Evolution Unit Review

Evolution Unit

• AP Biology Notes by Jensen

Natural Selection

• Species produce more offspring than the environment can support.

• Only a fraction of an individual’s offspring may survive.

• Individuals best suited to the environment typically leave more offspring.

• There exists heritable variation among individuals.

• Even poorly adapted individuals may produce offspring under certain circumstances.

Upper Forelimb Structure

• Comparative anatomy of mammalian forelimbs shows equivalent limb bones in:

  • Human

  • Cat

  • Whale

  • Bat

• Limb transformations involve genetic mutations affecting gene-control proteins.

• Development is influenced by mutations that integrate body parts through control mechanisms during embryonic development.

Darwin’s Finches

• Approximately 13 finch species in the Galápagos are descendants of a common ancestor from South America.

• Four distinct lineages exist, classified into three genera:

  • Warbler finch (genus Certhidea)

  • Vegetarian finch (genus Camarhynchus)

  • Tree finches (genus Camarhynchus)

  • Ground finches (genus Geospiza)

• Ground finches have more recent evolutionary adaptations and are more genetically similar.

Genus Geospiza

• Ground finches are closely related to each other compared to tree finches.

Genus Camarhynchus

• A 1999 study found that the vegetarian finch is genetically comparable to ground finches and not necessarily closer to tree finches despite its classification.

Reading a Cladogram

• Horizontal axis represents a timeline (from 100,000 years ago to present).

• Vertical axis does not represent any specific data.

• Labelled branch points (V-Z) indicate common ancestors.

• Variation existed enough to separate lineages into distinct species approximately 50,000 years ago.

Common Ancestors

• Five common ancestors (labeled V-Z) led to both extant and extinct species.

Evolutionary Trees

• Evolutionary trees are hypotheses and are understood as such by scientists.

The Drought and Finch Survival

• Beak size affected survival of finches on Daphne Major during a prolonged drought.

• The depth and strength of beaks were critical for survival during the drought.

Heterozygous & Homozygous

• If average heterozygosity in a species' gene pool is 50%, the average homozygosity should also be 50%.

• Heterozygosity and homozygosity values sum to 100%.

Genetic Drift and Founder Effect

• Original finches arriving in the Galápagos may have had genetic differences from the South American population, illustrating genetic drift and the founder effect.

Star Trek Scenario

• In a hypothetical scenario with space colonists, calculations of allele frequency and use of Hardy-Weinberg equation will be taught.

• Free earlobes are dominant to attached earlobes.

Survival of the Fittest

• Natural selection affects allele frequencies as some individuals survive and reproduce more effectively than others.

Cetartiodactyla Clade

• Whales and hippos, previously classified in different orders, show genetic closeness leading to reevaluation of classifications into the clade Cetartiodactyla.

• Importance of molecular evidence and uncertainty in whether it should be order or superorder status discussed.

Shared Derived Character

• Vestigial pelvic girdle in modern cetaceans can indicate shared derived characters if lineage divergence timing supports that.

Species Definition

• A species is often described as the largest group of organisms capable of interbreeding and producing fertile offspring.

• Hybrid sterility can reduce gene flow between species.

Punctuated Equilibrium

• According to this model, new species rapidly accumulate unique features upon existence and remain relatively stable over time.

Geographical Isolation

• Differentiates between geographic isolation and habitat differentiation regarding speciation processes.

Autopolyploids

• Autopolyploids are derived from a single species and can arise from spontaneous genome doubling or fusion of unreduced gametes.