Final answer:
The pre-Mendelian idea that sex cells contain a miniature adult called a homunculus is false. Human development begins with a sperm uniting with an egg to form a zygote, leading to mitosis and differentiation, influenced by factors such as epigenetics. Meiosis produces haploid gametes, which combine during fertilization to begin the development of a new individual.
Step-by-step explanation:
The idea that sex cells contain a miniature adult, known as a homunculus, which just grows up during development is false. This concept was part of a pre-Mendelian theory called preformationism, where it was believed that organisms develop from miniaturized versions of themselves. However, with the advent of microscopy and further scientific study, it became clear that human development is a complex process that starts when a sperm unites with an egg, forming a single cell called a zygote. This zygote then undergoes countless rounds of cell division through the process of mitosis, and differentiation, ultimately resulting in a multicellular organism made up of trillions of cells organized into various tissues and organs. The development and differentiation of cells are due in part to epigenetics, a field of biology that studies how environmental factors affect gene expression.
Furthermore, the claim that there is little change in the reproductive system between infancy and puberty is not accurate. During puberty, significant changes occur in the reproductive system, which enable sexual reproduction. Meiosis is the process that leads to the formation of haploid gametes —sperm in males and eggs in females—each containing half the number of chromosomes found in somatic cells. The fusion of these gametes during fertilization restores the diploid state, and the resulting zygote contains a full set of genetic instructions to develop into a new individual.