Some species of Chondrichthyes (the class that includes sharks, skates, and rays) produce eggs encased in a tough, leathery pouch (commonly called a “mermaid’s purse”). These eggs are often laid in safe, protected waters by the mother. When the offspring hatches out of the egg, the case may wash up on the beach. (If you enjoy beachcombing, keep an eye out for these on our Texas coast!) The reproductive strategy demonstrated by these species is 

Which is a correct usage of phenotype and genotype?  

A population of salamanders live along the edge of a north-south mountain range. The populations from the east and west slope eventually join in a low northern pass and interbreed, producing fertile offspring, but they do not circle around the southern edge because of a desert barrier. When glaciers move southward, the populations are pushed south of the northern pass and are isolated. While isolated, the two populations develop enough differences over time that when the glaciers retreat north and the salamanders again share the same pass, they no longer mate at the same time, nor can they produce fertile offspring. These salamanders have experienced

The diploid cells of an animal contain ________ alleles per gene located on autosomes. Assume the animal has the normal number of chromosomes. 

DNA strands are often referred to as “complementary.” This refers to the fact that

Match the individual(s) with the correct scientific contribution. Answers may be used more than once. 

RNA which is a complementary copy of a gene is 

Which of the following is an example of a prezygotic isolating mechanisms? 

Positive reinforcement __________ the chances that a given behavior will occur again; negative reinforcement __________ the chances that a given behavior will occur again (Be careful!).

The below image represents an atom of a specific hypothetical element and its own cation.   Which image represents the cation?  Y represents the cation  X represents the cation  What supports your choice?   Cations are larger than their neutral atom Cations are smaller than their neutral atom  Why does this occur?   Because cations lose electrons from the outer most shell, the remaining electrons have a stronger attraction to the nucleus and are pulled closer, thereby making the ion small Because cations gain electrons, the incoming electrons will be repelled by the existing electron and therefore the shell will expand to accommodate them.