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Chapters 22-25 Evolution. Evolution. The definition of Evolution is: change over time Biological Evolution is: genetic change in population over time process by which modern organisms have descended from ancient organisms (slow change over long time)

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Chapters 22 25 evolution

Chapters 22-25Evolution


Evolution
Evolution

The definition of Evolution is:

  • change over time

    Biological Evolution is:

  • genetic change in population over time

  • process by which modern organisms have descended from ancient organisms (slow change over long time)

    • Even relatively quick evolution takes hundreds of thousands of years


History of evolutionary theories
History of Evolutionary Theories

  • Plato (427-347 B.C.) 2 worlds – 1 perfect, 1 imperfect. No change in organisms

  • Aristotle (384-322 B.C.) Organisms placed on “ladder of complexity / perfection” (scala naturae) No change

  • Judeo-Christian culture tried to explain the Creator’s plan as observable, natural phenomena – Natural Theology


History of evolutionary theories1
History of Evolutionary Theories

  • Carolus Linnaeus (1707-1832) Designed modern taxonomic system (binomial nomenclature)

    • From this system, we can (he didn’t) now infer evolutionary relationships between different groups

  • Geologists:

    • Georges Cuvier

    • James Hutton

    • Charles Lyell


History of evolutionary theories2
History of Evolutionary Theories

  • Georges Cuvier (1769-1832) helped develop Paleontology – study of fossils

    • Discovery of fossils (extinct species, similarities to modern species) put some doubt into Earth’s age and the origin of species

    • Cuvier explained differences in strata with “catastrophism” – floods, droughts, volcanoes, etc. changed local areas drastically over short periods of time

      • Organisms did not change, just migrate


History of evolutionary theories3
History of Evolutionary Theories

  • James Hutton (1726-1797) proposed that rocks, mountains, and valleys have been changed by water, wind, temperature, volcanoes, and other natural forces

  • He described the slow processes that shape Earth as “gradualism”


History of evolutionary theories4
History of Evolutionary Theories

  • Charles Lyell (1797-1875) – agreed with Hutton and said that scientists must always explain past events in terms of observable, PRESENT events and processes (“uniformitarianism” – what happens today happened yesterday)

  • They theorized Earth was much older than a few thousand (6,000) years, which didn’t set well in the traditional timeframe of Creationism


Age of the earth
Age of the Earth

  • We now know Earth is approximately 4.5 billion years old

  • Darwin used the work of Hutton and Lyell as a basis for his theories of slow change over time. Darwin’s work was a biological duplicate of Hutton and Lyell’s works in geology.


Geologists study earth s rocks
Geologists study Earth’s rocks

  • Fossils are preserved remains of ancient organisms

  • As fossils are found that don’t resemble organisms today, evidence increases that Earth has changed and that organisms have changed with it

  • Biologists and geologists date Earth’s past with the help of rocks


Geological time scale
Geological Time Scale

  • RELATIVE DATING

    • Technique used to determine age of fossils relative to other fossils in different strata

    • This technique is VERY approximate


Geological time scale1
Geological Time Scale

  • ABSOLUTE (RADIOMETRIC) DATING

    • Using radioactive elements in rock that decay at a steady rate to determine age

    • Decay measured in terms of HALF-LIFE

      • Half-life – time required for half the radioactive atoms in a sample to decay


Radioactive decay
Radioactive Decay

  • During radioactive decay, the atoms of one element break down to form something else

Lose a proton

6 protons

4 neutrons

5 protons

4 neutrons



K-40 half-life

Ar-40

K-40

Ar-40

  • Scientists often date rocks using Potassium-40, which decays to form the stable element Argon-40

  • It has a half life of 1.3 billion years

  • This is used to date the oldest rocks on earth

Formed

1.3 B yrs

2.6 B yrs


  • Uranium and Potassium are useful for dating rocks half-life

  • Carbon-14 is useful for dating things that were once alive such as wood, natural fiber, or cloth

    • C-14 is in the atmosphere; living things take it in their cells. After the organism dies, it doesn’t take in any more C-14. We can then compare the amounts of C-14 to N-14, knowing its half-life, to determine the age of the sample


Fossil evidence
Fossil Evidence half-life

  • Found in Sedimentary rock: layers of sand, silt, and clay in streams, lakes, rivers, and seas form rock that may have trapped living organisms

  • Fossil records – Show change over time. Some time frames are missing, but will show change of climate and geography.

