Introduction to Evolution

In-class interactive lecture on evolution that covers the principles and mechanisms driving evolutionary change and adaptation in species over time.

Constructing a Phylogenetic Tree

• Use an attribute table to build a phylogenetic tree based on three lines of evidence:

  • Observations of habitat and eating habits: Examining where species live and what they eat can provide initial clues about their evolutionary relationships.

  • Observations of skeletons: Analyzing skeletal structures exposes similarities among species that can indicate common ancestry.

  • Observations of gene sequences: Genetic comparisons allow us to determine how closely related different species are at the molecular level.

• Update the phylogenetic tree after each observation to reflect new insights.

Species Overview

1. Black Bear

   • Scientific Name: Ursus americanus

   • Habitat: Terrestrial, typically found in forests and mountainous areas.

   • Diet: Omnivore, consuming a varied diet of plants, insects, and small animals.

2. Harp Seal

   • Scientific Name: Phoca groenlandica

   • Habitat: Aquatic & Terrestrial, often found in ice-covered regions of the North Atlantic.

   • Diet: Carnivore, primarily feeding on fish and invertebrates.

3. Hippopotamus

   • Scientific Name: Hippopotamus amphibius

   • Habitat: Terrestrial & Aquatic, spending a lot of time in water to keep cool.

   • Diet: Herbivore, mainly grazing on grasses during the night.

4. Sea Otter

   • Scientific Name: Enhydra lutris

   • Habitat: Aquatic, primarily inhabiting coastal areas in the northern Pacific Ocean.

   • Diet: Carnivore, feeding on marine invertebrates such as sea urchins and crabs.

5. King Penguin

   • Scientific Name: Aptenodytes patagonicus

   • Habitat: Aquatic & Terrestrial, found on islands in the Southern Ocean.

   • Diet: Carnivore, primarily feeding on fish and squid.

6. Harbor Porpoise

   • Scientific Name: Phocoena phocoena

   • Habitat: Aquatic, residing in coastal waters of the North Atlantic and Pacific.

   • Diet: Carnivore, mainly consuming fish and squid.

7. Blue Whale

   • Scientific Name: Balaenoptera musculus

   • Habitat: Aquatic, found in oceans serving extensive migratory patterns.

   • Diet: Omnivore, primarily feeding on krill and small fish.

Drawing a Phylogenetic Tree

• Example to illustrate tree based on diet & habitat. Include species with respective classification (genus, family, order) to highlight their evolutionary relationships.

Evidence from Skeletons

• Skeletons reveal strong evidence of common ancestry among vertebrates, highlighting evolutionary trajectories of various species.

• Includes living species and fossils of extinct species. Transitional fossils provide insights into evolutionary processes; for example, Ichthyostega demonstrates amphibians' descent from fish through features like limbs adapted for life on land.

Reptile to Mammal Transition

• Fossil record documents features indicative of transitions, e.g., jaw joint, teeth, neck ribs, signifying the gradual changes over time.

• Example fossil: Lycaenops, a carnivorous therapsid that showcases important anatomical features in the evolution of mammals.

Vestigial Structures

• Vestigial bones indicate common ancestry; examples include the pelvic girdle in snakes and the tailbone in humans, remnants of structures that had functional roles in ancestors but are now diminished in modern species.

• Vestigial pelvic bones in whales indicate evolutionary history from land-dwelling, ancestral mammals.

Homologous Structures

• Homologous features show common ancestry among mammals. These structures share a common pattern, indicating derived ancestry, e.g., forelimbs of whales, bats, and humans have similar underlying bone structures despite different functions.

Conclusion

• All mammals share a common ancestor evidenced by both fossil records and genetic studies. This underscores the unity of life and the evolutionary processes shaping diverse forms of life today.

Molecular Biology Evidence

• A universal genetic code across all living organisms suggests common ancestry. Comparison of DNA enhances understanding of evolutionary relationships among species.

Genetic Homologies

• Percentage of genes from other organisms that are also found in Homo sapiens:

  • Mouse: 86%

  • Fruit fly: 44%

  • Nematode worm: 25%

  • Yeast: 30%

  • Amoeba: 22%

  • Mustard plant: 19%

  • E. coli: 9%

Hemoglobin and Common Ancestry

• Hb gene widely distributed in various species suggests a common ancestor existed billions of years ago. Molecular biology enables scientists to estimate dates for common ancestry based on hemoglobin mutation rates, revealing the evolutionary connection among diverse organisms.

Drawing Phylogenetic Trees with Molecular Evidence

• Evolutionary relationships are depicted by similarity in DNA and protein sequences. Close matches in genetic material indicate recent common ancestry among species, providing a quantitative approach to understanding evolutionary connections.

Phylogenetic Tree Based on DNA Sequences

• Closely related species share similarities in DNA and proteins inherited from common ancestors, enhancing the understanding of their evolutionary pathways.

Hippo-Whale Relationship

• Recent findings suggest hippos and whales share a close evolutionary relationship; DNA analysis supports this connection, which is further substantiated by fossil evidence. The discovery of 47 million-year-old proto-whale fossils solidifies the theory, and unique ankle bone features connect hippos and proto-whales, illustrating their shared history.

Transitional Fossils

• Discovery of transitional fossils showing whale ancestors had legs, such as Ambulocetus, known as the walking whale, further provides evidence of the evolutionary transition from land to water adaptations in cetaceans.