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BIOLOGY 1M03 Study Guide - Louis Pasteur, Phylogenetic Tree, Cell Theory


Department
Biology
Course Code
BIOLOGY 1M03
Professor
Jon Stone

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The Tree Of Life
RICEE – all organisms conform to the following 5 things;
oReplication – every organism wants to be able to replicate
oInformation – every organism should be able to interpret
information genetically and from the environment
oCells – all organisms are made of cells
oEvolution – all organisms evolve
oEnergy – all organisms need to gain and use energy
Theory is a pattern and process
oThe cell theory is that all cells come from pre existing cells and
everything is made up of cells
oPattern would be everything is made of cells
oProcess would be all cells come from pre existing cells
Hypothesis Testing
Louis Pasteur tested the cell theory through the experiment with 2 flasks
and cells
A good experiment consists of
oA control group
oA constant environment
oIt can be tested over and over
Louis Pasteur came up with the experiment of checking if all cells come
from pre-existing cells
oHe disproved that cells are made spontaneously
NATURAL SELECTION ACTS ON INDIVIDUALS  EVOLUTION ACTS
ON POPULATIONS
2 conditions of natural selection
oIndividuals vary in characteristics that are heritable
oCertain versions of these heritable traits help individuals survive
better or reproduce more than other versions
Fitness is the ability to produce offspring
Adaptation is a heritable trait that increases the fitness of an individual
Theory of evolution by natural selection had 2 parts
oSpecies are related by common ancestry
oCharacteristics of species can be modified from
generation to generation DESCENT WITH
MODIFICATION
Evolution occurs when heritable variation leads to differential reproductive
success
Fitness is the ability for an individual to produce successful offspring
Adaptation is a heritable trait that aids in the survival of an indivifual
Process of divergence is called speciation

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SPECIES IS DEFINED AS EVOLUTIONARILY INDEPENDENT
POPULATIONS
Speciation
oAll species come from pre existing species
oAll species are traced back to a single common ancestor
Phylogeny is genalogical relationships
oAll cells contain the small subunit rRNA  Carl Woese decided to
examine this (he came up with a really good microscope)
orRNA is made up of sequences of 4 smaller chemicals called
ribonucleotides (A,U) (C,G)
orRNA is a trait that can change during evolution  not identical
among species
oWoese believed that rRNA should be similar in closely related
species and not similar in further related species
A phylogenetic tree depicts evolutionary history by means of similarities
and differences in gene sequences
oShows relationships between species
Tree of life estimated from an array of genes
Tree of life established 3 fundamental groups/ lineages of organisms
oBacteria
oArchea
oEukarya
Naming and classifying organisms is called taxonomy
Any group that is named is called a taxon
Domain represents a taxonomic category  major group
Scientific Species Names
First part indicates the organisms’ genus; a genus is made up of closely
related groups of species
2nd part of the name indicated its species
genus names are always capitalized, species names are not
Evolution by Natural Selection
Theorists and their theories
Theory of natural evolution  Charles Darwin, Alfred Wallace
oExplains how organisms have come to be adapted to the different
environments
Typological thinking  based on the idea that species are unchanging
types and that variations within species are unimportant or even
misleading (Plato)
Species are fixed types and some species are higher on the ladder of
nature- in the sense of being more complex (Aristotle)
Species are not static but change through time  spontaneous generation
and then evolve by moving up the chain over time (Lamarck)

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Darwin and Wallace discovered that evolution occurs because individuals
with certain traits leave more offspring than others do. Population
thinking is a way to view the variation among individuals in a population
to understand the nature of species
Held to be true:
oSpecies change through time
oSpecies are related by common ancestry
Evidence for Change Through Time
A fossil is evidence of something living in the past
The fossil record consists of all the fossils that have been found
Radioactive decay  steady rate at which unstable atoms are converted
into stable atoms- giving ways to determine ages
The pattern of species’ fossils having striking resemblances was later
known as the law of succession
A transitional feature is a trait in a fossil species that is intermediate
between those of older and younger species  link older and younger
species
Vestigial traits are traits that prove that species have evolved over time
oThey are traits that showcase parts of a living species that has
changed or made different use of in terms of their body types
Example: humans as well as other organisms now have
hundreds of pseudogenes (genes that have no purpose)
Species change through time and due to newer observations and
technology today, this change can be monitored.
Darwin took a ship called the Beagle to the Galapagos Islands and studied
the type of bird known as the mockingbirds and looked past their extreme
similarities to find the reason behind their differences  a common
ancestor theory came about
Darwin proposed that the mockingbird populations colonized different
islands had changed through time and formed new species
A phylogenetic tree is a branching diagram that describes the ancestor-
descendant relationships among individual humans
Homology is evidence of descent from a common ancestor
oHomology is the study of “likeness”
oHomology exists in species because of a common ancestor
Human hair and dog fur share a common ancestor
There are 3 types of homology
oGenetic homology
Occurring in DNA sequence
Example: genetic code
oDevelopmental homology
Recognized in embryos
Example: gill pouches in chicks
oStructural homology
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