Ecosystems communities organisms and their environments
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Ecosystems & Communities: Organisms and their Environments. Ecosystems have living and non-living components. What are ecosystems?. What is an Ecosystem?. A community of biological organisms plus the non-living components with which the organisms interact.

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Ecosystems & Communities:Organisms and their Environments

Ecosystems have living and non-living components

What are ecosystems?

What is an Ecosystem?

  • A community of biological organisms plus the non-living components with which the organisms interact.

  • Living organisms are not self-sufficient. They need energy and raw materials.

What is an Ecosystem?

  • The biotic environment consists of all the living organisms within an area and is often referred to as a community.

  • The abiotic (aka non-living or physical) environment, often referred to as the organisms’ habitat,consists of:

    • the chemical resources of the soil, water, and air, such as carbon, nitrogen, and phosphorus

    • the physical conditions, such as the temperature, salinity (salt level), moisture, humidity, and energy sources

Which scenario below exemplifies an ecosystem?

  • A group of organisms of the same species living in the same place at the same time

  • Different species interacting together at the same place and time

  • Different species interacting with each other at the same time in a desert

  • A smaller species living on a larger species in a mutually beneficial relationship

Take-Home Message

  • An ecosystem is all of the living organisms in a habitat as well as the physical environment.

  • Ecosystems are found not just in obvious places such as ponds, deserts, and tropical rainforests but also in some unexpected places, like the digestive tracts of organisms or the shell of a beetle.

Challenge Question

  • An ecosystem is made of two components: the biotic environment, or community, consisting of the living organisms within an area, and the physical environment, or the habitat in which these organisms live.

  • A habitat consists of its chemical resources of the soil, water, and air as well as its physical conditions.

    • List some of the aspects that make up the physical conditions of a habitat.

Ecosystems have living and non-living components

15.2 A variety of biomes occur around the world, each determined by temperature and rainfall.

A variety of biomes occur around the world, each determined by temperature and rainfall.

  • What is the average temperature?

  • What is the average rainfall (or other precipitation)?

  • Is the temperature relatively constant or does it vary seasonally?

  • Is the rainfall relatively constant or does it vary seasonally?

Tropical Rain Forest

  • forest of tall trees in a region of year-round warmth

  • ~ 125 to 660 cm yearly rainfall

  • temperature ranges from 20 °C - 34 °C

  • average humidity 77 - 88%

  • rainfall > 250 cm/year (may be a brief dry season)

  • almost all rain forests lie near the equator

Tropical Rain Forest

  • < 6% of Earth's land surface

  • > 50% of all the world's plant and animal species live in tropical rain forests

  • produce ~40% of Earth's oxygen

  • ~70% of the plants in the rainforest are trees

  • ~25% of all the medicines we use come from rainforest plants

Tropical Rain Forest

Indicator Species

  • any biological species that defines a trait or characteristic of the environment

    • may delineate an ecoregion 

    • could indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change

  • can be among most sensitive species in a region; sometimes act as early warning to monitoring biologists

Tropical Rain Forest – Indicator Plant Species

Tropical Rain Forest – Indicator Animal Species


Gorilla gorilla

Orangutan (Pongopygmaeus)

Spider Monkey


Tropical Rain Forest – Indicator Animal Species

2-toed sloth


Three-toed Sloth (Bradypusvariegatus) with baby - Costa Rica

Tropical Rain Forest – Indicator Animal Species

Collared Aracari


Grasslands (Prairie)

  • 2 different types

    • tall-grass: humid & very wet

    • short-grass: dry; hotter summers and colder winters than the tall-grass prairie

  • found in middle latitudes in the interiors of continents

  • either moist continental climates or dry subtropical climates

  • Argentina - grasslands are known as pampas

  • grasslands in southern hemisphere tend to get more precipitation than those in the northern hemisphere

Grasslands (Prairie)

Grasslands (Prairie)

  • temperatures range from -40° F  70° F

  • growing season and a dormant season

    • growing season is when there is no frost and plants can grow (which lasts from 100 to 175 days)

      • tropical and subtropical grasslands the length of the growing season is determined by how long the rainy season lasts

      • temperate grasslands the length of the growing season is determined by temperature (≥ 50° F)

    • dormant (not growing) season: nothing can grow because its too cold

Grasslands (Prairie)

  • average rainfall per year ranges from 10 - 30 inches

    • tropical and sub-tropical grasslands: average rainfall per year ranges from 25 - 60 inches

  • amount of rainfall is very important in determining which areas are grasslands

    • hard for trees to compete with grasses in places where the uppers layers of soil are moist during part of the year but where deeper layer of soil are always dry.

