EvolutionSpeciesBb (1)

Natural Selection

  • Variation Exists

    • Variation among individuals in a population is crucial for natural selection.

  • Early Death Happens

    • Early mortality affects which individuals survive to reproduce.

  • Impact of Variation

    • The variations can determine survival and reproductive success.

Importance of Darwin’s Idea

  • Lasting Relevance

    • Darwin’s theories help understand complex natural phenomena.

  • Explaining Bizarre Aspects of Nature

    • Natural selection clarifies seemingly odd biological occurrences.

  • Testing Hypotheses

    • It allows scientists to form and test hypotheses.

Microevolution

  • Well-Studied Examples

    • Microevolution refers to small evolutionary changes within species.

  • Experimental Testing Easiness

    • Microevolutionary processes can often be tested scientifically.

  • Consensus on Existence

    • Generally, there is little debate on microevolution's occurrence, though details are debated.

Microevolution vs. Macroevolution

  • Microevolution

    • Describes changes within species and the formation of new, similar species.

  • Macroevolution

    • Pertains to broader evolutionary changes leading to new types of organisms.

Timescales of Macroevolution

  • Duration

    • Macroevolution lasts over extensive geological time frames.

The Age of the Earth

  • Estimated Age

    • Approximately 4.6 billion years.

  • Evidence for Age

    • Oldest rocks: ~4.03 billion years old

    • Oldest minerals: 4.4+ billion years

    • Meteorite Dating: 4.5+ billion years

    • Oldest lunar rocks: 4.4 - 4.5 billion years

Evolution of Life on Earth

  • Oldest Fossils

    • Fossils date back to ~3.5 billion years ago, found near James River, TX.

Stromatolites

  • Example of Early Life

    • Stromatolites are significant in studying ancient biological activity.

Challenges in Studying Macroevolution

  • Long Timeframes

    • Evidence arises without direct experimentation, making it complex.

Evolution of the Eye

  • Debate on Eye Complexity

    • Some argue complicated structures like the eye cannot evolve through natural selection.

  • Investigating Eye Evolution

    • Examination of steps leading to ocular development.

Evolution of Eye Structures

  • Progression of Eye Complexity:

    • Light-sensitive cells → Eye cups → Camera-type eyes.

    • Development stages from simple to complex structures are noted.

Fish-to-Tetrapod Evolution

  • Transitional Fossils

    • Tiktaalik and Ichthyostega represent critical transitional forms in fish-to-tetrapod evolution.

  • Significance of Features

    • Combination of fish features alongside tetrapod limb adaptations.

Characteristics of Transitional Fossils

  • Key Features of Early Tetrapods:

    • Lungs, mobile neck, rib bones, and other derived characteristics indicating advancements from fish.

Definition of Species

  • Basic Definition

    • Species are organisms capable of interbreeding and producing fertile offspring.

  • Hybridization

    • Hybrids can occur but are often infertile, with chromosome differences causing reproductive limitations.

Genetic Variation in Species

  • Chromosomal Diversity

    • Example comparisons among gray treefrogs and other species.

Understanding Species Populations

  • Population Dynamics

    • Populations can vary significantly in size, density, and structure.

Organization of Life

  • Hierarchical Structure

    • From atoms to molecules, through cells and organisms, up to ecosystems.

Population Pyramids

  • Understanding Population Demographics

    • Comparison of age pyramids for populations in Canada and Madagascar in 2005, illustrating demographic trends.