Download EVOLUTION Evolutionary Science Sir Charles Lyell (1797

Evolutionary Science
EVOLUTION
Scientists have discovered millions of different
species of organisms, past and present, on earth
and millions more species have yet to be
discovered!
Even though these life forms are diverse, they are
fundamentally similar at the cellular and molecular
level
How has this happened?
Biology 12
Sir Charles Lyell (1797-1875)
Geologist
Suggested that Earth (geological change) had
undergone and continues to undergo slow, steady,
and very gradual change eg. Erosion.
Lyell visited Joggins, Nova Scotia in 1851 where he
found many fossils including the remains of large
plant trunks, some tiny bones and shells.
Chevalier de Lamarck (1744-1829)
Believed that the environment was the key factor in
evolutionary change
1. Theory of need – organisms change because of an
inner need to change
Eg a fish grows a longer tail because it needs to swim faster
to catch prey
2. Theory of use and disuse – if structures are not used,
they will weaken and disappear
3. Theory that acquired traits can be passed onto the
offspring
Eg. A giraffe stretches its neck to make it longer
then passes the trait to its young.
Reverend Thomas Robert Malthus
(1766-1834)
Malthus has become widely known for his theories
about population and its increase or decrease in
response to various factors.
He wrote “An Essay on the Principle of Population”,
published from 1798 to 1826, and observed that
sooner or later a population gets ‘checked’ by
famine and disease.
Alfred Russel Wallace (1823-1913)
British Naturalist
"Every species has come into existence coincident
both in space and time with a closely allied species"
Wallace wrote a letter to Darwin in 1958 outlining
a theory similar to Natural Selection which lead
Darwin to publish the conclusions on Natural
Selection that he had been working on for 15
years.
Charles Darwin (1809-1882)
Charles Darwin published The Origin of Species in
1859. This describes the theory of Natural
Selection.
Wallace Vs. Darwin
Galapagos Finches
A group of 14 or 15
species of passerine birds
found on the Galapagos
islands
The most important
differences between
species are in the size and
shape of their beaks, and
the beaks are highly
adapted to different food
sources.
Darwin always put the emphasis on selection acting on
individuals whereas Wallace apparently thought selection
acted on groups or species. That selection acts on the
individual, due to competition between individuals of the
same species, is one of the key points in Darwin’s theory.
Another apparent difference is that Darwin emphasised
competition within populations as the driving force for
evolution, whereas Wallace put more emphasis on the
species meeting the demands of a change in their
environment.
Evolution defined
Geological evolution: change in the earth over time
– rising of mountains, drifting of tectonic plates etc...
Biological Evolution: the cumulative change in the
heritable characteristics of a population
Cultural Evolution: evolution of our society, cultural
norms, values, knowledge etc...
Gene Pool
Evolution works at the level of a
population, Individual organisms cannot
evolve
There
must be variability between
individuals in a population
There must be a change in the frequency of
the alleles in the gene pool of a population
Gradualism Vs. Punctuated Equilibrium
Gradualism vs. Punctuated Equilibrium
Punctuated Equilibrium - Species remain the same
for long periods of time and then evolve rapidly
during a very short interval - Stephen Gould
Gradualism – new species arise through gradual
changes in their characteristics and evolution occurs
slowly over millions of years. – Charles Darwin
Evidence for Evolution
1. Fossil Record and radioactive dating
2. Comparative anatomy
3. Comparative embryology
4. Comparative biochemistry
5. DNA Sequencing
6. Direct Observation
Fossils
Fossil Record: Fossils offer evidence that evolution
occurred. The sequence in which fossils appear
matches the sequence they would have evolved,
with bacteria and algae appearing first, fungi and
worms later followed by land vertebrates etc... Also
many sequences of fossils are known, which link
together existing organisms with their likely
ancestors
Types of Fossils
Preserved in amber
Preserved in ice
Hard parts – bones and teeth that don’t decay
Petrification- organisms submerged in water high in
mineral content. Organism takes on minerals and
turns to stone.
Molds and cast imprints left in mud that hardens
Radioactive Dating
Radioactive elements decay at a fixed rate
The amount of time it takes for half of the atoms to
decay is called the half life
The age of the rock or fossil can be determined by
the percentage of the elements present.
Comparative Anatomy
Homologous Structures – Structures that look
superficially different and perform a different
function but have “unity of type”. For example, the
forelimbs of a human, mole, horse, porpoise and
bat have the same bones in the same relative
positions. This indicates they have the same origin
and they have become different because they
perform different functions. This is called Adaptive
Radiation.
Analogous Structures –
Structures that are very
different in appearance but
serve the same functions.
Like the tail fins of a whale
and a fish. This implies that
they had different origins
and have become similar
because they perform
similar functions. This is
called Convergent
Evolution.
