Chapter 5-3: Population Dynamics & Carrying Capacity limits population growth. Fig. 10–4a...

Chapter 5-3: Population Dynamics & Carrying Capacity

Characteristics of Populations Population Dynamics:

• population ___________

• population ________________

•Per unit area for terrestrial species

•Per unit volume for aquatic species

• ___________________ is the spatial patterning;

• _________________is the proportion of individuals in each age group (e.g., prereproductive, reproductive, & postreproductive) of a population.

Characteristics of Populations

Population dispersion can be clumped, uniform, or randomly distributed.

What is the human population dispersion?

Clumped Example: Elephant herd

Uniform Dispersion Example: Creosote bushes

Random Dispersion Example: Dandelions

________ dispersion is the most common

Why ______________? o Species tend to cluster where resources are available oGroups have a better chance of finding resources o Protects some animals from predators o Packs allow some to get prey o Temporary groups for mating and caring for young

Human Populations show ____________ distribution

1. Exponential: occurs when resources are ___________:

Most populations _______________________ (no limiting factors) grow at exponential rate

Types of Growth

The population increases by a percentage of the whole in a given time (and therefore increases by an increasing amount forming a J –shaped curve).

050

100150200250300

1 2 3 4 5 6 7 8 9Time (minutes)

Nu

mb

er o

f S

alm

on

ella

Number ofSalomonella

Biotic Potential Biotic Potential is the _______________ for growth

under ideal conditions.

Intrinsic rate of growth (r) is the __________ at which a species would grow if it had unlimited resources and other ideal conditions.

r

Doubling Time: Rule 0f 70 Doubling time =

70/percentage growth rate

Example: if the pop. grows by 1.43% each year, then the doubling time will be: 70/1.43 = 49 years

Kitten growth rate = 157% Doubling time = 0.45 years

Exponential Population Growth • during exponential growth

population size increases faster & faster with time;

• exponential growth can not occur forever because eventually some factor limits population growth.

Fig. 10–4a

Puppy growth rate = 139% Doubling time = 0.5 year

Carrying Capacity (K): The ___________ number of organisms that a region can support.

2. Logistic Growth: occurs when ______________ become more and more _____________ as population size increases. Sigmoid (S-shaped) graph of population that initially grows exponentially but plateaus at the carrying capacity.

Types of Growth

Population Controls

_____________________: sum of all the abiotic/biotic factors that will limit population growth.

Abiotic factors:

temperature, light, nutrients…

Biotic factors: food supply, competitors…

Density-Dependent Population Control: Factor which limits population that has a

__________ effect when population’s _________ increases. They are often due to ____________ feedback loops.

Example: Competition

Density-dependent controls tend to regulate the population at __________ levels.

Density-Independent Population Control:

Limiting factor for population that is ____ _____________ by population density.

Example: Fire

In a larger, denser population, a density-independent population control may kill more organisms but it does not have an increasing impact/ kill a greater percentage of the population. A density-dependent control has a greater impact in a dense population and can serve as a negative feedback to maintain a more constant population size.

Discuss with your table partner: Which of the following processes/events are density-dependent population controls and which are density independent population controls?

Process/Event Flood Hurricane Parasitism Infectious Disease Pollution

Type of Pop. Control Density- Density- Density- Density- Density-

Carrying Capacity is usually not a fixed quantity. • If there is an increase or decrease in a limiting factor,

the carrying capacity can shift.

Earth’s carrying capacity has changed due to cultural revolutions

• _____________ Revolution (~12,000 BP): changed from hunter-gather society. • _____________ Revolution (275 BP):

rapid urbanization, large-scale movement of resources.

• ____________ Revolution (50 BP): increased farming yields through commercial fertilizer use and selective breeding of high yield crops.

Exceeding the Carrying Capacity During the mid–1800s sheep populations exceeded the carrying capacity of the island of Tasmania. This "overshoot" was followed by a "population crash". Numbers then stabilized, with oscillation about the carrying capacity.

Exceeding the Carrying Capacity Why do populations oscillate around the carrying capacity? • ____________in the effects of the limiting factor: • Example: if the limiting factor is food, the population first has to exceed the available food resources before the population will decrease (due to starvation). • Once population is reduced, it grows back until it once again exceeds its carrying capacity, and population is reduced again, and so on…

• Oscillations are the result of _________________ feedback loops

Exceeding the Carrying Capacity

Example: Reindeer introduced to a small island off of Alaska in the early 1900s

Populations may not recover if they permanently destroy their habitat by depleting resources beyond a recoverable level (carrying capacity is then ______________)

4 Types of Variation in Population Size o ___________: Population stays close to

carrying capacity. o _____________: Explosive growth followed by

crash. Example: short-lived algae and insects. May be linked to seasonal changes etc.

Four General Types of Variation in Population Size Cont.

o ____________: Population fluctuates up and down. “Boom and Bust” cycles.

Top-down control example: Predators Bottom-up control example: Food supply

o _____________: no pattern (chaos in system)

Minimum Critical Size Even if the resources are unlimited, a population

may not exhibit exponential growth if it does not have a minimum critical size.

Having minimum critical size is important for: ● finding ___________ ● preventing _____________ ● providing adequate __________ _________________

Reproductive Strategies (Quantity vs. Quality) Because organisms have a limited amount of energy

to expend on reproduction, in general the number of offspring produced per individual is _____________ related to the amount of energy expended per offspring.

Number Energy of offspring per offspring

Two main types of species based on reproductive strategies:

• r–strategist species: tend to live in environments where resources are not limiting; such species tend to have high intrinsic rates of growth (high r);

• K–strategist species: tend to live in environments where resources are limiting & tend to have lower intrinsic rates of growth and characteristics that enable them to live near their carry capacity (population size near K).

Reproductive Strategies & Survival

r vs. K Reproduction Strategies energy expended per offspring number of offspring ● ________, small offspring ● _____, larger offspring ● ___________ parental care ● _____ parental care ● _______ reproductive age ● ________reproduction ● most offspring _____ before ● most offspring ______ reproducing to reproductive age ● _____ population growth rate (r) ● _____ pop. growth rate

r strategists K strategists

r strategists Advantages/Disadvantages Advantages ● Adapted to ____________ niche ecosystems,

can rebound quickly after a disruption.

Disadvantages ● _______________ adults ● Less able to compete ● Population size _____________

wildly above and below the carrying capacity (K)

Niches ● __________________ niches ● ___________ successional species

K strategists Advantages/Disadvantages Advantages ● ________ adults ● Better able to compete ● Population size fairly __________

Disadvantages ● Can not _____________ as quickly

from environmental disruption/___________prone

Niches ● _________________ niches ● ______successional

species

Review with your table partner:

Type of Organism

Ant Sequoia Tree Elephant Coral Dandelion

Type of Strategist - strategist - strategist - strategist - strategist - strategist

Classify the following organisms as r-strategists or K-strategists.

Survivorship Curves

Three kinds of curves: Late loss

• high mortality is late in life

• usually _____ strategists Constant loss

• mortality is about the same for any age

• Usually intermediate reproductive strategy

Early loss • high mortality is early in

life • usually ____ strategists

K

r