Lab 2A--Life on Earth
Geology 1402
Chapters 3 & 7 in the textbook
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A comment
• Many people including professional
scientist are skeptical of evolution or
outright reject it.
• I am not attempting to change your mind if
you are in that group.
• I am attempting to explain an idea that is
widely accepted by the scientific
community and is supported by extensive
evidence.
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Evolution
• Broad definition: Change
• Organic evolution: Change in life forms
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Organic Evolution
• How life has changed through time.
• How all life is interrelated through ancestry.
• Fossils: tangible record of changes in species
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Linnaean Classification Scheme
• System for classifying (grouping)
organisms---usually by form
• Grouped by
– shared similar characteristics, that is to say,
– they have the same forms and look very
similar.
5
Why classify organisms?
• Avoid complete chaos
• Determine which have a common ancestor
-or• Who is related to whom
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Caution
• Not all similarities mean a close ancestral
relationship
• Often similarities come from adapting to a
similar environment
7
Linnaean Classification Scheme
• DNA confirms relationships—has changed
some old ideas
• We find relationships with ancestors by
looking at the number of differences in
amino acid sequences which make up
DNA
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Classification of Life
(Fossils & Living Groups)
Kingdom Protista
Kingdom Fungi
Kingdom Animalia
Kingdom Plantae
Singlecelled
organisms
Source: http://www.windows2universe.org/earth/Life/classification_intro.html
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Classification of Life
(Fossils & Living Groups)
• Domain: Archaea—prokaryotes (bacteria)
• Domain: Eubacteria—prokaryotes (bacteria)
• Domain: Eukaryota--eukaryotes
– Kingdom Protista
– Kingdom Fungi
– Kingdom Animalia
– Kingdom Plantae
Lab book page 25— is out of date.
Monera was split into Archaea and Eubacteria.
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Linnaean Classification
• Kingdom
• Phylum
– Subphylum
• Class
•
•
•
•
Order
Family
Genus
Species
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Lamarck—An Idea Rejected
• Inheritance of acquired
characteristics
• Organisms adapt—a
giraffe stretches neck to
reach high leaves
• Giraffe can pass the longer
neck to young
• No—It doesn’t happen
this way.
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Evolution
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Evolution
• Idea evolved slowly
• Many people before Darwin suggested
evolution
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Darwin had read
Thomas Malthus
• Malthus published: Essay on the Principle
of Population (1798)
• A key idea: “…favourable variations would
tend to be preserved, and unfavourable
ones to be destroyed.”
• Survival of the fittest.
15
Evolution
• Darwin on the H.M.S. Beagle (1831-1836)
– Observed bird populations on isolated islands
– Recognized different species but closely
related species (finches)
– Recognized the influence of environment on
differing species.
– Published On the Origin of Species (1859)
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Evolution
• Basic idea: Species descended from prior
species
• Debated and accepted within a decade.
Very remarkable accomplishment.
• Controversy came when humans were
included in the theory
17
Note:
• Darwin never said:
Humans descended from monkeys.
• Darwin said:
Apes and humans have a common
ancestor.
18
Natural Selection
• “survival of the fittest”—the most suitable
for the environment (not the strongest!)
• This applies to individuals and to species
• Variations
– Some individuals able to survive better and
reproduce more abundantly
– Traits (forms) dominated
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Keys to Natural Selection
• Variation within a population among
individuals.
• The variation must be inheritable.
• Differences in reproductive success based
upon those differences.
20
Artificial Selection
• Humans decide which
individual will breed with
which.
• Examples:
–
–
–
–
Dog breeding
Race horse breeding
Cattle breeding
Turkey breeding
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What are the two things that
every living thing does?
Eat
Reproduce
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What are the two things that
every living thing does?
• Eat & reproduce
• Pass on your traits:
– Eat better than your competition (survive)
– Reproduce more
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Changes
• Changes in organisms or populations are
often due to changes in the environment.
• The ones that survive are those that can
adapt and tolerate the environmental
changes.
