Bio Notes Ch1

BIOLOGY NOTES
Chapter 1: A Local Ecosystem
1. The distribution, diversity and numbers of plants and animals found in ecosystems are determined by biotic and abiotic factors
Compare the abiotic characteristics of aquatic and terrestrial environments
Abiotic factor Aquatic environment Terrestrial environment
Viscosity (density)
Resistance to movement through a medium Difficult to move because water is more viscose than air Easier to move because are is less viscose than water
Buoyancy (no air)
Upthrust (upward pressure) or support Organisms that live in water experience an upward force; water is dense; water helps support organisms Organisms that live in air do not experience an upthrust; they need support to function
Temperature
Varies daily with seasons and with latitude Little difference in temperature except in a very small and shallow body of water Wide range of temperature at high altitudes
Availability of gases, water and ions
a) Gases
Oxygen for respiration and carbon dioxide for photosynthesis
Oxygen availability is lower in water; carbon dioxide availability is higher than oxygen Organisms able to get enough oxygen (20% of air is O₂), except on high mountains
b) Water
Living organisms are 60-90% water In freshwater, nutrients would sustain life. In saltwater, water leaves cells, leading to thirst and dehydration
Amount of rain and where an organism lives determines water availability
c) Ions
Charged particles In saltwater, dissolved ions are freely available. In freshwater, ions are lower in concentration Amount of ions available depends of whether soil is fertile or poor
Light penetration
The sun is the source of light energy Little light penetrates muddy, deep water Plentiful light is available in summer, except in dark areas (caves or rainforests)
Pressure variation Organisms exposed to more pressure at greater depths Less pressure on mountains
Physical forces Storms cause high tides, strong currents, huge waves and strong... [continues]

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