Biology and the Tree of Life Chapter One

Key Concepts Organisms obtain and use energy are made up of cells, process information, replicate, and as populations evolve. The cell theory proposes that all organisms are made of cells and that all cells come from preexisting cells. The theory of evolution by natural selection maintains that species change through time because individuals with certain heritable traits produce more offspring than other individuals do.

Key Concepts, cont’d A phylogenetic tree is a graphical representation of the evolutionary relationships between species. These relationships can be estimated by analyzing similarities and differences in traits. Species that share distinctive traits are closely related and are placed close to each other on the tree of life. Biologists ask questions, generate hypotheses to answer them, and design experiments that test the predictions made by competing hypotheses.

Proof of Life 1.Energy: to stay alive and reproduce, organisms have to acquire and use energy. 2.Cells: Organisms are made up of membrane-bound units called cells. 3.Information: organisms process hereditary or genetic information, encoded in units called genes, along with information they acquire from the environment. 4.Replication: Almost everything an organism does contributes to one goal: replicating itself. 5.Evolution

The Cell Theory There are two components to the cell theory: 1.All organisms are made up of cells 2.All cells come from preexisting cells

Evolution via Natural Selection Evolution - change of characteristics of a population over time An organism’s traits determine the survival of a species o Reproduction > Survival of Species > Reproduction > Survival of Species When there is change in the environment o Adapting to the environment for reproduction and survival is essential o Variation in traits allows for better adaptation

The Tree of Life - rRNA as an Indicator rRNA (RNA found in ribosomes) o RNA found in ribosomes contains a specific sequence o As organisms evolve from the common ancestor, their rRNA becomes more different from the original organism’s

Main Branches of the Tree The following are placed in a phylogenetic tree based on their properties: o The common ancestor of all of life is eubacteria (normal bacteria without a nucleus) o Then came archaebacteria (bacteria without a nucleus that live in the extreme conditions) o Then came eukarya (organisms with nuclei such as protista, fungi, plants, and animals)

Doing Biology Scientific Method - Understanding how the world works 1.Make observations 2.Ask research question 3.Establish a hypothesis 4.Design an experiment 5.Test the hypothesis 6.Interpret the results 7.Draw a conclusion