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The Biosphere Investigating an Ecosystem
Ecosystem Made up of living and non living parts POND WOODLAND SOIL MOOR Abiotic Food availability Predation  Temperature ...
 
Quadrat Estimates the abundance of non moving  organisms Throw randomly Count the number of squares an organism is found i...
LMM Can measure both  light intensity and  moisture content of a particular area Errors ? Shadow  Read wrong scale Stone  ...
Pitfall  Trap Alcohol (if you  The samples  Killed) Pitfall Trap
More
 
Results Quadrat  1  2  3  4  5  6  7  8  9  10 Light Intensity A  B  C  D  E  F  G  H  H  H Soil moisture 3  2  3  1  4  3...
Tullgren
 
 
Ecosystems and Energy Flow 3
What is an ecosystem? <ul><li>An ecosystem is all the animals and the plants in a habitat, together with their environment...
Ecosystems <ul><li>Made up of a number of different habitats sharing the same environment. E.g. a desert. </li></ul><ul><u...
What is a habitat ?
<ul><li>A  habitat  is the place where living things live. </li></ul><ul><li>It is more than just a home it includes the w...
People and their habitats <ul><li>People can live all over the world. </li></ul>
<ul><li>We can do this because we are able to build homes for different conditions.  </li></ul>
Also we can change our clothes to best suit the temperature around us. White clothes reflect the heat Animal skin and fur ...
Animals and plants <ul><li>Most plants and animals are specially adapted to survive in a  particular  habitat. </li></ul><...
Some examples of adaption
<ul><li>All birds have similar characteristics. </li></ul><ul><li>But many water birds have features that are different fr...
<ul><li>Some animals are  camouflaged  to blend in with their surroundings. </li></ul><ul><li>This keeps them safe as it i...
<ul><li>Aquatic animals have streamlined bodies to move more easliy in the water. </li></ul>
<ul><li>These animals have adapted to live in the hot climate of the desert. </li></ul>Camels store water in their humps. ...
<ul><li>These animals have adapted to be more suited to cold temperatures. </li></ul>Layers of fat keep the seals body war...
How do changes in the environment affect organisms?
Living things are adapted to daily changes in their habitat…………….
Daily changes <ul><li>Flowers open and close </li></ul>
Daily changes <ul><li>Sea anemones pull in their tentacles when the tide goes out to stop them drying out. </li></ul>
Living things are adapted to seasonal changes in their habitat
Seasonal changes in a garden <ul><li>A garden in  </li></ul><ul><li>the summer </li></ul>
A woodland <ul><li>A woodland  </li></ul><ul><li>in spring </li></ul>
The Arctic
The Seashore
Some plants store their food for winter underground in their roots and stems.
<ul><li>Squirrels store foods like nuts in the autumn to eat during the winter when there is not much food around. </li></ul>
Some animals like tortoises, hedgehogs and bears, cannot store food to keep them warm. Instead they go to sleep in a warm ...
Energy Flow in a Habitat Plants trap energy converting it to biomass. Producers Plant biomass eaten by animals Primary Con...
Terminology to Learn <ul><li>Herbivore  - animals that eat only plants. </li></ul><ul><li>Carnivore  - animals that eat on...
Trophic levels
What does this food chain show? <ul><li>The plant  is eaten by   the slug. </li></ul><ul><li>The slug   is eaten by   the ...
Food Web Write out four food chains found in the food web .
How do Organisms Interact? <ul><li>What happens to the locust population if  </li></ul><ul><li>the slugs die out? </li></u...
Pyramid of Numbers This is another way of showing a food chain. <ul><li>Why do the numbers drop as  </li></ul><ul><li>you ...
Pyramids of Numbers - examples 5000 Dandelions 100 Rabbits 1000 Pea Pods 100 Slugs 10 Frogs 1 Fox 1 Bird
Pyramid of Numbers 1 Partridge Now draw the pyramids of numbers for these food chains. 1 Pear  Tree 3000 Greenfly 1000 Lad...
Pyramids of Numbers - examples 2 5000 Dandelions 100 Rabbits 3000 Greenfly 1000 Ladybirds 500 Fleas 1 Tree 1 Partridge 1 Fox
Pyramid of Biomass Biomass is how much dry mass is present in each trophic level. For this reason Biomass Pyramids always ...
Energy flow <ul><li>Each animal in the food chain eats another animal or a plant in order to gain energy. </li></ul><ul><l...
