What we covered this week
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What we covered this week. With shortened chs 25 and 26. Fig. 24-10-3. 2 n. 2 n = 6. 4 n = 12. 4 n. Failure of cell division after chromosome duplication gives rise to tetraploid tissue. Gametes produced are diploid. Offspring with tetraploid karyotypes may be viable and

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What we covered this week

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What we covered this week

What we covered this week

With shortened chs 25 and 26


What we covered this week

Fig. 24-10-3

2n

2n = 6

4n = 12

4n

Failure of cell

division after

chromosome

duplication gives

rise to tetraploid

tissue.

Gametes

produced

are diploid..

Offspring with

tetraploid

karyotypes may

be viable and

fertile.


What we covered this week

Fig. 24-11-4

Species B

2n = 4

Unreduced

gamete

with 4

chromosomes

Unreduced

gamete

with 7

chromosomes

Hybrid

with 7

chromosomes

Meiotic

error

Viable fertile

hybrid

(allopolyploid)

2n = 10

Normal

gamete

n = 3

Normal

gamete

n = 3

Species A

2n = 6

  • Polyploidy is much more common in plants than in animals

  • Many important crops (oats, cotton, potatoes, tobacco, and wheat) are polyploids


What we covered this week

Fig. 24-12

Sexual selection can drive sympatric speciation

EXPERIMENT

Monochromatic

orange light

Normal light

P.

pundamilia

P. nyererei


Concept 24 3 hybrid zones provide opportunities to study factors that cause reproductive isolation

Concept 24.3: Hybrid zones provide opportunities to study factors that cause reproductive isolation


What we covered this week

Fig. 24-13

A hybrid zone is a region in which members of different species mate and produce hybrids

EUROPE

Fire-bellied

toad range

Hybrid zone

Fire-bellied toad,

Bombina bombina

Yellow-bellied

toad range

Yellow-bellied toad,

Bombina variegata

0.99

0.9

Allele frequency (log scale)

0.5

0.1

0.01

20

40

30

10

0

10

20

Distance from hybrid zone center (km)


Hybrid zones over time

Hybrid Zones over Time

  • When closely related species meet in a hybrid zone, there are three possible outcomes:

    • Strengthening of reproductive barriers

    • Weakening of reproductive barriers

    • Continued formation of hybrid individuals


What we covered this week

Fig. 24-14-4

Isolated population

diverges

Possible

outcomes:

Hybrid

zone

Reinforcement

OR

Fusion

Gene flow

Hybrid

OR

Barrier to

gene flow

Population

(five individuals

are shown)

Stability


Patterns in the fossil record

Patterns in the Fossil Record

  • The fossil record includes examples of species that appear suddenly, persist essentially unchanged for some time, and then apparently disappear

  • Niles Eldredge and Stephen Jay Gould coined the term punctuated equilibrium to describe periods of apparent stasis punctuated by sudden change

  • The punctuated equilibrium model contrasts with a model of gradual change in a species’ existence


What we covered this week

Fig. 24-17

(a) Punctuated pattern

Time

(b) Gradual pattern


Speciation rates

Speciation Rates

  • The punctuated pattern in the fossil record and evidence from lab studies suggests that speciation can be rapid

  • The interval between speciation events can range from 4,000 years (some cichlids) to 40,000,000 years (some beetles), with an average of 6,500,000 years


What we covered this week

Fig. 24-18

(a) The wild sunflower Helianthus anomalus

H. anomalus

Chromosome 1

Experimental hybrid

H. anomalus

Chromosome 2

Experimental hybrid

H. anomalus

Chromosome 3

Experimental hybrid

Key

Region diagnostic for

parent species H. annuus

Region diagnostic for

parent species H. petiolaris

Region lacking information on parental origin

(b) The genetic composition of three chromosomes in H.

anomalus and in experimental hybrids


Studying the genetics of speciation

Studying the Genetics of Speciation

  • The explosion of genomics is enabling researchers to identify specific genes involved in some cases of speciation

  • Depending on the species in question, speciation might require the change of only a single allele or many alleles


