Chapter 4, section 4.3 Chapter Review

What three genetic adaptations have helped humans to become such a powerful species?

1. Strong opposable thumbs 2. The ability to walk upright 3. A complex brain

What are five common myths about evolution through natural selection?

1. Survival of the fittest means survival of the strongest. 2. Evolution explains the origin of life. 3. Humans evolved from apes or monkeys. 4. Evolution by natural selection is part of a grand plan in nature in which species are to become more perfectly adapted. 5. Evolution by natural selection is not important because it is just a theory.

What are the two key concepts for this section?

1. The scientific theory of evolution through natural selection explains how life on the earth changes over time due to changes in the genes of populations. 2. Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

What is genetic variability?

A variety in the genetic makeup of individuals in a population.

What is the scientific theory of biological evolution through natural selection?

According to this scientific theory, species have evolved from earlier, ancestral species through natural selection—the process in which individuals with certain genetic traits are more likely to survive and reproduce under a specific set of environmental conditions. These individuals then pass these traits on to their offspring. Biological evolution through natural selection is the most widely accepted scientific theory that explains how the earth's life has changed over the past 3.8 billion years and why we have today's diversity of species.

Explain how harmful bacteria can become genetically resistant to antibiotics.

An example of natural selection at work is genetic resistance. It occurs when one or more organisms in a population have genes that can tolerate a chemical (like as a pesticide or antibiotic) that normally would be fatal. The resistant individuals survive and reproduce more rapidly than the members of the population that do not have such genetic traits.

Define biological evolution (evolution) and natural selection and explain how they are related.

Biological evolution: The process by which species change genetically over time. Natural selection: The process in which individuals with certain genetic traits are more likely to survive and reproduce under a specific set of environmental conditions.

What are two limitations on evolution through natural selection?

First, a change in environmental conditions leads to adaptation only for genetic traits already present in a population's gene pool, or if such traits arise from random mutations. Second, even if a beneficial heritable trait is present in a population, the population's ability to adapt may be limited by its reproductive capacity.

What are fossils and how do scientists use them to understand evolution?

Fossils: The remains or traces of past organisms. Scientists have discovered fossil evidence in successive layers of sedimentary rock such as limestone and sandstone. They have also studied evidence of ancient life contained in ice core samples drilled from glacial ice at the earth's poles and on mountaintops.

What is a mutation and what role do mutations play in evolution through natural selection?

Mutations: changes in the coded genetic instructions in the DNA in a gene. Mutations can occur in any cell, but only those that take place in the genes of reproductive cells may be passed on to offspring. Sometimes a mutation can result in a new genetic trait, called a heritable trait, which can be passed from one generation to the next. In this way, populations develop genetic differences among their individuals.

What is an adaptation, or adaptive trait?

The next step in biological evolution is natural selection, which explains how populations evolve in response to changes in environmental conditions by changing their genetic makeup. Through natural selection, environmental conditions favor increased survival and reproduction of certain individuals in a population. These favored individuals possess heritable traits that give them an advantage over other individuals in the population. Such a trait is called an adaptation, or adaptive trait. An adaptive trait improves the ability of an individual organism to survive and to reproduce at a higher rate than other individuals in a population can under current environmental conditions.