1.1 characteristics of living organisms

• Faeces


  Remains of substances not absorbed during digestion
• Sensitivity


  The ability of an organism to detect and respond to stimuli in its surroundings
• Responding to the environment around them gives an organism the best chances of survival
• Nervous system


  • Provides a complex system of receptors, neurones and effectors which detect and respond to different stimuli using electrical impulses
• Endocrine system


  • Allows a response to stimuli using chemical messengers, which travel in the blood, called hormones
• The nervous system and endocrine system allow humans to respond to their environment
• Geotropism


  A plant's response to gravity which causes the roots to grow down into the soil
• Phototropism


  A plant's response to light which causes shoots to grow towards sunlight
• Phototropism and geotropism allow plants to respond to their environment
• Movement


  An action by an organism causing a change of position or place
• Plants cannot move from place to place but can change their orientation
• Sunflowers track the sun and so change their orientation throughout the day
• Homeostasis


  The control of an organism's internal environment to keep conditions within required limits
• Thermoregulation


  The control of body temperature
• The optimum human body temperature is 37°C
• If body temperature increases e.g. during exercise, mechanisms for control will be initiated to return the temperature back to the optimum
• Mechanisms for thermoregulation include sweating or vasodilation
• Other homeostatic mechanisms in humans include glucoregulation (control of blood glucose levels) and osmoregulation (control of water levels)
• Transpiration


  The process plants use to maintain a suitable temperature by evaporation of water from the stomata on the underside of the leaves, leading to heat loss
• Plants maintain an optimum temperature through transpiration
• Reproduction


  The process that leads to the production of more of the same kind of organism
• Reproduction is fundamental to the survival of a population and ultimately, the species
• Sexual reproduction


  The fusion of male and female gametes to form a zygote that contains DNA from both parents
• Asexual reproduction


  Cells or whole organisms can reproduce without the fusion of gametes, producing an exact clone of the parent
• Mitosis


  An example of asexual reproduction where an exact copy of the parent cell is produced
• Growth


  A permanent increase in size
• In animals, an individual grows larger between the zygote and adult stage with changes in proportion or shape
• In plants, an individual grows larger throughout their whole life with new shoots, leaves, branches etc forming year after year