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Transcript
Lab 2A--Life on Earth
Geology 1402
Chapters 3 & 7 in the textbook
1
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.
2
Evolution
• Broad definition: Change
• Organic evolution: Change in life forms
3
Organic Evolution
• How life has changed through time.
• How all life is interrelated through ancestry.
• Fossils: tangible record of changes in species
4
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
6
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
8
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
9
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Lab book page 25— is out of date.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.
10
Linnaean Classification
• Kingdom
• Phylum
– Subphylum
• Class
•
•
•
•
Order
Family
Genus
Species
11
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.
12
Evolution
13
Evolution
• Idea evolved slowly
• Many people before Darwin suggested
evolution
14
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)
16
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
19
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
21
What are the two things that
every living thing does?
Eat
Reproduce
22
What are the two things that
every living thing does?
• Eat & reproduce
• Pass on your traits:
– Eat better than your competition (survive)
– Reproduce more
23
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
25
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
26
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
27
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
28
DNA
• Each nucleotide
contains one of the
following:
–
–
–
–
Adenine
Thymine
Cytosine
Guanine
A
T
C
G
• These nucleotides
determine the
characteristics of an
organism
29
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
31
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)
34
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)
36
Patterns of Evolution
37
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)
38
Divergent Evolution in Plants
All had a common ancestor
39
Adaptive Radiation
Bills Adapt
40
Convergent Evolution
41
Vestigial Structures
(Remaining structures)
42
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.
49
Clade
50
Review of Classification of Life
(Fossils & Living Groups)
• Domain: Archaea
• Domain: Eubacteria
• Domain: Eukaryota
– Kingdom Protista
– Kingdom Fungi
– Kingdom Animalia
– Kingdom Plantae
51
Any questions?
Please do lab two & the supplement.
Omit all questions in the lab book
that have a table to fill in.
52