Unit 7Evolution

Objectives

Distinguish between the scientific terms: hypothesis,

inference, law, theory, principle, fact, and observation

Explain how natural selection can impact allele

frequencies of a population

Describe the factors that can contribute to the

development of new species (e.g., isolating

mechanisms, genetic drift, founder effect, migration)

Explain how genetic mutations may result in genotypic

and phenotypic variations within a population

Interpret evidence supporting the theory of evolution

(i.e., fossil, anatomical, physiological, embryological,

biochemical, and universal genetic code)

Lesson 1Scientific Theories

Objective

Distinguish between the scientific terms: hypothesis,

inference, law, theory, principle, fact, and observation

Scientific Theories

All science begins with direct observation

Example: I saw a lizard eat a cricket.

Observations can often be quantified

Example: I observed a lizard eat 15 crickets in 3

hours.

Direct observations can also be called facts

Observations can lead to inferences that are

logical conclusions based on the observations

Example: This type of lizard eats insects for food.

Questions

Observations and inferences often lead

to questions

Not all questions are testable

Example: Why do lizards eat crickets?

A hypothesis can turn a non-testable

question into a testable question

Example:

Hypothesis: Crickets are part of this lizard’s

natural diet.

Question: Are crickets part of the natural diet of

this lizard?

When numerous observations are consistent, a scientific law can be developed to generalize the results

There should be no contradictions to the observations

Example: This lizard is insectivorous.

Where there is general agreement, scientific principlesdevelop from the laws

Example: Most insectivorous lizards share common characteristics and behaviors.

Scientific theories are used to explain observations using scientific laws and scientific principles

This must be based in evidence!

Example: Most insectivorous lizards evolved from a common ancestor and have several shared characteristics.

Scientific Theories

Opinions

Any belief that has insufficient evidence

to produce certainty

Individual scientists have opinions

Science itself should not include opinions

and should be based on scientific

theories, scientific principles, and

scientific laws that are all originally

based in observations

Lesson 2Changes to Populations

Objective

Explain how natural selection can impact allele

frequencies of a population

Changes in Populations

Evolution – a change in a population

over time

Charles Darwin was the first to propose

natural selection as the mechanism for

evolution

Other scientists before him discussed

evolution, but he was the first to

explain how it happens

Darwin used a series of observations

and inferences

Observation – something that can be

seen and or recorded

Inference – a logical conclusion based

off another observation or inferenceBy J. Cameron (Unknown) [Public domain],

via Wikimedia Commons

Darwin’s Observations

Observation 1: species produce lots of offspring

(overproduction)

Observation 2: resources are limited (competition)

Inference 1 (O1 + O2): there is a struggle for survival

Observation 3: populations are made of many

unique individuals (variation)

Observation 4: offspring look like parents (heredity)

Inference 2 (O3 + O4): individuals with beneficial traits will

be more likely to produce offspring with the same beneficial

traits (survival of the fittest)

Inference 3 (I1 + I2): beneficial traits will become

more common through many generations

(evolution + adaptation)

Adaptation

Natural selection results in

traits that are beneficial to an

organisms survival

Survival of the fittest

What is considered “fit” is

dependent on the environment

Example: Antibiotic Resistance

Public Domain via Wikimedia Commons

Population Genetics

Natural selection changes the genetics of a

population

Example:

50 deer with two alleles for fur length

F = long fur (50% of alleles in starting population)

f = short fur (50% of alleles in starting population)

10 deer with short fur (ff) die during a cold winter

F is now 75% of the remaining alleles

f is now 25% of the remaining alleles

The population evolved!!!!

Evolution = CHANGE over TIME

Sexual Selection

Special case of natural

selection

Traits may not be beneficial

for survival, but help in

finding mates

To be evolutionarily successful,

you need to survive and

reproduce

Creative Commons , courtesy of Lebobs via Wikimedia Commons

Selective Breeding

Humans have used evolution to

their advantage using selective

breeding otherwise known as

artificial selection

We choose traits that benefit us

and allow these organisms to

produce offspring

Virtually all agricultural animals

and plants came to be using this

method of selection

Creative Commons , courtesy of John Doeblyvia Wikimedia Commons

Lesson 3Speciation

Objective

Describe the factors that can contribute to the

development of new species (e.g., isolating

mechanisms, genetic drift, founder effect, migration)

Speciation

Species – group of organisms with the potential

to have viable offspring

How does one species become two different

species?

