YIJC [H2] CI4_Evolution (N)(S)

2025 JC2 BIOLOGY LECTURE NOTES CORE IDEA 4: BIOLOGICAL EVOLUTION TOPIC: BIOLOGICAL EVOLUTION Learning Outcomes: (a) Explain why variation (as a result of mutation, meiosis and sexual reproduction) is important in natural selection. (b) Explain, with examples, how environmental factors act as forces of natural selection. (c) Explain the role of natural selection in evolution. (d) Explain why the population is the smallest unit that can evolve. (e) Explain how genetic variation (including harmful recessive alleles) may be preserved in a natural population. (f) define biological evolution as descent with modification and explain the link between micro- evolution and macro-evolution (g) explain how evidence based on homologies identified in biochemical data (molecular homologies) and the fossil record (anatomical homologies), together with biogeography, supports Darwin’s theory of evolution (h) explain the various concepts of the species (biological, ecological, morphological, genetic and phylogenetic concepts) (i) define biological classification as the organisation of species according to shared characteristics and describe how evolutionary relationship is established (j) explain how new species are formed with respect to geographical isolation (allopatric speciation) and behavioural or physiological isolation within the same geographical location (sympatric speciation) (k) define phylogeny as the organisation of species to show their evolutionary relationships (l) explain the importance of the use of genome sequences in reconstructing phylogenetic relationships and state the advantages of molecular methods, including multiple sequence alignment (nucleotide and amino acid), in classifying organisms. References: Campbell and Reece. Biology. (11th edition). Chapter 23: Microevolution, P. 540 – 559, Chapter 21: How Evolution Works, P. 504 – 521, Chapter 22: Phylogenetic Reconstruction, P. 523 – 542, Chapter 24: Species and Speciation, P. 564 – 580, Chapter 25: Macroevolution, P. 583 – 607 (or any correspponding chapters in other editions) A Bridge to O Level Biology (6093 syllabus) You should have learnt to: (j) describe the difference between continuous and discontinuous variation and give examples of each (k) state that variation and competition lead to differential survival of, and reproduction by, those organisms best fitted to the environment (l) give examples of environmental factors that act as forces of natural selection (m) explain the role of natural selection as a possible mechanism for evolution (n) give examples of artificial selection such as in the production of economically important plants and animals H2

2 1 INTRODUCTION  Evolution refers to a process of descent with modification from a common ancestor. It involves a change in allele frequencies within a population over generations.  Allele frequency refers to the relative proportion of the alleles of a gene prese