ecology

EcologyStudy of the interactions between organisms and the living and non-

living components of their environment

• Ecology is a broad science involving:– Collecting information about organisms and

their environment– Observing and measuring interactions– Looking for patterns– Seeking to explain patterns

• Interdependence is when an organism’s survival depends of interactions with their surroundings.

Ecosystem: all the organisms and nonliving environment in a particular place

• Organism: one individual living thing• Habitat: the place where an organism

lives• Species: a group of organisms that is

able to reproduce together, share common genes and therefore resemble one another

• Population: includes all the members of a species that live in one place at one time

• Community: a group of interacting populations of different species

Energy Transfer• There is a hierarchy in the different levels of

organization within organisms. From the biosphere to the ecosystem, communities to populations, to organisms.

• Ecological models: a model that helps ecologists understand environmental interactions and predict changes. Used to help plan and evaluate solutions.

Deepwater Oil Rig Explosion

Energy Transfer• All organisms need energy to carry out life.• Autotroph: organisms that can capture

sunlight and “make their own food”, also called producers.

• Heterotroph: organism that relies on eating autotrophs or other heterotrophs, also called consumers – all animals!

• Within the ecosystem – the energy comes from the sun and flows to the autotrophs, then heterotrophs consume it.

Energy transfer

• Gross primary productivity is the rate at which the producers in an ecosystem capture the energy of sunlight: the organic molecules that they produce are referred to as biomass.

• When ecologists study the accumulation of biomass they refer to it as the net primary productivity.

• Think paychecks… gross vs. net

4 Labels• Herbivores: eat producers ex) antelope

eats grass• Carnivores: eat other consumers ex) lion

eats the antelope• Omnivores: eat both producers and

consumers ex) grizzly bear• Detrivores: (specifically called

decomposers) garbage feeders, ex) vulture cleans up carcasses and aids in decomposition

Energy Flow• Energy flows from an organism into the

one that consumes it. An organisms’s trophic level indicates the position in a sequence of energy transfers. All producers are in the first trophic level, herbivores in the second, and predators in at least the third

• Many ecosystems can only support 3 – 4 levels, marine can do much more.

• Only about 10% of available energy is transferred to the next trophic level.

Populations

• Species richness: how many species are in an area vs. species eveness: the abundance of each species

• Richness is a count and will change with latitude in general, the closer to the equator you are the more species you’ll see

Species

• Species-area effect is seen when you have a larger area, you’ll have more species than in a small area.

• Species interactions and richness: some species are necessary to maintain the number of other species ex) less beef cows = less Ramseys

Populations

• Disturbance is any event that could change an environment- earthquake, tornado, flood, volcano

• Stability is the ability of a community to maintain constant conditions (similar to homeostasis in humans)

Succession

• Gradual sequential re-growth of an area.• Primary sucession: development in an

area previously not supporting life• Secondary sucession: sequential

replacement of species that follows disruptions on existing communities

Succession• Pioneer species – small, quick

growing fast to reproduce, predominate species ex) lichens and grasses on volcanic slopes

• Primary succession occurs slowly- the soil is too poor to sustain much, it takes a while to build up organic material enough to support larger plants. The final stage of succession is called the climax community – very stable.

Patterns of Mortality

• Survivorship curves show the probability of members in a population to survive to a certain age– Type I – likelihood of dying isn’t until late

in life (humans)– Type II – likelihood of dying doesn’t

change through life (bugs)– Type III – very likely chance of dying

young (bears)

Measuring populations

• Charles Darwin calculated that one pair of elephants could increase to a population of 19 million individuals within 750 years.

• Why aren’t we overrun with elephants?

• Immigration changes the population, it moves individuals into a population

• Emigration is the movement of individuals out of a population.

• Usually we discuss populations by the thousands, we present data “per capita”

Growth Models

• Exponential Model: a steady growth rate and pattern of rapid increase. At this rate, more individuals are added than die off each year. When graphed, a J-shaped curve is shown. We see when the population is small, it grows slowly but as we get larger the faster it grows. 2 cows don’t reproduce as fast at 200.

Growth Models• Logistic Model: builds on the exponential

model but accounts for limiting factors.• A limiting factor is anything that restrains

the growth (money, space)• The carrying capacity of enviroment is

how many individuals the area can support over a period of time.

