Ch. 25 The History of Life on EarthObjective:

L.O. 1.9 TSIAT: evaluate evidence provided by data from many scientific disciplines that support biological evolution.L.O. 1.10 TSIAT: refine evidence based on data from many scientific disciplines that support biological evolution.L.O. 1.11 TSIAT: design a plan to answer scientific questions regarding how organisms have changed over time using information from morphology, biochemistry and geology.L.O. 1.12 TSIAT: connect scientific evidence from many scientific disciplines to support the modern concept of evolution.L.O. 1.13 TSIAT: construct and/or justify mathematical models, diagrams or simulations that represent processes of biological evolution.L.O. 1.14 TSIAT: pose scientific questions that correctly identify essential properties of shared, core life processes that provide insights into the history of life on Earth.L.O. 1.15 TSIAT: describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms.L.O. 1.16 TSIAT: justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today.L.O. 1.20 TSIAT: analyze data related to questions of speciation and extinction throughout the Earth’s history.L.O. 1.21 TSIAT: design a plan for collecting data to investigate the scientific claim that speciation and extinction have occurred throughout the Earth’s history.L.O. 1.27 TSIAT: describe a scientific hypothesis about the origin of life on Earth.L.O. 1.28 TSIAT: evaluate scientific questions based on hypotheses about the origin of life on Earth.L.O. 1.29 TSIAT: describe the reasons for revisions of scientific hypotheses of the origin of life on Earth.L.O. 1.30 TSIAT: evaluate scientific hypotheses about the origin of life on Earth.L.O. 1.31 TSIAT: evaluate the accuracy and legitimacy of data to answer scientific questions about the origin of life on Earth.L.O. 2.31 The student can connect concepts in and across domains to show that timing and coordination of specific events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.L.O. 2.32 TSIAT: use a graph or diagram to analyze situations or solve problems (quantitatively or qualitatively) that involve timing and coordination of events necessary for normal development in an organism.L.O. 2.33 TSIAT: justify scientific claims with scientific evidence to show that timing and coordination of several events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.L.O. 4.20 TSIAT: explain how the distribution of ecosystems changes over time by identifying large-scale events that have resulted in these changes in the past.L.O. 4.21 TSIAT: predict consequences of human actions on both local and global ecosystems.

Overview• Currently, the largest

fully terrestrial animal in Antarctica is a 5mm long fly.

• However, fossils on Antarctica show a history of tropical animals, including dinosaurs.

• An ever changing world give rise to new organisms, but what was the first organic being on Earth?

25.1 Conditions on Early Earth Made The Origin of Life Possible

• Life began in 4 stages:1. Abiotic synthesis of small organic molecules (amino

acids and nitrogen bases)2. The joining of these small molecules into

macromolecules (proteins and nucleic acids)3. The packaging of these molecules into protocells,

droplets with membranes that maintained an internal chemistry different from that of their surroundings.

4. The origin of self-replicating molecules making inheritance possible.

Synthesis of Organic Compounds

• Earth formed ~4.6 b.y.a.• Earth was hot.• Bombardment by rocks and ice (comets).• Early atmosphere likely contained:

– water vapor– chemicals from volcanic eruptions (N2 and its oxides,

CO2, methane, ammonia, H2, hydrogen sulfide)

• Earth cooled forming oceans

• In 1953, Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible

• The first organic compounds may have been synthesized near volcanoes or deep-sea vents due to reducing properties.

EXPERIMENT“Atmosphere”

Electrode

Condenser

CH4

H 2NH

3

Water vapor

Cooled “rain”containingorganicmolecules

Cold water

Sample for chemical analysis

H2O “sea”

© 2011 Pearson Education, Inc.

Video: Tubeworms

© 2011 Pearson Education, Inc.

Video: Hydrothermal Vent

Macromolecules and Protocells• Dropping monomers on

hot “Earth” produces polymers (amino acids proteins; nucleotides RNA)

• Vesicles form when lipids are added to water.– Formation of lipid bilayer

• These vesicles absorb molecules near their surroundings (early proteins and RNA).

(a) Self-assembly

Time (minutes)

Precursor molecules plusmontmorillonite clay

Precursor molecules onlyRe

lativ

e tu

rbid

ity,

an in

dex

of v

esic

le n

umbe

r

0

20 m

(b) Reproduction (c) Absorption of RNA

Vesicle boundary

1 m

0

0.2

0.4

4020 60

• RNA serves as instructions for protein synthesis as well as acts as enzymes.

