Title
Demonstrate understanding of genetic variation and change
Date version published
17 November 2011
This achievement standard involves demonstrating understanding of genetic variation and change.
Achievement Criteria:
Achievement
· Demonstrate understanding of genetic variation and change.
Achievement with Merit
· Demonstrate in-depth understanding of genetic variation and change.
Achievement with Excellence
· Demonstrate comprehensive understanding of genetic variation and change.
Explanatory Notes:
1 This achievement standard is derived from The New Zealand Curriculum, Learning Media, Ministry of Education, 2007, Level 7. It is aligned with the following achievement objective in the Living World strand:
Ecology and Evolution
· Explain how the interaction between ecological factors and natural selection leads to genetic changes within populations
and is related to the material in the Teaching and Learning Guide for Biology, Ministry of Education, 2010 at http://seniorsecondary.tki.org.nz.
2 Demonstrate understanding involves defining, using annotated diagrams or models to describe, and describing characteristics of, or providing an account of, genetic variation and change.
Demonstrate in-depth understanding involves providing reasons as to how or why genetic variation and change occurs.
Demonstrate comprehensive understanding involves linking biological ideas about genetic variation and change. The discussion of ideas may involve justifying, relating, evaluating, comparing and contrasting, or analysing.
3 Genetic variation and change involves the following concepts:
· sources of variation within a gene pool
· factors that cause changes to the allele frequency in a gene pool.
4 Biological ideas and processes relating to sources of variation within a gene pool are selected from:
· mutation as a source of new alleles
· independent assortment, segregation and crossing over during meiosis
· monohybrid inheritance to show the effect of co-dominance, incomplete dominance, lethal alleles, and multiple alleles
· dihybrid inheritance with complete dominance
· the effect of crossing over and linked genes on dihybrid inheritance.
5 Biological ideas and processes relating to factors affecting allele frequencies in a gene pool are selected from:
· natural selection
· migration
· genetic drift.
6 Assessment Specifications for this achievement standard can be accessed through the Biology Resources page found at http://www.nzqa.govt.nz/qualifications-standards/qualifications/ncea/subjects/.
Key Words: These are the words that you are expected to understand when used in questions and be able to use in your answers.
Core Vocabulary:
Adaptation - the process of change by which an organism or species becomes better suited to its environment.
· Allele frequency - is a measure of the relative frequency of an allele on a genetic locus in a population. Usually it is expressed as a proportion or a percentage. In population genetics, allele frequencies show the genetic diversity of a species population or equivalently the richness of its gene pool.
· Co-dominance - a condition in which the alleles of a gene pair in a heterozygote are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive.
· Complete dominance - a kind of dominance wherein the dominant allele completely masks the effect of the recessive allele in heterozygous condition.
· Dihybrid inheritance - is a cross between F1 offspring (first-generation offspring) of two individuals that differ in two traits of particular interest.
· Directional selection - is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.
· Disruptive selection - also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups.
· Emigration - the act of leaving one's own habitat or area to settle permanently in another; moving away.
· Evolution - The change in genetic composition of a population over successive generations, which may be caused by natural selection, inbreeding, hybridization, or mutation.
· Gene pool - The total number of genes of every individual in an interbreeding population.
· Gene flow - is the transfer of alleles from one population to another population through immigration of individuals. In this example, one of the birds from population A immigrates to population B, which has fewer of the dominant alleles, and through mating incorporates its alleles into the other population.
· Gene frequency - is the proportion of a particular allele (variant of a gene) among all allele copies being considered. It can be formally defined as the percentage of all alleles at a given locus in a population gene pool represented by a particular allele.
· Genetic drift - random changes in the frequency of alleles in a gene pool, usually of small populations. The population contracted to just four random survivors, a phenomenon known as population bottleneck. In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.
· Genetic equilibrium - a condition where a gene pool is not changing in frequency because the evolutionary forces acting upon the allele are equal, thus, resulting in a population to not evolve even after several generations.
· Immigration - the action of coming to live permanently in a foreign area or habitat.
· Incomplete dominance - is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes.
· Independent assortment - now called Mendel's law of independent assortment, states that allele pairs separate independently during the formation of gametes. This means that traits are transmitted to offspring independently of one another.
· Lethal alleles - can code for either dominant or recessive traits, but they do not actually cause death unless an organism carries two copies of the lethal allele. Examples of human diseases caused by recessive lethal alleles include cystic fibrosis, sickle-cell anemia, and achondroplasia.
· Linked genes - Genes that are inherited together with the other gene(s) as they are located on the same chromosome. When a pair or set of genes are on the same chromosome, they are usually inherited together or as a single unit. For example, in fruit flies the genes for eye color and the genes for wing length are on the same chromosome, thus are inherited together.
· Mate selection - or intersexual selection, is an evolutionary process in which selection of a mate depends on the attractiveness of his or her traits. It is one of two components of sexual selection (the other being intrasexual selection).
· Migration - seasonal or permanent movement of animals from one region to another.
