UNIT VIII EVOLUTION Big Campbell Ch 22-28, 31 Baby Campbell Ch 13-17 Hillis Ch 15-18.
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Transcript of UNIT VIII EVOLUTION Big Campbell Ch 22-28, 31 Baby Campbell Ch 13-17 Hillis Ch 15-18.
UNIT VIII EVOLUTION
• Big Campbell Ch 22-28, 31
• Baby CampbellCh 13-17
• HillisCh 15-18
I. EVOLUTION - WHAT IS IT?o “Descent with Modification”
o
“Change”
Population
November 24, 1859
II. Hardy-Weinberg Principle• Means used to determine if a population
is evolving• Predicts allele frequency in a non-
evolving population; that is, a population in equilibriumo States that allele frequencies in a
population will remain constant from generation to generation if five conditions are met
II. Hardy-Weinberg Principle, cont• Five Conditions for Hardy-Weinberg Equilibrium:
1)
2)
3)
4)
5)
If any of these conditions are not met, evolutionary change will occur!
II. Hardy-Weinberg Principle, cont• Hardy-Weinberg Equation
p = frequency of one allele (A) q = frequency of other allele (a) p + q =
• Therefore, p = q =
• Genotype Frequency AA = aa = Aa =
• To determine distribution of genotype frequencies in a population →
II. Hardy-Weinberg Principle, cont
Hardy-Weinberg Practice Problems1. If you know that you have 16% recessive fish (bb), . . .
• q 2 =• q = • Therefore, p =
To calculate the frequency of each genotype …• p2 =• 2pq =
What is the expected percentage of heterozygous fish?
II. Hardy-Weinberg Principle, cont• Hardy-Weinberg Practice Problems, cont
2. If in a population of 1,000, 90 show recessive phenotype (aa), use Hardy-Weinberg to determine frequency of allele combinations.
3. In people light eyes are recessive to dark. In a population of 100 people, 36 have light eyes. What percentage of the population would be …
• Homozygous recessive?
• Homozygous dominant?
• Heterozygous?
II. Hardy-Weinberg Principle, cont4. The ability to roll the tongue is a dominant trait. … 75% of the students at Kingwood High School have the ability to roll the tongue. Assuming the student population is 2526,
a) How many students would exhibit each of the possible genotypes?
b) How many students would exhibit each of the possible phenotypes?
III. A HISTORY OF EVOLUTIONARY THEORY
• Aristotle (384-322 BCE)o Scala Naturae
• Carolus Linnaeus (1707-1778)o Taxonomy
III. A HISTORY OF EVOLUTIONARY THEORY, cont
III. A HISTORY OF EVOLUTIONARY THEORY, cont• Charles Darwin (1809-1882)
III. A HISTORY OF EVOLUTIONARY THEORY, cont• Darwin, cont
o Observed many examples of adaptationsInherited characteristics
that enhance organisms’ survival and reproduction
o Based on principles of natural selectionPopulations of organisms
can change over the generations if individuals having certain heritable traits leave more offspring than others
Differential reproductive success
III. A HISTORY OF EVOLUTIONARY THEORY, cont
• Darwin’s Conclusions Based on his own observations and
the work of other scientists, Darwin realized … o Members of a population often
vary greatly in their traits.o Traits are inherited from parents to
offspring.o All species are capable of
producing more offspring that their environment can support, therefore …
III. A HISTORY OF EVOLUTIONARY THEORY, cont Darwin concluded …
o Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals.
o This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.
Descent with Modification
III. A HISTORY OF EVOLUTIONARY THEORY, cont• Artificial Selection
III. A HISTORY OF EVOLUTIONARY THEORY, cont
• Post-DarwinNeo-Darwinism/Modern Synthesis Theory
Epigenetics
IV. EVIDENCE FOR EVOLUTION
• Direct Observationo Antibiotic/Drug Resistance
IV. EVIDENCE FOR EVOLUTION, cont• Fossil Record
o Succession of forms over timeo Transitional Linkso Vertebrate descent
IV. EVIDENCE FOR EVOLUTION, cont
• Homologyo Homologous structures
o Vestigial organsSnakesCetaceansFlightless birds
IV. EVIDENCE FOR EVOLUTION, cont
o Convergent Evolution Independent evolution of similar features in different lineagesAnalogous structures
IV. EVIDENCE FOR EVOLUTION, cont
• Biogeographyo Geographical distribution of
specieso Continental Drift
Pangaeao Endemic specieso Islands are inhabited by
organisms most closely resembling nearest land mass
IV. EVIDENCE FOR EVOLUTION, cont
• Comparative Embryologyo Pharyngeal
Pouches Gill slits
o Tail
IV. EVIDENCE FOR EVOLUTION, cont
• Molecular Biologyo Similarities in DNA,
proteins, genes, and gene products
o Common genetic code
V. MICROEVOLUTION
• A change in the gene pool of a population over a succession of generations
• Five main causes:
V. MICROEVOLUTION, cont• Genetic Drift
o Changes in the gene pool due to chance. o More often seen in small population sizes. o Usually reduces genetic variability. o There are two situations that can drastically reduce population size:
Bottleneck EffectFounder Effect
V. MICROEVOLUTION, cont
• Bottleneck Effect Type of genetic drift resulting
from a reduction in population (natural disaster)
Surviving population is no longer genetically representative of the original population
• Founder Effect Due to colonization by a
limited number of individuals from a parent population
