Exam 3 Bios 230 uic

Biotic:

living interactions

-Spruce tree, mosses, bacteria and fungi

Abiotic

nonliving (physical and chemical) interactions

-sunlight, nutrients, water

Population

a group of individuals of the same

species that inhabit a given area-potential for interbreeding

Distribution

The distribution of a species or population describes its spatial location

Geographic range

The area that encompasses all individuals of a

species

Crude density

number of individuals per unit

area

•Dispersion

refers to the evenness of the population's distribution through space. There are three population disperson patterns

- Random—an individual's position is independent of others

- Uniform—results from negative interaction among individuals

- Aggregated (or clumped)—results from patchy resources, social groupings

Abundance

the number of individuals in the population

and defines its size

Population density

the number of individuals per unit area

- The area over which the population is distributed

age structure

proportion of individuals in different age classes

- Prereproductive

- Reproductive

- Postreproductive

Range expansion

-can occur naturally through changes in

climate or other environmental conditions

-can result when humans introduce

species to a region where they did not previously exist

Invasive species

non-native, people have intentionally or

accidentally introduced to our region

Phragmites (common reed)

Spreading throughout the midwest.

Now fills many wetlands in Illinois

Demography

is the study of populations

• Population growth

• Age structure

• Life Tables

Population growth

how the number of individuals in a population increases or decreases with time

- Individuals added via birth and immigration

- Individuals removed via death and emigration

Closed Populations

births and deaths are only factors operating.

exponential growth

The intrinsic rate of increase, r, is a measure of a population's potential for growth

arithmetical increase

over a given interval of time, an unvarying number of new units is added to a population.

exponential increase

occurs when the number of new units added to a population is proportional to the number of units that exists.

Birthrate

number of individuals born as a proportion of the

total population

death rate

is the number of individuals who die in a given time period (expressed as a proportion) of the total population.

- If r is less than zero (deaths exceed births) the population is shrinking.

- If r is zero, the population is at zero population growth.

intrinsic rate of increase

a measure of a population's potential for growth

Rate of change

described by the derivative of the equation, dN/dt=rN

Life table

age-specific account of mortality

cohort

is a group of individuals born in the same period of time

Life table variables

- x = age classes (in units of years here)

- nx = the number of individuals from the original cohorts that are alive at the specified age (x)

- lx = the probability at birth of surviving to any given age (x)

-dx = age-specific mortality = the difference between

the number of individuals alive for any age class (nx)

and the next older age class (nx + 1)

- qx = age-specific mortality rate = the number of

individuals that died in a given time interval (dx)

divided by the number alive at the beginning of that

interval (nx)

mortality curve

plots the qx column against age (x)

survivorship curve

plots the lx column against age (x)

Type I: Survivorship Curve

Type I: typical of populations in which individuals have long life spans, survival rate is high throughout the life span with heavy mortality at the end

-humans

-high parental care

-K-Strategists

Type 2: Survivorship Curve

survival rates do not vary with age

-Adult birds, rodents, reptiles, perennial plants

Type 3: Survivorship Curve

mortality rates are extremely high in early life

-Fish, invertebrates and plants

-have many offsprings

-r strategists

K-selected species

-population size fluctuates within narrow range

around carrying capacity (K)

-Reproductive rates (r) are lower, and often there is

parental investment in offspring

-stable environment

R (ruderal)

species rapidly colonize disturbed sites

C (competitive)

species are favored by predictable habitats

with abundant resources

S (stress-tolerant)

species survive in habitats where resources

are limited

reproductive effort

is the time and energy allocated to reproduction

Semelparity

the mode of reproduction in which an organism expends all of its energy in one suicidal act of reproduction

-The life span of semelparous species varies from several days (some insects)

to decades (cicada, bamboo)

Iteroparity

the mode of reproduction in which an

organism produces fewer young at one time and repeats

reproduction throughout its lifetime

- Vertebrates, perennial plants, shrubs, and trees

Altricial young

young are born or hatched in a helpless condition and

require considerable parental care (e.g., mice)

Precocial young

young emerge from the egg or womb ready to move

about and forage for themselves (e.g., ungulate mammals)

Density-dependent

effects influence a population in

proportion to its size

• As population density increases

a. The mortality rate increases (density-dependent mortality)

b. The fecundity rate decreases (density-dependent fecundity)

c. Or both the mortality rate increases and the fecundity rate decreases

logistic model of population growth

dN/dt = rN(1 - N/K)

Competition

occurs when individuals use a common

resource that is limited

Intraspecific competition

occurs among individuals of the same species

Scramble competition -

- when growth and reproduction are depressed equally across individuals

• can result in local extinction

Contest competition-

- when some individuals claim enough resources while denying others a share

• Only a fraction of the population may suffer

• Population is sustained by those that access resources

Exploitation

competition occurs when individuals indirectly interact with one another but affect the availability of shared resources (e.g., herbivores on the African savannas)

Interference

competition results when individuals directly interact and prevent others from occupying a habitat or accessing resources within it (e.g., bird species nesting sites)

Self-thinning

is the progressive decline in density and increase

in growth of remaining individuals caused by

- Density-dependent mortality

- Individual growth

home range

is the area that an animal normally

uses during a year

• Home range size varies with

- Food resource availability

- Mode of food gathering

- Metabolic needs

- Body size

- Sex

- Age

territory defense

By defending a territory, an individual secures sole access to an area and the resources that it

contains

• Methods of territory defense

- Song and call

- Spreading wings and tail (birds)

- Baring fangs (mammals)

- Attack and chase

- Marking with scents

Density-independent factors

factors influence population growth but are unrelated to population density

• They may influence birth and death rates of a

population but do not regulate population growth

Commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected

Ecological niche:

The range of physical and chemical conditions under which a species can persist, and the

array of essential resources it utilizes.

