Transcript EVOLUTION BASICS

Fundamentals of Evolution
A Summary of Evolution
Fundamentals of Evolution
A Summary of Evolution
Nothing in Biology Makes Sense Except in the Light of
Evolution
EVOLUTION:
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The frequency of an allele in a gene pool of a population depends on many
factors and may be stable or unstable over time. As a basis for understanding
this concept:
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Students know why natural selection acts on the phenotype rather than the genotype
of an organism.
Students know why alleles that are lethal in a homozygous individual may be carried
in a heterozygote and thus maintained in a gene pool.
Students know new mutations are constantly being generated in a gene pool.
Students know variation within a species increases the likelihood that at least some
members of a species will survive under changed environmental conditions.
Evolution is the result of genetic changes that occur in constantly changing
environments. As a basis for understanding this concept:
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Students know how natural selection determines the differential survival of groups of
organisms.
Students know a great diversity of species increases the chance that at least some
organisms survive major changes in the environment.
Students know the effects of genetic drift on the diversity of organisms in a
population.
Students know reproductive or geographic isolation affects speciation.
Students know how to analyze fossil evidence with regard to biological diversity,
episodic speciation, and mass extinction.
Students know how to use comparative embryology, DNA or protein sequence
comparisons, and other independent sources of data to create a branching diagram
(cladogram) that shows probable evolutionary relationships.
Evolution
Definition: A change in a population of a
species over time
Organisms evolve to adapt better to their
environment
According to Evolution, all living things
(organisms) on the planet are related and
have a common ancestor
A unicellular prokaryote (bacteria)
that lived near hydrothermal vents
where the temperature is near 200
degrees Fahrenheit amidst poisonous
hydrogen sulfide and deadly sulfuric
acid
Formation of EARTH
First need to talk
about formation of
earth: 4.6 billions yrs
ago!
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How do we know this stuff:
RADIOACTIVE DATING-
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Not relative dating•Solar system in beginning (~5 billion yrs ago) was a swirling mass of gas
and dust that collapsed inward leaving some debris outside (planets)
Formation of Earth and water
FORMATION OF LIFE
(First organic molecules)
Scientists believed early earth
had perfect conditions: ammonia
(NH3), Water vapor, hydrogen
gas, and methane gas
(containing Carbon)
Perfect boiling temperatures lead
to first organic compounds amino
acids
Earth cooled and water vapor
turned to liquid (oceans)
Then complex reactions with UV
light and lightning lead to more
complex organic compounds that
did not contain any genetic info
(no DNA nor RNA)
First replicating molecules
RNA was the first genetic material to selfduplicate.
DNA was the second and the one that
most organisms use today
First Prokaryotes
(the early cells that are still around today
aka bacteria)
Since no oxygen on earth before 1.7 bya,
first cells must have been anaerobic-Most likely heterotrophs that depended
on organic molecules. After consuming
all organic molecules, there was a need
for some organisms to evolve into
autotrophs
These first autotrophs resembled
archaebacteria (aka extremophiles)-These early archaebacteria obtained their
energy by chemosynthesis--
Effects of Oxygen
Oxygen began being produced about 1.7 billion
yrs ago by photosynthetic organisms that
resemble modern cyanobacteria (like simple
unicellular green algae).
Oxygen was probably deadly to most early
organisms
As O2 levels rose (for another 1billion years),
ultraviolet radiation by the sun converted O2 to
O3 ozone (poisonous to life) so life could still not
exist on land yet
Life continued to exist only in the ocean
First cells by endosymbiosis
Then many of these cells began sticking together, first in
colonies, then permanently attached; first multicellular
organisms: early invertebrates (look at timeline Handout in
summer reading packet)
Then after more oxygen was released by early plant forms
and algae, multicellular organisms diversified rapidly
(Cambrian explosion)
EVIDENCE FOR EVOLUTION
MACROMOLECULAR EVIDENCE: #1
(Comparing the DNA, proteins and other
molecules of life of other organisms)
FOSSIL EVIDENCE: #2
BIOGEOGRAPHY
EMBRYOLOGY
COMPARATIVE ANATOMY
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VESTIGIAL STRUCTURES
HOMOLOGOUS STRUCTURES
ANALOGOUS STRUCTURES
CLASSIFICATION
1. FOSSIL EVIDENCE
Allow scientists to see how organisms
changed over time
Shows when different forms of organisms
appeared, lasted for periods of time, then
disappeared only to be found by newer
forms of life.
