Transcript chapter17 - OCC

Evidence of Evolution
Chapter 17
Impacts, Issues
Measuring Time
 Evidence of events that happened millions of
years ago – such as meteor impacts – lead to
inferences about evolution of life on Earth
17.1 Early Beliefs,
Confounding Discoveries
 Belief systems are influenced by the extent of
our knowledge
 Beliefs that are inconsistent with systematic
observations of the natural world tend to change
over time
Naturalists and Biogeography
 Aristotle was one of first naturalists – people
who observe life from a scientific perspective
 In the late 1800s, Alfred Wallace and others
were pioneers in biogeography – the study of
patterns in the observation of species
Patterns in Biogeography
Comparative Morphology
 Comparative morphologists study body plans
and structures among groups of organisms
• Some organisms are outwardly similar, but
different internally; others differ outwardly, but
have similar internal structures
• Some organisms have vestigial parts with no
apparent function
Vestigial Body Parts
coccyx
limb
bud
Fig. 17-3, p. 261
Geology
 Geologists found identical sequences of rock
layers in different parts of the world
• Different layers held different fossils – evidence
of earlier forms of life
 Cumulative findings from biogeography,
comparative morphology, and geology led to
new ways of thinking about the natural world
Fossils
17.2 A Flurry of New Theories
 By the 1800s, many scholars realized that life on
Earth had changed over time, and began to think
about what could have caused the changes
New Evidence and Old Beliefs
 Catastrophism
• Georges Cuvier proposed that many species that
once existed became extinct due to catastrophic
geological events unlike those known today
 Gradualism
• Jean-Baptiste Lamarck proposed that individuals
changed in response to their environment, and
passed those changes on to their descendents
Reconsidering Old Beliefs
 Theory of uniformity
• Lyell’s book, Principles of Geology, proposed that
gradual, repetitive geological processes shaped
the Earth over great spans of time
• Lyell’s insights shaped Charles Darwin’s thinking
during his five-year voyage on the Beagle
Voyage of the Beagle
 Darwin observed unusual fossils and diverse
species in a range of habitats
Beagle and The Galapagos Islands
17.1-17.2 Key Concepts
Emergence of Evolutionary Thought
 Long ago, naturalists started to catalog
previously unknown species and think about the
global distribution of all species
 They discovered similarities and differences
among major groups, including those
represented as fossils in layers of sedimentary
rock
17.3 Darwin and Natural Selection
 Darwin’s observations of species in different
parts of the world helped him understand a
driving force of evolution – natural selection
Old Bones and Armadillos
 Darwin observed similarities between fossil
glyptodons in Argentina and the armadillo
A Key Insight – Variation in Traits
 Darwin’s observations:
• Populations can produce more individuals than
their environment can support
• Some versions of a trait might enhance an
individual’s ability to survive and reproduce in its
particular environment
• Example: Finches in the Galapagos Islands
Finches in the Galapagos Islands
Natural Selection
 Natural selection
• Differential survival and reproduction among
individuals of a population that vary in details of
shared, inherited traits
 Adaptive trait
• Any trait that enhances an individual’s fitness
(ability to survive and reproduce in a particular
environment)
Principles of Natural Selection
Stepped Art
Table 17-1, p. 265
17.4 Great Minds Think Alike
 Darwin’s insights into evolution were made
possible by contributions of scientists who
preceded him
 Alfred Wallace independently developed the
idea of evolution by natural selection
Alfred Wallace
 Wallace drew on his own observations of plant
and animal species and proposed that natural
selection is a driving force of evolution
17.3-17.4 Key Concepts
A Theory Takes Form
 Evidence of evolution, or changes in lines of
descent, gradually accumulated
 Charles Darwin and Alfred Wallace
independently developed a theory of natural
selection to explain how heritable traits that
define each species evolve
17.5 About Fossils
 Fossils are remnants or traces of organisms that
lived in the past
 They give us clues about evolutionary
relationships
 The fossil record will always be incomplete
Fossils
 Fossils
• Remains of bones, teeth, shells, seeds, spores,
or other body parts
 Trace fossils
• Evidence of an organism’s activities (nests, trails,
footprints, burrows, bore holes, eggshells, feces)
Fossils
Fig. 17-9a, p. 267
Fig. 17-9b, p. 267
Fig. 17-9c, p. 267
How Do Fossils Form?
