13. EVOLUTION

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Students are required to read the textbook for the instructor to be able to teach the concepts the course encompasses. (From FOUNDATION SKILLS in the Biology Department Master Syllabus.)
Students, do not just read these notes, to succeed in this class -- at least if you wish to have a high grade, you MUST use your textbook as a LEARNING TOOL!

The "minimal" reading centers in on the chapter figures. Look at the recommended figures and read the caption. If the caption does not have enough information to allow you to understand it, find the text discussing the figure. If you still do not understand the figure you may have to read the whole subchapter.
(Mader, Ed. 8.)
Ch. 17 -- Darwin and Evolution Chapter Introduction Figure, Figure 17.1, Figure 17.2, Figure 17.3, Figure 17.8, Figure 17A, Figure 17.10, Figure 17.11, Figure 17.12, Figure 17.13, Figure 17.14, Figure 17.15, Figure 17.16, Figure 17.17
Ch. 18 -- Process of Evolution Chapter Introduction Figure, Figure 18.2, Figures 18.3, Figure 18.4, Figure 18.5, Figure 18.9, Figure 18.10.
Ch. 19 -- Origin and History of Life Chapter Introduction Figure, Figure 19.1, Figure 19.5, Figures 19.6, Figure 19.9, Figure 19.10, Figure 19.11, Figure 19.12, Figure 19.13, Figure 19.14, Figure 19.15, Figure 19.16.


MAIN TOPICS OUTLINE

13.1 EVOLUTION
13.11 Different forms of Evolution.
13.12 Link to Genetics.
13.13 What can ‘evolve’?
13.14 How does Biological Evolution occur?
13.15 Speciation.
13.16 Evidences of Evolution

13.2 ORIGIN AND EVOLUTION OF LIFE

LECTURE OBJECTIVES

 1. Explain Lamarck's theory of inheritance of acquired characteristics, and contrast it with, and explain Darwin's theory of natural selection.
2. Differentiate between artificial and natural selection.
3. Review the evidence in support of evolution.
4. Define a biological species and explain why it is difficult to define species.
5. Discuss and list the steps in the speciation process.
6. Explain the concept of spontaneous generation.
7. Explain the endosymbiotic theory and how it applies to cell evolution.
8. Discuss the chemical, biological, and cultural evolution timetable.
9. Describe different mechanisms that contribute to genetic variation.
10. Explain why evolution cannot occur without genetic variation.
11. Trace the course of human evolution as we have diverged from other primates.
12. Define selected key terms.


Key Terms:

def. Acquired characteristic: A characteristic of an organism gained during its lifetime, not determined genetically, and therefore not transmitted to the offspring.
def. Allele Frequency: The relative abundance of each kind of allele, carried by the individuals, in a population.
def. Allele: alternative forms of a gene for a particular characteristic e.g. Free, Attached ear lobe
def. Allopatric Speciation: Speciation that follows geographic isolation of populations of the same species.
def. Biological Evolution: Change within a line of descent over time (change in allele frequency in a population of organisms); all species descending from ancestral species through a process of change brought about by natural selection.
def. Chemical Evolution: Change (increase) in the complexity of chemicals that eventually led to the first cell.
def. Cultural Evolution: Change in the behavior of a population of animals, especially humans, by learning behavior acquired by by members of previous generations.
def. Diploid organism: an organism having two sets of chromosomes – one from the maternal parent, the other from the paternal parent.
def. Evolution: chemical, biological, and/or cultural change over time
def. Gene Flow: physical movement of alleles in and out of populations as individuals leave (emigrate) or enter (immigrate), the outcome being changes in allele frequencies.
def. Gene Pool (Allele Pool): The various genotypes (alleles) in a population (pool of genetic variations in a population)
def. Gene: portion of DNA that determines characteristics (traits) e.g. EAR LOBE SHAPE
def. Geographic isolation: When two populations of a species live in different locations separated by a physical barrier, preventing gene flow.
def. Microevolution: small scale changes in allele frequencies.
def. Natural Selection: 1. A microevolutionary mechanism that encourages the passage of beneficial genes to future generations, and discourages harmful or less valuable genes. 2. A difference in survival and reproduction in a population -- that differ in one or more traits.


def. Reproductive Isolation: An absence of gene flow between populations
def. Speciation: The evolutionary process by which species originate.
def. Species (of sexually reproducing organisms): A group of organisms that interbreed under natural conditions and produce fertile offspring, and are reproductively isolated from other such groups.
def. Population: A group of individuals of the same species occupying a given area.



