1. Speciation
1.1. sympatric speciation
1.1.1. results from polyploidy
1.1.1.1. occurs when organisms possess more than 2 of the haploid chromosome set
1.1.1.1.1. Autopolyploidy -an organism contains two or more complete sets of chromosome from two or more different species
1.1.1.1.2. Allopolyploidy -an organism contains two or more sets of chromosome, all derived from a single species
1.1.2. results from ecological isolation
1.1.2.1. due to occupying varying micro habitats within a niche
1.1.2.1.1. differing selection pressures (eg food) exist [see natural selection]
1.2. allopatric speciation
1.2.1. results from geographical isolation
1.2.1.1. physical barriers that prevent gene flow (reproductive isolation)
1.2.1.2. natural selection due to different selection pressures from environment
1.2.1.3. Genetic drift
2. Species concepts
2.1. Genetic species concept
2.1.1. A genetically distinct group of natural population of organisms that share a common gene pool
2.1.2. Deals with genetic isolation
2.1.3. Link to DNA structure and nucleotide sequence
2.2. Biological species concept
2.2.1. Defines a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are unable to produce viable, fertile offspring with members of other populations
2.2.2. Deals with reproductive isolation
2.2.3. Link to cell and nuclear division (homologous chromosomes and chromosome number)
2.3. Phylogenetic species concept
2.3.1. Defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life
2.4. Morphological species concept
2.4.1. Characterise a species by body shape and other structural features
2.4.2. Organisms are classified as the same species if their anatomical traits appear to be very similar
2.5. Ecological species concept
2.5.1. Views a species in terms of its ecological niche that is within its native environment, focusing on unique adaptations to particular roles in a biological community
2.5.2. Ecological niche is the unique set of habitat resources that a species requires, as well as its influence on the environment and other species
3. Microevolution
3.1. Why variation is important in natural selection
3.1.1. Provides basis for natural selection
3.1.1.1. In various climatic conditions due to change in abiotic factors e.g. temperature, rainfall, etc. through change in seasonal and geographical patterns
3.1.1.1.1. Link to anthropogenic climate change and effects on the environment
3.1.2. Increases genetic diversity
3.1.2.1. Variance of phenotypes
3.1.2.1.1. Upon exposure to drastic environmental changes, population is able to adapt
3.2. Role of natural selection in evolution
3.2.1. Organisms have great potential to reproduce
3.2.1.1. Overproduction of offspring could lead to exponential increase in population size
3.2.2. Constancy in numbers due to limited resources
3.2.2.1. However, size of most populations stay relatively constant
3.2.2.1.1. Many offspring die before they reach reproductive age
3.2.3. Struggle for existence as individuals are constantly competing with each other for limited resources
3.2.4. Variation within a population due to spontaneous mutations
3.2.5. Survival of the fittest by natural selection
3.2.5.1. Individuals with genetic variations best adapted to the environment are better able to survive and reproduce
3.2.5.1.1. They are selected for by the environment
3.2.6. Differential reproduction which leads to changes in allele frequencies
3.2.6.1. Those with selective advantage more likely to survive to maturity and reproduce
3.2.6.1.1. More likely to leave more offspring
3.2.7. Formation of a new species through reproductive/genetic isolation
3.2.7.1. Over many generations, with genetic isolation, reproductive isolation will occur
3.2.7.1.1. New species will form
3.3. How environmental factors act as forces of natural selection
3.3.1. Act as selection pressures
3.3.1.1. Specific phenotypes are better adapted and thus have a selective advantage, so it is selected for
3.3.1.1.1. Higher survival rate, will live to reproductive age
3.4. Populations are the smallest unit to evolve
3.4.1. evolutionary impact of natural selection is only apparent in the changes in a population of organisms over time
3.4.2. microevolution - change in allele frequencies in the gene pool of a POPULATION over generations
3.5. How genetic variation is preserved
3.5.1. Processes that CONTRIBUTE to genetic variation: - mutations to form new alleles - chromosomal abberations - crossing-over and independent assortment of homologous chromosomes during meiosis to form new combinations of existing alleles - sexual reproduction
3.5.1.1. MUTATIONS, CELL NUCLEAR DIVISION, INHERITANCE
3.5.2. Processes that REDUCE genetic variation: - genetic drift - natural selection (stabilising, directional selection)
3.5.3. Maintenance of genetic variation: - diploidy - balanced polymorphism
3.5.3.1. Diploidy: Recessive alleles (including harmful alleles) can be propagated in heterozygous individuals
3.5.3.2. Balanced polymorphism: Balancing selection to maintain 2 or more alleles at a locus OR to maintain 2 different phenotypic forms in a population to MAINTAIN GENETIC DIVERSITY
3.6. Linking Microevolution to Macroevolution
3.6.1. Macroevolution occurs as a result of microevolution and macroevolution cannot take place without microevolution
4. Reconstructing Phylogenetic Relationships
4.1. Molecular systematics- Analysis of genetic data to study and identify homology
4.1.1. Advantages
4.1.1.1. 1. Quantifiable 2. Genetic 3. Used w all organisms 4. Understanding of evolutionary relationships that cannot be determined by non molecular methods
4.1.1.1.1. Link to molecular techniques
4.1.2. DNA Sequence Comparison
4.1.2.1. Multiple sequence alignment using microsatellites as they are non coding regions or mitochondrial DNA
4.1.3. Amino Acid Sequence Comparison
4.1.3.1. Homologous proteins from different species may have polypeptide chains identical in length w variant/invariant residues
5. Phylogeny
5.1. Hypothesis about patterns of evolutionry relationship among species. Phylogenetic trees show a visual representation of a phylogeny to illustrate lineages and their evolutionary relationship
5.1.1. .
5.1.1.1. Monophyletic grouping: Includes an ancestral species and all descendants
5.1.1.2. Polyphyletic grouping: Several evolutionary lines that do not share same recent common ancestor
5.1.1.3. Paraphyletic grouping: includes an ancestral species+ some of the descendants
5.1.2. Character/Traits are important in the study of phylogeny as:
5.1.2.1. 1) These observations are used to infer pattern of ancestry and descent among populations and is represented in phylogenetic tree
5.1.2.2. 2) By mapping additional traits onto phylogeny created, study the sequence and timing of evolutionary events
6. Biological Classification of living organisms
6.1. the act of systematically arranging organisms into groups based on shared characteristics
6.1.1. vital in the study and referencing of organisms
6.1.2. reveals evolutionary relationships, link to phylogeny