PA Standards:

1. PA Standards: • 4.1.7.A – Describe the relationships between the biotic and abiotic components of an ecosystem • Describe symbiotic and predator/prey relationships

2. 73. Chapter 1 – Populations & Communities • Ecosystem – All livingandnonliving things that interact in a particular area • Living things include bacteria, plants, and animals • Nonliving things include sunlight, chemicals, soil, water, air, and man-made items

3. Ecosystem Example • What is living? • What is nonliving? • Name the interactions.

4. 74. A single ecosystem may contain many “habitats” • Habitat – where an organism lives and finds what it needs to survive • Example: A pond ecosystem includes several habitats – the muddy bottom, the water, the bank, etc.

5. 75. Parts of an Ecosystem: • Biotic Factors – name given to all the LIVING parts; the interaction is often “eat or be eaten”! • Abiotic Factors – name given to all the NONLIVING parts; these supply the conditions for survival (shelter, oxygen, water, climate, etc.)

6. 76. Organisms are grouped by “species” • Species – all those organisms that are physically similar (look alike) and can reproduce fertile offspring

7. Not all animals that can mate are the same species! Ex: horse + donkey • The offspring is a mule that can’t reproduce (infertile).

8. 77. A species group is a “population” • Population = all the members of one species living together in a particular area • One ecosystem contains many populations • Ex: duck population, turtle population, etc.

9. 78. A group of populations is a “community” • Community = all the different populations that live together in an area

10. 79. In a community living things affect one another & their surroundings • Ecology – the study of how living things interact with each other and the environment; this work is carried out by an “ecologist”

11. American folk singer Pete Seeger recorded this song about environmental interactions • http://www.youtube.com/watch?v=UyGYXjyrvhY

12. 80. “Population Density” is the number of individuals found in a specific area (or how tightly packed) • It is calculated by dividing: • # of individuals Area they inhabit • Example: The population density of this classroom might have been designed to be 1 student per meter2

13. 81. Ways to Find Total Population Size 1) Counting: a. by direct observation (seeing the animals with your own eyes) b. by indirect observation (seeing only the animals’ tracks or nests) 2) Sampling: count only the animals in a small area, then estimate the rest 3) Mark & Recapture: captured animals are marked, then released; when a new sample is captured, the fraction of those w/marks can be used to calculate total population

14. Example of Sampling: • Bacteria are grown on the surface of agar (kind of gelatin) in petri dishes; these microscopic cells form colonies that show up as small spots on the agar. Often too numerous to count, the scientist will count only a sample of colonies(maybe ¼ the dish) and estimate the rest. • 40 colonies x 4 = • 160 on the whole • dish

15. Example of Mark & Recapture: • You use nets to catch 100 blue birds. • You put metal bands on the legs of all 100 and release them. • One month later you use nets again to catch blue birds. In this new group you find that ½ already have bands on their legs. • This indicates that in the original group of 100 birds, you really only caught ½ of the population in your nets. • Total population is then actually 200 birds.

16. 82. What can Change Population Size? • 1) Births: When birth rate > death rate, population increases • 2) Deaths: When death rate > birth rate, population decreases • 3) Immigration: individuals move in • 4) Emigration: individuals move out

17. 83. What Controls Population Size? • Limiting factors are environmental conditions that can stop population growth. • These include: food, space, and weather. • Carrying capacity is the largest population that an environment can support given its limiting factors.

18. Ecologists graph population data; this graph shows human population • Population grows steadily until resources run out. Limiting factors are little food, no shelter, & disease.