Earth: A Living planetTo properly care for our planet, we must

understand how the living world operates.We study ecology, or the study of the

interactions of organisms with one another and with their physical surroundings.

The part of the planet in which life exists is called the biosphere.

Where do we find life?The part of the planet in which life exists is

called the biosphere.It includes all the areas of land, air and

water on the planet as well as all the life that populates these areas.

Biosphere extends from about 8 km above the earth’s surface to as far as 8 km below the surface of the ocean.

Living organisms are not evenly distributed throughout the biosphere-why not?

EcosystemsThe biosphere is too large to study so

scientists break it down into small units called ecosystems.

Ecosystems include a given area’s physical features (abiotic factors) and living organisms (biotic features)What are the abiotic and biotic factors in a

pond ecosystem?

Pond ecosystemAbiotic factors

WaterSunlightSoil typeRocksTemperatureHumidityElevationrainfall

Biotic factorsFishesFrogsInsectsSnailsWormsAmoebasWater lilies

CommunityThe organisms living together in an

ecosystemEx- a forest community would include trees,

bird and fungiEcosystems are not self-contained-they don’t

function independently of one another.

Ecological successionEcosystems change with time because

every organism effects environmental conditions around it.ex- Burrowing worms change the texture of soil.Trees shade the area beneath their branches,

making it coolerBecause of this, many ecosystems undergo

ecological succession- a process in which an existing community of organisms is replaced by a different community over periods of time ranging from a few decades to thousands of years.

Sometimes succession occurs in places where no living community existed before.Ex- new volcanic islands

Organisms that colonize such areas are called pioneer species.Lichen are typical pioneer species

Changes in species, physical factors, natural disasters, human intervention are all things that can cause succession.

Succession often leads to a fairly stable collection of organisms called a climax community.

These are often described by the predominent species they containEx- temperate zone beech-maple forest

BiomesA broad area of earth’s surface characterized

by distinctive vegetation and associated animal life; for example. Broad-leaf forest biome, grassland biome, desert biome.

Land BiomesTundra

Northernmost land biomeNearly treeless but with mosses, lichens,

grassesAnimals migrate there during the summer –

caribou, reindeer, wolves, foxes, hordes of mosquitoes

Characteristics permafrost- layer of permanently frozen subsoil;

only a few centimeters thaw before its frozen again; this keeps plants small and stunted.

Taiga (Boreal Forest)From Russian word meaning primeval forestMuch of N. America/Asia- coast of N.

California, Washington, Oregon –home of giant redwoods (tallest trees in the world – 60 meters)

Cold summers that are mild enough and long enough to allow plants and animals to reproduce

Many animals, birds

Temperate Deciduous ForestsEastern US, most of Europe, parts of Japan,

china and AustraliaChanging seasons and leaf fallMany animals- a lot hunted to extinction-deer,

moose, gray foxes beginning to reappearAn abundance of organic matter and nutrients

stored in a layer called humus, making this good farmland

Human activity (clearing) in New England, but much has been recovered

GrasslandsMany interior parts of continentsVast areas covered with grasses and small leafy plantsSignificant rainfall that falls during one seasonPlains and prairies of N. America, steppes of Soviet

Union, veld of S. Africa and pampas of ArgentinaMidwest US- hot summers, cold wintersTropical grasslands- little seasonal temperature

change-seasons change from wet to very dry- called savannas

Animal grazing keeps succession downOverfarming causes wind erosion

Tropical Rain ForestWarm temperatures (25 C) and year round

rainfall (200-400 cm)Large areas of S. America, SE Asia, Africa,

Central AmericaHome to more species of plants and animals than

the rest of the land combined70 meter tree canopy; lianas (wrapping vines)Animal life rich and varied. Many are tree

dwellers-forest floor holds dangerChemicals found for diseases; destruction may be

imminent

DesertsLess than 25 cm of rainfall a yearSahara- Africa- largest desert- desolate, virtually

no plant life Can be seasonal deserts- some rainfall- home to

rapidly growing plants with extensive surface roots-SW US and Mexico

Mountainous deserts- higher altitude-called cold deserts- brief rainy season- some grasses and shrubs

Irrigation can make suitable for farming- often very fertile soil- working on it

Aquatic BiomesFreshwater biomes

Rivers, streams, lakesProvide much of our drinking waterImportant source of foodLarge rivers (Nile-Africa, Amazon-S. America)

home to many species of insects, fish, amphibians,reptiles and mammals

Human dumping grounds for waste

Marine BiomesVast habitats or the oceanPhotic zone- the short distance that can be

penetrated by sunlight- where photosynthesis takes place in plantsMay be as shallow as 30 m in N. Atlantic or as

deep as 200 m in S. Pacific OceanLayer where phytoplankton (tiny free-floating

photosynthetic organisms) and algae growOceanographers have divided the ocean into

ecologically distinct zones depending on depth and distance from shore.

