BISC 102 Chapter Notes - Chapter 1: Organism, Archaea, Carl Linnaeus
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16 Oct 2019
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Chapter 1: Biology and the Tree of Life
1.1 - What does it mean to say that something is alive?
● Organism: a lifeform; a living entity made up of one or more cells; most biologists agree that
organisms share five fundamental characteristics:
○ Cells: membrane-bound units; make up organisms
○ Replication
○ Evolution
○ Information - encoded information (genes) and responding to information coming in
from the environment
○ Energy - acquire and use energy
● Theory: an explanation for a very general class of phenomena or observations that is
supported by a wide body of evidence
1.2 - Life is Cellular
● Early discoveries:
○ Robert Hooke devised the first crude microscope and noticed compartments that he
named “cells” in bark tissue
○ Leeuwenhoek then developed more powerful microscopes that added evidence of
cells
● All organisms are made of cells, from the smallest organisms (bacteria) to some of the largest
(e.g. sequoia trees)
● Cell theory: all organisms are made of cells, and all cells come from preexisting cells
○ That is, cells are produced from the growth and division of preexisting cells
■ Shown by Pasteur in his experiment involving nutrient broths and either swan-
neck flasks (prevented cells from entering the flask) and straight-necked flasks
(allowed cells to enter the flask from the air)
● The first cells arose from nonlife through chemical evolution
1.3 - Life Evolves
● Darwin and Wallace proposed that all species are connected by common ancestry
○ This is paralleled in human biology in the way all cells in the body are the result of
division and are linked by common lineage
● Darwin and Wallace’s theory:
1. Species are related by common ancestry
2. A species’ characteristics can be modified from generation to generation
● (i.e. species are related to one another and can change through time)
● Natural selection: explains how evolution occurs; two conditions of natural selection:
1. Characteristics that are heritable: meaning trains that can be passed on to offspring