Chapter 31. Heritability: Plants and Soil
Learning Objectives
Define the concept of heritability.
Understand the role that the environment plays in estimates of the heritability of a trait.
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1. Heritability refers to the extent to which variation among individuals can be attributed to genes. Heritability is greater for some traits (such as height) than for others (such as musical talent).
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2. Surprisingly, the environment also plays a role in heritability. In general, if the environments of individuals are very similar, heritability for any given trait will be high, because genes would be responsible for most of the differences among the individuals.
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3. But if the environments are very different, heritability for that trait will probably drop, because the individual differences in that trait may be influenced by environmental factors.
Practice 1: Different Seeds in the Same Environment
Practice 1: Different Seeds in the Same Environment
Drag the packet of short seeds onto one pot, and drag the packet of tall seeds onto the other pot. Observe the height difference in the plants.
In this simulated experiment, you will use two different types of seeds. The purple packet of seeds has a genetic tendency to produce short plants, while the blue packet of seeds has a genetic tendency to produce tall plants. For the first phase, both planting pots have the same fertile soil—all from the same bag of potting soil. You should assume that all other environmental factors (water, temperature, amount of sunshine, etc.) are held constant.
To begin, drag the packet of short seeds onto one pot, and drag the packet of tall seeds onto the other pot. Observe the height difference in the plants.
Practice 2: Different Seeds in Different Environments
Practice 2: Different Seeds in Different Environments
Drag a packet of each type of seeds onto each type of soil. Then observe the differences in the plants.
In this experiment, you will again use two different types of seeds. You will also use two different types of soil—poor-quality soil and fertile soil. You should assume that all other environmental factors (water, temperature, amount of sunshine, etc.) are held constant.
The genetically short seeds in poor soil yielded very short, weak plants. The plants from the genetically tall seeds grew taller. The differences among the plants in the poor soil are mainly due to genetic factors; thus, heritability for height is high for plants grown in this poor soil.
In good soil, the plants from genetically tall seeds grew taller than those from short seeds. But these plants from short seeds are almost as tall as those from tall seeds in poor soil! When we consider the variation among ALL the plants, heritability drops and the role of environment becomes clear.
Quiz
Quiz
Read the idea for an experiment about heritability, and then answer the question. When an answer has been chosen, select the CHECK ANSWER button.