Transcript Chapter 16 Darwin`s Theory of Evolutionx

Chapter 16.1: Darwin’s Theory of Evolution:
Objectives:
1. State Charles Darwin’s contribution to science.
2. Describe the three patterns of biodiversity
noted by Darwin.
Darwin’s Epic Journey

Charles Darwin – Naturalist
Born in England in 1809
Developed the theory of
evolution.
Darwin’s Epic Journey
Dates: February 12th, 1831
 Ship: H.M.S. Beagle
 Destination: Voyage around the world
 Findings: Collected thousands of plant & animal
specimens to propose a hypothesis about how life
changes over time.

Differences Among Organisms
•
•
Species: A group of organisms that
can mate with one another to
produce fertile offspring.
Adaptation: Characteristic that
helps an organism survive and
reproduce in its environment.
Observations Aboard the Beagle
Darwin noticed 3 patterns of
biological diversity:

Species
vary globally
Species vary locally
Species vary over time
Species Vary Globally

Similar species in different
continents?
 South
America: Rheas
 Africa: Ostrich
 Australia: Emu

Conclusion: Similar
environments produce
species with similar
adaptations.
Species Vary Locally: Galapagos Islands

Related species had
different adaptations
in different parts of
the same continent.
Example:
Hood
Island Tortoise
& Isabela Island
Tortoise
Finches
Isabela Island
Tortoise
Hood Island
Tortoise
Species Vary Locally: Galapagos Islands

Variation among finches on
different islands
Species Vary Over Time
Darwin also collected
fossils.
 Fossils: Traces of organisms
or “footprints”
 Fossil Record: Timeline of
life, organizing fossils by
their estimated ages and
physical similarities.

Species Vary Over Time

Darwin’s observations of fossils:
Extinct animals were similar to
living species
 Example:
 Extinct
Glyptodont vs. Armadillo
Do Species Change over Time?


As populations and their environment change
over time, new species form.
Evolution: The process in which populations
gradually change over time.
Chapter 16.2 Essential Questions
What did Hutton and Lyell
conclude about Earth’s history?
 How did Lamarck propose that
species evolve?
 What was Malthus’s view of
population growth?
 How is inherited variation used
in artificial selection?

Ideas That Shaped Darwin’s Thinking
Geologists Lyell + Hutton discovered that EARTH:
 Was much older than previously thought
 Changed and is still changing in the same pattern
 Principles of Geology, 1809
 These ideas helped shaped Darwin’s theories about
how organisms adapt to changes on Earth

Lamarck’s Evolutionary Hypotheses


Jean Baptiste Lamarck:
1st naturalist to study
adaptations
Suggested 2 theories:
Acquired
characteristics
Inheritance of acquired
characteristics
Lamarck’s Evolutionary Hypotheses

Theory of acquired characteristics (1809):
 Organisms
acquire traits during their lifetime to
adapt to their environment
 Driven by innate tendency toward perfection
 Pertained to both use and disuse

Theory of inheritance of acquired
characteristics:
 Traits
acquired during an organism’s lifetime can
be passed on to their offspring.
 Example: Giraffe’s neck
Lamarck Was Wrong!!!



Phenotypic changes do not result
in genotypic changes.
However, he was the first to link
organism’s environment to its
body changes.
Darwin built his theory using
Lamark’s ideas.
Population Growth

Thomas Malthus (1798)
 The
rate of people being born is
higher than the rate of people
dying
 Theory: If this rate continues, there
won’t be enough food and living
space.

Darwin related this idea to other
organisms, and started wondering
why overcrowding does not exist
in nature.
Artificial Selection
Darwin studied artificial selection by plant and
animal breeders.
 Artificial selection: Selective breeding
i.e. Can produce variation among species
(pigeons)
 Darwin realized variation in nature was key for
evolution to occur.

Darwin’s Thinking –
Ideas About Population



Only a limited number of individuals
survive to reproduce in a population.
Survivors must have favorable traits.
Only the strongest species will go on to
have offspring with these favorable traits.
Chapter 16.3 Essential Questions


Under what conditions does natural
selection occur?
What does Darwin’s mechanism for
evolution suggest about living and
extinct species?
Natural Selection

1859, Darwin’s theory
of evolution was
published
On
the Origin of
Species by Means of
Natural Selection

Theory of Natural Selection:
1.
2.
3.
The Struggle for Existence
Variation and Adaptation
Survival of the Fittest
Natural Selection

1. The Struggle for Existence
Population
rate forces species to
compete for resources
Natural Selection

2. Variation and Adaptation
Variations
are due to adaptations
to the environment
Adaptation:
Characteristics
increasing
ones chance of survival

Natural Selection
3. Survival of the Fittest
Adaptations
High
fitness
Individuals
Low
effect an individual’s fitness
have a better advantage
fitness
Individuals
die before having offspring
Natural Selection