· Multiple alleles - a series of three or more alternative or allelic forms of a gene, only two of which can exist in any normal, diploid individual.
· Natural selection - The process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characters in increasing numbers to succeeding generations while those less adapted tend to be eliminated.
· Population - a community of animals, plants, or humans among whose members interbreeding occurs.
· Recombination - The exchange of a segment of DNA between two homologous chromosomes during meiosis leading to a novel combination of genetic material in the offspring. Crossing over is the swapping of genetic material that occurs in the germ line.
· Segregation - now called Mendel's law of segregation, states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.
· Selection pressure - An agent of differential mortality or fertility that tends to make a population change genetically.
· Speciation - The evolutionary formation of new biological species, usually by the division of a single species into two or more genetically distinct ones. The formation of new biological species by the development or branching of one species into two or more genetically distinct ones.
· Species - a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial, e.g. Homo sapiens.
· Stabilising selection - a type of selection that removes individuals from both ends of a phenotypic distribution thus maintaining the same distribution mean.
· Variation - In genetic variation, the genes of organisms within a population change. Gene alleles determine distinct traits that can be passed on from parents to offspring. Gene variation is important to the process of natural selection.
At the end of this unit of work you should be able to use the core knowledge listed in the statements below to describe, explain and discuss aspects of evolution. Questions may be presented to you in unfamiliar situations that will require you to recognise and link these ideas together.
1. Recognise evolution as a process of change in allele frequency.
2. Describe the key ideas that underpin the theory of evolution.
3. Identify and explain the 4 sources of variation within a gene pool. These include: mutation, crossing over, independent assortment and random fertilisation.
4. Define independent assortment, segregation and crossing over during meiosis.
5. Identify and explain the 5 factors that cause changes to the allele frequency in a gene pool. These include: migration, mutation, natural selection, mate selection and genetic drift.
6. Recognise mutation as a source of new alleles and explain what mutations can be inherited and which can be established in a population.
7. Explain monohybrid inheritance to show the effect of co-dominance; incomplete dominance; lethal alleles and multiple alleles.
8. Explain dihybrid inheritance with complete dominance.
9. Understand the effect of crossing over and linked genes on dihybrid inheritance.
10. Discuss how to do a test cross for dihybrid inheritance.
11. Communicate ideas clearly using the scientific terminology relevant to this topic.
In addition the following knowledge will contribute to your understanding of the core knowledge
12. Be able to calculate allele frequency for given populations.
13. Define artificial selection. Describe the basis of the principles of artificial selection and link to human needs or demands.
14. Describe evidence for evolution.
Demonstrate understanding of genetic variation and change
Date version published
17 November 2011
This achievement standard involves demonstrating understanding of genetic variation and change.
Achievement Criteria:
Achievement
· Demonstrate understanding of genetic variation and change.
Achievement with Merit
· Demonstrate in-depth understanding of genetic variation and change.
Achievement with Excellence
· Demonstrate comprehensive understanding of genetic variation and change.
Explanatory Notes:
1 This achievement standard is derived from The New Zealand Curriculum, Learning Media, Ministry of Education, 2007, Level 7. It is aligned with the following achievement objective in the Living World strand:
Ecology and Evolution
· Explain how the interaction between ecological factors and natural selection leads to genetic changes within populations
and is related to the material in the Teaching and Learning Guide for Biology, Ministry of Education, 2010 at http://seniorsecondary.tki.org.nz.
2 Demonstrate understanding involves defining, using annotated diagrams or models to describe, and describing characteristics of, or providing an account of, genetic variation and change.
Demonstrate in-depth understanding involves providing reasons as to how or why genetic variation and change occurs.
Demonstrate comprehensive understanding involves linking biological ideas about genetic variation and change. The discussion of ideas may involve justifying, relating, evaluating, comparing and contrasting, or analysing.
3 Genetic variation and change involves the following concepts:
· sources of variation within a gene pool
· factors that cause changes to the allele frequency in a gene pool.
4 Biological ideas and processes relating to sources of variation within a gene pool are selected from:
· mutation as a source of new alleles
· independent assortment, segregation and crossing over during meiosis
· monohybrid inheritance to show the effect of co-dominance, incomplete dominance, lethal alleles, and multiple alleles
· dihybrid inheritance with complete dominance
· the effect of crossing over and linked genes on dihybrid inheritance.
5 Biological ideas and processes relating to factors affecting allele frequencies in a gene pool are selected from:
· natural selection
· migration
· genetic drift.
6 Assessment Specifications for this achievement standard can be accessed through the Biology Resources page found at http://www.nzqa.govt.nz/qualifications-standards/qualifications/ncea/subjects/.
Key Words: These are the words that you are expected to understand when used in questions and be able to use in your answers.
Core Vocabulary:
Adaptation - the process of change by which an organism or species becomes better suited to its environment.
· Allele frequency - is a measure of the relative frequency of an allele on a genetic locus in a population. Usually it is expressed as a proportion or a percentage. In population genetics, allele frequencies show the genetic diversity of a species population or equivalently the richness of its gene pool.
