Theory of Evolution

1
Theory of Evolution

• Chapter 15
• Miss Colabelli

2
Idea of Evolution

• Charles Darwin (1809-1882)
• English naturalist
• Took a trip around the world on a ship called
  H.M.S. Beagle
• Mostly fascinated with the Galapagos Islands
• Best known for his theory of evolution by natural
  selection

3
Idea of Evolution

• Galapagos Islands
• Groups of animals vary from island to island
• Ex tortoises on each island resemble each other
  but differ in the shape and function of their
  shells
• Ex finches on each island resembled each other
  but differ in the shape and function of their
  beaks
• Darwin believed these unique animals all came
  from a common ancestor and they changed/adapted
  to their environment

4
Idea of Evolution

• Evolution
• Development of new types of organisms over time
• Heritable change in the characteristics within a
  population from one generation to the next

5
Ideas of Darwins Time

• Scientists thought all species were permanent and
  unchanging
• The Earth was believed to only be a few thousand
  (not billions) of years old
• Charles Lyell was a English geologist that
  believed the Earths surface continues to change
• Influenced Darwin

6
Ideas of Darwins Time

• Jean-Baptiste Lamarck
• French biologist that supported the idea that
  populations of organisms change over time
• Also believed in biogenesis of simple organisms
• Proposed that individuals acquire traits during
  lifetime from behavior and pass them onto
  offspring
• Called Theory of Acquired Traits

7
Darwins Ideas

• Around the same time Darwin and Wallace formed
  theory to explain evolution
• Published book On the Origin of Species in 1858
• Book explained how evolution occurs by means of
  natural selection

8
Descent with Modification

• Idea that every species must have descended by
  reproduction from pre-existing species that
  arrange over time
• Ex finch beaks at Galapagos

9
Natural Selection

• Mechanism from descent with modification
• 1. Overproduction
• More offspring are produced than survive to
  maturity

• 2. Genetic variation
• Traits vary within a species
• Ex deer fur thickness is passed on to future
  offspring

10
Natural Selection (contd)

• 3. Struggle to survive
• Organisms need to compete with each other known
  as struggle for existence
• When an organism is successful in a new
  environment its called an adaptation

• 4. Differential Reproduction
• Organisms best adapted for an environment will
  survive best and reproduce
• Survival of the fittest
• The ability for an organism to reproduce and pass
  on adaptations

11
The Fossil Record

• Fossils
• Remains of an organism that died long ago
• Some are remains of extinct organisms, meaning
  the species is no longer alive
• Superposition
• Idea that strata form in layers where the layers
  closest to the top are the younger than below

12
The Fossil Record

• Relative Age
• Age compared to other fossils in order of old to
  young
• Absolute Age
• Using radiometric dating to get actual number age
  

13
The Fossil Record

• Scientists use these relative and absolute ages
  to try and make the history of life on Earth as
  precise as possible
• Fossil records are incomplete history because not
  all organisms have left fossils behind
• Fossils can easily be destroyed during the
  process
• Finding fossils is rare also

14
Transitional Species

• We can infer that species have gradually changed
  based on the fossil record
• Scientists have hypothesized ancestors and later
  descendant species
• Organisms with features that are between
  hypothesized ancestors

15
Biogeography

• Study of locations of organisms around the world
• Darwin used this method when exploring islands
  and observed animals variation based on
  environment

16
Anatomy and Embryology

• Anatomy study of the body
• Embryology study of development
• Homologous structures
• Anatomical structures that originated by heredity
  from a structure in most common ancestor
• Ex bones in arms of humans, penguins, alligator
  and bat
• Related structure but function may differ

17
Anatomy and Embryology

• Analogous Structures
• When structures have similar function, but did
  not develop the same way
• Ex wings of bat vs. bird
• Vestigial Structures
• Organs that no longer serve a function in an
  organism
• Ex human tail bone, appendix

18
Phylogeny

• Relationships among groups of organisms
• Can make a tree of animals evolved
• Trunk of the tree would represent species that
  are closely related
• Branches represent a separate population or
  lineage

19
Caribbean Anole Lizard

• Found in the Caribbean islands of Cuba,
  Hispaniola, Jamaica, and Puerto Rico
• Each lizard species body type differs by their
  habitat
• Ex stocky body and long legged lizards are best
  adapted for tree truck environments, slender
  bodies and long tails are best adapted for grassy
  environments
• Hypothesis 1 An ancestral anole species
  specialized for living on twigs originally lived
  on one island and later migrated to other islands
  
• OR
• Hypothesis 2 Each twig-dwelling species evolved
  independently on each island from distant
  ancestor anole species

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Evolution in Action

• Biologists tested the hypothesis by comparing DNA
  from the various species
• DNA evidence supported hypothesis 2 that each
  lizard evolved independently on each island
• Convergent Evolution
• Process by which different species evolve
  similar traits
• Ex sugar glider of Australia and flying
  squirrel of North America came from different
  ancestors but evolved similar adaptations to
  their environment

21
Divergence Radiation

• Divergence evolution
• Process by which the descendants of a single
  ancestor diversify into species that each fit
  different parts of the environment
• Ex lizards with genes for large toe pads and
  short legs ran slowly on the tree trunks and fell
  easily to predators, lizards with long legs and
  small toe pads were able to slip away and
  reproduce

22
Divergence Radiation

• Adaptive Radiation
• Pattern of variation when a new population in a
  new environment undergoes divergent evolution

23
Artificial Selection

• Process the occurs when human breeders choose
  individuals that will parent the next generation
• Ex faster greyhounds, smaller tea cup dogs, high
  milk yield cows, high yielding grain per stalk
• Darwin hypothesized domesticated dogs diverged
  from wolves
• DNA evidence indicated similarities with wolves
  in East Asia, supporting Darwins hypothesis and
  humans selected domestic dogs from wolf
  population 15,000 years ago

24
Coevolution

• Evolution is on-going and many species may evolve
  together
• Coevolution
• When two or more species have evolved adaptations
  to each others influence
• Predator/Prey Interactions
• Introduction of new species
• Creating antibiotics