(These are the ones with 2 pills, taken a couple of days apart.) They can be carried out up t â¦ o 12 weeks of pregnancy.   After 12 weeks of pregnancy there are 2 options, one is to have labour induced (You are given a drug which makes the uterus contract) and the other is a surgical abortion.(Removing the contents of the uterus, usually with a vacuum pump.).1 person found this useful. After 12 weeks of pregnancy there are 2 options, one is to have labour induced (You are given a drug which makes the uterus contract) and the other is a surgical abortion. (Removing the contents of the uterus, usually with a vacuum pump.). 1 person found this useful.
keystone species. A keystone species is an organism that helps define an entire ecosystem. By keeping populations of mussels and barnacles in check, this sea star helps ensure healthy populations of seaweeds and the communities that feed on themâsea urchins, sea snails, limpets, and bivalves.
Such predators are known as keystone species and may have a profound influence on the balance of organisms in a particular ecosystem. Introduction or removal of this predator, or changes in its population density, can have drastic cascading effects on the equilibrium of many other populations in the ecosystem.