Transcript NATURAL SELECTION - For The King

Biology 11
Mrs. Trevelyan
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How the Turtle Got its Shell...
 260 million old fossil shows how the turtle got its
shell...basically back bones fused together.
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T. Rex was a Chicken???
 In 2003, scientists discovered preserved soft tissue in a
68 million-year old thighbone of a T. Rex.
 In 2007, this tissue was tested twice (independently)
and indicated that the T. Rex is likely related to the
present day chicken.
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EVOLUTION
1. PRESCRIBED LEARNING OUTCOMES
and VOCABULARY
2. VIDEO:
None 
3. TEXTBOOK PGS :
Origin of Life- pg 380-391; Natural Selection- pg 392-403
Mechanisms of Evolution- pg 404-419;
Classification- pg 443-449; Six Kingdoms pg 450-471
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Warm Up Activity
On a separate sheet of paper, write down some responses to
the following questions:
1. What is evolution? What do you already know about it?
2. Where did all the different types of plants and animals on
Earth get here? How did humans appear on Earth?
3. Are we the most advanced, perfected, important form of life
on earth?
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A Brief History of the Theory
of Evolution
Creationalism: the religious belief that all life was made by a
supernatural being and that species have not changed
Jean-Baptiste Lamarck- In early 1800’s, proposed animals
evolve through inheritance of acquired characteristics (not
true!)
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A Brief History of the Theory
of Evolution
Charles Darwin (with help from Alfred Russel Wallace) first
presented his theory of evolution through Natural Selection
in 1859.
Voyage of the BEAGLE
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A Brief History of the Theory
of Evolution
Darwin suggests there was variation in a population and that those
that are best suited to the environment survive and pass on their
traits to their offspring
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Evidence for Evolution
1. Direct evidence in stone (=fossils)
-generally, deeper specimens are more ancient
ACTIVITY: The Evolution of Barbellus Cut and Paste
2. Geological time scale (=rock layers)
-use radioactive carbon dating to
determine age of the rock
(and fossils within it)
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Evidence for Evolution
3. Living organisms have similarities in early development
-the embryos of many different species look similar
4. Living organisms have similarities in Body Structure
-includes homologous structures (same ancestor, different
function, e.g. dog limbs, human arms, fish fins)
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Evidence for Evolution
5. Similarities in chemical compounds (DNA, proteins, amino
acids)
ACTIVITY: Evidence for Evolution Worksheet
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Key Aspects Proposed by
Darwin…
1. There is variation of TRAITS within a population
e.g. eye colour, height, ability to run fast, etc
This is called a
BELL CURVE 
Variation of a trait within a population may be large (wide
curve) or small (skinny curve)
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Key Aspects Proposed by
Darwin…
2. Birthrates are high so populations should GROW
(like, out of control!)
We only see this happening with humans…but why?
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Key Aspects Proposed by
Darwin…
3. A struggle for existence ensures population controls
-competition between individuals (NICHES)
• a NICHE is the combination of an organism’s “profession” and
the place in which it lives
• no two species can occupy the same niche in the same
location for a long period of time
 They will compete for food and home!
The more efficient species will survive and reproduce;
the other will leave or die
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Key Aspects Proposed by
Darwin…
There is also struggle through...
-predators
-environment stresses
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Key Aspects Proposed by
Darwin…
What do we conclude is happening?
 NATURAL SELECTION= the process that results in the most
FIT organisms producing offspring
 This is similar to ARTIFICIAL SELECTION (human breeding
of plants and animals) but without human influence and
taking a longer time
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Natural Selection
 Survival of the fittest- only those organisms best adapted
to an environment will survive, produce offspring, and
pass on their genes.
 Well-suited traits= survive! (genes passed on)
 Poorly-suited traits= death! (genes not passed on)
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An Example of Natural Selection
The Peppered Moth
 the trait is moth colour (controlled by genes/DNA)
 the selective pressure is predators
 the trait varies within the population and changes over time
nonpolluted
forest, lots
of lichen
polluted
forest, lots
of soot but
no lichen
Activity: Peppered Moth Simulation Game
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The Events of Natural Selection
STEPS:
1. Variety exists in a population (favourable and unfavourable)
2. A selective pressure acts on the population
-e.g. limited types of food available to birds selects for a
particular type of bird beak (strong for nuts, sharp for insects
etc)
3. A portion of the population is removed due to the action of the
selective pressure. These animals were less fit and die.
