Ecology Exam 1

Ecology

Ecology

The study of the interactions of organisms with one another and with their environment

The study of the distribution and abundance of organsism

Evolution

Change in population’s gene pool over time

science of the origins of biological diversity and its distribution

Ecological systems

1. individual

2. population

3. community

4. ecosystem

5. biosphere

Individual

most fundamental unit of ecology

species

individuals that are capable of interbreeding or share genetic similarity

Population

individuals of the same species living in a particular area and interbreeding.​

characteristics of populations (not individuals)

Geographic range (distribution) ​

Abundance ​

Density ​

Change in size​

Composition (demography) ​

Community

Populations of species living together in a particular area.​

Ecosystem

one or more communities of living ​organisms interacting with their nonliving ​physical and chemical environments.​ ( community+ physical and chemical environment= ecosystem)

Biosphere

all ecosystems on earth

Individual approach

Understands how adaptations, or characteristics of an individual’s morphology, physiology, and  behavior enable it to survive in an environment.​

Populations approach

Examines variation in the number, density, and composition of individuals over time and space.​

community approach

Understands the diversity and interactions of organisms living together in the same place.​

ecosystem approach

Describes the storage and transfer of energy and matter.​

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Biosphere approach

Examines movements of energy and chemicals over the Earth’s surface.​

Darwin’s 4 postulates

1. Individuals vary in their traits.​

2. Traits are heritable.​

(More offspring are born than survive)​

3.  Variation in traits causes some individuals to experience higher fitness (survival and reproduction).​

Producers

or autotrophs—convert ​

chemical energy into resources.​

consumers

or heterotrophs—obtain their energy from other organisms.​

Mixotrophs

can switch between being producers and consumers.​

Scavengers

consume dead animals

Detritivores

break down dead organic ​ matter (i.e., detritus) into smaller particles.​

Decomposers

break down detritus into simpler elements that can be recycled.​

types of species interactions

• predation

• parasitism

• herbivory

• competition

• mutualism

• commensalism

predation

when an organism kills or consumes an individual

parasitism

when one organisms lives in or on another organism.​

competition

when two organisms that depend on the same resource have a negative effect on each other.​

mutualism

when two species benefit from each other

commensalism

when two species live in close association and one receives a benefit, whereas the other is unaffected.​

Habitat

the place, or physical setting, where an organism lives.​

Distinguished by physical features, such as dominant plant type.​

Niche

the range of abiotic and biotic conditions an organism can tolerate.​

Hypothesis

ideas that potentially explain a repeated observation.​

predictions

statements that arise logically from hypothesis

Nemoria experiment and results

butterfly experiment where different conditions were used to determine what causes different phenotypes.

Results: diet changes development

Population approach

Examines variation in number, density, and composition of individuals over time and space​

Spatial Structure

the pattern of density and spacing of individuals in a population.​

Fundamental Niche

the range of abiotic conditions (e.g., temperature, humidity, salinity) under which a species can persist.​(all possible options)

realized niche

the range of abiotic and biotic conditions under which a species does persist.​ (reality)

Geographic range

a measure of the total area covered by a population (e.g., temperature and drought define the range of sugar maple).​

endemic

geographic range where species live in a single often isolated location

cosmopolitan

a measure of the total area covered by a population (e.g., temperature and drought define the range of sugar maple).​

abundance

the total number of individuals in a population that exist within a defined area (e.g., total number of lizards on a mountain).

Density

in a population, the number of individuals per unit area or volume; calculated by dividing abundance by area.​

Dispersion

the spacing of individuals with respect to one another within the geographic range of a population.​

Clustered dispersion

when individuals are aggregated in discrete groups (e.g., social groups or clustering around resources).​

Evenly spaced dispersion

when each individual maintains a uniform distance between itself and its neighbors (e.g., defended territories, croplands).​

Random dispersion

when the position of each individual is independent of other individuals; not common due to non-random environmental heterogeneity.​

Dispersal

the movement of individuals from one area to another.​(verb of dispersion, actual movement)

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Population abundance and range

Populations with high abundance also have large geographic ranges.​ (example: birds)

Population density and body size

The density of a population is negatively correlated to the body size of the species.​

Dispersal limitation

the absence of a population from suitable habitat because of barriers to dispersal.​

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Habitat corridor

a strip of favorable habitat located between two large patches of habitat that facilitates dispersal (e.g., a narrow band of trees that connects forests).​

Ideal free distribution

when individuals distribute themselves among different habitats in a way that allows them to have the same per capita benefit.​ (pizza example)

subpopulations

when a large population is broken up into smaller groups that live in isolated patches.​

