Evolution Genetic change in a lineage over time first convincing case put forth by –Charles Darwin

Evolution

• Genetic change in a lineage over time

• first convincing case put forth by – Charles Darwin

Artificial Selection in Agriculture

Agriculture

Corn looks very different from its ancestor

Artificial Selection

Artificial Selection

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fig. 21.5-1 SCIENTIFIC THINKING

Question: Can artificial selection lead to substantial evolutionarychange?


SCIENTIFIC THINKING


Hypothesis: Strong directional selection will quickly lead to a largeshift in the mean value of the population.

Experiment: In one population, every generation pick out the 20% ofthe population with the most bristles and allow them to reproduce toform the next generation. In the other population, do the same withthe 20% with the fewest number of bristles.


Bristle number in Drosophila

Nu

mb

er

of

Ind

ivid

ua

ls

0 10 20 30 40 50 60 70 80 90 100 110

SCIENTIFIC THINKING


Result: After 35 generations, mean number of bristles has changed

substantially in both populations.

Lowpopulation

Initialpopulation

Me

an

Me

an

Me

an

Highpopulation




Bristle number in Drosophila

Nu

mb

er

of

Ind

ivid

ua

ls

0 10 20 30 40 50 60 70 80 90 100 110

SCIENTIFIC THINKING


Result: After 35 generations, mean number of bristles has changed

substantially in both populations.

Lowpopulation

Initialpopulation

Me

an

Me

an

Me

an

Highpopulation



Interpretation: Note that at the end of the experiment, the range of

variation lies outside the range seen in the initial population.

Selection can move a population beyond its original range because

mutation and recombination continuously introduce new variation

into populations.

Darwin’s finches

Evidence of Natural Selection

Peter and Rosemary Grant studied medium ground finch

Evidence of Natural Selection

Natural Selection

Figure 21.4Selection against melanism.The red circles indicate the frequency of melanic Biston betularia moths at Caldy Common in Great Britain. Green diamonds indicate frequencies of melanic B. betularia in Michigan, and the blue squares indicate corresponding frequencies in Pennsylvania.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 22.12

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• For patients treated with the drug 3TC, which interferes with genome replication in HIV, 3TC-resistant strains become 100%

of the population of HIV in just a few weeks.

Fig. 22.13

Evolution of Super bugs: MRSA, or methicillin-resistant Staphylococcus aureus.Multi-drug resistant tuberculosis; Clostridium difficile, etc

Whale “missing links”

Fossil Evidence of Evolution

• Vestigial structures: have no apparent function, but resemble structures their ancestors possessed

Anatomical Evidence for Evolution

Vestigial structures of a whale

• Humans– Muscles for wiggling ears

• Boa constrictors– Hip bones and rudimentary hind legs

• Manatees– Fingernails on their fins

• Blind cave fish– Nonfunctional eyes


Homology of the bones of the forelimb of mammals


Convergent evolution of fast swimming predators


Developmental similarities reflect descent from a common ancestor


Evolution

• A unifying theme in Biology

• Explains the diversity and unity we observe

Charles Darwin

• Naturalist on

HMS Beagle in 1831

• Galapagos Islands

• the origin of new

species

Origin of Species, 1859

• Two main points– 1. Evolution explains the unity and diversity of

life• “descent with modification”

– 2. Natural selection was the main cause of evolution

• differential reproductive success leads to adaptation

Evolution

• Individuals do not evolve

• Populations are the smallest units that can evolve– a group of interbreeding individuals belonging

to a particular species sharing a common geographic area

• Discussed “microevolution” in BIO 150

Origin of New Species

• Biological species concept– a population or group whose members have the

potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot successfully interbreed with other such groups

– does not work for everything• asexual, extinct, geographically separated???

• Species are based on interfertility, not physical similarity.

• For example, the eastern and western meadowlarks may have similar shapes and coloration, but differences in song help prevent interbreeding between the two species.

• In contrast, humans haveconsiderable diversity,but we all belong to thesame species because ofour capacity to interbreed.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 24.2

Speciation

• Evolution of reproductive barriers– the key biological event in the origin of new

species– any factor that impedes two species from

producing fertile hybrids, thus contributing to reproductive isolation

– prezygotic and postzygotic

Tab. 22.1

Tab. 22.1.contd.

https://www.youtube.com/watch?v=z922by9_6Fw

https://www.youtube.com/watch?v=z922by9_6Fw

Later found Prezygotic isolation- different songshttps://www.youtube.com/watch?v=kUdeEw2BPsQ

Types or Modes of Speciation

Fig 24.6

Types of Speciation

• Allopatric speciation– speciation event in which the initial block to

gene flow is a geographic barrier that physically isolates the populations

Reasons for Geographic Isolation

Example of Allopatric speciation

Fig 24.7

Fig. 22.16Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

a.

b.

