5.1 notes

HOW POPULATIONS GROW

Describing Populations: there are five different ways to study populations, which include--

Geographic Range- the area inhabited by a pop., can vary largely in size, but this depends on the species. EX: Bacteria in a rotting pumpkin may have a range smaller than a cubic meter. On the other hand, cod in the W. Atlantic covers a range from Greenland to N. Carolina.

Density and Distribution- population density (<- vocab) deals with the number of individuals per unit area. There are different densities to each species population. A population can be distributed in three ways: randomly (ex: Purple lupines grow randomly in a field of wildflowers), uniformly (ex. King Penguins pop. shows uniform spacing between individuals), and clumped (ex. Striped catfish form tight clumps)
-there are pictures on page 131 in your textbook if you need a visual for these examples-

Growth Rate- whether the pop. increases, decreases, or stays the same. EX: Hydrilla plants in their native habitat usually stay the same size. Their growth rate is around zero because their population doesn't increase or decrease in size.

Age Structure- number of males and females at a certain age each population contains. This is needed to fully understand a species population because most plants/animals cannot reproduce until a certain age.

Population Growth: there are two ways that can affect population size, they are--

Birthrate and Death Rate-
~ birthrate > death rate = higher population
~birthrate = death rate = same size population
~birthrate < death rate = lower population

Immigration and Emigration-
~immigration= when individuals into another populations range from elsewhere
EX: Increase of squirrel population in oak grove along with increase of acorn supply.
~emigration= when individuals move out of populations range/ when animals reaching maturity search for mates or try to establish new territories
EX: Shortage of food/overcrowding may lead to emigration

Exponential Growth: when a species is under ideal conditions and unlimited resources, it's population will grow exponentially. This is the "J" curve on a graph that we learned in class.

Three different environments where Exponential Growth is prominent: with organisms that produce rapidly (bacteria), with organisms that produce slowly (elephants), and with organisms in new environments (European gypsy moths in Boston -this happens sometimes because they are from a foreign area, we don't have predators to keep whatever species under control-)
-again, visual on page 133 in your textbook-

Logistic Growth: when a species is in exponential growth and an events/ series of events (look at population growth above for options) stops the growth, in other words, reaches carrying capacity (the max. numero of individuals of particular species that particular environment can support). Many plants and animals follow this curve. This is the "S" curve on a graph that we learned in class.

Three phases of growth:
~Phase 1: Population grows rapidly. (EXPONENTIALLY)
~Phase 2: Growth slows. (SERIES OF EVENTS)
~Phase 3: Growth stops; population size stablilizes. (CARRYING CAPACITY)

Last page, which I'm pretty sure is just a filler story is about "The invasive Zebra Mussels and Quagga Mussel" and the two main points are that they should be destroyed or at least controlled/ attempt to prevent. These are an example of an organism in a new environment which is a/an : YOU GUESSED IT! Exponential Growth!

Janna Lyhus is cooler than Luke Pilliod will ever be. Just Saying.