  • Ex: Shark teeth in Utah

    • How can this be?


Jean baptiste de lamarck 1744 1829
Jean Baptiste de Lamarck (1744-1829) half-life

  • He also recognized that organisms were adapted to their environments and that they change

  • He relied on three ideas:

    • A desire to change (innate drive for perfection)

    • Use and disuse (Giraffe’s necks and vestigial organs)

    • Inheritance of acquired characteristics


Darwin s dilemma
Darwin’s Dilemma half-life

  • Set sail around the world in 1831 on HMS Beagle on a 5 year voyage

  • He had prior knowledge of geology (Lyell was a good friend) and agriculture that helped influence the development of his theory

  • Anchored all along the way and took samples from each place


Darwin s dilemma1
Darwin’s Dilemma half-life

  • He collected and studied beetles from Brazil, birds from Chile, and iguanas, tortoises, and finches from the Galápagos Islands

  • He noticed similarities between mainland (Ecuador) and Galapagos finches

  • Later, he noticed differences in beak size among finches from different islands in the Galapagos


Darwin s dilemma2
Darwin’s Dilemma half-life

  • Thomas Malthus – wrote paper on population growth in Great Britain

    • Population grows exponentially

    • Limiting factors on growth (carrying capacity)

      • Food

      • Area

      • Resources


Darwin s dilemma3
Darwin’s Dilemma half-life

  • Darwin applied Malthus’, Hutton’s, and Lyell’s work to species’ ability to change, and called the mechanism Natural Selection

    • Nat.Sel.: Process by which organisms with favorable variations survive and produce more offspring than less well-adapted organisms

  • He was sure Nat.Sel. was true, but he feared public ridicule. So, he kept his ideas to himself


Darwin s dilemma4
Darwin’s Dilemma half-life

  • Alfred Russel Wallace (1823-1913), working independently, came to the same conclusions as Darwin

  • He sent a manuscript to Darwin, basically for proofreading

  • “I never saw a more striking coincidence… so all my originality, whatever it may amount to, will be smashed.” – Charles Darwin

    • Letter to Charles Lyell, June 18, 1858

  • Darwin quickly abridged and published his work “On the Origin of Species”


Darwin s natural selection
Darwin’s Natural Selection half-life

  • Ernst Mayr, an evolutionary biologist, has dissected the logic of Darwin’s theory into three inferences based on five observations (Pg. 435)

  • Observations:

    • Tremendous fecundity

    • Stable populations sizes

    • Limited environmental resources

    • Variation among individuals

    • Heritability of some of this variation.


Darwin s natural selection1
Darwin’s Natural Selection half-life

  • Observation #1: All species have such great potential fertility that their population size would increase exponentially if all individuals that are born reproduced successfully.


Darwin s natural selection2
Darwin’s Natural Selection half-life

  • Observation #2: Populations tend to remain stable in size,except for seasonal fluctuations.

  • Observation #3: Environmental resources are limited.


Darwin s natural selection3
Darwin’s Natural Selection half-life

  • Inference #1: Production of more individuals than the environment can support leads to a struggle for existence among the individuals of a population, with only a fraction of the offspring surviving each generation.


Darwin s natural selection4
Darwin’s Natural Selection half-life

  • Observation #4: Individuals of a population vary extensively in their characteristics; no two individuals are exactly alike.

  • Observation #5: Much of this variation is heritable.


Darwin s natural selection5
Darwin’s Natural Selection half-life

  • Inference #2: Survival in the struggle for existence is not random, but depends in part on the hereditary constitution of the individuals.

    • Those individuals whose inherited characteristics best fit them to their environment are likely to leave more offspring than less fit individuals.


Darwin s natural selection6
Darwin’s Natural Selection half-life

  • Inference #3: This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over the generations.


Evidence in living organisms
Evidence in Living Organisms half-life

  • Comparative embryology:

    • All vertebrate embryos look similar to one another in early development, with the development of a tail and gill arches

      • Ernst Haeckel made early drawings – later exposed as frauds.

