Evolution and Biodiversity

1
Evolution and Biodiversity

• The origin, adaptation, and extinction of life on
  Earth

2
Origins of Life

• Abiogenesis theory of the origin of life
• Chemical evolution in the primordial soup
• Oparin, Miller, Fox, and others
• Biological evolution began in the oceans
• The possible impact of cosmogenesis
• The fundamental role of evolution by natural
  selection

3
Evolutionary Processes

• All species evolve from earlier, ancestral
  species.
• Evolution causes changes in the gene pool of a
  population due to genetic mutations.
• Individuals with greater fitness pass more of
  their genes to the next generation.
• Natural selection exists in three forms
  directional, stabilizing, diversifying (or
  disruptive).
• Coevolution is when two species interact so
  intimately over time that changes in one
  population can lead to changes in the other.

4
Microevolution

• Genetic variability in a population
• Traits are passed on to offspring.
• Natural selection exerts a selective pressure on
  individuals.
• Those individuals with the trait are more
  successful at reproduction.
• Over time the proportion of individuals with the
  trait increases.

5
The case of the Peppered Mothan example of
evolution by natural selection

• http//www.biologycorner.com/worksheets/pepperedmo
  th.html

6
Macroevolution

• Formation of new species speciation
• Geographic and/or reproductive isolation
• Genetic divergence of the populations
• Adaptive radiation
• speciation of a single species to fill many
  niches.
• Extinction
• A species can no longer reproduce successfully
  due to changes in its environment
• Continental drift, climate change, catastrophe
• Human impacts

7
Evidence of Evolution

• The fossil record
• Favors organisms with hard body parts (shells and
  bones)
• Favors organisms in certain environments
  (alluvial plains and certain deserts)
• Anatomical similarities
• Molecular evidence DNA sequences
• Bacterial resistance to drugs and insect
  resistance to pesticides

8
A Brief History of Life on Earth

• The Geologic Time Scale
• Hadean Time
• Archaean Era - 1st life about 3.8 B years ago
• Proterozoic beginnings of life as we know it
• Paleozoic an explosion of life and a great mass
  extinction
• Mesozoic the age of dinosaurs
• Cenozoic life since the last great extinction
• An age of mammals or an age of flowering
  plants
• The recent arrival of humans and their impacts

9
Mass Extinction Events

• Mass extinction refers to a single event that
  causes the extinction of species at a rate much
  higher than the background rate.
• Mass extinctions (or the slightly less severe
  mass depletions) have occurred five times in
  geologic history.
• Human impacts are often considered to be causing
  a sixth mass extinction.

10
Speciation Extinction Biodiversity

• The sum of all of the species of life existing on
  Earth is global biodiversity.
• Types
• Genetic diversity
• Species diversity
• Ecosystem diversity
• Estimates of number of species vary but a general
  agreement might be about 10 million, of which
  about 1.5 million have already been described.