Unit 1: The Living World - Ecosystems

Ecology

The study of relationships between organisms and their environment

Levels of Organization

(smallest to largest) species —> population —> community —> ecosystem —> biome —> biosphere (Earth)

ecosystem

A geographic area with interacting biotic and abiotic relationships

abiotic

non-living; eg. water, air, rocks

biotic

living things; eg. animals, plants, bacteria, fungi

predator

an organism that feeds on other organisms

apex predator

a predator at the top of the food chain without natural predators; Regina George

prey

an organism that is captured and is a food source for another animal

symbiosis

the relationship between two species in an ecosystem

mutualism

both organisms benefit

commensalism

one organism benefits & the other is neither harmed/helped

parasitism

one organism is benefited & the other organism is harmed

competition

the struggle of individuals to obtain a shared limiting resource

INTRAspecific

members of the same species competing for resources

INTERspecific

members of different species competing

competitive exclusion principle

Two species competing for the same limiting resource cannot exist

resource partitioning

Two or more species divide a resource based on differences in behavior and morphology

biomes

Large regions of the earth that are characterized by distinct biotic and abiotic characteristics.

two types of biomes

terrestrial & aquatic

climate

the average weather and precipitation over a long period of time

Desert

Temperature range (°C):

•18 to 31 (~68 to ~88℉)

Precipitation Range (cm):

•0 to 100 (0 to ~40 in)

Important Facts:

•NPP (net primary production)  limited by precipitation

•Low NPP = high sensitivity to disturbance

•Rain brings brief but rapid plant growth

Example: Sahara (Africa), Mojave (Cal, Nev), Chihuahuan (New Mexico)

Major Plant Types:

•Cacti and succulents

Example Animal Species:

•Camel, Kangaroo Rat, Gila Monster, Scorpion

Chaparral

Temperature range (°):

•-5 to 20 (23 to 68 ℉)

Precipitation Range (cm):

•25 to 125 (~20 to ~49 in)

Important Facts:

•NPP limited by summer high temperatures and low precipitation

•Species evolved around regular wildfire cycles

Major Plant Types:

•Drought resistant shrubs (Sages, Yucca, etc)

Example Animal Species:

•Mule Deer, Roadrunner, Coyote, Jack Rabbit

Example Location:

•Mediterranean coast, Southern California

Savanna

Temperature range (°C):

•20 to 30 (68 to 86 ℉)

Precipitation Range (cm):

•50 to 275 (~20 to ~108 in)

Important Facts:

•Distinct wet and dry seasons

•High decomposition rate = fertile soil = agriculture

•NPP limited by precipitation

•Grazing and regular wildfire keeps large, woody plants at bay

Example Location:

•Serengeti (Africa)

Major Plant Types:

•Broad-leaf Grasses

Example Animal Species:

Zebra, Lion, Elephant, Rhino

Temperate Grassland

Temperature range (°C):

•-5 to 20 (23 to 68 ℉)

Precipitation Range (cm):

•0 to 50 (0 to ~20 in)

Important Facts:

•NPP limited by temperature and precipitation

•Species evolved around regular wildfire cycles

•Why there are so few trees

Major Plant Types:

•Grasses

Example Animal Species:

•Bison, Pronghorn, Prairie Dog, Black-footed Ferret, Sage Grouse 

Example Location:

•Oklahoma, Kansas, Nebraska, eastern Colorado

Temperate Deciduous Forest

Temperature Range (°C)

Avg Temps: -30 C ---30 C (-22-86 F)

Avg. Precip (cm) 75-150, 30-60 in

Important Facts:

•Warmer temps = rapid decomposition = high soil nutrient levels

•High NPP

•Prime target for agricultural development

Major Plant Types:

•Broadleaf deciduous trees (i.e. Oak, Maple, Hickory, etc.)

Example Animal Species:

•Squirrel, Chipmunk, Bobcat, White-tailed Deer

Example Locations

Eastern U.S./Europe

**We live in this biome**

Temperate Rainforest

Temperature range (°C):

•5 to 20 (41 to 68 ℉)

Precipitation Range (cm):

•150 to 350 (59 to ~138 in)

Important Facts:

•Coastal Biome

•High precipitation + moderate temperatures = high NPP

•BIG TREES!

•Rapid plant growth = low soil nutrient levels

Major Plant Types:

•Conifers (i.e.: Pine, Spruce, etc.)

