unit 4 review mechanisms of evolution. copyright © 2005 pearson education, inc. publishing as...

Unit 4 Review

Mechanisms of Evolution

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 22Chapter 22

Descent with Modification: A Darwinian View of Life


Darwin worked in a historical CONTEXT!

• Others’ ideas shaped Darwin’s thinking…

Figure 22.2

Linnaeus (classification)Hutton (gradual geologic change)

Lamarck (species can change)

Malthus (population limits)Cuvier (fossils, extinction)

Lyell (modern geology)

Darwin (evolution, nutural selection)

Mendel (inheritance)

Wallace (evolution, natural selection)

1750

American Revolution French Revolution U.S. Civil War

1800 1850 19001795 Hutton proposes his theory of gradualism.

1798 Malthus publishes “Essay on the Principle of Population.”

1809 Lamarck publishes his theory of evolution.1830 Lyell publishes Principles of Geology.

1831–1836 Darwin travels around the world on HMS Beagle.

Darwin begins his notebooks on the origin of species.1837Darwin writes his essay on the origin of species.1844

Wallace sends his theory to Darwin.1858

The Origin of Species is published.1859Mendel publishes inheritance papers.1865


• Elements of Darwin’s theory of…Evolution by Natural Selection?

– organisms overproduce offspring

– members of a population differ in adaptations

– competition for limited resources

– survival of the fittest

– population changes over time

• What was Darwin missing?

– He couldn’t describe a mechanism for the variation in adaptations. Can you?


Artificial Selection

• Artificial selection: Humans have modified other species by selecting and breeding individuals that possess desired traits

Figure 22.10

Terminalbud

Lateralbuds

Brussels sproutsCabbage

Flowercluster

Leaves

Cauliflower

Flowerandstems

Broccoli Wild mustard Kohlrabi

Stem

Kale


• If an environment changes over time

– Natural selection may result in adaptation

• Does the individual or population evolve?

• The alternative to adapting?


Caused by the pesticide?


Homologous structures:

– variations on a structural theme inherited from a common ancestor

Figure 22.14Human Cat Whale Bat


• Comparative embryology

– Reveals additional anatomical homologies not visible in adult organisms

Figure 22.15

Pharyngealpouches

Post-analtail

Chick embryo Human embryo


Vestigial organs:

– remnants of structures that served important functions in the organism’s ancestors


Biochemical Comparisions:

• Particularly comparison of:

– DNA

– Proteins

Figure 22.16

Species

Human

Rhesus monkey

Mouse

Chicken

Frog

Lamprey14%

54%

69%

87%

95%

100%

Percent of Amino Acids That AreIdentical to the Amino Acids in aHuman Hemoglobin Polypeptide


Figure 22.18

• The Darwinian view of life

– Predicts that evolutionary transitions should leave signs in the

• fossil record

• Paleontologists have discovered fossils of many such transitional forms






The Evolution of Populations


The Modern Synthesis

• Population genetics…

– Merges & extends Darwin’s & Mendel’s ideas

– Focuses on populations as units of evolution


The Hardy-Weinberg Theorem

• The Hardy-Weinberg theorem describes a population that is not _________.

– evolving

– States that allele frequencies in a gene pool will remain constant from generation to generation, IF:

• only Mendelian segregation and recombination of alleles are at work

• no evolutionary forces are at work


• Five (rarely met) conditions for non-evolving populations…

– Extremely large population size

– No gene flow

– No mutations

– Random mating

– No natural selection


You reviewed these with the graphical Q’s, right?

Hardy-Weinberg Equations - If a population has only two possible alleles at a particular locus, & one is dominant, and no evolutionary forces are working:

• p + q = 1 (sum of allele frequencies = 1)

• p = frequency of the dominant allele in the population

• q = frequency of the recessive allele in the population

• p2 + 2pq + q2 = 1 (sum of genotype frequencies = 1)

• p2 = frequency of homozygous dominant individuals

• q2 = frequency of homozygous recessive individuals

• 2pq = frequency of heterozygous individuals


• Two processes produce variation in gene pools. What are they? Which one happens FIRST?

– 1st: Mutation creates allele variations.

