14. Introduction to ecology

What is ecology?

the scientific study of the interactions between organisms and the environment

• the interactions determine distribution of organisms and their abundance

  • ecology reveals the richness of the biosphere

    • Ecology derived from: Oikos = home & Logos = study

Levels of Ecology

Ecologist work at levels ranging from individual organisms to the planet:

• Global, landscape, ecosystem, community, population, organismal

organismal ecology

this ecology studies how an organism's structure, physiology and behaviour (for animals) meet environmental challenges

What is a population?

A population is a group of individuals of the same species living in an area

population ecology

Population ecology focuses on factors affecting how many individuals of a species live in an area

What is a community?

A community is a group of populations of different species in an area

COmmunity Ecology

Community ecology deals with the whole array of interacting species in a community

What is an ecosystem?

An ecosystem is the community of organisms in an area and the physical facors with which they interact

Ecosystem ecology

Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotive components

What is a landscape?

A landscape is a mosaic of connected ecosystems

Landscape ecology

Landscape ecology deals with arrays of ecosystems and how they are arranged in a geographic region

What is the biosphere?

The biosphere is the global ecosystem

• essentially the sum of all the planet's ecosystems

Global ecology

Global ecology examines the influence of energy and material on organisms across the biosphere

The ecological levels of organization

organisms → population → community → ecosystem → landscape → biosphere

Regional effects on climate: Seasonality

In middle to high latitudes, Earth's tilted acis of rotation and it's annual passage around the sun cause strong seasonal cycles in day length, solar radiation and temperature

Regional effects on climate: bodies of water

Ocean currents influence climate along the coasts of continents by HEATING or COOLING overlying air masses that pass across the land

• coastal regions are also generally wetter than inland regions

Regional effects on climate: Mountains

Mountains influence air flow over land

• As warm, moist air approaches a mountain it is released on the windward side

  • This causes the leeward side to be dry

Biomes

These are the major ecological associations that occupy broad geographic regions of land or water

• Varying combinations of biotic and abiotic factors determine the nature of biomes

  • Includes terrestrial and aquatic

Terrestrial biomes Features

these are defined by vegetation type

• Terrestrial biomes are named for major physical or climatic features and for their dominant vegetation

  • Vertical layering of vegetation is an important feature

  • layering of vegetation creates different habitats for animals

Climograph

Shows how climate affects the distribution of biomes .

Tropical forests

Climate: Temp is usually high.

• Rain forests get 200-400cm of rain annually

• Dry forests get 150-200 cm annually

Organisms: Vertically layered forests and plants compete for light

• Tropical forests is home to millions of species

  • has the highest animal diversity than any other terrestrial biome

Savanna

Climate: Temp averages 14-19 degrees C

• Rainfall averages 3-50 cm per year and is seasonal

Organisms: Scattered trees that are often thorny

• Fires are common in dry season and dominant plant species are fire adapted

  • Grasses and forbs primary ground cover

  • Large herbivores mammals and their predators are common

Desert

Climate: Temp varies seasonally & daily

• >50 degrees in hot deserts

• <30 degress in cold deserts

Organisms: Dominated by low widely scattered vegetation

• Plant adaptations: tolerance to heaet, water storage, reduced leaf area, physical defenses against herbivores

Chaparral

Climate: Annual precipitation 30-50cm

• Has rainy winters and dry summers

  • fires occur routinely

Organisms: Dominated by shrubs, small trees that are fire adapted

• Some shrubs germinate only after fires and are adapted to drought

  • Animals include broswers such as deer and goats; many insects, small mammals, amphibians and birds

Temperate grassland

Climate: Annual precipitation 30-100cm

• has dry winters and wet summers

Organisms: Dominated by grasses and forbs

• Grassland plants are adapted to drought & fire

  • Grazing by large animals, such as bisons & wild horses, prevent establishment of trees

    • Burrowing animals are common

Northern coniferous forest

Climate: Annual precipitation 30-70cm

• winters are cold and has a large annual temp range

Organisms: Conifers are common and some depend of fire to regenerate

• Plant diversity lower than broadleaf forests

  • Many migratory birds nest in coniferous forests

    • Mammals include moose, brown bears and siberian tigers

      • Insect outbreaks can kill trees

Temperate broadleaf forest

Climate: Annual precipitation 70-200cm

• winter low to about 0 degrees and has humid summers up to 35 degrees

Organisms: Dominant plants are deciduous trees

• In Austrailia, evergreen eucalyptus trees are common

• In the northern hemisphere, many mammals hibernate while birds migrate south

Tundra

Climate: Annual precipotation 20-60 cm in arctic tundra and up to 100cm in alpine tundra

