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 1. Density - “the number of individuals per unit area or volume” Ex - # bass fish per cubic meter of water 2. Dispersion – “ the relative distribution or arrangement of it’s individuals in a given amount of space” “ 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 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!?)

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 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: 1. Density Dependant 2. Density Independent

S – Curve Growth  Mimics a “S”  Population starts slow, then increases quickly, then begins to level off to support the current population at it’s maximum capacity.

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 – physical home, env factors for its survival, and its interactions with others. 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. 1. Competition 2. Predation 3. Parasitism 4. Mutualism 5. 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 the other

Mutualism = defined as: Benefits both!

Parasitism = defined as: benefits one, harms the other

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

Symbiosis and Coevolution  Symbiosis is the relationship in which 2 species interact.  Typically in which one benefits.  Coevolution may occur b/w species in close relationship. - Without one, the other will die! - Without one, the other will die!