Review Questions

1. Many people are scared of sharks and for that reason they have been hunted and killed in many cases to the point of being threatened with extinction, not to mentioning fishing lines. Many sharks are keystone species in their ecosystems, which make them important.

2. Biodiversity is the variety of the earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes that sustain all. It’s important because it’s a vital renewable resource. A species is a set of individuals that can mate and produce fertile offspring. Insects are pollinators, which help sustain life on earth. Biomes are large regions with distinct climates and a set of species that are adapted to that climate, which include forests, deserts, and grasslands.

3. Fossils are mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks that help to tell us the history of the earth. Biological evolution is the process whereby Earth’s life changes over time through changes in the genetic characteristics of populations. The theory of evolution says that life comes from life. Natural selection is the process in which individuals with certain traits are more likely to survive and reproduce under a particular set of environmental conditions than those without the traits. Mutations are random changes in the DNA molecules of a gene in any cell. Mutations help populations develop genetic variability. An adaptation is any heritable trait that improves the ability of an individual organism to survive and to reproduce at a higher rate than other individuals in a population can. Differential reproduction enables individuals with adaptive traits to leave more offspring than other members of the population leave. Humans have strong opposable thumbs, the ability to walk upright, and a complex brain, which helped us to become so powerful. Two limits to evolution by natural selection are changes in environmental conditions, and if a good heritable trait is present in a population, the population’s ability to adapt may be limited by its reproductive capacity. Three myths are “survival of the fittest”, organisms developing certain traits because they need them, and evolution by natural selection, which involves some grand plan of nature in which species become more perfectly adapted.

4. Geologic processes, like tectonic plate movements, earthquakes, and volcano eruptions, have wiped out large numbers of species and created opportunities for the evolution of new species. Climate change and catastrophes have generated opportunities for evolution. Life on the earth can only thrive within a certain temperature range, the liquid water that Earth has on its surface, energy, food, and shelter.

5. Speciation is when one species splits into two or more different species. Geographic isolation happens when different groups of the same population of a species become physically isolated from one another for a long period of time. In reproductive isolation, mutation and change by natural selection operate independently in the gene pools of geographically isolated populations. If populations are separated, they can develop adaptations to suit their new environment. Artificial selection enables a change in the genetic characteristics of populations by selecting one or more desirable genetic traits in the population of a plant or animal such as a type of dog. Genetic engineering is the alteration of an organism’s genetic material through adding, deleting, or changing segments of its DNA to produce desirable traits or eliminate undesirable ones, like combining fish genes into a tomato plant to give it certain properties.

6. Extinction is when an entire species ceases to exist. Endemic species are species that are found in only one area. They’re vulnerable to extinction because they cannot migrate or adapt in the face of various environmental conditions.