– 2nd: Sexual recombination generates new allele combinations

via:

• crossing over during meiosis

• random segregation into gametes

• random recombination during fertilization


• Three major factors alter allele frequencies and bring about most evolutionary change

– Natural selection

– Genetic drift

– Gene flow


Directional, Disruptive, and Stabilizing Selection

• Selection can only act on an individual’s …

– phenotype

• This allows damaging recessive alleles to hide in ___________, and avoid elimination from the gene pool.


• The three modes of selection


Why does complex sexual reproduction persist?

– It produces genetic variation that may aid in…

• disease resistance

• better predator evasion

• better feeding efficiency

• survival in a changing environment


Why can’t evolution fashion perfect organisms?

– Mutations are RANDOM, not chosen

– Adaptations are often compromises

– Selection can only edit existing variations…

• gotta’ work with what we’ve got.

– “Perfect” is a moving target…

• Predators, prey & competitors keep changing






The Origin of Species


• Speciation

– is where microevolution of populations gives way to macroevolution

• Macroevolution

– Refers to evolutionary change that leads to whole new clades of creatures


Limitations of the Biological Species Concept

• The biological species concept cannot be applied to…?

– Asexual organisms

– Fossils

– Organisms with unknown reproductive cycles


• Prezygotic barriers … continued next slide…

Figure 24.4

Individualsof differentspecies

Matingattempt

Habitat isolation

Temporal isolation

Behavioral isolation

Mechanical isolation

HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION

(b)

(a)(c)

(d)

(e)

(f)

(g)

. . . . . . .


Viablefertile

offspring

Reducehybrid

viability

Reducehybridfertility

Hybridbreakdown

Fertilization

Gameticisolation

GAMETIC ISOLATION REDUCED HYBRID VIABILITY

REDUCED HYBRID FERTILITY HYBRID BREAKDOWN

(h) (i)

(j)

(k)

(l)

(m)

• ………………postzygotic barriers.


(a) Allopatric speciation. A population forms a new species while geographically isolated from its parent population.

(b) Sympatric speciation. A smallpopulation becomes a new specieswithout geographic separation.

• Speciation can occur in two ways

– Allopatric speciation

– Sympatric speciation


A. harrisi A. leucurus

• Allopatric or Sympatric?


Adaptive Radiation?


Evolutionary Novelties

• Most novel biological structures

– Evolve in many stages from previously existing structures


Hox Genes??

• Associated with the evolution of vertebrates


Most Species are?• Dead Ends!






Phylogeny and Systematics


Investigating the Tree of Life

• Phylogeny:

– The evolutionary history of a species or group of related species

• Phylogenies are constructed from three major types of evidence:

– fossil, morphological, and molecular


Linking Classification and Phylogeny

• Systematists depict evolutionary relationships in phylogenetic trees (cladograms)

Figure 25.9

Panthera pardus

(leopard)

Mephitis mephitis

(striped skunk)

Lutra lutra (European

otter)

Canis familiaris

(domestic dog)

Canislupus (wolf)

Panthera Mephitis Lutra Canis

Felidae Mustelidae Canidae

Carnivora

Ord

erF

amily

Gen

us

Sp

ecie

s


• “Deeper” branch points represent…

– progressively greater amounts of divergence

– longer times since divergence

Leopard Domestic cat

Common ancestor

Wolf


Monophyletic? Paraphyletic?

• A valid clade is monophyletic

– Signifying that it consists of the ancestor species and all its descendants

Figure 25.10a

Grouping 1

D

C

E G

F

B

A

J

I

KH


Outgroup? Derived Character? Cladogram?

• Cladograms help determine who branched off when.

• Presence or absence of derived characters determines how you build the cladogram.


Mutation rates vary for different types of genes.

• Which mutation pattern is best for comparing closely related species? Distantly related species?

mtDNA genes

rRNA genes


The Universal Tree of Life

• The tree of life is divided into three great clades called domains: Bacteria, Archaea, and Eukarya

• The early history of these domains is complex

Figure 25.18

Bacteria Eukarya Archaea4 Symbiosis of

chloroplast ancestor with ancestor of green plants

3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes

2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells

1 Last common ancestor of all living things

4

3

2

1

1

2

3

4

0

Bill

ion

ye

ars

ag

o

Origin of life

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