Example Animal Species:

•Bear, Grouse, Banana slug, spotted owl

Example Location:

•Pacific Northwest, West Coast of Canada, west coast of New Zealand, southern Chile

Tropical Rainforest

Temperature range (°C):

•20 to 30 (68 to 86 ℉)

Precipitation Range (cm):

•250 to 450 (~98 to ~177 in)

Important Facts:

•Very rapid plant growth = very low soil nutrient levels

•Most biodiversity (⅔ terrestrial species)

•Very high NPP

Major Plant Types:

•Broadleaf Evergreens

Example Animal Species:

•Poison Dart Frog, Gorilla, Orangutan, Chimpanzee, Jaguar

Example Location:

•Amazon, The Congo Basin, Sumatra

Boreal Forest / Taiga

Temperature range (°C):

•-5 to 10 (23 to 14 ℉)

Precipitation Range (cm):

•25 to 200 (10 to ~79 in)

Important Facts:

•Short Growing Season

•Low precipitation + slow decomposition (from cool temperatures) + shallow soil = low NPP

Example Location:

Between 50° N to 60° N (North America, Europe. High elevation (above 10,000 in NA)

Major Plant Types:

•Conifers (i.e.: Pine, Spruce, Aspen, 

etc.)

Example Animal Species:

•Moose, Wolf, Bear, Beaver

Tundra

Temperature range (°):

•-10 to 5 (14 to 41℉)

Precipitation Range (cm):

•0 to 100 ( 0 to ~40 in)

Important Facts:

•Permafrost (Subsoil is permanently frozen)

•Low precipitation, cool temperatures, shallow soil = low NPP

Major Plant Types:

•Shrubs, lichens, grasses, wildflowers, NO TREES

Example Animal Species:

•Hare, Arctic Fox, Polar Bear, Caribou

Example Location:

•Greenland, Extreme Northern Asia and North America

Alpine tundra: above about 11,500-11,800 in US depending on latitude

Freshwater Aquatic Biomes

streams, livers, lakes, ponds, freshwater wetlands

Marine Aquatic Biomes

salt marsh, mangrove swamps, intertidal zones, coral reefs, open ocean

Nitrogen fixation

Bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃) or ammonium (NH₄⁺)

Nitrification

Ammonia is converted into nitrites (NO₂⁻) and then into nitrates (NO₃⁻) by bacteria, making nitrogen accessible to plants

Denitrification

Bacteria convert nitrates back into nitrogen gas (N₂), releasing it into the atmosphere.

Water Cycle (Hydrologic Cycle)

- Evaporation and transpiration: Water from oceans, lakes, and plants turns into vapor.

- Condensation and precipitation: Water vapor cools, forming clouds, and eventually falls as rain, snow, etc.

- Runoff and infiltration: Water flows back into bodies of water or seeps into the ground, replenishing groundwater.

Phosphorus Cycle

• Weathering: Phosphorus from rocks is released into soil and water through weathering.

• Absorption by plants: Plants take up phosphates (PO₄³⁻) from soil; animals get phosphorus by consuming plants.

• Sedimentation: Phosphorus returns to the environment through waste and decays, eventually settling into sediments

Sedimentation

Phosphorus returns to the environment through waste and decays, eventually settling into sediments

Deposition

SO₂ combines with water to form sulfuric acid, which falls to Earth as acid rain

Photosynthesis

Plants take in carbon dioxide (CO₂) from the atmosphere and convert it into glucose

Equation = 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Respiration

Animals and plants release CO₂ back into the atmosphere

Equation =C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

Primary Production

The rate at which solar energy is converted into organic compounds via photosynthesis over a unit of time

Gross Primary Production

THE TOTAL rate of photosynthesis in a given area

Net primary production

the energy or biomass available to organisms after plants use some for respiration

Productivity

measured in units of energy per unit area per unit time

recall biomass

the total mass of all living matter in a specific area

standing crop

 the amount of biomass present in an ecosystem in a given time

10% rule

In the transfer of energy from one level to another, only about 10% is passed on

Trophic Level

Can be defined as successive levels of organisms consuming one another.

Producer ---> primary consumer---> secondary consumer ---> tertiary consumer

algae---> zooplankton---> fish---> bald eagle

food chain

a sequence of consumption from producers through tertiary consumers

food webs

models of interlocking patterns of food chains that depict the flow of energy and nutrients in two or more food chains