      • Gave fuel to anti-evolutionists


Evidence in living organisms1
Evidence in Living Organisms half-life

  • Comparative embryology:

    • These anatomical similarities indicate similar genetics are at work

    • Become more dissimilar as they grow

      • Cell specialization and differentiation

    • Common ancestor?



Evidence in living organisms3
Evidence in Living Organisms half-life

  • Comparative anatomy:

    • Homologous Structures

    • Analogous Structures

    • Vestigial Organs


Evidence in living organisms4
Evidence in Living Organisms half-life

  • Homologous Structures – structures that are similar in anatomy, but may serve very different functions

    • Ex: cat, whale, and human forearm


Homologous Structures half-life

Flying

Swimming

Running

Grasping


Evidence in living organisms5
Evidence in Living Organisms half-life

  • Analogous Structures – structures that serve similar functions, but have evolved independently of each other


Not half-life homologous;analogous

Not homologous;not analogous

Homologous;not analogous

Homologous; analogous


Evidence in living organisms6
Evidence in Living Organisms. half-life

  • Vestigial organs – organs that have little or no purpose in the organism; may become smaller or even disappear

    • Ex: Tailbone or appendix in humans

    • Ex: Tiny leg bones in snakes (boas and pythons) thought to come from 4 legged ancestor


Evidence in living organisms7
Evidence in Living Organisms half-life

  • Comparative biochemistry and molecular biology:

    • All cells have DNA, RNA, ribosomes, the same 20 amino acids and use ATP to do work

    • Similarities in biochemistry indicate relationship


Evidence in living organisms8
Evidence in Living Organisms half-life

  • Cytochrome c is a highly conserved respiratory protein containing 104 amino acids in humans


Evidence in living organisms9
Evidence in Living Organisms half-life

  • Amino acid differences of hemoglobin between species


What homologies tell us
What Homologies tell us… half-life

  • Similarities in structure and chemistry provide powerful evidence that all living things evolved from a common ancestor

  • Darwin Concluded:

    • Living organisms evolved through gradual modifications of earlier forms  descent with modification


What similarities tell us
What Similarities tell us… half-life

  • Two types of evolution can account for homologous AND analogous structures

    • Convergent evolution

    • Divergent evolution


What similarities tell us1
What Similarities tell us… half-life

  • Divergent evolution – two species evolve from a common ancestor (speciation)

    • They share similarities in anatomy, biochemistry, and embryology due to common ancestry

    • Explains homologous structures


What similarities tell us2
What Similarities tell us… half-life

  • Convergent – two species apparently becoming more similar

    • Two species have adapted in similar ways to similar environmental conditions

    • NOT due to common ancestry

    • Explains analogous structures


Convergent evolution
Convergent Evolution half-life

  • Ocotillo from California and allauidi from Madagascar have evolved similar mechanisms for protecting themselves


Convergent evolution1
Convergent Evolution half-life

  • Adaptive radiation of anoles has occurred on the islands of the Greater Antilles in a convergent fashion. On each island, different species of the lizards have adapted to living in different parts of trees, in strikingly similar ways.




Diversity of life
Diversity of Life half-life

  • Fitness:

    • Physical traits and behaviors that enable organisms to survive and reproduce in their environment arises from adaptation.

  • Adaptation allows species to be better suited to their environment and therefore can survive and reproduce.


Evolution on different scales
Evolution on Different Scales half-life

  • Microevolution – generation-to-generation change in a population’s allele frequencies

  • Macroevolution – origin of new taxonomic groups; speciation


4 driving forces behind evol
4 Driving Forces behind Evol. half-life

  • Mutation

    • Any change in the original DNA

    • ONLY ultimate source of variation in a population

  • Gene Flow

    • Movement of genes either into or out of a population

    • Migration – Immigration (add alleles) and Emigration (subtract alleles)


4 driving forces behind evol1
4 Driving Forces behind Evol. half-life

  • Genetic Drift

    • Change in the allele frequency in a small population by chance alone

      • Bottleneck Effect

      • Founder Effect


4 driving forces behind evol2
4 Driving Forces behind Evol. half-life

  • Genetic Drift

    • Bottleneck Effect: population undergoes a high mortality rate; genetic variation decreases dramatically