Grasslands (Prairie)

Grasslands– Indicator Plant Species

Old Field Habitat, Ohio

Ironweed (Vernoniasp.)with Hedge Bindweed Vine  (Calystegiasepium)

Grassland, North Dakota

Grasslands– Indicator Plant Species

Ironweed (Vernoniasp.)

Joe Pye Weed

Eupatorium purpureum

Grasslands – Indicator Plant Species

Common Teasel


Queen Anne's Lace (Daucuscarota)

Grasslands – Indicator Animal Species

Bison (Bison bison) on the range, Theodore Roosevelt National Park, North Dakota

Grasslands – Indicator Animal Species

Przewalski's horse (Equuscaballusprzewalskii), The Wilds, Ohio

Grasslands – Indicator Animal Species


  • Russian word for forest

  • largest biome in the world

  • Eurasia, North America

  • located just below the tundra biome

  • many coniferous trees

  • aka boreal forest; Boreal was the Greek goddess of the North Wind


  • winter temperature range is -54 to -1° C (-65 to 30° F)

  • summer: -7° C (20° F) to 21° C (70° F)

  • summers are very short (50 - 100 frost free days)

  • average yearly precipitation: 30 - 85 cm (12 - 33 in)

  • main seasons are winter and summer

    • spring and autumn are very short

    • weather is either hot and humid or very cold


Taiga – Indicator Plant Species

Balsam Fir


Black Spruce


Taiga – Indicator Plant Species

White Poplar

Populus alba

Paper Birch


Jack Pine


Taiga – Indicator Animal Species

American Black Bear


Bald Eagle


Taiga – Indicator Animal Species

Snowshoe Rabbit


Long-eared Owl



  • cover about one fifth of Earth's land surface

    • hot and dry: near Tropic of Cancer/Tropic of Capricorn

    • cold: near the Arctic

  • temperature

    • hot & dry: ~ 25° C to ~ 49° C

    • cold: -2 to 4° C (winter) 21 to 26° C (summer)

  • precipitation

    • hot & dry: very little rainfall and/or concentrated rainfall in short periods between long rainless periods (< 15 cm/year)

    • cold: 15 - 26 cm/year


Desert – Indicator Plant Species

Desert – Indicator Plant Species

Fishhook Cactus


Saguaro Cactus


Desert – Indicator Plant Species


Desert – Indicator Animal Species

Zebratail Lizard - Callisaurusdraconides

Desert – Indicator Animal Species

Rock hyrax (Procaviacapensis)

Desert – Indicator Animal Species

Bactrian Camel, Camelusbactrianus

Temperate Deciduous Forest

  • temperature: 0 - 20 C

  • precipitation: ~ 50 – 200 cm/year

Temperate Deciduous Forest

Temperate Deciduous ForestIndicator Plant Species

Oaks (Quercus sp.)



Temperate Deciduous ForestIndicator Plant Species




Sassafras albidum

Temperate Deciduous Forest – Succession

  • orderly succession of communities to a climax community (biome)

  • two main types of succession:

    • primary succession: begins with bare rock exposed by geologic activity

    • secondary succession: begins on soil from which previous community has been removed (by fire, agriculture, etc.)

