Chapter 14, 15 & 16 – Evolution

Why is the concept of evolution controversial to some people?

What is evolution?

Where did the concept of evolution come from?

How does evolution occur?

What does science know about the origin of life on Earth?

What does science know about the origin of humans?

What evidence exists of major evolutionary transitions?

Why is the concept of evolution controversial to some people?

• Some Christians view the Bible as scientifically accurate regarding Earth History

• Some Christians believe they know how much time has elapsed since the creation of the Earth

• Some people interpret the Bible in a manner that makes it conflict with the findings of science

• Some persons fail to distinguish between evolution, the origin of life on Earth, and Common Descent

What is evolution?

• Evolution – A change in the frequency of alleles in a population over time (p. 297)

• Evolution – Change over time in the characteristics of a population (p. 278)

Did you know…

…the term “evolution” is conflated with other concepts?

• The origin of the universe

• The origin of the 1st life form

• Common descent of species

Where did the concept of evolution come from? (p. 278-280)

1766 – Carolus Linnaeus“Species are the work of time”; “It is impossible to doubt, that there are new species produced by hybridization”; fossils not the result of a global flood

1778 - Georges LeClerc

proposed evolution, but no mechanism (theory); Modern species (are) conceived by nature and produced by time”

1823 - Etienne Geoffroy Saint-Hilaire “It is not repugnant to reason, that is to physiological principles, that the crocodiles of the present epoch could be descended through an uninterrupted succession from the antediluvian species” (Descent with modification)

Catastrophism vs. uniformitarianism (p. 280)

Georges Cuvier (1769-1832) – Catastrophism (major changes in earth’s crust result from geological catastrophes)

J. Hutton (1785) & C. Lyell (1830) – Uniformitarianism (past geological events can be explained by current geological processes)

“It is by faithfully weighing evidence, without regard to preconceived notions, by earnestly and patiently searching for what is true, that we have attained our dignity…”

Charles Lyell, 1872

Figure 14-4 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

youngestrocks

oldestrocks

Geological formations are the result of slow, repeated natural processes (p. 281)

Where did the concept of evolution come from?

Jean Baptiste Lamarck, 1801 – Evolution by (the theory of) inheritance of acquired characteristics (p. 281)

Evolution vs. Evolutionary theory

Evolutionary theories

Proposed mechanisms explaining why evolution occurs

Theories exist to explain facts (The fact of evolution is explained by theory)

Figure 14-4 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

youngestrocks

oldestrocks

What explains the specific patterns of fossils found in the geological record?

What explains the pattern of plant fossils in the geological record?

xThere are no fossilized flowering plants (or parts) in older sedimentary rock

What explains why dino coprolites do not contain flowering plant remnants?)

Coprolites (p. 279) record eaten life

Scientifically observable facts require explanation (why do we observe what we do?)

What explains flightless birds?

Figure E14-2 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

What best explains the presence of vestigial limbs in snakes? (p. 283)

What best explains the transitions observed in comparing historical patterns to modern patterns?

x

Science, March 17, 2000

What explains why limbless pythons possess limb genes?

Cohn, M., Tickle, C., Developmental basis of limblessness and axial patterning in snakes,

Nature, June 3, 1999, p. 474-479.

Scientifically observable facts require explanation (why do we observe what we do?)

Bacteria are becoming increasingly resistant to antibiotics

Scientifically observable facts require explanation (why do we observe what we do?)

Biological control of rabbits in Australia with Myxomatosis virus

1952 – 99% mortality

Today – 40% mortality

Why are there several types of distinct but similar Hawaiian honeycreepers living on the Hawaiian islands?

Was Hawaii always there?

What explains the different types of

preying mantises?

Scientifically observable facts require explanation (why do we observe what we do?)

Why are there several types of distinct but similar birds living in the Galapagos archipelago?

Where did the concept of evolution come from?

Charles Darwin & Alfred Wallace (p. 281-282), 1858 – Evolution by the mechanism of natural selection (theory to explain the fact of evolutionary change)

How does evolution occur? (p. 288-289)

Theory of evolution by natural selection depends on 4 postulates

1. Populations vary2. Traits are inherited3. Some individuals fail to survive and

reproduce4. Reproductive success is not random

-reproductive success depends on one’s characteristics

Evolution occurs when…

• A characteristic in a species is genetic

• Genetic variation exists for the gene(s) involved in the characteristic

• Selective pressure exists which confers a survival advantage to some individuals

Does genetic variation exist within a species?

