Answer:
D. the 23rd pair of chromosomes
Explanation:
Humans have a total of 23 pairs of chromosomes. Out of a total of 23 pairs, 22 pairs are autosomes. Autosomes are the chromosomes that carry the genes for all the genetic traits but are not involved in the sex determination of the individuals.
The 23rd pair of chromosomes in humans is of sex chromosomes as these chromosomes carry the genes to regulate the gender of the individuals. A human female has two copies of the X chromosome as sex chromosomes while human males have one X and one Y chromosome as their sex chromosomes. The Y chromosome carries "SRY" gene that codes for testes determining factor and regulates the development of testes in the embryo.
Answer:
Lichens are not parasitic when they grow on trees, they just use the tree bark as a home. They enrich the soil by trapping water, dust and silt. When lichens die they contribute organic matter to the soil, improving the soil so that other plants can grow there.
Answer:
Genetics take a long time to mutate.
Explanation:
Answer: Mercury has been well known as an environmental pollutant for several decades. As early as the 1950's it was established that emissions of mercury to the environment could have serious effects on human health. These early studies demonstrated that fish and other wildlife from various ecosystems commonly attain mercury levels of toxicological concern when directly affected by mercury-containing emissions from human-related activities. Human health concerns arise when fish and wildlife from these ecosystems are consumed by humans.
During the past decade, a new trend has emerged with regard to mercury pollution. Investigations initiated in the late 1980's in the northern-tier states of the U.S., Canada, and Nordic countries found that fish, mainly from nutrient-poor lakes and often in very remote areas, commonly have high levels of mercury. More recent fish sampling surveys in other regions of the U.S. have shown widespread mercury contamination in streams, wet-lands, reservoirs, and lakes. To date, 33 states have issued fish consumption advisories because of mercury contamination.
These continental to global scale occurrences of mercury contamination cannot be linked to individual emissions of mercury, but instead are due to widespread air pollution. When scientists measure mercury levels in air and surface water, however, the observed levels are extraordinarily low.
Explanation:
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