Understanding Populations Chapter 8 pg 210 Understanding Populations

What is a population? “all the members of a species living in the same place at the same time”

Properties of Populations Density - “the number of individuals per unit area or volume” Ex - # bass fish per cubic meter of water Dispersion – “ the relative distribution or arrangement of it’s individuals in a given amount of space” Even Clumped Random

Growth Rate Change in pop. size = Births – Deaths If adults in a population are not replace by new births, the growth rte will be negative and the population will shrink

How Fast can the Population Grow? Biotic Potential = Fastest rate at which its population can grow. Limited by: The organism’s: Repro. Potential

Reproductive Potential 1. Number of offspring produced at one time 2. How often does the organism reproduce 3. how soon can the organism reproduce (age!?)

Logistic Growth Population grows initially and then begins to taper off and only carry the amount suitable for the ecosystem Shows a S shaped curve

Exponential Growth Population growth that grows faster and faster! Produces a J-Shaped curve

Limits to population Growth 1. Carrying Capacity 2. Resource Limits 3. Competition within a population

1. Carrying Capacity Defined as the maximum population (number) that the ecosystem can support. Will crash when it reaches capacity due to disease, etc.

2. Resource Limits A particular resource that is consumed by a particular species (food, water, etc) is called a “LIMITING FACTOR” CC is reached when the species is consuming it at the same rate it is being produced.

3. Competition Within a Population = Members of a population use the same resources in the same way so they will eventually compete with one another as the population approaches it carrying capacity. Ex = Christmas time and Limited toys

2 types of Competition: Direct = direct fighting for resources Ex – food Ex – Limited # of Elmo dolls at target at an 8 am sale and 400 mommies waiting outside! Indirect = indirect fighting for resources Ex- nocturnal vs. diurnal Ex – mommy arrives at a 24 hour Target and buys the last doll before another mommy arrives at 8 am!

Two types of population Regulation: =The cause of death to regulate the population size can be: Density Dependant Density Independent

Density Dependant = Death occurs more quickly in a crowded population than a sparse one.

Density Independent = death that is caused regardless of the pop.’s density. It affects all members of a population in a general/similar way.

8.2 How species interact with each other (pg. 217) Niche = role in the ecosystem. Ex – decomposers niche is to recycle nutrients in its ecosystem! Habitat = location. Ex -Where an organism lives

Species Interactions page 218 = based on whether each species causes benefit or harm to the other species in a given relationship. Competition Predation Parasitism Mutualism Commensalism

Competition Defined as both species being harmed. May be in competition for mates, territory, food, etc.

Predation = defined as: benefits one and harming the other

Symbiosis: Symbiosis is the relationship in which 2 species interact. Typically in which one benefits. 1. mutualism 2. parasitism 3. commensalism

Mutualism = defined as: Benefits both!

Parasitism = defined as: benefits one, harms the other

Commensalism = defined as one benefits and the other is unaffected.