 Organisms or traces are covered in sediments or
volcanic ash
 Inorganic compounds dissolved in water slowly
replace minerals in bones and hard tissues
 Pressure and mineralization transform remains
into rocks
Fossil-Containing Sedimentary Rock
 The oldest fossils are usually in the deepest
layers of sedimentary rocks
The Fossil Record
 The fossil record will never be complete
• Geologic events obliterated much of it
• Slanted toward species with hard parts, dense
populations, wide distribution, long periods of time
• Substantial enough to help reconstruct patterns
and trends in the history of life, and establish
some lines of descent (lineages)
17.6 Dating Pieces of the Puzzle
 Researchers use predictable radioisotope decay
to estimate the age of rocks and fossils
 Radiometric dating
• Reveals the age of a material by determining its
radioisotope and daughter element content
Radioisotopes
 Radioisotope
• A form of an element with an unstable nucleus
• Decays into atoms of another element
• Example: uranium 238 → lead 206
 Half-life
• The time it takes for half of a radioisotope’s atoms
to decay into a daughter element
Half-Life
parent isotope
daughter isotope
newly
formed rock
after one half-life
after two half-lives
Fig. 17-11, p. 268
parent isotope
daughter isotope
newly
formed rock
after one half-life
after two half-lives
Stepped Art
Fig. 17-11, p. 268
Animation: Radioisotope decay
Carbon 14 Dating
Animation: Radiometric dating
17.7 A Whale of a Story
 New fossil discoveries are continually filling the
gaps in our understanding of the ancient history
of many lineages
New Links in the
Ancient Lineage of Whales
New Links in the
Ancient Lineage of Whales
New Links in the
Ancient Lineage of Whales
17.5-17.7 Key Concepts
Evidence From Fossils
 The fossil record offers physical evidence of past
changes in lines of descent
 We use the property of radioisotope decay to
determine the age of rocks and fossils
17.8 Putting Time into Perspective
 Geologic time scale
• The chronology of Earth’s history
• Measured by radiometric dating and fossils in
similar sequences of sedimentary rock layers
around the world
The Geologic Time Scale
Fig. 17-14a, p. 270
Fig. 17-14b, p. 271
Animation: Geologic time scale
17.9 Drifting Continents, Changing Seas
 For billions of years, slow movements of Earth’s
outer layer and catastrophic events have
changed the land, atmosphere, and oceans, with
profound effects on the evolution of life
Continental Drift
 Continental drift
• All continents were once part of a supercontinent
– Pangea – that split and drifted apart
• Evidence: Magnetic rocks
 Plate tectonics
• The mechanisms of continental drift
• Plate grow from ridges and sink into trenches
Plate Tectonics
trench
A
A Plumes of
molten rock
rupture a
tectonic plate at
what are called
“hot spots.”
The Hawaiian
Archipelago has
been forming
this way.
hot spot
ridge
B
B At oceanic ridges,
huge plumes of molten
rock welling up from
Earth’s interior drive the
movement of tectonic
plates. New crust
spreads laterally as it
forms on the surface,
forcing adjacent tectonic
plates away from the
ridge and into trenches
elsewhere.
trench
C
C At trenches, the
advancing edge of
one plate plows under
an adjacent plate
and buckles it. The
Cascades, Andes,
and other great
coastal mountain
ranges formed this
way.
rift
D
D At rifts,
continents rupture
in their interior as
plates slide apart
from each other.
Fig. 17-15, p. 272
Boundaries of Tectonic Plates
 San Andreas Fault
Gondwana
 Supercontinents continually form and split,
altering habitats and influencing evolution
 Gondwana
• Ancient supercontinent, older than Pangea
• Similar fossils and geologic formations in Africa,
India, South America and Australia
The Drifting Continents
A 420 mya
B 237 mya
C 152 mya
D 65.5 mya
E 14 mya
Fig. 17-17, p. 273
Fig. 17-17 (top left), p. 273
Fig. 17-17 (top right), p. 273
17.8-17.9 Key Concepts
Evidence From Biogeography
 Correlating evolutionary theories with geologic
history helps explain the distribution of species,
past and present
Animation: Comparative pelvic anatomy
Animation: Continental drift
Animation: Finches of the Galapagos
Animation: Geologic forces
Animation: Plate margins
Animation: The Galapagos Islands
ABC video: Creation vs. Evolution
ABC video: Chickens have a new
ancestor
ABC video: Indonesian Earthquake
ABC video: Asteroid Menace
Video: Measuring time