EXAM 3: Ch. 52 & 53 (part one)

Organismal Ecology

includes physiological, evolutionary, & behavioral ecology

Population Ecology

• focuses on factors affecting population size over time

• studies populations in relation to their environment

Community Ecology

examines the effect of interspecific interactions on community structure & organization

Ecosystem Ecology

emphasizes energy flow & chemical cycling between organisms & the environment

Landscape Ecology

exchanges of energy, materials, & organisms across multiple ecosystems

Global Ecology

examines the influence of energy & materials on organisms across the biosphere

Earth’s climate varies by

latitude & season; changing rapidly

Climate

long-term prevailing weather conditions in an area

Physical Components of Climate

1. sunlight

2. temperature

3. precipitation (rainfall, snow, ice)

4. wind

Solar energy determines

1. temperature variation

2. circulation of air

3. circulation of water

4. evaporation of water

Latitudinal variation determines

1. angle of sun

2. which varies sunlight intensity

3. which causes season variation (temperature/precipitation)

The tilt of the Earth causes

incidental sunlight & creates the season variation

Solar radiation causes

global patterns of air circulation & precipitation

Pattern of air circulation & precipitation

1. wet warm air rises over equator, due to temperature

2. as air cools & expands in upper atmosphere, rain falls over equator

3. dry cold air masses return to Earth, absorb water from land (30°); deserts

4. as air cools & expands in upper atmosphere, rain falls over land (60°)

Surface winds are named by

the direction they originate from

Tradewinds

northeasterly, southeasterly - blow towards equator

Westerlies

west-east winds 30° N/S to 60° N/S - blow towards poles

Large bodies of water moderate

the climate of nearby land

Mountains influence air flow

over land & affect climate in the area

Windward Side

• warm air cools as it rises up the mountain

• releases moisture on windward side

Leeward Side

• cool dry air descends down mountain

• it warms as it descends; picking up any moisture from land

• creates a rain shadow on leeward side; arid region

Every 1000m increase in elevation

• drops temp 6°C

• equal to change at different latitudes

Every environment on Earth is characterized by a

mosaic of small-scale differences in abiotic & biotic factors that influence the distribution & abundance of organisms

Global Climate Change

• directional change to global climate

• lasts three decades or more

Why is global climate change happening?

• increasing carbon dioxide

• deforestation - trees take CO2 out of the atmosphere

• burning fossil fuels - adds CO2 to the atmosphere

What are signs of global climate change?

• wind patterns shifting

• precipitation patterns shifting

• global temperature has increased

• extreme weather events have increased

Current range & predicted ranges (American Beech)

• beech needs to move 4-6 miles/year to remain in favorable climate

• has only moved 0.12 miles since ice age

Seeds can travel by many mechanisms to

spread to further range

The distribution of terrestrial biomes is controlled by

climate & disturbance

Biomes are

major life zones

Terrestrial Biomes

• climate is major factor

  • precipitation & temperature

• northern vs. southern hemispheres

• vertical layering - important feature

Distant Biomes

similar environments create convergent evolution

Cacti in North America & Euphorbs in African deserts

convergent evolution, analogous features

Hawaiian Islands

tourist area is leeward side

Disturbance (terrestrial biomes)

• an event that changes a community

  • fire, flood, hurricane

  • human activity (MAJOR THREAT): pollution - global warming, urban areas - habitat loss/fragmentation, farms - habitat loss/fragmentation

Climograph

plots the annual mean in temperature & precipitation in a region

Aquatic Biomes

• less latitudinal variation than terrestrial biomes

• marine biomes average salt concentration of 3%

• oceans make up largest biome - 70% Earth

What is the average salt concentration of freshwater biomes?

< 0.1%

Freshwater biomes influenced by

1. surrounding terrestrial biome

2. patterns of water

3. speed of water

Many aquatic biomes are stratified into zones defined by

1. light penetration

2. temperature

3. depth

Pelagic Zone

• “open sea”

• open water area; not close to shore

• has photic & aphotic zones

Upper photic zone (pelagic)

• sufficient light for photosynthesis

• most organisms live in photic zone

• abundant sunlight

Lower aphotic zone (pelagic)

• receives little light; sunlight is sparse

• extensive zone, but little life found there

• abyssal zone - 2000 to 6000m

Benthic Zone

• bottom zone - deep or shallow water

• organic or inorganic sediment at bottom

• benthos are communities of organisms living there

• detritus falls from productive surface waters = food source

Littoral Zone

• area near shore

• submerged plants final area

Limnetic Zone

• deeper water past shore

• within photic zone

Intertidal Zone

area between high tide/low tide

Neritic Zone

from low tide to continental shelf

Oceanic Zone

everything else; divided into three parts

Thermocline

• in oceans & lakes

• temperature boundary separates warm & upper lower cold H2O

Turnover

• mixes oxygenated water of surface & nutrient rich water of bottom

• tropical lowland lakes & ocean have year round mixing of water

• temperate lakes undergo semiannual mixing of water

Aquatic Biome Characterization

1. physical environment (light penetration; temperature; depth)

2. chemical environment (salinity; oxygen concentration; nutrient density)

3. geologic features

4. photosynthetic organisms (autotrophs)

5. heterotrophs

6. human impact

Biotic factors that affect the distribution of organisms

1. predation

2. herbivory

3. competition

4. mutualism

5. parasitism

abiotic factors that affect the distribution of organisms

1. temperature

2. water

3. oxygen

4. salinity

5. sunlight

6. soil

Most abiotic factors vary in

space & time

Population ecology determines how

biotic & abiotic factors influence population density, dispersion, & demography

Population

• a group of individuals of single species living in same general area

• described by boundary & size

Density

• number of individuals per unit area or volume within set boundary

  • ex: number of E. coli in a test tube; number of oak trees in a park

Dispersion

• pattern of spacing among individuals within their boundary

• environmental & social factors influencing spacing

Demography

study of birth/death/migration/vital rates of a population over time

Population size (density) can be estimated by

extrapolation from small samples

Mark-Recapture Method

1. capture organism

2. tag (mark) organism

3. release tagged organism (s = number tagged & released)

4. scientists recaptured a 2nd sample of individuals (n)

5. note how many are marked (x) in 2nd sample

6. estimated population size (N = sn/x)

Images of animals can be used

to identify animals - spot patterns, fin shapes, etc.

