Transcript Chapter 8: Developing a Theory of Evolution

UNIT 3: Evolution
Chapter 7: Introducing Evolution
Chapter 8: Developing a Theory
of Evolution
What is the theory of evolution, and what
evidence is there to support it?
Chapter 9: Evolution and Speciation
UNIT 3 Chapter 8: Developing a Theory of Evolution
8: Developing a Theory of Evolution
Any scientific theory requires evidence to support its
assumptions or postulates. Fossils, such as these trilobites,
support the scientific theory of evolution as it relates to life
on Earth.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
8.1 Scientific Contributions to a Theory
of Evolution
John Ray (1627-1705)
• one of the first scientists to carry out empirical studies on
the natural world
• developed a classification system for plants and animals
based on anatomy and physiology (refined by Linnaeus)
Georges-Louis Leclerc, Comte de Buffon (1707-1788)
• one of the first people to publicly challenge the idea that
life forms are unchanging
• speculated that Earth was more than 6000 years old
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Scientific Contributions to a Theory
of Evolution
Mary Anning (1799-1847)
• worked as a fossil hunter and
uncovered the first plesiosaur
• work was confirmed by Georges
Cuvier, the founder of paleontology
Mary Anning was very
skilled at collecting
fossils. As a result, she
made many important
contributions to the field
of paleontology.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Catastrophism
Georges Cuvier (1769-1832)
• credited with founding the field of paleontology (study of fossils)
• discovered that each stratum (layer) of rock held a unique group of
fossil species
• discovered that the oldest fossils are in the deepest layer
• suggested that catastrophes killed many species (catastrophism)
and that these events corresponded to the boundaries between the
fossil strata
Deep rock strata are
older than strata closer
to the surface. Different
species of fossilized
organisms can be found
in different sedimentary
rock strata. This is
evidence that not all life
forms came into
existence at the same
time.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Uniformitarianism
Charles Lyell (1797-1875)
• rejected Cuvier’s theory of catastrophism
• proposed the theory of uniformitarianism: geological
processes in the past operate at the same rate as they do today
• suggested that a slow and continuous process could result in
substantial changes in the long term
• agreed that Earth was more than
6000 years old
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Line of Descent
Jean-Baptiste Lamarck (1744-1829)
• proposed a “line of descent” progression between current
species and fossil forms
• suggested species increased in complexity and became better
adapted to their environment over time
• proposed the idea of the inheritance of acquired
characteristics whereby characteristics
acquired during an organism’s lifetime
could be passed on to offspring
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Evolution by Natural Selection
Thomas Malthus (1766-1834)
• an economist who wrote Essay on the Principles of Population that
explained how populations might change over time
• key idea was that populations produce far more offspring than their
environments can support
Charles Darwin (1809-1882)
• travelled the coast of South America and made natural and
geographical observations
• used these observations to propose the theory of natural
selection: how life has changed and continues to change, due to
natural pressures, the first comprehensive presentation of the idea
Alfred Russel Wallace (1823-1913)
• made observations and conclusions similar to Darwin’s
• Darwin and Wallace recognized the importance of Malthus’s essay
UNIT 3 Chapter 8: Developing a Theory of Evolution
Evolution by Natural Selection
The five-year voyage of the HMS Beagle took
Darwin around much of the world. He spent
most of his time exploring the coast and
coastal islands of South America.
Section 8.1
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Evolution by Natural Selection
The theory of evolution by natural selection includes the idea of
survival of the fittest as discussed in Darwin’s The Origin of Species:
• Organisms produce more offspring
than can survive. Therefore, organisms
compete for limited resources.
• Individuals of a population vary
extensively, and much of this variation is
heritable.
• Individuals that are better suited
(fitted) to local conditions survive to
produce more offspring.
• Processes for change are gradual.
The changes in populations can be viewed as descent with modification, as
the change does not demonstrate progress (improvement). It is simply
change.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Darwin’s Observations and Questions
Some of Darwin’s observations that led to his theory were:
• The flora and fauna were different in different regions.
• He found fossils of extinct animals that looked similar to
living animals.
• Finches found on islands resembled continental finches but
were different in some characteristics.
• Finch beaks were adapted to the food source on each island.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1
Darwin’s Observations and Questions
Questions that Darwin considered:
• Why were all types of organisms not randomly distributed?
• Why would living and fossilized organisms that looked
similar be found in the same region?
• Why did the Galapagos species so closely resemble
organisms on the adjacent South American coastline?
• Could species have been modified from an ancestral form
that arrived on the Galapagos Islands shortly after the islands
were formed?
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.1 Review
Section 8.1
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
8.2 Sources of Evidence for Evolution
The fossil record reveals the history of life on Earth.
Continued…
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
Sources of Evidence for Evolution
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
Fossil Evidence
The fossil record provides the following evidence:
• Fossils in younger (and usually closer to the surface) rock are
more similar to current species than those in deeper strata.
• Fossils appear in “chronological order” in the rock strata, and
probable ancestors of a species are found in older rocks.
• Not all organisms appear in the fossil record at the same time,
showing the successive evolution of groups (kingdoms) of
species.
Paleontologists have
used fossils to trace
the evolution of the
modern camel. The
Paleocene, Eocene,
Oligocene, and
Miocene epochs are
subdivisions of the
Cenozoic era.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
Fossil Evidence
Scientists are always looking for transitional fossils that show
an intermediary link between past and present groups of
organisms.
Vestigial structures are reduced versions of what were once
functional structures in an ancestral species. A key piece of
evidence is a fossil record that shows the once functional use
of a present day vestigial structure.
Fossil evidence suggests
that modern toothed whales
evolved from a terrestrial
ancestor, Pakicetus attocki.
Basilosaurus and Dorudon,
not shown in this illustration,
appear more recently in the
fossil record, after the
appearance of Rodhocetus.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
Evidence from Biogeography
Biogeography is the study of the past and present geographical
distribution of organisms. Darwin and Wallace supported their
theories with biogeographical evidence showing that species
evolved in one location and spread out to other regions.
• Geographically close environments are more likely to be
populated by related species.
• Animals found on islands often closely resemble animals on
the nearest continent.
• Fossils of the same species can be found
on the coastlines of neighbouring continents.
As the southern supercontinent Gondwana
broke apart about 150 million years ago, the
land masses that became the current
continents of Africa, Australia, South America,
and Antarctica were isolated from each other.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
Evidence from Anatomy
The study of anatomy provides the following evidence:
• Homologous structures are those that have similar structural
elements and origin but may have a different function. They
originate from a common ancestor. Examples include forelimbs
in vertebrates and mammalian hairs.
• Analogous structures do not have a common evolutionary
origin but perform similar functions. These provide evidence for
adaptation to suit the environment. An example is the fins of a
porpoise and a fish.
What type of
anatomical evidence
of evolution is shown
in the images?
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
Evidence from Embryology
Embryology is the study of pre-birth stages of an organism’s
development. It has been used to determine evolutionary
relationships between animals:
• Generally, related species
share common embryological
stages and timings of
structural development.
• All vertebrate embryos
have paired pouches, or outpocketings, of the throat
(these later develop into
ears/throat or gills).
Similarities in the embryos of fish, birds, and mammals
provide evidence of evolution of species from a
common ancestor.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2
Evidence from DNA (Molecular Evidence)
Evolutionary relationships are reflected in DNA since DNA
carries genetic information from generation to generation:
• Species that have
similar DNA share a
common ancestor.
• DNA evidence supports
conclusions about
relationships and common
ancestry provided by other
areas of evidence.
UNIT 3 Chapter 8: Developing a Theory of Evolution
Section 8.2 Review
Section 8.2
UNIT 3 STSE Feature: Biology Connections
T. rex and chickens share a common ancestor?