Basic metapopulation model

a model that describes a scenario in which there are patches of suitable habitat embedded within a matrix of unsuitable habitat; all suitable patches are assumed to be of equal quality.​

Spatial structure models

• Metapopulation​

• Source-Sink​

• Landscape​

metapopulation

a set of local populations linked by dispersal​ : least complex

patches

suitable habitat

Matrix

barrier to dispersal

Source sink model

recognizes differences in quality of suitable habitat patches: intermediate complexity ​

Source patches : more food reproduce more

Sink patches: less resources less reproduction

Landscape model

• most complex

• considers effects of differences in the habitat matrix:​​

• the quality of a habitat patch can be affected by the nature of the surrounding matrix​​

• some matrix habitats are more easily traversed than others​

demography

The study of (the structure and growth of) populations​

What causes population increase?

birth and immigration

What causes population decrease

deaths and emigration

geometric growth

discrete time intervals (choppy points and lines)

exponential growth

time is treated as continuous (one smooth line no points). Continuous growth -- overlapping generations with year round reproduction

Geometric (discrete) growth

N(t + 1) = N(t) ​

where:N(t + 1)  = number of individuals after 1 time unit​

N(t)        = population size at time t​

N(t+1)

number of individuals after 1 time unit​

N(t)

population size at time t

Geometric Population growth

 = ratio of population size at any time to the population size 1 time unit earlier ​

  is the “per capita growth rate” ​ \n      or “finite rate of increase”:​

Geometric Population Growth for Multiple time intervals

Exponential population growth equation

Pe^rt

when a population is decreasing

λ<1 and r<0

when population is constant

λ=1 and r=0

when a population is increasing

λ>1 and r>0

Density independent limitations

factors that limit population size regardless of the population’s density.​ Common factors include climatic events (e.g., tornadoes, floods, extreme temperatures, and droughts).​

Density dependent limitations

factors that affect population size in relation to the population’s density.​

negative density dependence

when the rate of population growth decreases as population density increases.​ The most common factors that cause negative density dependence are limiting resources (e.g., food, nesting sites, physical space).​ (think about splitting the pie, the more people the less pie each person gets)

Shelf-thinning curve

a graphical relationship that shows how decreases in population density over time lead to increases in the size of each individual in the population; often has a slope of -3/2

positive density dependence

when the rate of population growth increases as population density increases (also known as inverse density dependence, or Allee effect).​ (typically happens when pop is so small that it makes it hard to find mates and reproduce)

Logistic growth model

a growth model that describes slowing growth of populations at high densities; it is represented by:​

Carrying capacity (k)

the maximum population size that can be supported by the environment.​

S- shaped curve

The shape of the curve when a population is graphed over time using the logistic growth model.​

Inflection point

the point on a sigmoidal growth curve at which the population has its highest growth rate.​

logistic growth model low in population size

N is small so the slope is higher rising in growth

logistic growth model with higher population size

N is closer to one so slope is smaller slowing growth

Age structure pyramids with broad base and narrow top (arrow shaped)

indicates population is growing because more babies are being born than in previous generations

Age structure pyramids with narrow base (v shaped)

Indicates that population is declining because less babies are being born than previous generations

Life tables

tables that contain class-specific survival and fecundity data.​

life table parts

x = age class​

nx = the number of individuals in each age class immediately after the population has produced offspring.​

sx = the survival rate from one age class to the next age class​

bx = the fecundity of each age class​

Number surviving to next age class

(nx) x (sx)​

number of new offspring produced

(nx) x (sx) x (bx)​

Type one curve

survivorship curve depicts a population that experiences low mortality early in life and high mortality later in life (e.g. bears, humans, elephants, whales).​

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type 2 curve

curve depicts a population that experiences constant mortality throughout its life span (e.g., squirrels, corals).​

type 3 curve

depicts a population with high mortality early in life and high survival later in life (e.g., weeds, fish, alligators).​

Cohort life table

a life table that follows a group of individuals born at the same time from birth to the death of the last individual.​

Static life table

a life table that quantifies the survival and fecundity of all individuals in a population during a single time interval.​

Does not take into account the effect of time ​

Works well with organisms with long lifespans ​

overshoot

when a population grows beyond its carrying capacity; often occurs when the carrying capacity of a habitat decreases from one year to next (e.g., because less resources are produced).​

Die- offs

a substantial decline in density that typically goes well below the carrying capacity.​ Die-offs often occur when a population overshoots its carrying capacity.

population cycles

regular oscillation of a population over a longer period of time.​

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delayed density dependence

when density dependence occurs based on a population density at some time in the past.​