BLG1502 ASSIGNMENT 02 (Complete solutions)

QUESTION 1 1.1) Monophyletic 1.2) Animal 1.3) Horizontal gene transfer 1.4) Photoautotroph 1.5) Parasitism 1.6) Euglenids 1.7) Dinoflagellates 1.8) Sporopollenin 1.9) Peristome 1.10) Cycadophyta QUESTION 2 2.1) Phylogeny refers to the evolutionary relationship/history of a species or a group of species, particularly the differences and similarities between these groups of organisms. Biologists use systematics which is the study of identification, classification, ecology and histories of organisms to determine and classify evolutionary relationships and represent this information on a tree called a phylogeny tree. Phylogeny is based on the evidence that all organisms are related by a common descent. Evidence for phylogeny comes from palaeontology, comparative anatomy and DNA sequence analysis. 2.2) A monophyletic (single-tribe) group is a group which consists of an ancestral species and all its descendants, a monophyletic group is also called a clade. In contrast a paraphyletic (beside-the-tribe) group is a group which consists of an ancestral species and some, but not all its descendants. 2.3) Homology refers to similarity in characteristics resulting from a shared ancestry. Homology results from divergent evolution, vertebrate limbs are an example of homology. Whereas homoplasy is defined as a similar (analogous) structure or molecular sequence that has evolved independently in two species (does not emerge from a common ancestor). Homoplasy results from convergent evolution, an example would be the wings of a bat and bird. 2.4) Orthologous genes are homologous genes that diverged after evolution and gives rise to different species (speciation), they are found in different species and their divergence traces back to the speciation events that produced the species. In contrast, paralogous genes are homologous genes that have diverged within one species. Unlike orthologous genes, a paralogous gene is a new gene that holds a new function. Paralogous genes result from gene duplication, hence multiple copies of these genes have diverged from one another within a species. Orthologous genes can only diverge after speciation has taken place, however paralogous genes can diverge within a species as they are present in more than one copy of the genome. 2.5) The tree of life consists of three major branches namely – Bacteria, Archaea and Eukaryotes. The domain bacteria consist of unicellular organisms lacking a nucleus. Archaea consists of microscopic organisms that are single celled, lack a nucleus, and classed as prokaryotes. This domain splits into four main groups; korarchaeotes, euryarchaeotes, crenarchaeotes and nanoarchaeotes. The eukaryote domain consists of organisms that have a nucleus is their cell or cells, they also have smaller cellular structures called organelles that perform specific functions in the cell. The domain eukaryotes are split often into; animals, fungi and plants