Evolution/Basics Lecture Outline
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Based on Pough et. al, 1989. Vertebrate Zoology - 3rd Ed. MacMillan
Hickman et al., 2001. Integrated Principles of Zoology - 11th Ed. William C.
Brown Publishers
Biology 222 Vertebrate Zoology
Intro to Vertebrates/Evolution - The Basics
Theme: The turtle as a typical vertebrate.
Demonstration - Turtle
Question - what is a vertebrate?
characteristics - size from 0.1 gram to 100,000 kg
length to 60m
all habitats
all types of feeding strategies
presence of a vertebral column (and associated brain, spinal cord,
etc.)
50,000 extant species, up to 500,000 extinct species
Some examples of vertebrates:
Myxini - hagfish
Cephalaspidomorphi - lampreys 50 species (with myxinoidea)
Elasmobranchii - sharks, skates, rays - 800 species
Holocephali - ratfish
Cladista - bichers, reed fish
Chondrostei - sturgeon, paddlefish
Neopterygii - gar, bowfin
Teleostei - other ray-finned fishes - 21,000 species of fish
Actinistia - coelocanth - 1 species
Dipnoi - lungfish - 6 species
Microsauria/Caudata - salamanders & caecilians - 350 species
Temnospondyli/Anura - frogs and toads - 3,500 species
Testudomorpha/Testudines - turtles - 225 species
Lepidosauria - tuatara, lizards, snakes - 5,800 species
Archosauria - crocodiles - 21 species crocs
Aves - birds - 9,000 birds
Synapsida - mammals - 4,000 species
(17 groups)
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Biology 222 Vertebrate Zoology
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Evolution/Basics Lecture Outline
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Biology 222 Vertebrate Zoology
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Classification of the turtle:
Kingdom Animalia (Plantae, Fungi, Protista, Monera)
Phylum Chordata
Class Anapsida
Order Testudomorpha
Family Emydidae
Genus Terrapene - box turtles
species carolina - eastern box turtle
Terrapene carolina (Linnaeus, 1758)
Note forms of order names, family names, proper handling of specific epithet
(including author).
Graptemys geographica (Le Seur) - 1827
Note common names
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Biology 222 Vertebrate Zoology
Evolution/Basics Lecture Outline
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Taxa - any hierarchical grouping - a level
Basic taxonomy - Holotype - part of species description
must be deposited in museum
must be mentioned in text
is the basis for future assignment of the name
paratype
additional specimens representing the known variation of the
species
priority - first description is the valid one
each species must have unique specific epithet
Commission of Zoological Nomenclature
Evolution
gene - basic unit of selection - DNA code for protein AKA locus
allele - differing form of gene - same protein, slightly different
genotype - all the genes of an individual
Haploid - only one allele for each gene - sex cell
diploid - two alleles for each gene - somatic cell
Homozygous - both alleles for a given locus are identical (diploid cell)
Heterozygous - two different alleles at a given locus
phenotype - the resulting traits (structural, behavioral, etc.) of a given
genotype
Variation - mutations are changes in the genetic code - they give rise to new alleles alleles are combined into new genotypes (and phenotypes) through sexual reproduction
and recombination. Variation is the basis for evolution.
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1.
There are differences in organisms (evidence gathered on Beagle)
2.
3.
There is a struggle for existence (Malthus)
In the struggle, certain differences will give those organisms
possessing them an
advantage (Darwin's contribution)
These organisms will survive and reproduce in greater numbers
(differential reproduction)
4.
5.
Over long periods of time (Lyell), the whole species will change
(evolution)
heritability - any variation must exist in the genes - be heritable - if natural selection is to
act on it.
Natural Selection - differential reproduction of differing alleles (genotypes, phenotypes)
different levels
selection of individuals (and associated genes)
genic selection (alleles going into sex cells)
group or interdemic selection - species selection (controversial)
Types of natural selection:
----- use bell drawings ----directional selection
stabilizing selection - driving force of allopatric speciation
disruptive selection - driving force of sympatric speciation
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Biology 222 Vertebrate Zoology
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Fitness - measure of the reproductive success (of an allele or individual)
Inclusive fitness - fitness gained by the copies of your genes carried by relative's kin.
sometimes one can maximize his own fitness by foregoing reproduction to help
kin rear offspring - altruistic behavior
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Types of variation :
1 - individual - each individual has a unique assortment of genes
(genotype), and thus a unique phenotype.
2 - polymorphism - several discrete phenotypes exist in a population
3 - sexual dimorphism - a type of polymorphism where the phenotypes vary
according to sex. Often reinforced by sexual selection
4 - geographic - variation in populations according to geographic
location.
polytypic - a species with geographic variants pronounced enough
to be subspecies.
monotypic - a species which shows little variation over its range.
Speciation
speciation - the separation of a population into distinct breeding groups via natural
selection and other genetic processes, including chance.
biological species - groups of actually (or potentially) interbreeding natural populations
which are reproductively (genetically) isolated from other such groups.
gene flow - the mixing of alleles in a population through breeding.
if effective gene flow exists, then speciation cannot occur.
reproductive isolating mechanisms - keep organisms of different species
interbreeding
1.
2.
premating
a)
b)
c)
d)
postmating
a)
b)
c)
d)
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from
habitat isolation
temporal isolation
behavioral isolation
mechanical isolation
gametic isolation
zygote mortality
hybrid sterility
fitness of offspring
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effects of size:
if a population is large - becomes subdivided - strong (but different) natural
selection on each "pocket" --> speciation (assuming low gene flow)
if a population is small - genetic drift ---> speciation (assuming low
gene flow.
genetic drift - the tendency for random chance to change allelic frequencies within a
population - pronounced in small populations.
effective population size: the current population size may not be critical in the species'
evolution. Often low population size is.
bottleneck effect - powerful sorting and genetic drift effects from single period of low
population size
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founder effect - if a population is formed initially by few individuals, genetic diversity is
low and subsequent evolution will be drastically affected.
Biology 222 Vertebrate Zoology
adaptive radiation - the evolution into many different niches by a single species (through
speciation) - usually requires colonization of an ecologically void area (island)
Models of speciation:
allopatric - geographic isolation ---> genetic drift and/or natural selection --> speciation
sympatric - no geographic isolation - mutation ---> reproductive isolation --> genetic drift
and/or natural selection --> speciation
Example: Galapagos finches - Figure 6-22 pg. 120
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Isolation on continents:
mountain ranges - rivers - deserts
refugia and speciation
gradualism vs. punctuated equilibria - use figure 6-24, 6-25, pg. 121
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