Does some genetic variation confer a survival advantage in a competitive environment?

Alleles conferring a survival advantage will be maintained in a population

Sickle cell allele frequency is higher in descendants of central Africa (why?)

Even potentially harmful genetic variation may be adaptive in certain environments

Those with 2 sickle cell alleles have a 1/5 chance of surviving to reproductive age (will have sickle cell anemia)

Those with 1 sickle cell allele (heterozygous) have a 25% better chance of survival in a malaria environment

Does some genetic variation confer a survival advantage in a competitive environment?

Genetic variation is produced by gene mutations (p. 298)

Mutations, natural selection, and evolution (p. 299)

• Mutations are random

• Mutations do not occur in response to natural selection

• The process of evolution requires mutations

Evolution means…

• The gene pool (p. 297) of a population (frequency of alleles) changes over time as a consequence of selective pressures

• As the gene pool changes, so does the frequency of the characteristics influenced by the alleles selected for/against

Evolution is a change in allele frequencies in a population over time (p. 297)

= SS or Ss (susceptible to insecticide)

= ss (resistant to insecticide)

90% susceptible; 10% resistant

Survivors: 40% susceptible (Ss); 60% resistant (ss)

Next generation: 25% susceptible; 75% resistant

Individuals do not evolve; populations evolve

Changes within an individual is not evolution

Do Darwin’s finches meet the criteria for evolution?

Variation in gene expression can produce advantageous phenotypic variation

Science, Sept. 3, 2004

Speciation may occur as a result of changes in allele frequencies in a population over time (p. 316-324)

Resource partitioning is adaptive and can lead to reproductive isolation

Natural selection may be directional, stabilizing or disruptive (p. 309)

Common descent is an extension of evolution

Related species arose from a common ancestor through reproductive isolation and genetic divergence through natural selection

Hawaiian silverswords (28 species)

California tarweed

(Raillardiopsis scabrida)

The Theory of Evolution by natural selection explains the diversity of distinct but similar species

Adaptive radiation (p. 324)

3 of 300 species of cichlid fishes in Lake Malawi (9th largest lake in world)

The Theory of Evolution by natural selection explains the diversity of distinct but similar species

Adaptive radiation and the Composite Family (Asteracea – 23,000 species)

What is the best explanation for the facts we observe in nature?

Why do some fish move on land?

What is the best explanation for the facts we observe in nature?

Monotremes exhibit characteristics of reptiles, birds, and mammals?

What best explains the pattern of hominid fossils in geological history?

Did you know…

…the earliest reliably dated modern Homo sapiens were found in Israel?

Skhul Cave, Skhul Cave, Mt. Carmel, IsraelMt. Carmel, Israel90,000 years old90,000 years old(9 individuals)(9 individuals)

Is radiometric dating (p. 338) reliable?

Argon dating of Vesuvius (79 A.D.)

C14 dating of the Siloam Tunnel

Nature 425, 169 - 171 (11 September 2003)

2 Kings 20:20; 2 Chronicles 32:3,4

C14 dating validates the historical accuracy of the Old Testament, but YECs passionately argue that radiometric dating is grossly inaccurate

Humans have fewer chromosomes than

primatesChromosome Numbers in the

great apes:

human (Homo) 4646chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Did humans share a common ancestor with primates?

Chromosome Numbers in the great apes (Hominidae):

human (Homo) 46chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Testable prediction:Testable prediction: Common ancestor had 48 chromosomes (24 pairs) and humans carry a fused chromosome; or ancestor had 23 pairs, and apes carry a split chromosome.

Centromere

Telomere

Ancestral Chromosomes

FusionHomo sapiens

Inactivated centromere

Telomere sequences

“Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).”

“Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).”

Homo sapiens

Inactivated centromere

Telomere sequences

Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.

Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.

Human Chromosome #2 shows the exact point at which this fusion took place

Human Chromosome #2 shows the exact point at which this fusion took place