Requires isolation

Two populations can diverge and become different

enough to be called separate species

Even if the populations rejoin, the populations will not

interbreed

EXAMPLE

By No machine-readable author provided. Fastfission~commonswiki assumed (based on copyright claims).

[Public domain], via Wikimedia Commons

Studying Evolution at All Scales

Because it affects every aspect of

biology, scientists can study evolution at

many scales

Microevolution

Macroevolution

Microevolution refers to evolution as a

change in the genes of a population

Macroevolution refers to the appearance

of new species over time

Microevolution

Five major processes can affect the kinds of

genes that will exist in a population

1. Natural selection

2. Migration

3. Mate Choice

4. Mutation

5. Genetic Drift

Natural Selection

Can cause an increase or decrease

of certain traits in a population

By Khaydock (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Migration

The movement of individuals into, out of, or between

populations.

Migration can change the numbers and types of traits in

a population

By Nuzree [CC0], via Wikimedia Commons

Mate Choice

If parents are paired up randomly in a population, a

random assortment of traits will be passed on to the

next generation.

If parents are limited or selective in their choice of

mates, a limited set of traits will be passed on

By DeFacto (Own work) [CC BY-SA 4.0

(http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Mutation

Can change the numbers and types of traits from

one generation to the next.

These changes are rare.

By Thomas Shafee (Own work) [CC BY-SA 4.0

(http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Genetic Drift

The random effects

of everyday life can

cause differences in

survival and

reproduction of

individuals

By Professor marginalia (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL

(http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

Bottleneck Effect

By Professor marginalia (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

Factors that Contribute

to Speciation

Why islands are perfect:

Geographic isolation: island population separated from

mainland population (Hawaii, Galapagos, other islands)

Founder effect: the island population is often started by

a very small number of individuals, so the new

population is instantly unique from the mainland (Amish)

Genetic Drift: the island population is often small and

random fluctuations can have drastic impacts

Migration: migration between populations is limited, this

allows the populations to become different

All of these factors can come in to play in situations

other than islands

Macroevolution

(1) Coevolution

Organisms are part of one

another’s environment, so they

can affect one another’s

evolution

(2) Adaptive Radiation

Over time, species may split into

two or more lines of

descendents. As this splitting

repeats, one species can give

rise to many new species

By L. Shyamal (Own work) [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons

Macroevolution

(3) Extinction

If all members of a species die off or simply fail to

reproduce, they are said to be extinct

By Tim Hough (Own work) [CC BY-SA 3.0

(http://creativecommons.org/licenses/

by-sa/3.0)], via Wikimedia Commons

By BazzaDaRambler [CC BY 2.0

(http://creativecommons.org/licens

es/by/2.0)], via Wikimedia Commons

By Charles H. Smith vergrößert von Aglarech

(U.S. Fish and Wildlife Service) [Public

domain], via Wikimedia Commons

Macroevolution

(4) Gradualism

Occurs uniformly and by the steady, gradual changes over long periods of time

(5) Punctuated Equilibrium

Most populations will show little change for most of their geological history, and when evolution does occur, it is localized in rare, rapid events of branching speciation

By Miguel Chavez, modified by wooptoo (Own work)

[Public domain], via Wikimedia Commons

The Rate of Evolution

Both of the models to the right

probably occur, but punctuated

equilibrium seems to be more

common

Drastic changes to the

environment may be the cause of

rapid change

The stable areas may be important

for accumulating genetic variation

(mutations)

By Miguel Chavez, modified by wooptoo (Own work)

[Public domain], via Wikimedia Commons

Other types of Isolation

These are important in creating new

species as well as maintaining them as

separate species

Geographic isolation – the most important

Habitat isolation – populations live in different

parts of the ecosystem

Reproductive isolation – populations have

different mating habits that do not allow cross-

breeding

Gametic isolation – if cross-breeding occurs, the

sperm will not fertilize the egg

Hybrids

By Алексей Шилин (Own work) [Public domain], via Wikimedia CommonsBy No machine-readable author provided. Mrc2000

assumed (based on copyright claims). [CC BY-SA 2.5

(http://creativecommons.org/licenses/by-sa/2.5)], via

Wikimedia Commons

By Alan Wilson (www.naturespicsonline.com: [1]) [CC BY-SA 3.0

(http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

By Shellie from Florida, USA (Grizzly Bear Alaska) [CC BY 2.0

(http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

By Jack Dykinga, edited by Fir0002 [Public domain], via Wikimedia Commons

By Pikaluk (Flickr: One Gorgeous Cow) [CC BY 2.0

(http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

By This vector version: Eric Gaba (Sting - fr:Sting) (NASA Astrobiology Institute, found in an article)