Pyramid of Energy transfer
Where does the energy come from? <ul><ul><li>The Sun </li></ul></ul><ul><li>In every ecosystem, Energy is trapped and stor...
Energy flow in a food chain <ul><li>Sun </li></ul><ul><ul><li>98% energy lost </li></ul></ul><ul><ul><li>Producer </li></u...
Energy flow through Producers <ul><li>Most of the sunlight that falls on leaves is not absorbed and used </li></ul><ul><li...
What is this chemical energy used for? <ul><li>For respiration and growth </li></ul><ul><li>When the plant grows, its biom...
Energy flow through a  green  plant <ul><li>Released in  primary </li></ul><ul><li>Respiration consumers  </li></ul><ul><l...
What happens to the other 90%? <ul><li>Only 10% of the stored energy in the deer is transferred to the lion </li></ul>
Write down what happens to the missing 90% of the energy in a deer ( Kudu) that is not transferred to the lion.
What are the units? <ul><li>kJ/m ²/yr </li></ul><ul><li>Unit of energy/ area/time </li></ul><ul><li>(kilo Joules per metre...
The reasons for the inefficiency of this energy transfer are:- <ul><li>Some plant material passes out of the body of the h...
Carnivores are able to achieve 20% efficiency.  Why? <ul><li>20% of the herbivores biomass ends up as the carnivores bioma...
Energy Flow in a food chain <ul><li>Some people eat kudu. </li></ul><ul><li>What is the food chain? </li></ul><ul><li>Gras...
Where does all the energy go? <ul><li>Plants convert a small % of light energy into glucose (biomass)’ </li></ul><ul><li>T...
Match the words and phrases. A food chain shows Most food chains start with Plants are Animals are  Animals that hunt and ...
<ul><li>A  population  is a group of organisms of the same species living in the same place at the same time </li></ul><ul...
Populations <ul><li>Properties of populations </li></ul><ul><ul><li>Birth rate; count number of live births in a given per...
Population Growth The growth rate of a population is the increase in the number of individuals over time. Exponential grow...
Generation # of bacteria time 1 1 0 2 2 15min 3 4 30min 4 8 45min 5 16 1hr 6 32 75min 7 64 90min 8 128 105min 9 256 2hrs 1...
<ul><li>But can a population continue to grow at this rate?  NO </li></ul><ul><li>Limiting factors will control population...
A Population <ul><li>Group of organisms of the same species living in the same place at the same time </li></ul><ul><li>In...
Population Growth <ul><li>Since each organism of a population is governed by the selfish gene, populations tend to grow. <...
Population Growth 2 <ul><li>Resources are never unlimited, though.  </li></ul><ul><li>As population rises, resources decli...
Reindeer
Population Growth 3 <ul><li>More often what happens is that the resources slowly decrease, the growth rate slowly decrease...
Growth Rate Limiting Factors (affecting birth or mortality rates)   <ul><ul><li>Predation </li></ul></ul><ul><ul><li>Incre...
Predator-Prey Cycles Control of Population Size
Lynx
Snowshoe Hare
Lynx cycle lags behind hare by 1-2 yrs.  Why?
What is the cause of these population changes? When hare numbers increase, 2 things happen: 1. Shortage of food for hares ...
Lynx  numbers  increase  when  Hare  numbers high, but if food for hares is low and predation is high…………………….. ………… soon ...
(1) Some  Lynxes  leave ( emigrate)  to where food is more plentiful. (2)  Lynxes  eat other prey when hare  numbers low. ...
Lower  Hare  numbers – vegetation starts to grow again  + Hares  have fewer  Lynx  to watch out for  + There is more veget...
Highest peaks always belong to  PREY Why? The predator is ALWAYS at a higher level in the pyramid of numbers Than the prey...
COMPETITION… <ul><li>Competition is the STRUGGLE FOR RESOURCES WHICH ARE IN SHORT SUPPLY </li></ul><ul><li>PLANTS compete ...
Where do decomposers come in? <ul><li>When living things die their bodies are broken down by decomposers so releasing the ...
An example of Fungi You know
The Nitrogen Cycle Nitrogen in the air Denitrifying bacteria Eating   Nitrates in the soil N 2  fixing bacteria waste NH 3...
…On pollution <ul><li>Pollutants may REDUCE the biodiversity in an ecosystem </li></ul><ul><li>Eg fossil fuels produce Sul...
Pollution and Biodiversity… <ul><li>If untreated sewage enters a river or lake it provides food for BACTERIA. </li></ul><u...
DO dissolved oxygen BOD biochemical oxygen demand
Oxygen Sag The oxygen decline and rise downstream from a point source is called the  oxygen sag.
The Biodiversity crisis <ul><li>Human activity can cause habitat destruction and pollution. </li></ul><ul><li>This contrib...
WHY IS BIODIVERSITY SO IMPORTANT ? <ul><li>FOOD….Eg fish from the North Sea </li></ul><ul><li>RAW-MATERIALS…such as timber...
Grazing and Biodiversity… <ul><li>Grassland is made up of a variety of plants </li></ul><ul><li>Some species grow quickly ...
Intensity of Grazing… <ul><li>LOW levels of unselective grazing allows the grasses to grow and out compete other less vigo...
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The Biosphere Extended

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Transcript of "The Biosphere Extended"

  1. 1. The Biosphere Investigating an Ecosystem
  2. 2. Ecosystem Made up of living and non living parts POND WOODLAND SOIL MOOR Abiotic Food availability Predation Temperature Light intensity Moisture Biotic
  3. 4. Quadrat Estimates the abundance of non moving organisms Throw randomly Count the number of squares an organism is found in Errors ? Non random throwing Counting the same organism over two squares Too few quadrats done
  4. 5. LMM Can measure both light intensity and moisture content of a particular area Errors ? Shadow Read wrong scale Stone Too few readings
  5. 6. Pitfall Trap Alcohol (if you The samples Killed) Pitfall Trap
  6. 7. More
  7. 9. Results Quadrat 1 2 3 4 5 6 7 8 9 10 Light Intensity A B C D E F G H H H Soil moisture 3 2 3 1 4 3 2 3 4 3 grass 6 8 8 10 15 20 23 25 25 25 Daisies 0 0 0 0 5 11 16 19 22 22 Sorrel 20 15 15 10 10 5 0 0 0 0
  8. 10. Tullgren
  9. 13. Ecosystems and Energy Flow 3
  10. 14. What is an ecosystem? <ul><li>An ecosystem is all the animals and the plants in a habitat, together with their environment. </li></ul><ul><li>An ecosystem provides everything that the animals and plants that live there need. </li></ul><ul><li>A rock pool is an ecosystem, and so is a forest or a lake. </li></ul>
  11. 15. Ecosystems <ul><li>Made up of a number of different habitats sharing the same environment. E.g. a desert. </li></ul><ul><ul><li>Habitat - a place where living things live. E.g. a pond. </li></ul></ul><ul><ul><li>Community - a group of populations living in a habitat. </li></ul></ul><ul><ul><li>Population - a group of organisms of the same species. </li></ul></ul>
  12. 16. What is a habitat ?
  13. 17. <ul><li>A habitat is the place where living things live. </li></ul><ul><li>It is more than just a home it includes the whole surrounding area. </li></ul><ul><li>The habitat provides the animal or plant with food or shelter . </li></ul>
  14. 18. People and their habitats <ul><li>People can live all over the world. </li></ul>
  15. 19. <ul><li>We can do this because we are able to build homes for different conditions. </li></ul>
  16. 20. Also we can change our clothes to best suit the temperature around us. White clothes reflect the heat Animal skin and fur act as insulators and keep heat in.
  17. 21. Animals and plants <ul><li>Most plants and animals are specially adapted to survive in a particular habitat. </li></ul><ul><li>They have developed special features to suit the demands of their environment. </li></ul><ul><li>This is called adaption . </li></ul>
  18. 22. Some examples of adaption
  19. 23. <ul><li>All birds have similar characteristics. </li></ul><ul><li>But many water birds have features that are different from those birds live on land. </li></ul>Long legs are good for wading These wings act as flippers Webbed feet for swimming
  20. 24. <ul><li>Some animals are camouflaged to blend in with their surroundings. </li></ul><ul><li>This keeps them safe as it is more difficult for other animals to see them or catch them for food. </li></ul>These zebra could easily be mistaken for bushes from a distance. This lizards skin is so similar to the rock colour. This lion blends in well with the grassy background.
