As with flowers, seeds form within the female cone after pollination. Animals are usually mobile and seek out a partner of the opposite sex for mating. I understand the urge to convey that feeling into words. My life didn't have meaning before I had kids! Many animals and some plants have differences between the male and female sexes in size and appearance, a phenomenon called sexual dimorphism. When a fertilized ovum reaches the uterus, it becomes implanted in the lining of the uterus the endometrium and a pregnancy begins. In genetic sex-determination systems, an organism's sex is determined by the genome it inherits. Those with ID may have limited knowledge and access to contraception, screening for sexually transmitted infections and cervical cancer. In clownfish , smaller fish are male, and the dominant and largest fish in a group becomes female. Unless you and your friend have some previous communication on this topic about how your little one is always welcome, assume the party is not kid friendly. By dismissing the "before" as just a build up to your kids, you are not only dismissing your friends, but you're also implying that their story has not started yet. In many wrasses the opposite is true—most fish are initially female and become male when they reach a certain size. Consensual sexual intercourse is not always an option for some. For gay male pairings, there is the option of surrogate pregnancy; for lesbian couples, there is donor insemination in addition to choosing surrogate pregnancy.