Fundamental niche:

The ecological niche of a species in the absence of interactions with other species.

Interspecific competition

a relationship that affects the populations of two or more species adversely

Lotka-Volterra Competition Model

A modified form of the logistic equation used to model interspecific competition.

competitive exclusion principle

states that "complete competitors" cannot coexist

Complete competitors

two species that live in the same place and have exactly the same ecological requirements

resource partitioning

Similar species coexist by partitioning available resources

- Different kinds/sizes of food

- Feed at different times

- Forage in different areas

- Exploit the portion of resources unavailable to others

Character displacement

involves a shift in feeding niche that subsequently affects a species' morphology, behavior, or

physiology

Predation

Is the consumption of one living

organism (the prey) by another (the predator)

• Simplest categories of predators: classes of

heterotrophic organisms

- Carnivore

- Herbivore

- Omnivore

predator (true predator)

kills its prey immediately upon capture, consumes multiple prey organisms, and functions as an agent of mortality on prey populations

herbivores (e.g., grazers and browsers)

consume only part of the plant and usually do not kill the plant

Parasites

feed on the prey organism (host) while it is still

alive, and their feeding activity is generally not lethal in the short term

Parasitoids

lay eggs on a host and when these eggs hatch,

the larvae feed on the host, slowly killing it

Prey

population growth equation includes two components

- The exponential model of population growth =

dN/dt = rN

Prey population growth equation

dNprey/dt = rNprey- cNpreyNpred

Predator population growth equation

dNpred/dt = b(cNpreyNpred) - dNpred

- Start with exponential model of population growth

• dN/dt = rN

- A birthrate term (b)

-A mortality rate

functional response

the relationship between the per capita rate of

consumption and the number of prey is the predator's

Type I Functional Response

There is a linear relationship between Nprey and the per capita rate of predation

- As # of prey increase, predators eat more of them

- Characteristic of passive predators (e.g., spiders, filter feeders)

- Predators are never satiated

Type II Functional Response

The per capita rate of predation increases in a decelerating fashion up to a maximum rate that is attained at some high prey density

- Predation approaches an asymptote

- Prey mortality rate declines with increasing prey density

Type III Functional Response

The rate at which prey are consumed is low at first, increasing in a sigmoid fashion as the rate of predation reaches a maximum

- The predator may prefer more abundant prey

- Initial rate of prey mortality increases with prey density but declines as rate of predation reached maximum

- This functional response that can potentially regulate a prey population

Availability of cover:

Availability of cover: the susceptibility of prey individuals will increase as the population grows and hiding places become filled

Search image

the ability of a predator to recognize a prey

species will increase as the prey population size increases

Prey switching

the act of a predator turning to a more abundant

(but maybe less preferred or palatable), alternate prey

numerical response

• reproduction by predators (b)

• movement of predators into an area of high prey density (aggregative response)

Coevolution:

as prey species evolve ways to avoid being

caught, predators evolve more effective means to capture them

Red Queen hypothesis

- For two interacting species, continuous change is needed just to maintain the fitness of one species relative to the other species it is coevolving with

Chemical defense (predator defense)

- Odorous secretions repel predators (e.g., arthropods, amphibians)

- Storage or synthesis of

toxins and poisons (e.g., arthopods, snakes)

Cryptic coloration (predator defense)

includes colors and patterns that allow prey to

blend into the background

Object resemblance

an organism resembles an object in the environment to avoid detection from predators

warning coloration (predator defense)

Animals that are toxic to predators or use other

chemical defenses often possess warning

coloration— these are bold color patterns that

serve to warn would-be predators

Batesian mimicry (predator defense)

--only one is dangerous

occurs when an edible species mimics the inedible species (the model)

- Butterflies and snakes

- Mimicry is not limited to color pattern (e.g., rattle-like sound)

Mullerian mimicry

---all are dangerous

is the similar color pattern shared by many unpalatable or venomous species

- Predator has to be exposed to only one of the species before learning to stay away from all other species with the same warning color patterns

Protective armor (predator defense)

(shells, quills) is used by some animals for defense

• A wide range of behavioral defenses is known to help prey

avoid or escape predators

- Living in groups

parasitism

a close association between two species is

beneficial to one (the parasite) and harmful to the other (the host)

-normally don't kill the host, but can reduce their fitness

-they are normally smaller and reproduce faster than hosts

Microparasites

are characterized by small size and a short generation time

- Viruses, bacteria, and protozoans

Macroparasites

are relatively large with a comparativel long generation time and usually involve intermediate

hosts and carriers

- Invertebrates (e.g., flatworms, ticks, lice) and fungi (e.g., rusts, smuts)

Hemiparasitic

plants take nourishment from host plant but also

photsynthesizes itself

Holoparasitic

plants are nonphotosynthetic completely

dependent on host for survival

Ectoparasites

are those that live on the host's skin within

the protective cover of feathers and hair

Endoparasites

live within the host (e.g., beneath the

skin, bloodstream, gills of fish, mouthparts)

definitive host.

The organism that is host to an adult parasite is known

as the definitive host

intermediate host.

The organism that is host to a juvenile parasite is known as an intermediate host

Mutualism

a relationship that is beneficial to both species

community

a group of species that occupy a given area, interacting either directly or indirectly

- A spatial concept

• A more restrictive definition of community is a subset of species

- E.g., bird community, plant community, etc

Species richness (S)

is the count of the number of species occurring within the community

Relative abundance

represents the percentage each species contributes to the total number of individuals of all species

rank-abundance diagram

common method to plot the relative abundance of each species against rank