Chapter 22 Notes: Descent with Modification

Root Words

  • evo-: "Period", "age" - Latin
    • Evolution: to stem from a period or age.
  • ana-: "Against" “back” “Up” - Greek
    • Anarchy: without/against rule
  • homo - “The same” Greek
    • Homosexual: sexual preference to the same sex
    • Homologous: having the same position or structure

Overview

  • Evolution explains life changes over time, supported by:
    • Fossil record
    • Comparative anatomy
    • Embryology
    • Biochemistry
    • Biogeography

Fossil Record

  • Rock layers (sediments) form over time, preserving traces of organisms like fossils, imprints, remains, and skeletons.
  • Paleontologists analyze these to compare organisms across layers/years.
  • Fossils show ancient species' similarities to current ones.
  • Problem: soft tissues decay, tectonic plates shift, causing damage and incomplete records.

Comparative Anatomy

  • Homologous structures: Anatomically similar structures inherited from common ancestor.
  • Vestigial organs: Serve no useful function (e.g., human appendix).

Embryology

  • Vertebrate embryos share homologous structures early on, diverging later.
  • Embryo: earliest stage of growth and development of both plants and animals.
  • Shared embryonic features suggest common ancestry.

Biochemistry

  • Molecular and genetic evidence supports evolution. Comparing Cytochrome Sequences Among Species
  • Closely related organisms share similar DNA.
  • Molecular data (genes, proteins) is best for comparing organism relatedness.

Biogeography

  • Studies plant/animal distribution to track species migration.
  • Pangaea explains migration over seas.

Evolutionary Theory

  • Evolution: change over time; modern organisms descend from ancient ones.
  • Scientific theory: well-supported, testable explanation of natural phenomena.

Darwin’s Theory of Evolution - Summary

  • Individuals vary; variation is heritable.
  • More offspring are produced than can survive, leading to competition for resources.
  • Advantages & disadvantages leads to survival and reproduction.
  • Natural selection causes species to change over time.
  • Species descend with modification from ancestors, uniting all life.

Darwin’s Journey

  • Darwin was a naturalist on the HMS Beagle, collecting biological and geological specimens.

Darwin in the Galapagos

  • Collected mockingbirds, finches, etc., noting variations across islands.
  • Specimens were new to European scientists.
  • Populations changed after reaching the Galápagos.

Darwin's Hypotheses

  • New species arise gradually via small changes.
  • Artificial selection (human-selected variations) mirrors natural processes.

Key Terms

  • Struggle for existence: competition for resources.
  • Fitness: ability to survive and reproduce.
  • Adaptation: inherited trait aiding survival.
  • Survival of the fittest: successful individuals survive and reproduce.
  • Descent with modification: species evolve with changes from ancestors.
  • Common descent: all species from common ancestors.

Darwin’s Theory of Natural Selection

  • Natural selection: mechanism for population change due to favorable variations.
  • Organisms with favorable variations survive, reproduce; pass traits.
  • Published in "On the Origin of Species" (1859).

Darwin’s Theory of Natural Selection - core principles

  • Individuals vary.
  • Variations are inherited.
  • More offspring than resources allow.
  • Beneficial variations are more likely to be passed on.

Theory of Evolution by Natural Selection - Key aspects

  • Overproduction: species produce more offspring than can survive.
  • Variation: individuals in a population differ.
  • Selection: some survive/reproduce more.
  • Adaptation: traits of survivors become common.

Outcomes of Natural Selection

  • Natural selection changes inherited traits over time, increasing the population's fitness.