Ecology

Ecology

Climate Drives

EcologyBoth the sun and the seasonal variation of

the earth impact ecology.

The sun is the primary provider for energy for all of life.

The seasons (due to the tilt in the earth’s axis(~23.5°)) create

variability and change in the environment.

Water and it’s Impact on Climate

Water is warmed at the equator and flows towards the poles, where it cools.

The water can moderate climate of nearby land.

Climate Controls Terrestrial Biomes

Temperate Broadleaf Forest Tundra Tropical Forest

Savanna Northern Coniferous Forest Desert

Aquatic Biomes

Make up most of the largest of all biomes.

Similarly diverse as terrestrial biomes.

Characterized by their physical

environment: salt, light, soils, and biotic factors.

Zonation in Aquatic Biomes

Zonation depends upon: 1) Light

penetration 2) Distance

from shore and water depth

3) Open water vs. bottom

Different Zones = Different Environment!

Intertidal Zone Oceanic Pelagic Zone Benthic Zone

River Lake Coral Reef

Wetlands Estuaries

Ecological Perspective - What is being studied?

Population EcologyStudying what variables affect, influence,

and drive populations of organism.

What drives a population?

Density

Dispersion

Demography

Population DensityNumber of individuals in a given area.

Density is constantly in flux; individuals are being added or removed all the time.

Dispersion: Spacing of individuals

in a population

Populations may vary how they space themselves for

various reasons.

1) Protection

2) Territoriality

3) Mating

4) Feeding

Demography – the vital statistics and how they

change

Birth rates Death rates Demographics of a population

Done by following a cohort from birth until death.

Each year the number of individuals are determined and the proportion of surviving members is calculated.

Methods of Displaying Population Death Rate: Life Table

Life Table

Survivorship CurveVisual representation of life tables 3 Major types: I – low early death rates and a steep drop in death at older ages.II – relatively constant rate of death of the life span of the population.III – high death rates for young and lower death rates for older individuals.

Population Growth

Food Reproduce

Grow

In order for a population to grow these

criteria must be met to some

degree.

Exponential Growth

If access to food and reproduction are

unlimited and there are no restrictions a population may grow

exponentially.

J-shaped

Maximum rate of increase is constant,

but the number of individuals over time at

a greater rate.

Seen in populations introduced to new

environments or those rebounding.

Logistic GrowthUnlimited resources are

rarely seen. As the population density increases, resource

availability decreases.

There is a limit to the number of individuals that

the environment can support: Carrying

Capacity (K).

As K is reached, the population will remain

relatively constant, fluctuating slightly.

Logistic Growth and Real Populations

Population Growth and Natural Selection: How and why do

Populations Grow?K-selection: Traits that are sensitive to population density, and are favored at high densities (near K).

r-selection: Traits that maximize reproductive success. Tactics that allow

for fast population growth.

Population Growth Regulation

Den

sity D

ep

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Density

Ind

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If a birth or death rate is influenced by the population density.

• Competition for resources

• Predation due to availability

• Waste accumulation

• Disease

• Territoriality

If a birth or death rate is NOT influenced by the population density.

Ultimately Populations Fluctuate Yearly – Population

Dynamics

Community Ecology

Ecological Niche

An ecological niche is related to an organism’s “position” in a community (think job).

The “job” is related to its ability to rather resources effectively and allow for that organism to reproduce and thrive.

2 species competing for the same resources in the same area cannot coexist – competitive exclusion suggests that the slight differences in the species will lead to some ecological advantage for one species, leading to the elimination of the less fit species.

Resource Partitioning

Community Interactions are Classified Based on Help, Harm, or

no Effect

1) Competition: (-/-)Different species

compete for the same limited resource

Competitive Exclusion

Ecological niche

2) Predation: (+/-)One species kills and

eats the other.

Adaptations by predators to improve

success.

Prey often display adaptations for defense: aposematic coloration,

mimicry, etc.

3) Herbivory: (+/-)Predation of plants

Most herbivores are invertebrates

Herbivores are adapted to seek out proper plants

Plants also have defense mechanisms

4) Facilitation: (-/-)

One species has a positive effect on

another

Symbiosis: 2 or more species in direct and intimate

contact

Parasitism(+/-)

Mutualism(+/+)

Commensalism

(+/0)

Community Structure

Species Diversity

Species Richness

Relative Abundanc

e

Community Structure: Trophic Levels

Autotrophs (primary producer) Herbivores (primary consumer) Carnivores (secondary, tertiary, etc.

consumer) Detritivores (decomposer)

Energetic hypothesis: Food chain length limited by inefficiency of energy transfer (~10% per “link”).

Dynamic Stability hypothesis: Long food chains are less stable due to magnification up each link.

Community Structure: Food Web

Species with a Large Impact

Dominant Species:

most abundant

with greatest biomass

Keystone Species:

not abundant but exert

great control over

community structure

Disturbance and it’s Impact on the Community

Disturbance can create species diversity and improve the overall survival of a community.

Some species rely on disturbances to complete their life cycle

New York Pine Barrens

Ecological Succession

Ecological succession in Glacier Bay, Alaska after glacier retreat:

Ecosystem Ecology

Energy Flow and Chemical Cycling

1st Law of Thermodynamics: Energy cannot be

created or destroyed

Energy enters through sunlight

Transferred to other organisms via food

chains/webs

2nd Law: Entropy

Energy is lost through heat

Chemical elements are continually cycled through an ecosystem.

Overview of Energy and

Nutrient Dynamics in an

Ecosystem

Energy limits ecosystem production!

Without enough energy input primary

producers cannot support trophic levels

above them.

The same can be said for various nutrients:

limiting nutrients.

Ecosystem Energy Budget

Despite the large amount of solar radiation that bombards the earth daily, only a small amount is used in photosynthesis. ~1% is used for photosynthesis!

GPP = amount of energy from light converted to chemical energy.

NPP = GPP – energy used by primary producers to make energy. This is the energy available to consumers – the energy that moves up the food chain/web.

Energy Transfer Between Trophic Levels

Much of the energy consumed by an organism in a trophic level above consumers is lost to heat through undigested feces, respiration, etc.

~1/6 energy consumed is used for growth (secondary production).

Trophic Efficiencies

Amount of product transferred from one

trophic level to the next.

Much of the energy from one trophic level is lost

due to heat.

~10% of the available energy is passed to the

next trophic level.

Similar Trends are Established for Biomass and

Density

But Why???

Biogeochemical CyclesFor each of the

biogeochemical cycles please note:

Biological importance

Forms available to life

Reservoirs – biotic or abiotic accumulations of a particular chemical that living things draw nutrients from and also return the nutrient to

Key processes – driving factors for each cycle

Water Cycle