With sexual reproduction a sperm coming from the male must unite with the female egg. Both are needed for this kind of reproduction, and an offspring CAN'T be formed without both. Unlike asexual reproduction, the offspring of a mammal reproducing sexually is DIFFERENT from both parents, since the offspring is a combination of both the mother and the father.
An easy to remember example I use when thinking about what sexual reproduction is:
the formation of a human child. A mother with her egg and the father with the sperm is BOTH needed. If you think about siblings that come from the same parents (and therefore same gene pool) they are not all exactly identical to each other. Although they may have similar features, they look different and are NOT genetically identical
Pinecrest are a plan and are asexual, meaning they do not need a partner to reproduce. although humans and dogs a sexual reproducers, their DNA structure is different and not compatible with human DNA structure. thats why you can't breed a human and a dog.
An set structure of tissues and fibres, basically a meaning of the vascular system for a plant. The xylem tissue distributes water and nutrients to other parts of the plant such as the leaves.