• This graph looks like an S; when population is small, birth rates are high and death is low. As it increases, birth rates go down and death rates increase

Population Regulation• 1. Limiting factors

Density-independent factors: weather, flood, fire, reduce the population regardless of the size by the same proportion

Density-dependent factors: resource limitations will determine the population size

Population Regulation• 2. Populations naturally fluctuate. Ex)

Charles S. Elton (1900-1991) saw that the number of lynx and those of hares followed similar fluctuations.

• Not what you think though- it wasn’t due to predation. On an island without lynx, the hares still fluctuated!

• 3. Perils of small populations– Rapid growing human populations have

caused extreme reductions in population of other species.

• Perils, cont.– Only around 200 Siberian tigers remain

in the wild because of hunting and destruction of habitat

– California’s condor population in the 1980’s had dropped to only 9 individuals. Now there are 192 in the wild, 391 total live birds. They are the largest North American land bird.

Small populations• Small populations are extremely

suceptible to extinction. Environmental factors can stress their environment (food, shelter) and either kill off all individuals of leave just a few to repopulate. (Shallow gene pool?) This leads to genetic vulnerability. The less variety, less likely to adapt for survival.

Human Population growth• 10-12,000 years ago the population

was small, we had a hunter-gatherer lifestyle with high child mortality rates.

• Agricultural revolution – 12,000 years ago led to domestication of animals and a steady food supply- population grew faster and mortality rates went down.

• Theory says that industrial development causes socioeconomic changes, visible is 1-3 generations.

Biotic and Abiotic factors

• Biotic factors are all the living aspects of an ecosystem

• Abiotic factors are the physical and chemical characteristics fo the environment.

Abiotic Factors• Temperature• Humidity• pH• Salinity• Oxygen concentration• Amount of sunlight• Availability of nitrogen• Precipitation

• Abiotic factors are not constant, not independent of biotic factors and they vary from time to time and place to place

• Tolerance is how well something can survive at a given point.

• A tolerance curve is a graph that shows how well an organism can function and survive outside its optimal range. This curve shows performance at a given variable like temperature on fish.

• Acclimation – some organisms can adjust their tolerance to abiotic factors.

Control of Internal Conditions• Conformers are organisms that

don’t regulate their internal conditions- they change as their external environment changes

• Can you think of an example of this?• Regulators are organisms that use

energy to control some of their internal conditions they can remain in optimal range over a wide

• Can you think of an example of this?

Escape!

• Some animals can escape temporarily from unfavorable conditions

• Dormancy- a long term strategy of reduced activity

• Migration – moving to a more favorable habitat

• Do humans do this? How?

• Niche: the specific role of life an organism plays within its environment

• Generalists – species with a broad niche, can tolerate wide range of conditions & use a variety of resources

• Specialists – species with narrow niches (Ex. Koala Bear with the eucalyptus tree leaves)

Competition• Interspecific: 2 or more species

use the same resource, one wins• Ex) deer + quail + rabbits• Intraspecific: competing within

one species (which is more intense?)

• Intra- they all use the same resource in the same way so it comes down to who is genetically superior.

Predator + Prey

• Natural Selection (survival of the fittest) favors the predator that can adapt and overcome

• Prey use mimicry – looking like another species to prevent predation

Mimicry• Batesian – looking like a dangerous species• Mullerian – 2+ dangerous or distasteful

(bees & wasps are black and yellow)• Plants also have developed defenses-

physical and chemical (secondary compounds)

• Predation and competition will decrease the niche size of a species

• Fundamental niche is the range a species can potentially tolerate

• Realized niche is the actual range

Symbiosis

• Parasitism: one is harmed and one benefits

• Mutualism: both get some benefit• Commensalism: one benefits while

the other isn’t harmed or helped

Why do we have weather?

• Latitudinal variation in sunlight intensity.

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Why do we have weather?Seasonal variation in sunlight intensity.

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Why do we have weather?Global air circulation and precipitation patterns.

Why do we have weather?

• Global wind patterns.• Currents and other bodies of water.