• The successful trait must already be
available in the gene pool. (Discuss)
24
Genes, DNA & RNA
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Genetics
1822-1884
Austria-Hungary
• Gregor Mendel
–
–
–
–
Published in 1865
Unknown to Darwin
Experimented with peas
Demonstrated that traits from
each parent were inherited by
offspring
– Traits passed by genes
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Genes
• Genes are paired—one set from each
parent
– Note: Sexual reproduction produces more
variation than asexual reproduction.
• Genes do not mix (Key point!)
– Some are dominant and obvious
– Others are recessive and hidden
• Passing of genes produces variation in a
population
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DNA: deoxyribonucleic acid
• Genes are sections on the DNA.
• Allele: part of the gene that passes on the
trait to offspring.
• DNA molecules: basic hereditary units
• DNA: information for making proteins out
of amino acids
• Proteins make cells
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DNA
• Each nucleotide
contains one of the
following:
–
–
–
–
Adenine
Thymine
Cytosine
Guanine
A
T
C
G
• These nucleotides
determine the
characteristics of an
organism
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Mutations—How Change Happens
• Alterations in DNA
• Genes can move from one part of the DNA
to another
• Amino acids are substituted for others: the
code changes
30
What can cause mutations?
•
•
•
•
Radiation (even ultraviolet radiation)
Cosmic rays and gamma rays
Chemicals
Random changes in the genetic code
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Are mutations good or bad?
• Comments from class.
• Discussion
• What do we call bad mutations in
humans?
• Bad—”birth defects”
• Good—helpful traits
• Neutral—makes no difference
• The call—How well does the organism
adapt to the environment?
32
RNA—Two Types
• DNA—inside the cell
• RNA—Passes through the cell wall
– mRNA—Messenger RNA: Carries message
from DNA to site where proteins are formed
(outside the cell)
33
RNA—Two Types
• DNA—inside the cell
• RNA—outside the cell
– tRNA—Transfer RNA: Ferries amino acids to
sites where they are assembled into proteins
(outside the cell)
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Speciation
• The development of new species
• A change in the gene pool
• Isolated populations diverge, that is,
change and eventually cannot interbreed
• Now have a new species
35
What is a species?
• Species—
– Group of organisms
– Similar structure, function and development
– Able to produce fertile offspring (in nature)
• Examples of non-species:
– Mule (female horse and male donkey)
– Liger (tiger and lion—only happens in zoos)
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Patterns of Evolution
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Patterns of Evolution
• Divergent evolution
– A single species evolves into two distinct species,
each with distinctive traits
• Adaptive radiation
– Many new species evolving different traits to live in
different environments
• Convergent evolution
– Unrelated species exhibit similar adaptations when
they inhabit similar environments (wings: birds and
bats)
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Divergent Evolution in Plants
All had a common ancestor
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Adaptive Radiation
Bills Adapt
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Convergent Evolution
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Vestigial Structures
(Remaining structures)
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How fast is evolutionary change?
• Phyletic gradualism
– Small changes over a long period of time
• Punctuated equilibrium
– Very distinct changes over a very short period
of time with little change in between these
“bursts”
• (draw diagram)
43
Comparison
How
quickly
does
change
happen?
44
Organization of Life
• Old way: Based upon observable traits
that arise from genetic processes.
• Now: A clade—a group of organisms that
share a common ancestor based upon
DNA analysis, not just observable forms.
45
Clade
• A clade—a group of
organisms that share
a common ancestor
based upon DNA
analysis, not just
observable forms.
46
Clade
Based upon DNA
similarity
47
Clade
Different species within
a category must have a
common ancestor
48
Clade
A clade—a group of
organisms that share a
common ancestor
based upon DNA
analysis, not just
observable forms.
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Clade
50
Review of Classification of Life
(Fossils & Living Groups)
• Domain: Archaea
• Domain: Eubacteria
• Domain: Eukaryota
– Kingdom Protista
– Kingdom Fungi
– Kingdom Animalia
– Kingdom Plantae
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Any questions?
Please do lab two & the supplement.
Omit all questions in the lab book
that have a table to fill in.
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