Heterozygotes for the sickle cell trait have an adaptive advantage in areas where malaria is prevalent. This is an

example of ____.



a. a fixed allele
b. genetic drift
c. a balanced polymorphism
d. sexual selection
e. disruptive selection


ANSWER: c

Biology & Microbiology

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Which of the following describe source-sink metapopulations? 

_____ Sink populations near source populations are less likely to go extinct. _____ Sink populations without access to immigrants from source populations are less likely to go extinct. _____ Source populations usually occupy better habitats. _____ Source populations are less likely to go extinct. _____ The emigration rate from source populations exceeds that from sink populations.

Biology & Microbiology

Which statement is true about chlamydia?

a. It often harms the joints and skin. b. It damages the liver, bones and brain. c. It has no cure.

d. It causes a compromised immune system. e. It can be passed from mother to child during birth.

Biology & Microbiology

The vertebrate jaw first appeared in

a. fishes. b. amphibians. 272 Test Bank c. reptiles. d. birds. e. mammals.

Biology & Microbiology

Most genetic disorders of humans are caused by

A) multiple alleles. B) recessive alleles. C) a mutation that occurs in the egg, sperm, or zygote. D) dominant alleles.

Biology & Microbiology