Biology Midterm

DNA sequence are read in groups of ____ called a codon.

3

DNA strands are read in groups of ____, called a codon.

3

Define Codon (Biology-DNA based definition)

A codon is a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule.

If a human somatic cell contains 46 chromosomes, how many chromosomes would be in a human sex cell? Why?

A human sex cell would contain 23 chromosomes. Two sex cells must combine to make a somatic cell. Half of 46 is 23 making sexcells have 23 chromosomes.

What are the four nucleotide bases in DNA, and which ones pair together?

Adenine ---------- Thymine Cytosine ---------- Guanine

What do these codons produce, making DNA like a recipe or blueprint?

proteins and amino acids

Complete the sentence: Organisms with the most beneficial traits are more likely to survive and __________, thus continuing to pass on the __________ _________.

reproduce; best traits

Compare asexual versus sexual reproduction. Contrast the advantages and disadvantages of each.

Asexual reproduction requires one parent while sexual reproduction requires two parents. There are no genetic differences in asexual reproduction because offspring are exact copies. There are genetic differences in sexual reproduction because both parents contribute to the offspring's genetic make-up. Some advantages of asexual reproduction are that offspring can be produced quickly, you only need one parent, and the population increases faster. Disadvantages are that all offspring are genetically identical to their parents and a different factor being introduced to the environment can wipe out a species. Advantages of sexual reproduction are genetic diversity, the ability to adapt, and an unknown factor that is less likely to affect the entire species. Disadvantages are that two mates are required and it takes longer to reproduce.

What ultimately caused the bacteria in Addie's body to become pan-resistant, in other words, resistant to everything?

Being exposed to many types of antibiotics made the bacteria in Addie's body pan-resistant. The bacteria adapted and became more immune to each antibiotic. The constant exposure to only made the bacteria stronger which made it pan-resistant.

This is Darwin's finches. Which of the birds would be most likely to survive in an environment with trees called betel palms that produce nuts with tough outer husks as a primary food source?

Bird number 1 would most likely survive because of its big hard beak. It would be able to crack the tough outer shell of the nuts.

What shape is DNA?

Double Helix

What is the theory of natural selection? KNOW THIS AND BE ABLE TO APPLY IT

Natural selection is the theory that the organisms best suited for the environment will survive and reproduce more than those who aren't and that the species will evolve and require the most beneficial traits.

The black-tailed jackrabbit lives in the desert. These rabbits maintain their body temperature by releasing heat through their long ears. If global temperatures continue to rise, what change would be expected in this rabbit species over time?

Overtime, the rabbit population will become lighter and grow longer ears. Dark colors absorb more heat than lighter colors. A lighter fur will reflect the sun and maintain the rabbits body temperature. The species could also grow longer ears. The longer their ears, the more heat they can release.

If you are given a DNA strand that reads AACGTTA, what would the complementary strand look like?

The complementary strand would read TTGCAAT.

Sea gulls prey on hermit crabs on the rocky sea coast. The crabs vary in color from solid brown to brown and tan striped. The birds suck the soft crab bodies out of the shells and leave the shells behind on the rocks. Scientists picked up 500 empty shells and found that 400 of the shells were solid brown and only 100 were striped. Over the years, what would you expect to happen to the crab population? Why?

The crab population will begin to evolve into being striped. This is because of natural selection and adaptation. Natural selection is the theory that organisms that are suited best for the environment will survive and reproduce more than those who aren't. Because the striped crab is the 'fittest' in the environment, the species will begin to adapt and become striped in order to survive.

What are the key physical and behavioural differences between Mountain Juncos and UCSD Juncos?

The key physical differences between the UCSD Juncos and the Mountain Juncos are the wingspan and the tail feather color. The key behavioral difference is boldness of each species. UCSD birds are extremely bold while Mountain Juncos aren't.

In the giraffe population there is a variation in neck lengths among individuals. Some have longer necks and some have shorter necks. In a scenario where monkeys swarm into an area and tear all of the leaves off the bottoms of the trees, which neck variation of giraffes would be more likely to survive?

The longer neck population would be more likely to survive. Because there would be no bottom leaves, the giraffes with longer necks would have nothing to eat because they can't reach the leaves on the top of the trees like the long neck giraffes. The longer neck giraffes would be the only ones who would be able to eat making them more likely to survive.

A phenotype is a physical characteristic, while a genotype is the actual combination of alleles (Aa, AA, or aa). Over a period of time, one characteristic (such as spots) is naturally advantageous over the other (no spots) due to the fact that a natural predator prefers the non-spotted species. What might a population distribution graph of the organism look like over time? Why?

The population of species with spots will increase because it is the more advantageous trait and has a higher survival rate. This would result in the line associated with the spotted species to increase and the line associated with to decrease.

A biologist conducting a long-term eld study noticed there were two types of coyotes in a valley. One type of coyote had webbed toes, and one type of coyote lacked webbed toes. A dam was built in the valley turning the land into a wetland. As the years passed, all coyotes living in the valley were found to have webbed toes. No coyotes were found with non-webbed toes. Which statement best explains the observed change in the coyote population?

This is a result of natural selection. The webbed toed coyotes has a competitive advantage over the non webbed toed coyotes. Because they were better suited for the environment, they survived and reproduced more than the non webbed toed coyotes which made that population die out.

Natural selection can result in structural changes in appearance, size, and/or shape of individuals in a population. How does this process occur?

This process occurs as the use of the animal changes. For example, as time passed, people began to use horses for transportation, shipping goods, and war. They were being used more and for longer periods of time. This caused the bones and feet of horses to grow longer and stronger.

Some mutations always occur from generation to generation. But most mutations do not persist over time in the gene pool. Which mutation is MOST likely to become established and persist in a species?

a. a mutation that changes the color of an iguana's eyes b. a mutation that makes it harder for a seal to catch food c. a mutation that helps an insect conceal itself from predators* d. a mutation that causes a lion to attack humans more frequently