The mechanisms of reproductive isolation prevent the reproduction of two individuals from different species. The prezygotic mechanisms disrupt the stages of reproduction before the forming of the zygote or prevent the mating at the start, and the postzygotic mechanisms affect the stages of reproduction after the forming of the zygote.
So, the first and the third example (the urchins and the grasshoppers) show the prezygotic mechanism, as the two individuals are not able to mate or form a zygote.
The second and the fourth example ( zonkey and the death of a zygote) show the working of the postzygotic mechanisms, as the zygote is formed, but it seems to be inviable, and the zonkeys are sterile, preventing the individual to reproduce.
Answer:
The area under a speed-time graph represents the distance travelled.
Answer:
<h2>Chalamydomonas.</h2>
Explanation:
Protists are those organisms that are unicellular and eukaryotic in nature. They are present in diverse forms and structures and show different types of characteristics/. There are many protists that are harmful to human beings and some other organism that causes certain diseases called parasitic protists such as protozoans, trichomonas and some other. There are some protists that are not parasitic in nature such as Chlamydomonas and some other. Protists have different types of the mode of nutrition that may be autotrophic, saprophytic and parasitic and some other.
Answer:
There are 2 sexes however gender is a spectrum and has proven to part of the brain so yes.
Answer:
The correct order of events is:
C) Nicotine binds to the transmembrane protein that normally binds the neurotransmitter acetylcholine.
A) The acetylcholine receptor is an ion channel, and when a ligand binds, the ion channel opens.
B) An influx of ions carries the signal to the reward areas of the brain.
D) The signal causes release of dopamine in the brain, which causes good feelings.
E) Nicotine is quickly eliminated from the body (causing cravings for more cigarettes to produce good feelings).
Explanation:
Nicotine acts on acetyl cholinergic receptors that are located in membranes of the midbrain neurons. Nicotine can activate those receptors or block them more efficiently than acetylcholine. Stimulation of nicotinic receptors leads to an increase in ions flow that reaches the brain and causes dopamine release in the nucleus accumbens through axonal prolongations of the dopaminergic pathway. This response is responsible for the smoker´s recompense sensation.
The dopaminergic pathway is the most important way in the process of nicotine dependence and addiction to the drug.
