Thinking back to the structure of the cell, we know that mitochondria are not only the powerhouses of the cell, but they store important genetic material.
Mitochondrial inheritance occurs when a trait encoded in the mitochondria gets passed down. Because mitochondria are passed into the egg from cells in the ovary, offspring can inherit a genetic condition via the mitochondria. An affected male does not pass his mitochondria down to his offspring, so when we think of mitochondrial inheritance, we know that it always occurs on the maternal (mother) line.
Mitochondrial inheritance can be caused by incorrectly functioning mitochondria, an alteration in the nuclear DNA, or an alteration in the mitochondrial DNA.
Examples of mitochondrial inherited illnesses in humans include mitochondrial myopathy, Kearns-Sayre syndrome, Leigh’s syndrome, and Mitochondrial Depletion syndrome (MDS).
Sickle-cell anemia is an inherited disorder. People with sickle-cell anemia produce abnormally-shaped red blood cells (shaped like crescents, or sickles), which means the cells can’t transport enough oxygen to the body.
This condition is caused by mutations in the HBB gene and is an inherited autosomal recessive disorder. That means that a person inherits sickle-cell anemia only when both parents have at least one recessive copy of the gene. You can be a carrier for sickle-cell anemia without showing symptoms, and people who suffer from the disease inherited both recessive copies.
Human Impact on the Extinction of Species
Humans have impacted wildlife diversity in several ways.
Habitat loss: Habitat loss refers to the destruction or alteration of a natural landscape for human purposes, such as construction. Housing developments, malls, cities, and roads are all examples of how humans have caused habitat loss. Deforestation for logging is another type of habitat loss. This destroys the balance of natural ecosystems.
Amphibians (frogs, toads, and salamanders) are small organisms that are very sensitive to ecosystem changes. Their numbers have declined with habitat loss. Primates are an example of animals displaced by deforestation. When habitats are destroyed, this creates an imbalance in the ecosystem: not only do animals no longer have space to live, but the change in the landscape creates unfair competition, lack of food, or lack of nesting sites.
Water pollution: People have contributed to pollution through the use of motorized boats (which emit both gas pollution and noise pollution), dumping waste into the waterways (agricultural waste, such as fertilizers, pesticides, or human waste), dumping trash, or oil spills.
Seabirds and marine mammals have been harmed by pollution when infectious diseases get spread into the waterway, they consume pesticides or chemicals, or they become tangled in trash. Oil spills cause massive death and destruction to aquatic life, from birds and mammals down to algae and coral.
In Florida, the manatee population is threatened by humans’ water activity: about 150 manatees die each year from being hit by motorized boats.
Air pollution: When chemicals saturate the air, that culminates in air pollution. “Chemicals” include smog and smokey byproducts of cars or industrial living. When acidic pollutants combine with water droplets in clouds, this becomes acid rain. Acid rain damages the environment by killing or harming plants, fish, and wildlife. Acid rain can change the quality and makeup of soils, seep into water systems, and even creep into the airways of animals or humans.
Climate change: Humans have contributed to climate change by the increased CO2 emissions in the atmosphere. This causes increased global temperature on land and sea. An average increase in global temperature causes polar ice cap melt (which leads to increased sea level rise); warmer, drier weather in temperature regions (contributing to drought and habitat loss); coral bleaching; and extreme weather patterns. All of these cause disruptions in migratory patterns of animals, loss of food sources, loss of habitat, and an inability to cope with new environments.
Disease: Modern humans are able to travel with ease. This leads to increased transmission of disease, both from person-to-person and person-to-animal. When habitats are introduced to non-native diseases, the animals do not have the built-up immune responses to fight off the diseases. People can spread disease just by travel, but also by traveling with their domestic livestock (dogs or cattle, for example), and this can spread disease.
The introduction of avian malaria, for example, caused a major threat to endemic birds of Hawaii.
Introducing invasive species: When humans transport new species to an area, this is called introducing an invasive (non-native) species. The introduction of new species disrupts the entire natural ecosystem, causing endemic species to have to compete for food, habitat, and mates.
Popular examples of invasive species are the introduction of the European Starling to America in the 1800s and the introduction of the Bullfrog to Australia in the 1900s. Starlings quickly displaced endemic birds and populated so quickly that today, they are considered a nuisance. Bullfrogs were introduced to Australia for pest control but soon took over entire habitats, threatening several species toward extinction.