Download Evolution - Westlake FFA

Changes through time
“Survival of the Fittest”
Evidence that life has
changed and is now changing
Fossil Record
 Fossils are remains or traces of organisms
that lived in the past.
Fossil Record
 Fossils are usually found in sedimentary
rock.
 Organisms are buried soon after death
and the hard parts become fossilized.
Fossil Record
 Fossils indicate a great deal about the
actual structure of the organisms and
their environment.
Types of fossils
 Petrified Bones
Types of fossils
 Imprints
Types of fossils
 Molds/Casts
Types of fossils
 Fossils preserved in tar,
amber, or ice
Relative Age of Fossils
 Layering of
fossils:
 Older fossils
are found in
the lower
levels of
sediment
Relative Age of Fossils
 Layering of
fossils:
 Newer fossils
deposited on
top of older
fossils and
sediment
 Sometimes flipped
by earthquakes, etc.
Relative Age of Fossils
Relative Age of Fossils
 Fossils in each layer usually of
those organisms that lived at
the time the layer was formed.
 Fossils in lower layers
represent species that lived
earlier than those found in the
upper layers.
 Relative position only tells
which are older and which
younger.
Evolution of the
Horse
 Over time (higher
layers of sediment)
horse fossils became
larger
 Separate toes
became a single-toed
hoof
 Teeth became
adapted to grinding
grasses
Radiometric Dating
 Some elements, such as
uranium, undergo
radioactive decay to
produce other elements.
 Scientists have
observed that
radioactive elements
(isotopes) decay at a
constant rate over time
Radiometric Dating
 The amount of radioactive elements
remaining in a rock can help scientists
determine how much time has elapsed since
the rock was formed and cooled.
 Common isotopes used for long-term dating
(old rocks) include uranium as it decays to
lead, and potassium as it decays to argon.
 The carbon-14 isotope can be used for
dating of more recent fossils and artifacts
Radiocarbon Dating
 Carbon-14 is a radioactive isotope found
in all living organisms.
 It decays at a known rate.
 Carbon-12 does not decay.
 By comparing the ratio of C-12 to C-14
scientists believe they can
determine the age of a fossil
Radiocarbon Dating
A timescale
 Based on radiometric data, scientists have
proposed a timeline for the history of the
earth.
 Composed of four primary “eras”




Archeozoic (oldest) [aka Precambrian period]
Paleozoic
Mesozoic
Cenozoic (most recent)
Archeozoic Era
 Oldest known rocks and fossils
 Animals without backbones
 Jelly-fish, worms, sponges
 Bacteria and blue-green algae
Paleozoic Era
 Estimated from 248-550 million years ago
 Animals: Fish, amphibians, and insects
 Plants: Algae and simple plants; first
conifers
Mesozoic Era




Estimated from 65-248 million years ago
Age of the Dinosaurs
Animals: Reptiles and birds
Plants: Conifers and first flowering plants
Cenozoic Era
 Estimated from present to 65 million years
ago
 Age of the Mammals
 Animals: Mammals and birds
 Plants: Flowering plants
Contemporary Changes
 Evidences we can observe within our
lifetime
 Pesticide resistance in insects
Contemporary Changes
 Evidences we can observe within our
lifetime
 Antibiotic resistant bacteria
Indirect evidences
 Scientists cite these indirect evidences as
evidence of common ancestry



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Homologous structures
Embryonic development patterns
Biochemical evidence
Vestigial organs
 They at least demonstrate a common
pattern of development
Parts of the body with similar
structure (homologous)
Human Cat
Whale
Bat
Similar patterns of embryonic
development (homologous)
Human
Swine
Reptile
Yes, you had a tail as an embryo!
Bird
Homologous Development –
actual photos of embryos
Reptile
Bird
Rabbit
Human
Biochemical similarities –
DNA and Proteins
 The ability to analyze individual biological
molecules (DNA and proteins) has
provided evidence for biochemical
similarities
Methods of Change
Jean Baptiste Larmarck
 French naturalist and
evolutionary theorist
 1744-1829
 Proposed the
inheritance of
acquired
characteristics
 Based on an “inner
need” to change
Larmarck’s theory
 His theory was disproved
Charles Darwin and Natural
Selection (1859)
 Naturalist on the
HMS Beagle
Charles Darwin and Natural
Selection (1859)
 Exploration of South
America (3 ½ years)
 Visited the
Galapagos Islands
Darwin’s theory of Natural
Selection
1. Living things
increase in number
geometrically
(overproduction)
2. There is no net
increase in the
number of
individuals over a
long period of time
Spider eggs: Many more produced
than will survive
Darwin’s theory of Natural
Selection
3. A “struggle for
existence” since not
all individuals can
survive
4. No two individuals
exactly alike
(variation)
Darwin’s theory of Natural
Selection
5. In the struggle for existence, those
variations which are better adapted to
their environment leave behind them
proportionately more offspring than
those less adapted
“Survival of the Fittest”
A Modern Perspective
1. Mutation – a sudden change in the
genetic material (a source of variation)
Example: The DNA of one bacteria changes
(becomes mutated), allowing it to become
resistant to an antibiotic. It survives long
enough to reproduce. Each succeeding
generation has the mutated copy and is
resistant to the antibiotic.
A Modern Perspective
2. Recombination of genes within a
population (sexual reproduction)


