Population Ecology Part Two: Population Growth Developed by Steven Taylor Wichmanowski based in part on Pearson Environmental Science by Jay Withgott

Enduring Understandings 5.1 Population Growth Notes 12/6/2018 Enduring Understandings #1) Populations grow or decline through the combined effects of births, deaths, immigration and emigration. #2) There are limits to population growth and a maximum number of individuals an environment can support. Unit 5: Interconnected

What You Need To Know… Population size is controlled by (abiotic) non-living factors. The (biotic) environment influences the size of a population. Feedback mechanisms help to adjust population size toward an “ideal” level.

Carrying capacity is usually determined by one or more limiting factors. A limiting factor is some kind of environmental pressure that restrains the exponential growth of populations. Examples of limiting factors: availability of food availability of water availability of nutrients presence of predators presence of mates available habitat disease

Limiting Factors and Carrying Capacity

Density independent factors are limiting factors that do not depend on population density and usually relate to natural disasters. (e.g., a tsunami would significantly affect the populations of a small coastal village as well as a large coastal city)

Limiting factors slow population growth. In density-independent (DI) populations, birth rate and death rate do not change with population density Abiotic Factors Weather Fire Floods Wind and storms Oxygen supply Space/Area © 2011 Pearson Education, Inc.

(e.g., disease, competition, predation, resource availability) Some limiting factors are related to population density. Density dependent factors are limiting factors whose influence depends on population density (e.g., disease, competition, predation, resource availability) 

8) Limiting factors slow population growth. In density-dependent (DD) populations, birth rates fall and death rates rise with population density Biotic Factors Predation Infection Competition Toxic build-up Available mates © 2011 Pearson Education, Inc.

What You Need To Know… Population size is controlled by (abiotic) non-living factors. The (biotic) environment influences the size of a population. Feedback mechanisms help to adjust population size toward an “ideal” level.

One important factor in understanding population growth is a species’ biotic potential. Biotic potential is the maximum ability to produce offspring in ideal conditions. (i.e., how many babies can you have?)

5.1 Population Growth Notes 12/6/2018 3) Feedback mechanisms help to adjust population size toward an “ideal” level. A: Biotic potential B: Carrying capacity (avg.) C: Population max. D: Carrying capacity (actual) E: Endangered/Extinction Unit 5: Interconnected

Case Study #1: Paramecium Competition 5.1 Population Growth Notes Case Study #1: Paramecium Competition 12/6/2018 “What do you see?” “What does it mean?” Unit 5: Interconnected

Competition Use or defense of a LIMITING RESOURCE Not necessarily direct Ex) if one rabbit simply eats a patch of a limited food plant before another rabbit does, then they are competing with one another even if they never directly interact Ex) if one rabbit physically denies another rabbit access to food this is also competition

Interspecific Competition A form of competition in which individuals of DIFFERENT species compete for the same resource in an ecosystem (ex. Food or living space) Ex) If a tree species in a dense forest grows taller than the surrounding tree species, it is able to absorb more sunlight. Since shorter tree species are shaded, they get less sunlight needed to live. Ex) Leopards and lions both feed on the same prey, so they can be negatively impacted by the presence of one another since they will have less food.

Intraspecific Competition Members of the SAME species compete for limited resources Ex) Two males fighting each other over a female Ex) Wolf packs fighting for food or territory

Symbiotic Relationships A symbiotic relationship is a long- term, physically close relationship between separate species where at least one organism benefits.

Mutualism: (+/+) a symbiotic relationship where both species benefit

Commensalism: (+/0) a symbiotic relationship where one species benefits and the other is not affected either positively or negatively

Parasitism: (+/-) a symbiotic relationship where one species benefits and the other is harmed