13.1. Evolution

• Fathers of Evolution (1859):

--- Charles Darwin
--- Alfred Wallace
13.11 Different forms of Evolution
def. Evolution: chemical, biological, and/or cultural change over time


1. Chemical Evolution: -- Primitive earth >> Macromolecule formation

2. Biological Evolution (in all living organisms) -- Protocell >> First humans on Earth

3. Cultural Evolution (in humans only) -- Agricultural Revolution 40,000 yrsa >> today

def. Chemical Evolution: Progressive change (increase) in the complexity of chemicals that eventually led to the first cell.
def. Biological Evolution: Progressive change in allele frequencies over time due to genetic adaptation of a population to its environment, and the idea that all organisms descended from common ancestors ("descent of modification"). (Change within a line of descent over time.)
def. Cultural Evolution: Progressive change in the behavior of the human population, by learning behavior developed by members of previous generations.


 13.12 Link to Genetics

Recommended textbook reading: (ed. 7: p. 302 - 303) This text also covers the Hardy-Weinberg Law which will not be covered in the lecture:

The Hardy-Weinberg Law states that if allele frequencies does not change, because of nonrandom mating, selection, migration, and genetic drift, then evolution will not occur.


def. Gene: portion of DNA that determines characteristics (traits), e.g. EAR LOBE SHAPE
def. Allele: alternative forms of a gene for a particular characteristic, e.g. Free, Attached Ear Lobe
def. Diploid organism: an organism having two sets of chromosomes – one from the maternal parent, the other from the paternal parent.
def. Allele Frequency: The relative abundance of each kind of allele, carried by the individuals, in a population.

• Evolution shows up as a Change in Allele Frequencies:

>> Some of the alternative forms of a trait (alleles) becomes more (or less) common.

We will return to this idea later.

>> changes in allele frequencies.


13.13 What can 'evolve'?

def. Population: A group of individuals of the same species occupying a given area.

def. Gene Pool (Allele Pool): The various genotypes (alleles) in a population (pool of genetic variations in a population)


13.13.1. Individuals in a Population Vary (Deviations in the Allele Pool)
1. Genetic information are in the genes -- specific regions on DNA.

2. In diploid organisms there are at least two forms -- these forms are called alleles

3. Individuals inherit different combinations of alleles. -- this gives variation to a population
13.13.2 Populations Evolve (Individuals do NOT evolve)
1. Individuals pass on their genes (alleles) to future generations of the population

2. If the frequency of certain alleles of a trait change in the population, then

3. Future generations change, they EVOLVE


13.14 How does Biological Evolution occur?
13.14.1 Genetics
• How and if evolution occurs is based upon:

A. genetic traits (the frequencies of alleles)
B. evolutionary mechanisms (microevolutionary processes)
C. survival characteristics


A. Genetic Traits

def. Allele Frequency: The relative abundance of each kind of allele, carried by the individuals, in a population.
def. Allele: One of two, or more, slightly different molecular forms of a gene that code for different versions of the same trait.


• Evolution shows up as a Change in Allele Frequencies

 >> some form of a trait, an allele becomes more or less common

 >> genetic traits will change from one generation to the next


http://chem.tufts.edu/science/evolution/HorseEvolution.htm

__________

Questions:

Does evolution occur?

or

Do allele frequencies change?

or

If you have a baby will it be a copy of you?

Answer:

A baby is different looking than the parents.

so

A baby has different alleles than the parents.

so

The allele frequency has changed (compared to the parents).

so

the potential for evolution is there (i.e., A CHANGE)
__________


B. Mechanisms

• The mechanisms of evolution are microevolutionary processes.
def. Microevolution: small scale changes in allele frequencies. 1. Natural Selection -- best trait survives/mate
2. Other mechanisms
a. Mutations -- DNA changes and gives rise to new traits
b. Nonrandom mating -- only organisms with certain traits mate
c. Random drift -- certain traits promoted by accident
d. No gene flow -- organisms isolated preventing gene mix

• The mechanisms of evolution influences the transmission of alleles from one generation to the next. (influences the “direction of evolution”)


C. Survival Characteristics

• Certain traits (alleles) are better for survival

def. Natural Selection: 1. A microevolutionary mechanism that encourages the passage of beneficial genes to future generations, and discourages harmful or less valuable genes. 2. A difference, in one or more traits, in population survival and reproduction.

