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Lecture 1

BIO152H5 Lecture Notes - Lecture 1: Organism, Ribonucleotide, Alfred Russel Wallace


Department
Biology
Course Code
BIO152H5
Professor
Fiona Rawle
Lecture
1

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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
cells
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
materials
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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