Biology 171 EXAM

1. List the characteristics that all living organisms have; describe how biologists distinguish living organisms from non-living entities. Characteristics of all living organisms: ● Has potential to reproduce ● Responds to environmental stimuli ● Composed of 1 or more cells ● Contain genetic material (DNA) and can replicate their genetic material ● Made up of organic molecules (contain C) and water based ● Populations of this entity evolve ● Obtain energy and materials from environment Living things grow internally and nonliving things grow externally ● All living things share same 8 characteristics 2. Give a reason why viruses might be considered living and a reason why they might not. NOT. Viruses are not made out of cells, cannot keep themselves in stable state, do not grow, and cannot make their own energy ARE. Viruses replicate and adapt to their own environment 3. Describe what the “tree of life,” and phylogenetic trees more generally, represent. “tree of life”—idea that all life is related by common descent Phylogenetic trees—show evolutionary pathways and connections among organisms 4. Identify past and present on a phylogenetic tree, along with the root and nodes on a tree. The single line is the ancestors and the branches all the way on the end are the present-day species; the patterns where the branches connect represents our understanding of how species in tree evolved from a series of common ancestors Nodes—represent a divergence event, or splitting apart of a single group into two descendant groups Root—most common ancestor of all present-day species and oldest ancestor