Evolution and Natural Selection

• Evolution is the genetic change in species over generations, leading to new species, suggesting all organisms evolved from pre-existing ones.

Jean-Baptiste Lamarck

• Proposed in 1809 that organisms change themselves over generations to meet their needs, acquiring survival characteristics passed to offspring.
• Each generation would continue the process until a species trait evolved.

Charles Darwin

• Developed the theory of natural selection based on observations.
• Organisms produce more offspring than survive.
• Populations remain relatively constant.
• Species members show varied characteristics.
• Some characteristics are inherited.
• Darwin deduced that all organisms engage in a struggle for survival where only the best adapted survive.
• Surviving organisms reproduce and pass useful adaptations to offspring.
• Variation in species leads to trait differences.
• Through natural selection, advantageous traits are passed on, evolving the species over time.

Survival Of The Fittest

• Individuals best adapted to their environment reproduce, passing on useful adaptations.
• Less adapted individuals do not survive long enough to breed.
• These ideas form the basis of Darwin’s theory of evolution by natural selection.
• Selection pressures are external factors affecting an organism’s survival ability in a given environment.

Variation

• Describes naturally occurring differences among individuals of a species.
• Permits flexibility, ensuring survival of a population in changing environments.
• Genetic variation is advantageous.
• Individuals show a range of phenotypes (physical characteristics).
• Variation is caused by genetics and environment.
• Environmental phenotypes develop due to interaction with factors like sunlight or diet.

Adaptation

• Thick fur on polar bears is an adaptation for warmth.
• Bears with thinner fur may not survive cold temperatures.
• The population (not an individual animal) evolves over time as advantageous adaptations are passed on.

Speciation

• This is the process by which a species branches from an original one, creating a new species.
• Which involves variation, isolation, and selection.

Fossils

• Remains of living organisms that can include bones, teeth, footprints, tracks, and whole organisms.
• Fossils form only when conditions are optimal such as quick burial, existence of suitable body parts, and minimal geological disturbance.
• Hard body parts fossilize more easily.
• Petrified fossils are remains changed to rock as minerals replace the buried structure.
• Molds and casts form when buried hard parts dissolve, leaving a hollow space.
• Preserved remains can be trapped in substances like ice

Relative Dating

• Determines which of two fossils is older, using the Law of Superposition.
• It can only be used when rock layers are in their original sequence.
• Absolute dating determines the exact age of a fossil, using methods like Carbon-14 or fluorine dating.
• Fluorine dating is a relative dating method that determines the age of bones by measuring the amount of fluorine they have absorbed from groundwater over time.
• Fossils in lower layers are older.

Law Of Superposition

• Describes the relative age of rocks, the oldest being at the bottom.
• Rock formation and fossils enable construction of a geological timeline.

The Fossil Record

• The totality of fossils, both discovered and undiscovered.

Earth’s Evolutionary Timeline

• Eons: Phanerozoic, Proterozoic, Archean, Pre-Archean
• Era: Cenozoic, Mesozoic, Paleozoic
• Period: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Tertiary, Quaternary

Peppered Moths

• Found in England, Europe, and North America.
• Small size, 1.5 to 2.5-inch wingspan.
• Wings speckled, giving a "peppered" appearance.
• Eggs hatch in mid-summer, larvae feed on birch, willow, and oak leaves, resembling small branches for camouflage.
• Larvae can change colour from brown to green.
• Pupae stage in winter, emerge as adults in April and May.
• Adults lay eggs and die by summer's end, living up to one year.
• Colour morphs: Typica (light grey), Carbonaria (dark), Insularia (intermediate).
• Predators: Flycatchers, nuthatches, and European robins.
• Avoid predators by flying at night, resting during the day.
• Camouflage is enhanced by resembling tree bark and lichens.

Evidence for evolution

• Anatomy is the study of body structure.
• Homologous structures evolved from a common ancestor, look similar, but have different mature forms and functions.
• Vestigial structures have lost most or all of their original function.
• They are usually dwarfed and useless.
• Sometimes vestigial structures can be adapted for new uses.
• Analogous structures serve the same function but differ in internal anatomy.
• They are likely NOT from a common ancestor.
• For example, the wings of birds and bats.
• They are of no use in classifying organisms or figuring out evolutionary relationships.