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L. O. U. V. T. E. I. O. N. Fig. 16-4b, p.239. EVOLUTION = change over time which is inherited. Macroevolution: major changes of life on earth since its formation 4.6 billion years ago from fossils to present-day species 2. Microevolution:

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slide1

L

O

U

V

T

E

I

O

N

Fig. 16-4b, p.239

slide2

EVOLUTION

= change over time

which is inherited

  • Macroevolution:
  • major changes of life on earth since its formation 4.6 billion years ago
  • from fossils to present-day species
  • 2. Microevolution:
  • small scale changes in allele frequencies in the gene pool of a population
  • from mutations to speciation events
slide3

Speciation

Definition (Ernst Mayr): Species are groups of interbreeding natural populations (which produce fertile offspring) that are reproductively isolated from other such groups.

Many/large microevolutionary steps

 new species

Reproductive isolation

Gene flow between populations stops = gene pools stay separate

Genetic divergence (change)

of structural, function, or behavioral traits

Reproductive isolation: populations are not longer reproductively compatible = a new species has originated

slide4

How is gene flow stopped?

  • Separation by a physical barrier (created by glaciation, earth quakes, volcanic activity, formation of mountains, land bridges = allopatric speciation
  • Ecological separation without physical barriers (different food, mating areas) = sympatric speciation
slide5

How is gene flow stopped?

  • Separation by a physical barrier (created by glaciation, earth quakes, volcanic activity, formation of mountains, land bridges = allopatric speciation

North American Prairie

camelid ancestor

landbridges

camels

Asia, Africa

Ilama

South America

vicuna

South America

stepped art
Stepped Art

1

A few individuals of a species on the mainland reach isolated island 1. Speciation follows genetic divergence in a new habitat.

3

2

4

Later in time, a few individuals of the new species colonize nearby island 2. In this new habitat, speciation follows genetic divergence.

1

2

Speciation may also follow colonization of islands 3 and 4. And it may follow invasion of island by genetically different descendants

of the ancestral species.

1

3

2

4

How is gene flow stopped?

  • Separation by a physical barrier (created by glaciation, earth quakes, volcanic activity, formation of mountains, land bridges = allopatric speciation

New islands created by volcanic activity.

Fig. 17-20a, p.275

slide8

How is gene flow stopped?

2. Ecological separation without physical barriers (different food, mating areas) = sympatric speciation

Cichlids in Africa live on different food sources  many species in one lake.

Fig. 17-21a, p.276

slide9

Speciation

Definition (Ernst Mayr): Species are groups of interbreeding natural populations (which produce fertile offspring) that are reproductively isolated from other such groups.

Many/large microevolutionary steps

 new species

Reproductive isolation

Gene flow between populations stops = gene pools stay separate

Genetic divergence (change)

of structural, function, or behavioral traits

Reproductive isolation: populations are not longer reproductively compatible = a new species has originated

slide11

Naming species - taxonomy

  • Scientific name:
  • Latin
  • Binomial (2 parts: generic name + species epithet

Ursus arctos – brown bear

Ursus americanus – black bear

common name

genus

species

slide12

Ranking species - classification

Ursus arctos – brown bear

Ursus americanus – black bear

Fig. 17-27, p.280

slide16

Evolutionary Tree of Life

The three domain system:

Webpage:

http://tolweb.org/tree/phylogeny.html

p.259c

slide17

Evolutionary Tree of Life

ANIMALS

PLANTS

arthropods

chordates

FUNGI

flowering plants

conifers

annelids

roundworms

club

fungi

echinoderms

sac

fungi

ginkgos

mollusks

cycads

horsetails

rotifers

zygospore-

forming

fungi

ferns

flatworms

cnidarians

lycophytes

bryophytes

chytrids

charophytes

sponges

chlorophytes

amoeboid

protozoans

PROTISTS

choanoflagellates

(stramenopiles)

brown algae

alveolates

red algae

ciliates

chrysophytes

apicomplexans

oomycotes

dinoflagellates

“crown” of eukaryotes

(rapid divergences)

euglenoids

slime molds

kinetoplatids

Parabasalids

(e.g., Trichomonas)

ARCHAEA

BACTERIA

spirochetes

diplomonads

crenarchaeotes

euryarchaeotes

Gram-positive bacteria

chlamydias

cyanobacteria

korarchaeotes

Webpage:

http://tolweb.org/tree/phylogeny.html

slide18

Phylogenetic trees illustrate the relationship between species.

