BIOLOGY 1M03 Chapter Notes - Chapter 1, 24, 25, 26, 27: Allele Frequency, Genotype Frequency, Assortative Mating

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25 Aug 2016
Chapter 1 –Biology and the Tree of Life
Key Concepts
Organisms obtain and use energy, are made up of cells, process information, replicate,
and, as populations, evolve
The cell theory involves the idea that all organisms are made of cells and that all cells
come from pre-existing cells
The theory of evolution by natural selection involves the idea that species change
through time because individuals with certain heritable traits produce more offspring
than other individuals do
A phylogenetic tree is a graphical representation of the evolutionary relationships
between species. These relationships can be estimated by analysing 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.
oPhylogenies can be established by analyzing similarities (and differences) in traits
1.1- What does It Mean to Say That Something is Alive?
Organism: a life form, a living entity made up of one or more cells
-No simple definition of life
Organisms share a suite of five fundamental characteristics:
1) Energy: To stay alive and reproduce, organisms have to acquire and use energy. Ex.
Plants absorb sunlight; animals ingest food
2) Cells: Organisms are made up of membrane-bound units called cells. A cell’s
membrane regulates the passage of materials between exterior and interior spaces
3) Information: Organisms process hereditary or genetic information, encoded in units
called genes, along with information they acquire from the environment. Right now,
cells throughout your body are using genetic information to make the molecules that
keep you alive; your eyes and brain are decoding information on this page that will
help you learn some biology
4) Replication: One of the great biologists of the twentieth century, Francois Jacob, said
that the “dream of a bacterium is to become two bacteria.” Almost everything an
organism does contributes to one goal: replicating itself.
5) Evolution: Organisms are the product of evolution and their populations continue to
1.2 - The Cell Theory
Two greatest ideas in all of science:
-The cell theory
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-Theory of evolution by natural selection
Theory: an explanation for a very general class of phenomena or observations
Most scientific theories comprise two components:
-Patterns observed in the natural world
-Mechanism or processes identified that produce the patterns
In the late 1660s, Robert Hooke and Anton Van Leeuwenhoek were the first scientist to observe
Cell: a highly organized compartment bounded by a plasma membrane that contains
concentrated chemicals in an aqueous solution
Hypothesis: a proposal
Prediction: something that can be measured and must be correct if a hypothesis is valid
Louis Pasteur
-Demonstrated that cells arise from cells and not by spontaneous generation
-Had an effective experimental setup because the two groups differed in only the one
factor being tested
-Used straight necked flask and swan necked flask
oPlace nutrient broth in flask
oBoil to sterilize flask
oPre-existing cells enter flask from air (straight necked flask)
oPre-existing cells from air are trapped in swan neck
-Conclusion: cells arise only from pre-existing cells, not spontaneously from non-living
Because all cells come from pre-existing cells, all individuals in a population of single celled
organisms are related by common ancestry
Darwin and Wallace
-1858, proposed that all species are related by common ancestry
-Proposed that characteristics of species can be modified from generation to generation
-Evolution: entails that species are related to one another and can change through time
-Natural Selection: is a process that explains how evolution occurs
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-Fitness: may be conceptualised as the ability of a typical individual to survive and
produce offspring
-Adaptation: may refer to a trait that increases the fitness of a typical individual in a
particular environment
-Population: group of individuals of the same species living in the same area
-Two conditions must be met for natural selection to occur in a population
oIndividuals in the population vary among themselves in characteristics that are
oIn a particular environment, particular versions of these heritable traits help
individuals survive better or reproduce more than other versions
-If particular heritable traits lead to increased success in surviving and producing
offspring, then those traits become more common in the population over time
oPopulation characteristics change from natural selection operating on individuals
-Evolutionary change occurs in populations
-Evolution occurs when heritable variation leads to differential success in reproduction
Artificial selection: humans select particular individuals to produce the most offspring in a
population, on the basis of particular traits
-Modern biology comprises at least two unifying ideas
oCells are the fundamental structural units among organisms
oOrganisms are related through common ancestry and have changed over time as a
consequence from natural selection
Speciation: a divergence process in which natural selection has caused populations of one
species to diverge to form new species
Tree of Life: a diagram that may be interpreted to infer the genealogical relationships among
species with a single ancestral species at its base
Carl Woese
-Using molecules to understand the tree of life
-Studied small subunit rRNA, as a means for understanding the evolutionary relationships
among organisms
-SSU rRNA is a nucleic acid that constitutes partially ribosomes (the protein producing
organelles in cells)
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