• RNA molecules that were more stable or replicated more quickly would have left the most descendent RNA molecules.

• Copying errors occurred (mutations) leading to slight differences and thus natural selection.

25.2 The Fossil Record Documents The History of Life

• Fossils are only made in certain conditions, making the fossil record incomplete.– However, it can be seen how extinct species could

have given rise to current ones (sepciation).Dimetrodon

Stromatolites

Fossilizedstromatolite

Coccosteuscuspidatus

4.5 cm

0.5 m

2.5 cm

Present

Rhomaleosaurus victor

Tiktaalik

Hallucigenia

Dickinsonia costata

Tappania

1 cm

1 m

100 mya

175200

300

375400

5005255656001,500

3,500

270

Figure 25.4

© 2011 Pearson Education, Inc.

Animation: The Geologic Record Right-click slide / select “Play”

• Dating Fossils– Relative dating: older fossils are lower in the

Earth’s strata.– Absolute dating (exact age) uses radiometric

dating: use of half life’s of radioactive isotopes within the fossil.

Accumulating “daughter”

isotope

Frac

tion

of p

aren

t is

otop

e re

mai

ning

Remaining “parent” isotope

Time (half-lives)1 2 3 4

1 2

1 41 8 1 16

The Origin of New Groups of Organisms• Ex: mammals

– Mammals belong to the group of animals called tetrapods– Evolution of unique mammalian features can be traced through gradual

changes over time

OTHERTETRA-PODS

Temporal fenestra

Hinge

†Dimetrodon

†Very late (non-mammalian) cynodonts

Mammals

Synapsids

Therapsids

Cynodonts

Reptiles (including dinosaurs and birds)

Key to skull bones

ArticularQuadrate Squamosal

Dentary

Temporal fenestra

HingeHinge

Hinge

Hinges

Temporal fenestra(partial view)

Early cynodont (260 mya)

Very late cynodont (195 mya)

Synapsid (300 mya)

Therapsid (280 mya)

Later cynodont (220 mya)

25.3 Key Events in Life’s History Included The Origins of Single-celled and Multicellular Organisms and the Colonization of Land

Geologic Time Scale•Boundaries formed by major extinction events•3 Eons (Archaean, Proterozoic, Phanerozoic)•Phanerozoic (current eon) divided into Eras

– Paleozoic – age of trilobites to amphibians– Mesozoic – age of reptiles– Cenozoic – age of mammals

Origin of solar system and Earth

Prokaryotes

Atmospheric oxygen

Archaean

4

3

Proterozoic

2

Animals

Multicellular eukaryotes

Single-celled eukaryotes

Colonization of land

Humans

CenozoicMeso-

zoic

Paleozoic

1

Billions of years

ago

First Single-Celled Organisms• Stromatolites are rocks formed from

prokaryotes bind sediment together.– Thought to be 1st cells

• Cells began to photosynthesize, releasing O2 into the atmosphere.

Stromatolites

The First Eukaryotes•Formed 2.1 b.y.a. by the endosymbiont theory.

– Ancestral mitochondria and chloroplasts were their own type of prokaryotic cells.

– Mitochondria were up taken by protocells, then chloroplasts.

Plasma membrane

DNA

Cytoplasm

Ancestralprokaryote

Nuclear envelope

Nucleus Endoplasmic reticulum

Aerobic heterotrophicprokaryote

Mitochondrion

Ancestralheterotrophic eukaryote

Photosyntheticprokaryote

Mitochondrion

Plastid

Ancestral photosyntheticeukaryote

The Origin of Multicellularity• Formed ~1.5 b.y.a.• First multicellular

organism was algae.• After “snowball Earth”

(long ice age), the Cambrian explosion occurred creating all the phyla that currently exist and 1st predator-prey interactions.

Sponges

Cnidarians

Echinoderms

Chordates

Brachiopods

Annelids

Molluscs

Arthropods

Ediacaran Cambrian

PROTEROZOIC PALEOZOIC

Time (millions of years ago)

635 605 575 545 515 485 0

Colonization of Land

• Fungi, plants, and animals colonized land ~500 m.y.a.

• Arthropods and tetrapods are the most widespread and diverse land animals– Tetrapods evolved from lobe-finned fishes ~365 m.y.a.

