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NCEA lvl 3 Evolution
3.5 Evolution
| Question | Answer |
|---|---|
| Why does the genotype (genetic makeup) of indivuals vary? | Independent assortment of genes as homologous chromosomes seperate and recombine during meiosis; crossing over and recombination, mutations and random fertilisation of gametes. |
| What is a gene pool called? | It is the genetic makeup of a population |
| How does changes in the gene pool occur? | It occurs because of mutation, migration, genetic dtift(change by chance, including founder and bottleneck effects) and natural selection. |
| What is speciation? | It is the formation of a new species. |
| What is a species? | A species is a group of organisms that normally interbreed in the natural environment to produce fertile offspring.Species exist as populations that have the same gene pool. |
| What is natural selection? | It is the process in which heritable traits, that make it likely for an organism to survive long enough to reproduce,become more common over successive generations of a population. |
| What is sexual selection? | Males/females compete for partners with the heritable characteristics of the 'winners' being passed on. |
| What are the three modes of natural selection? | Three modes of selection occur in populations - stabilising, disruptive and directional. |
| What is stabilsing selection? | In stabilsing selection extreme phenotypes are selected against and average phenotypes are selected for |
| What is disruptive selection? | In disruptive selection, individuals at both extremes of the distribution are selected for simultaneously. Average phenotypes are at a disadvantage and are selected against. |
| What is directional selection? | In directional selection, a single phenotype is selected for and the allele frequency continuously shifts in one direction. |
| What is a population? | It is a group of organisms of one species living in the same geographic area |
| What is a deme? | It is a local population that has limited gene flow with members of the larger population.Location natural selection pressures mean that the phenotypic features of one deme may differ from those of another. |
| what is a cline? | It is a pattern of variation between individuals where there is a continyous increase or decrease in some phenotypic characteristic between adjacent populations. |
| What is genetic drift? | Change in the relative frequency which an allele occurs in a population resulting from the fact that alleles occur in offspring at random and because of the role chance plays in determining whether an individual dies or survives and reproduces. |
| When do population bottlenecks occur? | Occur's when a population’s size is reduced for at least one generation. Because genetic drift acts more quickly to reduce genetic variation in small populations, undergoing a bottleneck can reduce a population’s genetic variation significantly. |
| What is the founder effect? | It is when a new population formed from a few original 'founders' is very small,the alleles present and their frequency may not be representative of the parent population.There is much inbreeding and limited gene pool. |
| What is genetic equilibrium? | Describes a population when the frequencies of alleles and genotypes in a population do not vary from one generation to the next. |
| What is an isolating mechanism? | An isolating mechanism is any factor that stops two species from interbreeding - a barrier to gene flow. |
| What are prezygotic mechanisms? | Prezygotic isolation can occur either before mating (pre-mating barriers) or after mating (post-mating barriers). Prezygotic (before fertilised egg) mechanisms act BEFORE fertilisation. |
| What are examples of pre mating barriers? | Geographic isolation, habitat (ecological) isolation, temporal (seasonal) isolation, behavioural isolation and structural (anatomical) isolation. |
| What is geographic isolation? | Physical barriers seperate populations e.g.when metling ice and a rise in sea level separated NZ into North and South Islands two genetically isolated populations of birds were produced from one ancestral population. |
| What is Habitat (ecological) isolation? | Populations occur in different habitats but in the same region e.g. herbivorous insects from two populations feed and mate on different host plants. |
| What is temporal (seasonal) isolation? | Mating or flowering occurs at different times or different seasons.E.g. Silver pine sheds pollen in October while Rimu sheds pollen in mid November |
| What is behavioural isolation? | Courtship and mating behaviours are different. |
| What is structural (anatomical) isolation? | Physical non-correspondence of reproductive parts.Mating takes place in insects but males cannot transfer sperm to females because sex organs do not fit together. |
| What is an example of Post-making barriers? | Gene incompatibility, sperm cannot fertilise eggs of a different species.Male gametes are transferred but sperm do not penetrate the egg surface |
| What are examples of Post zygotic mechanisms? | Hybrid inviability, hybrid sterility, hybrid breakdown. |
| What is hybrid inviability? | Some species that do not normally interbreed occasionally do. However the young die at some point early in their development. |
| What is hybrid sterility? | The offspring reach maturity but are infertile e.g the mule is a hybrid between a donkey (2N=62) and a horse (2N=64. The mule has 63 chromosomes and is infertile. |
| What is hybrid breakdown? | The first generation (F1) is fertile but the second (F2) generation is infertile e.g. common in plants, hybrids between cotton species. |
| What is allopatric speciation? | Allopatric speciation is speciation involving a period of geographic separation. |
| How does Allopatric speciation occur? | A barrier separates the population and prevents them from exchanging DNA with each other.They accumulate genetic differences overtime because of nat selection, new mutations, genetic drift and the founder effect. |
| What is sympatric speciation? | It is the formation of a species from a single ancestral species while both species occupy the same geographical location? |
| How does sympatric speciation occur? | It involves genetic polymorphism, the formation of a polyploidy,able to breed only with other individuals.Separated from the parent species by a reproductive isolation mechanism, formation of polyploidy species represents instant speciation. |
| What is convergent evolution? | Species have different ancestral starting points, but they evolve similar adaptations because they occupy similar ecological niches and therefore have similar selection pressures acting on them.They have adaptations that perform the same/similar structure |
| What is divergent evolution? | The diversification of a single common ancestral species into two or more species. Adaptive radiation is a type of this form of evolution. |
| What is adaptive radiation? | The relatively fast evolution of many species from a single common ancestor to fill a variety of different ecological niches, often in different geographic areas. |
| What is co-evolution? | This is when two or more species each have an effect on the other's evolution. It is more likely to happen when different species interact with one another. |
| What is gradualism? | This model describes the rate of evolutionary change. It proposes that there is a slow, constant rate of change in species overtime in response to various selection pressures. This is shown by transition forms seen in fossil records. |
| What is punctuated equilibrium? | Very long periods of stasis brought about by stabilising selection when there is hardly any evolutionary change, followed by short bursts of different, unrelated species. |
| What is extinction? | Species have a lifecycle that starts within a period of increasing genetic variation and range.The species separates into a variety of habitats/may become a number of subspecies/new species.Eventually species face decreased genetic diversity and numbers. |
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BlahForever
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