Provides new combinations for natural
selection to try.
Shows how the percentage of a gene in a
population can change.
A Modern Perspective
3. Isolation – separation of a population
from others of the same kind (species)


Prevents recombination of genes
Species become different overtime

Example: A species of primrose existed together where the
Promontory Range (Northern Utah) now exists. When the range
lifted up, it isolated two groups. Both became different as they
adapted to the different environments on either side of the range.
They have become so different they can no longer reproduce.
A Modern Perspective
4. Natural Selection – certain traits give an
adaptive advantage to organisms and
they leave behind more offspring
They survive long enough to reproduce and
pass on their genetic information
INDIVIDUALS DO NOT EVOLVE . . .
POPULATIONS EVOLVE OVER TIME
Species
 A group of individuals that
LOOK similar and are capable
of producing FERTILE
offspring in the natural
environment.
Population
 All of the members of the
same SPECIES that live in
particular AREA at the same
TIME.
Variation in a population
 Bell Curve - The distribution of
traits (Average is the middle.)
 Mode - The number that
occurs most often (High pt.)
 Range - The lowest number to
the highest number
Sexual Selection
 Preferential choice of a MATE
based on the presence of a
specific trait
Speciation
 The formation of new
SPECIES
Isolation
 Separation of a formerly
successful BREEDING
population
Geographic Isolation
 Separated PHYSICALLY from
each other
Reproductive Isolation
 Can no longer produce
FERTILE offspring
Extinction
 When an entire SPECIES dies
off.
Gene pool
 The collection of GENES for
all of the traits in a
POPULATION
Hardy-Weinberg Principle
 Genetic Equilibrium – no
CHANGE in the gene pool
Conditions that must exist
for genetic equilibrium
1.
2.
3.
4.
5.
No MUTATION
No MIGRATION
Large POPULATION
Random MATING
No NATURAL SELECTION
Natural Selection
Three types of selection
1. Stabilizing Selection
2. Directional Selection
3. Disruptive Selection
Stabilizing Selection
 Individuals with the AVERAGE
form have the ADVANTAGE
 Example – lizards that are small are not
fast enough to avoid predators; lizards
that are large cannot hide easily from
predators; those of average size are
both fast enough to get away from
predators and small enough to hide –
giving them the selective advantage.
Directional Selection
 Individuals with one of the
EXTREME forms have the
ADVANTAGE
 Example – Peppermoth in Great Britain during
the industrial revolution – “melanistic” (dark
colored) moths had the selective advantage
after trees where covered in coal soot. After
air quality improved, the selection advantage
returned to the lighter colored moths.
Directional Selection
 Peppermoth – find two moths per picture
As the ants dig deeper, anteaters with longer tongues
have the adaptive advantage – survive to reproduce.
Disruptive Selection
 Individuals with either of the EXTREME
forms have the ADVANTAGE
 Example: a shellfish living in shallow ocean water is
preyed upon by a bird. Originally those with the
neutral color (sand colored) had the advantage
because they were camouflaged in the sand. As the
birds fed on the shellfish and left their feces behind in
the water, the ocean floor became white in color.
Those shellfish that were sand colored are now easily
found while the lighter colored shellfish are able to
blend in, as are the darker colored shellfish if they
are found on the darker rocks.
How have crops and livestock
changed over the last 50 years?
In producing better
livestock or crops, what
are some examples of
traits for which
producers select?
Then
Now
Then
Now
Then
Now
Then
Now
Then
 Removing Seeds
Now
 Seedless
Then
 Dehorning
Now
 Polled
Natural Selection
 an organisms’ ability to SURVIVE
and pass on its GENETIC
information to its offspring.
Selective Breeding
 Also known as Artificial Selection
 Human control over organisms
passing on their genetic information.
 Human determination of those crops
and livestock allowed to reproduce
 Based on desired traits
Selective Breeding
In what ways is
selective breeding
similar to natural
selection?
In what ways is it
different?