2016 H2 Diversity and Evolution Lecture Notes Updated

NANYANG JUNIOR COLLEGE H2 Biology Diversity and Evolution J2/2016 1 TOPIC Q : DIVERSITY AND EVOLUTION Learning Outcome Candidates should be able to Core Topic 7 – Diversity and Evolution (a) Explain the binomial nomenclature of a species and hierarchical classification. (b) Describe the classification of species into taxonomic gr oups (genus, family, order, class, phylum, kingdom) and explain various concepts of the species. (Knowledge of biological ecological, morphological, phylogenetic concepts of species is required.) (c) Explain how species are formed with reference to geographica l isolation, physiological isolation and behavioural isolation. (d) Explain the relationship between classification and phylogeny. (Evolutionary relationships between organisms should be reflected in systematic classification.) Classification is the organisation of species according to particular characteristics. Classification may not take into consideration evolutionary relationship between the species. Phylogeny is the organisation of species according to particular characteristics which takes into consider ation the evolutionary relationship between the species. (e) Explain why variation is important in selection. (f) Explain, with examples, how environmental factors act as forces of natural selection. (g) Explain how natural selection may bring about evolution. (h) Explain why the population is the smallest unit that can evolve. (i) Explain how homology (anatomical, embryological and molecular) supports Darwin’s theory of natural selection (with emphasis on descent with modification). (j) Explain how biogeography and the fossil re cord support evolutionary deductions based on homologies. (k) Explain the importance of the use of genome sequences in reconstructing phylogenetic relationships and state the advantages of molecular (nucleotide and amino acid sequences) methods in classifying organisms. (l) Explain how genetic variation (including recessive alleles) may be preserved in a natural population. (m) Briefly describe the neutral theory of molecular evolution in terms of mutations producing new molecular variants which are selectively neutral . (Knowledge of genetic drift and molecular clock is required.) Use the knowledge gained in these sections in new situations or to solve related problems.

NANYANG JUNIOR COLLEGE H2 Biology Diversity and Evolution J2/2016 2 Content Outline 1. Introduction 2. Classification of Organisms (a) Hierarchical classification (b) Binomial nomenclature (c) Phylogeny (d) Molecular methods of classification 3. The Various Concepts of Species (a) Biological concept of species (b) Ecological concept of species (c) Morphological concept of species (d) Phylogenetic concept of species 4. Natural Selection and Evolution (a) Darwin’s Theory of Evolution via Natural Selection (b) Forces of natural selection (c) Isolation mechanisms for speciation (d) The Neo-Darwinian revolution 5. Evidence of Evolution (a) Biogeography (b) Fossil records (c) Homology 6. Preservation of Genetic Variation in Natural Populations (a) Diploidy (b) Balanced polymorphism (c) Neutral mutations 7. The Neutral Theory of Molecular Evolution (a) Genetic drift (b) Molecular clock References 1. Campbell N. A. and Reece J.B. (2008). Biology. Chapter 21-26. Eighth Edition. Pearson Education, Inc. 2. Brooker R.J. et. al. (2008). Biology. Chapter 23-26. First Edition. The McGraw-Hill Companies. 3. Kardong KV. (2005). An Introduction to Biological Evolution. Chapter 1, 6,-8. 1st Edition. McGraw Hill. 4. Strickberger MV. (2000). Evolution. Chapter 11-12. Third Edition. Jones & Bartlett Publishers.

NANYANG JUNIOR COLLEGE H2 Biology Diversity and Evolution J2/2016 3 1. Introduction In order to make sense of the diversity of organisms, it is necessary to group similar organisms together and organiz e these groups in a non -overlapping hierarchical arrangement. At the lowest level of the hierarchy, the organisms in each group form a species. There are various concepts of species that have been adopted to classify organisms with highly similar characteristics as a single species. It is through the understanding of such diversity of organisms that we appreciat e how each of these species has evolved. Charles Darwin’s Theory of Evolution via Natural Selection has been widely accepted by scientists across the world. Several pieces of evidence have been put forth to support his theory. However, his theory is still being challenged even till this day. Recent advances in molecular Biology have since supported the Neutral Theory of Molecular Evolution, which is seen as a complement to Darwin’s theory. 2. Classification of Organisms Systematics is the science of cl assification. It is defined as the study of diversity of organisms and all their comparative and evolutionary relationships. Systematists use data ranging from fossils to molecules and genes to infer evolutionary relationships. Taxonomy is the science con cerned with the identification, classification and nomenclature of organisms. Carolus Linnaeus (1748) developed a system of classifying every known organism in his time. The system is based on creating and differentiating organisms in terms of structural similarities and differences. With improvements in science and technology, many other similarities and differences, such as embryological and molecular relationships, are also taken into consideration. Thus there are two ways in classifying organisms: (a) Hierarchical classification (b) Phylogeny

NANYANG JUNIOR COLLEGE H2 Biology Diversity and Evolution J2/2016 4 (a) Hierarchical classification Classification is the organisation of species according to particular characteristics. Classification may not take into consideration evolutionary relationship between the species. A common type of classification is phenotypic classification:  It is concerned with grouping individuals species into phenotypic classes based on the morphology of organisms.  However, phenotypic similarities and evolutionary relationships do not always correspond with each other due to:  complex relationship between phenotype to genotype  occurrences of convergent evolution  variations between lineages in rates and modes of phenotypic evolutionary change Hierarchical classification refers the grouping of organi sms into levels of increasingly inclusive categories. A category in any rank unites groups in the level below it , based on shared characteristics. There are several variations to the classification of life. Among them are:  The two -empire system, with to p-level groupings of Prokaryota (or Monera) and Eukaryota empires.  The five-kingdom system with top-level groupings of Protista, Monera, Fungi, Plantae, and Animalia.  The most recent three-domain system, introduced by Carl Woese in 1990, with top - level groupings of Archaea, Eubacteria, and Eukaryota domains. Table of the different classification systems

NANYANG JUNIOR COLLEGE H2 Biology Diversity and Evolution J2/2016 5 In the three-domain / Linnaean system of classification, there is a hierarchy of designation, of which the genera and species denominations are at the bottom. This system, places related genera in the same family, families into order, orders into class, classes into phylum, phyla into kingdom, and more recently, kingdoms into domain. The named taxonomic unit at any level of the hierarchy is called a taxon (plural, taxa). Linnaean classification At each level, or rank, species are placed in groups within more inclusive groups. Domain Kingdom Phylum Class Order Family Genus Species Fun mnemonics to help you remember the hierarchy: Dear King Philip Came Over For Good Soup

NANYANG JUNIOR COLLEGE H2 Biology Diversity and