Answer:
What does DNA do? DNA contains the instructions needed for an organism to develop, survive and reproduce. To carry out these functions, DNA sequences must be converted into messages that can be used to produce proteins, which are the complex molecules that do most of the work in our bodies.
Explanation:
Answer: B). Primary succession takes place over a long period of time on a newly formed land, while secondary succession occurs quickly in areas that have disrupted by a natural disaster.
Explanation:
A succession is a gradual change that occur within the biotic community due to change in the non-living environmental factors with respect to time until the community establish stability.
A primary succession occurs over a land which was not previously occupied by any living species. The land can be primitive, environmental factors like soil, air and others are not supportive initially. Thus, it takes long time to establish a biotic community.
A secondary succession occurs over a region which was previously inhabitated by colonies of species but disturbed due to natural calamity or human induced disaster. Some of the precursors of life can be found in such region like seeds, spores, roots and others which support new growth and the environmental factors are suitable to support re-establishment of living species. Hence, secondary succession takes place quickly as compared to primary succession.
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.
