2. POPULATIONS Ch 5.1 Ecology

3. Population Review What is a population?What is a population? Groups of individuals that belong to the same species and live in the same areaGroups of individuals that belong to the same species and live in the same area Give an example from a biome.Give an example from a biome.

4. Population Characteristics 1)Geographic Distribution 2)Population Density 3)Growth Rate 4)Age Structure* Each factor listed above is equally important in determining the future of a population. (ex: endangered vs. overpopulated)

5. Geographic Distribution Also called “range”Also called “range” Area (size) inhabited by a populationArea (size) inhabited by a population Ex: Northern Cardinals and Cedar WaxwingsEx: Northern Cardinals and Cedar Waxwings

6. Northern Cardinal

7. Cedar Waxwings

8. Population Density Number of individuals per unit areaNumber of individuals per unit area Main characteristic to describe a populationMain characteristic to describe a population Varies greatly depending on species and quality of ecosystemVaries greatly depending on species and quality of ecosystem Ex 1: Cacti vs. Rainforest Fig Trees….Which is more dense?Ex 1: Cacti vs. Rainforest Fig Trees….Which is more dense? Ex 2: Science Daily (Dec. 7, 2000) — Nov. 22, 2000 -- Zoologists from the University of Toronto have cracked the ecological puzzle of how animals - in this case the arctic ground squirrel - manage to control their own population in the northern boreal forest of Canada.Ex 2: Science Daily (Dec. 7, 2000) — Nov. 22, 2000 -- Zoologists from the University of Toronto have cracked the ecological puzzle of how animals - in this case the arctic ground squirrel - manage to control their own population in the northern boreal forest of Canada.

9. Growth Rates Natural populations can grow, decline, or stay the sameNatural populations can grow, decline, or stay the same Depends on 3 factors:Depends on 3 factors: Birth RateBirth Rate Death RateDeath Rate Individuals entering or leaving populationIndividuals entering or leaving population Immigration (in) and Emigration (out)Immigration (in) and Emigration (out) Give an example for the terms above!Give an example for the terms above!

10. Examples What will happen to the following population (grow, decline, stay the same) immediately and later.What will happen to the following population (grow, decline, stay the same) immediately and later. 1.The EPA protects sea otters from hunting. 2.Killer whales prey on sea otters.

11. Exponential Growth With abundant space and food, protection from disease and predators, a population will increase in size exponentiallyWith abundant space and food, protection from disease and predators, a population will increase in size exponentially 1.Reproduce at constant rate 2.Unlimited Resources 3.Begins slowly, then takes off! Ex: Doubling effect of bacteria

12. Consider this… Bacteria have the fastest rates of reproduction among living thingsBacteria have the fastest rates of reproduction among living things Assume “binary fission” (doubling) occurs every 20 minutesAssume “binary fission” (doubling) occurs every 20 minutes 20 min= 2 bacteria20 min= 2 bacteria 40 min= 4 bacteria40 min= 4 bacteria 60 min=8 bacteria60 min=8 bacteria 120 min = 64 bacteria120 min = 64 bacteria 3 hrs = 512 bacteria3 hrs = 512 bacteria 24 hrs = 4,720,000,000,000,000,000,000 bacteria24 hrs = 4,720,000,000,000,000,000,000 bacteria

13. Charting Exponential Growth J-shaped curve = unlimited resources and growthJ-shaped curve = unlimited resources and growth

14. Logistic Growth As shown prior, exponential growth only lasts for a short whileAs shown prior, exponential growth only lasts for a short while Logistic growth occurs when growth slows or stops after exponential growth occursLogistic growth occurs when growth slows or stops after exponential growth occurs Results from:Results from: Birthrate drops/Death rate increasesBirthrate drops/Death rate increases Immigration slows/Emigration increasesImmigration slows/Emigration increases Both can result from lack of space and resourcesBoth can result from lack of space and resources

15. Charting Logistic Growth “S” shaped curve“S” shaped curve Shows “carrying capacity” of an ecosystem (maximum # of organisms based on available resources)Shows “carrying capacity” of an ecosystem (maximum # of organisms based on available resources) Why does the population remain constant towards the end of the curve?Why does the population remain constant towards the end of the curve?

16. Bringing it all Together!

17. Why is the carrying capacity not a flat line?