  21. 25. <ul><li>Aquatic animals have streamlined bodies to move more easliy in the water. </li></ul>
  22. 26. <ul><li>These animals have adapted to live in the hot climate of the desert. </li></ul>Camels store water in their humps. Ostriches have long eyelashes to keep out the sand. Snakes glide across the hot sands and can shed their skin
  23. 27. <ul><li>These animals have adapted to be more suited to cold temperatures. </li></ul>Layers of fat keep the seals body warm, and small ears stop heat loss. Polar bears are kept warm by their body fat. Deer have a warm layer of fur.
  24. 28. How do changes in the environment affect organisms?
  25. 29. Living things are adapted to daily changes in their habitat…………….
  26. 30. Daily changes <ul><li>Flowers open and close </li></ul>
  27. 31. Daily changes <ul><li>Sea anemones pull in their tentacles when the tide goes out to stop them drying out. </li></ul>
  28. 32. Living things are adapted to seasonal changes in their habitat
  29. 33. Seasonal changes in a garden <ul><li>A garden in </li></ul><ul><li>the summer </li></ul>
  30. 34. A woodland <ul><li>A woodland </li></ul><ul><li>in spring </li></ul>
  31. 35. The Arctic
  32. 36. The Seashore
  33. 37. Some plants store their food for winter underground in their roots and stems.
  34. 38. <ul><li>Squirrels store foods like nuts in the autumn to eat during the winter when there is not much food around. </li></ul>
  35. 39. Some animals like tortoises, hedgehogs and bears, cannot store food to keep them warm. Instead they go to sleep in a warm sheltered place, such as under pile of old leaves or inside an old tree trunk. This is called hibernation.
  36. 40. Energy Flow in a Habitat Plants trap energy converting it to biomass. Producers Plant biomass eaten by animals Primary Consumers Larger animals eat animals that eat plants Secondary Consumers All energy initially comes from the sun as light energy
  37. 41. Terminology to Learn <ul><li>Herbivore - animals that eat only plants. </li></ul><ul><li>Carnivore - animals that eat only animals. </li></ul><ul><li>Omnivore - animals that eat plants and animals. </li></ul><ul><li>Top Carnivore - animals not eaten by anything else. </li></ul><ul><li>Decomposer - organisms that live on dead material. </li></ul><ul><li>Trophic Levels - each step along a food chain. </li></ul>
  38. 42. Trophic levels
  39. 43. What does this food chain show? <ul><li>The plant is eaten by the slug. </li></ul><ul><li>The slug is eaten by the frog. </li></ul><ul><li>The frog is eaten by the heron. </li></ul>
  40. 44. Food Web Write out four food chains found in the food web .
  41. 45. How do Organisms Interact? <ul><li>What happens to the locust population if </li></ul><ul><li>the slugs die out? </li></ul><ul><li>What happens to the plant population? </li></ul>
  42. 46. Pyramid of Numbers This is another way of showing a food chain. <ul><li>Why do the numbers drop as </li></ul><ul><li>you go up the trophic levels? </li></ul><ul><li>Draw the pyramid of numbers </li></ul><ul><li>for these food chains. </li></ul>5000 Dandelions 100 Rabbits 1 Fox 1000 Pea Pods 100 Slugs 10 Frogs 1 Bird
  43. 47. Pyramids of Numbers - examples 5000 Dandelions 100 Rabbits 1000 Pea Pods 100 Slugs 10 Frogs 1 Fox 1 Bird
  44. 48. Pyramid of Numbers 1 Partridge Now draw the pyramids of numbers for these food chains. 1 Pear Tree 3000 Greenfly 1000 Ladybirds 5000 Dandelions 100 Rabbits 1 Fox 500 Fleas
  45. 49. Pyramids of Numbers - examples 2 5000 Dandelions 100 Rabbits 3000 Greenfly 1000 Ladybirds 500 Fleas 1 Tree 1 Partridge 1 Fox
  46. 50. Pyramid of Biomass Biomass is how much dry mass is present in each trophic level. For this reason Biomass Pyramids always look the same .
