Gravitational Biology is the study of the effects gravity has on living organisms. Gravitation is a natural Phenomenon by which objects with Mass attract one another Life is a state that distinguishes Organisms from non-living objects such as non-life and dead organisms being manifested by growth through Metabolism Throughout the history of the Earth life has evolved to survive changing conditions, such as changes in the climate and habitat. eVolution is the third Album by eLDee, it was due to be released in 2008 Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of A habitat (which is Latin for "it inhabits" is an Ecological or environmental area that is inhabited by a particular Species. The only constant factor in evolution since life first began on Earth is the force of gravity. In Physics, a force is whatever can cause an object with Mass to Accelerate. As a consequence, all biological processes are accustomed to the ever-present force of gravity and even small variations in this force can have significant impact on the health and function of organisms. A biological process is a process of a living Organism (either plant or animal ^[1]

Contents 1 Gravity and Life on Earth 1.1 Plant use of Gravity 1.2 Animal Struggles with Gravity 2 Gravity and Life Elsewhere 2.1 Recent experiments 3 See also 4 References

Gravity and Life on Earth

The force of gravity on the surface of the Earth, normally denoted g, has remained constant in both direction and magnitude since the formation of the planet. Standard gravity, usually denoted by g 0 or g n is the nominal acceleration due to gravity at the Earth's surface at sea level As a result, both plant and animal life have evolved to rely upon and cope with it in various ways. Plants are living Organisms belonging to the kingdom Plantae.

Plant use of Gravity

Main article: Gravitropism

Plant tropisms are directional movements of a plant with respect to a directional stimulus. Gravitropism ''geotropism'' is a turning or growth movement by a Plant or Fungus in response to Gravity. A tropism (from Greek tropos, to turn is a biological Phenomenon, indicating growth or turning movement of a biological Organism, usually a plant One such tropism is Gravitropism, or the growth or movement of a plant with respect to gravity. Gravitropism ''geotropism'' is a turning or growth movement by a Plant or Fungus in response to Gravity. Plant roots grow towards the pull of gravity and away from sunlight, and shoots and stems grow against the pull of gravity and towards sunlight.

Animal Struggles with Gravity

Gravity has had an effect on the development of animal life since the first single-celled organism. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually The size of single biological cells is inversely proportional to the strength of the gravitational field exerted on the cell. This article is about proportionality the mathematical relation That is, in stronger gravitational fields the size of cells decreases, and in weaker gravitational fields the size of cells increases. Gravity is thus a limiting factor in the growth of individual cells.

Cells which were naturally larger than gravity alone would allow for had to develop means to protect against internal sedimentation. Several of these methods are based upon protoplasmic motion, thin and elongated shape of the cell body, increased cytoplasmic viscosity, and a reduced range of specific gravity of cell components relative to the ground-plasma. Protoplasm is the living contents of a cell that are surrounded by a Plasma membrane. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. Specific gravity is defined as the ratio of the Density of a given solid or liquid substance to the density of water at a specific temperature and pressure typically ^[2]

The effects of gravity on many-celled organisms is even more drastic. During the period when animals first evolved to survive on land some method of directed locomotion and thus a form of inner skeleton or outer skeleton would have been required to cope with the increase in the force of gravity due to the weakened upward force of buoyancy. An endoskeleton is an internal support structure of an Animal. An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is Prior to this point, most lifeforms were small and had a worm- or jellyfish-like appearance, and without this evolutionary step would not have been able to maintain their form or move on land.

In larger terrestrial vertebrates gravitational forces influence musculoskeletal systems, fluid distribution, and hydrodynamics of the circulation. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes The musculoskeletal system (also known as the locomotor system is an organ system that gives Animals the ability to physically move using the Muscles and Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion This is an article about the rock music band "Circulatory System"

Gravity and Life Elsewhere

Every day the realization of space habitation becomes closer, and even today space stations exist and are home to long-term, though not yet permanent residents. A space habitat, also called space colony, orbital colony, space city, or space settlement is a Space station intended as a A space station is an artificial structure designed for Humans to live in Outer space. Because of this there is a growing scientific interest in how changes in the gravitational field influence different aspects of the physiology of living organisms, especially mammals since these results can normally be closely related to the expected effects on humans. Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands All current research in this field can be classified into two groups. ^[3]

The first group consists of the experiments that involve gravitational fields of less than one g, termed hypogravity. All space travel is done in hypogravity, and effective gravitational fields on any space station without Artificial gravity are on the order of hypogravity, and therefore the understanding of the effects of hypogravity on the human body is necessary for prolonged space travel and colonization. Spaceflight is the use of Space technology to fly a Spacecraft into and through Outer space. Artificial gravity is a simulation of gravity in Outer space or Free-fall.

The second group consist of those involving gravitational fields of more than one g, termed hypergravity. For brief periods furing take-off and landing of space craft astronauts are under the influence of hypergravity. An astronaut or cosmonaut (космона́вт) is a person trained Understanding the effects of hypergravity are also necessary if colonization of planets larger than the Earth is ever to take place.

Recent experiments

Recent experiments have proven that alterations in metabolism, immune cell function, cell division, and cell attachment all occur in the hypogravity of space. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. For example, after a matter of days in microgravity (< 10^-3 g), human immune cells were unable to differentiate into mature cells. Weightlessness is a phenomenon experienced by people during Free-fall. In Developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized Cell type. One of the large implications of this is that if certain cells cannot differentiate in space, organisms may not be able to reproduce successfully after exposure to zero gravity.

Scientists believe that the stress associated with space flight is responsible for the inability of some cells to differentiate. These stresses can alter metabolic activities and can disturb the chemical processes in living organisms. A specific example would be that of bone cell growth. Microgravity impedes the development of bone cells. Bone cells must attach themselves to something shortly after development and will die if they can not. Without the downward pull of a gravitational force on these bone cells, they float around randomly and eventually die off. This suggests that the direction of gravity may give the cells clues as to where to attach themselves.

See also

• Astrobiology
• Cell biology
• Gravitation
• Space colonization
• Space exploration

References

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