Question

Which of the following is an example of homoplasy? a. hair in humans and fur in mice b. astragalus ankle bones in hippos and deer c. Hox genes in humans and flies d. streamlined bodies in dolphins and ichthyosaurs.

Short answer

The correct answer is d. streamlined bodies in dolphins and ichthyosaurs, as they represent homoplasy. Their streamlined bodies evolved independently due to similar environmental pressures, despite not sharing a recent common ancestor.

Step-by-step solution

Identify the traits in the options

Look at the traits mentioned in the given options: a. Hair in humans and fur in mice b. Astragalus ankle bones in hippos and deer c. Hox genes in humans and flies d. Streamlined bodies in dolphins and ichthyosaurs

Determine which traits have evolved independently in unrelated species

Research and compare the evolutionary history and environment pressures experienced by the species mentioned in the options: a. Hair in humans and fur in mice: Both humans and mice are mammals, and hair is a common ancestral trait shared among mammals. b. Astragalus ankle bones in hippos and deer: Both hippos and deer are ungulate (hoofed) mammals, and the astragalus bone is a shared characteristic among them due to common ancestry. c. Hox genes in humans and flies: Hox genes are essential for the development of complex body plans in animals, and their presence across diverse species (including humans and flies) is a result of common ancestry. d. Streamlined bodies in dolphins and ichthyosaurs: Dolphins are marine mammals, while ichthyosaurs were marine reptiles. Both species faced the same environmental pressure to be more streamlined for efficient swimming and reduced drag in the aquatic environment, leading to convergent evolution, which results in homoplasy.

Choose the example that matches homoplasy

The correct answer is: d. streamlined bodies in dolphins and ichthyosaurs. This is an example of homoplasy, as their streamlined bodies have evolved independently due to similar environmental pressures despite the species not sharing a recent common ancestor.

Key concepts

Convergent Evolution

Convergent evolution is an intriguing phenomenon in the realm of evolutionary biology where unrelated species evolve similar traits independently. This occurs when organisms from different lineages face comparable environmental pressures and natural selection favors similar adaptations for survival. A classic example is the development of streamlined bodies in aquatic animals like dolphins and the extinct ichthyosaurs. Dolphins are mammals and ichthyosaurs were reptiles, yet their bodies evolved to take on similar hydrodynamic shapes.

Why does this matter? Understanding convergent evolution helps us appreciate how life can mold distinct species with no recent common ancestor into resembling one another because of the demands of their habitats. This can sometimes mislead researchers to assume a close relationship between species that look alike but are, in fact, on distant branches of the tree of life.

Evolutionary Biology

At its core, evolutionary biology is the study of the origins and changes in the diversity of life over time. It involves exploring how genetic variations occur within populations and how these variations contribute to the physical traits—or phenotypes—of organisms. The theory of evolution by natural selection, first described by Charles Darwin, explains the process by which advantageous traits become more common in a population.

Homoplasy, the independent evolution of similar traits, is a crucial concept in evolutionary biology. It showcases that evolution isn't a linear path but rather a complex network, where similar problems (like moving efficiently in water) can lead to similar solutions (streamlining the body), even in unrelated species.

Comparative Anatomy

Comparative anatomy, a branch of morphology, stretches our understanding of evolutionary relationships by examining the similarities and differences in the anatomy of different organisms. By studying structures like the limbs of mammals or the wings of birds and bats, comparative anatomy reveals patterns of shared ancestry and adaptive evolution.

When comparing anatomical features, homologous structures indicate common ancestry, while analogous structures have independent origins. For instance, the wing of a bat and the arm of a human are homologous; they're built from the same basic skeletal structure. The wings of birds and insects, on the other hand, are analogous; despite providing the same function—flight—they evolved independently. Comparative anatomy helps scientists understand whether resemblances in species are due to shared lineage or environmental pressures leading to homoplasy.