Freshwater ecosystems have been modified by the creation of dams and the withdrawal of water for human use, which have changed the flow of many large river systems. This in turn has had other effects such as reducing sediment flows, the main source of nutrients for estuary ecosystems.
Within terrestrial ecosystems, more than half of the original area of many types of grasslands and forests has been converted into farmland. The only types of land ecosystems which have been changed relatively little are tundra and boreal forests, but climate change has begun to affect them.
The distribution of species on Earth is becoming more homogenous. By homogenous, we mean that the differences between the set of species at one location on the planet and the set at another location are, on average, diminishing. The natural process of evolution, and particularly the combination of natural barriers to migration and local adaptation of species, led to significant differences in the types of species in ecosystems in different regions. But these regional differences in the planet’s biota are now being diminished.
Non-native species
Figure 1.7 Non-native species
Two factors are responsible for this trend. First, the extinction of species or the loss of populations results in the loss of the presence of species that had been unique to particular regions. Second, the rate of invasion or introduction of species into new ranges is already high and continues to accelerate apace with growing trade and faster transportation. (See Figure 1.7.) For example, a high proportion of the roughly 100 nonnative species in the Baltic Sea are native to the North American Great Lakes, and 75% of the recent arrivals of about 170 nonnative species in the Great Lakes are native to the Baltic Sea.
When species decline or go extinct as a result of human activities, they are replaced by a much smaller number of expanding species that thrive in human-altered environments. One effect is that in some regions where diversity has been low, the biotic diversity may actually increase—a result of invasions of nonnative forms. (This is true in continental areas such as the Netherlands as well as on oceanic islands.)
hope this helps im not sure it will
Answer:
A
Explanation:
monosaccharide is derived from mono, meaning "one", and saccharide, meaning "sugar". The common monosaccharides are glucose, fructose, and galactose. Each simple sugar has a cyclic structure and is composed of carbon, hydrogen and oxygen in ratios of 1:2:1 respectively. Although each sugar mainly exists as a cyclic compound, it is important to note that they are all in equilibrium to a small extent with their linear forms.
While galactose and glucose are composed of six-membered rings, fructose has only five carbon atoms bonded to each other in ring form.
Explanation:
Firstly, humans have a double circulatory system, which increases blood pressure and flow of blood to the tissues. To allow the heart to pump blood around the body, the heart is made of cardiac muscle. These muscle cells have long protein filaments, which have the ability to slide past each other, shortening the cell and leading to contraction. In order to supply oxygen to cells the heart first pumps the blood into the lungs through the pulmonary artery. Here oxygen diffuses from the air in the alveoli into the blood. Blood then returns to heart via the pulmonary vein. It is then pumped out again, towards the rest of the body, through the aorta. Oxygen is then carried around the body by red blood cells. They are specialised cells, which have no nucleus and contain haemoglobin so that there is maximum space for oxygen. The circulatory system is made up of three types of blood vessels. The first type, arteries, carry the oxygenated blood to the tissues. The second type, capillaries, which have very thin wills and a large surface area to allow for easy and maximum diffusion, deliver the oxygen to the cells for respiration and therefore energy release. Waste products such as CO2 are then removed from the tissues, as they diffuse through the capillary walls and into the blood plasma. The third type of blood vessel, veins, then carry this blood back to the heart. Veins contain valves to keep blood flowing in the right direction and prevent back flow.
Chemical (mutagens)
usually either mimic the structure of nucleotides and are inserted in DNA or either cause
chemical changes (such as alkylation) in nucleotides hence causing mismatching during replication.
Radiation, on the other hand, (due to its high energy) causes double-strand breaks in DNA causing an
increased likelihood of mutations during the repair of the DNA by cell
mechanisms.
Answer:
objectives, operating environments, and categories of effort
Explanation:
