Page 312 - ABCTE Study Guide_Neat

B It would be inverted.

C It would be narrower at the bottom and wider at the top.

D None of the above

Answer

The correct answer is A. Because less energy is available to top consumers, an ecosystem can support
far fewer of these organisms than it can plants and herbivores.

Review

• Energy from the sun drives the hydrologic cycle, photosynthesis in plants, and
transpiration of water.
• Few organisms can make any use of the atmospheric N 2, making them dependent on
the nitrogen cycle.
• The food chain is arranged by trophic levels: producers, consumers (primary,
secondary, etc.), and decomposers.
• The varying temperatures of the seasonal cycle have a dramatic effect on the operation
of the food chain (or food web).

Genetics and Heredity

Lesson Objective

In the upcoming sections, we’ll take a look at genetics and one of the most famous members of the field,
Gregor Mendel. We’ll also see how genetic traits get passed along via natural selection.

Previously Covered:

The preceding pages reviewed the various cycles (hydrologic, nitrogen, etc.) integral to life on the planet.
We also examined how energy moves in the plant and animal world through the food web and other
processes.

Basic Heredity

Long before anything was known about DNA, chromosomes, or genetics, scientists knew traits could
be passed from parents to offspring. It was not until Gregor Mendel’s work with garden pea plants
that an initial mechanism was proposed. What was critical about Mendel’s approach was that it was
experimental and applied the principles of probability.

From studying mitosis and meiosis, you know that crossing over can lead to a shuffling of genes between
pairs of chromosomes. Thus, traits can seemingly disappear or offspring can have traits very different
from their parents. Even with this shuffling, the basic principles revealed by Mendel’s experiments
provided a foundation for the principles of inheritance including: