Evolution Test Review

Part I: Natural Selection

• Evolution: The process of change by which an organism or species becomes better suited to its environment.
• Natural Selection: "Survival of the fittest," a mechanism of evolution.
• Adaptation: N/A
• Fitness: An organism's ability to survive and reproduce.
• Competition: An interaction between organisms or species in which both require a resource that is in limited supply (such as food, water, or territory).

Peppered Moth Example

• Industrial Revolution Impact: Pollution darkened trees, changing the selective pressure.
• Pre-Industrial Revolution: Light moths were more common because they blended into the light-colored trees, providing camouflage from predators.
• Post-Industrial Revolution: Dark moths became more common as they blended into the polluted, darker trees, gaining a survival advantage.
• Selective Pressure: Predators acted as the selective pressure in the ecosystem.

Types of Selection

• Directional Selection: Favors one extreme phenotype.
• Disruptive Selection: Favors both extremes.
• Stabilizing Selection: Favors the average phenotype (middle, most common) - stable.
• Artificial Selection: Selection by humans for breeding useful traits from the natural variation among different organisms.

Graphs of Selection

• Stabilizing: average
• Directional: one extreme
• Disruptive: both extremes

Significance of Disruptive Selection

• Disruptive selection is most likely to lead to speciation.

Four Principles of Natural Selection

1. Variation in phenotypes
2. Heritable
3. Struggle for existence
4. Reproduction and survival rates

Part II: Evidences of Evolution

Evidences of Evolution

1. Comparative anatomy
2. Biogeography
3. Fossils
4. Embryology
5. Biochemistry/DNA

Matching Evidence Descriptions

• Comparative Anatomy: Structures of different species reveals similarities and differences that indicate shared ancestry or evolutionary relationships.
• Biogeography: Changes in geographical features explain fossil species distribution.
• Fossils: Show the gradual change of physical structures over time.
• Comparative Embryology: Similarities in development across organisms show how they may be related
• Comparative Biochemistry (DNA): Sequencing the genetic material (genome) of different species shows how closely they are related

Structure Definitions

• Homologous: Structures that are similar in shape amongst related species, but do not serve the same purpose or function, but can show links to a common ancestor.
• Analogous: Body parts in different species that have similar functions but evolved separately, meaning they do not come from a common ancestor and do not share similar structures.
• Vestigial: Inherited from a common ancestor but serve no actual purpose in the present-day species. Useless or not needed structures.

Examples of Structures

• Homologous Structures: Same structure-diff. function (e.g., human, cat, whale, bat arm bones).
• Analogous Structures: Same function, different structure.
• Vestigial Structures: vestigial pelvic bone; not needed.

DNA Similarity

• Species are ranked based on % similarity to species M to determine recency of common ancestor.
• Most Common Ancestor to Least Common Ancestor: Y (92%), W (87%), Z(37%), X (16%)

Part III: Rates, Patterns, and Processes of Evolution

Definitions

• Adaptive Radiation: When a single or small group of ancestral species rapidly diversifies into a large number of descendant species.
• Divergent Evolution: Homologous structures are structures indicating a species is breaking away from its ancestor.
• Convergent Evolution: Refers to the evolution in different lineages of structures that are similar or 'analogous', but that cannot be attributed to the existence of a common ancestor.
• Coevolution: Cases where two (or more) species reciprocally affect each other's evolution.
• Gradualism: Shows slow, steady change within a population over time.
• Punctuated Equilibrium: Rapid change in population of organisms followed by periods of slow or no change

Types of Evolution

• Divergent Evolution: common ancestor, branch off.
• Convergent Evolution: no common ancestor, come together.
• Coevolution: Together

Characteristics of Convergent and Divergent Evolution

• Both: May occur through natural selection
• Divergent: Common ancestor, Produce homologous structures, Species appearance becomes more different over time, Species are closely related (share genetic homology)
• Convergent: Different ancestor, Produce analogous structures, Species appearance becomes more similar over time, Species are genetically different (unrelated).

Examples of Evolutionary Scenarios

• Coevolution: The acacia tree evolved structures (hollow thorns, nectar glands, Beltian bodies) specifically adapted to attract and support ants. In turn, the ants evolved behaviors and physiological traits (such as aggression toward intruders and the ability to digest plant-based food bodies) that benefit the acacia trees.
• Convergent: In the ocean surrounding Antarctica, there are fish that survive the cold water by using a molecule made of glycoproteins that circulates the blood and keeps it from freezing. Certain kinds of worms that live in the Arctic ocean also make antifreeze proteins that help them live in icy water.
• Divergent: The Gallotia atlantica and Gallotia galloti lizards evolved through natural selection from a common ancestor into a wide variety of different looking lizards.

Phylogenetic Trees

• Phylogenetic Tree Components: Tips, Branch (external), Branch (internal), Nodes, Root
• Relationship Determination: Species A and B are more closely related than species B and C because they share a more recent common ancestor.

Traits Shared on a Phylogenetic Tree

• Based on the provided vertebrate phylogenetic tree, all organisms share the trait of vertebrae.

Part IV: Population Genetics

Definitions

• Genetic Drift: Change in the allele frequency of a population due to random chance.
• Gene Flow/Migration: Movement of alleles into or out of a population due to migration.
• Population: A group of similar organisms that can breed and produce fertile offspring.
• Bottleneck Effect: Population is drastically reduced to a very low number and then rebounds.
• Founder Effect: Accounts for large genetic variations in isolated populations, an extreme example of genetic drift. Colonizers

Identifying Effects

• Image A: Bottleneck Effect
• Image B: Founder's Effect

Diversity after Population Reduction

• Following a virus that killed most of the seals, starting a new population with a small number of seals (20) would result in the new population being less diverse than the original population.