Download Topic 5 Evolution

Evolution
Topics 5.1-5.4
Evolution
• Definition : Evolution is the cumulative change in the
heritable characteristics of a population.
• Charles Darwin developed his theory in The Origin of
Species, published in 1859.
• The theory of natural selection can be explained in a
series of observations and deductions.
Evolution
Topics 5.1-5.2
Darwin’s Observations and Deductions
Observation
• Populations of living
organisms tend to
increase exponentially.
• However, the number
of individuals in
populations remain
nearly constant.
Deduction
• More offspring are
produced than the
environment can
support. There is a
struggle for existence in
which some individuals
survive and some die.
Darwin’s Observations and Deductions
Observation
• Living Organisms vary. The
members of a species are
different from each other in
many ways.
• Some individuals have
characteristics that make
them well adapted to their
environment and other
individuals have
characteristics that make
them less well adapted to
their environment.
Deduction
• The better adapted
individuals tend to survive
and reproduce more than
the less well-adapted
individuals.
• (a.k.a. Natural Selection)
Darwin’s Observations and Deductions
Observation
• Much variation is heritable
– it can be passed on to
offspring
Deduction
• The better-adapted
individuals pass on their
characteristics to more
offspring than the less well
adapted individuals. The
results of natural selection
therefore accumulate.
• As one generation follows
another the characteristics
of the species gradually
change – the species
evolves.
Sexual Reproduction Driving Evolution
• Variation is necessary for natural selection
– Mutation : original source for new genes
– Meiosis : greater opportunity for variation
because of independent assortment.
• Species that produce asexually still produce
some variation primarily through mutation.
– Potential for evolution is much less.
Evidence: Homologous Structures
• Homologous
Structures are
structures that are
similar in different
species but come
from common
ancestry.
Fossil Records
• Comparison of
the skulls of a
human (left
column) and the
capuchin monkey
(right column).
Selective Breeding
Method of improving a species by allowing
only those individual organisms with desired
characteristics to produce the next
generation.
How does selective breeding give evidence to
evolution?
Evolutionary Response to the Environment
• Many organisms will evolve in response to the
environment.
– This is typically an environmental threat to the species.
– Struggle for survival leads to evolution(change in traits
seen)
• Examples:
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Galapagos Finches
Pesticide Resistance
Heavy Metal Tolerance in Plants
Antibiotic Resistance
Antibiotic resistance
• Direct exposure to antibiotic does NOT produce
resistance
• Bacteria that have a natural resistance to the
antibiotic survive exposure and reproduce
offspring
• Those that are not naturally resistant die when
exposed to antibiotics. No new off spring
produced
• What remains is a population of resistant
bacteria. ( they “evolved”)
Terminology
• Gene Pool:
– All of the genes in an interbreeding population.
• Allele Frequency
– The number of times a particular allele appears in
a give population
• Species
– A group whose members possess similar
anatomical characteristics and have the ability to
interbreed.
Speciation
• The formation of a new species as a result of a preexisting species spliting.
• Two types of speciation:
– Sympatric : same geographical location
– Allopatric : different geographical location
• This usually results from populations becoming
isolated from the rest of their species.
• This is most commonly seen when populations
migrate to areas that are geographically isolated
from their original territory or different ecologically.
Geographic Isolation
Speciation
• Endemic species are species that exist in only
one place.
– Ex. Galapagos Islands
• Galapagos Finches
– 4 Endemic Species
• Lava Lizards
– 7 Endemic Species that live on twelve different islands
Classification
Topic 5.3
Classifying Organisms
• Advantages to classifying organisms
– Species Identification
• Easy to find out which species an organisms belongs to
– Predictive Value
• Species in the same grouping will have similar characteristics
– Evolutionary links
• Groups with similar characteristics most likely evolved from a
common ancestor. Possible to predict evolution by classifying
organisms.
Classification
• 1959 - 5 kingdoms
established.
• Based on physical
characteristics
seen by scientists
Reclassification
• 1989 Carl Woese
studied the molecular
relationships (RNA)
between organisms
• Established 3 Domains:
* Eubacteria
* Archaea
* Eukarya
Characteristics of the 3 domains
Charactersitic
Eubacteria
Archaea
Eukarya
histones
absent
histone-like
proteins
present
introns
absent
present in some
DNA
present
size of ribosome
70S
70S
80S
structure of cell
membrane lipids
unbranched
hydrocarbons
some branched
hydrocarbons
unbranched
hydrocarbons
peptidoglycan in
cell wall
present
absent
absent
membrane-bound
organelles
absent
absent
Present
Taxa
• Group of organisms (ex. Species) is called a
taxon.
• Organisms are classified into a series of taxa.
There is a hierarchy of taxa.
• The first taxa is the most specific (Homo
sapiens) and the last taxa is the most general
(Kindom Animalia)
• There are seven levels of taxa
Binomial Nomenclature
• Naming system adopted by Carolus Linnaeus
in the 1700’s.
• Nomenclature : name given to a species
• Binomial : Two names are used for naming
• Binomial Nomenclature = Naming system
where two name are used to name each
species
Binomial Nomenclature
continued
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Homo sapiens
First name is the genus name
First name is given an upper-case first letter
Second name is the species name
Species name is given a lower case first letter
Italics are used when the name is printed
Name is underlined if it is handwritten
Levels of Hierarchy for Eukaryotes
(general to specific)
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Kingdom
Phylum
Class
Order
Family
Genus
Species
Examples
Humans
Garden Pea
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Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Primate
Family Hominidae
Genus Homo
Species Sapiens
Kingdom Plantae
Phylum Angiospermae
Class Dicotyledonae
Order Rosales
Family Papilionaceae
Genus Pisum
Species sativum
Dichotomous key
Dichotomous key
Dichotomous key
Dichotomous key
Cladistics
Topic 5.4
Cladistics
• A clade is a group of organisms that have
evolved from a common ancestor
• Evidence can be seen from gene base
sequences or amino acids sequences
• Sequence changes accumulate so there is a
positive correlation between the number of
differences and the amount of time since 2
species diverges (molecular clock)
Molecular clock
Homologous vs. Analogous Traits
• Homologous traits are
similar due to ancestry
• Example; chicken wing,
human arm
• Analogous traits are
similar due to
convergent evolution
• Octopus eye and
human eye
Cladograms
• Tree diagrams based on
similarities and
differences between
species in a clade
• Based on amino acid/DNA
sequences as opposed to
structural features
• Branching points are
called nodes
(hypothetical split of
species)
Cladograms
Cladograms
Cladograms