Biology Chapter: Adaptations and Variations

Adaptations

• Adaptations are traits that enhance survival and reproduction.
• Biochemical/Body Processes: Internal adaptations like fish producing antifreeze proteins for cold water survival.
• Structural Adaptations: Physical traits like polar bear fur for insulation.
• Behavioral Adaptations: Actions like bird migration for warmer temperatures.
• Examples: Camouflage, hibernation, sharp talons/teeth, good eyesight.

Variations

• Variations are differences in traits within a species (size, color, behavior).
• Cause of Variations: Mixing of parental genes during meiosis results in unique offspring.
• Mutations: Permanent DNA sequence changes.
• Examples of Mutations: Tay-Sachs (nerve cell damage), Huntington's (brain cell death), Cystic Fibrosis (lung/pancreas problems).

Natural Selection

• Natural selection is how populations change due to survival of individuals with beneficial traits.
• Requirements:
• Variation in traits within a population.
• Selective pressure (environment favoring certain traits).
• Heritable traits (passed to offspring).

Evidence for Evolution

• Fossils: Provide evidence of species change over time; simpler organisms appear earlier, more complex later, not all species appear at once.
• Chronological Order: Fossils in younger layers show more recent species.
• Geographic Distribution: Similar species often found in similar geographic areas (evolved after continental separation).
• Anatomy:
• Homologous Structures: Similar structure, different function (e.g., bat, whale, cat forelimbs), indicating common ancestry.
• Analogous Structures: Different structure, similar function (e.g., bird, bat wings), not indicating common ancestry..
• Vestigial Structures: Structures with reduced or lost function (e.g., human appendix, whale hip bones).
• Transitional Fossils: Fossils showing intermediate stages in evolutionary change.

Lamarck

• Lamarck proposed a theory of evolution where acquired traits are inherited.
• Example: a giraffe stretching its neck becomes longer in order to survive, and passes this longer neck on.

Darwin

• Darwin's theory of evolution by natural selection:
• Species change over time because individuals with beneficial traits reproduce more successfully and pass these traits on.
• Darwin's work is based on observations made during his voyage on the HMS Beagle.

Speciation

• Speciation is the formation of new species.

• Types:

• Transformation: One species changing completely into a new species.

• Divergence: One species splitting into two or more.

• For speciation to occur: Populations need to be reproductively isolated to prevent gene flow.

• Types of Isolation:

• Geographical: Physical barriers preventing interbreeding (mountains, rivers, oceans).

• Biological: Internal/behavioral factors preventing interbreeding in the same geography.

• Behavioral isolation: differences in mating behaviors.

• Habitat isolation: Different habitats even in the same place

• Temporal Isolation: Reproductive periods differ.

• Mechanical Isolation: Incompatibility of reproductive structures.

• Gametic Isolation: Incompatibility of sperm and egg.

• Adaptive Radiation: Rapid evolution of many species from a single ancestor (e.g. Darwin's Finches).

Pace of Evolution

• Punctuated Equilibrium: Evolution occurs in rapid bursts followed by long periods of little change.
• Gradualism: Evolution happens slowly and steadily.