  47. 51. Energy flow <ul><li>Each animal in the food chain eats another animal or a plant in order to gain energy. </li></ul><ul><li>The energy flow in the ecosystem keeps all of the animals alive. </li></ul>
  48. 52. Pyramid of Energy transfer
  49. 53. Where does the energy come from? <ul><ul><li>The Sun </li></ul></ul><ul><li>In every ecosystem, Energy is trapped and stored by the plants (primary producers). </li></ul><ul><li>Some energy is always lost in the transfer of energy between trophic levels </li></ul><ul><li>Ecologists have calculated 10% of energy available in a trophic level is taken up by the level above </li></ul>
  50. 54. Energy flow in a food chain <ul><li>Sun </li></ul><ul><ul><li>98% energy lost </li></ul></ul><ul><ul><li>Producer </li></ul></ul><ul><ul><li> 90% energy lost </li></ul></ul><ul><ul><li>Primary consumer </li></ul></ul><ul><ul><li> 90% energy lost </li></ul></ul><ul><ul><li>Secondary consumer </li></ul></ul><ul><ul><li> 90% energy lost </li></ul></ul><ul><ul><li>Tertiary consumer </li></ul></ul>
  51. 55. Energy flow through Producers <ul><li>Most of the sunlight that falls on leaves is not absorbed and used </li></ul><ul><li>What happens? </li></ul><ul><li>Some is reflected from the leaf’s surface </li></ul><ul><li>Some passes straight through the leaf </li></ul><ul><li>Only part of the light is useful and can be absorbed by chlorophyll </li></ul><ul><li>The overall efficiency of energy transfer during photosynthesis is less than 10% </li></ul><ul><li>So only about 8% of sunlight energy reaching the plant is transferred into useful chemical energy. </li></ul>
  52. 56. What is this chemical energy used for? <ul><li>For respiration and growth </li></ul><ul><li>When the plant grows, its biomass will increase. This will provide food energy for herbivores. </li></ul><ul><li>It may be transferred between trophic levels from producers to primary consumers. </li></ul><ul><li>Some food energy may be transferred to decomposers. </li></ul><ul><li>When leaves are shed, fruit and seeds are dispersed and when the plant itself dies. </li></ul><ul><li>Decomposers eat the dead plant tissues to get energy. </li></ul>
  53. 57. Energy flow through a green plant <ul><li>Released in primary </li></ul><ul><li>Respiration consumers </li></ul><ul><li>Producer decomposers </li></ul><ul><li>energy input </li></ul><ul><li>SUN </li></ul>
  54. 58. What happens to the other 90%? <ul><li>Only 10% of the stored energy in the deer is transferred to the lion </li></ul>
  55. 59. Write down what happens to the missing 90% of the energy in a deer ( Kudu) that is not transferred to the lion.
  56. 60. What are the units? <ul><li>kJ/m ²/yr </li></ul><ul><li>Unit of energy/ area/time </li></ul><ul><li>(kilo Joules per metre squared per year.) </li></ul><ul><li>Important to remember that pyramids of energy transfer are NEVER inverted. </li></ul>
  57. 61. The reasons for the inefficiency of this energy transfer are:- <ul><li>Some plant material passes out of the body of the herbivore as faeces without being digested. </li></ul><ul><li>A lot of energy is used in respiration. </li></ul><ul><li>Some energy passes to decomposers in dead remains. </li></ul>
  58. 62. Carnivores are able to achieve 20% efficiency. Why? <ul><li>20% of the herbivores biomass ends up as the carnivores biomass. </li></ul><ul><li>This is possible because proteins are more efficiently digested than are carbohydrates. </li></ul>
  59. 63. Energy Flow in a food chain <ul><li>Some people eat kudu. </li></ul><ul><li>What is the food chain? </li></ul><ul><li>Grass Kudu human </li></ul><ul><li>Of the 1000 000kJ of Energy which falls on one square metre of grass in a year only 100kJ available for humans. </li></ul>
  60. 64. Where does all the energy go? <ul><li>Plants convert a small % of light energy into glucose (biomass)’ </li></ul><ul><li>The energy works its way through the food chain, </li></ul><ul><li>but trophic level 2 only takes 10% of total energy of trophic level 1 </li></ul><ul><li>The 90% of energy lost is used in staying alive: </li></ul><ul><li>HEAT </li></ul><ul><li>Excretory products </li></ul><ul><ul><li>movement </li></ul></ul><ul><ul><li>life processes </li></ul></ul>This explains why pyramids of biomass get smaller as they go up and why food chains are rarely more than 4 links long .