Density is the result of

• interplay between processes that add or remove individuals from a population

  • birth = adds

  • immigration = adds

  • death = removes

  • emigration = removes

Clumped Dispersion

• individuals aggregate in patches

• most common pattern of dispersion

• influenced by 1. resource availability 2. mating behavior 3. group predator defense

Uniform Dispersion

• individuals are evenly distributed

• influenced by 1. social interactions 2. territoriality

Random Dispersion

• pattern of each individual is independent of other individuals

• not influenced by 1. strong attractions 2. strong repulsions

• uncommon in nature

Life Tables

• summarize demographic information

• age specific summary of 1. survival rates 2. reproductive rates

• follow the fate of a cohort

  • same aged group followed from birth-death

  • tracks proportion of cohort that survives from one age group to the next

  • males usually ignored; females produce offspring

  • population is viewed as females producing new females (offspring)

Survivorship Curve

• graphic way to represent data in life table

• three types - Type I, Type II, Type III

• most species are intermediate to these curves

Type I Survivorship Curve

• large mammals, few offspring, care for young

• low death rates early & mid life; deaths increase in older age

Type II Survivorship Curve

• rodents, invertebrates, annual plants

• constant death rate over organism’s life span

Type III Survivorship Curve

• produce large numbers of offspring; little/no care

• high death rates in young, lower death rate of survivors

Reproductive Rates

• counts number of females in age group

• counts average number of female offspring produced by females

• age specific reproductive rates vary considerably by species

• overharvesting can lead to population collapse

Exponential Population Growth

• describes population increase under idealized conditions

• dN/dt = the rate at which the population is increasing in size at each moment in time

  • N = current population size

  • r = constant; the intrinsic rate of increase/growth

  • r = the per capita (per individual) rate at which an exponentially growing population increases in size at each instant in time

Exponential population growth cannot be

sustained for very long in any population

Carrying Capacity

• a more realistic population model limits growth by incorporating K

• K = maximum population size the environment can support

• varies with abundance of limiting resources

• food, shelter, refuge from predators, nesting sites, etc.

Logistic Population Growth Model

• produces a sigmoid curve

• individuals are added to population most rapidly at N = K/2

• when N approaches K, growth rates slow down

• births decrease; deaths increase

• when N=K, the population stops growing

Logistic Population Growth Model Importance

• useful as a starting point for thinking about how populations grow & constructing more complex models

• important for predicting how population will recover from small size, estimating sustainable harvest rates for wildlife populations, determining critical size at which animals may go extinct

Life history traits are products of

natural selection

Life History

• traits that affect an organism’s schedule of reproduction & survival

• why we should not overharvest or overfish

Key Components of Life History

1. when an organism reaches sexual maturity

2. how often the organism reproduces

3. how many offspring are produced per reproductive episode

Semelparity

• semel = once & parere = to beget

• Big Bang reproduction

• produce once then die: salmon

• in hostile environment, adult & offspring likely to die

Iteroparity

• iterare = to repeat & parere = to beget

• repeated reproduction

• produce offspring multiple times while fertile

• in dependable environment, both adult & offspring tend to survive

Life histories represent an

• evolutionary resolution of conflicting demands

• limited resources mandate trade-offs between investment in reproduction & survival

Categorizing the diversity of life history based on variables of logistic equation

1. K-selection

2. r-selection

K-selection

• selection for traits that are advantageous at high densities

• operates in populations living near limits imposed by resources (carrying capacity)

• competition among individuals of population is strong

r-selection

• selection for traits that are advantageous at low densities

• maximizes intrinsic rate of increase r

• competition among individuals of population is weak

Density-Dependent factors regulate

population growth

Mechanisms of Density-Dependent Regulation

1. competition for resources

2. disease

3. predation

4. territoriality

5. intrinsic factors

6. toxic wastes

Competition for Resources (density-dependent regulation)

• plants are stuck where they are

• use of fertilizers on crops to increase yield

Disease (density-dependent regulation)

• more dense populations spread diseases more easily

• less resources, more stressed physiologically, get sick

Predation (density-dependent regulation)

• dense population, prey is more abundant, may be selected

Territoriality (density-dependent regulation)

• when space is resource of competition

• surplus of non-breeding males is a sign

Intrinsic Factors (density-dependent regulation)

• physiologic factors that regulate population size, even with resources

Toxic Wastes (density-dependent regulation)

• as density increases, so do toxins, alcohol for yeasts

• global warming, etc. for humans

No population can

increase indefinitely (humans are no exception)

Age structure diagrams can (pyramids)

help predict a population’s growth trends

Ecological Footprint

summarizes aggregate land & water area needed to sustain a person, city, or nation (provides all resources one consumes & absorbs all the waste one generates)

Types of Lakes

1. oligotrophic

2. eutrophic

Types of Wetlands

1. marsh

2. bog

3. swamp