1)
many plants have thorns on their stems or leaves. what is the most likely explanation for the evolution of thorns?
a) thorns plants produce more food from photosynthesis.
b) thorns are an example of a mutation that arises in the genetic code of plants.
c) thorns plants to conserve resources like water and soil nutrients that may be used by other organisms.
d) thorns are an adaptation that some plants have evolved in order to discourage herbivores from eating the plant.
2)

in any population there will be variations of certain characteristics. for example, in the giraffe population there is a variation in neck lengths among individuals. some have longer necks and some have shorter necks. giraffes with a longer neck variations would be more likely to survive than shorter-necked giraffes in which of these situations?
a) loggers come in and chop down all of the trees
b) insects can only eat the highest leaves due to the canopy
c) a plant disease infects the trees, resulting in total leaf death.
d) monkeys swarm in and tear off all of the lower leaves to use for shelters
3)

some giraffes have long necks and some have shorter necks. the ones with longer necks can reach food sources like tall trees as well as eat grasses on the ground.

how will this difference most likely the giraffe population?
a) their number will remain unchanged.
b) over time, more will have longer necks.
c) giraffes will move from place to place for food.
d) there will be great differences among the giraffe population.
4)

consider the model for natural selection. in a population of living things, genetic variation exists. one source of variation is mutation. which scenario listed here could be a mutation that causes members of a population to die out?
a) in a population of fast-running cheetahs, some are born that run slower than most.
b) in a population of sunflowers, mutations cause some flower heads to produce more seeds.
c) in a population of brownish rabbits that live in the tundra, some are born with fur that turns white in the winter.
d) in a populations of birds, mutations result in different beak sizes so the birds do not compete for food in the area.
5)

darwin hypothesized that there are definite steps to natural selection. consider the model here. use the roman numerals (i - iii) to guide you through the steps. which is an accurate description of darwin's hypothesized theory of natural selection?
a) sexual reproduction of bacteria cause variation. some bacteria survive and some do not. over time all of the bacteria should become extinct.
b) in any population, variation exists. some bacteria are resistant to antibiotics. most bacteria die, but the bacteria that are resistant survive and reproduce.
c) in a population of bacteria that are exposed to antibiotics, some bacteria change their genetic make-up and survive. the new genetic make-up is passed on to offspring.
d) there is a change in the environment: an antibiotic is added. some of the bacteria are capable of changing to the new environment. they survive and reproduce, passing along their favorable traits.
6)

the picture depicts three generations of moths over time. in the beginning, the environment was free of air pollution and the light colored moths were more prevalent in the forest against the light colored trees. however, as air pollution started to increase, black colored moths were more prevalent in the forest.
which hypothesis provides the best explanation as to why the moth populations changed over time?
a) each moth changed color to adapt to the changing environment.
b) as the soot covered trees became more prevalent, lighter colored moths stood out and were eaten.
c) as the environment changed, darker moths were less likely to survive, reproduce, and pass on their genes.
d) the light colored peppered moths avoided predation because they were better adapted among the soot colored trees.