Reproduction and Evolution

This section compares sexual and asexual reproduction methods and their implications for evolution.

Sexual reproduction involves:

• Two parents (male and female)
• Genetically different offspring
• Meiosis, resulting in new combinations of alleles
• Generally fewer offspring at a time
• Improved chances of survival due to increased variation

Asexual reproduction involves:

• One parent
• Genetically identical offspring
• Methods such as budding, fragmentation, and vegetative propagation
• Production of many individuals at one time

Highlight: Sexual reproduction generally leads to more variation, which improves an individual's chance of survival in changing environments.

The text then defines biological evolution as the analysis of how heritable traits change in frequency within a population over time. This includes physical traits, molecular sequences, and behavioral traits.

Vocabulary:

• Microevolution: Evolution within a single population over a short period of time
• Macroevolution: When small changes accumulate over a long period, producing noticeable changes in species

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.