What we covered this week

Fig. 24-19


What we covered this week

Fig. 24-20

(a) Typical Mimulus lewisii

(b) M. lewisii with an M. cardinalis flower-color allele

(c) Typical Mimulus cardinalis

(d) M. cardinalis with an M. lewisii flower-color allele


What we covered this week

Fig. 24-UN1

Original population

Macroevolution is the cumulative effect of many speciation and extinction events

Allopatric speciation

Sympatric speciation


What we covered this week

Fig. 24-UN2

Ancestral species:

AA

BB

DD

Wild

T. tauschii

(2n = 14)

Triticum

monococcum

(2n = 14)

Wild

Triticum

(2n = 14)

Product:

AA BB DD

T. aestivum

(bread wheat)

(2n = 42)


Chapter 25

Chapter 25

The History of Life on Earth


Overview lost worlds

Overview: Lost Worlds

  • Past organisms were very different from those now alive

  • The fossil record shows macroevolutionary changes over large time scales including

    • The emergence of terrestrial vertebrates

    • The origin of photosynthesis

    • Long-term impacts of mass extinctions


What we covered this week

Fig. 25-1


Concept 25 1 conditions on early earth made the origin of life possible

Concept 25.1: Conditions on early Earth made the origin of life possible

  • Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages:

    1. Abiotic synthesis of small organic molecules

    2. Joining of these small molecules into macromolecules

    3. Packaging of molecules into “protobionts”

    4. Origin of self-replicating molecules


Synthesis of organic compounds on early earth

Synthesis of Organic Compounds on Early Earth

  • Earth formed about 4.6 billion years ago, along with the rest of the solar system

  • Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide)


What we covered this week

  • A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing environment (add e- or H to cmpds)

  • Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible

  • Reduction could also have happened in water.


Miller s experiment

Miller’s Experiment

http://www.cbs.dtu.dk/staff/dave/roanoke/stanley_miller_3d.gif


What we covered this week

Fig. 25-3

Protobionts

20 µm

Glucose-phosphate

Glucose-phosphate

Phosphatase

Starch

Amylase

Phosphate

Maltose

(a) Simple reproduction by

liposomes

Maltose

(b) Simple metabolism


Self replicating rna and the dawn of natural selection

Self-Replicating RNA and the Dawn of Natural Selection

  • The first genetic material was probably RNA, not DNA

  • RNA molecules called ribozymes have been found to catalyze many different reactions

    • For example, ribozymes can make complementary copies of short stretches of their own sequence or other short pieces of RNA


What we covered this week

Table 25-1


What we covered this week

The classical "Big Five" mass extinctions identified by Jack Sepkoski and David M. Raup in their 1982 paper are widely agreed upon as some of the most significant: End Ordovician, Late Devonian, End Permian, End Triassic, and End Cretaceous.[2][3]


What we covered this week

Fig. 25-9-4

Cytoplasm

Plasma membrane

DNA

Ancestral

prokaryote

Endoplasmic reticulum

Nucleus

Nuclear envelope

Aerobic

heterotrophic

prokaryote

Photosynthetic

prokaryote

Mitochondrion

Mitochondrion

Ancestral

heterotrophic

eukaryote

Plastid

Ancestral photosynthetic

eukaryote


The earliest multicellular eukaryotes

The Earliest Multicellular Eukaryotes

  • Comparisons of DNA sequences date the common ancestor of multicellular eukaryotes to 1.5 billion years ago

  • The oldest known fossils of multicellular eukaryotes are of small algae that lived about 1.2 billion years ago

  • What is the advantage of being multicellular?


The colonization of land

The Colonization of Land

  • Fungi, plants, and animals began to colonize land about 500 million years ago

  • Plants and fungi likely colonized land together by 420 million years ago

  • Arthropods and tetrapods are the most widespread and diverse land animals

  • Tetrapods evolved from lobe-finned fishes around 365 million years ago


What we covered this week

Fig. 25-12b

North

American

Plate

Eurasian Plate

Caribbean

Plate

Philippine

Plate

Juan de Fuca

Plate

Arabian

Plate

Indian

Plate

Cocos Plate

South

American

Plate

Pacific

Plate

Nazca

Plate

African

Plate

Australian

Plate

Antarctic

Plate

Scotia Plate

How might continental drift influence biota on a ecosystem level?


