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Evolution
Evolution- the gradual
accumulation of
adaptations over time; a
gradual change over time
• Adaptation- evolution of a
structure, behavior , or
internal process that
enables an organism to
respond to stimuli and
better survive in an
environment
Fossils
• Age of earth- estimated 4.6
billion years old
• Fossil- physical evidence of
an organism that lived long
ago that scientist use to study
the past; evidence may be in
rocks, amber, or ice
• Paleontologist- scientist
who study ancient life. They
are like detectives who use
fossils to understand
events that happened long
ago.
• Fossil record- name given
to the history of life on
earth as shown by fossils
• Why is fossil record
incomplete- not all fossils
have been found, and not
all organisms have been
preserved
• Sedimentary rock- small
particles of mud, sand or
clay that is compressed
over time and hardened
• How are fossils formed?
Most fossils are formed in
sedimentary rock from
being buried in the mud,
sand, or clay before it
hardens
• Relative dating- scientist
determine the order of
appearance and extinction of
species that formed fossils in
the layers. Layers at the
surface must be younger than
the deeper layers
• Radioactive dating- AKA
radiometric dating and
carbon dating- utilizes
radioactive isotopes in
rocks or fossils.
• Radioactive dating is more
accurate
• What is half life? b/c every
radioactive isotope has a
characteristic decay rate,
scientist use the rate of
decay as a type of clock
• Extinction- when the last
members of a species die
Homology
• Homologous structuresstructures with common
evolutionary origins, can be
similar in arrangement, in
function, or both; provides
evidence of evolution of a
common ancestor
• Examples- 4 limbs of a
crocodile
• Whales-flippers
• Birds-wings
• Embryology- study of
embryos which is the earliest
stage of growth and
development of both plants
and animals; differences and
similarities among embryos
can provide evidence of
evolution
• Example.. Can’t tell the
embryo of a fish, bird, or
mammal apart. They all
have gill slits, tail, and
notochord. Fish are the only
ones who keep them
throughout life.
• Biochemical similarities
(genetic)- provides
evidence for evolution- All
organisms have the same
DNA and RNA
• Vestigial structures- body
structure that has no function
in a present day organism but
was probably useful to an
ancestor long ago
• Appendix
• Analogous structuresstructures that do not have
a common evolutionary
origin but are similar in
function
• Example- a bird wing and a
butterfly wing, both are
used for flying; however,
they are the same structure.
• Natural Selection- mechanism
for change in populations;
occurs when organisms with
certain variations survive,
reproduce, and pass their
variations to the next
generation; can be directional
, disruptive, or stabilizing
• Charles Darwin- father of
evolutionary theory.
Proposed the theory of
natural selection.
• Another name for natural
selection- survival of the
fittest
• Peppered moth- H.B.
Kettlewell studied
camouflage adaptations of
a population of light and
dark colored peppered
moths. The moths rested on
the trunks of trees.
• Camouflage- enables
species to blend with their
surroundings
• Ex- peppered moth , snake
you do not see
• Mimicry- a structural
adaptation that enables one
species to resemble
another species
• Ex- butterfly that looks like
a wasp
• Fittest- how suitable the gene
is in the environment for a
particular population
• Niche- role and position a
species has in its
environment
• Genetic drift-alteration of
allelic frequencies in a
population by chance
events, result in genetic
equilibrium
• Speciation- process of
evolution of new species
that occurs when members
of a similar populations no
longer interbreed to
produce fertile offspring
Divergent evolutionevolution in which species
that once were similar to
ancestral species diverge;
occurs when populations
adapt to different
environmental conditions,
• Adaptive radiationdivergent evolution in
which an ancestral species
evolve into an array of
species to fit a number of
diverse habitats
• Convergent evolutionevolution in which distantly
related organisms evolve
similar traits, occurs when
unrelated species occupy
similar environments