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Earth: A Living planet
 To 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?
Ecosystems
 The 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 ecosystem
 Abiotic factors
 Water
 Sunlight
 Soil type
 Rocks
 Temperature
 Humidity
 Elevation
 rainfall
 Biotic factors
 Fishes
 Frogs
 Insects
 Snails
 Worms
 Amoebas
 Water lilies
Community
 The organisms living together in an ecosystem
 Ex- a forest community would include trees, bird and
fungi
 Ecosystems are not self-contained-they don’t function
independently of one another.
Ecological succession
 Ecosystems 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
cooler
 Because 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 contain
 Ex- temperate zone beech-maple forest
Biomes
 A 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 Biomes
 Tundra
 Northernmost land biome
 Nearly treeless but with mosses, lichens, grasses
 Animals 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 forest
 Much 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 Forests
 Eastern US, most of Europe, parts of Japan, china and
Australia
 Changing seasons and leaf fall
 Many animals- a lot hunted to extinction-deer, moose,
gray foxes beginning to reappear
 An 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
Grasslands
 Many interior parts of continents
 Vast areas covered with grasses and small leafy plants
 Significant rainfall that falls during one season
 Plains and prairies of N. America, steppes of Soviet Union,
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veld of S. Africa and pampas of Argentina
Midwest US- hot summers, cold winters
Tropical grasslands- little seasonal temperature changeseasons change from wet to very dry- called savannas
Animal grazing keeps succession down
Overfarming causes wind erosion
Tropical Rain Forest
 Warm temperatures (25 C) and year round rainfall (200
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400 cm)
Large areas of S. America, SE Asia, Africa, Central America
Home to more species of plants and animals than the rest
of the land combined
70 meter tree canopy; lianas (wrapping vines)
Animal life rich and varied. Many are tree dwellers-forest
floor holds danger
Chemicals found for diseases; destruction may be
imminent
Deserts
 Less than 25 cm of rainfall a year
 Sahara- 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 Biomes
 Freshwater biomes
 Rivers, streams, lakes
 Provide much of our drinking water
 Important source of food
 Large rivers (Nile-Africa, Amazon-S. America) home to
many species of insects, fish, amphibians,reptiles and
mammals
 Human dumping grounds for waste
Marine Biomes
 Vast habitats or the ocean
 Photic zone- the short distance that can be penetrated by
sunlight- where photosynthesis takes place in plants
 May be as shallow as 30 m in N. Atlantic or as deep as
200 m in S. Pacific Ocean
 Layer where phytoplankton (tiny free-floating
photosynthetic organisms) and algae grow
 Oceanographers have divided the ocean into ecologically
distinct zones depending on depth and distance from
shore.
Intertidal Zone
 Most difficult for organisms to live in
 Part 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 Zone
 The 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 zone
 Phytoplankton responsible for 80-90% of earth’s
photosynthesis
 Food chains are at work
 Fish, mammals, sea birds reside here
 More phytoplankton closer to shore (more nutrients),
hence more fish closer to shore
 Unfortunately makes them more susceptible to human
pollution and over-fishing
Deep-Sea Zones
 Area of high pressure, cold temperatures and total
darkness
 Until recently thought to be devoid of life
 Home 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
Estuaries
 Found at the boundary between fresh water and sea
water
 Salt marshes, mangrove swamps, lagoons, and river
deltas
 Relatively shallow, high photosynthetic areas
 Sheltered area for fish laying and bird nesting
Energy and Nutrients: Building the Web of Life
 One 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 things
 1/2 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-
st
1
step
 Sunlight (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 –
nd
2
 Animals 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
step
Energy flow-
rd
3
 When 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
step
Summary – energy flow
 Each step is called a trophic level
 At each trophic level, energy is used and less is
available to the next level
 As 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 Cycles
 Although 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 cycle
 The movement of
water from the
atmosphere to the
earth and back to the
atmosphere
Nitrogen cycle
 All 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 limitations
 The 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 relationships
 Simplest – food chain
 Usually more complex- food
web
Can find more info in Ch. 17 & 18.
 End of material for second test
Populations
 A group of organisms that all belong to the same
species and that live in a given area
Exponential Growth
 Almost any organism provided with ideal conditions for
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growth and reproduction will experience a rapid increase in
its population
The larger the population gets, the faster it expands
It produces a growth curve called an exponential growth
curve
Left 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 reality
 Most populations go through a number of growth
phases which can be represented on a logistic growth
curve.
A- at first their numbers
increase slowly
E
D
C
B
A
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 growth
 Density-dependent limiting factors- usually operate
only when populations are large and crowded
 Competition
 Predation
 Parasitism
 Crowding and Stress
Competition- plants and animals compete for food,
water, space, sunlight and other essential of life
 Competition between members of different yet similar
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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 evolution
It is an example of how all biological sciences are
interrelated when you look at them from an evolutionary
point of view
Predation
 Predator prey relationships exist for just about every
species
 As 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 .
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wolves, bobcats and deer
Rabbits in Australia