      • secondary succession can proceed much faster because the soil has been prepared by the previous community

Temperate Deciduous ForestIndicator Animal Species

Box Turtle

American Toad


Temperate Deciduous ForestIndicator Animal Species

Eastern Gray Squirrel


Eastern Chipmunk


Temperate Deciduous ForestIndicator Animal Species

Yellow-breasted chat



  • annual average temperature < 5 C

  • precipitation (mostly in the form of snow) < 100 mm/year

  • summer is brief

    • temperatures above freezing last only a few weeks at most

    • "warm" summer coincides with periods of almost 24 hour daylight, so plant growth can be explosive 


Anaktuvuk Pass, Alaska

Tundra – Indicator Plant Species

Arctic Tundra Wildflowers - Alaska

Tundra – Indicator Plant Species

Polytrichum Moss

(photographed in Ohio, not on the Tundra)


Tundra – Indicator Animal Species



Tundra – Indicator Animal Species

 Caribou On Autumn Tundra Denali National Park Alaska


  • rolling grassland scattered with shrubs and isolated trees

    • found between a tropical rainforest and desert biome

    • not enough rain falls on a savanna to support forests

    • found in a wide band on either side of the equator on the edges of tropical rainforests

  • warm temperature year round

  • very long dry season (winter): ~ 10 cm rain; none at all from Dec - Feb

  • very wet season (summer): ~ 35-65 cm rain


Savanna – Indicator Plant Species


UmbrellaThorn AcaciaAcacia tortillis

Savanna – Indicator Animal Species

Savanna ElephantLoxodontaafricana

Black MambaDendroaspispolylepis

LionPanthera leo


  • winter: mild and moist, but not rainy

  • summer: very hot and dry.

  • annual temperature range: between -1° and 38° C

  • annual precipitation: ~ 25-45 cm, mostly in the winter


Chaparral – Indicator Plant Species

Olive TreeOleaeuropaea

Blue OakQuercusdouglasii

Common SagebrushArtemisia tridentata

Chaparral – Indicator Animal Species

Black-tailed JackrabbitLepuscalifornicus

Golden JackalCanis aureus

 Spotted SkunkSpilogalegracilis

The Freshwater Biome

  • low salt concentration — usually less than 1%

  • plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e., ocean)

  • 3 different types of freshwater regions:

    • ponds and lakes

    • streams and rivers

    • wetlands

The Freshwater Biome – Ponds and Lakes

From left: a view across Manzanita Lake toward Mt. Lassen, California; a forest pond near Donnelly, Idaho; a Great Blue Heron; Paranagat Lake, southeastern Nevada.

The Freshwater Biome – Streams and Rivers

From left: McArthur-Burney Falls State Park, California; trout; Green River, Utah; Brooks River, Alaska.

The Freshwater Biome - Wetlands

From left: Pescadero Marsh, California; coastal marsh at Umpqua Dunes, Oregon; trees and bogs on Esther Island, Alaska.

The Marine Biome

  • cover about three-fourths of the Earth's surface

  • marine algae supply much of the world's oxygen supply and take in a huge amount of atmospheric carbon dioxide

  • evaporation of the seawater provides rainwater for the land

  • 3 different types of marine regions:

    • oceans

    • coral reefs

    • estuaries

The Marine Biome - Oceans

From left: mussels, worms, and a spider crab at a hydrocarbon seep community in the Gulf of Mexico; a sea fan and brain coral in the Florida Keys National Marine Sanctuary; a school of Atlantic amberjack off North Carolina.

The Marine Biome – Coral Reefs

From left: reef life in the Gulf of Aqaba, Red Sea; a reef at Fanning Island atoll in the central Pacific; a reef in the Florida Keys National Marine Sanctuary.

The Marine Biome - Estuaries

From left: Mangrove roots, south Florida; wetlands and tidal streams in the Ashe Island area, ACE Basin National Estuarine Research Reserve, South Carolina; a salt marsh in Winyah Bay National Estuarine Research Reserve, South Carolina.

Ecological Notes

These are the biomes, in order of their productivity (highest first)

  • estuaries and tropical rain forest  (highest)

  • temperate forest

  • agricultural land

  • temperate grassland

  • lakes and streams

  • coastal zone

  • tundra

  • open ocean

  • desert   (lowest)

Ecological Notes

In order to be productive and have a lot of living material standing around (biomass), an ecosystem has to have 4 basic necessities for plant life to thrive (if there are enough plants, the ecosystem will also support a lot of animals).  The four things are:

  • Sunlight

  • Nutrients

  • Warm temperatures

  • Water

Biomes Video

Take-Home Message

  • Biomes are the major ecological communities of earth, characterized mostly by the vegetation present.

