Evidence for Evolution, Sexual Selection, Speciation and Artificial Selection

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Evidence for Evolution

Biogeography

Definition: The study of organisms in relation to their geographic locations.
Example: Jaguars and leopards look alike because they live in similar environments, but they evolved separately.

Fossils

Definition: The study of preserved remains or traces of ancient organisms.
Examples: Bones, footprints, shells, amber, and even fossilized waste.

  • Tiktaalik – A transitional species between land and water (amphibians). It had traits of both fish and amphibians, such as eyes on top of its head, lungs, fins, and flippers.
  • Archaeopteryx – A transitional species between land animals and birds. It had traits of both reptiles and birds, providing evidence for the evolution of birds from dinosaurs.

Homologous Structures

Definition: Similar structures in different species that suggest a common ancestor but may have different functions.
Example:

  • Bat wings and human hands – Both have similar bone structures, but humans use their hands for gripping while bats use theirs for flying.

Analogous Structures

Definition: Different structures in unrelated species that serve similar functions due to similar environmental pressures.
Example:

  • Bird wings and bee wings – Both are used for flying and pollination, but their structures are completely different.

Vestigial Structures

Definition: Structures that are present but no longer serve a function in the organism.
Examples:

  • Humans – Wisdom teeth, appendix, and tailbone.
  • Whales – Small hip bones, a remnant from their land-dwelling ancestors.

Embryology

Definition: The study and comparison of early developmental stages of organisms.
Example:

  • All vertebrate embryos (including humans, fish, birds, and reptiles) look very similar in early development, indicating a shared evolutionary history.

Evolutionary Patterns

Convergent Evolution

Definition: Different species evolve similar traits because they live in similar environments.
Example: Pollinators like birds and bees both develop specialized structures for pollination, even though they are not closely related.

Divergent Evolution

Definition: When two related species evolve different traits due to adaptations to different environments.
Example: Wolves and domestic dogs share a common ancestor but have evolved different traits due to selective pressures of a house vs the woods.

Coevolution

Definition: When two species evolve together, influencing each other’s adaptations.
Example:

  • Predator-prey relationships – In the straw worm experiment, predators (tweezer monsters) ate the larger worms first because they were easier to find. Over time, the population might evolve to favor smaller worms, which were harder to detect. The predators had to adapt with sharper beaks or better vision to continue hunting.

Sexual Selection

Definition: Sexual selection is a specific type of natural selection where traits evolve because they increase an individual's ability to attract mates and reproduce. These traits may not always improve survival, but they are favored because they enhance reproductive success.

Examples of Sexual Selection in Nature

Bright Colors & Ornamentation – Peacocks, birds of paradise, and guppies use vibrant colors to attract mates.
Mating Dances & Displays – Lizards, insects, and birds perform elaborate courtship rituals.
Large Size & Strength – Elephant seals, deer, and gorillas fight for dominance to win mates.
Vocalization – Frogs and songbirds use complex calls to attract potential partners.

Why Does Sexual Selection Matter?

Sexual selection plays a key role in evolution, driving the development of extraordinary physical traits and behaviors. Over time, it can lead to speciation, where new species emerge due to differences in mating preferences.

Speciation

Definition: Speciation is the process in which new species are created. This is usually caused by geographic isolation. These two separate environment will prevent the changes that affect one population from affecting the other. 

Example of Speciation

A species of finches get separated by an earthquake and develop different mutations, mating season, mating calls and physical appearances that over time leads to the development of two different finch species.

Artificial Selection

Definition: Nature proves variations in which humans select which of the variation is desirable. 

Example of Artificial Selection

Wild wolves became domesticated over time to become the different dog species we see today.
Wild cats like the African Serval were selected for and artificially bred to be the housecats we see today.

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