Evolutionary Biology is Important to Health Science Section 14.5

Natural Selection & Sickle Cell Anemia Sickle cell disease (common in Africa) affects about 1 out of every 25 individuals abnormal shape of red blood cells in individuals (normal – round, abnormal – crescent shape) Homozygous recessive to have disorder Heterozygous only carriers Individuals with just one copy of the sickle cell allele are resistant to the disease malaria. This resistance is an important advantage in environments where malaria is a major cause of death in infants.

The map in Figure 14-33 indicates that the frequency of the sickle cell allele in Africa is generally highest in areas where the malaria parasite is most common. Malaria is transmitted by the bite of certain mosquitoes that transfer the disease-causing protist from one person to another.

Evolution of Antibiotic Resistance in Bacteria Antibiotics – kill or slow growth of bacteria But the widespread use of antibiotics also brings risk. It has caused the evolution of antibiotic-resistant populations of the very bacteria the drugs are meant to kill. resistant bacteria multiply and quickly become the norm Doctors are less likely to prescribe antibiotics unless absolutely necessary

Concept Check 14.5 Under what conditions is the sickle cell allele beneficial to a heterozygous individual? Identify a possible risk of overuse of antibiotics.

Part of the Chapter Review Review for Test Part of the Chapter Review

Reviewing Concepts - Multiple Choice 1. Which of the following is an incorrect match? a. Lyell—suggested physical changes to Earth result from geologic processes occurring over long periods of time. b. Lamarck—proposed that organisms adapt to their environment. c. Darwin—developed the theory of natural selection as a mechanism of change in species. d. Malthus—thought that characteristics acquired during an organism's lifetime can be passed on to the next generation. 2. Which of the following provides clues about the size and structure of once-living organisms? a. fossils b. DNA and proteins from the organisms c. vestigial structures d. development of embryos 3. What statement is not an observation or inference on which Darwin's theory of natural selection is based? a. Variations among individuals exist in a population. b. Poorly adapted individuals never produce offspring. c. Individuals whose inherited characteristics give them advantages in their environment will generally produce more offspring. d. Species living today descended with modification from earlier species. 4. Artificial selection is similar to natural selection in that both processes a. were suggested by Darwin. b. adapt species to their environments. c. occur over many millions of years. d. depend on variation among individuals. 5. What genotype is the most beneficial for individuals living in regions where malaria is common? a. homozygous dominant (no sickle cell alleles) b. homozygous recessive (two sickle cell alleles) c. heterozygous (one sickle cell allele) d. no difference among the genotypes

Visualizing Concepts Complete the concept map to the left using the following choices:

Analyzing Data Analyzing Data A population containing striped and unstriped snails has recently moved into a new region. Birds break the snails open by dropping them onto rocks. The birds eat the bodies of the snails and leave the shells. In one area, researchers counted both live snails and broken shells. The data are summarized below. a. Based on the data, tell which form of snail (striped or unstriped) is more likely to be caught by the birds for food. Explain. b. Suggest a hypothesis to explain what is happening to the snails.