Organisms grow through growth of existing cells.
There is a framework for K-12 science education.
By the end of grade 2.At different stages of development, plants and animals have predictable characteristics.Plants and animals change.Plants and animals can be young.In many animals, parents and offspring engage in behaviors that help the offspring to survive.By the end of grade 5.The continued existence of every kind of organisms depends on reproduction.Plants and animals have different life cycles that include being born, growing, developing into adults, reproducing, and dying.By the end of grade 8.Organisms can reproduce sexually or asexually.The odds of reproduction increase when animals engage in characteristic behaviors.Plants can reproduce in a variety of ways depending on animal behavior and specialized features.Plants can continue to grow throughout the life of the plant.Local conditions as well as genetic factors affect the size of the plant.Genetic factors, food intake, and interactions with other organisms are some of the factors that control the growth of an animal.For more specifics about grade level, see LS3.A.By the end of grade 12.In multicellular organisms individual cells grow and divide, allowing the organisms to grow.The organisms begins as a single cell that divides into many cells, with each parent cell passing the same genetic material to both daughter cells.Different genes are activated or deleted by small differences in the environment when an embryo's cells are subdivisions.A complex organisms are composed of systems of tissues and organs that work together to meet the needs of the whole organisms.In sexual reproduction, a specialized type of cell division called meiosis occurs that results in the production of sex cells, such as gametes in animals.
There is a framework for K-12 science education.
As organisms progress from birth to old age, their characteristic structures, functions, and behaviors change in predictable ways.When organisms reach adulthood, they can reproduce and transfer their genetic information to their offspring.Plants may develop specialized structures and depend on animal behavior to accomplish reproduction, if they engage in behaviors that increase their chances for reproduction.Understanding how a single cell can give rise to a complex, multi-cellular organisms builds on the concepts of cell division and gene expression.Cell division is an essential part of multi-cellular organisms.The process of cell division involves passing genetic material from one cell to another.Many cells are produced by successful divisions.Although the genetic material in each of the cells is the same, small differences in the environment can cause cells to develop differently.The body can form specialized cells that perform different functions even though they are all descended from a single cell.The mechanisms by which a fertilized egg develops into a complex organisms are cell growth and differentiation.Sex cells, which contain only one member from each of the chromosomes in the parent cell, are produced in sexual reproduction when a specialized type of cell division called meiosis occurs.