Pollination and adaptation
Explain why a plant species in which self polination usually occurs can become adaptd to new surroundings better than the one that reproduces asexually, but less well than a species that is always cross polinated.
This is a great question! Generally inbreeding such as self pollination is considered to be detrimental to a species over time, because it can cause double copies of a defective gene to crop up in offspring. However in the case of a plant moving into a new environment, the ability to self pollinate is an advantage, because a single plant can still reproduce and colonize the new area. In self-pollination there is still some shuffling of the genes during meiosis, so not all of the offspring are identical.
Plants that reproduce asexually can do this as well, but in this case every single offspring will be genetically identical, which can cause vulnerabilities to the entire population. A group of genetically identical individuals is known as a clone, and all will share the same strengths and weaknesses.
A species that has to cross pollinate will have the highest genetic diversity, but it may be difficult for such a species to get established in a new area, since there has to be a large enough population of such a species that two or more individuals are blooming at the same time within the range of their pollination method (insects, wind, etc.).