  • What type of evidence/support is used to build a tree?
  • Biochemical evidence
  • Fossil evidence
  • Morphological evidence
  • Developmental evidence

Fig. 17-15, p.271

slide19

1. Biochemical evidence:

DNA, protein, or metabolite analysis

DNA example

ATGCGCCTTAGCA polar bear

TTGCGCCTAAGCA brown bear

GTCGGCCTAATCT black bear

protein example (cytochrome c needed for respiration):

conserved areas between Yeast/wheat/primate

Fig. 17-14b, p.271

slide20

1. Biochemical evidence:

DNA, protein, or metabolite analysis

Molecular clock:

Time scale of biochemical analysis: when have species diverged from each other?

Assumption: neutral mutations happen at a constant rate

slide21

2. Fossil evidence:

  • Evidence of ancestral species
  • Evidence for a time scale:
  • the deepest layer in the ground contains the oldest fossils
  • radiometric dating

p.259b

slide23

Radiometric Dating

Uranium (in rocks) → Lead: the earth is at least 4.6 billion years old

after one half-life

after two half-lives

a A simple way to think about the decay of a radioisotope to a

more stable form, as plotted against time.

Fig. 17-4a, p.262

slide24

Radiometric Dating

b Long ago, trace amounts of 14C and a lot more 12C were incorporated into tissues of a living mollusk. The carbon was part of the organic compounds making up the tissues of its prey. As long as it lived, the proportion of 14C to 12C in its tissues remained the same.

Fig. 17-4b, p.262

slide25

Radiometric Dating

c When the mollusk died, it stopped gaining carbon. Over time, proportion of 14C to 12C in its remains declined because of the radioactive decay of 14C. Half of the 14C had decayed in 5,370 years, half of what remained was gone in another 5,370 years, and so on.

Fig. 17-4c, p.262

slide26

Radiometric Dating

dFossil hunters find the fossil. They measure its 14C/12C ratio to determine the half-life reductions since death. The ratio turns out to be one-eighth of the 14C/12C ratio in living organisms. Thus the mollusk lived about 16,000 years ago.

Fig. 17-4d, p.262

slide27

Midnight, origin of life

11:59:40 PM, first humans

origin of prokaryotes

dinosuars, flowering plants

origin of eukaryotes

Fig. 17-6, p.263

slide29

Location of fossil records needs to be interpreted in the context of the plate tectonic theory: continents are drifting

island arc

oceanic crust

oceanic ridge

trench

continental crust

lithosphere

(solid layer of mantle)

hot spot

athenosphere

(plastic layer of mantle)

subducting plate

Fig. 17-7b, p.264

slide30

Location of fossil records needs to be interpreted in the context of the plate tectonic theory: continents are drifting

a 420 mya

b 260 mya

c 65 mya

d 10 mya

PANGEA supercontinent

Fig. 17-8a, p.265

slide31

NORTH AMERICAN PLATE

EURASIAN PLATE

PACIFIC PLATE

PHILIPPINE PLATE

COCOS

PLATE

SOMALI PLATE

SOUTH AMERICAN PLATE

NAZCA

PLATE

INDO-

AUSTRALIAN PLATE

AFRICAN PLATE

ANTARCTIC PLATE

Fig. 17-7a, p.264

slide33

3. Morphological evidence:

HOMOLOGIES give useful information about relationship:

Homology = similar structure (bone, muscle, nerve, …) inherited from a common ancestor

ANALOGIES should not be used to infer relationship:

Analogy = structure that seems to be similar but has not been inherited from a common ancestor

Fig. 17-9a, p.266

slide34

Homology = similar structure (bone, muscle, nerve, …) inherited from a common ancestor

Example: comparison of

forelimbs

Fig. 17-9, p.266

slide35

Analogy = structure that seems to be similar but has not been inherited from a common ancestor

Example: comparison of

wings

skin

extension of exoskeleton (chitin)

feathers

Fig. 17-10a, p.267

slide36

body wall (exoskeleton)

strong membrane (extension of wall)

wing veins

Fig. 17-10d, p.267

slide37

4. Developmental evidence:

Similarities may be obvious only during the early stages of development, not in the adult individual:

chimpanzee skull

proportions in infant

adult

human skull

Fig. 17-12a, p.268