Populations, Communities and Biodiversity

Populations, Communities and Biodiversity

Population Ecology: Population Characteristics Population Characteristics • Population Density: • The number of organisms per unit area • Spatial Distribution: • Dispersion: The pattern of spacing a population within an area • 3 main types of dispersion • Clumped • Uniform • Random • The primary cause of dispersion is resource availability

Population Ecology: Population Characteristics Population Limiting Factors • Population growth rate • How fast a given population grows • Factors that influence this are: • Natality (____ rate) • Mortality (_____ rate) • Emigration (the number of individuals moving _________ a population) • Immigration (the number of individuals _________ a population) birth death away from moving to

Population Ecology: Density-independent factors Population Limiting Factors • Density-independent factors • Factors that limit population size, regardless of population density. • These are usually abiotic factors • They include natural phenomena, such as weather events • Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc.

Population Ecology: Density-dependent factors Population Limiting Factors • Density-dependent factors • Any factor in the environment that depends on the number of members in a population per unit area • Usually biotic factors • These include • Predation • Disease • Parasites • Competition

Understanding Exponentials Population Ecology: Population Growth Rate • Put your pens down for a minute & think about this: • An employer offers you two equal jobs for one hour each day for fourteen days. • The first pays $10 an hour. • The second pays only 1 cent a day, but the rate doubles each day. • Which job will you accept?

Population Ecology: Population Growth Rate Understanding Exponentials Now, how much would your employer owe you if you stayed at this job for another 2 weeks? Job 2 lags for a long time before exponential growth kicks in! What would happen if this type of growth took place within a population?

Population Ecology: Population Growth Rate Population Limiting Factors • Population growth models • Exponential growth model • Also called geometric growth or J-shaped growth. • First growth phase is slow and called the lag phase • Second growth phase is rapid and called the exponential growth phase • Bacteria can grow at this rate, so why aren’t we up to our ears in bacterial cells?

Population Limiting Factors Population Ecology: Population Growth Rate • Population growth models • Limits to exponential growth • Population Density (the number of individuals per unit of land area or water volume) increases as well • Competition follows as nutrients and resources are used up • The limit to population size that a particular environment can support is called carrying capacity (k) • When you’re done writing, put your pens down…

Population Ecology: Population Growth Rate What population do you think this is?

So, what do you think is going to happen to the human population? • We will probably reach our carrying capacity. • Our growth rate will start to look like most organisms, which is the Logistic Growth Model Carrying Capacity (k) What letter does this curve kind of look like?

Population Limiting Factors Population Ecology: Population Growth Models • Population growth models • Logistic Growth Model • Often called the S-shaped growth curve • Occurs when a population’s growth slows or stops following exponential growth. • Growth stops at the population’s carrying capacity • Populations stop increasing when: • Birth rate is less than death rate(Birth rate < Death rate) • Emigration exceeds Immigration (Emigration > Immigration)

Population Limiting Factors Population Ecology: Population Growth Models • Population growth models • Logistic Growth Model The S-curve is not as pretty as the image looks • Carrying capacity can be raised or lowered. How? Example 1: Artificial fertilizers have raised k Example 2: Decreased habitat can lower k • Populations don’t reach k as smoothly as in the logistic graph. • Boom-and-Bust Cycles • Predator-Prey Cycles

Community Ecology: Communities Communities • Review: • A community is a group of interacting populations that occupy the same area at the same time.

Community Ecology: Communities Communities • Limiting Factors • Any abiotic or biotic factor that restricts the numbers, reproduction, or distribution of organisms.

Community Ecology: Communities Communities • Range of Tolerance • The limits within which an organism can exist.

Community Ecology: Ecological Succession Ecological Succession • Ecological Succession • The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors

Community Ecology: Ecological Succession Ecological Succession • Ecological Succession • Consists of 2 types: • Primary Succession • Secondary Succession

Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • The establishment of a community in an area of exposed rock that does not have topsoil is called Primary Succession. • It occurs very slowly at first

Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • The first organisms to arrive are usually lichens or mosses, which are called pioneer species. • They secrete acids that can break down rock • Their dead, decaying organic materials, along with bits of sediment from the rock make up soil.

Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • Small weedy plants and other organisms become established. • As these organisms die, additional soil is created

Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • Seeds brought in by animals, water and wind begin to grow in the soil. • Eventually enough soil is present for shrubs and trees to grow.

Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • The stable, mature community that eventually develops from bare rock is called a climax community.

Community Ecology: Ecological Succession: Secondary Succession Ecological Succession • Ecological Succession: Secondary • Disturbances (fire, flood, windstorms) can disrupt a community. • After a disturbance, new species of plants and animals might occupy the habitat.

Community Ecology: Ecological Succession: Secondary Succession Ecological Succession • Ecological Succession: Secondary • Pioneer species in secondary succession are usually plants that begin to grow in the disturbed area. • This is much fasterthan primarysuccession

Community Ecology: Ecological Succession Ecological Succession • Ecological Succession: End point? • Cannot be predicted • Different rates of growth &human involvementmake it impossible toknow if a true climaxcommunity has beenreached.

Biodiversity and Conservation: Introduction On the left side of your IntNB, address the following: • What would happen if all of the jackrabbits in a food web died suddenly? • Is the disappearance of one species from Earth important, or will another species fill its niche?

Biodiversity and Conservation: What is biodiversity? Biodiversity • What is Biodiversity? The variety of life in an area that is determined by the number of different species in that area. • There are 2 main types: Genetic Diversity Species Diversity

Biodiversity and Conservation: Why is biodiversity important? Biodiversity Penicillin: Derived from bread mold Teosinte: A distant relative of corn Domestic corn plant Madagascar Periwinkle: Used to treat childhood forms of leukemia

Biodiversity and Conservation: Extinctions Extinction Rates • The gradual process of becoming extinct is known as background extinction. • Mass extinctions: When a large percentage of all living species become extinct in a relatively short period of time. • 250 MYA: Over90% of species died

Biodiversity and Conservation: Extinctions Estimated number of Extinctions since 1600

Biodiversity and Conservation: Extinctions Five Most Recent Mass Extinctions Cretaceous Period (65 MYA) Triassic Period (200 MYA) Permian Period (250 MYA) Devonian Period (360 MYA) Ordovician Period (444 MYA)

Activity: Understanding Geological Time • Working in your groups, you will get the following supplies: • A meter stick • A roll of 5 meters of paper • Colored pencils • Using the worksheet, plot out the dates. • 1 million years is a millimeter • 1 billion years is a meter

Populations, Communities and Biodiversity