Intertidal ZoneMost difficult for organisms to live inPart of the day underwater; part of the day

exposed to air and sunlight; pounding surf; surging waves

Some organisms burrow (clams);some attach themselves to rocks (barnacles, seaweed) still others cling by their feet or suckers (snails, sea urchins, starfish)

Neritic ZoneThe part of a marine biome that extends from

the low-tide line to the edge of the open ocean

Larger algae (seaweed) are abundant because its in the photic zone

Huge numbers of marine life reside here/hunt here

Fish, invertebrates, turtles, lobsters, crabs, flounder, rays

Open-sea zonePhytoplankton responsible for 80-90% of

earth’s photosynthesisFood chains are at workFish, mammals, sea birds reside hereMore phytoplankton closer to shore (more

nutrients), hence more fish closer to shoreUnfortunately makes them more susceptible

to human pollution and over-fishing

Deep-Sea ZonesArea of high pressure, cold temperatures and

total darknessUntil recently thought to be devoid of lifeHome to some of the strangest creatures-

gulper eels with mouths that make up ½ of their body; giant squid with glowing side spots; huge sea cucumbers lumber on the bottom

Zooplankton (free-floating microscopic animals) hide out here during the day and come to the top at night

EstuariesFound at the boundary between fresh water

and sea waterSalt marshes, mangrove swamps, lagoons,

and river deltasRelatively shallow, high photosynthetic areasSheltered area for fish laying and bird

nesting

Energy and Nutrients: Building the Web of LifeOne of the most important factors in an

ecosystem is the flow of energy.Only 0.1% of the sun’s energy that reaches

the surface is used by living things1/2 of the energy absorbed by plants is used

immediately- the rest is stored in plant tissue in compounds called carbohydrates

Animals that eat plants obtain this energy.They use much of it and store very little in

tissues.Energy cannot be recycled or used again so

they don’t call it an energy cycle but rather an energy flow.

Energy Flow- 1st stepSunlight (solar energy)

trapped by plants (and some bacteria) and changed into carbohydrates through photosynthesis.

Producers – photosynthetic organisms capable of making their own food.

Energy Flow – 2nd stepAnimals are consumers.They get their energy

either directly or indirectly from producers

Directly – eat plants- primary consumers- herbivores

Indirectly- eat animals that eat plants – secondary, tertiary or quaternary consumers-carnivores

Energy flow- 3rd stepWhen producers and

consumers die, their remains do not build up because of decomposers

Decomposers obtain their energy from non-living organic matter

They break down dead material

Include fungi and bacteria

Summary – energy flowEach step is called a trophic levelAt each trophic level, energy is used and less

is available to the next levelAs a rule, only about 10% of the energy at

one level is stored to be used by the organisms at the next level.

Scientist use an ecological pyramid to represent the energy relationships among trophic levels.

Biogeochemical CyclesAlthough energy moves in a one-way

direction through an ecosystem, nutrients are recycled.

They are called biogeochemical cycles because nutrients, unlike energy may be used over and over again by living systems.

Water cycleThe movement of

water from the atmosphere to the earth and back to the atmosphere

Nitrogen cycleAll organisms require

nitrogen to build proteins

Although 78% of the air is nitrogen gas, most organisms can’t use it in this form.

The nitrogen cycle shows the movement of nitrogen through the biosphere

Carbon and Oxygen cycles

Nutrient limitationsThe rate at which producers can capture

energy and use it to produce living tissue is controlled by several factors, one of which is the amount of available nutrients.

If the nutrients are in short supply, it is called a limiting factor

Ex- adding large amounts of nitrogen to coastal water causes tremendous growth, or an algal bloom.

Adding a bit of fertilizer doesn’t usually harm an ecosystem, but adding too much can cause harm.

Feeding relationshipsSimplest – food chainUsually more complex-

food web

Can find more info in Ch. 17 & 18.End of material for second test

PopulationsA group of organisms that all belong to the

same species and that live in a given area

Exponential GrowthAlmost any organism provided with ideal conditions

for growth and reproduction will experience a rapid increase in its population

The larger the population gets, the faster it expandsIt produces a growth curve called an exponential

growth curveLeft unchecked, one bacteria could exponentially

reproduce to cover the planet three miles thick in 72 hours.

One pair of elephants could produce in 19 million offspring in 750 years!

Logistic Growth: closer to realityMost populations go through a number of

growth phases which can be represented on a logistic growth curve.

A

B

C

DE

A- at first their numbers increase slowly

B- the population soon grows rapidly (exponentially)

C- speed of the growth begins to slow down- the population grows but not at as quick a rate

D- from here on it grows more and more slowly until

E- population growth becomes steady-the steady state- the birth rate is roughly equal to the death rate- population is maintained

Steady state line represents the carrying capacity of a particular environment for a particular species- certain factors keep the population from growing further.

Factors that control population growthDensity-dependent limiting factors- usually

operate only when populations are large and crowdedCompetitionPredationParasitismCrowding and Stress

Competition- plants and animals compete for food, water, space, sunlight and other essential of life

Competition between members of different yet similar species is a major force behind evolutionary change

No two species occupy the same niche in the same place at the same time

When two species compete, both find themselves under pressure from natural selection to change in ways that decrease their competition.

This is important because it ties ecology to evolutionIt is an example of how all biological sciences are

interrelated when you look at them from an evolutionary point of view

PredationPredator prey relationships exist for just about

every speciesAs prey numbers increase, its easier to get.

More get eaten and their numbers decrease.As predator numbers increase, the food source

gets used up and their numbers decrease.Important to maintain both groups

Ex . wolves, bobcats and deer Rabbits in Australia