A recent study of the eggs of tree frogs in Panama has provided insights into the concept of phenotypic plasticity. A biologist that studied the eggs observed that they would normally hatch a week after they were laid. However, by touching the eggs, the biologist could induce them to hatch immediately. The biologist likened this touch to the vibrations from an attacking snake. The implication was that the egg, even at an early stage, was flexible. It could either wait its usual full term to hatch, or hatch immediately in response to an environmental stressor. This example demonstrates phenotypic plasticity, which is the flexibility an organism has in expressing its genes. The phenotype is the expression of the genotype, or genetic makeup, and plasticity means the ability to change or adapt. Put another way, genotype is the inherited instructions that an organism receives from its genes, while phenotype is its physical appearance and actions.
Early theories of genetics relied on a cause-and-effect model: everything about an organism, including its phenotype, was determined by its genotype. Phenotypic plasticity, on the other hand, allows for the inclusion of environmental factors. For example, some types of plants can allocate more resources to their roots when growing in low-nutrient soil, or change the size and thickness of their leaves in response to the amount of sunlight they receive. Although genes certainly play a major role, individual organisms are not different simply because they have different genes. Rather, organisms can express phenotypic differences in response to variations in ecosystem, diet, temperature and climate.
Which of the following is not an example of phenotypic plasticity, as it is described in the passage?
A. Water fleas can grow sharp spines when in an environment that contains natural predators, while others will not grow the spines when in an environment without predators
B. A plant in an unusually sunny environment will grow thicker, larger leaves in order to absorb more radiation
C. Ectothermic organisms can adjust the composition of their cell membranes, depending on the temperature of their environment
D. The color of some species of tree frog is determined entirely by the genes they inherit
E. Species in environments that offer low quality diets respond by increasing their overall food intake![]()
Early theories of genetics relied on a cause-and-effect model: everything about an organism, including its phenotype, was determined by its genotype. Phenotypic plasticity, on the other hand, allows for the inclusion of environmental factors. For example, some types of plants can allocate more resources to their roots when growing in low-nutrient soil, or change the size and thickness of their leaves in response to the amount of sunlight they receive. Although genes certainly play a major role, individual organisms are not different simply because they have different genes. Rather, organisms can express phenotypic differences in response to variations in ecosystem, diet, temperature and climate.
Which of the following is not an example of phenotypic plasticity, as it is described in the passage?
A. Water fleas can grow sharp spines when in an environment that contains natural predators, while others will not grow the spines when in an environment without predators
B. A plant in an unusually sunny environment will grow thicker, larger leaves in order to absorb more radiation
C. Ectothermic organisms can adjust the composition of their cell membranes, depending on the temperature of their environment
D. The color of some species of tree frog is determined entirely by the genes they inherit
E. Species in environments that offer low quality diets respond by increasing their overall food intake