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Evolution. Ch 13. Historical Theories. Anaximander (~2500 yrs ago) Aristotle Georges Buffon (1700’s) Jean Baptist Lemark (late 1700’s - early1800’s) Erasmus Darwin. Charles Darwin. 1874. 1859. Voyage of the HMS Beagle. On the Origin of Species…. Descent With Modification

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historical theories
Historical Theories
  • Anaximander (~2500 yrs ago)
  • Aristotle
  • Georges Buffon (1700’s)
  • Jean Baptist Lemark (late 1700’s - early1800’s)
  • Erasmus Darwin
on the origin of species
On the Origin of Species…
  • Descent With Modification
  • By means of Natural Selection
support for descent with modification
Support for Descent with Modification
  • Biogeography
  • Fossil Record
  • Molecular Biology, Biochemistry, Cell Biology
  • Comparative Anatomy


  • Geographic distribution of species
    • Darwin noted that Galápagos animals resembled species of the South American mainland more than animals on similar but distant islands
    • Organisms may have common ancestor
fossil evidence


Fossil Evidence
  • Organisms evolved in a historical sequence

A Skull of Homoerectus

D Dinosaur tracks

B Petrified tree

C Ammonite casts

E Fossilized organicmatter of a leaf

G “Ice Man”

F Insect in amber

Figure 13.3A–G

fossil evidence9

Figure 13.3I


Fossil Evidence

Many fossils link early extinct species with species living today

comparative anatomy





Figure 13.4A


Comparative Anatomy
  • Comparison of body structures in different species
    • Homology- similar characteristics resulting from common ancestry
    • Homologous structures- features with different functions but structurally similar due to common ancestry
comparative embryology




Human embryo

Chick embryo

Figure 13.4B


Comparative Embryology
  • Comparison of early stages of development among different organisms
molecular biology

Table 13.4


Molecular Biology
  • Comparisons of DNA and amino acid sequences between different organisms to reveal evolutionary relationships
how did darwin come up with his ideas
How Did Darwin Come Up With His Ideas?
  • Scientific Method
  • Key observations
    • Traits vary in a population & most are inherited from parent to offspring
    • More offspring are produced than the environment can support (Thomas Malthus)
  • Limited resources
  • Overproduction of offspring
  • Heritable individual variation
    • Therefore, survival depends partly on inherited features
darwin s theory of evolution
Darwin’s Theory of Evolution
  • In a varied population, individuals whose inherited characters best adapt them to the environment are more likely to survive and reproduce.
  • Therefore, they tend to leave more offspring than less fit individuals.
  • Natural Selection is the mechanism
    • Reproduction (differential) is Key
observing natural selection

A flower mantidin Malaysia

A leaf mantid in Costa Rica

Figure 13.5A


Observing natural selection
  • Camouflage adaptations that evolved in different environments
pestacide resistance

Chromosome with geneconferring resistanceto pesticide

Pesticide application


Additionalapplications of thesame pesticide willbe less effective, andthe frequency ofresistant insects inthe populationwill grow

Figure 13.5B


Pestacide Resistance
antibiotic resistance


Antibiotic resistance
  • The excessive use of antibiotics is leading to the evolution of antibiotic-resistant bacteria

Colorized SEM 5,600

Figure 13.13

natural selection experiment
Natural Selection Experiment
  • Darwin Finches (Galapagos Finches)
  • Similar EXCEPT for beaks
    • Beaks = specialization
unit of evolution


Unit of Evolution
  • Evolution acts on individuals, affects whole populations
    • Populations are the unit of evolution
    • Group of individuals of the same species living in the same place at the same time
unit of evolution24
Unit of Evolution
  • Evolution is change in prevalence of heritable traits in population
  • A gene pool
    • Is the total collection of genes in a population at any one time
  • Microevolution
    • Is a change in the relative frequencies of alleles in a gene pool
hardy weinberg equilibrium
Hardy-Weinberg Equilibrium
  • Frequency of alleles in a stable population will not change over time
    • Very large population
    • Population is isolated
    • Mutations don’t alter gene pool
    • Random mating
    • All individuals are equal in reproductive success
  • In reality, this never happens
agents of change
Agents of Change
  • Genetic Drift
    • Bottle neck affect
    • Founder affect
  • Gene Flow
  • Mutation
  • Non Random Mating
  • Natural Selection

Figure 13.11


  • Extensive in most populations
  • Mutation and sexual recombination generate variation and can create new alleles.
endangered species often have reduced variation


Endangered species often have reduced variation
  • Low genetic variability
      • May reduce the capacity of endangered species to survive as humans continue to alter the environment

Figure 13.10

sexual selection
Sexual Selection
  • Sexual Dimorphism
  • Sexual Selection- where individuals with certain characteristics are more likely to obtain mates than others.
    • Intrasexual selection
    • Intersexual selection
  • Heterozygote advantage
  • Balancing selection
  • Frequency-dependent selection
natural selection is limited
Natural Selection is Limited
  • Only act on existing variation
  • Historical constraints
  • Compromise
  • Change, selection and the environment