Darwin's Observations and Finches

This section focuses on Charles Darwin's contributions to evolutionary theory.

Quote: "Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms." - Charles Darwin

The text mentions Darwin's seminal work, "Origin of Species," and his observations on the Galapagos Islands. It particularly highlights Darwin's finches as a key example of adaptation.

Example: The finches on different Galapagos Islands were similar to mainland finches but had adapted to the specific food sources available on each island.

The document includes an illustration showing different finch species with beaks adapted to various food sources, such as seeds, cactus fruits, buds, and insects.

Evidence for Evolution

This section introduces various fields of study that provide evidence for evolution:

1. Anatomy
2. Embryology
3. Biochemistry
4. Paleontology

The field of anatomy is explored in detail. It explains how organisms that have diverged from a common ancestor often have homologous structures, which are similar characteristics resulting from common ancestry.

Definition: Homologous structures are similar characteristics in different species resulting from common ancestry.

The text also introduces the concept of vestigial organs, which are structures with little or no important functions in an organism but were likely functional in ancestral species.

Example: Vestigial structures include the human tailbone, wisdom teeth, and pelvic bones in baleen whales.

The document distinguishes between homologous and analogous structures. Analogous structures are similar in function but not necessarily in structure and do not indicate shared ancestry.

Example: The wings of butterflies and birds are analogous structures, as they serve similar functions but evolved independently.

Anatomical Evidence for Evolution

This section provides detailed examples and illustrations of homologous, analogous, and vestigial structures as evidence for evolution.

Homologous structures are exemplified by the pentadactyl limbs found in various vertebrates:

• Human arm
• Cat leg
• Whale flipper
• Bat wing

These structures, despite their different functions, share a common basic structure due to their shared evolutionary history.

Analogous structures are illustrated with streamlined appendages in different aquatic animals:

• Dolphin flipper
• Shark fin
• Penguin wing

These structures evolved independently in response to similar environmental pressures, demonstrating convergent evolution.

Vocabulary: Convergent evolution occurs when unrelated species develop similar traits in response to similar environmental pressures.

The text provides a comprehensive list of vestigial structures in various organisms:

• Remnants of pelvis and hind limbs in snakes
• Hind legs in whales
• Wings on many flightless birds
• Erector pili (goose bumps) in humans
• Body hair in humans
• Human tailbone
• Wisdom teeth
• Male breast tissue and nipples
• Appendix in humans

Highlight: Vestigial structures provide strong evidence for evolution as they show structural changes over time in response to changing environmental pressures and functional needs.