Secondary Science - Growth

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Growth P-prim and Driver Article Summary

By Bob Fiero

Growth refers to an increase in some quantity over time.

The quantity can be:

Physical (e.g., growth in height, growth in an amount of money) Abstract (e.g., a system becoming more complex, an organism becoming more mature). It can also refer to the mode of growth, i.e. numeric models for describing how much a particular quantity grows over time.

According to Driver's article most students/novices have conceive of growth to mean a wide variety of things but do think of if it as a criterion for anything to be considered a life form or as evidence of life in said object. In surveys quoted she mentioned she said that people reported that growth entailed biochemical reactions and pathways, cell mitosis and differentiation and macroscopic growth of body parts. For those age 9+ physiological events, measures such as size, developmental stage (maturity) and just getting larger we mentioned frequently but very little reference to change in weight or mass. Preschoolers generally mentioned getting bigger but would say getting big related to age too but interestingly they felt growing laring was intentional and not a natural involunarty phenomenon.

Driver in reference to various studies quoted that children do not appear to recognize that the substances taken in are the material basis for growth, becoming transformed and incorporated into the body and thus making it bigger. Also they would have misconceptions such as plants get the materials for their bodies through the absorption of nutrients through the soil and did not recognize the need for light and carbon dioxide in combination with water through the process of photosynthesis to make the materials, such as glucose, to produce the basic building material for themselves as autotrophs. In relation to this, in a study by Russel and Watt[1], found children believed that the new plant material emerged from the bean seed.

Briefly discussed notion of development indicated children very that all the organs of animals are already preformed in the egg and gradually emerge as the organism grows larger and mentioned nothing about gene regulation of growth and development or heredity.

Below is a brief, diverse and interestingly vague outline of what growth, and somewhat, development is defined in the literature:

Growth can be at the cellular level/scale. The term cell growth is used in the contexts of cell development and cell division (reproduction). When used in the context of cell division, it refers to growth of cell populations, where one cell (the "mother cell") grows and divides to produce two "daughter cells".

Growth can mean developmental maturing of mind and body. For example, Erikson's stages of psychosocial development as articulated by Erik Erikson explain eight stages through which a healthily developing human should pass from infancy to late adulthood. In each stage the person confronts, and hopefully masters, new challenges. Each stage builds on the successful completion of earlier stages. The challenges of stages not successfully completed may be expected to reappear as problems in the future.

The stages: 1.1 Infancy: Trust vs. Mistrust (0 to 1 year) 1.2 Toddler: Autonomy vs. Shame & Doubt (2 to 3 years) 1.3 Preschool: Initiative vs. Guilt (4 to 6 years) 1.4 Childhood: Industry vs. Inferiority (7 to 12 years) 1.5 Adolescence: Identity vs. Role Confusion (13 to 19 years) 1.6 Young Adulthood: Intimacy vs. Isolation (20 to 34 years) 1.7 Middle Adulthood: Generativity vs. Stagnation (35 to 65 years) 1.7.1 Central tasks of Middle Adulthood 1.8 Senior: Integrity vs. Despair (65 years onwards)

Biological development

Human development is the process of growing to maturity. In biological terms, this entails growth from a one-celled zygote to an adult human being.

Sperm fertilizing an eggDevelopment begins with fertilization, the process by which the male gamete, the sperm cell, and the female gamete, the egg, fuse to produce a zygote. In pregnancy the 3 stages are commonly referred as Z.E.F. - meaning Zygote, Embryo, Fetus.

In medicine, the beginning of pregnancy is the instant a sperm cell enters an ovum and forms a viable zygote. Recently, in western medicine, pregnancy is defined as beginning when a zygote becomes implanted in a woman's uterus. This occurs when the zygote then becomes embedded into the endometrium (lining of the uterus) where it forms a placenta, for the purpose of receiving essential nutrients through the uterus wall. The umbilical cord in a newborn child helps get the nutrients to the child and helps get rid of the waste from the child.

The zygote undergoes rapid cell divisions with no significant growth (a process known as cleavage) and cellular differentiation, leading to development of an embryo. Child birth is the process in which the baby is born. Age is defined relative to this event in most cultures.

Child (birth - puberty) Neonate (newborn) (0-30 days) Infant (baby) (1 month-1 year) Toddler (1-4) Play age (3 - 6 years) Primary school age (also called prepubescence) (4-12) Elementary school age (also called middle childhood) (4-8) Preadolescence (preteen, or late childhood. The child in this and the previous phase are called schoolchild (schoolboy or schoolgirl), when still of primary school age.) (10-12) Adolescence and puberty (12-20) Peripuberty (8-10 until 15-17) Adult (21-death) Early adulthood (21-39) Middle adulthood (40-59) Advanced adult/Senior citizen (60+) Death (occurs at various ages, depending on person) Decomposition (breakdown of the body after death)

Also sometimes used are terms that specify one's age in numbers, such as: Child (0-12) Teenager (13-19) Twentysomething (20-29) Thirtysomething (30-39) Fortysomething (40-49) (formerly also Quadragenarian, rarely used since 1980) Quinquagenarian (50-59) Sexagenarian (60-69) Septuagenarian (70-79) Octogenarian (80-89) Nonagenarian (90-99) Centenarian (100-109) Supercentenarian (110+)

Plant growth Further information: Meristem, Cellular differentiation, Morphogenesis, and Plant embryogenesis A vascular plant begins from a single celled zygote, formed by fertilisation of an egg cell by a sperm cell. From that point, it begins to divide to form a plant embryo through the process of embryogenesis. As this happens, the resulting cells will organize so that one end becomes the first root, while the other end forms the tip of the shoot. In seed plants, the embryo will develop one or more "seed leaves" (cotyledons). By the end of embryogenesis, the young plant will have all the parts necessary to begin in its life.

Once the embryo germinates from its seed or parent plant, it begins to produce additional organs (leaves, stems, and roots) through the process of organogenesis. New roots grow from root meristems located at the tip of the root, and new stems and leaves grow from shoot meristems located at the tip of the shoot. Branching occurs when small clumps of cells left behind by the meristem, and which have not yet undergone cellular differentiation to form a specialized tissue, begin to grow as the tip of a new root or shoot. Growth from any such meristem at the tip of a root or shoot is termed primary growth and results in the lengthening of that root or shoot. Secondary growth results in widening of a root or shoot from divisions of cells in a cambium.

In addition to growth by cell division, a plant may grow through cell elongation. This occurs when individual cells or groups of cells grow longer. Not all plant cells will grow to the same length. When cells on one side of a stem grow longer and faster than cells on the other side, the stem will bend to the side of the slower growing cells as a result.

1. Russel, T. and Watt, D. (1989) Students'conceptions of photosynthesis and food for plants, Report from the Institute For research on Teaching, Michigan State University, East Lansing, Michigan.