The four limitations are
1.It's often impossible to repeat trials on the same subjects.
2-Subjects may report an inaccurate medical history.
3-It can be difficult to control all possible variables.
4-It's impossible to come up with testable scientific questions for human subjects.
Research involving human beings is ultimately necessary for improvements in human health and welfare. Any results about healthy physiology, illness causes, treatment effectiveness, learning, or behavior must be verified by carefully controlled investigations involving human participants. Sadly, not all human research have been valid and beneficial. It is possible to harm people in the name of research. The most well-known instances happened in Nazi Germany. Investigations conducted after the war found several crimes, including experiments in which participants were submerged in extremely cold water to determine how long it would take them to pass away from hypothermia.
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Dispersal helps different species to increase their range of places, thereby helping to increase their population size in different regions. Dispersal also helps to avoid crowding of diseases of a single location as species move to different locations.
<h3>What is dispersal?</h3>
- Dispersal is the act of distributing things over a large area. It is when the individuals or seeds move from one site to their growing site.
- Dispersal can be active (move by oneself) or passive (require dispersers).
- Seed dispersal is the mechanism of transport of plant seeds to new sites for germination and the establishment of new individuals and colonies.
- This depends upon the effectiveness of the seed dispersers.
- Seed dispersal occurs by wind, water, animals, bats, explosions or gravity of the earth.
- Dispersal of seeds is very important for the survival of plant species.
- If the plants of same type grow too closely, they have to compete with each other for light, water and nutrients from the soil.
- Seed dispersal allows plants to spread out from a wide area and avoid competing with one another for the same resources.
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In the case of liquid droplets, including water, surface tension is the factor, which is accountable for their shapes and configuration. Though can easily be malformed, the droplets of water seem to be pulled into a spherical shape due to the cohesive forces of the surface layer.
In the non-existence of other forces, involving gravity, the drops of almost all the liquids would be almost spherical.
Answer:
lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually, some of the magma pushes through vents and fissures to the Earth's surface. Magma that has erupted is called lava. Some volcanic eruptions are explosive and others are not.
Seminal vesicles
prostate gland
bulbourethral glands
I hope this helped. :)
