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Introduction: Evolution Natural Selection and Species

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Pre-1850s: Thoughts on the Origin of Life. Earth believed to be only thousands of years old ... Horse donkey - mule (infertile) ... – PowerPoint PPT presentation

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Title: Introduction: Evolution Natural Selection and Species


1
Introduction Evolution Natural Selection and
Species
  • Professor Pamela L. Pannozzo
  • Principles of Biology II BSC 1011

2
Where Does Biological Diversity Come From?
3
Pre-1850s Thoughts on the Origin of Life
  • Earth believed to be only thousands of years old
  • Different organisms and their structures were the
    results of the Creator
  • Species were specially created and unchangeable
    over time

4
A Journey Charles Darwin and the HMS Beagle
  • 1831 - 22 year old Charles Darwin served as
    naturalist on a five-year mapping expedition
    around the world
  • Studied and collected plants and animals
  • Examined fossils
  • Observed series of related but distinct forms of
    life

5
Charles Darwins 5 Year Expedition
6
Darwins Observations
  • Earth of great geological change
  • Earthquakes, volcanoes, ancient oceans
  • Glyptodont fossils
  • Geographical distribution of species
  • Galapagos finches

7
Other Influences on Darwins Thinking
  • Thomas Malthus (1798) populations of plants and
    animals tend to increase exponentially resources
    are limited though reproductive rate is
    not?competition for survival
  • Charles Lyell (1830) geological and fossil
    records suggest Earth is very old and species
    have changed over time
  • Artificial Selection selective breeding of
    plants and animals to achieve certain desired
    characteristics in their offspring

8
…Darwins Postulates
  • Individuals vary in their traits
  • Traits are inherited
  • There is competition for limited resources
  • Only the most fit organisms are able to
    survive and reproduce

9
Evolution
  • The change in inherited characteristics of a
    population from generation to generation,
    eventually resulting in new species

10
The Theory of Natural Selection
  • On the Origin of Species, 1959
  • Explanation for why and how evolution occurs
  • Individuals with traits best suited to the local
    environment generally have more surviving
    offspring. This increases the representation of
    certain heritable variations in the next
    generations. This differential reproductive
    success is called natural selection.

11
Traits are Inherited, Not Acquired
12
Two Meanings of Evolution
  • Macroevolution
  • Origin of new species over vast periods of time
  • Microevolution
  • Genetic changes within a species over generations

13
How Fast Does Evolution Occur?
  • Organism-specific
  • Bacteria vs. Mammals
  • Punctuated Equilibruim
  • Gradualism

14
(No Transcript)
15
What is the Evidence for Evolution?
  • Observed Changes in traits in rapidly reproducing
    organisms
  • Aripo River system guppies (effects of predation
    and mate attraction)
  • Pathogen bacteria and viruses 9effect of
    drug-resisitance)
  • Fossils
  • Molecular BiologyDNA, Proteins
  • Anatomical Homologies

16
Fossils
  • Sedimentary rock burials
  • Radioisotopic dating

17
Fossils at different depths show successive
changes over time
18
Fossil Evidence Shows Cetaceans Evolved from
Terrestrial Animals
19
Molecular Biology
  • Broad genomic differences
  • Proteomic differences
  • Individual gene sequences

Hemoglobin ß chain amino acids
20
Anatomical Homologies
  • Embryology
  • All vertebrates share basic developmental
    instructions

21
Anatomical Homologies
  • Homologous structures
  • Vertebrates share like skeletons, body plans,
    organs from same origin

22
Convergent Evolution
  • Analogous structures
  • Unrelated organisms develop like adaptations due
    to similar environmental pressures

23
Convergent Evolution
24
How Do We Determine Species?
25
The Biological Species Concept
  • Species a group of organisms that can
    successfully interbreed in nature and produce
    fertile offspring
  • Requires reproductive isolation
  • What about…?
  • Dog wolf -gt wolf-hybrid (fertile)
  • Horse donkey -gt mule (infertile)
  • Tiger lion -gt liger (males infertile (?),
    females fertile, but health problems)
  • Other definitions of species?
  • Morphology, ecological niche, phylogeny

26
Evolution Commonly Occurs On Islands
27
Types of Reproductive Isolation
  • Prezygotic barriers
  • Habitat isolation (physical barriers)
  • Temporal isolation
  • Behavioral isolation
  • Mechanical isolation
  • Postzygotic barriers
  • Reduced developmental viability in first
    generation
  • Sterility of first generation
  • Feeble or sterile second generation offspring

28
Two Mechanisms of Speciation
  • Allopatric speciation
  • Geographic barrier separates gene pools, prevents
    interbreeding
  • Sympatric speciation
  • Less common
  • No geographic barrier
  • Chromomsomal mutations, genetic mutations
    enabling use of different resources, sexual
    selection
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