IBDP Biology Chapter 5 Notes



These notes have specially been curated by expert teachers to simplify and enlighten concepts given in IB Biology HL. The notes are comprehensive in nature and are sufficient to study the chapter in depth and one need not look for other resources beyond the notes provided on our website which can be accessed for free. The notes for Cell Biology IBDP HL are available on our official website and can be downloaded for free. You are one click away from obtaining all that you need to score well in IB Biology HL.

The material made available on Tychr’s website is available for all IBDP subjects and is specially curated after an extensive amount of effort to ensure that the notes are in consonance with the IB curriculum and are an amalgamation from various textbooks prescribed by the IBO.Students often face a challenge understanding concepts, especially concepts that are new and tricky. These IB Biology Notes will help the student cover the chapter of Cell Biology entirely while explaining each and every concept in a detailed and easy way.

In this chapter, we link evolution, natural selection, biodiversity and cladistics. Evolution is the change in the heritable characteristics of a population which leads to the speciation (emergence of new species; populations can no longer interbreed). Evolution is supported by fossil records, radioactive dating, animal breeding and presence of homologous structures. Adaptive radiation is the development of different functional structures from a common ancestral form. Then we shift the focus to natural selection where better adapted individuals get selected and hence are able to continue reproducing and continue the existence of their species.

These adaptations are brought about by mutations which cause variations in the gene pool, e.g. survival of antibiotic resistant bacteria. Then we discuss classification of biodiversity through binomial nomenclature ( genus name + species name) which ensures an unique and universally understandable name for every organism. These rules for naming are given by ICZN ( animals) and ICBN ( plants). We also examine domains of living organisms followed by the 7 principal taxa ( kingdom, phylum, class, order, family, genus, species). Then we look into the examples of animal and plant phyla with an in-depth view on the phylum vertebrata of the animal kingdom and its classes( fish, amphibians, reptiles, birds, and mammals).

To the end we dive into Cladistics which is the natural classification which classifies taxa together according to the apomorphic traits (more recently evolved characters). Clade is the group of organisms arising from a common ancestor on basis of biochemical evidences (mostly amino acid sequence) and node is the point of divergence.