• In order to survive an organism must:

1. Be able to adopt to changes

>> because the environment is always changing

2. The adaptations must be genetically controlled

>> because the survival characteristics must be passed on to the next generation,

(adaptations not under genetic control cannot be passed on.)

 13.14.2 Natural Selection


• Two competing theories: Lamarck vs. Darwin
Lamarckianism (inheritance of acquired characteristics)

def. Acquired characteristic: A characteristic of an organism gained during its lifetime, not determined genetically, and therefore not transmitted to the offspring.

• Acquired characteristics are not genetically controlled (not inherited), and therefore do not influence natural selection.


Darwinism (natural selection)

def. Natural Selection: 1. A microevolutionary mechanism that encourages the passage of beneficial genes to future generations, and discourages harmful or less valuable genes. 2. A difference, in one or more traits, in population survival and reproduction.

• Natural selection is the idea that some individuals whose gene combinations favor life in their surroundings, will be most likely to survive, reproduce, and pass their genes on to the next generation. – "survival of the fittest".

• Most biologist agree that evolution occurs as a result of

-- Natural Selection

-- Artificial Selection


NATURAL SELECTION is a theory -- on how evolution has occurred
(a mechanism).

EVOLUTION is a concept. -- that most people today accept as scientific fact (a scientific law)

13.14.2 Natural Selection Steps

• Evolution using Natural Selection as the mechanism works as follows:

1. Overpopulation: Living organisms have more offspring than can survive.

2. Genetic Variation: These offspring have variations.

3. Struggle for Survival: Some variations give an advantage, and some variations give a disadvantage, in the struggle for survival.

4. Survival & Reproduction: Those organisms with most useful variations will survive, reproduce, and pass on their useful traits to their offspring.

>> changes in allele frequencies.

5. Speciation: In this way, living organisms will change. Given enough time, new species will evolve.

>> this is a long term result of evolution and it means that all organisms have a "common descent".


Not On-Line Dr. Thinkwell: Lamarck-AqChar/Darwin-NatSel/Giraffe ../Thinkwell_f/14_Lam_Darw1_gir_2627_2650.mov

Not On-Line Dr. Thinkwell: Lamarck-AqChar/Darwin-NatSel/Woodpecker ../Thinkwell_f/14_Lam_Darw2_wPe_2628_2651.mov

13.15 Speciation
• Long term result of evolution

def. Species (of sexually reproducing organisms): A group of organisms that interbreed under natural conditions and produce fertile offspring, and are reproductively isolated from other such groups.
def. Speciation: The evolutionary process by which species originate.
def. Gene Flow: physical movement of alleles in and out of populations as individuals leave (emigrate) or enter (immigrate), the outcome being changes in allele frequencies.
def. Reproductive Isolation: An absence of gene flow between populations
def. Allopatric Speciation: Speciation that follows geographic isolation of populations of the same species.
def. Geographic isolation: When two populations of a species live in different locations separated by a physical barrier, preventing gene flow, e.g., two species of squirrels found on opposite sides of the Grand Canyon.


• Speciation Process, sequence of events that may result in a new species:


1. Geographic isolation

Some populations of a species will be separated, geographically isolated, from other populations (prevention of gene flow)

i. Environmental differences.
ii. Mutation – new genes, and these new genes will be kept separated (not shared) from other populations.

2. Natural selection (and other microevolutionary processes)

 -- will influence the populations

3. Changes in allele frequencies (genetic difference in the populations)

Over a long period of time, genetic differences will accumulate (reproduction impossible between the two former populations of the same species)
13.16 Evidences of Evolution
• These are evidences of Common Descent -- i.e., all living organisms descended from the same origin. (See your textbook for additional evidence):

A. Fossil record

B. Comparative embryology

-- Related organisms develop similarly.

>> animals looking different as adults, resemble each other in immature stages

-- e.g.,gill slits

The early embryos of vertebrates strongly resemble one another because they inherited the same ancient plan for development

C. Comparative anatomy

 -- Related organisms remain alike
>> evolutionary related organisms remain alike in many structures

-- Homologous Structures

-- Related organisms share
a unity of plan

– plants with flowers, compared to ferns (Angiosperms)
– animals with feathers (Birds)
– animals that nurse their young from mammary glands (Mammals)
– animals with similar bone structures (vertebrates)


-- Vestigial Structures

D. Comparative biochemistry

-- All organisms have the same basic biochemical molecules

1. DNA is the universal genetic material (different combinations – but same chemicals).

2. Protein is the universal structural chemical and the universal chemical of enzymes.
-- Cytochrome C
-- Hemoglobin

3. ATP is the universal source of energy.

-- related organisms have similar chemical structures - (e.g., Man & Chimp)
-- related organisms have DNA derived from a common ancestor

 >> since DNA carries the code for protein synthesis
>> related animals are expected to have similar proteins.