25.4 The Rise and Fall of Groups of Organisms Reflect Differences in Speciation and Extinction Rates

• Earth’s crust is broken into plates that are constantly in motion (moving 2cm/yr).

• This causes changes in habitats and climates on Earth over time (Antarctica used be near the equator). Move, adapt, or die.

Juan de FucaPlate

NorthAmerican Plate

CaribbeanPlate

Cocos Plate

PacificPlate

NazcaPlate

SouthAmericanPlate

Eurasian Plate

Philippine Plate

Indian Plate

African Plate

Antarctic Plate

Australian Plate

Scotia Plate

Arabian Plate

65.5

135

251

Pre

sen

t

Cen

ozo

ic

North Americ

a

Eurasia

AfricaSouthAmerica

India

Antarctica

MadagascarAustra

lia

Mes

ozo

icP

aleo

zoic

Mil

lio

ns

of

year

s ag

o

Laurasia

Gondwana

Pangaea

Mass Extinctions• Many species died on Earth around the same time

frames.– 5 mass extinctions have been recorded.– b/w Paleozoic and Mesozoic 96% marine life died! (volcano)– b/w Mesozoic and Cenozoic killed dinosaurs, etc. (meteor)

25

20

15

10

5

0

542 488 444

EraPeriod

416

E O S D

359 299

C

251

P Tr

200 65.5

J C

Mesozoic

P N

Cenozoic

0

0

Q

100

200

300

400

500

600

700

800

900

1,000

1,100

To

tal

exti

nct

ion

rat

e(f

amil

ies

per

mil

lio

n y

ears

):

Nu

mb

er o

f fa

mil

ies:

Paleozoic

145

NORTH AMERICA

YucatánPeninsula

Chicxulubcrater

Consequences of mass extinctions• Loss of current diversity of life on Earth• Opens up the way for new life

Adaptive Radiation• Many species adapted from 1 due to many new

environmental challenges.– Global: Extinction of dinosaurs mammal flourished– Regional: Hawaiian Islands newly created and bare for

organisms to diversify on.

Dubautia laxa

Dubautia waialealae

KAUA'I5.1

millionyears O'AHU

3.7millionyears

LANAI

MOLOKA'I1.3 million years

MAUI

HAWAI'I0.4

millionyears

Argyroxiphium sandwicense

Dubautia scabra Dubautia linearis

N

25.5 Major Changes in Body Form Can Result From Changes in The Sequences and Regulation of Developmental Genes

Effects of Developmental Genes• Current organisms are genetically similar to ancestors, but

developmental timing makes them physiologically different.– Ex: heterochrony between chimps and humans.– Ex: Paedomorphosis in salamanders (juvenile anatomy in adults)

Chimpanzee infant Chimpanzee adult

Chimpanzee adult

Human adultHuman fetus

Chimpanzee fetus

Gills

Changes in Spatial Pattern• Hox (homeotic) genes tell cells how to

develop according to where it is located on the embryo.

Changes in Genes• Changes in developmental genes can result in new

morphological forms– Probably from duplications– Ex: Specific changes in the Ubx gene have been identified

that can “turn off” leg developmentHox gene 6 Hox gene 7 Hox gene 8

Ubx

About 400 mya

Drosophila Artemia

Changes in Gene Regulation• Change in regulation, not sequence of DNA.

– Ex: threespine sticklebacks in lakes have fewer spines than their marine relatives

– The gene sequence remains the same, but the regulation of gene expression is different in the two groups of fish

Threespine stickleback(Gasterosteus aculeatus)

Ventral spines

25.6 Evolution is Not Goal Oriented• Evolutionary Novelties

– Human Eye: a complex organ … how did it evolve?

• Improve on given structure based on current function

• Start simple – photoreceptors that tell light from dark

• Cup photoreptors in round shape.

• Filter light through a pupil• Focus light with a lens• Protect eye with cornea

Pigmented cells(photoreceptors)

Epithelium

Nerve fibers

Pigmentedcells

Nerve fibers

Fluid-filled cavity

Epithelium

Cellularfluid(lens)

Cornea

Optic nerve

Pigmentedlayer (retina)

Opticnerve

Cornea

Lens

RetinaOptic nerve

(a) (b)

(d)(c)

(e)

Evolution is NOT Goal Oriented• Organisms don’t think “I need wings” and are

then able to make wings over generations.• Organisms use what they have that helps

them currently.