Populations Communities And Ecosystems

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Populations Communities And Ecosystems

  1. 1. POPULATIONS, COMMUNITIES, AND ECOSYSTEMS Chapter 2
  2. 2. LIVING THINGS INTERACT All the organisms of the same species living  together that live in a specific ecosystem are called a population The individuals in the population compete with one  another for food, nesting space, and mates.
  3. 3. LIVING THINGS INTERACT All of the populations of different species of animals  and plants that live and interact together in an area is a community The different populations in a community depend  on each other for food, shelter, and many other things
  4. 4. LIVING THINGS INTERACT Each community depends on its environment. The  nonliving, or abiotic, parts of an environment combine with the living, or biotic, things in a community to make up an ecosystem. Abiotic things include  soil, air, temperature, precipitation, and many more.
  5. 5. Looking at p.34 in your textbook, identify two biotic and  two abiotic factors in Figure 2-1. Biotic 1. ______________________________________ 2. ______________________________________ Abiotic 1.______________________________________ 2. ______________________________________  When you’re finished, pair up with someone beside you and share what you wrote down.
  6. 6. In the next slide box, draw an ecosystem of your choice.  Include at least 5 populations as well as biotic and abiotic factors. Below your picture write  Populations: Community:  Ecosystem:  Tell me what from your picture is included in each of the vocabulary words.
  7. 7. CHARACTERISTICS OF POPULATIONS Population density- the number of organisms per 1. unit of living space It’s NOT just the number of organisms in the population.
  8. 8. POPULATION DENSITY Look at Figure 2-3 on p.36. Each population is  made up of the same number of oak trees. Trees in population I are spread over 10 km2 while  those in population II occupy only 1 km2. Which of these populations has greater population  density? What are the population densities for each? 
  9. 9. Sometimes populations are spread over a large  area while in other cases a population is clumped together in a small area. Look at Fig.2-4. Those birds are evenly spread  throughout the marsh where they live. -Why do you think they spread out evenly?
  10. 10. CHARACTERISTICS OF POPULATIONS 2. Size- which is constantly changing  Populations can increase in size through  reproduction of organisms. They can also decrease in size due to the death of organisms. The birthrate and death rate need to be considered  together to see their actual effect on population size.
  11. 11. LOOKING AT BIRTHS AND DEATHS Population of rabbits lives in a 1 km2 field. At the  beginning of the year the population is 225 rabbits. The end of the year population count shows there are now 310 rabbits. Does this mean that there were 85 rabbits born that  year? Not necessarily. Although the population increased  by 85, perhaps 150 rabbits were born and 65 rabbits died.
  12. 12. LOOKING AT BIRTHS AND DEATHS Let’s take a look at that same rabbit population the  following year. The total population goes from 310 to 400 rabbits. Births: 150   Deaths: 75  Net gain: 75 rabbits Where did the other 15 rabbits come from? 
  13. 13. COMING AND GOING The other 15 rabbits might have immigrated to the  ecosystem. Immigration: when new members join a population  Emigration: when members of a population leave 
  14. 14. Mice Cats Original Population 45 6 Births 105 4 Deaths 95 1 Immigration 6 2 Emigration 16 0 Which population has the greatest density at the beginning of the year? At the end of the year? Which population was larger at the end of the year?
  15. 15. INTERACTIONS WITH THE ENVIRONMENT Most living things produce more offspring than will  survive. For example, a female frog might lay hundreds of eggs in a small pond. In a few months, the population of frogs in that  pond will be about the same as it was the year before. Why isn’t the pond overrun with frogs? 
  16. 16. LIMITING FACTORS Populations cannot grow indefinitely because the  environment only contains so much food, water, living space, and other needed resources. When one or more of those resources becomes  scarce, it is called a limiting factor.
  17. 17. For example, food could become a limiting factor  when a population becomes too large for the amount of food available. Any single resource can be a limiting factor for  population size.
  18. 18. CARRYING CAPACITY The largest population that a specific environment can  support over a long period of time is called the environment’s carrying capacity. When a population grows larger than its carrying  capacity, limiting factors in the environment cause the population to get smaller.
  19. 19. What kinds of limiting factors might act on a  population of tropical fish living in an aquarium?
  20. 20. RELATIONSHIPS BETWEEN POPULATIONS Most common is the predator-prey relationship.  Predator is an animal that hunts and eats other  animals The animal eaten by a predator is its prey  Examples: lion-zebra, bird-worm 
  21. 21. Parasitism is a relationship between two types of  organisms in which one organism benefits while the other one is harmed Parasite is an organism that lives in or on another  organism and is harmful to that organism The infected organism is the host 
  22. 22. EXAMPLES OF PARASITISM Athlete’s foot  -Parasite: fungus -Host: human’s foot Other common examples are fleas, ticks, lice, and mosquitoes. These animals live off the blood of the host. The parasite doesn’t want to kill the host though. If the host dies, this normally results in the death of the parasite as well.
  23. 23. OTHER RELATIONSHIPS Commensalism: one organism benefits while the other  is not affected Examples: clown fish and sea anemone from p.32-33  Mutualism: both organisms benefit  Example: termite and protozoan in termite’s gut 

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