What we covered this week

  • The break-up of Pangaea lead to allopatric speciation

  • The current distribution of fossils reflects the movement of continental drift

  • For example, the similarity of fossils in parts of South America and Africa is consistent with the idea that these continents were formerly attached


What we covered this week

Fig. 25-14

800

20

700

600

15

500

Number of families:

400

Total extinction rate

(families per million years):

10

300

200

5

100

0

0

Mesozoic

Paleozoic

Cenozoic

Era

Period

E

C

Tr

C

O

S

D

P

J

P

N

200

145

65.5

0

542

488

444

416

359

299

251

Time (millions of years ago)


What we covered this week

  • The Permian extinction defines the boundary between the Paleozoic and Mesozoic eras

  • This mass extinction occurred in less than 5 million years and caused the extinction of about 96% of marine animal species

  • This event might have been caused by volcanism, which lead to global warming, and a decrease in oceanic oxygen


What we covered this week

  • The Cretaceous mass extinction 65.5 million years ago separates the Mesozoic from the Cenozoic

  • Organisms that went extinct include about half of all marine species and many terrestrial plants and animals, including most dinosaurs


What we covered this week

Fig. 25-15

NORTH

AMERICA

Chicxulub

crater

Yucatán

Peninsula


Is a sixth mass extinction under way

Is a Sixth Mass Extinction Under Way?

  • Scientists estimate that the current rate of extinction is 100 to 1,000 times the typical background rate

  • Data suggest that a sixth human-caused mass extinction is likely to occur unless dramatic action is taken


Adaptive radiations

Adaptive Radiations

  • Adaptive radiation is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities


Worldwide adaptive radiations

Worldwide Adaptive Radiations

  • Mammals underwent an adaptive radiation after the extinction of terrestrial dinosaurs

  • The disappearance of dinosaurs (except birds) allowed for the expansion of mammals in diversity and size

  • Other notable radiations include photosynthetic prokaryotes, large predators in the Cambrian, land plants, insects, and tetrapods


What we covered this week

Fig. 25-17

Ancestral

mammal

Monotremes

(5 species)

ANCESTRAL

CYNODONT

Marsupials

(324 species)

Eutherians

(placental

mammals;

5,010 species)

50

200

250

100

150

0

Millions of years ago


Evolutionary effects of development genes

Evolutionary Effects of Development Genes

  • Genes that program development control the rate, timing, and spatial pattern of changes in an organism’s form as it develops into an adult

Fig. 25-21


Chapter 26

Chapter 26

Phylogeny and the Tree of Life


Overview investigating the tree of life

Overview: Investigating the Tree of Life

  • Phylogeny is the evolutionary history of a species or group of related species

  • The discipline of systematicsclassifies organisms and determines their evolutionary relationships

  • Systematists use fossil, molecular, and genetic data to infer evolutionary relationships

  • Taxonomyis the ordered division and naming of organisms


What we covered this week

Fig. 26-3

Species:

Panthera

pardus

Genus: Panthera

Family: Felidae

Order: Carnivora

Class: Mammalia

Phylum: Chordata

Kingdom: Animalia

Domain: Eukarya

Archaea

Bacteria


What we covered this week

Fig. 26-4

Species

Order

Family

Genus

Pantherapardus

Panthera

Felidae

Taxidea

taxus

Taxidea

Carnivora

Mustelidae

phylogenetic trees

Lutra lutra

Lutra

Canis

latrans

Canidae

Canis

Canis

lupus


What we covered this week

  • A phylogenetic tree represents a hypothesis about evolutionary relationships

  • Each branch point represents the divergence of two species

  • Sister taxa are groups that share an immediate common ancestor


What we covered this week

Fig. 26-5

Branch point

(node)

Taxon A

Taxon B

Sister

taxa

Taxon C

ANCESTRAL

LINEAGE

Taxon D

Taxon E

Taxon F

Common ancestor of

taxa A–F (root)

Polytomy


What we can and cannot learn from phylogenetic trees

What We Can and Cannot Learn from Phylogenetic Trees

  • Phylogenetic trees do show patterns of descent

  • Phylogenetic trees do not indicate when species evolved or how much genetic change occurred in a lineage

  • It shouldn’t be assumed that a taxon evolved from the taxon next to it


Concept 26 2 phylogenies are inferred from morphological and molecular data

Concept 26.2: Phylogenies are inferred from morphological and molecular data

  • To infer phylogenies, systematists gather information about morphologies, genes, and biochemistry of living organisms


