5. Evolution and biodiversity

5. Evolution and biodiversity

5.1 Evidence for evolution

Nature of science:

  • Looking for patterns, trends and discrepancies - there are common features in the bone structure of vertebrate limbs despite their varied use.

Understandings:

  • Evolution occurs when heritable characteristics of a species change.

  • The fossil record provides evidence for evolution.

  • Selective breeding of domesticated animals shows that artificial selection can cause evolution.

  • Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function.

  • Populations of a species can gradually diverge into separate species by evolution.

  • Continuous variation across the geographical range of related populations matches the concept of gradual divergence.

Applications and skills:

  • Application: Development of melanistic insects in polluted areas.

  • Application: Comparison of the pentadactyl limb of mammals, birds, amphibians and reptiles with different methods of locomotion.

5.2 Natural selection

Nature of science:

  • Use theories to explain natural phenomena - the theory of evolution by natural selection can explain the development of antibiotic resistance in bacteria.

Understandings:

  • Natural selection can only occur if there is variation among members of the same species.

  • Mutation, meiosis and sexual reproduction cause variation between individuals in a species.

  • Adaptations are characteristics that make an individual suited to its environment and way of life.

  • Species tend to produce more offspring than the environment can support.

  • Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.

  • Individuals that reproduce pass on characteristics to their offspring.

  • Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species.

Applications and skills:

  • Application: Changes in beaks of finches on Daphne Major.

  • Application: Evolution of antibiotic resistance in bacteria.

5.3 Classification of biodiversity

Nature of science:

  • Cooperation and collaboration between groups of scientists - scientists use the binomial system to identify a species rather than the many different local names.

Understandings:

  • The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses.

  • When species are discovered they are given scientific names using the binomial system.

  • Taxonomists classify species using a hierarchy of taxa.

  • All organisms are classified into three domains.

  • The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species.

  • In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.

  • Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species.

  • Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group.

Applications and skills:

  • Application: Classification of one plant and one animal species from domain to species level.

  • Application: Recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta.

  • Application: Recognition features of porifera, cnidaria, platyhelmintha, annelida, mollusca, arthropoda and chordata.

  • Application: Recognition of features of birds, mammals, amphibians, reptiles and fish.

  • Skill: Construction of dichotomous keys for use in identifying specimens.

5.4 Cladistics

Nature of science:

  • Falsification of theories with one theory being superseded by another - plant families have been reclassified as a result of evidence from cladistics.

Understandings:

  • A clade is a group of organisms that have evolved from a common ancestor.

  • Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein.

  • Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor.

  • Traits can be analogous or homologous.

  • Cladograms are tree diagrams that show the most probable sequence of divergence in clades.

  • Evidence from cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species.

Applications and skills:

  • Application: Cladograms including humans and other primates.

  • Application: Reclassification of the figwort family using evidence from cladistics.

  • Skill: Analysis of cladograms to deduce evolutionary relationships.

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