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The Events of Natural Selection
4. Survivors pass on favorable traits to their offspring.
-traits are determined by proteins, which are controlled by
genes (DNA)
-through reproduction, you pass on your genes to your
offspring
5. The distribution of favourable traits shift in the population
(more of the offspring have the trait)
6. The selective pressure acts (with similar results) on the
population for many generations
Ha ha, you can’t
hurt me now!!! I’m
RESISTANT
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Types of Natural Selection
There are 3 types:
1) Directional Selection
-one extreme trait is selected against- this is a less common
trait found on the edge of the curve
-population shifts to the right or to the left (depends on which
trait is being selected against)
-the average changes
e.g. giraffe neck length; selection for
taller necks resulted in longer necks
becoming more common
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Types of Natural Selection
2) Stabilizing Selection
-two extreme traits are selected against- these are less
common traits found on both edges of the curve
-population does not shift, but has less variety of traits
-the average does not change, but the FREQUENCY of the
average trait has increased
e.g. flower colour; selection
against white and red flowers
resulted in pink flowers
becoming more common; red
and white flowers become
less common
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Types of Natural Selection
3) Disruptive Selection
-the two extreme traits are favoured- the most common trait is
selected against
-population splits in two; this may over time lead to two
separate species
e.g. bird colour; selection against
grey birds resulted in white and
black birds becoming more
common; grey birds become less
common
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In Summary:
Activity: Worksheets (X2) on Types of Natural Selection
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A New Species Evolves!
Species= a group of organisms that can breed with one another
and produce fertile offspring in a natural environment
Speciation= the process of new species evolving from an old
one
**New species usually form only when POPULATIONS
are isolated or separated**
Population- groups of organisms of the same species whose
members can breed with one another; more than 5
individuals
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Isolation of a Population
Pre-zygotic Isolation
1) Geographical barriers- rivers, mountains, roads
2) Behavioural differences- Courtship behaviours or fertile periods
Eww..
Budgie- budgie
Budgie
lovebird
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Isolation of a Population Cont’d
3) Habitat Preference- live in different places in an area
e.g.meadow vs. wooded areas
4) Mating Seasons Differences
e.g. frogs in Texas breed 2-3
months earlier than frogs
elsewhere
5) Body Size or structural differencese.g a tiny
poodle will not
mate with a
large husky
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Isolation of a Population Cont’d
Post-zygotic Isolation:
1) Sterile offspring- e.g.) a donkey and a horse give rise to a
sterile offspring
2) Offspring die after being born
3) Aborted during pregnancy
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A New Species Evolves!
 If two populations are reproductively isolated, natural
selection is different for each group.
 results in each population become better adapted to different
environments.
 over time, their separate gene pools gradually become more
dissimilar, leading to two separate species.
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Another Example of Speciation:
Darwin’s Finches
Found on various nearby islands; beaks adapted to the type of food they eat
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An Example of Speciation: Darwin’s 13 Finches
1. Founding Fathers and Mothers- first explorers to arrive at
Island A
2. Separation of Populations- birds fly from Island A to Island B
(ocean is a geographical barrier)
3. Changes in the Gene Pool- populations on ach island became
adapted to the needs of their environments (i.e. beak size)
4. Reproductive Isolation-difference in beak size makes species
A look unworthy to mate with to species B. They will no
longer interbreed; this leads to separate species
5. Sharing the Same Island- leads to coexistence (if they live in
different niches), extinction (if they live in the same niche), or
further evolution are possible
ACTIVITY: Gizmo: Rainfall and Bird Beaks (Metric)
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What Darwin didn’t know…
Why do we have such variation?
 different combinations of GENES
 passed on through sexual reproduction
changed by MUTATIONS in your DNA
ACTIVITY: PhET Natural Selection
http://phet.colorado.edu/en/simulation/natural-selection
You have inherited your traits from your parents! Thanks dad and
especially mom!
Video: http://www.youtube.com/watch?v=osWuWjbeO-Y
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Thanks DNA!
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Structure of DNA
• Deoxyribonucleic acid is made up of
•
•
•
•
many nucleotide subunits.
a nucleotide consists of a sugarphosphate backbone and a
nitrogenous base
Bases: Adenine, Guanine, Thymine or
Cytosine
Complimentary base pairing is A-T
and C-G only!
