Final answer:
Both plants and animals originate from a single cell, typically a zygote created from the fusion of male and female gametes. Plants can also reproduce asexually, with certain cells differentiating into new organisms. The cell is central to life, supporting growth and maintenance through division in accordance with cell theory.
Step-by-step explanation:
The Origin of Plant Life from a Cell
It's true that both animals and plants originate from a single cell. In plants, this single cell is the result of the union of pollen (male gamete) and ovule (female gamete), creating a zygote. This zygote undergoes numerous cell divisions, a process known as embryogenesis, to eventually form a multicellular organism, such as a seedling that grows into a mature plant. All sexually reproducing organisms, including plants, start from a zygote, which then gives rise to various cell types during development.
In some cases, plants can also reproduce asexually through somatic embryogenesis, which differs from sexual reproduction. Cells that are not zygotes can develop into new plants, and this process can either happen spontaneously or be induced. Plants such as Bryophyllum and bulb-bearing ferns are examples where structures on the leaves develop into new plants, showcasing the remarkable capacity of plant cells to give rise to complete organisms.
Overall, whether through sexual or asexual reproduction, the cell is central to the development of life. Cell division is crucial for the growth and maintenance of multicellular organisms, with the zygote being the common starting point in the life cycles of sexually reproducing species. This fundamental principle is part of the universally accepted cell theory, which emphasizes that all life begins as a single cell and that all cells arise from preexisting cells.