Evolution and Natural Selection

Scientists estimate that there are more than 20,000 species of ants. The species range in size from 1 mm long to 38 mm long and live in most environments. The diets of ants range from flowers and seeds to fluids from their own larvae. Ants have been able to successfully inhabit so many different environments because their populations have been able to -

• hybridize with other species of insects

• adapt to a variety of habitats and food sources

• fill niches usually occupied by mammals

• occupy habitats that have no other life forms

A prey population consists of individuals with a variety of running speeds. The adaptation that allows some of these animals to run fast would be an example of natural selection if it helps them -

• survive and undergo mutations in their DNA

• lower the mortality rates of the population

• produce offspring that run at average speeds

• reproduce and increase the frequency of their genes in the population

In the 1940's, the scientist J. B. S. Haldane linked many human red blood cell disordres with the tropical regions where malaria occurs. Haldane hypothesized that the widespread presence of these red blood cells disorders as well as traits that protect individuals from malaria were the result of natural selection. Haldane's hypothesis was later confirmed by the research of A. C. Allison. The resistance of malaria carried by individuals in areas where malaria is widespread is the result of -

• a vaccine against malaria

• the individuals genetic composition

• antibiotic medication

• the individuals behavior in avoiding those with infection

B7A Scientists can determine relatedness among organisms by comparing partial amino acid sequences. The table shows four partial amino acid sequences from four organisms.

Which organism is the LEAST related to the other three organisms'

• Organism 1

• Organism 2

• Organism 3

• Organism 4

B7A The image shows part of the humerus bone in different genera of primates.

Which statement is best supported by the observable structures of the different humerus bones?

• The primates lived in similar environments.

• The primates shared a common ancestor.

• The primates interbreed with similar organisms in a population.

• The primates had diets that consisted of similar types of foods

B7A Cetaceans are whales and their relatives. The diagram shows some fossils of cetaceans

Which statement prov ides the best evidence that Ambulocetus natans is an ancestor of

Basilosaurus isis?

• Homologous structures occur in each fossil.

• Similar nitrogenous bases are found in the DNA of each fossil.

• The fossils were found in different locations

• The youngest fossil is larger than the older fossils

B7A An analysis of DNA and RNA sequences can be used to classify organisms. A dendrogram, such as the one shown below, is based on molecular data . It can be used to represent evolutionary relationships within a group of organisms that are hypothesized to have descended from a common ancestor.

Which statement is best supported by the information in this dendrogram?

• Lesser pandas are more genetically similar to giant pandas than they are to raccoons.

• Brown bears are more genetically similar to giant pandas than they are to sun bears

• Lesser pandas are more genetically similar to raccoons than they are to giant pandas.

• The bear species are all more genetically similar to dogs than they are to giant pandas

After examining the fossil record, scientists have determined that scorpions today are much smaller than their extinct ancestors. For example, Jaekelopterus rhenaniae, a giant scoprtion species that lived 255 million to 460 million years ago was 2.5 meters long. Which of the following conclusions is supported by this information?

• scorpions living today have increased their numbers since they first appeared

• scorpions in the fossil record are smaller than their descendants are

• scorpions have changed as a result of natural selection

• scorpions do not appear in their original state in the fossil record

The cladogram shows the evolution of land plants as indicated by fossil records. Which discovery would challenge the validity of this cladogram?

• a large aquatic vascular plants about 200 millions years old

• a species of algae that has existed for less than one million years

• a moss species that has existed for less than 380 million years

• a fossil of a fern more than 425 million years old

This diagram of the fossil record represents changes in mollusks over millions of years. How can the pattern of change in the fossil record best be explained?

• the mollusks were well adapted to their stable environment. a large, sudden change occurred in their environment. after the change the mollusks with the bigger shells were better adapted for the new environment

• the mollusks were well adapted to their stable environment. the mollusks hybridized with a smaller species of mollusk. a new species of mollusk with a bigger shell resulted

• the mollusks were not well adapted to their environment. the length of the mollusks shells changed gradually over time. the mollusks in the original population that had small shells died over a period of many years

• the mollusks were well adapted to their environment. humans introduced a new species of mollusk that was not adapted to this environment. the introduced mollusk out competed the native mollusk species