Transcript Evolutionary Biology is Important to Health Science

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 antibioticresistant 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
1.
Under what conditions is the sickle cell allele beneficial to
a heterozygous individual?
2.
Identify a possible risk of overuse of antibiotics.
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.