<span>The smell of Danger.
Researchers have discovered a single compound found in high concentrations in the urine of carnivores that triggers an instinctual avoidance response in mice and rats. This is the first time that scientists have identified a chemical tag that would let rodents sense carnivores in general from a safe distance.</span>
Answer: Van der Waals forces
Explanation:
Van der Waals forces are weak intermolecular forces that depend on the distance between two particles. They are caused by correlations in the change in polarization between two nearby particles. To put it in other words, when a particle changes its polarization (becomes more positive on one end and more negative on the other), so does the adjacent particle, and the next one, and so on. This causes these particles to stick together weakly.
The tiny "hairs" increase the surface area of the gecko's feet in contact with the wall, which makes the bond stronger and allows it to support all of its weight.
Because experiments have shown that geckos stick well to both hydrophobic and hydrophilic surfaces, we can assume there aren't any hydrogen bonds present.
Ionic bonds can't be present either because geckos wouldn't stick to electrically neutral surfaces, as these bonds require charged molecules.
Answer:
Undergrowth of water plants hypoxia
Low levels of oxygen.
Explanation:
Eutrophication occur when lake or river has adequate nutrients that will encourage the growth of water plants i.e algae which lead to the depletion of dissolved oxygen in the lake. The growth of algae is increased due to availability of carbondioxide or phosphorus or nutrients required for photosynthesis. This result in tainted drinking water,hypoxia and degradation of recreational activities.
Answer:
It is because the axons that fail to find a target cell die thats why every axon in an adult mammal has a target cell (muscle cell or other neuron) with which it makes synaptic contact.
Explanation:
Synapse is basically a structure in the nervous system responsible for the passage of the electrical and the chemical signals from one neuron to another neuron or an effector cell.
Usually the axon is the presynaptic part of the synapse and the postsynaptic part is usually present on the body of the neuron or a dendrite or an effector cell like a muscle cell.
If the axon doesn't make a synaptic contact with the target cell , the axon will die because the neurotransmitters and the chemical mediators will not be released and no action will result on the postsynaptic membrane.