• Winters are cold while summers only reach 10 degrees

Organisms: Vegetation mostly herbaceous, such as mosses, grasses and forbs

• Musk oxen resident; migratory caribou

  • Predators include: bears, wolves, foxes and snowy owls

    • Many migratory birds breed on tundra in the summer

Aquatic biomes Vertical zones

Called the Pelagic Zone

• Photic zone - the top layer with the most light penetration

• Aphotic Zone - Below the photic zone and has the least light penetration

Aquatic Biomes Horizontal zones

Called the Benthic zone

• Littoral zone - closest to the shore and touches it

• Limnetic zone - past the littoral zone

Wetlands and Estuaries

Physical Environment: Wetlands has water at least some of the year

• Wetlands can develop shallow basins, along flooded river banks, or on the coasts of large lakes and seas

• Estuary is a transition between river and sea

  • They are highly productive habitats

Organisms:

• Water saturated soils favour growth of plants such as cattails & sedges

  • Herbivores include: crustaceans, aquatic insect larvae, muskrats

    • Predators include: dragonflies, frogs, alligators and herons

• Estuaries support oysters, crabs and fish

Why are wetlands good?

Wetlands act like giant sponges

• they soak up rain and snowmelt and release water in drier season

  • they reduce soil erosion and flooding and filter water

Streams and Rivers

Physical environment: Headwaters clear and cold, downstream water is warmer and more turbid

Organisms: Headwaters may be rich in phytoplankton or rooted aquatic plants

• Diverse fishes and invertebrates inhabit unpolluted streams and rivers
  

Intertidal Zones

Physical environment: Periodically submerged by tides twice daily

• upper strata experience more exposure to air and greater variations in temp & salinity

Organisms: Includes diverse marine algae while sandy zones lack attached plants or algae

• Some animals adapted to attaching to rocks

  • many bury themselves in sandy or muddy areas and feed on rising tides

Coral Reefs

Physical Environment: formed largely from calcium carbonate skeletons of corals

• Shallow reef building corals live in clear photic zone of tropical seas

Organisms: Unicellular algae live within tissues of corals in mutualism that provides coral with organic molecules

• Fish and invertebrate density on corals exceptionally high

  • Species diversity rivals tropical forests

Oceanic pelagic zone

Physical environment: The vast realm of open blue water

• surface constantly mixed by wind-driven currents

  • covers 70% of Earth

Organisms: Dominant photosynthetic organisms are bacteria and other phytoplankton

• they accound for half of global productivity

  • Zooplankton eat phytoplankton

    • Free-swimming animals include squid, fish, sea turtles and sea mammals

Marine Benthic zone

Physical environment: The sea floor

• Temp declines and pressure increases with depth

Organisms: Seaweeds live in shallow benthic areas

• At deep sea vents, prokaryotes are food producers

  • Coastal benthic communities include invertebrates and fishes

Why is a species absent from an area?: Does dispersal limit it's distribution?

• Yes - area inaccessible or insufficient tim

• No - Do biotic facters limit it's distribution?

Why is a species absent from an area?: Do biotic factors (other species) limit its distribution?

• Yes - due to predation, parasitism, competition, disease

• No - do abiotic factos limit it's distribution?

Why is a species absent from an area?: Do abiotic factors limit it's distribution?

• Chemical factors - Water, oxygen, salinity, pH, soil nutrients, etc.

• Physical Factors - Temperature, light, soil structure, fire, moisture, etc.

Dispersal

Is the movement of individuals away from centers of high population density or from their area of origin

• this contributes to global distrubution of organisms

Species transplants

This occurs when new species are introduced into a habitat

• Includes organisms that are intentionally or accidentlly relocated from their original location

  • this can disrupt communities or ecosystems to which they have been introduced

Biotic factors affecting the distribution of organisms

1. Interactions with other species

2. Predation

3. Competition

• if balance is unkept will cause a species to rapidly increase while another decreases

Abiotic factors affecting distribution of organisms

1. Temperature

2. Water and oxyfen

3. Salinity

4. Sunlight

5. Rocks and soil

Temperature

Environmental temperature is an important factor in distribution of organisms because of it's effects on biological processes

• Cells may freeze and rupture below 0 degress, while most proteins denature abobe 45 degrees

  • Mammals and birds expend energy to regulate their internal temperature

Water and Oxygen

Water availability in habitats is another important factor

• Desert organisms exhibit adaptations for water conservation

Salinity

Salt concentration affects water balance of organisms through osmosis

• Few terrestrial organisms are adapted to high-salinity habitats

Sunlight

Light intensity and quality affect photosynthesis

• Water absorbs light, thus in aquatic environments most photosynthesis occurs near the surace

  • In deserts, high light levels increase temperature and can stress plants & animals

Rocks & soil

Many chaaracteristics of soil limit distribution of plants which the animals feed on.

• Includes:

  • Physical structure

  • pH

  • Mineral Composition