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Biology 2B Ecosystems Populations and relationships.

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Presentation on theme: "Biology 2B Ecosystems Populations and relationships."— Presentation transcript:

1 Biology 2B Ecosystems Populations and relationships

2 Features of populations Distribution and abundance Abundance or size – how many in a population Density – the number of organisms per unit area Distribution – the location of individuals within an area Population composition Sex ratios – number of organisms of each sex Age structure – number of organisms of different ages Population fertility – the reproductive capacity of the females

3 Factors affecting populations Density independent Physical (abiotic) factors Rainfall Humidity Temperature Acidity Salinity Catastrophic events Flood Fire Drought Volcanic eruptions Earthquakes Tsunamis Density dependent (biotic factors) Food supply (abundance or distribution of prey species) - this becomes more critical as population size and density increases Disease - this is easier to spread as population size and density increases Parasites - these spread more easily as population size and density increases Competition - this becomes more critical as population size and density increases Predation (abundance or distribution of predator species) - this becomes more critical as population size and density decreases Anything that affects health, survival or reproductive success will affect populations

4 Abiotic factors – both aquatic and terrestrial FactorEffect on survivalMeasurement TemperatureTemperature affects cell activity – especially enzymes and reactions in the cell. At low temperatures, cellular reactions slow. As the temperature increases the rate of reactions increases. At extremely high temperatures, enzymes and structures can be damaged and the cell can die. If the cell freezes, ice crystals can burst the cell Thermometer LightLight is necessary for photosynthesis. It is affected by water depth and shade (eg trees). Light meter pH (soil or water)pH affects cell survival by altering proteins. This can damage cell membranes and enzymes in the cell. pH meter indicators Salinity (soil or water)Salinity affects water and ion movement into and out of cells. High salt conditions dehydrate cells, low salt conditions can cause cells to swell and burst Salinity meter Conductivity meters WindWind affects wave action in aquatic environments and humidity and water loss in terrestrial environment. Wind meter Anemometer

5 Abiotic factors – mainly aquatic FactorEffect on survivalMeasurement Wave actionWave action affects the amount of gases (oxygen and carbon dioxide) that can dissolve in the water. The greater the action, the more gases dissolve. Height in metre (swell) Water currentsThese affect the temperature of water at different levels. They can carry nutrients from estuaries and coasts to deeper water. Radar and infrared satellites BuoyancyThis is a measure of how easy it is to float. It is affected by salinity – the greater the salt content, the more buoyancy there is. ViscosityThis affects movement. The more viscous a material, the more effort is needed to move through it. TurbidityThis is a measure of small particles in the water (eg silt). High turbidity can reduce light penetration and interfere with gill function making it harder to survive. Secchi disc DepthThe deeper the water, the less light penetrates. The wavelength of light also varies – red penetrates the least far & violet the most. Sonar Plumb line GasesOxygen is needed for respiration, carbon dioxide is needed for photosynthesis Dissolved oxygen meter Chemical tests

6 Abiotic factors – mainly terrestrial FactorEffect on survivalMeasurement Amount of waterAll organisms need water to surviveRain gauge HumidityThis affects water loss from leaves and the effectiveness of sweating and panting (evaporative cooling) in animals Humidity meter Hygrometer Mineral salts (in soil)Plants need minerals to grow. Mineral salts affect salinitySalinity meter Chemical tests Soil typeThis is mainly determined by particle size, mineral salts and organic matter present. These affect water retention, fertility and the type of plants that will grow. Soil tests TopographyFeatures such as slope, hills, valleys affect water movement, soil formation or erosion, shade and altitude. All of these affect the growth of plants and the animals they can support. Inclinometers Mapping instruments AltitudeHeight above sea levels affects oxygen and carbon dioxide levels. Soil quality is also generally less at higher altitudes. Mapping instruments

7 Biotic factors – role in ecosystem Autotroph – makes its own food Producer – provides energy to a food chain by photosynthesis (using light to convert carbon dioxide and water into sugars) or chemosynthesis (using chemical reactions to make energy or organic compounds) Heterotroph can not make its own food, so must eat other organisms Consumer – gains its energy by eating other organisms Decomposer – gains its energy by feeding on dead or decaying living matter

8 Biotic factors – feeding relationships Herbivore – eats plants Carnivore – eats animals Detrivore – eats dead or decaying matter Saprophyte – eats dead or decaying matter Predator – animal that eats another Prey – animal species eaten by predator Parasite – lives or feeds in or on a host without killing it Host – organism that a parasite feeds on

9 Associations and relationships RelationshipIs beneficial toHas no effect onCauses harm to Predator-preyPredatorPrey CompetitionBoth InhibitionOne SymbiosisOne or both MutualismBoth CommensualismOne ParasitismParasiteHost AmensualismOne CollaborationBoth DiseasePathogenHost

10 Associations and relationships 2 Predator – prey – predators feed on prey Numbers of predators depend on number of prey There are usually more prey than predators A rise in prey numbers leads to a rise in predator numbers A fall in prey numbers leads to a fall in predator numbers The change in predator numbers follows the change in prey numbers The lag times in rise and fall depend on the speed of reproduction of both species Parasite – host and Disease – host relationships show the same pattern Usually parasites and disease organisms (pathogens) are smaller than their hosts, so host numbers may be smaller than numbers of the parasite or disease organisms

11 Associations and relationships 3 Competition – rivalry between two organisms/species for the same resources – both are harmed Inhibition or antibiosis – one organism directly hinders the growth of another Amensalism – one organism is harmed, but the other is not benefited or harmed itself

12 Biotic factors – associations Symbiosis – one or both species benefit o Mutualism – both species benefit and both need each other eg lichen, pollination o Commensalism – one species benefits and the other is unaffected eg epiphytic ferns o Parasitism – one organism benefits and the other is harmed Collaboration - working together so both benefit but they can work without each other eg herbivores herding together so it is easier to avoid predators, seed dispersal


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