13.2 ORIGIN AND EVOLUTION OF LIFE
• Continental Drift & Plate Tectonics
 -- the map of the Earth has not always been the same -- the continents have moved and continue to move
not
on-line
Continental Drift		 TimeTable
Plate Tectonics
Scroll down for Plate Tectonic College alias on the DeskTop




































Click Plate Tectonic College alias on the DeskTop (not on-line)





































----
• Evolutionary Timetable
 -- for the formation of the solar system, earth, & life


1. Start of CHEMICAL EVOLUTION

15 billion yrsa

SOLAR SYSTEM BEGINS TO FORM

4.5 billion yrsa

EARTH FORMED
-- no oxygen
-- too hot for life (and water)
-- the crust cooled slowly and hardened
-- water vapor in the atmosphere condensed >>> rain

OCEANS FORMED
-- water erosion of rocks (chemicals for chemical reactions)
-- lightning, volcanic heat, & UV radiation (energy for reactions)

ORGANIC MOLECULES FORMED

2. Start of BIOLOGICAL EVOLUTION

3.8 billion yrsa

PROKARYOTIC ORGANISMS (oldest known fossils)
-- anaerobic (no oxygen)
-- heterotrophs (used an organic source of energy – "eating")


3.5 billion yrsa

PHOTOSYNTHETIC BACTERIA
-- anaerobic (no oxygen)
-- autotrophic (used sunlight energy, produced oxygen - waste)

OXYGEN FORMED

2.5 billion yrsa

AEROBIC BACTERIA (mitochondrial-like bacteria)

-- used oxygen (aerobic, prokaryotic)
-- used energy more efficiently (Krebs cycle)

ENDOSYMBIOTIC RELATIONSHIPS (organisms start to interact)

1.8 billion yrsa

EUKARYOTIC ORGANISMS (Protistans)

0.75 billion yrsa (750 mya)

MULTICELLULAR ORGANISMS -- incl. the FIRST ANIMALS

0.55 billion yrsa (550 mya)

 “Cambrian Explosion” -- all modern phyla formed

0.45 billion yrsa (450 mya)

 first fishes (jawless)
first plants (nonvascular)
first insects
first amphibians

0.4 billion yrsa (400 mya)

 first vascular plants
first gymnosperms

0.35 billion yrsa (350 mya)

 amphibians decline
first reptiles
0.25 billion yrsa (250 mya)
Pangaea
first dinosaurs
first mammals

0.15 billion yrsa (150 mya)
Gondwanaland / Laurasia
first birds
first flowering plants (angiosperms)
first placental mammals

0.066 billion yrsa (66 mya)
Earth when the dinosaurs went extinct

last dinosaur, mammals diversify
not
on-line
CNN: Evidence of Asteroid Impact
CNN: Measuring Time


0.060 billion yrsa (60 mya)

first primates (prosimians)

not
on-line
Binocular Vision

0.035 billion yrsa (35 mya)

first anthropoids (monkeylike primates)

0.024 billion yrsa (24 mya)

first hominoids (apelike primates)

not
on-line
Ape Skulls

0.018 billion yrsa (18 mya)

Asian ape evolutionary line separates from the African ape line
-- gibbon line
-- orangutan line

0.010 billion yrsa (10 mya)

African ape evolutionary lines diverge
-- gorilla line
-- chimpanzee line
-- pygmy chimpanzee line

0.005 billion yrsa (5 mya)

Pygmy chimpanzee line separates from the human line

0.0045 billion yrsa (4.5 mya)

OLDEST HOMINID FOSSILS
-- Australopithecus sp.

0.003 billion yrsa (3 mya)

FIRST HOMO sp.
-- Homo habilis
-- Homo erectus
-- Homo sapiens


3. Start of CULTURAL EVOLUTION
0.00004 billion yrsa (40,000 yrsa)
Earth today
AGRICULTURE


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