e. some are resistant to the antibiotic and
some are not resistant.
Resistant individuals have the favourable phenotype in the presence of the antibiotic,
i.e. they are more biologically fit
Non-resistant individuals are sensitive to the antibiotic, i.e. they have an
unfavourable phenotype and are less biologically fit
↓ ↓ These resistant individuals are adapted to an environment in which the antibiotic is
present—they have a survival advantage - an increased chance of surviving and reproducing—they are ‘selected for’
Non-resistant individuals have a decreased chance of surviving and reproducing—they
are ‘selected against’
↓ ↓ Through reproduction (transfer of plasmids that contain antibiotic resistant genes) they pass on the alleles that confer the survival advantage to the next generation (and to
other bacteria)
Individuals with unfavourable phenotype decline in the population
↓ ↓ Over time and generations there is a shift in the allele frequencies and the associated phenotypes in the population, such that those with the resistant phenotype increase in frequency and those with the
non-resistant phenotype decrease in frequency.
2 Increased use of antibiotics exposes bacteria to the selection pressure, accelerating the process of natural selection that has led to increasing levels of antibiotic resistance. When new and more potent antibiotics are developed and applied, a bacterial mutation that confers resistance is passed to offspring (and to other bacteria through transfer of plasmids), leading to an entire population of resistant individuals. Failure to complete a course of antibiotics also contributes to the problem—taking only part of a course of antibiotics will be effective at destroying the most susceptible bacteria causing an infection, leaving any resistant individuals that may be present to increase in number before causing a relapse. Re-application of the same antibiotic will be less effective because the remaining population are resistant.
Worksheet 44: The truth of the matter—patterns in evolution 1 Correct order of responses: true, false, true, false, false, true, true, true, false, true
2 • Divergent evolution occurs when related species diverge from a common ancestral species.
• The presence of 13 different species of finches on the Galapagos Islands is understood to be an example of divergent evolution.
• Parallel evolution occurs when different but related species diverge from a common ancestral group and then independently evolve similar structural features.
• When paired chromosomes fail to separate during meiosis, the resulting offspring feature multiple sets of chromosomes. This is called polyploidy and is responsible for sudden speciation. Polyploidy is common is some plant groups.
Worksheet 45: Adaptive radiation—Darwin’s finches 1 Adaptive radiation is the rapid divergence of one or more species from an ancestral population.
2
3 a Seeds; Species A features a large, strong beak that is suitable for crushing large seeds.
b Insects; Species F beak is most similar to the beak of species B which is an insect eater.
4 • Ancestral mainland population included variation, e.g. in size and shape of beak.
• Ancestral population migrate to islands. Initially expect proportions of variants to be representative of original population.
• Different environmental pressures (food sources available on different islands) favour particular phenotypes, e.g. a large, strong beak adapted to crushing seeds is favoured on some islands, whereas a long, fine beak adapted to extracting nectar is favoured on other islands.
• Birds with phenotypes that confer a survival advantage are favoured on some islands, whereas different phenotypes are favoured on other islands. The most biologically fit individuals increase in number on each island, whereas less fit individuals leave less offspring and their numbers decline.
• Over time and many generations, distinct races appear on each of the islands.
• Cessation of gene flow between populations on the different islands means races become increasingly adapted to their particular environment, and increasingly different from one another.
• When gene flow is no longer possible between members of the different populations, speciation is said to have occurred.
Worksheet 46: Human evolution and interventions—crossword
Across 2 Oldest known hominid fossil, dated at about 6 million years old
4 Fully bipedal, human-like primates
6 Describes members of species in the Genus Homo that co-existed with Homo sapiens but became extinct about 30 000 years ago; fossils originally discovered in the Neander river valley in Germany
10 Practice of using fire to remove dense vegetation and promote new growth; used by Australian Aborigines
15 Late Palaeolithic (Stone Age, 40 000 years old) humans whose fossil remains show evidence of culture
16 Species name of most recently discovered humans whose fossil remains on the Indonesian island of Flores reveal complex culture
Down 1 Genus of robust hominids that used tools
2 Artificial selection, i.e. selecting only those organisms with the most desirable characteristics for breeding purposes
3 Technical term used to describe testing procedure to determine the presence or absence of genetic defects in IVF embryos before implanting
5 Class to which the four hominid genera belong
7 Genus of robust hominid that includes the famous ‘Lucy’ fossil
8 Species to which modern humans belong
9 Describes ‘giant’ animal species including mammals, reptiles and emu-like birds that became extinct in the last 35 000 years
11 Knowledge accumulated and passed from generation to generation through various forms of communication
12 Mobility that involves walking on two legs
13 Order of animals featuring grasping hands, bicuspid teeth, binocular vision, well-developed brain; includes monkeys, apes, humans
Worksheet 47: Fluorofish—a controversial application of gene transformation 1 Fluorescence gene isolated from jellyfish
↓
Specific gene promoters (skin, muscle) isolated from zebra fish
↓
Hybrid gene produced that is composed of zebra fish gene promoter sequence and jellyfish fluorescence gene
↓
Hybrid gene injected into zebra fish embryos by microinjection at early stage of development—one or two-cell stage
↓
Transgenic zebra fish allowed to develop
↓
Fluorescence observed in relevant differentiated tissue, e.g. skin tissue
2 The transgenic zebra fish will likely die as a result of predation—the fluorescence means it is not camouflaged in its natural environment.
3 Ethical issues include: unknown consequences of this kind of intervention for a species, especially if transgenic animals escape to wild populations; may be seen as ‘playing God’; animal rights issues.
4 Sheep have been successfully engineered in the UK to include a human gene that results in the production of a protein in sheep milk. This represents a potential treatment for the genetic disease cystic fibrosis.
GM cattle: include a human gene that results in production of milk that contains a protein that may be useful in treating multiple sclerosis.
Research into the development of GM cats that are hypo-allergenic.
Worksheet 48: Homo hobbit—the lost tribe of Flores 1 The fossil evidence of upright stance, bipedalism, flattened nose, and arms shorter than legs indicates that
Homo floresiensis was indeed a human species. Artefacts such as cooking utensils, stone tools and evidence of use of fire indicate relatively advanced intelligence and culture.
2 The general pattern observed in hominid evolution shows an increased brain-case size from older to more recent fossils, a pattern that suggests a larger brain together with increasing intelligence. Homo floresiensis was a species that stood at only 1 metre tall with a brain-case of only 380 cm3, and yet showed the hallmarks of advanced intelligence.
3 Homo sapiens and Homo floresiensis appear to share a common ancestor that diverged to yield different lines, one leading to Homo erectus and Homo floresiensis (which appear to be closely related) and the other giving rise to Homo heidelbergensis, from which Homo neanderthalensis and Homo sapiens evolved.
4 Possible geographical isolation of ancestral population on island (Flores) due to rise in sea levels. No gene flow with original population, together with unique environmental pressures over millennia, would steer island population towards adaptations that suit its unique environment. Population becomes increasingly different from the ancestral population, eventually evolving into distinct species.
