Ectopic focus or ectopic pacemaker happens when an excitable group of cells outside the normal sinoatrial node causes premature heartbeat. Sinoatrial node (SA node) is the pacemaker of the heart. Most people experience ectopic focus but persistent occurrence may need the client/patient to visit the doctor. If a client or patient complains of ectopic focus, it is better to consider his/her activity before visiting the clinic. Ask, for example if the client/patient had a vigorous exercise because it might be causing the irregular heartbeat, how often is he/she experiences such irregularity in his/her heartbeat (acute ectopic foci is usually non-life threatening, however, chronic type requires medical help), his/her lifestyle (he/she might be using illegal drugs, smokes and/or drinks alcohol,had too much coffee etc). Again, history taking is very vital.
Ionic bond is a compound made up of a meta and a non-metal eg NaCl (sodium chloride)
covalent bond is made up of two non-metals eg H2O (water)
The carbon cycle is affected by a variety of factors, and happens through different processes. The processes can be divided into two, which are biological processes and geological processes. The biological aspect covers the use and production of carbon by living organisms. The geological aspect covers physical processes such as volcanic eruptions, and weathering of rocks, which may result to release of carbon back to the atmosphere. However, both of these aspects can be affected by recurring events in Earth's history. One is the switching between glacial and interglacial periods, and the other one is the seasonal changes. Glacial periods can lead to lower temperatures and lower carbon levels in the atmosphere. In contrast to this, warmer interglacial periods result to higher carbon levels primarily due to an abundance of life. Seasonal changes have a similar effect that can be observed at a shorter time. Human activities such as burning of fossil fuels and deforestation may also bring changes to the carbon cycle.
Indirect methods like mark and recapture become a strong tool to estimate population size or density in species on which it is impossible to apply a direct methods. <em>Because of their biological and ecological characteristics, the Gypsy moth and the Green lizard populations are good examples for which mark and recapture would work well.</em>
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There are different methods to study population density. There are direct methods and indirect methods. Among these last ones, we might find the Mark-Recapture technique.
The Mark-Recapture technique assumes that
- <em>the population is closed during the sampling season, there is no mortality nor natality, </em>
- <em>marks in the individual last the whole sampling season, and they do not affect the marked individual or their behavior. </em>
- <em>marked individuals are randomly distributed in the population, and </em>
- <em>all the individuals have the same probability of being sampled.</em>
The method consists of capturing a sample of individuals belonging to the population under study. After capturing the individuals, the researcher marks and releases them again. The third step is to sample again: The researcher captures new individuals and counts how many of them are marked. These marked individuals belong to the first sample.
Indirect methods like this become a strong tool to estimate population size or density in species on which it is impossible to apply a direct method such as <em>counting individuals</em>.
For instance, if we need to estimate insects population density (<u><em>Gypsy moth population</em></u>) or reptiles population density (<u><em>Green lizard population</em></u>) because of their biological and ecological characteristics, the best way of doing it is by applying indirect methods. <em>These species characterize as small-sized, fast to escape, they can hide in small inaccessible places, they have nocturnal habits, their reproductive rate is too high, and their distribution rate is wide. </em>Among many other characteristics, their population density can not be estimated by direct methods. Mark-Recapture technique is the most suitable one.
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