Evolution concepts and mechanisms
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Transcript of Evolution concepts and mechanisms
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Evolution: Concepts o ut o Co ceptsand Mechanism
AP Biology Rapid Learning Series
Rapid Learning Centerwww.RapidLearningCenter.com/© Rapid Learning Inc. All rights reserved.
AP Biology Rapid Learning SeriesWayne Huang, PhD
Andrew Graham, PhDElizabeth James, PhD
Casandra Rauser, PhD Jessica Habashi, PhD
Sara Olson, PhDJessica Barnes, PhD
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Learning Objectives
Understand the concept of
By completing this tutorial, you will learn about:
Understand the concept of Evolution.
Apply the concept to your life and the environment around you.
Hone your skills of analysis by judging the soundness of
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by judging the soundness of Darwin’s theory of Evolution.
Evolution Concept Map
DNA ChemicalStructure
Genes
Chromosomes
MendelianLaws
IndependentAssortment
Law of Segregation
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Structure Function
Meiosis
Mitosis
Seg egat o
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Descent with Modification
Define “Descent With Modification”Natural SelectionNatural SelectionInheritance
Descent with Modification
Evolution is the change in inherited traits of a population.
Changes in genes are a function of mutations and selection.
Selection acts on the “generations”. Bacteria with a life span of 20 – 45
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minutes will evolve more rapidly then an organism that requires years to produce new generations.
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Natural Selection
To understand Darwin’s theory you need to
understand the meaning of : descent
DescentRefers to the idea that current day organisms arose from older ancestral species of : descent,
modification and natural selection.
over time.
M difi ti
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ModificationModification is a mechanism or process of interaction between the environment and an organisms heritable constitution adaptation
Natural SelectionThe process in which
favorable traits that are heritable become more common in subsequent
generations.
Definition of InheritanceHeritable and inheritance
describes a trait that can be passed down from one generation
to the next. This includes hair l h i ht tcolor, height etc.
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Modification = Natural SelectionThe main mechanism of modification is via “Natural Selection”.
Random variation of traits in a
population
Interaction of species with
Adaptationmore offspring
carrying
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environmentDifferential
reproductive success of
species carrying
particular traits
y gadvantageous
traits
Natural Selection Targets
Natural selection acts on the phenotype which is the observable characteristics of an organism.
Individuals with favorable phenotypes are more likely to survive and reproduce than those with less f bl h tan organism. favorable phenotypes.
Over time this will result in an “adaptation” which causes the organism to specialize for a certain niche. This can even lead to the emergence of
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If the phenotype is due to a genetic difference that genotype will be selected for and its frequency in the next generation increased.
even lead to the emergence of a new species.
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Genetic Variation and Selection
Genetic variation can occur when different organisms of a population
have different versions of a gene (allele)(allele).
Some traits are the result of a single gene.
Beak variation is an example.
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Some traits are the result of a single gene. Most traits are a result of interactions of many genes. Pleiotropy happens when a single gene influences many different phenotypic traits. A new mutation in the gene will have effects on
all traits simultaneously. Genetic linkage occurs when particular alleles are inherited
together.
Origin of the Species
Evolution and speciationSpecies originSpecies originPhylogenetic tree
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Speciation & Origin
Speciation is the evolutionary process giving rise to a new
species. There are four modes of natural selection that give rise to a
A species is a taxonomic group who's members can
interbreed and produce fertile offspring. natural selection that give rise to a
new species and involves geographic isolation: allopatric,
peripatric, parapatric and sympatric. New species may also be produced by genetic engineering and animal
husbandry.
fertile offspring.
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Kinds of Geographic SpeciationAllopatric speciation, a
population is split into two geographically isolated
ones. The isolated l ti th d
Parapatric speciation, the geographic zones of the two diverging populations are separate but do overlap.
populations then undergo genotypic divergence.
Peripatric speciation a new species is formed in small
Individual of each species may come in contact or mate but the fitness of the heterozygote is reduced so selected against.
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species is formed in small isolated peripheral
populations which are prevented from exchanging
genes with the main population.
Sympatric speciation species diverge while inhabiting the
same place e.g. insects which become dependent on
different host plants in the same area.
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Phylogenetic Tree of LifeA phylogenetic tree is a branching graph that shows the evolutionary interrelationships between species and shows the common ancestor. Each node represents the most recent common ancestor of the descendants. The lengths of the branches are time estimates.
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Phylogenetic TreeSpeciation events are shown in this phylogenetic tree. The relationship between ancestor and descendant is based on the number of
h d h i iOld world
kshared characteristics between them.
monkeys
New World Monkeys
Pro-simians
Gibb
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Orangutans
ChimpanzeesHumans
GorillasGibbons
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Darwin’s Theory
ReproductionGenetic variationGenetic variationDarwin’s Hypothesis
Reproduction Effects on Evolution
Sir Darwin, can you
First I observed that reproducing organisms will produce more
offspring then the environment can support if all offspring survive to y
tell me about your observations that
lead you to the theory of evolution?
pp p greproduce. This is the struggle for
existence.
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Darwin & Genetic Variation
Sir Darwin how does genetics impact your
I observed that for any given population of individuals there is a range of heritable characteristics.
genetics impact your theory?
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Survival & Inherited Traits
How does an organism’s traits
Survival depends on an organisms inherited traits. If a trait or set of traits enables an organism to survive and
effect a species?g
reproduce that species will survive.
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See these birds? Ability to fly high and hunt will be
helped by big wings in some environments. In other
environments like dense forests smaller wings will
have the advantage.
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Darwin’s Hypothesis
The hypothesis states that the attributes leading to a better fit in an environment leads to a greater
chance of survival and leaving
Disproportionate reproductive success within population
members gradually leads to a change in traits of that particular
behind viable offspring. population.
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Support for Darwin’s HypothesisThe theory is tested by looking
into the fossil record and studying taxonomy. By
comparing embryological and anatomical information
How can you test your theory?
anatomical information similarities and ancestry can be
discovered.
Today with modern molecular biology
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molecular biology techniques, it is possible to determine evolution on
the basis of genetics.
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Fossils and Evolution Support
Fossils are ancient impressions left by biological forms in sedimentary rocksedimentary rock. These impressions
often reveal the skeletal framework of an extinct
species.
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Fossil RecordsThe oldest fossils record the oldest
species living.
Younger fossils have species with traits common to older fossils plus some additional traits oradditional traits or
similar traits reorganized.
Fossil record
Jurassic "clams"
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indicates that there are shared traits
between ancestors and descendants.
This supports Darwin’s theory.
Cretaceous ammonite
Cretaceous ichthyosaur
Miocene beaver skull
Pleistocene sabertoothed cat
Pleistocene mammoth
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Taxonomy Science of Classification
Taxonomy is the science of classification. It is a
hierarchical grouping of i ith d diorganisms with descending
categories having more specific characteristics.
Organization is based on similarity of traits.
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Taxonomic Groupings
Taxonomic groupings are by shared traits among
different species leading to evolutionary relatedness.
The taxonomic grouping support Darwin’s theory that all species within a
group can be shown to be related to one another.
Flowers having similar traits would be grouped together.
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Comparative Taxonomy
Comparative Anatomy, Embryology:
These lines of evidence involve making i f i t t dcomparisons of various structures and
determining the degree of similarity among them.
For Example, flippers, wings, paws, hands.
All have similar bone structures, despite overall external differences - Remember descent with modification
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Genetics & Darwin’s TheoryGenetic evolution refers to
the change in the frequency of a gene or alleles in a
population.
Mechanisms of genetic evolution include: natural
selection, mutation, random , ,genetic drift and gene flow.
Natural selection is the best explanation for genetic evolution Once gene
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evolution. Once gene frequencies change and adaptation due to natural
selection occurs, advantageous genes will be selected again and
again because of directional selection.
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Evidence Summary
Types of Evidence
Does the evidence
corroborate Darwin’s Theorycorroborate Darwin s Theory
Fossil Record
Taxonomic Groups
Independent
Yes
Yes
Y
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Independent Traits
Genetics
Yes
Yes
ModernModern Evolutionary Theory
Variations of evolutionary theory.
Environmental effects and selection.
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Variations on Evolutionary Theory
My original theory believed that evolution
was a very gradual process. Referred to
Today evidence shows that evolution may be
better characterized bypas gradualism.
better characterized by punctuated equilibrium. A spurt and plateau pattern.
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Darwin
Environment and Evolution
The ecosystem plays a bigger role in stimulating
Yes, an example is dinosaur extinction which is thought
to be a consequence of climate change.
accumulation of new species then was previously
thought.
climate change.
Environmental changes can select for new traits required by that environment and lead
to new species formation.
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to new species formation.
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Gene Flow & In Breeding
There are other mechanisms of species modification that have a
minor role in evolution of species. These include: gene flow and non-
Gene flow: individual species breed outside their
tiThese include: gene flow and nonrandom mating (in breeding).
native group.Non random mating: in breeding mating is not
random.
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Question: ReviewThe process in which favorable traits become more frequent.
___________Natural selection
___________
___________
Taxonomy
Fossil record
Punctuated equilibrium
The science of classification.
Evolution is characterized by t d l t thi i
What record supports Darwin’s hypothesis?
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___________Punctuated equilibriumspurts and plateaus, this is known as what?
Minor mechanisms of evolution include these. ___________Gene flow, in-breeding
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Darwin’s theory may be
described as
Darwin’s theory may be
described as The major force The major force
Genetic variation can occur when
different
Genetic variation can occur when
different
Learning Summary
described as “descent with modification”.
described as “descent with modification”.
in evolution is natural selection
in evolution is natural selection
different organisms of a
population have different versions of a gene (allele).
different organisms of a
population have different versions of a gene (allele).
The fossil record and molecular biology support Darwin’s
theory.
The fossil record and molecular biology support Darwin’s
theory.
Survival of the fittest means an organism can create offspring
that are viable.
Survival of the fittest means an organism can create offspring
that are viable.
Congratulations
You have successfully completed the core tutorial
EvolutionRapid Learning Center
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