Transcript evolution

Evolution
What is evolution?
 Evolution is the
process of biological
change by which
species of organisms
change over time.
 Evolution is a central
theme in all fields of
biology today.
Evolution is when organisms change
over time. So, modern organisms
descended from ancient ones.
Evolution is a Theory –
Just like Gravity!
• Evolution is a well
supported
explanation of
phenomena that
have occurred in
the natural world
• A theory in science
is a well tested
hypothesis, not just
a guess
Evolutionary Scientists
 Charles Bonnet mid-1700s
 First to use term evolution
 Studied fossils
 James Hutton
 1795 Theory of Geological change
 Jean-Baptiste Lamarck 1809
 Charles Lyell
 Geographical features can be built up or torn down
 Charles Darwin
 Thomas Malthus
 Russell Wallace
 Gave Darwin the drive to publish his findings
Malthus
 Reasoned that if the
human population
continued to grow
unchecked, sooner or
later there would be
insufficient living space
and food for everyone
Jean-Baptiste Lamarck
 He proposed the idea of inheritance of
acquired characteristics:
 changes in an environment caused an
organism’s behavior to change
 this would lead to greater use or disuse of a
structure or organ.
 the structure would become larger or smaller
and would then be passed down to offspring
 For example: giraffes’ long necks
 Idea was WRONG!!
Charles Darwin
 Natural selection was
the theory he proposed
to explain evolution.
 He attempted to provide
reasons for the biological
diversity on Earth.
 Developed his theory
from personal
observations and
research of other
scientists.
Charles Darwin (1809-1882)
Sailed around the world 1831-1836
on the British ship H.M.S. Beagle.
What did
Darwin’s Travels
Reveal?
 The diversity of living
species was far greater
than anyone had previously
known!!
 These observations led him
to develop the theory of
evolution!!
 He observed the land and
its inhabitants.
 Finches and Tortoises
What did Darwin do?
 He noticed the physical differences among
island species.
 Species on one island looked different from
those on another island.
 Island species looked different from those
found on the mainland. This is known as
variation.
 Genetic variations arise from mutations
 He noticed that the physical differences among
the species were appropriate for their
environment and diet.
Darwin finally
published his
ideas in 1859.
 Other naturalists
were developing
the same theory
that Darwin did.
 Even though he
was afraid of the
Church’s reaction
to his book he
wanted to get
credit for his work.
Natural Selection
 The traits that
help an organism
survive in a
particular
environment are
“selected” in
natural selection
Evidence of Evolution
1. Fossil Record
2. Homologous Body structures
3. Similarities in Embryology
4. Biochemical Evidence
Evidence of Evolution:
The Fossil Record

Fossil record
provides evidence
that living things
have evolved

Fossils show the
history of life on
earth and how
different groups of
organisms have
changed over time
Relative
vs.
Absolute
Dating
Relative Dating
 Can determine a
fossil’s relative age
 Performed by
estimating fossil age
compared with that of
other fossils
 Drawbacks – provides
no info about age in
years
Absolute Dating
 Can determine the
absolute age in
numbers
 Is performed by
radioactive dating –
based on the amount
of remaining
radioactive isotopes
remain
 Drawbacks - part of the
fossil is destroyed
during the test
• Radiometric dating uses decay of unstable
isotopes.
– Isotopes are atoms of an element that differ in their
number of neutrons.
– A half-life is the amount of time it takes for half of the
isotope to decay.
Primate Fossils
Australopithecus
Homo erectus
Homo sapien
Primate Bone Structure
Evidence of Evolution:
Homologous Body Structures

