BIO-1407 Chapter 24

Which of the following best describes microevolution?

• The small-scale changes in allele frequencies within a population over time
• The broad accumulation of differences leading to extinction or diversification
• The formation of entirely new taxonomic groups above the species level
• The sudden appearance of species in the fossil record

Answer explanation

Microevolution is the change in allele frequencies within a population over time, whereas macroevolution involves broad evolutionary change above the species level.

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According to the biological species concept, what is the primary criterion for defining a species?

• Members share similar morphological features
• Members occupy the same ecological niche
• Members have a shared evolutionary history
• Members interbreed to produce viable, fertile offspring

Answer explanation

The biological species concept defines a species as populations whose members interbreed naturally and produce viable, fertile offspring.

A mule, the offspring of a horse and donkey, is robust but sterile. This is an example of:

• Reduced hybrid fertility
• Mechanical isolation
• Gametic isolation
• Temporal isolation

Answer explanation

Mules are sterile hybrids, which is a postzygotic barrier known as reduced hybrid fertility.

Which scenario best illustrates allopatric speciation?

• Apple maggot flies diverge into two groups based on different host plants
• A plant species develops polyploidy, producing fertile offspring in one generation
• A lake splits into two smaller lakes, causing populations of fish to diverge
• Cichlid fish diverge due to female mate choice of male coloration

Answer explanation

Allopatric speciation occurs when populations are geographically isolated, such as when a lake splits into two.

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If two species of frogs produce hybrids that have lower fitness than either parent species, what outcome is most likely?

• Stability
• Reinforcement
• Fusion
• Polyploidy

Answer explanation

Reinforcement strengthens reproductive barriers when hybrids have reduced fitness.

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A paleontologist studies fossil records showing long periods of little change punctuated by sudden species appearances. Which model does this support?

• Reinforcement
• Gradualism
• Hybrid breakdown
• Punctuated equilibrium

Answer explanation

The punctuated equilibrium model describes long periods of stasis interrupted by sudden changes.

Which of the following best illustrates macroevolution?

• A shift in allele frequency for coat color in a wolf population
• The frequency of a resistance gene increases in bacterial populations
• A population of finches shows a gradual increase in beak depth over generations
• The rise of mammals after the extinction of dinosaurs

Answer explanation

Macroevolution involves broad evolutionary changes above the species level, such as the emergence of mammals.

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Which situation demonstrates the limitation of the biological species concept?

• Polar bears and grizzly bears produce fertile hybrids called 'grolar bears'
• Different bird species refuse to mate due to unique courtship displays
• Two butterfly species mate but their hybrids are weak and sterile
• Fossil organisms cannot be classified because mating behavior cannot be observed

Answer explanation

The biological species concept cannot be applied to fossils or asexual organisms since interbreeding cannot be tested.

Behavioral isolation can be defined as:

• Fertilization fails because gametes cannot fuse
• Different species occupy different habitats
• Courtship rituals prevent interbreeding between species
• Hybrids fail to reach sexual maturity

Answer explanation

Behavioral isolation arises from differences in mating rituals or signals.

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Which of the following is an example of autopolyploidy?

• A tetraploid plant arising from a diploid plant due to mitotic error
• Cichlid divergence in Lake Victoria due to mate choice
• A mule resulting from a cross between a horse and a donkey
• Wheat, which arose from hybridization between different species of grasses

Answer explanation

Autopolyploidy arises when multiple chromosome sets come from one species, often due to cell division errors.