Chapter_22-student-part 2

Chapter Overview

• Campbell: Biology Twelfth Edition Chapter 22

• Topic: Descent with Modification

• Focus on evolutionary theory and its supporting evidence.

Learning Objectives

• Types of Evolution Evidence (22.3):

  • Provide examples supporting evolution.

  • Address common misconceptions related to evolution.

Concept 22.3: Theory of Evolution by Natural Selection

• Definition of a Theory:

  • A theory in science is more robust and supported by extensive evidence compared to a hypothesis.

Evidence Supporting Evolution

• Types of Data Supporting Evolution:

  • Direct Observations: Documented examples of evolution happening.

  • Field and Lab Studies: Research conducted in various environments.

  • Homology: Anatomical and genetic similarities among species.

  • Fossil Record: Historical documentation of species and their evolution.

  • Biogeography: Study of species distribution and its implications for evolution.

The Evolution of Drug-Resistant Bacteria

• Staphylococcus aureus: Common bacterium with a concerning strain known as MRSA (Methicillin-resistant Staphylococcus aureus).

• Evolution Timeframe:

  • Bacteria can evolve resistance in as little as 2-4 years to antibiotics.

  • Penicillin Resistance: Emerged in 1945.

  • Methicillin Resistance: Emerged in 1961.

Mechanism of Evolutionary Change

• Key Components:

  • Variation: Presence of differences in traits within a population.

  • Heritability: Ability of traits to be passed from parents to offspring.

  • Differential Reproductive Success: Organisms with advantageous traits are more likely to survive and reproduce.

• Natural Selection:

  • Operates at the individual level, leading to population-level evolution.

Mechanism of Antibiotic Resistance

• Action of Methicillin: Inhibits enzymes for cell wall production.

• MRSA Mutation: Allows access to an alternate enzyme pathway; thus, MRSA survives despite the presence of methicillin.

• Spread of Resistance: Evolving faster than new antibiotic discoveries.

Homology as Evidence of Evolution

• Definition of Homology: Similarity due to shared ancestry.

• Types of Homology:

  • Comparative Anatomy: Anatomical resemblances in closely related species.

  • Comparative Embryology: Similarities in embryonic development.

  • Comparative Genomics: Genetic similarities across species.

Comparative Anatomy

• Homologous Structures:

  • Present in different species indicating a common ancestor (e.g., mammal arm bones).

• Examples:

  • Arm bones in humans, cats, whales, and bats.

Comparative Embryology

• Similarities in Embryos:

  • Vertebrate embryos show common features (e.g., pharyngeal arches, post-anal tails).

Molecular Homologies

• Molecular Evidence:

  • Similar genes indicating a common ancestor among diverse species.

  • Genetic sequence alignment reveals evolutionary relationships.

Analogy vs. Homology

• Differences:

  • Homology: Similar traits due to shared ancestry.

  • Analogy: Similar traits that evolved independently (convergent evolution).

The Fossil Record as Evidence of Evolution

• Fossil Record Insights: Evidence of extinction, origins of species, and transitional forms.

• Example: Transition from land mammals to cetaceans (whales and dolphins).

Fossil Evolution Timeline

• Cetacean Evolution: Emerged from land mammals about 65 million years ago

• Intermediate Species: Illustrate gradual transition in body structure and behavior.

Biogeography as Evidence of Evolution

• Definition: Study of species distribution across geographical areas.

• Continental Drift: Understanding of past continent formations like Pangaea aids in studying species evolution.

Endemic Species

• Definition: Species unique to a specific geographic area.

• Example: Galàpagos finches closely related to mainland birds.

Misconceptions About Evolution

• Common misconceptions include:

  • Evolution occurs in individuals;

  • Evolution has a specific goal;

  • Organisms evolve to become more complex;

  • Natural selection is the only mechanism;

  • Organisms evolve features because they need them.