Turtle
Structures that
have different
mature forms but
develop from the
same embryonic
tissues
Ex: Wing of bat,
human arm, leg
of turtle
Alligator
Bird
Evidence of Evolution:
Homologous Structures
 Features that are similar in structure but
appear in different organisms and have
different functions.
 Strong evidence for common ancestor.
 Ex: forelimbs of humans, bats and moles.
Human hand
Mole foot
Bat wing
Analogous Structures
 Structures that perform a similar
function.
• Not evidence of common
ancestry.
Vestigial Structures
 Remnants of organs or structures that
had a function in an early ancestor.
 Ex: Ostrich wings, used for balance but
not flight
 Ex: Humans’ appendix
Evidence of Evolution:
Similarities in Embryology
In their early stages
of development,
chickens, turtles and
rats look similar,
providing evidence
that they shared a
common ancestry.
Embryological Development
Evidence of Evolution:
Biochemical Similarities
 Scientists study nucleotide sequences in
DNA and proteins in different organisms
to determine ancestry.
 If the organisms are closely related they
will have similar sequences of
nucleotides in their DNA and
arrangement of amino acids in proteins.
Evidence of Evolution:
Biochemical Similarities
Organism
Amino Acid
Differences
Organism
Amino Acid
Differences
Human beta
chain
0
Mouse
27
Gorilla
1
Kangaroo
38
Rhesus monkey
8
Chicken
45
Dog
15
Frog
67
Cow
25
Soy bean
124
The more similar the
Patterns,
Processes, and
Rates of Evolution
Adaptation
 Darwin’ observations led him to realize
that species must somehow be able to
adapt to their surroundings.
 Adaptations allow species to better survive
in their surroundings.
 Adaptations can lead to genetic change in
a population over time.
Variation Among Species…
 Organisms in the same species have
different traits…
 Known as variation
 Variations may result from mutations or from
how genetic material is rearranged during
sexual reproduction
 Variations within a species can have two
results:
 Speciation
 Extinction
VariationSpeciation
 Individuals with beneficial trait are well suited for
the environment
 They reproduce and pass the beneficial trait to their
offspring
 Individuals without the beneficial trait are less
likely to survive and reproduce
 Their traits are not passed.
 Beneficial traits are passed while other traits
disappear
 These changes can eventually cause speciation
Speciation
 Evolution of a new species from an existing
species
 Occurs if the environment changes
 Individuals with beneficial traits will survive and pass
their traits on to offspring
 Ex: Colder weather-animal with thicker fur
 Ex: Type of food-animal equipped to eat new type
 Ex: New predator-animal able to escape
 Speciation Creates Biodiversity
 Variety of organisms, their genetic information, and
their habitats.
Mechanisms of Evolution
 Genetic variation that leads to evolution can be a result of
several things:
 Mutations
 Changes in DNA
 Only mutations in gametes affect evolution
 Gene flow
 Introduction of genes from one population to another
 Low gene flow=evolution of different species
 Gene pool
 Combination of genetic material from all members of a
population
 Affected by mobility-more mobility=higher rate of gene flow
Rates of Evolution
 CatastrophismGeorges Cuvier
 He believed that a natural
disaster would occur, cause
landforms to change and cause
species to become extinct
 Once that species went extinct
another would come in and take
its place
 Did not believe species changed
over time
Rates of Evolution
 Two main views:
 Gradualism-James Hutton
 Evolution occurs slowly and constantly over a long
period of time
 Darwin
 Punctuated Equilibrium
 Evolution occurs in spurts
 Period of rapid speciation then long period of little to
no change
 Caused by random mutations or sudden changes in
environment
 Cambrian explosion
Rates of Evolution
 Uniformitarianism-Charles Lyell
 Expansion of gradualism
 Favored theory of geologic change
 Proposed that changes occur slowly at a constant
rate continuously
VariationExtinction
 Permanent loss of a species.
 Two causes:
 Populations fail to adapt
 Sudden, drastic changes in the environment
 Humans attempt to prevent extinction of
species through captive breeding,
restricting hunting, and creating
sanctuaries.
Mass Extinction
 Extinction of huge numbers of species in
a short period of time
 Earth has experienced several mass
extinctions
 250 million yrs. ago-ocean invertebrates
 65 million yrs. ago-dinosaurs