  61. 65. Match the words and phrases. A food chain shows Most food chains start with Plants are Animals are Animals that hunt and eat others are called Animals that are caught and eaten are called producers consumers predators prey a green plant what is eaten by what
  62. 66. <ul><li>A population is a group of organisms of the same species living in the same place at the same time </li></ul><ul><li>Millions of different populations all evolving according to their own self interest in a particular environment. </li></ul><ul><li>But each population is a part of the environment of its neighbors, so any evolutionary change has a ripple effect . </li></ul>Populations
  63. 67. Populations <ul><li>Properties of populations </li></ul><ul><ul><li>Birth rate; count number of live births in a given period. </li></ul></ul><ul><ul><li>Death rate; count number of deaths in a given time period. </li></ul></ul><ul><ul><li>Growth rate; balance between birth/death rate. For population to grow, birth rate must exceed death rate. </li></ul></ul><ul><ul><li>Age structure, Density,and dispersion are also factors </li></ul></ul>A population is a group of organisms of the same species living in the same place at the same time
  64. 68. Population Growth The growth rate of a population is the increase in the number of individuals over time. Exponential growth is when the number of individuals grows at a constant rate. Growing bacteria in a lab is a good example
  65. 69. Generation # of bacteria time 1 1 0 2 2 15min 3 4 30min 4 8 45min 5 16 1hr 6 32 75min 7 64 90min 8 128 105min 9 256 2hrs 10 512 11 1024 12 2048 13 4096 3hrs 14 8192 15 16,384 16 32,768 17 65,536 4hrs 18 131,072 19 262,144 20 524,288 21 1,048,576 5hrs
  66. 70. <ul><li>But can a population continue to grow at this rate? NO </li></ul><ul><li>Limiting factors will control population growth </li></ul><ul><li>Food shortages </li></ul><ul><li>Lack of space </li></ul><ul><li>Accumulation of own waste products </li></ul><ul><li>Lack of other resources like oxygen, living space etc. </li></ul>
  67. 71. A Population <ul><li>Group of organisms of the same species living in the same place at the same time </li></ul><ul><li>Individuals may come and go, but the population can remain the same </li></ul><ul><li>The Nakuru Flamingos each year, for Example </li></ul>
  68. 72. Population Growth <ul><li>Since each organism of a population is governed by the selfish gene, populations tend to grow. </li></ul><ul><li>If unlimited resources are present, growth will be exponential </li></ul><ul><li>It will proceed very quickly for rapidly reproducing organisms and more slowly for slowly reproducing ones </li></ul><ul><li>The curve, however, will always be a “J” curve or an exponential growth curve </li></ul>
  69. 73. Population Growth 2 <ul><li>Resources are never unlimited, though. </li></ul><ul><li>As population rises, resources decline. </li></ul><ul><li>If the growth is too rapid, resources are rapidly depleted and a population crash can occur </li></ul><ul><li>This pattern occurs often with many populations (including humans) </li></ul><ul><li>For example... </li></ul>Gypsy moth caterpillar
  70. 74. Reindeer
  71. 75. Population Growth 3 <ul><li>More often what happens is that the resources slowly decrease, the growth rate slowly decreases, and they meet. </li></ul><ul><li>This point that they oscillate around is the carrying capacity of the environment for that particular organism </li></ul><ul><li>So when would you “harvest” these individuals? (1,2,3,4,or 5) </li></ul>S - shaped curve
  72. 76. Growth Rate Limiting Factors (affecting birth or mortality rates) <ul><ul><li>Predation </li></ul></ul><ul><ul><li>Increased competition for scarce resources </li></ul></ul><ul><ul><li>Sickness </li></ul></ul><ul><ul><li>Others?... </li></ul></ul><ul><ul><li>Weather </li></ul></ul><ul><ul><ul><li>Ice Age </li></ul></ul></ul><ul><ul><ul><li>Global Warming </li></ul></ul></ul><ul><ul><ul><li>Flood </li></ul></ul></ul><ul><ul><ul><li>El Nino </li></ul></ul></ul><ul><ul><ul><li>Etc. </li></ul></ul></ul>Range of tolerance of environmental conditions is an important factor: temperature, light, salinity, nutrients, water etc
  73. 77. Predator-Prey Cycles Control of Population Size
  74. 78. Lynx
  75. 79. Snowshoe Hare
  76. 80. Lynx cycle lags behind hare by 1-2 yrs. Why?
  77. 81. What is the cause of these population changes? When hare numbers increase, 2 things happen: 1. Shortage of food for hares 2. Increase in Lynx number (predation)
  78. 82. Lynx numbers increase when Hare numbers high, but if food for hares is low and predation is high…………………….. ………… soon the Hare population will crash (drop).