Three types of Adaptations:
1.
2.
3.
Structural
Physiological
Behavioral
1. Structural Adaptations
Camouflage
Mimicry
Warning Coloration
Structural Adaptations
Duck---webbed feet
 Fish---gills
 Giraffe---long neck
 Beaver---large teeth
 Whale---blubber
 Snake---flexible jaw
 Platypus---bill

2. Physiological Adaptations
Chemicals
Toxins
Body Temperature
3. Behavioral Adaptations
Scaring Predators
Hibernating
Migrating in “V”
Staying in Groups
Mating Calls
Darwin’s Theory of Natural Selection

Natural Selection:
Individuals better
adapted to their
environment survive and
reproduce more
successfully than less well
adapted individuals
Natural Selection – Insect Resistance
Darwin’s Theory of Natural Selection

Genetics and Evolution
 Darwin’s
theory (1858) lacked explanation of
inheritance of traits and variation
 Mendelian genetics (1900s)
Variation is due to differences in genes
Darwin Presents His Case
Over time adaptation could cause
successful species to evolve into new
species
 Living species are descended from
common ancestors (Descent with
modification)

 1st

evolutionary tree
Principle of common descent
 All
species are related to a common
ancestor (tree of life)
Evidence of Evolution
Exploring Various Lines of
Evidence for the Theory of
Evolution
Lines of Evidence
• Biogeography
• Comparative
Anatomy
• Embryology
• Fossil Record
• DNA Sequences
Biogeography
• Biogeography
is the study of
the global
pattern of
distribution of
species and
their
ancestors.
Patterns in Distribution (2 Types)
• Closely Related But Different
– Finches developed different variations
depending on the environment of their island
but all had a common ancestor from the
mainland.
• Distantly Related but Similar
– Similar species (rheas, ostrich, emu) in
different grasslands (Europe, Australia, Africa)
do not share a common ancestor, but
developed similar adaptations.
Evidence for Evolution
– Radioactive dating is a technique used to
date materials such as rocks, by comparing
its abundance of a naturally occurring
radioactive isotope to its known decay rates.
– Determined Earth is about 4.5 billion years
old
Evidence for Evolution:
The Fossil Record
Evidence for Evolution
• Fossil Record
– Provides evidence about
the order in which species
have existed
Whale Evolution
Comparing Anatomy &
Embryology
• Homologous Structures: Similarities in
structures b/w species suggest they descended
from a common ancestor
• Includes bone structures and embryological
development
Comparative Anatomy
• Homologous
Structures
• Note the colorcoded bones
for the limbs of
these 4
mammals –
though
different, they
share many
similar bones.
Comparative Anatomy
• Same arrangement of bones in cats,
dolphins, bats, and humans suggest
they share a common ancestor.
Comparing Anatomy & Embryology
• Analogous Structures:
Body parts that share
common function, but not
structure. Do not share a
common ancestor.
– Example: Wing of a bird and
an insect
• Vestigial structures:
Structures inherited from
ancestors that are no
longer necessary and have
lost their function.
– Ex: Hip bone of whale
Genetics and Molecular Biology
• Genetics gives evidence of common
descent among organisms.
• We also know that variation is due to
shuffling and crossing over in meiosis.
DNA Sequences
• Scientists are able
to isolate pieces of
DNA.
• Species that are
more closely related
tend to have more
similarities in their
DNA.
DNA Sequences
• Leptin = Protein hormone
important for regulating body
weight and metabolism
• Mice without properly functioning
leptin gene are morbidly obese
(right) compared to normal mice
(left).
Testing Natural Selection
• Darwin’s finches hypothesis:
– Beaks of finch species evolved to adapt to the
type of food available on the island.
– Recently tested by Peter and Rosemary Grant
to be true.
Testing Natural Selection
• Natural Selection:
– The Grants found that if the environment changes
quickly and unexpectedly, that finch populations could
evolve within decades, confirming that competition
and environmental change drive natural selection.
– They also showed that variation increases a
populations chances of survival.
Biogeography
• Marsupial
Marsupialsdistribution
are a group
across
of mammals
the globe:
that
http://evolution.berkeley.edu/evolibrary/arti
give
birth to live young that develop in an
cle/0_0_0/lines_11
outer
pouch of the mother. Bandicoot
• Distribution today split on two sides of
globe – how?
• Review a few facts of the distribution and Koala
marsupials, as well as the history of the
Earth, then formulate hypothesis behind
Opossum
distribution
Sugar Glider
Kangaroo
Biogeography
How do you think some marsupials
ended up halfway across the world
from the others?
Biogeography
Continental Drift over millions of years –
watch the movement of land masses
Biogeography
Continental Drift + Distribution of Marsupials