2. Ecological Succession Do all ecosystems stay the same all the time? What are some things that cause changes to ecosystems? Natural and unnatural Quickly and slowly
3. Ecosystems are constantly changing in response to human and natural disturbances. As an ecosystem changes, older habitants die out and new organisms move in, causing more change
4. Ecological Succession Series of predictable changes that occur in a community over time Physical environment Natural disturbance Human disturbance
5. Primary Succession Succession on land that occurs on surfaces where no soil exists Volcanic eruptions Glaciers melting
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8. Stages of Primary Succession Start with no soil, just ash and rock First species to populate this area “pioneer species” For example, pioneer species on volcanic rock are lichens (LY-kunz) Lichens made up of fungus and algae that can grow on bare rock When lichens die, they for organic material that becomes soil…now plants can grow
9. Secondary Succession Succession following a disturbance that destroys a community without destroying the soil Natural hurricane fires Human disturbances Farming Forest clearing
16. What is population? A Population is a group of individuals of the same species living in an area. Group of individuals of the same species that live in the same area
20. What do you think happens when sea otters are hunted? Sea urchins increase or decrease? Kelp forest increase or decrease? Sea otters are then placed on the endangered species list So now what happens to the population of sea otter? Starts to increase How does this affect the kelp and the sea urchins? Sea urchins start to get eaten again=decrease in # Kelp increases b/c less sea urchins to eat them
23. What does this tell us about population? Population changes There are many factors that influence a population Natural Unnatural Population density has a great impact on ecosystems
24. 3 Factors that affect population size # of births # of deaths # of individuals that enter or leave population Population will increase or decrease depending on # of individuals added or removed
25. What happens to the population when we…. Have more births than deaths? Population increases Have more deaths than births? Population decreases Have equal amounts of births and deaths? Population remains constant
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27. Immigration “im”= in Migrate= to move from one place to another Immigration is the individual movement into an area Animals in search of mates and food in new areas
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32. Emigration “E” means ‘out’ Migrate means to move from one place to another Emigrate means individuals moving out of one place and into another Young wolves and bears leaving as they mature Shortage of food
33. Two types of growth Exponential growth Individuals reproduce at a constant rate Population multiplies by constant FACTOR over constant time interval Logistic growth Occurs when a populations growth slows or stops after a period of exponential growth As population approaches carrying capacity, BR may decrease, DR may increase or both, until equal
34. Exponential Growth Occurs under ideal conditions with unlimited resources Think about exponents in math…. Starts slowly then sky rockets to infinity Our graph will look like a J Bacteria
35. Lets look at bacteria… Bacteria reproduce by splitting in half Bacteria have a doubling time of 30 minutes If you start will one bacterium, how many bacteria will there be after the first 30 minutes? 2 After an hour? 4 After an hour and a half? 8 After two hours? 16 After 15 hours? Over a billion
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37. Logistic Growth As resources become less available, the growth of the population slows or stops S-shape curve No net increase or decrease in population What we usually see in nature: except for humans
39. Carrying Capacity The largest number of individuals that a given environment can support The flattened part of the logistic graph after the exponential growth The point at which this flat line reaches the y-axis is the size of the population when the growth rate reaches zero This doesn’t mean the population stops growing Many factors slow the growth of plants and animals…
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41. Limiting Factor Condition that can restrict a population’s growth Could be: Space Disease Availability of food
43. Boom and Bust Growth Cycles Increase rapidly for a period of time followed by a sharp decrease in population for a brief period of time Still not completely understood Hypothesis: Changes in food supply Stress from overcrowding Other organisms influence on population
44. Boom-and Bust Population Cycles -Involves more than one population -Rapid increase and decrease in populations