Gene pool is different than source population
V. MICROEVOLUTION, cont
• Gene FlowGenetic exchange due to the
migration of fertile individuals or gametes between populations – tends to reduce differences between populations
V. MICROEVOLUTION, cont
• MutationsA change in an
organism’s DNA (gametes; many generations); original source of genetic variation (raw material for natural selection)
V. MICROEVOLUTION, cont
• Nonrandom Mating Inbreeding Assortative mating
V. MICROEVOLUTION, cont
• Natural Selection
Only form of microevolution that adapts a population to its environment
VI. VARIATION IN POPULATIONS
• Genetic Variation is the “substrate” for evolution
• Maintained through … Polymorphism
Coexistence of 2 or more distinct forms of individuals (morphs) within the same population
Geographical Variation Differences in genetic
structure between populations (cline)
VI. VARIATION, cont Mutation and Recombination
Diploidy 2nd set of chromosomes hides
variation in the heterozygote
Balanced Polymorphism Heterozygote Advantage Frequency-Dependent Selection
o Survival & reproduction of any 1 morph declines if it becomes too common
o Parasite/host
VII. A CLOSER LOOK AT NATURAL SELECTION
• Natural Selection Not a random process → Dynamic processIncreases frequency of alleles that provide reproductive
advantageFitness
VII. CLOSER LOOK AT NATURAL SELECTION, cont
Natural selection is the only evolutionary mechanism for adaptive evolution
VII. CLOSER LOOK AT NATURAL SELECTION, cont
• Three ways in which natural selection alters variationDirectional
Disruptive
Stabilizing
VII. CLOSER LOOK AT NATURAL SELECTION, cont
• Sexual Selection Can result in sexual
dimorphism - secondary sex characteristic distinction
Intrasexual Selection
Intersexual Selection
VIII. MACROEVOLUTION
• Macroevolution Refers to the formation of new
taxonomic groups Due to an accumulation of
microevolutionary changes AKA Speciation
• “Species” Morphological Species Concept
Ecological Species Concept
Phylogenetic Species Concept
VIII. MACROEVOLUTION, cont
• Biological Species Concept Described by Ernst Mayr in
1942 A population or group of
populations whose members have the potential to interbreed and produce viable, fertile offspring; in other words, similar organisms that can make babies that can make babies
Can be difficult to apply to certain organisms . . .
VIII. MACROEVOLUTION, cont
• Reproductive Isolationo Prevent closely
related species from interbreeding when their ranges overlap.
o Divided into 2 typesPrezygoticPostzygotic
VIII. MACROEVOLUTION, cont
Prezygotic Reproductive Barriers
VIII. MACROEVOLUTION, cont
Postzygotic Reproductive Barriers
VIII. MACROEVOLUTION, cont• Speciation
o Fossil record shows evidence of bursts of many new species, followed by periods of little chanceKnown as punctuated equilibrium
o Other species appear to change more graduallyGradualism fits model of evolution proposed by Darwin
VIII. MACROEVOLUTION, cont• Modes of Speciation
Based on how gene flow is interrupted
Allopatric Populations segregated by a
geographical barrier; can result in adaptive radiation (island species)
Sympatric Reproductively isolated
subpopulation in the midst of its parent population (change in genome); polyploidy in plants; cichlid fishes
IX. HISTORY OF LIFE ON EARTH
IX. HISTORY OF LIFE ON EARTH, cont
• Formation of Organic Moleculeso Oparin/Haldane Hypothesis
Primitive Earth’s atmosphere was a reducing environment
No O2
Early oceans were an organic “soup”Lightning & UV radiation provided
energy for complex organic molecule formation
o Miller/Urey ExperimentTested Oparin/Haldane hypothesisSimulated atmosphere composed of
water, hydrogen, methane, ammoniaAll 20 amino acids, nitrogen bases,
ATP formedHypothesis was supported
IX. HISTORY OF LIFE ON EARTH, cont
IX. HISTORY OF LIFE ON EARTH, cont
IX. HISTORY OF LIFE ON EARTH, cont• Mass Extinctions
IX. HISTORY OF LIFE ON EARTH, cont• Adaptive Radiation
o Periods of evolutionary change, increased speciation
o Often due to increased ecological niches in communities
o Also seen in organisms with major evolutionary innovations
IX. HISTORY OF LIFE ON EARTH, cont
X. PHYLOGENY• Taxonomy
Linnaeus Binomial nomenclature Taxon (taxa)
X. PHYLOGENY, cont
• Evolutionary history of an organism
X. PHYLOGENY, cont• Phylogenetics
Tracing of evolutionary relationships
Illustrated with diagrams known as phylogenetic trees
X. PHYLOGENY, cont• Important to distinguish
between homologies and analogies Homologies are
likenesses attributed to common ancestry
Analogies are likenesses attributed to similar ecological roles and natural selection
• May also be done at a molecular level Known as molecular
systematics
X. PHYLOGENY, cont• Cladistics
Use of common ancestry as primary criterion for classificationSpecies are put into groups known as clades
Includes ancestral species + descendents Clades are sub-categorized as
Monophyletic – Includes ancestral group and all descendents
Paraphyletic – Includes ancestral group and some, but not all descendents
Polyphyletic – Includes taxa with multiple ancestorsParsimony – Also known as Occam’s Razor
X. PHYLOGENY, cont
X. PHYLOGENY, cont