Ecosystems are composed of communities and communities are composed of populations. A biome is a larger unit than an ecosystem, as it includes multiple ecosystems.

The taiga biome is the largest biome in the world and is characterized by short, rainy summers coupled with long, freezing winters. Due to its extremely cold temperatures, the taiga's flora or plant life consists of mostly coniferous trees that can survive on the scarce nutrients available in the cold climate of the biome. In contrast, the tundra is frozen year-round and permafrost prevents any trees from growing. Deciduous forests, as the name suggests, sports mainly deciduous trees as its plant life. The alpine biome consists mostly of the areas right below the snow lines of mountains and is generally dry year-round. The chaparral is a relatively small biome that is characterized as being mostly hot and dry year-round, with mild winters.

The characteristics listed describe a savanna. Deserts can also have pronounced periods of rain and dryness but are not dominated by grasses and not populated by large migratory animals. Tropical rainforests and deciduous forests are dominated by trees and tundras tend to be colder and may not receive much rainfall, but often have moist soil due to low evaporation rates.

R-strategists are known for producing large numbers of offspring, though few live to maturity. This is a result of low parental investment, competition, etc. Despite such a large number of offspring, the gestation period for these species is generally shorter than that of K-strategists. For instance, the gestation period of mice is much shorter than the nine months seen in humans.

External process also affect the ecosystem. For example, climate is a very important external factor that will affect temperature and precipitation within the ecosystem.

Abiotic factors are the non-living components of an ecosystem. Biotic factors are living things, such as vegetation (the correct answer because it is the only living thing among the answer choices and therefore NOT abiotic).

"k" and "r" refer to two different reproductive strategies. K-strategists tend to occupy a more stable environment and have a larger body size as adults and at birth, fewer offspring, longer life spans, more efficient use of energy, later age of reproduction, slower maturation, more parental care, and longer gestation times. The question asked which characteristic is not generally true of k-strategists, and the correct answer is "shorter life spans," which describes r-strategists instead.

Density-dependent factors are factors that affect population growth only when the population reaches a certain level, and are strongest in a large, dense population and weakest in small, scattered populations. Disease, parasitism, competition, and predation all vary with population density. Natural disasters are the one choice that are density-independent, meaning they affect all populations similarly regardless of size/density.

According to the law of independent assortment, there are 2ⁿ combinations where chromosomes can assort into different gametes. So where n is the haploid number, you get 2²³=8,388,608. There are 8,388,608 possible combinations of chromosomes when assorting into gametes.

As the disorder is X-linked and the subject is male, he only received an X-chromosome from his mother. Therefore, the allele for the disorder must have been inherited from his mother. However, this does not mean that the mother expressed the disorder herself, as she could have the dominant allele in addition to one recessive allele.