    • Ex: Cheetahs



4 driving forces behind evol3
4 Driving Forces behind Evol. half-life

  • Genetic Drift

    • Founder Effect: few individuals leave a large population to start their own; gene pool is very limited

    • Ex: polydactyly in PA Amish




4 driving forces behind evol4
4 Driving Forces behind Evol. half-life

  • Selection

    • Natural – differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment

      • Nature does the selecting


4 driving forces behind evol5
4 Driving Forces behind Evol. half-life

  • Selection (Natural)

    • Resistance – overuse of insecticides and antibiotics have bred resistant species of bugs and germs


4 driving forces behind evol6
4 Driving Forces behind Evol. half-life

  • Selection

    • Artificial – breeding of domesticated plants and animals

      • Humans intentionally do the selecting

      • Cabbage, cauliflower, Brussels sprouts, kale, kohlrabi and broccoli have a common ancestor in one species of wild mustard


4 driving forces behind evol7
4 Driving Forces behind Evol. half-life

  • Problems with artificial selection – not enough genetic variation


4 driving forces behind evol8
4 Driving Forces behind Evol. half-life

  • Selection (Sexual)

    • Intrasexual selection – selection within the same sex (competition, usually between males

      • Competition, usually between males

      • Exaggerated anatomy

Bighorn Sheep

Rocky Mountain Elk

Five-horned Rhinoceros Beetles

Stagbeetles


4 driving forces behind evol9
4 Driving Forces behind Evol. half-life

  • Selection (Sexual)

    • Intersexual selection – one sex selects mate based on phenotypes

    • Exaggerated anatomy



Directional selection
Directional Selection half-life

  • Environment selects against one phenotypic extreme, allowing the other to become more prevalent


Disruptive selection
Disruptive Selection half-life

  • Environment selects against intermediate phenotype, allowing both extremes to become more prevalent


Stabilizing selection
Stabilizing Selection half-life

  • Environment selects against two extreme phenotypes, allowing the intermediates to become more prevalent


Key points
Key Points half-life

  • Natural selection does not cause genetic changes in individuals.

  • Natural selection acts on individuals; evolution occurs in populations.

  • Evolution is a change in the allele frequencies of a population, owing to unequal success at reproduction among organisms bearing different alleles.

  • Evolutionary changes are not “good” nor “progressive” in any absolute sense.


Evolutionary theory
Evolutionary Theory half-life

  • Foundation on which the rest of the biological science is built. Collection of carefully reasoned and tested hypotheses about how evolutionary change occurs.


Speciation
Speciation half-life

  • What is a species?

    • Biological definition: a group of closely related organisms (population) that can interbreed to produce fertile, viable offspring


Speciation1
Speciation half-life

  • Why can’t/don’t populations interbreed?

    • Prezygotic barriers

    • Postzygotic barriers


Prezygotic barriers
Prezygotic Barriers half-life

  • Ecological (habitat) isolation – pops live in different habitats and do not meet

    • Parasites generally don’t transfer hosts

  • Temporal isolation – active or fertile at different times

    • Flowering plants pollinate on different days or different times of the day


Prezygotic barriers1
Prezygotic Barriers half-life

  • Behavioral isolation – differences in activities

    • Mating calls or actions are different


Prezygotic barriers2
Prezygotic Barriers half-life

  • Mechanical isolation – mating organs do not fit or match

    • Enough said

  • Gametic isolation – gametes cannot combine

    • Sperm destroyed in “different” vaginal cavity

    • Sperm and egg don’t fuse due to different membrane proteins


Postzygotic barriers
Postzygotic Barriers half-life

  • Hybrid inviability – hybrid zygotes fail to develop or reach sexual maturity

  • Hybrid infertility – hybrids fail to produce functional gametes


Summary
Summary half-life

  • 2 or more mechanisms may occur at once

  • Ex: Bufo americanus and Bufo fowleri are ecologically, temporally, and behaviorally isolated

  • Bufo americanus breeds in early spring in small, shallow puddles or nearby dry creeks

  • Bufo fowleri breeds in late spring in large pools and streams

  • Their mating calls also differ


Limitations of biological species concept
Limitations of Biological Species Concept half-life

  • How do you classify organisms that:

    • have the potential to interbreed, but do not do so in nature?