  • Different biomes result from differences in temperature and precipitation, and the extent to which they vary from season to season.

Challenge Question

  • Terrestrial biomes are determined by the temperature and precipitation amounts as well as whether those factors are constant or vary by season.

  • By contrast, how are aquatic biomes determined?

Energy and chemicals flow within ecosystems

Energy flows from producers to consumers.

First Stop: Primary Producers

First Stop: Primary Producers

  • ecosystem: producers or consumers

    • primary producers: plants, algae (some), bacteria

      • convert light energy from sun into chemical energy through photosynthesis

      • chemical energy = food

    • consumers eat or absorb their food

      • energy stored in chemical bonds of carbohydrate, protein, and lipid molecules is captured and harnessed for consumers’ own movement, reproduction, and growth

Second Stop: Primary Consumers – the Herbivores

Third Stop: Secondary Consumers – the Carnivores

Fourth Stop: Tertiary Consumers – the “Top” Carnivores

Food Chain

Food Web

Food Web

Food Chains & Food Webs

  • A change in one link in a food chain will affect the other links.

  • The table on the next slide gives one example of a food chain and the trophic levels represented in it:

Food Chains & Food Webs

Chain Reaction Game

Energy Flows through a Food Web

Losses at every “step” in a food chain

Inefficiency of energy transfers

A grasshopper eats a plant. A mouse eats the grasshopper. A snake eats the mouse. A hawk could eat the snake or the mouse. In this food web, how would we categorize the hawk?

  • Producer

  • Primary consumer

  • Secondary consumer

  • Tertiary consumer

  • Quaternary consumer

  • 4 and 5

Take-home message

Energy from the sun passes through an ecosystem in several steps.

First, it is converted to chemical energy in photosynthesis.

Herbivores then consume the primary producers, the herbivores are consumed by carnivores, and the carnivores, in turn, may be consumed by top carnivores.

Take-home message

Detritivores and decomposers extract energy from organic waste and the remains of organisms that have died.

At each step in a food chain, some usable energy is lost as heat.

Energy and chemicals flow within ecosystems

Energy pyramids reveal the inefficiency of food chains.


  • biomass: total weight of all living organisms in a given area

  • only about 10% of the plants in an ecosystem is converted into biomass

  • Food Energy Pyramid

    • flow of energy through a food chain

    • trophic level: position that an organism occupies in a food chain - what it eats, and what eats it

  • African savannas and grasslands sustain more species of higher-order carnivores than any other terrestrial ecosystem

Food Energy Pyramids

flow of energy through a food chain

trophic level: position that an organism occupies in a food chain - what it eats, and what eats it

You go out to eat at a fancy restaurant. You have a salad, salmon, and for dessert ice cream! Which part of the meal was the most energy efficient food for you to eat?

  • Salad

  • Salmon

  • Ice cream

  • 2 and 3

Take-home message

Energy from the sun passes through an ecosystem in several steps known as trophic levels.

Energy pyramids reveal that the biomass of primary producers in an ecosystem tends to be far greater than the biomass of herbivores.

The biomass transferred at each step along the food chain tends to be only about 10% of the biomass of the organisms being consumed, due to energy lost in cellular respiration.

As a consequence of this inefficiency, food chains rarely exceed four levels.

Energy and chemicals flow within ecosystems

Essential chemicals cycle through ecosystems.

Chemical Reservoirs

Each chemical is stored in a non-living part of the environment.

Organisms acquire the chemical from the reservoir, a non-living part of the environment.

The chemical cycles through the food chain (biogeochemical cycles).

Eventually, the chemical is returned to the reservoir.

