Biology Week 15: Evolution

Week 15: Evolution

• Evolution is the cumulative change in a population of organisms over time.

Objectives

• Describe how natural selection leads to evolution.
• Describe evidence of evolution.
• Explain how populations change over time, showing patterns of descent and modification from common ancestors.
• Describe how the current classification system is based on evolutionary relationships.

What is Evolution?

• On the Origin of Species by Means of Natural Selection, by Charles Darwin:
  • All species on Earth are products of descent with modification.
  • Natural selection is the mechanism for descent with modification.

Evidences of Evolution

• Fossil Records:

  • Provide direct evidence of organisms' appearances and lifestyles.
  • Fossils found in sedimentary rock layers.
  • Specific layers contain fossils from certain periods.
  • Reveal how organisms evolved in their environments.

• Geographic Distribution:

  • Organisms' evolution can be tracked through their geographic distribution.
  • Pangaea's breakup caused species separation and then distribution to different continents, showing evolutionary relationships and patterns.

• Comparative Anatomy

  • The study of similarities and differences in structures.
  • Homologous structures: Organs with different functions, but with similar structures (e.g., limbs in bats, whales, cats, and humans). Show common ancestry.

• Common Traits in Embryo:

  • Similarity in embryonic development of vertebrates (fish, birds, mammals, and amphibians).
  • Shared ancestry reflected in embryonic features.

• Genetic Changes

  • DNA shared among different mammal species shows varying degrees of similarity reflecting evolutionary relationships (e.g. dogs, cats, elephants, chimps).

How Evolution Works

• Divergent Evolution:

  • Closely related species develop new habitats and lifestyles, producing distinct species.
  • Example: Elephants and mammoths.

• Convergent Evolution:

  • Distantly related lineages evolve similar structures as adaptations to similar environments or life styles.
  • Example: Flying squirrels and sugar gliders.

• Adaptive Radiation:

  • Ancestral species invade a new territory with no competitors.
  • Exploit environment and occupy different niches.
  • Leads to diversification and speciation in the new territory.
  • Example: Darwin's finches.

• Coevolution:

  • Observed in predator-prey relationships, and mutualism.
  • Two or more species affect each other's survival and evolution.
  • Example: Ants and trees in nectar relationships.

Pace of Evolution

• Phyletic Gradualism:

  • Continuous, slow change over long periods.

• Punctuated Equilibrium:

  • Rapid bursts of change followed by periods of no change.

Classification Based on Evolutionary History

• Phylogenetic systematics: Identifies evolutionary relationships between organisms.
  • Living and extinct organisms.
• Charles Darwin drawing of the Tree of Life.
• Phylogenetic Tree of Life: A visual representation of evolutionary relationships.
  • Organisms are grouped together based on their shared ancestry.
  • Examples of kingdoms – Protista , Monerans, Fungi, Plants, and Animals.

This quiz explores the concept of evolution, highlighting how natural selection drives change in populations over time. Participants will examine evidence of evolution through fossil records and geographic distribution. Furthermore, the quiz delves into the current classification system rooted in evolutionary relationships.