    • do not reproduce sexually?

    • exist only as fossils?

  • Alternative species concepts (ecological, pluralistic, morphological, genealogical) help address limitations


Modes of speciation
Modes of Speciation half-life

  • Allopatric (Greek, allos = other; Latin, patria = homeland)

  • Speciation due to geographic separation

    • Barrier stops gene flow between populations

    • Evolutionary change acts independently on each pop to establish reproductive barriers


  • Where the Amazon is very wide, tamarins on one side are brown, but on the other side are white. Where the Amazon is narrow, tamarins of both colors are found on either side


Allopatric speciation

A. leucurus monkey pops (those separated by wide rivers) are diverging toward speciation

A. harrisi

Allopatric Speciation

  • Birds can move freely across the gorge of the Grand Canyon; squirrels cannot

  • Two species arose when their original pop was disrupted by the carving of the canyon


A. harrisi monkey pops (those separated by wide rivers) are diverging toward speciation

A. leucurus


Allopatric speciation1
Allopatric Speciation monkey pops (those separated by wide rivers) are diverging toward speciation

  • If not given enough time, speciation will not occur

  • Also, even if they do come back together, they need to interbreed to be the same species


Allopatric speciation2
Allopatric Speciation monkey pops (those separated by wide rivers) are diverging toward speciation

  • Figure 24.11

  • Adaptive Radiation: evolution of many diversely-adapted species from a common ancestor

  • Ex: Hawaiian archipelago


Sympatric speciation
Sympatric Speciation monkey pops (those separated by wide rivers) are diverging toward speciation

  • Sympatric (Greek, sym = together; Latin, patria = homeland)

  • Speciation occurs in populations that share a habitat

  • Results from:

    • Ecological isolation

    • Polyploidy (number of sets of chromosomes increases)


Sympatric speciation1
Sympatric Speciation monkey pops (those separated by wide rivers) are diverging toward speciation

  • Polyploidy (number of sets of chromosomes increases)

  • A result of accidents in meiosis


Will speciation occur
Will Speciation Occur? monkey pops (those separated by wide rivers) are diverging toward speciation

  • p + q = 1

  • p2 + 2pq + q2 = 1

  • Will speciation occur? You tell me!

  • Hardy-Weinberg PPT 1

  • Hardy-Weinberg PPT 2


Evolutionary time scales
Evolutionary Time Scales monkey pops (those separated by wide rivers) are diverging toward speciation

  • Evolution can take a long time or can occur relatively quickly

    • Gradualism

    • Punctuated Equilibrium


Evolutionary time scales1
Evolutionary Time Scales monkey pops (those separated by wide rivers) are diverging toward speciation

  • Gradualism – big evolutionary changes are the result of many small ones over a long period of time


Evolutionary time scales2
Evolutionary Time Scales monkey pops (those separated by wide rivers) are diverging toward speciation

  • Punctuated Equilibrium – speciation occurs fairly rapidly then remain constant


Evolutionary novelties
Evolutionary Novelties monkey pops (those separated by wide rivers) are diverging toward speciation

  • Unique and highly specialized organs seem to complicated to have been naturally selected

  • Ex: eyes are really just photoreceptors; some are more developed, but all do the basic function: receive light


Evolutionary novelties1
Evolutionary Novelties monkey pops (those separated by wide rivers) are diverging toward speciation


Evo devo
Evo-devo monkey pops (those separated by wide rivers) are diverging toward speciation

  • Evolutionary development

  • A field of interdisciplinary research that examines how slight genetic divergences can become magnified into major morphological differences between species


Evo devo1
Evo-devo monkey pops (those separated by wide rivers) are diverging toward speciation

  • By blocking expression of one gene, researchers forced a chicken’s foot to develop to resemble a duck’s foot

  • Two embryos from the same animal


Evo devo2
Evo-devo monkey pops (those separated by wide rivers) are diverging toward speciation

  • Left, a normal chicken leg will develop

  • Right, a normal duck leg will develop… from a chicken embryo

  • Chicken leg: scaled with 4 digits

  • Duck leg: smooth and webbed

  • Duck legs, due to one genetic evolutionary difference, help ducks do many things chickens cannot, like swim


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