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Biology and the Tree of Life

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Title: Biology and the Tree of Life


1
Biology and the Tree of Life
  • Chapter 1

2
Unity and Diversity of Life
3
Unity and Diversity of Life
  • Scope of biology is immense
  • Huge variety of life forms with many diversifying
    characteristics
  • Two unifying concepts
  • Cell theory
  • Theory of evolution by natural selection

4
Cell Theory
  • In the late 1660s, Robert Hooke and Anton van
    Leeuwenhoek were the first to observe cells.
  • By the 1800s there were enough observations to
    make the generalization that all organisms were
    made of cells

5
Cell Theory
  • The cell theory states that all organisms are
    made of cells and all cells come from preexisting
    cells.
  • Based on inductive reasoning
  • Hooke and van Leeuwenhoek showed that all
    organisms are made of cells
  • Louis Pasteur proved that cells arise from cells
    and not by spontaneous generation

6
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7
Cell Theory
  • Implicated that
  • All single-celled organisms in a population are
    related to a single common ancestor
  • And all cells in a multi-cellular organism also
    descend from a single ancestral cell

8
The Evolution of Life
9
Theory of evolution by natural selection
  • In 1858, Darwin and Wallace proposed that all
    species are related by descent from a common
    ancestor.
  • Theory of evolution states that
  • Species change over time and are related to one
    another.
  • Natural selection is the process by which
    evolution occurs

10
Natural Selection
  • Individuals of the same species living in the
    same area at the same time constitute a
    population.
  • Two conditions must be met for natural selection
    to occur in a population
  • Individuals in the population must differ from
    one another for some heritable trait(s)
  • Differential reproductive success due to
    heritable traits.

11
Natural Selection
  • In natural selection, as the individuals with the
    favorable traits increase in frequency, a
    populations characteristics will change over
    time
  • In artificial selection, individuals in a
    population are selected for mating based on
    particular traits. Repeating this process over
    generations results in a population with altered
    characteristics

12
Artificial Selection
13
Artificial Selection
  • Allows breeding for particular characteristics
  • Brassica oleracea- broccoli, cabbage, kale,
    brussell sprouts
  • All the same species, just different cultivars
  • Same with dogs and cats

14
Classifying Life
15
Classifying Life
  • Linnaeus taxonomic system for classifying
    organisms, each organism is given a unique
    two-part scientific name consisting of the genus
    and the species.
  • Linnaeus system is hierarchical with nested
    taxa. The taxonomic levels from least to most
    specific are kingdom, phylum, class, order,
    family, genus, and species

16
Classification of Man
17
Classification of Man
18
Classification of Organisms
  • Linnaeus proposed a two kingdom system
  • Plant and animal
  • An alternative five-kingdom system based on
    phylogeny was proposed in the 1960s
  • Monera, Protista, Animalia, Plantae, and Fungi

19
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20
Molecular Classification
  • Carl Woese and colleagues studied small subunit
    rRNA, as a means for understanding the
    evolutionary relationships among groups of
    organisms.
  • Closely related species should have rRNA
    sequences that are more similar than those from
    distantly related species
  • rRNA sequences can be used to produce a
    phylogenetic tree

21
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22
Molecular Classification
  • The tree of life indicates three major groups of
    organisms the eukaryotes (Eukarya) and two
    groups of prokaryotesthe Bacteria and the
    Archaea.
  • Woese proposed a new taxonomic level called the
    domain. Each of the three domains (Bacteria,
    Archaea, and Eukarya) includes several related
    kingdoms)

23
The Tree of Life
24
Experimenting with Biology
25
Hypothesis Driven Science
  • In science, inquiry that asks specific questions
    involves the proposing and testing of
    hypothetical explanations, or hypotheses
  • A hypothesis is a tentative answer to a
    well-framed question, an explanation on trial
  • Makes predictions that can be tested

26
Hypothesis-Driven Science
  • Example
  • Hypothesis All human males
  • have a Y sex chromosome.
  • Prediction If this hypothesis is correct,
  • Experiment and I test all human males,
  • Predicted result these males should have the Y
    sex chromosome.

27
Example Dead Batteries
28
Hypothesis Driven Science
  • A scientific hypothesis must have two qualities
  • It must be testable
  • It must be falsifiable
  • Is an idealized process of inquiry
  • No amount of testing can prove a theory beyond a
    shadow of a doubt
  • Most scientific endeavors do not follow the
    scientific method to the letter
  • Often the research gets redirected or changed all
    together

29
Experimental Design
  • A good scientific experiment must have three
    parts
  • A control group to check for other factors that
    might influence the results
  • experimental conditions that are controlled to
    eliminate extraneous variables
  • the test is repeated to reduce the effects of
    random variation (sample size).
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