BSC 111-H001 Chapter 17: Speciation and Macroevolution

Practice flashcards for BSC 111-H001 covering models of speciation, species concepts, reproductive isolation, and principles of macroevolution.

What is the main distinction between microevolution and macroevolution?

Microevolution refers to evolutionary changes within populations of a single species over short periods without creating new species, whereas macroevolution is the origin of new species (speciation) over long periods representing the large-scale history of life.

Why do cryptic species pose a challenge to the morphological species concept?

Cryptic species look morphologically identical to human observation, meaning their distinct genetic or physiological differences can be missed without molecular analysis such as DNA evidence.

Who proposed the biological species concept in the 1942 book Systematics and the Origin of Species?

Ernst Mayr

What are the five prezygotic isolating mechanisms that prevent reproductive attempts or fertilization?

Habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, and gamete isolation.

What postzygotic isolating mechanism is illustrated here when a female horse and male donkey reproduce?

Hybrid sterility, because the resulting mule offspring cannot successfully produce gametes and reproduce.

How is a species defined according to the evolutionary species concept, and where is it primarily applied?

It is defined as a single lineage of ancestor-descendant populations evolving separately with shared diagnostic traits and a common evolutionary fate, used primarily to identify species in the fossil record.

Under the phylogenetic species concept, what is a monophyletic group?

A branch on a phylogenetic tree that contains all the descendants of a common ancestor, representing an unbroken line of evolutionary descent.

How does speciation progress in a ring species such as the Ensatina salamanders in California?

Populations diverge around a central geographic barrier where neighboring populations interbreed, but populations meeting at the far end of the ring have diverged enough that they no longer recognize each other as mates.

What is reinforcement in the context of allopatric speciation?

Reinforcement occurs when recently diverged populations come back into contact, no longer recognize each other as potential mates, and develop distinguishing traits that reinforce reproductive isolation.

In this plant speciation process, what parent species and chromosome numbers combine to produce the hybrid that doubles its chromosomes to form Clarkia pulchella ($2n = 24$)?

Clarkia concinna ($2n = 14$) and Clarkia virgata ($2n = 10$).

How did the introduction of domesticated apples to America lead to sympatric divergence in Rhagoletis flies?

Rhagoletis flies originally reproduced only on native hawthorns, but a subpopulation adapted to introduced apples, causing reproductive divergence within the same geographic region.

What is ecological release, and how does it facilitate adaptive radiation?

Ecological release is the freedom from controls by predators, disease, or competition, allowing an ancestral species to expand into previously unavailable microhabitats and rapidly diversify into many new species.

How do the gradualistic model and the punctuated equilibrium model differ regarding the pace of macroevolution?

The gradualistic model proposes that macroevolution occurs slowly and continuously over time, whereas the punctuated equilibrium model suggests long periods of species stability interrupted by rapid periods of evolution.

What role do Hox genes play during animal development?

Hox genes dictate body plans by governing the number and placement of repeated structures, such as vertebrae in vertebrates.

What percentage of all species that have ever existed on Earth are estimated to be extinct?

$$99\%$$