Some simple organisms are unicellular, but more complex organisms are multi-cellular. Multi-cell organisms (e.g. animals and humans) are large and complex. Being Multi-cellular allows organisms to be larger and more complex and allows for cell differentiation.
Becoming multicellular requires development of specialised organ systems for communications between cells, supplying ells with nutrients and controlling exchanges within the environment.
Cells and Gametes
In mammals, most body cells are diploid which means that they contain two set of matching chromosomes. But, some cells can be haploid, which means that they only contain one set of chromosomes.
Gametes are sex cells. They are specialised haploid cells, an at fertilisation they combine to form a diploid zygote. Genetic material from both parents combines to produce a unique individual. Genes on the chromosomes combine to control the characteristics of the zygote.
A sperm is a tiny cell with tail which makes it very mobile. It…