BIO152H5 Lecture Notes - Lecture 1: Organism, Ribonucleotide, Alfred Russel Wallace
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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 is a life form - a living entity made up of one or more cells
organisms share a suite of five fundamental characters:
energy - have to acquire and use energy in order to survive and reproduce
cells - organisms are made up of membrane bound units called cells; regulates the passage of materials
between exterior and interior spaces
Information - process hereditary or genetic info. encoded in genes as well as from the environment
replication - almost everything an organism does is in order to replicate itself
evolution - organisms are the product of evolution and pop. continues to evolve
1.2 The Cell Theory
theory - an explanation for a very general class of phenomena or observations.
• cell theory and theory of evolution address fundamental questions:
⁃ what are organisms made of?
⁃ where do they come from?
• these concepts emerged in mid-1800s and established two of 5 attributes of life: organism are cellular
and population changes over time
• 1665, robert hooke used a crude microscope to examine the structure of a cork (bark tissue) in which
he discovered small, pore like compartments - cells
• Anton Van Leeuwenhoek created a powerful microscope (up to 300X) - used to examine pond water,
human blood cells and sperm cells
• by the early 1800s enough data was accumulated for biologists to claim that all organisms consist of
Are all organisms made of cells?
• while some organisms consist of one cell others can consist of many (ex. bacteria vs. sequoia tree)
• cell - highly organized compartment that is bound by a thin, flexible structure called a plasma
membrane and that contains concentrated chemicals in an aqueous solution. chemical reactions
take place inside cells. most cells are able to reproduce by dividing
Where do cells come from?
• scientific theories contain two parts:
1. describes a pattern in the natural world
2. identifies a mechanism or process that is responsible for creating that pattern
• 1858, Rudolph Virchow stated that all cells arise from pre-existing cells
• cell theory: all organisms are made of cells and all cells come from pre-existing cells.
• two hypotheses:
⁃ spontaneous generation: that cells arise under certain conditions; spring to life from non living
⁃ all-cells-from-cells: cells produced only when pre-existing cells grow and divide
• Louis Pasteur tested the two hypotheses thru experiments
⁃ did it by creating two test groups: a broth that wasn't exposed to the a source of pre-existing
cells and a broth that was
⁃ spontaneous generation predicted that cells would appear in both test groups while all-cells-
from-cells predicted that it would only appear in the exposed test group
⁃ results: fungi and bacteria filled in the exposed test group whereas the non-exposed test group
stayed sterile for months
• success of the cell theory process meant that if all cells come from pre-existing cells then all
individuals in an isolated population of single celled organisms are related by common ancestry
• as well, multicellular organisms are connected by common ancestry as well
• Charles Darwin and alfred Russel Wallace came with the realization that all species - all distinct,
identifiable types of organisms - are connected by common ancestry
1.3 The Theory of evolution by natural selection
what is evolution?
• Darwin and Wallace made two important claims concerning patterns that exist in the natural world:
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