Glaciation

snowfield snowline fringe stony debris sheltered boggy

Mountain populations become isolated,permitting divergence and speciation.

Alpine zones are reconnected. Separatelyevolved species come back into contact.

Glaciers link alpine zones into onecontinuous range.

Glaciersrecede

a(1): © Photo New Zealand/Hedgehog House; a(2): © Jim Harding/First Light; a(3): © Colin Harris/Light Touch Images/Alamy; a(4)-(5): © Focus New Zealand Photo Library.

Periodic Isolation in Alpine Buttercup

• The key to allopatric speciation is whether the separated populations have become different enough that they can no longer interbreed and produce fertile offspring when they come back in contact.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 24.8

Types of Speciation

• Sympatric speciation– formation of new species within the range of

the parental population– Much less common– Polyploidy– Or disruptive selection

Polyploidy and Sympatric Speciation

What Causes Reproductive Isolation to Evolve?

• Selection– May cause the initial isolation if populations

are adapting to different environments– May lead to reinforcement of isolating

mechanisms

• Random changes

Reinforcement in European Flycatchers

Piedflycatcher

Piedflycatcher

Collaredflycatcher

Collaredflycatcher

Macroevolution

• Origin of taxonomic groups higher than the species level

• evolutionary change substantial enough to view its products as new genera, families or phyla

• Has a random component

Macroevolution

• The study of– major evolutionary innovations

• bird feathers, insect wings

Macroevolution

• The study of– evolutionary trends

Fig. 21.13Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.H

yrac

othe

rium

Oro

hipp

us

Epi

hipp

us Mes

ohip

pus

Anc

hith

eriu

m

Mio

hipp

us

Meg

ahip

pus

Hyp

ohip

pus

Eocene

Oligocene

Miocene

browsersgrazersmixed feeders

Kal

obat

ippu

s

Arc

haeo

hipp

us

Des

mat

ippu

s

Par

ahip

pus

Mer

ychi

ppus

Pse

udhi

ppar

ion

Neo

hipp

ario

n

Hip

pario

n

Nan

nipp

us

Cor

moh

ippa

rion

Pro

tohi

ppus

Cal

ippu

s

Plio

hipp

us

Ast

rohi

ppus

Ono

hipp

idio

n

Din

ohip

pus

Equ

us

Merychippus(mixed feeders)

Neohipparion(grazers)

Nannippus(grazers)

Equus(grazers)

Anchitherium(browsers)

Hyracotherium(browsers)

Mesohippus(browsers)

Pleistocene

5MYA

10MYA

15MYA

20MYA

25MYA

30MYA

35MYA

40MYA

45MYA

50MYA

55MYA

60MYA

Pliocene

Macroevolution

• The study of– trends in biodiversity

• extinctions and radiations

Fig. 22.18


Ordovician

Devonian

Permian

Triassic

Cretaceous

Mill

ion

s o

f ye

ars

ag

o

Number of families

600

800 10006004002000

0

100

200

300

400

500

Fig. 21.10


2200 Oldest eukaryotes

4600

3800 First signs of life

Plants

Insects and amphibiansReptiles

Mammals and dinosaurs

First hominids

600

100

200

300

400

500

3500 Oldest fossils

2700

Millions ofyears ago

Extinction ofthe dinosaurs

Flowering plantsand first birds

Colonization ofland by animals

Vertebrates

Diversification of multicellularlife and algae

Oxygen increasesin the atmosphere

Fig. 22.14Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Ground and Cactus FinchesVegetarianTree Finch

WarblerFinches

Certhideafusca

Platyspizacrassirostris

Certhideaolivacea

Tree Finches

Cactospizapallida

Camarhynchuspauper

Camarhynchusparvulus

Geospizaconirostris

Geospizamagnirostris

Geospizafuliginosa

Geospizafortis

Geospizascandens

Geospizadifficilis

Camarhynchuspsittacula

Cactospizaheliobates

Fig. 22.15


Secondset of jaws

Leaf eater

Snail eater

Insect eater

Zooplankton eater

Algae scraper

Fish eater

Scale scraper

Macroevolution

• The study of– pace of evolution

Fig. 22.17


Tim

e

a. Gradualism b. Punctuated equilibrium

Pace of Evolution

Macroevolution

• Fossil record provides the outline of macroevolution

• must also study extant species to provide the details

Documents

Evolution Genetic change in a lineage over time first convincing case put forth by –Charles Darwin