Another look at sedimentary layers
Relative age: by comparing
layers
Absolute age: measuring radioactivity
in certain rocks
2. Macromolecular (Molecular
biology) Evidence
DNA EVIDENCE-
Since all organisms on
the planet contain
DNA, we can
compare their DNA
to see which
organisms are more
related and then
construct a
phylogenic tree or a
cladogram
DNA evidence
Here is the GENOTYPE (genetic information of an
organism). This Genotype will eventually lead to
an organisms’ PHENOTYPE (organism’s physical
or behavioral appearance)
2. Macromolecular (Molecular
biology) Evidence (continued)
Amino acid
evidence; the
building
blocks of
proteins!
3. BIOGEOGRAPHY:
Study of Geographical
distribution of fossils
Same fossils on West
Coast of Africa and East
Coast of South America.
HOW??--Scientists see a trend.
Life forms arise in the
same areas where
similar, older forms once
existed
Homologous Structures
-Structures from different
organisms that look
similar because the
organisms descended
from common ancestors.
These structures have
evolved to perform
ANALOGOUS STRUCTURES
Structures that are similar in form and
function but evolved independently.
Although a bird and insect are not recently
related, they are distantly related but for
whatever reason, they happened to evolve
wings for flight.
EMBRYOLOGICAL EVIDENCE
Embryos look similar
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____________ but look different
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This suggests that all these
vertebrates have a
_____________
______________. The fact that
they end up looking different, is
a result of evolution. Each
organism’s DNA (instructions)
has evolved a new message – to
become a different type of
organism
VESTIGIAL STRUCTURES
DefinitionExamples-
LAMARCK vs DARWIN
Acquired traits (Lamarck)– Use and disuse
– Acquired Traits are passed
down to offspring. NOT!no genetic change only a
phenotypic change
DARWIN’S THEORY
OVERPRODUCTION: some must die because
of ____________
VARIATION: increases the likelihood that at least
some members of a species will survive under
changed environmental conditions
NATURAL SELECTION “survival of the fittest
(according to the environment!)” not everyone
survives the same!
INHERITED (passed down): Successful
individuals pass down these fit traits
Genes and evolution: Natural selection
acts on (tests) the phenotype
PATTERNS OF EVOLUTION
Co-evolution:
Hummingbird’s beak and
a long thin flower
Convergent evolution:
similar environments push development of
similar features –anteater’s tongue
Divergent evolution:
– Adaptive radiation - ___________
– Artificial selection- ____________
SO HOW DO WE GET A NEW
SPECIES????
Called Speciation: The formation of a new
species occurs when members of a species
are isolated reproductively (they can’t
reproduce with each other and so they
adapt to their environment on their own)
Two ways:
Geographic isolation
Reproductive isolation
FORMATION OF A NEW SPECIES
(Branching on the tree of life)
BIOLOGICAL
SPECIES CONCEPT:
Proposed by Ernst Mayr:
a species is a –
___________________
_________________
– Limitations in this
concept
Extinct organisms?
Asexual organisms?
Population Genetics
The smallest unit of evolution is the
population.
Population: Collection of individuals from
a single species that routinely interbreed.
There is variation in a population (humans,
fish, every life form)
A bell curve shows the
variations on a
population and how
they average out in the
center. Extremes at
either end.
The gene pool:
Gene pool=
all the genetic differences in a population
Let’s pretend our classroom
represents the gene pool with all
the differences in our population
Things that can affect the gene pool
Mutations: add more variety to the gene pool
Migration: immigration (+) and emigration (-):
both cause gene flow:
Genetic Drift: When a random event causes
your gene pool to change: genetic drift is
more dramatic in small populations not large
Non random mating: choosing to mate with
organisms with similar characteristics; not
random but controlled
Types of Natural Selection
RATE OF SPECIATION
GRADUAL VS PUNCTUATED
Can organisms plan their
evolution?
Did giraffe’s grow longer necks on purpose to
reach the trees?
Did ancient primates decide to walk upright to
become humans?
If the world gets covered in water like in the
movie “Waterworld”, will some of us grow gills?
Will we look like aliens in the future?
Evolution is random!!!
Not something planned or on purpose
Mutations and sexual reproduction create variationif these variations happen to help you live in your
environment– then good for you! 
You’ll get to survive better, reproduce more
successfully, and pass those “fit” traits to others
But what if the environment changes again? Well,
we don’t know if those traits will keep on helping
you. Maybe they will, maybe they won’t
Just keep hoping that we keep creating variationsthis will increase our chances of adapting
What about the future of earth and global warming?