Chapter 1: An Evolutionary Framework for Biology

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Chapter 1 An Evolutionary Framework for Biology

• Introduction
•  Evolution- What is it?
•  Rise of Evolutionary Thought
• Charles Darwin and Evolutionary Theory

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Chapter 21 The Mechanisms of Evolution
CHAPTER 21The Mechanisms of Evolution

• Early ideas- Lamarck and influence of the
  environment
•  Darwin and natural selection
• Evolution since Darwin

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Chapter 22 Species and their Formation

• What Are Species?
•  How Do New Species Arise?

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Introduction

• Evolution - What is it?
• Descent with modification
• Common Misconceptions idea of
  progress humans as pinnacle of evolution

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Introduction

• Evolution unites all of biology.
• Nothing in biology makes sense except in light
  of evolution.
• Evolution is as close to being a fact as is
  anything in science.

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Rise of Evolutionary Thought

• Scala Naturae ladder of life life forms
  arranged on a scale of increasing complexity
• Humans
• Mammals
• Birds
• Amphibians
• Fish

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Rise of Evolutionary Thought
Strong influence of religion-reinforce the idea
that life was the result of special creation and
that life forms were individually created,
permanent and unchanging. Importance of
fossils show that earth has had a succession of
plant and animal life. Recognition that
extinction was a common occurrence.
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Rise of Evolutionary Thought
How does life evolve? Lamarck- first to
propose a mechanism-- influence of the
environmment 1) through use an organ becomes
stodnger 2) these modification passed onto
offspring- inheritance of acquired
characteristics 3) Classic example giraffe neck
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Charles Darwin 1809-1882

• Early life studied medicine but found lectures
  dull and clinical aspects ghastly.
• Voyage of Discovery-hired as naturalist on H.M.S.
  Beagle- geographical survey of coastlines around
  the world.

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Voyage of Discovery
When left England -He had not least doubt
about the strict and literal truth of every
word in the Bible. When and what changed his
mind?
From observations of plants and animals
realized considerable diversity in nature.
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Voyage of Discovery
Best example Galapagos islands - fewer
species on islands - island species most similar
to nearby mainland species - island species
show diversity not seen on mainland CONCLUSION
island species have been modified from mainland
species since arrival on islands.
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Galapagos islands
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22.5 Part 1

• Figure 22.5 Part 1

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Charles Darwin

• Darwin based his arguments regarding mechanisms
  of evolution on artificial selection by plant and
  animal breeders.

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Mechanism of Evolution Natural Selection
Organisms vary. More offspring produced
than can possibly survive. Usually offspring
with variations favored by the environment will
survive. Variations favored by environment
accumulate - adaptations
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On the origin of Species-1859
Species are not immutable, but change or adapt
over time. Mechanism of change is natural
selection.
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Evolutionary mechanisms since Darwin

• Modern genetics has elucidated the mechanisms of
  heredity, which have provided the solid base that
  supports and substantiates Darwins theory.

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Other Mechanisms of Evolution
Genetic Drift changes in gene pool of
population due to chance -Bottleneck effect
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Elephant seals-bottleneck
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Maintaining Genetic Variation

• Sexual reproduction generates an endless variety
  of new combinations of genetic material on which
  natural selection can act.

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Constraints on Evolution

• Natural selection acts by modifying what already
  exists. A population cannot get temporarily worse
  in order to achieve some long-term advantage.

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Chapter 22 Species and their Formation

• What Are Species?
• How Do New Species Arise?

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What Are Species?

• Species mean different things to different
  people.
• A commonly accepted definition (BSC)is that
  species are groups of actually or potentially
  interbreeding natural populations which are
  reproductively isolated from other such groups.

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• Problem with biological species concept
• Interbreeding among species-viable hybrids- coy
  dogscoyotes dogs
• asexual populations-many bacteria

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Evolutionary Species Concept

• Species as a lineage (ancestor -descendant
  population) that remains separate from other
  lineages.
• Recognizes phylogeny as important.

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What Are Species?

• Because speciation is often a gradual process, it
  may be difficult to recognize boundaries between
  species. Review Figure 22.2

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22.2
figure 22-02.jpg

• Figure 22.2

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How Do New Species Arise?

• Allopatric or geographic speciation is the most
  important means of speciation among animals and
  is common in other groups of organisms.

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22.3

• Figure 22.3

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How Do New Species Arise?

• Species may form sympatrically by subdivision of
  gene pool that is not result of geographic
  separation but behaviorally. It is more common
  among plants than animals.

- Fruit fly (Rhagoletis) -lay eggs on hawthorn
berry in upstate NY - Apple trees planted-some
fruit flies laid eggs of apples instead-over time
two sympatric species formed-each feeding on
different fruit.
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Evolutionary Radiations

• Evolution of many diversely adapted populations
  from a common ancestor

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The Significance of Speciation

• As a result of speciation, Earth is populated
  with millions of species, each adapted to live in
  a particular environment and to use resources in
  a particular way.