Population Growth Notes 1-2

How Does a Population Grow?

• Natality=Birth

• When conditions are good, some organisms have more offspring than it takes to replace themselves

• When this happens to plankton, it is known as a “bloom”

• See Page 216 in your text (dinoflagellate bloom)

Dinoflagellate Population Explosion

What Makes A Population Stop Growing?

• Conditions become less favorable to support massive growth

• Resources get used up• Limiting resources (w/o which a population

can’t keep growing) include:– Food & Nutrients– Shelter/living space

• Carrying capacity = the largest population size that can be sustained by the available resources

Open vs. Closed Systems• An open system indicates individuals

emigrating (leaving) from an area and/or immigrating (coming) to an area– Ex: birds on an island that use their resources may

be able to survive on another island

• A closed system indicates individuals that are not capable of leaving the system.– Ex: humans on earth are stuck here. If our

resources become depleted or we reach carrying capacity, we may die.

What happens when a resource is limited? Intraspecific or

Interspecific?

http://www.youtube.com/watch?v=0jZe_VGLRYI

What are the resources that would be limiting here?

Primary Productivity – notes # 4• What are the limiting

factors?

Nutrients Required by Marine Plants• Nitrate (NO3) – most limited nutrient in the ocean is nitrogen• Phosphate (PO4) – a source of phosphorus that is also limiting

Plankton Populations in LIS Notes - # 6

• Spring Bloom-sunshine & nutrients not as limited, phytoplankton can go nuts!

• Why does bloom stop or slow in summer?– Increase in sunlight warms surface waters, they

become less dense, less well mixed– Phytoplankton use up nutrients (usually Nitrate 1st)– Nutrients limited=decrease in phytoplankton #’s– See pages 348-349 in text

• Fall Bloom – cool sunny days with lots of wind bring light and nutrients - plankton can go nuts again!

• Why does fall bloom stop or slow in winter?– Light becomes limited– Nutrients become limited as they are used up

Plankton Populations Worldwide

Guess who loves a good

phytoplankton bloom?