Module 1: Evolution

Month Day TopicSept 8 Mechanisms of evolution I

11 Mechanisms of evolution II

13 Speciation

15 Macroevolution and phylogenies

18 Biodiversity

20 The history of plants

22 Molecular evolution

25

27

Exam review

First mid-term exam

What controls the rate at which new species form?

What controls the rate at which new species form?

• Species richness

What controls the rate at which new species form?

• Species richness

• Range size and mobility

What controls the rate at which new species form?

• Species richness

• Range size and mobility

• Behavior, especially mate choice

What controls the rate at which new species form?

• Species richness

• Range size and mobility

• Behavior, especially mate choice

• Environmental change

What controls the rate at which new species form?

• Species richness

• Range size and mobility

• Behavior

• Environmental change

• Life history

What controls the rate at which new species form?

• Species richness

• Range size and mobility

• Behavior

• Environmental change

• Life history

• “Empty space”

Hawaiian silverswords

4th mass extinction 210 mya: ~65% of species5th mass extinction 65 mya: ~76% of speciesExtraterrestrial impact or volcanism?

What controls the rate at which new species form?

• Species richness

• Range size

• Behavior

• Environmental change

• Generation time

• “Empty space”

• Innovation

Proportional Changes in Skull

Chimpanzee

Human

Figure 19.14bPage 315

MicroevolutionChange in the frequencies of genotypes

in a population

The formation of new species

Macroevolution

Classifying the diversity of life

Systematics

Classifying the diversity of life

Systematics

Taxonomy Phylogenetics

Bluebells…

Taxonomy

• Linnaeus (1700s)– System of classification based on

morphological similarity

Taxonomy

• Linnaeus (1700s)– System of classification based on

morphological similarity

– Binomial nomenclature

Taxonomy

• Linnaeus (1700s)– System of classification based on

morphological similarity

– Binomial nomenclature

– Hierarchical classification

Binomial nomenclature

Homo

Genus Species

sapiensCapitalize

Italicize or underline

Hierarchical classification

Kingdom:

Phylum:

Class:

Order:

Family:

Genus:

Species:

Hierarchical classification

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primates

Family: Hominidae

Genus: Homo

Species: H. sapiens

Hierarchical classification

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Diptera

Family: Muscidae

Genus: Musca

Species: M. domestica

Hierarchical classification

Kingdom: Plantae

Phylum: Anthophyta

Class: Monocotyledonae

Order: Poales

Family: Poaceae

Genus: Zea

Species: Z. mays

Hierarchical classification

Kingdom: Plantae

Phylum: Anthophyta

Class: Monocotyledonae

Order: Asparagales

Family: Orchidaceae

Genus: Vanilla

Species: V. planifolia

Phylogenetics

Classification of organisms according to their evolutionary relationships

Phylogenetics

Classification of organisms according to their evolutionary relationships

A phylogeny is the history of decent of a group of organisms from their common

ancestor

Ancestor

Sp. 1 Sp. 2 Sp. 3

Ancestor

Sp. 1 Sp. 2 Sp. 3

Ancestor

Sp. 1 Sp. 2 Sp. 3

Derived traits

Ancestral trait

Ancestor

Sp. 1 Sp. 2 Sp. 3

Tail stub

SHARED CHARACTER

Ancestor

Sp. 1 Sp. 2 Sp. 3

Tail stub

Tail motor control

SHARED DERIVED CHARACTER

Ancestor

Sp. 1 Sp. 2 Sp. 3

Prehensile control

Tail stub appears

Tail motor control

DERIVED CHARACTER

Jaws Limbs Hair Lungs Tail Shell

0 0 0 0 0 0

1 1 0 1 0 1

1 1 1 1 0 0

1 1 1 1 1 0

1 0 0 1 0 0

1 0 0 0 0 0

1 1 1 1 1 0

Lamprey

Turtle

Cat

Gorilla

Lungfish

Trout

Human

Taxon Traits (Characters)

Homologs

Features that have descended from a common ancestral feature

Homologs

Features that have descended from a common ancestral feature

Use homology to determine phylogenetic relationships

Homologs

Traits can be…

Morphological

Developmental

Behavioral

Molecular

Homologous features

Difficulty

Traits change with evolution

More difficulties…

• Convergent evolution

More difficulties…

• Convergent evolution– Similar environments shape features that

have different ancestral origins to look very much alike

Arm bones are homologousBUT wings are the result ofconvergent evolution

Cactus and euphorbs

More difficulties…

• Parallel evolution

More difficulties…

• Parallel evolution– Similar developmental processes may

make traits in distantly related organisms look similar, even though those traits did not come from a shared ancestor

More difficulties…

• Evolutionary reversals

More difficulties…

• Evolutionary reversals– A derived trait may revert back to its

ancestral state

Ancestor—Toothy frog

Sp. 1 Sp. 2 Sp. 3

Loss of teeth

Teeth regained

More difficulties…

• Convergent evolution

• Parallel evolution

• Evolutionary reversals

Traits that are similar due to these processes are called

homoplastic traits

Homologous trait

versus

Homoplastic trait

Same because of descent from common ancestor

Same because shaped by similar environments

Homologous trait

versus

Homoplastic trait

Used to build phylogenetic relationships

Not used to build phylogenetic relationships

Principle of parsimony

Choose the simplest hypothesis capable of explaining the pattern.

Principle of parsimony

Choose the simplest hypothesis capable of explaining the pattern.

Descent from a common ancestor is much simpler than invoking

homoplasies.

Principle of parsimony

…think of it as the path of least resistance

It is “easier” to inherit a trait than to build a new one.

Principle of parsimony

The null hypothesis: this trait was inherited from a common ancestor

The alternative hypothesis: this trait was built by natural selection

Modern taxonomy

Modern taxonomy

Biological species

Versus

“taxonomic” species

Modern taxonomy

• Taxonomic groups should reflect evolutionary relationships

Modern taxonomy

• Taxonomic groups should reflect evolutionary relationships

• Taxonomic groups should be monophyletic– They should contain all the descendents of

a particular ancestor, and no others

Monophyletic

Evolutionary Tree

extreme

thermophiles

halophilesmethanogens cyanobacteria

ARCHAEBACTERIA

PROTISTANS

FUNGIPLANTS

ANIMALS

clubfungi

sacfungi

zygospore-forming

fungi

echino-derms

chordatesannelids

mollusks

flatworms

sponges

cnidarians

flowering plants conifers

horsetails

lycophytes

ferns

bryophytes

sporozoans

green algae amoeboidprotozoans

slime molds

ciliatesredalgae

brown algaechrysophytes

cycads

ginkgos

rotifers

arthropodsround-worms

chytrids

oomycotes

euglenoids

dinoflagellates

Gram-positive bacteria

spirochetes

chlamydias

proteobacteria

? crown of eukaryotes

(rapid divergences)

molecular origin of life

EUBACTERIAparabasalids

diplomonads(e.g., Giardia)

(alveolates)

(stramenopiles)

chlorophytes

kinetoplastids

extreme

(e.g., Trichomonas)

Figure 19.21Page 321

Five Kingdoms

Bacteria Protists Plants Fungi Animals

Earliest organisms

Three domains

Bacteria

Earliest organisms

Archaea Eukarya