The Most Important Chemical Cycles





Carbon Cycle Game

Fossil Fuels

  • created when large numbers of organisms die and are buried in sediment lacking oxygen

  • In absence of oxygen, at high pressures, and after very long periods of time, organic remains are ultimately transformed into coal, oil, and natural gas

  • burning coal, oil, and natural gas releases large amounts of carbon dioxide

    • increases average CO2 concentration in the atmosphere

    • current level of CO2 in the atmosphere is the highest it has been in almost half a million years

Global CO2 levels are rising in general, but they also exhibit a sharp rise and fall within each year – why?


Because it is necessary for the production of every plant protein, and because all nitrogen must first be made usable by bacteria, plant growth is often limited by nitrogen levels in the soil.

For this reason, most fertilizers contain nitrogen in a form usable by plants.

Sulfur Cycle

component of protein 

cycles in both a gas and sedimentary cycle

source : earth's crust

enters the atmosphere as  hydrogen sulfide (H2S) during fossil fuel combustion, volcanic eruptions, gas exchange at ocean surfaces, decomposition

Sulfur Cycle

H2S is immediately oxidized to sulfur dioxide (SO2) 

SO2 + water vapor  H2SO4 (falls to earth in rain)  

sulfur in soluble form is taken up by plant roots, incorporated into amino acids such as cysteine

travels through food chain

eventually released through decomposition

How is carbon recycled back to the atmosphere in the carbon cycle?

It is “fixed” by bacteria.

It is a product of cellular respiration.

Burning of fossil fuels.

2 and 3.

All of the above.

Why do commercial fertilizers usually contain usable forms of nitrogen and phosphorous?

These chemicals are not efficiently recycled in the soil.

Nitrogen and phosphorous need to be “fixed” by bacteria or the plant.

Nitrogen and phosphorous are found at high levels in the atmosphere but not in the soil.

Nitrogen and phosphorous only enter the soil through erosion.

Take-home message

Chemicals essential to life—including carbon, nitrogen, and phosphorus—cycle through ecosystems.

They are usually captured from the atmosphere, soil, or water by growing organisms; passed from one trophic level to the next as organisms eat other organisms; and returned to the environment through respiration, decomposition, and erosion.

These cycles can be disrupted as human activities significantly increase the amounts of the chemicals utilized or released to the environment.

Symbiotic Relationships

Symbiosis: close relationship between organisms of two different species

At least one participant gains some sort of benefit (usually nutritional)

Types of symbiosis:






Parasite derives nutrition from the host

This harms the host but a true parasite does not usually kill its host (directly)


Remain outside the host

Ticks, fleas, leeches


Live inside the host’s body

Tapeworms, malarial parasites

Parasite Transmission

Many parasites live on or in a single organism

Some will alternate between 2 or more host species

Vertical transmission – from mother  offspring

Horizontal transmission – between members of a population

Direct contact (head lice)

Vectors (mosquitos)


Neither species is totally dependent on the other

One benefits – no effect on the other

Feeding or protection

Porcelain anemone crabs and anemones


Both species benefit

Food or shelter


Plants and microbes (rhizobium in root nodules)

Plants and fungi (orchids and mycorrhizae)

Protists and fungi (lichen)

Plants and insects (pollination)

Animals and bacteria (ruminants)

Animals and other animals (crocodiles and plover birds)


Rhizobium in root nodules of certain plants convert nitrogen in soil to usable form.


Fungi aid the plant in the uptake of nutrients.

Fungi ingest some of the food from plant photosynthesis


Most of the lichen is composed of fungal filaments, but living among the filaments are algal cells, usually from a green alga or a cyanobacterium.

The lichen fungus provides its partner(s) a benefit (protection) and gains nutrients in return.


Ruminants are characterized by their four-chambered stomach and "cud-chewing" behavior. Cud is a food bolus that is regurgitated, rechewed, and reswallowed. The rumen is a large fermentation vat containing billions of microorganisms, including bacteria and protozoa, which allow ruminants to digest fibrous feeds such as grass and hay that other animals cannot efficiently utilize.

Crocodiles & Plover Birds

The bird gets into the crocodile's mouth and picks out the tiny bits of food stuck in his teeth, then eats it (the tiny bits).

This cleans the crocodile's teeth and keeps his mouth fresh and free from infections.









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