Vestigial Structures – These are structures that are
reduced and serve no function. Examples are the
beginnings of teeth found in embryo baleen whales,
despite the adults being toothless, the small pelvis
and thigh bone found in the body wall of whales
and some snakes, and the appendix in humans.
These structures have evolved and lost their function
Comparative Embryology
Similar patterns of development in embryos of
different organisms.
This suggests a common evolutionary origin
Comparative Biochemistry
There is greater similarity between the DNA and
proteins of more closely related organisms.
Eg. The hemoglobin molecule of a gorilla and a human
differ by only one amino acid. Human and Chimpanzee
DNA are 98% identical
Nuttall test – the antibodies against human blood
proteins are used to determine how close other
organisms blood proteins are to humans.
DNA and the Evolutionary Clock
Genes are ancestral units of heredity.
Maps of gene sequences provide mathematical key
to ancestral history.
Humans and other advanced organisms have
retained many of the same DNA found in the
simplest bacteria and blue-green algae even
though many of them serve no useful purpose in
humans.
All living things are related by the
immortal thread of DNA
Antibiotic Resistance
Resistance to antibiotics
is increased though the
survival of individuals
which are immune to the
effects of the antibiotic,
whose offspring then
inherit the resistance,
creating a new
population of resistant
bacteria.
Evolution of the Horse
The early ancestors of the modern horse
walked on several spread-out toes, an
accommodation to life spent walking on
the soft, moist grounds of primeval forests.
As grass species began to appear and
flourish, the horse’ diets shifted from
foliage to grasses, leading to larger and
more durable teeth. As predators
evolved, the horse's predecessors needed
to be capable of greater speeds to
outrun predators. This was attained
through the lengthening of limbs and the
lifting of some toes from the ground in
such a way that the weight of the body
was gradually placed on one of the
longest toes, the third
Direct Observation
By observing organisms such as bacteria, which can
reproduce in as little as 20 minutes, evolution can
be observed.
Bacteria have evolved from forms that were once
readily destroyed by penicillin to forms that are
now completely resistant.
Pathologists are constantly developing new
antibiotics to try to keep ahead of the evolution of
new pathogenic bacteria
Viruses
Viruses mutate and evolve even faster than
bacteria.
New flu viruses crop up every year.
A person never gets the same strain of the flu a
second time.
Mechanisms of Evolution
1. Natural Selection
2. Overproduction
3. Genetic Variation
4. Genetic Drift
5. Artificial Selection
6. Biotechnology
Natural Selection
Organisms that possess variations that allow them to
best adapt to their environment survive to produce
offspring thus passing on these favourable traits
and increasing the frequency of favourable alleles
in the population – nature ‘selects’ which organisms
will be successful.
Spoon-hand, Knife-hand, Straw-hand demo...
Peppered Moths
See p. of your Biology 12 Textbook
Overproduction of Offspring
Most species produce more offspring than
the environment can support
This leads to a struggle for survival
Genetic Variation
Variation exists between members of the same
species
Sexual reproduction promotes variation
Genetic Drift
Allele frequency is how often alleles occur in a
population – not all alleles occur with the same
frequency and recessive alleles may be more
frequent than their dominant counterparts.
Genetic Drift is an increase or a decrease in the
allele frequency over successive generations
Speciation
The formation of a new species
Species – a population of structurally similar
organisms which can interbreed and produce fertile
offspring
There are 3 causes of speciation:
Artificial Selection
Domesticated animals – Domesticated breeds have
not always existed in their current form. This change
has been achieved by repeatedly selecting for
breeding the individuals most suited to human uses.
This shows that selection can cause evolution
Speciation by Isolation
1. Isolation
2. Migration
3. Natural Selection
Speciation by Isolation Cont’d...
Reproductive Isolation – differing mating rituals and
courtship behaviours prevent breeding and thus
variations accumulate differently in isolated
populations.
Geographic Isolation –
barriers such as
mountains deserts or
bodies of water
prevent the mixing of
gene pools which
allows differences to
accumulate in the
isolated organisms. If
enough differences
accumulate, a new
species is formed
Migration
Organisms from one environment move to a new
environment. This works two ways:
New gene combinations – new organisms breed with
resident organisms which yields offspring with a new
gene combination
Migration followed by isolation results in speciation
Natural Selection
After mutations occur, the environment acts as a
selector for the more advantageous traits.
The organisms with the advantageous traits survive
to produce more offspring and they pass along
these traits to their offspring – overtime, this leads
to differentiation and speciation.
Evolution Simulations! Yay!
http://www.pbs.org/wgbh/evolution/darwin/origi
n/index.html
http://biologyinmotion.com/evol/
Evolution Video
http://www.pbs.org/wgbh/evolution/library/11/2
/e_s_4.html