· Co-dominance - a condition in which the alleles of a gene pair in a heterozygote are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive.
· Complete dominance - a kind of dominance wherein the dominant allele completely masks the effect of the recessive allele in heterozygous condition.
· Dihybrid inheritance - is a cross between F1 offspring (first-generation offspring) of two individuals that differ in two traits of particular interest.
· Directional selection - is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.
· Disruptive selection - also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups.
· Emigration - the act of leaving one's own habitat or area to settle permanently in another; moving away.
· Evolution - The change in genetic composition of a population over successive generations, which may be caused by natural selection, inbreeding, hybridization, or mutation.
· Gene pool - The total number of genes of every individual in an interbreeding population.
· Gene flow - is the transfer of alleles from one population to another population through immigration of individuals. In this example, one of the birds from population A immigrates to population B, which has fewer of the dominant alleles, and through mating incorporates its alleles into the other population.
· Gene frequency - is the proportion of a particular allele (variant of a gene) among all allele copies being considered. It can be formally defined as the percentage of all alleles at a given locus in a population gene pool represented by a particular allele.
· Genetic drift - random changes in the frequency of alleles in a gene pool, usually of small populations. The population contracted to just four random survivors, a phenomenon known as population bottleneck. In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.
· Genetic equilibrium - a condition where a gene pool is not changing in frequency because the evolutionary forces acting upon the allele are equal, thus, resulting in a population to not evolve even after several generations.
· Immigration - the action of coming to live permanently in a foreign area or habitat.
· Incomplete dominance - is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes.
· Independent assortment - now called Mendel's law of independent assortment, states that allele pairs separate independently during the formation of gametes. This means that traits are transmitted to offspring independently of one another.
· Lethal alleles - can code for either dominant or recessive traits, but they do not actually cause death unless an organism carries two copies of the lethal allele. Examples of human diseases caused by recessive lethal alleles include cystic fibrosis, sickle-cell anemia, and achondroplasia.
· Linked genes - Genes that are inherited together with the other gene(s) as they are located on the same chromosome. When a pair or set of genes are on the same chromosome, they are usually inherited together or as a single unit. For example, in fruit flies the genes for eye color and the genes for wing length are on the same chromosome, thus are inherited together.
· Mate selection - or intersexual selection, is an evolutionary process in which selection of a mate depends on the attractiveness of his or her traits. It is one of two components of sexual selection (the other being intrasexual selection).
· Migration - seasonal or permanent movement of animals from one region to another.
· Multiple alleles - a series of three or more alternative or allelic forms of a gene, only two of which can exist in any normal, diploid individual.
· Natural selection - The process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characters in increasing numbers to succeeding generations while those less adapted tend to be eliminated.
· Population - a community of animals, plants, or humans among whose members interbreeding occurs.
· Recombination - The exchange of a segment of DNA between two homologous chromosomes during meiosis leading to a novel combination of genetic material in the offspring. Crossing over is the swapping of genetic material that occurs in the germ line.
· Segregation - now called Mendel's law of segregation, states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.
· Selection pressure - An agent of differential mortality or fertility that tends to make a population change genetically.
· Speciation - The evolutionary formation of new biological species, usually by the division of a single species into two or more genetically distinct ones. The formation of new biological species by the development or branching of one species into two or more genetically distinct ones.
· Species - a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial, e.g. Homo sapiens.
· Stabilising selection - a type of selection that removes individuals from both ends of a phenotypic distribution thus maintaining the same distribution mean.
· Variation - In genetic variation, the genes of organisms within a population change. Gene alleles determine distinct traits that can be passed on from parents to offspring. Gene variation is important to the process of natural selection.
At the end of this unit of work you should be able to use the core knowledge listed in the statements below to describe, explain and discuss aspects of evolution. Questions may be presented to you in unfamiliar situations that will require you to recognise and link these ideas together.
1. Recognise evolution as a process of change in allele frequency.
2. Describe the key ideas that underpin the theory of evolution.
3. Identify and explain the 4 sources of variation within a gene pool. These include: mutation, crossing over, independent assortment and random fertilisation.
4. Define independent assortment, segregation and crossing over during meiosis.
5. Identify and explain the 5 factors that cause changes to the allele frequency in a gene pool. These include: migration, mutation, natural selection, mate selection and genetic drift.
6. Recognise mutation as a source of new alleles and explain what mutations can be inherited and which can be established in a population.
7. Explain monohybrid inheritance to show the effect of co-dominance; incomplete dominance; lethal alleles and multiple alleles.
8. Explain dihybrid inheritance with complete dominance.
9. Understand the effect of crossing over and linked genes on dihybrid inheritance.
10. Discuss how to do a test cross for dihybrid inheritance.
11. Communicate ideas clearly using the scientific terminology relevant to this topic.
In addition the following knowledge will contribute to your understanding of the core knowledge
12. Be able to calculate allele frequency for given populations.
13. Define artificial selection. Describe the basis of the principles of artificial selection and link to human needs or demands.
14. Describe evidence for evolution.