Population Dynamics

Relationships in an Ecosystem

Symbiosis Symbiosis: a long-term relationship between two organisms in an ecosystem.

Types of Symbiosis Mutualism: both organisms benefit from their relationship Commensalism: one organism benefits, and the other is unaffected Parasitism: one organisms benefits, and the other is harmed

Symbiosis Summary Relationship Type Species ASpecies B Mutualism ++ Commensalism +0 Parasitism +-

Name That Symbiosis Lampreys feed off of the trout below, and eventually cause it to die.

Name That Symbiosis Lampreys feed off of the trout below, and eventually cause it to die. Parasitism

Name That Symbiosis A clown fish lives among the sea anemone. The clown fish gains protection, but the anemone is neither harmed nor helped.

Name That Symbiosis A clown fish lives among the sea anemone. The clown fish gains protection, but the anemone is neither harmed nor helped. Commensalism

Name That Symbiosis Ox-peckers live on the heads of the ox, eating insects and keeping the ox clean. The birds also get a place to live.

Name That Symbiosis Ox-peckers live on the heads of the ox, eating insects and keeping the ox clean. The birds also get a place to live. Mutualism

Predator vs. Prey Predator and prey populations can affect one another. 1) As prey increases, predator will increase in response. 2) As predators increase, prey will decrease. 3) As prey decrease, predators will decrease.

Predator vs. Prey

Population Growth and Overpopulation

Populations The number of organisms from one species that live in a specific area Examples: the human population in different cities, the squirrel population in a forest, the grass population in a meadow

Populations are affected by many resources. These include: The amount of food available in an area The amount of sunlight (if it is a plant population) The amount of water The competition for food/shelter The predators in an area

Population Growth Graphs A: Slow growth as a population begins to grow Birth Rate > Death Rate

B: Exponential growth as population grows rapidly Birth Rate > Death Rate

C: Slow-down of growth as population maxes out its resources, like food, water, or light Birth Rate > Death Rate

D: Population reaches the maximum number supported by environment, the carrying capacity Birth Rate = Death Rate

Carrying Capacity Carrying Capacity: the maximum number of organisms in a population that are supported by the environment

Carrying Capacity Reaching Limit of Resources Exponential Growth, no limiting resources

Populations are typically limited by resources. – They reach carrying capacity when there aren't enough resources to keep growing. – Birth Rate = Death Rate.

Unlimited Growth If there are no limiting resources, populations grow exponentially. Birth Rate > Death Rate

Decline If population birth rate < death rate, the population will decline.

Which of the following graphs shows a population that is free of limiting factors?

Which of the following graphs shows a population that has reached carrying capacity?

How would a scientists determine the growth rate of a population? A. Birth Rate + Death Rate B. Birth Rate – Death Rate C. Birth Rate x Death Rate D. Birth Rate / Death Rate

What statement best describes the population shown in the graph below? A. Birth rate = Death rate B. Birth rate < Death rate C. Birth rate > Death rate D. Birth rate = 0

What statement best describes the population shown in the graph below at time “t”? A. Birth rate = Death rate B. Birth rate < Death rate C. Birth rate > Death rate D. Birth rate = 0

R-selected species (r) – high rate of population increase - Tend to be opportunists - Short generation times - Reproduce early in life - Reproduce many times in life - Many offspring when they reproduce Two types of organisms and their population growth

K-selected species – slow reproduction - Reproduce later in life - Small number of offspring - Born large and mature slowly

Patterns of Population Distribution Clumping – Populations live in clumps or patches Uniform Dispersion – Constant distance between individuals Random Dispersion – Fairly rare, random spacing