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Earth’s biomes

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Tropical rainforest

distribution: equatorialprecipitation: very wettemperature: always warmcharacteristics: many plants & animals, thin soil

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Savanna

distribution: equatorialprecipitation: seasonal, dry season/wet seasontemperature: always warmcharacteristics: fire-adapted, drought tolerant plants; herbivores; fertile soil

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Desert

distribution: 30°N & S latitude bandprecipitation: almosttemperature: variable daily & seasonally, hot & coldcharacteristics: sparse vegetation & animals, cacti, succulents, drought tolerant, reptiles, insects, rodents, birds

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Temperate Grassland

distribution: mid-latitudes, mid-continentsprecipitation: seasonal, dry season/wet seasontemperature: cold winters/hot summerscharacteristics: prairie grasses, fire-adapted, drought tolerant plants; many herbivores; deep, fertile soil

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Temperate Deciduous Forest

distribution: mid-latitude, northern hemisphereprecipitation: adequate, summer rains, winter snowtemperature: moderate warm summer/cool wintercharacteristics: many mammals, insects, birds, etc.; deciduous trees; fertile soils

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Coniferous Forest (Taiga)

distribution: high-latitude, northern hemisphereprecipitation: adequate to dry (temperate rain forest on coast)temperature: cool year roundcharacteristics: conifers; diverse mammals, birds, insects, etc.

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Arctic Tundra

distribution: arctic, high-latitude, northern hemisphereprecipitation: dry temperature: cold year roundcharacteristics: permafrost, lichens & mosses, migrating animals & resident herbivores

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Alpine Tundra

distribution: high elevation at all latitudesprecipitation: dry temperature: cold year roundcharacteristics: permafrost, lichens, mosses, grasses; migrating animals & resident herbivores

Aquatic/Marine Biomes– Account for the largest part of the

biosphere in terms of area– Can contain fresh (aquatic), brackish,

or salt (marine) water• Oceans

– Cover about 75% of Earth’s surface– Have an enormous impact on the

biosphere

Lakes• Oligotrophic - nutrient

poor, oxygen rich• Eutrophic - nutrient rich,

oxygen poor– Periodic oxygen

depletion; large amount of decomposition

• Life- fish, invertebrates depending on O2 levels

An oligotrophic lake in Grand Teton, Wyoming

A eutrophic lake in Okavango

delta, Botswana

LAKES

Wetlands• Inundated with water at

least periodically• Plants adapted to water-

saturated soil• Highly productive• Important filters and

breeding grounds• Birds, carnivores,

crustaceans, plants, reptiles.

WETLANDS

Okefenokee National Wetland Reserve in Georgia

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Streams and Rivers• Current with lots of

aeration• Aquatic plants and

phytoplankton, fish, invertebrates, etc.

STREAMS AND RIVERS

Figure 50.17A headwater stream in theGreat Smoky Mountains

The Mississippi River farform its headwaters

Estuaries• Transition between rivers

and sea - brackish water with flow between the two.

• Variable salinity depending on temperature, depth, and tides.

• Worms, oysters, crabs, fish, etc.

• Highly productive and important in filtering water.

Figure 50.17 An estuary in a low coastal plain of Georgia

ESTUARIES

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Intertidal Zones• Periodically submerged

and exposed.• Physical environment

varies vertically, so species range varies vertically.

• Oxygen and nutrients renewed tidally.

• Sea grass, algae, worms, crustaceans, crabs, etc.

Figure 50.17

INTERTIDAL ZONES

Rocky intertidal zone on the Oregon coast

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Oceanic Pelagic Biome

• Open ocean, particularly deep water.• Driven by currents - lots of light and oxygen. Large photic zone.• Experience nutrient turn over - depends on temperature.• 70 percent of world’s surface - we will be going to Ocean Hall!• Phytoplankton and photosynthetic bacteria - makes our oxygen!• Zooplankton, fish, cephalopods, marine mammals, etc.

Figure 50.17Open ocean off the island of Hawaii

OCEANIC PELAGIC BIOME

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Coral Reefs• Formed from coral “skeletons”• Photic zone - zooxanthellae

need light for photosynthesis; sensitive to change in temperature

• Fringing reef --> barrier reef --> atoll island

• Unicellular algae, coral animals, fish and invertebrate diversity.

Figure 50.17A coral reef in the Red Sea

CORAL REEFS

Marine Benthic Zone• Below neritic (near, coastal) and

pelagic (noncoastal, open water) zones.

• Deep benthic = abyssal zone; deep sea vents with chemoautotrophs.

• Shallow benthic - oxygen from algae and seaweed.

• Chemo- or photo- autotrophs; worms, arthropods, echinoderms, etc.

A deep-sea hydrothermal vent community

MARINE BENTHIC ZONE

DONE!