Bases bonded by weak H-bonds
ACTIVITY: Modelling DNA Cut and Paste
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Protein Synthesis
 DNA makes proteins  physical traits
 Involves 2 steps:
1. Transcription
-DNA unzips, a copy of RNA is made in the nucleus
2. Translation
-RNA leaves the nucleus and is “read” by a ribosome. TRNA
matches the codons on RNA and brings amino acids. A chain
of amino acids is formed = protein.
Protein Synthesis Animation:
http://www.learnerstv.com/animation/biology/Proteinsynthesis.swf
ACTIVITY: Protein Synthesis Comic
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The Role of DNA & Mutations
 Speciation involves changes in PHENOTYPE (physical
characteristics) that arise due to changes in GENOTYPE
(genetic code, or DNA)
 Changes in DNA are called MUTATIONS
 Most (99%) mutations are HARMFUL and lead to DEATH!
 Some mutations are beneficial and improve the FITNESS of an
individual. This potentially allows for more offspring, which
will carry the mutation/new phenotype.
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The Role of DNA & Mutations
Fast Rabbit Escapes!
Slow Rabbit Does Not Escape
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The Role of DNA & Mutations
ACTIVITY: Identify the Mutation Worksheet and Mechanisms of Evolution W/S
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Mating Across Species
An aside: some cross-species mating can occur but
this is VERY, VERY, VERY rare!!
Horse +
zebra = zorse
Shark +
horse....just
kidding here!
Lion + tiger =
liger
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Types of Speciation
1. Divergent Evolution (also known as Adaptive
Radiation)
-one species gives rise to many species that live in
different niches
-HOMOLOGOUS STRUCTURES (same ancestor but not
necessarily same function)are evidence divergent
evolution
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Types of Speciation
2. Convergent Evolution
-when two different organism produce species that are
similar in appearance and behaviour
-ANALOGOUS STRUCTURES (have same function but no
common ancestor) are seen in convergent evolution
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Types of Speciation
3. Parallel Evolution
-when two different species evolve independently of one
another- maintaining the same level of similarity
-the two species usually do not live in the same niche
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Parallel Evolution Example
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VESTIGIAL STRUCTURES
 These are body structures that no longer serve its
original purpose
 Examples:
Whales have remnant “legs”
Video: Whale Evolution
http://www.youtube.com/watch?v=8cn0kf8mhS4
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Shaping the Evolutionary
Theory
 Hardy and Weinburg developed a mathematical model for
evolution. They found that evolution will not occur in a
population unless ALLELIC FREQUENCIES are acted apon =
HARDY-WEINBURNG PRINCIPLE
ALLELE= genetic trait; an alternative form of a characteristic that
can be inherited
e.g. Blue eyes, brown eyes, green eyes
ALLELIC FREQUENCY= percentage of alleles in a population
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Shaping the Evolutionary
Theory
 A non-changing population (no change in allelic
frequency) is said to be in GENETIC EQUILIBRIUM
 Five conditions for H-W Principle to work:
1. No genetic drift
Of course, these
2. No gene flow
happen in the real
3. No mutations
world, so this model is
not perfect
4. No selective mating
5. No natural selection
Activity: Chapter 15-2- Mechanisms of Evolution Part I fitb
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Rate of Speciation
 There are 2 models: the gradual change model and the
punctuated equilibrium model of evolution
1. Gradual Change Model
-occurs SLOWLY
-consistent levels
of change over
time
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Rate of Speciation
2. Punctuated Equilibrium Model
-sudden big change
followed by periods of
little to no change
Activity: Chp 15.2 Mechanisms of Evolution Part II Read & fitb w/s
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Other Agents of Evolutionary
Change
 Natural selection and mutation are NOT the only way
speciation occurs!
 Other agents of evolutionary change:
1. Genetic drift
2. Gene flow
3. Non-random mating
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Other Agents of Evolutionary
Change
1. Genetic drift (aka allelic drift)
-is the change in frequency of a gene variant (ALLELE) due
to RANDOM SAMPLING/CHANCE (e.g. fire, avalanche, etc)
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Other Agents of Evolutionary
Change
2. Gene flow (aka migration)
-is the transfer of alleles or
genes from one population
to another.
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Other Agents of Evolutionary
Change
3. Non-random mating- humans use non-radom mating on
plants and animals (selective breeding)
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In Summary
 Simpson’s evolution video
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