Morphological and molecular homologies

Morphological and Molecular Homologies

  • Organisms with similar morphologies or DNA sequences are likely to be more closely related than organisms with different structures or sequences


Sorting homology from analogy

Sorting Homology from Analogy

  • When constructing a phylogeny, systematists need to distinguish whether a similarity is the result of homology or analogy

  • Homology is similarity due to shared ancestry

  • Analogy is similarity due to convergent evolution


What we covered this week

Fig. 26-10

polyphyleticgrouping consists of various species that lack a common ancestor

monophyleticconsists of the ancestor species and all its descendants

A

A

A

Group I

B

B

B

C

C

C

D

D

D

Group III

Group II

E

E

E

F

F

F

G

G

G

(b) Paraphyletic group

(c) Polyphyletic group

(a) Monophyletic group (clade)

paraphyleticgrouping consists of an ancestral species and some, but not all, of the descendants


What we covered this week

Fig. 26-11

TAXA

Lancelet

(outgroup)

Lancelet

(outgroup)

Salamander

Lamprey

Lamprey

Leopard

Turtle

Tuna

Tuna

Vertebral column

(backbone)

1

1

1

1

1

0

Vertebral

column

Hinged jaws

1

1

1

1

0

0

Salamander

Hinged jaws

CHARACTERS

1

0

0

0

1

1

Four walking legs

Turtle

Four walking legs

1

1

0

0

0

0

Amniotic (shelled) egg

Amniotic egg

Leopard

0

1

0

0

0

0

Hair

Hair

(b) Phylogenetic tree

(a) Character table


Maximum parsimony and maximum likelihood

Fig. 26-14

Mushroom

Human

Tulip

Maximum Parsimony and Maximum Likelihood

40%

0

30%

Human

40%

0

Mushroom

0

Tulip

(a) Percentage differences between sequences

5%

15%

5%

15%

15%

10%

25%

20%

Tree 1: More likely

Tree 2: Less likely

(b) Comparison of possible trees


Concept 26 4 an organism s evolutionary history is documented in its genome

Concept 26.4: An organism’s evolutionary history is documented in its genome

  • Comparing nucleic acids or other molecules to infer relatedness is a valuable tool for tracing organisms’ evolutionary history

  • DNA that codes for rRNA changes relatively slowly and is useful for investigating branching points hundreds of millions of years ago

  • mtDNA evolves rapidly and can be used to explore recent evolutionary events


Molecular clocks

Molecular Clocks

  • A molecular clock uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change

  • Molecular clocks are calibrated against branches whose dates are known from the fossil record


Applying a molecular clock the origin of hiv

Applying a Molecular Clock: The Origin of HIV

  • Phylogenetic analysis shows that HIV is descended from viruses that infect chimpanzees and other primates

  • Comparison of HIV samples throughout the epidemic shows that the virus evolved in a very clocklike way

  • Application of a molecular clock to one strain of HIV suggests that that strain spread to humans during the 1930s


What we covered this week

Fig. 26-20

0.20

0.15

Computer model

of HIV

Index of base changes between HIV sequences

0.10

Range

0.05

0

1900

1920

1940

1960

1980

2000

Year


What we covered this week

Fig. 26-21

EUKARYA

Dinoflagellates

Land plants

Forams

Green algae

Ciliates

Diatoms

Red algae

Amoebas

Cellular slime molds

Euglena

Trypanosomes

Animals

Leishmania

Fungi

Sulfolobus

Green nonsulfur bacteria

Thermophiles

(Mitochondrion)

Spirochetes

Chlamydia

Halophiles

COMMON

ANCESTOR

OF ALL

LIFE

Green

sulfur bacteria

BACTERIA

Methanobacterium

Cyanobacteria

(Plastids, including

chloroplasts)

ARCHAEA


What we covered this week

Fig. 26-22

Horizontal genetransfer

Bacteria

Eukarya

Archaea

4

3

2

1

0

Billions of years ago


What we covered this week

Is the Tree of Life Really a Ring?

  • Some researchers suggest that eukaryotes arose as an endosymbiosis between a bacterium and archaean

  • If so, early evolutionary relationships might be better depicted by a ring of life instead of a tree of life


What we covered this week

Fig. 26-23

Eukarya

Bacteria

Archaea


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