[Public domain], via Wikimedia Commons

Darwin’s Tree of Life

By Charles Darwin (HTML / JPG) [Public domain], via Wikimedia Commons

Genotype vs. Phenotype

Evolution will only act on outward traits

(phenotypes)

Recessive traits may be sheltered from

evolutionary pressures because they are not

always expressed

In several cases it has been shown to be

beneficial to be a heterozygote (Rr) over a

homozygote (RR)

Sickle Cell Anemia and Malaria

By Armando Moreno Vranich (Original work of Armando Moreno Vranich) [Public domain], via Wikimedia Commons

Lokal_Profil [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons

• Sickle cell trait is yellow, HbS (above)

• Malaria abundance (more is red, less is yellow

to the right) according to WHO data 2004

• The more common malaria is, the higher the

frequency of sickle cell anemia

• In normal conditions sickle cell anemia is an adverse

trait, but in the presence of malaria, having just one

copy of HbS gives survival advantage

Lesson 4Evidence of Evolution

Objective

Interpret evidence supporting the theory of evolution

(i.e., fossil, anatomical, physiological, embryological,

biochemical, and universal genetic code)

Evidence of Evolution Fossils – any evidence of ancient organisms

Most organisms that have live on earth are now extinct

The organisms that are seen in the fossil record show the

major patterns in earth’s history

Disappearance of the dinosaurs followed by the emergence of

mammals and birds

Fossil record is biased towards organisms with hard parts and

ecosystems that have slow decay

By Owen, Richard [Public domain], via Wikimedia CommonsBy FunkMonk (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or

GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

Comparative Anatomy & Physiology

Modern and extinct organisms have remarkable similarities in structure and function

Many organisms have vestigial structures (structures that are no longer useful to an organism, but passed on from ancestral organisms)

Finger bones in a whale flipper

A tail bone in humans, chimps, orangutans, and gorillas

By Christopher Walsh, Harvard Medical School [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5) or CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia

Commons

Vestigial Structures

By Meyers Konversionlexikon (Meyers Konversionlexikon 1888) [Public domain or Public domain], via Wikimedia Commons

By Meyer C. (domaine public (décès des auteurs 1917 et 1911)) [Public

domain], via Wikimedia Commons

Land mammal (cow) hip

bone vs. marine mammal

(whale) hip bone

Homologous vs. Analogous Homologous structures – structures that have clear

basis in common ancestry such as mammal limbs

Analogous structures- structures that have superficial

resemblance due to convergent evolution such as a

bird and bat wing

By John Romanes (1892): Darwin and after

Darwin [Public domain], via Wikimedia CommonsBy Волков Владислав Петрович (Own work) [CC BY-SA 4.0

(http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Homologous Structures

Forelimb Bone Structure

Creative Commons , courtesy of Jerry Crimson Mann via Wikimedia Commons

Analogous Structures

Bat vs. Bird Wing

By Internet Archive Book Images [No restrictions], via Wikimedia Commons

Comparative Embryology

The embryos of most animals develop in very similar patterns

Especially true for early stages

See page for author [Public domain], via Wikimedia Commons

Image from Popular Science Monthly (1892) vol. XLII pg. 752

Chick Tortoise Pig Human

Pharyngeal pouches

Post-anal tail

Which is Human?Dolphin5 weeks

By Starlarvae [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

A: early development

B: later development

1 2 3 4 5 6

DNA & Proteins

Organisms share huge amounts of DNA

The genetic code is universal

DNA and proteins have been used to determine

evolutionary relationships

Humans & Chimpanzees share over 96% of their DNA

Most of the 4% difference is in non-coding areas of the DNA

DNA & ProteinsGene that encodes leptin in apes.

300 nucleotides, few differences