Unit 2 – Lecture 4

Review… Discuss What is a population? Population – a single species in a single location at the same time

Population Growth Exponential Growth – number of organisms grows very quickly

Logistic Growth – begins with a period of rapid growth [like exponential], then slowly stabilizes BE CAREFUL WHEN DRAWING THIS GRAPH!!! Population Growth – cont’d

Discuss Why would a population be able to grow so quickly like the exponential graph? Why would a population stabilize like the logistic graph? Which graph is more realistic?

Population Growth Exponential Growth – possibly due to lack of predators, great amount of resources [food, habitat, etc].

Population Growth – cont’d The population stabilizes in the logistic curve because… diminishing resources more orgs, less resources for each org Which growth curve is more realistic? Why? Logistic – because resources aren’t unlimited.

Population Growth – cont’d Carrying Capacity – the largest number of organisms that an ecosystem can support. influences for carrying capacity include… resources [food, shelter…], human influence, predation, illness, natural disasters, climate, etc…

Population Growth – cont’d Which type of curve showed a carrying capacity?

Carrying Capacity Shown on the graph: Or, more realistically…

Population Growth – cont’d Why does the line of CC waver on the realistic graph? births & deaths [explanation, don’t need to write this down…] as orgs increase, resources decrease decrease in resources  decrease in the number of orgs that can survive less orgs surviving  more resources more resources  increase in orgs that can survive

Limiting Factors Limiting Factor – a factor which limits a population’s growth includes everything that limits the carrying capacity resources [food, shelter…], human influence, predation, illness, natural disasters, climate, etc

Limiting Factors – cont’d Two Types: Density Dependent Factors limiting factors that DO depend on the density [#] of orgs in the area Density INdependent Factors limiting factors that DO NOT depend on the density [#] of orgs in the area.

Discuss Look back at your warm-up. Each of those items would be a limiting factor. Discuss and label each of the items on your list as either density dependent or density independent limiting factors.

Limiting Factors – cont’d Density Dependent Factors ex: resources, illness, predation… Density INdependent Factors ex: climate, natural disasters, human interaction…

Limiting Factors – cont’d Which is which? Ask this question: Would there be a change in the factor’s effect if there were 10 orgs in the area compared to if there were 10,000? Examples – Resources vs. Climate Yes, the factor would change = density dependent No, the factor wouldn’t change = density independent

Homework Complete the Kaibob & Carrying Capacity w/s on page of your packet. remember – use a SCALE graph axes go up by even intervals every box = the same amount use up at least 75% of your graph space!