Transcript Evidence_for_change

Evidence shows change

The continuing process of genetic
change in a population of organisms
over long periods of time is called:
EVOLUTION
History of Evolution
• At first most people believed that species could not
change, that there were a fixed number of species,
and that each species had a given set of traits that
remained with it forever.
•As stronger evidence became more available, they
began to see living things change over long periods
of time.
•Jean Babpiste de Lamarck and Charles Darwin led
the way in the search for the mechanisms that
caused this change.
Jean Baptiste de Lamarck
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1809 –proposed a hypothesis to explain the
variation in organisms.
Acquired Characteristics- traits that
developed during a lifetime could be passes
on to the offspring.
 I.e. giraffes stretched their necks over a
lifetime to reach food. They then passed on
the longer neck trait to their offspring.
Rejecting Lamarck’s Hypothesis
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Large amounts of
data showed that
acquired traits are
not hereditary.
Charles Darwin
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1836 took a voyage on the H.M.S Beagle to
the Galapagos Islands and collected a lot of
data.
 Natural Selection- a mechanism for change in
a population that occurs when individuals with
the most favorable variations for a particular
environment survive and pass these traits on
to offspring.
Natural Selection
1. Variations exist within populations.
2. Some variations are more advantageous
for survival and reproduction than others.
3. Organisms produce more offspring than
can survive.
4. Over time, offspring of survivors will
make up a larger proportion of the
population.
Peppered Moths
Variation in moths some
black some light colored.
In 1850 most were light.
Industrial revolution
covered trees with smoke
and soot. Now the dark
moths were better suited
for the environment.
Play Natural Selection Game
In this simulation of natural selection, an
equal number of light and dark Peppered
Moths are released in a forest. You are a bird
in the forest, trying to eat as many moths as
possible. To eat, click on the moth. The
current population of light and dark moths are
shown at the bottom of the screen.
Peppered Moths in a lichen covered forest
Peppered Moths in a dark, soot covered forest
Mechanisms of Evolution

The change in the genetic makeup of a
population of organisms over long
periods of time is called:
EVOLUTION

When allele frequencies change the genetic
equilibrium is altered and evolutions has
taken place.
2. Changes in genetic Equilibrium
a. Mutations are changes in genetic
material of an organism. Provides new
genetic material in a species.
Changes in genetic equilibrium
b. Genetic Drift – the change in allele
frequencies of a population as a result
of chance processes.
The survival and
reproductions of
organisms is
subject to
unpredictable
accidents
See an example
Changes in genetic equilibrium
continued
c.
Gene Flow is the movement of genes
in and out of the gene pool.
Gene flow increases genetic variation within a
population
Patterns of Evolution
Patterns of Evolution
3. Adaptive Radiation – species adapting
to different environments and become
a new species.
Recap
video
Evidence for change
Fossils- provide scientists with strong
records of the earth’s past.
A fossil is the remains of an organism
preserved in the earth’s crust
Where are fossils found?
Found in layers of
sedimentary rocks.
 Organisms were
buried in layers of
mud and or sand.

4 types of fossils

Imprint
 Mold
 Cast
 Petrified
Imprint Fossils
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The soft parts of
buried organisms
decay and leave an
imprint in the stone.

I.e. animal tracks
and plants
Mold fossils

The hard parts of an
organism decay and
leave indentation in
the rock.
Cast Fossil

A mold fossil fills
with mineral or rocks
Cast Dinosaur eggs
Petrified Fossils

Highly porous
materials like bones
or wood can
become petrified if
they are buried
quickly and
thoroughly.
More Petrified Fossils
Relative Dating
Relative dating tells scientists if a rock
layer is "older" or "younger" than
another.
 fossils found in the deepest layer of
rocks in an area would represent the
oldest forms of life in that particular rock
formation.

Evolution of the horse
Living organisms
resemble most
recent fossils in
the line of descent;
underlying
similarities allow
us to trace a line of
descent over time.
Absolute Dating

The use of
radioactive isotopes
to date fossils and
rocks.
 A radioactive
isotope is an atom
with an unstable
nucleus and decays
at certain rate.
Half-Lives of Selected
Radioactive Isotopes
Isotope Half-Life
 14-C
5730 y
 24-Na
15.0 h
 32-P
14.3 d
 36-Cl
3.1 x 10+5 y
 40-K
1.28 x 10+9 y
 45-Ca
165 d
 226-Ra
1.62 x 10+3
y
 235-U
7.1 x 10+8 y
 238-U
4.51 x 10+9 y
 239-Pu
2.44 x 10+4
Homologous Structures

Structures that are similar and are
derived from the same body parts.
Vestigial Structure
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Body parts that are reduced in size and serve no
apparent function.
I.e – Human tail bone – no function
Examples of Vestigial Structures
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Human appendix useless yet in other
mammals, including primates, it is necessary
to aid in digestion of high cellulose diet
Human external ear muscles still present but
useless
Humans have tailbones and some babies
occasionally have tails
Human wisdom teeth vestigial compared to
other primates
Some snakes have skeletal limbs
Cave dwelling crayfish have eyestalks yet no
eyes
Analogous Structures

Body part that have
similar functions but
originate from
different structures.
Examples of Analogous
structures
structures "fitted" for a particular
purpose tend to be similar, regardless of
origin
 flippers in dolphins, penguins and fish.
 wings have developed independently in
insects, reptiles, birds, and bats

Embryonic Development
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Gill slits and tail in
human embryo
show similarities of
embryos of
dissimilar
organisms.
Biochemical Analysis or
DNA/RNA Comparisons
•Comparison of nucleic acid sequences shows similarities
between species. The more closely related organisms are,
the more similar is their biochemical makeup
•Cytochrome C, a protein, The more closely related
organisms are, the more similar their amino acids are.
•Humans differ by 1 nucleotide compared to monkeys
•Humans differ by 19 nucleotides compared to turtles