  79. 83. (1) Some Lynxes leave ( emigrate) to where food is more plentiful. (2) Lynxes eat other prey when hare numbers low. (3) More competition between Lynxes. A CRASH in the Lynx population This drop in Hare numbers leads to 3 things …
  80. 84. Lower Hare numbers – vegetation starts to grow again + Hares have fewer Lynx to watch out for + There is more vegetation to eat SO, the number of Hares begins to increase The PREDATOR PREY cycle begins again MEANWHILE…..
  81. 85. Highest peaks always belong to PREY Why? The predator is ALWAYS at a higher level in the pyramid of numbers Than the prey, so the numbers of prey are always HIGHER than predators
  82. 86. COMPETITION… <ul><li>Competition is the STRUGGLE FOR RESOURCES WHICH ARE IN SHORT SUPPLY </li></ul><ul><li>PLANTS compete for Light,Nutrients and Water </li></ul><ul><li>ANIMALS compete for Food, Territorities,Shelter, and Water </li></ul>EACH SPECIES AFFECTS THE DISTRIBUTION OF OTHERS..
  83. 87. Where do decomposers come in? <ul><li>When living things die their bodies are broken down by decomposers so releasing the elements they contain. </li></ul><ul><li>These minerals can be used by plants to grow so the cycle repeats over again </li></ul>
  84. 88. An example of Fungi You know
  85. 89. The Nitrogen Cycle Nitrogen in the air Denitrifying bacteria Eating Nitrates in the soil N 2 fixing bacteria waste NH 3 and its compounds Nitrates absorbed by roots N 2 fixing bacteria Decomposing Fertilisers Nitrifying bacteria Lightning Formation of oxides of nitrogen
  86. 90. …On pollution <ul><li>Pollutants may REDUCE the biodiversity in an ecosystem </li></ul><ul><li>Eg fossil fuels produce Sulphur Dioxide when burned </li></ul><ul><li>This can cause ACID RAIN </li></ul>This can lower the pH in Lochs killing some INVERTEBRATES And FISH
  87. 91. Pollution and Biodiversity… <ul><li>If untreated sewage enters a river or lake it provides food for BACTERIA. </li></ul><ul><li>Their population numbers increase </li></ul><ul><li>They use up all the oxygen in the water </li></ul><ul><li>Species which cannot tolerate low Oxygen levels die out </li></ul>THIS RESULTS IN A DECREASE IN THE VARIETY OF SPECIES
  88. 92. DO dissolved oxygen BOD biochemical oxygen demand
  89. 93. Oxygen Sag The oxygen decline and rise downstream from a point source is called the oxygen sag.
  90. 94. The Biodiversity crisis <ul><li>Human activity can cause habitat destruction and pollution. </li></ul><ul><li>This contributes to the extinction of many species ; a reduction in the overall number. </li></ul><ul><li>Eg Deforestation, for housing,timber and agriculture </li></ul>CONSERVATION MEASURES HELP MAINTAIN BIODIVERSITY
  91. 95. WHY IS BIODIVERSITY SO IMPORTANT ? <ul><li>FOOD….Eg fish from the North Sea </li></ul><ul><li>RAW-MATERIALS…such as timber and rubber </li></ul><ul><li>MEDICINES…may come from as yet undiscovered plants </li></ul><ul><li>RECREATION…appreciation of the variety of species in the countryside. </li></ul>AND…MAINTAINING GENETIC VARIATION……..
  92. 96. Grazing and Biodiversity… <ul><li>Grassland is made up of a variety of plants </li></ul><ul><li>Some species grow quickly and dominate </li></ul><ul><li>Some species don’t grow as quickly and struggle to compete and survive </li></ul><ul><li>GRAZING is the eating of plants by herbivores </li></ul>UNSELECTIVE GRAZERS EAT ALL TYPES OF PLANT
  93. 97. Intensity of Grazing… <ul><li>LOW levels of unselective grazing allows the grasses to grow and out compete other less vigorous species.This REDUCES the variety of species </li></ul><ul><li>MEDIUM levels keep the grasses in check allowing less vigorous species to survive.This INCREASES the variety of species </li></ul><ul><li>HIGH levels result in OVERGRAZING.This DECREASES the variety of species </li></ul>
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